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bulletin AMERICAN CERAMIC SOCIETY emerging ceramics & glass technology APRIL 2012 Thermoelectrics—High-temperature oxides; modeling; nanoscale synthesis • Raw materials—scarcity and criticality • Meeting highlights—ICC4, GOMD • Thermoelectric materials – Using temperature differences to generate power, refrigerate Sr Ti O Sr 2 TiO 4 Sr 2 Ti 2 O 7

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Page 1: emerging ceramics & glass technologyamericanceramicsociety.org/bulletin/2012_pdf_files/apr_12/pdf/apr...bulletin AMERICAN CERAMIC SOCIETY emerging ceramics & glass technology APRIL

bulletinA M E R I C A N C E R A M I C S O C I E T Y

e m e r g i n g c e r a m i c s & g l a s s t e c h n o l o g y

APRIL 2012

Thermoelectrics—High-temperatureoxides;modeling;nanoscalesynthesis•

Rawmaterials—scarcityandcriticality•

Meetinghighlights—ICC4,GOMD•

Thermoelectric materials – Using temperature differences to generate power, refrigerate

Sr

Ti

O

Sr2TiO4 Sr2Ti2O7

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1American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

contentsA p r i l 2 0 1 2 • V o l . 9 1 N o . 3

cover storyHigh-temperature oxide thermoelectrics Cover photo credit: Layered thermoelectric Sr2TiO4. Credit: Misture and Edwards.

– page 24

feature articles4th International Congress on Ceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Keynote and plenary speakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Invited speakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233rd Ceramic Leadership Summit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

High-temperature oxide thermoelectrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Scott Misture and Doreen Edwards

Conversion of waste heat to electrical energy using oxide thermoelectric generators may revolutionize the efficient use of energy in the future .

High efficiency nanobulk thermoelectrics by bottom-up nanocrystal sculpting and assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Rutvik J. Mehta and Ganpati Ramanath

Bottom-up synthesis using nanostructuring and doping holds promise for realizing nanobulk thermoelectric materials with ZT values greater than 2 .

Modeling thermoelectric materials and devices . . . . . . . . . . . . . . . . . . . . . . . . 34Alan McGaughey

Recent advances in modeling and simulation suggest thermoelectric devices can be competitive with existing refrigeration and power generation technologies .

Issues of scarce materials in the United States . . . . . . . . . . . . . . . . . . . . . . . . . 40Steven W. Freiman and Lynnette D. Madsen

Government and the private sector can take steps to address scarcity of critical materials for manufacturing of ceramic materials .

2012 Glass & Optical Materials Division Annual Meeting . . . . . . . . . . . . . . . 46Program overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Schedule at a glance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Symposia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

MCARE’12 highlights and photos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

departmentsNews & Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3•Federalbudget2013—Whattheproposedbudgetisofferingforscience

R&D•Businessnews•Greenhomesmarketexpectedtoincreasefivefoldby2016,upfroma

$17B opportunity today•A123lookingatnewstrategiesasFiskerAutomotivefalters•TowardMaterialsGenomeInitiative,DOEallocates$12Mforsoftware,

‘glue’funding•TwonewMaterial Marvelsvideos:‘Thermoelectrics’and‘Nanomaterials’•NationalResearchCouncilnames16techprioritiesforNASA•Newceramic–aluminumcompositebrakerotordevelopedformassmarket•MakerBotsofferslow-costdesktop3Dreplicators

Raw materialsScarcity and criticality are key issues – page 40

Research BriefsGround waste glass improves cement – page 13

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2 www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 3

departments, continuedACerS Spotlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10•WelcometoournewestCorporateMembers•TurnmomentumintosuccessatCeramitec•OrderoftheEngineer:Apledgetoprofessionalism

People in the Spotlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11•SectionwillpresentToledoGlassandCeramicAwardtoFaber•SPIEnamesSundaramseniormember•ChineseAcademyelectsWadsworthForeignFellow

Advances in Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12•Makingferroelectricnanorockswithanatomicforcemicroscopehammer•Navyinvest$6Mfor‘bottomup’buildingofcarbon-basednanoelectronics

Research Briefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13•Ground-upwasteglassimprovescementproperties•Modelingsinteringwithoutconstitutiveequations•Silicatelayeriskeytolow-temperaturebondingofsiliconcarbide

Ceramics in Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16•Tailoredpiezoelectricnanostructuresvia‘softtemplateinfiltration’•CatalyticceramicporousmembranekeytoGas2’spilotgas-to-liquidsplant•AltaDevicesreportsNRELverifies23.5percentefficientforsolarpanel•VO2foilseyedformassproductionforthermochromicwindowapplications

Ceramics in Biomedicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21•UABgroupdemonstratestechniquestoelectrospinimproved3Dtissueengi-

neeringscaffolds

columnsDeciphering the Discipline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 RyanGebhardtandJohnSolomon International experiences are an opportunity to compare systems and cultures, help others learn English and “speak the language of international research .”

resourcesCalendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Classified Advertising . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Display Advertising Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

contentsA p r i l 2 0 1 2 • V o l . 9 1 N o . 3bulletin

AMERICAN CERAMIC SOCIETY

Editorial and ProductionPeter Wray, Editor ph:614-794-5853fx:614-794-5813 pwray@ceramics .orgEileen De Guire, Senior Editor ph:614-794-5828fx:614-794-5815 edeguire@ceramics .orgRusell Jordan,ContributingEditorTess M. Speakman, Graphic Designer

Editorial Advisory BoardAllen Apblett, OklahomaStateUniversityKristen Brosnan, General ElectricOlivia Graeve, AlfredUniversityAndrew Gyekenyesi, NASALinda E. Jones, Chair,AlfredUniversityJoe Ryan, PacificNorthwestNationalLab

Customer Service/Circulation ph:866-721-3322fx:240-396-5637 customerservice@ceramics .org

Advertising SalesNational SalesPatricia A. Janeway,AssociatePublisher pjaneway@ceramics .org ph:614-794-5826fx:614-794-5822

EuropeRichard Rozelaar media@alaincharles .com ph:44-(0)-20-7834-7676fx:44-(0)-20-7973-0076

Executive Staff Charles G. Spahr,ExecutiveDirectorandPublisher cspahr@ceramics .orgSue LaBute,HumanResourcesManager&Exec.Assistant slabute@ceramics .orgMegan Bricker,Dir.Marketing&MembershipServices mbricker@ceramics .orgMark Mecklenborg, Dir.TechnicalPublications&Meetings mmecklenborg@ceramics .orgLaura Vermilya,DirectorOperations lvermilya@ceramics .orgPeter Wray, Director Communications pwray@ceramics .org

American Ceramic Society Bulletin covers news and activities of the Society and its members, includes items of interest to the ceramics community and provides the most current information concerning all aspects of ceramic technology, including R&D, manufacturing, engineering and marketing.

American Ceramic Society Bulletin (ISSN No. 0002-7812). ©2012. Printed in the United States of America. ACerS Bulletin is published monthly, except for February, July and November, as a “dual-media” magazine in print and electronic format (www.ceramicbulletin.org).

Editorial and Subscription Offices: 600 North Cleveland Avenue, Suite 210, Westerville, OH 43082-6920. Subscription included with American Ceramic Society membership. Nonmember print subscription rates, including online access: United States and Canada, 1 year $95; international, 1 year $150.* Rates include shipping charges. International Remail Service is standard outside of the United States and Canada. *International nonmembers also may elect to receive an electronic-only, e-mail delivery subscription for $95.

Single issues, January–November: member $6.00 per issue; nonmember $7.50 per issue. December issue (ceramicSOURCE): member $20, nonmember $25. Postage/handling for single issues: United States and Canada, $3 per item; United States and Canada Expedited (UPS 2nd day air), $8 per item; International Standard, $6 per item.

POSTMASTER: Please send address changes to American Ceramic Society Bulletin, 600 North Cleveland Avenue, Suite 210, Westerville, OH 43082-6920.

Periodical postage paid at Westerville, Ohio, and additional mailing offices. Allow six weeks for address changes.

ACSBA7, Vol. 91, No. 3, pp 1–56. All feature articles are covered in Current Contents.

OfficersGeorge Wicks, PresidentRichard Brow, President-electMarina Pascucci, PastPresidentTed Day, TreasurerCharles Spahr, ExecutiveDirector

Board of Directors William G. Fahrenholtz, Director2009-2012David J. Green, Director2010-2013Vijay Jain, Director2011-2014Linda E. Jones, Director2009-2012William Lee, Director2010-2013James C. Marra, Director2009-2012Ivar Reimanis, Director2011-2014Lora Cooper Rothen, Director2011-2014Robert W. Schwartz,Director2010-2013David W. Johnson Jr., Parliamentarian

Address600NorthClevelandAvenue,Suite210 Westerville,OH43082-6920

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3American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

Federal budget 2013 — What the proposed budget is offering for science R&D

President Obama has delivered his FY’13 budget proposal to Congress, and OSTP chief John Holdren has appeared before the House’s Committee on Science, Space and Technology to offer comments about the civilian science and technology

pieces of the proposed budget.The OSTP has posted a summary

of the R&D requests in the budget. In a concurrent press release, the OSTP outlines seven administration goals for “building and fueling America’s engines of discovery”: to expand the frontiers of human knowledge; promote economic growth with a focus on manufactur-ing; cultivate domestic clean energy; improve healthcare outcomes; address

global climate change; manage envi-ronmental resources; and strengthen national security.

The FY13 budget requests $140.8 billion for federally supported R&D, which represents an increase of 1.4 percent ($2.0 billion) over the FY12 enacted level. In testimony, Holdren said the proposed budget is “designed to ensure that America will continue, in the President’s words, to ‘out-innovate,

news & trends

Hindusthan National Glass Industries has announced plans to invest in a new manufacturing facility in Andhra Pradesh, and the Neemrana region of Rajasthan, India (www.hngil.com) … AGC Glass Europe will shutter its two oldest glass furnaces in Europe (Moustier, Belgium, and Salerno, Italy (www.agc-glass.eu) … Corning Inc. lands first big order for photovoltaic glass (www.corning.com) … Saint-Gobain will continue to focus on emerging market development after strong Latin American “organic” sales growth of more than 25 percent via the company’s packaging segment, Verallia (www.verallia.com) … In 2011, Imerys’ end markets held well overall compared with 2010, a year of sharp upturn and inventory rebuilding (www.imerys.com) … Lucifer Furnaces Inc. recently delivered a single chamber bench model box furnace to Power Plant Services, an ISO 9001certified provider of parts and repairs for the power generation and steel mill industries (www.luciferfurnaces.com) … TEAM by Sacmi is organizing TEAM Day 2012 on May 21 at the Ceramitec fair, providing presenta-tions on a range of advanced ceramics topics and related technologies (www.sacmi-team.com) … Heidelberg Cement says despite the impact of a significant rise in energy costs during last year, revenues rose 9.7 pecent year-on-year to €12.9

billion in 2011, while operating income was up 3 percent to €1.5 billion (www.heidelbergcement.com) … Likewise, Saint-Gobain reports it was able to curb the impact of soaring raw-material and energy costs by increasing its sales prices and, as a result, delivered another sharp rise in earnings for the year (www.saint-gobain.fr) … FuelCell Energy announced a joint effort with Fraunhofer IKTS to develop the European market for stationary fuel cell power plants (www.fuelcellenergy.com) … The Tape Casting Warehouse Division of Richard E. Mistler Inc. is offer-ing environmentally friendly plasticizer for tape-casting systems (www.drblade.com/TCW.asp) … Ceramaterials signs Marty Keylon of Keylon Thermal Consulting as West Coast representative (www.ceramaterials.com) … Sauereisen wins 2011 Pittsburgh Business Ethics Award, given by the Society of Financial Services Professionals, the David Berg Center for Ethics and Leadership at the University of Pittsburgh and the Pittsburgh Rotary (www.sauereisen.com) … PacificGlas will commission a new electric furnace and two production lines in June 2013 at its plant located 300 kilometers south of Seoul, Korea. The furnace is expected to have a capacity of 20 tons per day (www.pacificglas.com) … Saint-Gobain is said to be on the verge of handing over to Pilkington its half of Flovetro automotive float plant in San Salvo, Italy (www.saint-

gobain.fr) … World crude steel produc-tion reached 1,527 megatonnes for the year 2011, a record for global crude steel production and an increase of 6.8 percent compared with 2010 (www.worldsteel.org) … Saudi Arabia has renewed its ban on cement exports, after partially lifting it in 2009, because of rising demand at home (www.saudigazette.com.sa) … Thermal Technology recently built and installed a 500,000-pound-force hot press for a Northern California customer to produce large powder metallurgy semiconduc-tor materials (www.thermaltechnology.com/) … Ortech offers ceramic tubing for industrial machinery and chemical manufacturing (www.ortechceramics.com) … PPG sponsored the 2012 Progressive Architecture Awards Feb. 16 at Museum of Modern Art in New York to recognize build-ings and architectural design throughout the world that stretches the boundaries of convention and promotes advances in the field (www.ppg.com) … Morgan Thermal Ceramics offers next-generation flexible MIN-K aerospace insulation that features 20 to 25 percent lower thermal conductivity than the industry (www.morganthermalce-ramics.com) … Eliane S/A and Portobello S/A, Brazilian producers of ceramic tile, have entered into an agreement to merge, resulting in a firm with more than 4,000 employees and $650 million in sales and one of the top five worldwide producers (www.portobello.com.br). n

Business news

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news & trends

out-educate and out-build the rest of the world’.”

Three agencies have been identi-fied as critical to fulfilling the nation’s mission to maintain and advance its economic position: the NSF, DOE and NIST. (Holdren describes them as “jewel-in-the-crown” agencies). Holdren’s testimony noted that the administration has been working to continue efforts begun under the Bush administration (as part of the America COMPETES Act) to gradually double the budgets of these three agencies. The Budget Control Act of 2011 will slow, but not halt, that priority.

Culling through the R&D summary posted on OSTP’s website provides a glimpse of how things may shake out for the materials science community based on the proposed R&D budgets for agencies that fund the largest chunks of materials science research:

• National Science Foundation— $7.4 billion, an increase of 4.8 percent over 2012 enacted levels.

• Department of Defense—$71.2 billion for R&D, a $1.5 billion decrease from 2012. The funding request includes $11.9 billion for early-stage science and technology programs, $2.8 billion for DARPA and maintains basic research at $2.1 billion.

• NASA—$9.6 billion for R&D on an overall budget on $17.7 billion,

a 2.2 percent ($203 million) bump for R&D, but probably not enough to bring NASA technology up to levels recently recommended by the National Research Council.

• DOE—$11.9 billion, an 8.0 per-cent ($884 million) increase in R&D over 2012 enacted levels. ARPA-E is written in for $350 million, and the DOE budget targets $290 million specifically “to expand activities on innovative manufacturing processes and advanced materials.”

• NIST—$708 million for NIST’s intramural labs, 13.8 percent over 2012 enacted levels, reflecting the admin-istration’s efforts to double its budget. The agency is home to the Hollings Manufacturing Extension Partnership ($128 million request) and the new Advanced Manufacturing Technology Consortia program ($21 million request).

• Department of Homeland Security—$729 million, up 26.3 per-cent over enacted 2012. The huge increase is to restore cuts imposed in 2012. DHS efforts touch the materials community through R&D on nuclear materials, explosives detection and chemical/biological response systems.

• Department of Education—$398 million. This R&D funding addresses the president’s goal of training 100,000 STEM teachers in the next decade and developing educational strategies.

The R&D budget includes bud-gets for three multiagency initia-tives, including the National Nanotechnology Initiative. The NNI member agencies “focus on R&D of materials, devices and systems that exploit the unique … properties that emerge in materials at the nanoscale.” The requested budget is for $1.8 billion, an increase of $70 million over the 2012 enacted budget.

Finally, the contentious issue of hydraulic fracturing (“fracking”) is get-ting some attention in the budget with collaborative funding streams through DOE, EPA and the Department of the Interior to “understand and minimize the potential environmental, health and safety impacts of natural-gas and oil production.” That’s a broad-ranging mission statement, but materials sci-ence has a role to play, for example, with engineered proppants.

For play-by-play commentary, visit the AAAS website, “R&D Budget and Policy Program.” AAAS does a good job tracking developments and slicing out the parts that are relevant to the science and technology communities. Since 1976, AAAS has issued a com-prehensive analysis of the federal R&D budget. Last year it was available in May, so look for a similar report about FY13 in a few months. The OSTP web-site, of course, stays abreast of budget developments. Visit: www.aaas.org; www.whitehouse.gov. n

Green homes market expected to increase fivefold by 2016, up from a $17B opportunity today

McGraw-Hill Construction, a part of the McGraw-Hill Companies, released findings from a new Green Home Builders and Remodelers Study at the recent National Association of Home Builders International Builders’ Show in Orlando, Fla.

Green homes comprised 17 percent of the overall residential construction market in 2011 and are expected to

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Trends in federal research and development budgets.

(billions of constant FY2012 dollars)

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5American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

grow to between 29 percent and 38 per-cent of the market by 2016. By value, this equates to a fivefold increase, grow-ing from $17 billion in 2011 to $87–$114 billion in 2016, based on the five-year forecast for overall residential con-struction. Green remodeling is growing especially fast because of the economy and decline in new home construction. Visit: www.construction.com n

A123 looking at new strategies as Fisker Automotive falters

A123 Systems is in something of a scramble mode thanks to the problems with Fisker Automotive’s DOE loan guarantee.

The story first came to light on Feb. 9 when, according to a Forbes report, Wunderlich Securities analyst Theodore O’Neill reduced his rating of A123 stock in reaction to a DOE loan guarantee to Fisker being put in hiatus.

Fisker is a California-based start-up company that makes luxury hybrid cars and was started in 2007 by Henrik Fisker and Bernhard Koehler. In 2009 it received a $528 million loan guar-antee from the DOE, of which it has received $193 million so far, according to an online Reuters article, to sup-port development of its first model, a luxury vehicle dubbed Karma. Also in the works is a sedan called Nina. In an email to the Bulletin, Fisker spokesman Russell Datz explains that the company actually received two loans totaling $528.7 million: one for $169 million to support the Karma program, and the remainder to support Project Nina. He says the company has drawn all the loan for the Karma and about $24 mil-lion for Project Nina.

The company built about 1,500 Karmas and delivered 400–500, includ-ing its first car, which went in July 2012 to investor and ecocelebrity Leonardo DiCaprio. Prospective customers must indeed have lots of (monetary) karma to purchase a Karma — they sell for upward of $100,000.

Although some press reports claim

DOE suspended the loan guarantee, according to Fisker, the delay in DOE funding was initi-ated by the company, itself. Datz says, “In May 2011, Fisker Automotive opted to stop taking reim-bursements from the DOE while the com-pany entered negotia-tions to implement more realistic and achievable milestones.”

Fisker recently laid off 25 workers in its Delaware plant. The company says they had been refurbishing the plant in preparation for Project Nina. The Karma is assembled in Finland and Fisker says the layoff is not directly related to its production or the com-pany’s need for batteries.

Nevertheless, analyst O’Neill sus-pects that the interruption of DOE funding is likely to result in reduced Karma production. In his research note, quoted in the Forbes article, he says lower Karma production “throws 2013 estimates [for A123] into disar-ray because Fisker has started laying off employees at its plant in Delaware and this would have been a much larger opportunity for A123 Systems.” O’Neill estimates that Fisker has about 2,000 battery packs in its inventory and implied that might be enough, “We can’t be sure when it [Fisker] will need more or if it will have the money to pay for it. In either case, we have to lower our revenue forecast [for A123].”

There have been three straight month of unfortunate developments for Fisker: In December 2011, it recalled 239 vehicles because of a possible defect in the batteries, and in January sales reportedly were stopped for four days to fix a software glitch.

It has been reported that Fisker is A123’s largest customer, and the bat-tery pack is the most expensive com-ponent in the car. Forbes reports that

O’Neill had downgraded his rating of A123 stock from “hold” to “sell.” In his research note explaining his analysis and recommendation, O’Neill writes that the DOE loan guarantee has “become part of an intense political debate, [and] it may never be restored.” He sees this as part of the political fall-out from the Solyndra hot potato, and he thinks it sets up the possibility of “two Solyndras for the price of one.”

A Boston Globe article reports that about 60 percent of A123’s 2011 reve-nue came from the transportation indus-try. A123 seems to be working hard to make the best of a tough situation. The Globe says the company laid off about 20 percent of its Michigan work-force, affecting about 325 employees. Nevertheless, the newspaper says that since the problems arose with its Fisker business, A123 has raised $23.5 million from investors to fund its growth.

Crain’s Detroit Business reported that the company’s stock fell almost 24 percent following Fisker’s announce-ment that it was delaying the Nina project. That brings A123’s stock down by a sobering 80 percent in the past 12 months.

Jason Forcier, A123 vice president and general manager in Michigan pre-fers to see opportunity, saying in the Crain’s article, “This delay on the Nina project actually helps us by allowing us to pull our engineers to other programs.” A123 recently has reported several sig-nificant sales to power grid companies.

The future of Fisker Automotive’s luxury hybrid vehicle is unclear after DOE suspended its loan guarantee. That affects the fortunes of its vendors, including A123, supplier of the battery packs.

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Forcier is not a lone optimist. The Globe reports that Deutsche Bank ana-lyst, Dan Galves, sees the setback as significant, but temporary, saying, “We still see this company as having done very well in terms of carving out a posi-tion in the advanced lithium-ion bat-tery market.”

Fisker, too, prefers to see the sun-shine between the clouds. Founder Henrik Fisker is quoted in the Reuters story, “Our survival is not dependent on the DOE. We have already looked into alternative financing and we have really good possibilities.”

And, O’Neil may have it wrong with regard to Fisker’s future with the DOE. In the Globe article, a DOE spokes-woman says it “is working with Fisker to review a revised business plan and determine the best path forward so the company can meet its benchmarks, pro-duce cars and employ workers here in America.”

If so, that would be encouraging karma for Fisker and A123. Visit: www.a123systems.com n

The White House’s Office of Science and Technology Policy and the DOE announced that the agency is planning on making available $12 mil-lion each year fund sev-eral efforts related to the administration’s Materials Genome Initiative.

DOE published an “Expression of Interest” announcement via its division of Basic Energy Science, in which BES says it “has an interest in enhancing support for research which could lead to a theory/modeling design paradigm, validated through experi-ment, which could enhance the rate of discovery of new or vastly improved materials, material systems and chemi-cal processes.”

The BES announcement mentions several (not necessarily exclusive) exam-ples of programs in which it is interested.

• Electron Correlation: Many mate-rials of importance to BES’s goals con-tain localized electrons, which are not well described by the widely used den-sity functional theory, including oxide superconductors, magnetic materials and photocatalysts.

• Excited States: Improved descrip-tions of excited states would impact photovoltaic materials, exciton trans-port in organic semiconductors and light absorption in photocatalysts, plus provide a fundamental understanding of chemical reactivity enabling validated theories, models and computational tools for predicting rates, products and dynamics of chemical processes involved in energy utilization and transformations.

• Multiple Length and Time Scales: Projects that couple length scales, advance multiscale modeling or extend the time scale for dynamical simula-tions would be appropriate.

• Electron & Ion Transport: Projects that advance the theoretical under-standing of nonequilibrium effects in transport or provide validated algo-rithms for transport properties would be appropriate.

• Novel Approaches: Efforts that use simulation and digital data in novel ways, such as “inverse design,” “genetic algorithms” or scanning large data sets, including those with mixed theoretical and experimental data, would be appro-priate.

• Coupling Chemistry and Turbulent Flow: Of particular note are

news & trends

Toward Materials Genome Initiative, DOE allocates $12M for software groups, ‘glue’ funding

Two new Material Marvels videos: ‘Thermoelectrics’ and ‘Nanomaterials’ available

Science “popularizer” and Yale associate pro-fessor Ainissa Ramirez has added two new videos to her Material Marvels collection of short, free introduc-tory videos to various materials topics. The videos are available on YouTube via Yale University’s channel or on the Material Marvels website.

Her latest videos are on “Thermo-electrics” and Nanomaterials.”

If you are an engineer or science professional, you already know most of what Ramirez covers in her three- or four-minute presentations, but they are great for primary, secondary and even some college classes. In particular,

she always manages to come up with simple life-sized demonstrations and analogs to smoothly explain her con-cepts (which is often a challenge when in the materials science community attempts to explain what materials sci-ence is about to our family, friends and neighborhood institutions).

Visit: www:materialmarvels.com n

Screen shot of new Material Marvels video “Thermoelectrics.”

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two central issues that have been iden-tified as required to advance the state of the art for predictive simulation of internal combustion engines: dynamics of fuel-injection sprays and stochastic combustion processes.

BES also says it plans on divid-ing the awards to three categories of projects: small groups or single inves-tigator awards; “glue” funding awards to support collaborations between funded BES activities through shared postdoctoral staff, short-term exchange of principal investigators, capability development and related activities; and centers for materials or chemical sci-ences software innovation.

Visit: www.science.energy.gov/bes/funding-opportunities/predictive- theory-and-modeling n

National Research Council names 16 tech priorities for NASA

“Success in executing future NASA space missions will depend on advanced technology developments that should already be underway,” according to a new study by the National Research Council.

However, the report continues, “it has been years since NASA has had a vigor-ous, broad-based program in advanced space technology. NASA’s technology base is largely depleted,” leaving the agency with “few new, demonstrated technologies” to conduct its mission.

Relevant to the materials community is a call for making lightweight and multifunctional materials and structures a priority.

The 2010 NASA Authorization Act required NASA to find a way to maintain its R&D in space technol-ogy. In response, the agency released a strategic plan in early 2011. Of the six points on the plan, five are relevant to NASA’s aeronautics mission and were evaluated in the NRC study. As part of the strategic plan, NASA drafted 14 space technology roadmaps “to identify a number of critical enabling technolo-gies.” The NRC review committee used

these 14 roadmaps as the starting point for its study.

Of the 14 draft roadmaps, two explicitly address materials science issues and four imply materials science. The rest address systems issues, such as propulsion, launch, landing, ITand human health issues.

The study committee teased out three technology objectives from the NASA strategic plan and roadmaps:

• Extend and sustain human activi-ties beyond low-Earth orbit;

• Explore the evolution of the solar system and the potential for life else-where; and

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news & trends

• Expand our understanding of Earth and the universe in which we live.

Although each NASA roadmap identifies the technical challenges to meeting the needs of its technology area, the NRC committee attempted to add some focus. It made a list of which challenges apply to the three objec-tives. The exercise revealed groupings that cut across the three objectives (listed in the press release), which allowed them to identify five “unified technologies.”

In addition, working with the assumption that funding levels would be in the $500 million to $1 billion per annum range, the study committee determined 16 “highest priorities” for technology development.

Of the 16 high-priority technol-ogy challenges, only one was listed under all three objectives: Lightweight and Multifunctional Materials and Structures. Within that section of the roadmap, nine technologies were identified as high priority, including “Lightweight Structure (Materials).”

On the subject of lightweight materi-als the report says,

Advanced composite, metallic, and ceramic materials, as well as cost-effective processing and man-ufacturing methods, are required to develop lightweight structures for future space systems. Lightweight structural materials developed by NASA and other government agencies, academia and the aero-space industry have found exten-sive applications in transportation, commercial aircraft and military systems. Continued NASA leader-ship in materials development for space applications could result in new materials systems with signifi-cant benefit in weight reduction and cost savings. This technology has the potential to significantly reduce the mass of virtually all launch vehicles and payloads, creating opportunities for new mis-sions, improved performance and reduced cost.

The other eight items in this techni-cal area have to do with testing, cer-tification, manufacturing, systems and reliability.

The NRC report, “NASA Space Technology Roadmaps and Priorities,” is dense — 470 pages. It includes a comprehensive description of the com-mittee’s methodologies and recommen-dations. All 14 of NASA’s technical area roadmaps are included.

Visit: www.nap.edu/catalog.php?record_id=13048 n

New ceramic–aluminum com-posite brake rotor developed for mass market

Ceramic-containing brake pads and rotors first began to appear as high-tech solutions for F1 racers and other auto and motorcycle high-performance applications. More recently, they even have been appearing as braking system options in the premium sedan and truck markets.

While this technology is slowly mak-ing its way into mass-market vehicles, R&D work continues on perfect-ing such braking systems. A team of researchers from Polytechnic Institute of New York University and Michigan-based REL Inc. says it has created a next-generation aluminum–ceramic composite brake rotor that cuts the weight 60 percent (compared with cast-iron rotors). The team also says the new rotor’s functionally graded design could triple the lifespan of traditional rotors.

With an eye toward a market worth billions of dollars, REL Inc. applied for and received a $150,000 Phase I SBIR grant from the NSF to develop the initial product design, material and manufacturing process. REL already had established itself as a manufacturer of mixed-matrix components for the auto and aerospace industry. The company recruited the expertise of NYU-Poly’s Nikhil Gupta, an associate profes-sor who leads the school’s Composite Materials and Mechanics Lab.

While mechanically strong, the heavy cast-iron rotors are of a uniform design, which, according to Gupta and REL, contributes to their warpage and wear because of nonuniform temperatures and pressure strains across the surface of the rotor. Instead, they say, the optimal brake rotor needs to be designed with three functional regions, where each region is matched to a material with dis-tinct mechanical and thermal properties.

To accomplish this region-based design, the team begins with a high-temperature aluminum alloy and reinforces it with functionally graded ceramic particles and fibers that impart unique characteristics to each section of the rotor.

Gupta explains in a news release, “The hybrid material allows us to pro-vide reinforcement where additional strength is needed, increase high-tem-perature performance and minimize stress at the interfaces between the zones. Together, this should boost rotor life significantly, reducing warranty and replacement costs, and the weight savings will improve the vehicle’s fuel efficiency.”

Gupta and REL claim their one-piece design will be easier to manufac-ture than current ceramic and ceramic-

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Nikhil Gupta, associate professor in the Polytechnic Institute of New York University Mechanical and Aerospace Engineering Department, is developing a new generation of ceramic brakes to be used in mass-market automobiles. Today’s ceramic brakes are found mostly on race cars, exotic sports cars and motorcycles.

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composite braking systems and be able to penetrate into the $10 billion mar-ket. Their pitch to automakers is that their new rotors will last longer and slash approximately 30 pounds from a midsize sedan.

“As auto companies strive to meet increasingly high-efficiency and low-emissions targets, there’s a tremendous business opportunity in creating novel lightweight components which reduce overall vehicle weight and increase vehicle performance,” says Adam Loukus, vice president of REL.

Visit: http://composites.poly.edu n

MakerBots offers low-cost desktop 3D replicators

Three-dimensional printing is a relatively new but no longer unusual process for materials scientists and engi-neers. Indeed, researchers have been using 3D printers to build and test ideas of prototypes of biomedical scaffolds, casting molds for turbine blades and espresso cups.

Although once relatively rare, such printers are starting to seep into the do it yourself and consumer pipelines, and several companies have received sig-nificant financial backing for hardware and software businesses associated with personal 3D printers.

One company — MakerBots — is selling 3D printers for as low as $1,300. It produces products composed of ABS plastic, but there also are systems becoming available that will make products composed of ceramics, glass, metals and even concrete.

A parallel business line is emerging that markets downloadable 3D pat-terns. For example a Phillips subsidiary, Shapeways, claims to be “the largest marketplace for printable 3D designs.” Another design marketplace and 3D forum is Thingiverse.

Although some of Shapeway’s store owners sell designs for jewelry and toys, others are starting to create more elaborate technical designs. A Time.com story reports, “[D]octors have employed

3D printing to lower medical costs. Mark Frame, an orthopedic surgical trainee at RHSC Glasgow recently used Shapeways and CT-scan information to create a 3D model of a fractured forearm to practice a surgery. Instead of the nor-mal $1,200, the Shapeways model cost just $120. It’s hard to guess what kinds of things will be possible in the future, but aside from hoping to print in gold and mixed materials, [some 3D enthusi-asts] believe that in five or ten years 3D printers will be able to churn out work-ing electronics, such as an iPod.”

The individual pieces from 3D print-ers already can be used to assemble larger structures. Violin and car body prototypes have been built this way. Proponents say it’s only a matter of time before it may be possible to create anything from personal body parts to concrete structures and entire buildings. It’s unclear, however, how small-scale

innovators are addressing the sinter-ing, tempering or annealing work that would be needed to finish objects com-posed of ceramic or glass powders.

Regardless, personal 3D printing seems to be rapidly transitioning from a novelty to a serious technique for pro-ducing and delivering consumer goods.

Visit: www.makerbot.com n

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Bre Pettis, MakerBot CEO, with a Replicator.

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acers spotlight

Welcome to our newest Corporate Members

ACerS recognizes organizations that have joined the Society as Corporate Members. For more infor-mation on becoming a Corporate Member, contact Tricia Freshour at [email protected], or visit us at http://www.ceramics.org/corporate.

Mineral Research Processing (M.R. PRO)www.mineralresearchprocessing.com

New Tech Ceramics Inc.www.newtechceramics.com

Surmet Corporationwww.surmet.com

Glass short course offered in MayMay 20–21, 2012, ACerS is offer-

ing one of its most popular short courses, Fundamentals of Glass Science & Technology. The course is taught by Arun Varshneya, president of Saxon Glass Technologies and retired Alfred University professor. It will be held in St. Louis, Mo., in conjunction with the 2012 Glass & Optical Materials Division Spring Meeting.

The cost of the course is $745 for ACerS members, $835 for nonmembers and $295 for students. To register, call 866-721-3322, or go to www.ceramics.org/gomd2012 n

Turn momentum into successCeramitec 2012 is the “industry’s

leading trade fair” for all ceramics industries and will be held May 22–25, 2012, in Munich, Germany.

The fair occurs every three years, and the 2009 event attracted more than 650 exhibitors from 35 countries and around 15,000 visitors from 84 countries.

The subtheme of the fair is “Technologies | Innovations | Materials.” While the fair serves tradi-tional ceramic industries like brick, tile, whitewares and tableware, it also targets highly engineered ceramic industries like electronics, refractories and more.

Vendors will be showcasing the lat-est raw materials, testing rigs, produc-tion tools and equipment for producing ceramic products. (ACerS will be partici-pating as an exhibitor in booth 127 in hall B6. Be sure to stop by and say hello.)

Augmenting the international theme will be an India Day, where the focus will be on the growing ceramic industry in India.

The week will be a big one for the ceramics world. The International Symposium on Ceramic Materials and Components for Energy and Environmental Applications (an ACerS endorsed meeting) runs May 20–23, in Dresden, Germany. Organizers have worked out a collaboration whereby the last day of CMCEE will be at Ceramitec at the Munich Messe, bringing another 600–800 ceramic engineers and scien-tists to the trade fair. If ceramics is your business, Germany is the place to be this May. Contact: Anita Niebuhr, Tel. 646-437-1014; email: [email protected]; web: www.ceramitec.de/en/home. n

Order of the Engineer: A pledge to professionalism

The American Ceramic Society’s National Institute of Ceramic Engineers is proud to be a part of the Order of the Engineer, an organization that exists “to foster a spirit of pride and respon-sibility in the engineering profession, to bridge the gap between training and experience and to present to the public a visible symbol identifying the engi-neer.” Initiates recite an oath acknowl-edging their obligation as engineers and accept a stainless-steel ring to be worn on the fifth finger of the working hand.

NICE will host an induction cer-emony as part of the MS&T’12 meet-ing in Pittsburgh, Pa. To participate, fill out the application form (on NICE website) and mail it with a check for $25 to ACerS by Aug. 31, 2012.

For information about the form or making payment, contact Marcia Stout at [email protected], tel.: 614-794-5821. The deadline for submitting your application is Aug. 31. 2012.

For information about NICE Order of the Engineer link, fstover@ accesstoledo.com, tel.: 419-878-0001, visit: www.ceramics.org/nice. n

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Send section and member news to Eileen De Guire at [email protected].

CeramiC TeCh TodayGet daily updates and weekly emails on the latest news. Recently we covered– Chinese rare-earth exports– Waste glass in cement– Nano-piezoelectric fabrication– Bone scaffolds by electrospinning– Cars, batteries and businesswww.ceramics.org/ceramictechtoday

Find out why the matching ties at www.ceramics.org/ceramictechtoday.

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Section will present Toledo Glass and Ceramic Award to Faber

The Michigan/Northwest Ohio Section of ACerS is holding the Toledo Glass and Ceramic Award Presentation and Dinner on Thursday, April 19, 2012, at The Toledo

Club, in Toledo, Ohio. The award recognizes distinguished scientific, tech-nical or engineering achievements in glass and ceramics.

This year’s award recipient is Katherine T. Faber, in recognition of her research on the mechanical behav-ior of ceramics and ceramic composites, outstanding service and leadership in scientific and educational organizations related to the field of ceramics and advancing the role of women in science and engineering. Faber is a Fellow of ACerS and was president 2006–2007. She will deliver a talk for the occa-sion titled, “Coatings for 18th Century Porcelains and 21st Century Engines.”

Faber also is the lead organizer of the 4th International Congress on Ceramics in Chicago, Ill., July 15–19, 2012.

For more information contact Janet Bailey, email: [email protected]; tel.: 248-348-6585; web: http:// ceramics.org/sections/michigan-and-northwest-ohio-section. n

SPIE names Sundaram senior member

S.K. Sundaram, Inamori Professor of Materials Science in the Kazuo Inamori School of Engineering at Alfred University, is one of 166 researchers world-

wide selected for senior membership

in SPIE, an international society for optics and photonics. He was chosen for his “achievements in millimeter wave material diagnostics and sensing.” Sundaram’s primary research interests include terahertzmillimeter wave sci-ence and technology, multiscale materi-als processing, live-cell spectroscopy for rapid screening and ultrafast materials science and engineering.

He also is a Fellow of ACerS and several other professonal societies. n

Chinese Academy elects Wadsworth Foreign Fellow

Battelle presi-dent and CEO Jeff Wadsworth was elected a Foreign Fellow of the Chinese Academy of Engineering.

Every two years, a small number of

Foreign Fellows are elected to the CAE, which comprises only 500 scientists. Wadsworth was one of only six non-Chinese scientists elevated to member-ship in the CAE. n

people in the spotlight

Faber

Sundaram

Wadsworth

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In Memoriam Eva Zeisel

Some detailed obituaries also can be found on the ACerS website, www.ceramics.org/in-memoriam

CorrectionsNames of two PCSA committee

leaders were misspelled.

Samara Levine, Communications Committee Chair

Mona Emrich, Recruitment Committee Chair

Levine Emrich

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advances in nanomaterials

Making ferroelectric nanorocks with an atomic force micro-scope hammer

Ever heard the saying, “Ceramic engineering is all about making big rocks into little rocks, and then making little rocks into big rocks”? A recent Rapid Communication in the Journal of the American Ceramic Society seems to have this saying in mind.

The short paper by a Korean team, Son and Jung, describes a novel method of making discrete ferroelectric particles by a method that amounts to making “little rocks out of big rocks” — but on a nanoscale.

The investigators were interested in fabricating PbTiO3 nanodots for ferro-electric random access memory, which is a promising material for nonvolatile memory applications.

Demand for smaller devices is driv-ing the development of high-density, high-performance memories, and fur-ther downsizing is starting to run into physical limitations imposed by materi-als properties and processing.

Son and Jung’s idea was simple: Make a nanodot, whack it with a ham-mer, anneal to crystallize the shattered pieces and, finally, test for ferroelectric-ity. Their goal was to fabricate PTO nanodots less than 10 nanometers in diameter with ferroelectric properties.

Using dip-pen lithography, they made a PTO nanodot that had a 40-nanometer diameter and was 25 nanometers thick. Using an atomic force microscope tip as a hammer, the dot was shattered after “repeated col-lisions,” that is, they had to beat on it. The resulting nanoparticles ranged in size from several nanometers to a few tens of nanometers, and were of “diverse sizes in both diameter and thickness.”

After crystallization, tests showed that ferroelectric properties were pres-ent in a 25-nanometer-diameter by 11-nanometer-thick nanodot and in a

10-nanometer-diameter by 8-nanome-ters-thick nanodot. The 10-nanometer-diameter nanodot, according to the article, is “closer to the theoretical critical size” than has been achieved in other studies. PTO nanodots that were less than about 3 nanometers thick proved difficult to test because of high leakage currents.

The paper is “Ferroelectric PbTiO3 Nanodots Shattered Using Atomic Force Microscopy,” Jong Yeog Son, Inhwa Jung, JACerS. DOI: 10.1111/j.1551-2916.2011.05026.x.

Visit: www.kyunghee.edu n

Navy looks to use $6M to lure ideas for ‘bottom up’ building of carbon-based nanoelectronics

The Office of Naval Research has announced that it is interested in encouraging “research and innovation in bottom-up chemical synthesis and assembly of carbon-based, particularly graphene-based, electronic devices and circuits with atomic precision and ang-strom resolution,” and has just issued a Basic Research Challenge to stir up interest and submission of ideas.

The program, says ONR in the announcement, will support basic research on building new electronic devices and circuits “from the molecu-lar level up, using molecular synthesis,

surface catalytic chemistry and other novel techniques.”

ONR says it envisions several stages to the projects it hopes to fund. The beginning emphasis will be on “syn-thesis of graphene nanostructures with controllable predetermined shape and atomically sharp edges, e.g., graphene nanoribbons.” Dimensionally, it says it is interested in nanoribbons a few nanometers wide and longer than 100 nanometers. During this initial phase, ONR also wants to have methods developed to transfer the nanoribbon to nonmetallic substrates.

The middle phase of the projects would focus on “synthesis of molecules that perform as graphene-based circuit elements and, eventually, to rationally design and assemble them into ‘circuit molecules’.”

Eventually, ONR wants the projects’ emphasis to evolve into creating “ways to interface the molecularly derived graphene circuit elements and circuits, and impedance match them, with top-down manufactured systems at microm-eter scale” and also “interface with other molecules, such as other carbon allotropes (CNT, C60, etc.), graphene derivatives (hydrogenated and/or fluo-rinated graphene) and other closely related non-carbon materials (hexago-nal boron nitride, silicene, MoS2, etc.).”

The Navy imagines funding some-where between two and six different projects using a fund of $6 million spread out over five years.

Interested individuals are encouraged to first submit short white papers, by March 31, 2012.

Full proposals should be submitted by May 1, 2012. The ONR announcement mentions the grant opportunity funding number is 12-SN-0003. ONR says final funding decisions will be made by May 15, and grants will be awarded July 1.

Visit: www.onr.navy.mil/Contracts-Grants.aspx n

Ferroelectric lead titanate nanodots were shattered using an atomic force microscope tip to make nanodots less than 10 nm diameter.

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research briefs

Ground-up waste glass improves cement properties

An unlikely pairing of materials that are claimed under the umbrella of ceramic materials—glass and concrete —appears to be working out well on several levels.

Both of these materials are staples of modern life and are produced in enor-mous quantities. Both carry some seri-ous environmental baggage with them. But, work conducted over the past two years at Michigan State University is showing that incorporating ground-up waste glass into concrete actually improves the properties of the concrete. According to a university news story, “the concrete is stronger, more durable and more resistant to water.”

The research comes out of the MSU Department of Civil and Environmen-tal Engineering and was supervised by Parvis Soroushian. Soroushian and his doctoral student, Roz-Ud-Din Nassar published two papers in 2011 on their work.

There have been past efforts to incorporate waste glass into concrete as the aggregate phase, but, according to their paper, “These efforts neglected the reactive nature of glass in concrete, which was slowed down due to the relatively large (millimeter-scale) size of the glass particles.” The paper was published in the Journal of Solid Waste Management and Technology.

Recognizing that waste glass is an excellent source of amorphous silica, they realized that it has the right chem-istry and reactivity “to enter pozzolanic reactions with the lime released during hydration of cement,” and that “these reactions can yield highly stable end products with desired binding quali-ties,” i.e., cement.

What is a pozzolanic reaction? According to the American Concrete Institute website, pozzolan is “siliceous or siliceous and aluminous material,” and by itself, is not cementitious. How-ever, fine particles of pozzolans will react in the presence of moisture with calcium hydroxide to form cementitious

compounds, hence the description, “pozzolanic reaction.”

Naturally occurring pozzolans include volca-nic pumicites, opaline cherts and shales, clays and diatomaceous earths. Artificial pozzolans include fly ash, silica fume and, now, waste glass.

The researchers used a mix of colored waste glass ground to an aver-age particle size of 25 micrometers (93 percent passing #325 sieve) and substituted it for cement in amounts of 15, 20 and 23 percents by weight. In all cases, the mixes were prepared at ready-mix concrete plants, and crushed lime-stone and nonreactive river sand were used in the mixtures. In their paper they report that incorporating glass par-ticles is “compatible with conventional concrete production and construction techniques.”

Slump tests showed that the “fresh mix workability” of the glass-containing mixtures was a little lower for the two mixes with more glass. The 15-weight-percent mixture had the same slump-ing properties as the control batch of concrete. The authors suggest the nonspherical and rough geometry of the glass particles may contribute to the reduced workability.

In addition to lab tests, the mixes were field tested at several sites on the MSU campus, including driveways, heated pavements, sidewalks, gut-ters, curbs and parking stands. The 20-percent-glass mix was used for the field tests.

Test specimens were prepared at the time that the concrete was poured in the field, and, at several time intervals after pouring, cores were drilled from the field locations. Tests included compressive and flexure strength, water sorption, chloride permeability and

abrasion resistance.SEM work showed that the glass-

containing cement had a relatively dense and uniform microstructure compared with the control composi-tion. The authors attribute the micro-structure differences to “the pozzolanic reactions of milled waste glass yielding secondary calcium silicate hydrate (C-S-H).”

The authors report that after two years of exposure to Michigan weather and service loads (from cars, trucks and pedestrians), the waste glass improves the durability and abrasion resistance of the concrete. They conclude, “[T]he use of milled waste glass in concrete is a viable practice which would result in important energy, environmental and cost benefits, and would make impor-tant contributions toward reducing the carbon footprint of the construction industry.”

How important might those contri-butions be? They provide some interest-ing facts in the paper, which speak for themselves. Consider:

• 12.5 million tons per year of waste glass generated in US;

• 77 percent goes to landfills;• 6 percent by weight of municipal

solid waste is glass;• Every ton of cement manufactured

Adding ground waste glass to cement mixes improves its durability, according to MSU researchers.

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generates a ton of CO2 emission;• US cement production in 2007

was nearly 100 million tons, pumping nearly 100 million tons of CO2 into the atmosphere;

• 90 percent of the energy used to make concrete is used to make the cement;

• One ton of cement consumes about 5.5 million Btu of energy;

• Two percent of global primary energy consumption is used by the cement industry; and

• Only aluminum and steel manu-facture use more energy.

A second paper on the work was published in the Journal of Construction and Building Materials and is available online.

Visit www.egr.msu.edu/cee/people/soroushian.html n

Modeling sintering without constitutive equations

Sintering is among the most funda-mental and important processes applied to ceramic materials. In its essentials, it is simple: Densification by heating. The details, however, are complicated, and modeling has proved to be a useful tool for understanding the driving forces and mechanisms that govern sintering processes.

One challenge with modeling is the issue of scale. Different mathematical models are needed to describe physical processes depending on the scale of the object of interest. It is difficult and not necessarily accurate to derive meaning from the output of a model in one size regime that is applied to a different size regime. For example, the mathematics that describes the atom-level process of solidification of a metal is very different from the mathematics that describes the casting shrinkage of an engine block, even though the former deter-mines the latter.

A new paper in the Journal of the American Ceramic Society describes a new approach to modeling the sintering process that gets around the scale prob-

lem. The paper has a deceptively simple title, “Direct Multi-Scale Modeling of Sintering,” and is authored by ACerS Fellow Eugene Olevsky, from San Diego State University, and three others from institutes in the Ukraine and Russia.

The paper addresses “continuum sintering theory,” which models “sinter-ing of macroscopically inhomogeneous porous specimens.” The macroscopic inhomogeneity arises from presintering processes, such as powder pressing or forming. It also can arise from bound-ary constraints or from structural con-straints within the specimen itself, such as with multilayer composites.

Advances in continuum theory, the paper says, are due largely to “the use of comparatively simple special constitutive equations of sintered porous materials.”

Constitutive equations are mathe-matical descriptions of the relationship between stress, strain, strain rate and microstructural features like grain size. The coefficients in the equations are functions of internal material param-eters. Sintering kinetics are known to depend on grain size, pore-size distribu-tion, pore coarsening, pore and grain morphology and other parameters. A limitation of previous models has been an inability to expand the models to include more than one parameter.

The question is how to solve this

limitation and expand the models to accommodate multiple parameters. The paper lists three current barriers: experimentally determining the inter-relationships between multiple param-eters is difficult and time consuming; a multiparameter approximation of the experimental data in the constitutive equations is necessary; and the number and identification parameters to include in the model is not known.

However, the new approach does not rely on constitutive equations. Instead, “the results of modeling at the mesoscopic level are directly used for the prediction of the macroscopic behavior,” hence, the “direct” part of the paper’s title.

Mesoscopic modeling defines and analyzes the “evolution of a set of unit cells of a powder material during sintering.” In this paper, a unit-cell is a “representative mesoscopic volume of the material,” and the mesoscopic scale correlates to the structure level of the powder particles. The macroscopic level is the specimen being sintered. The “multi-scale” aspect refers to a simultaneous numerical analysis of the sintering processes at the powder par-

research briefs

Schematics of unit-cell formation from powder packing (above) and linking of microscopic and mesoscopic structure levels (below).

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ticle (mesoscopic) and specimen (mac-roscopic) levels.

The model starts by setting a control point, and then several finite elements around the point comprise the meso-structure/unit-cell. Using numerical analysis, macroscopic material param-eters like viscosity and sintering stress are found in what amounts to a virtual testing of the unit-cell independent of constitutive equations. Values of prop-erties are fed into a macroscopic finite element model, which allows macro-scopic effects like distortion and shrink-age to be determined.

The paper demonstrates the model-ing method for two cases: diffusion sintering of ceramic composites and viscous sintering. The researchers are able to show that the “evolution of the unit cells is connected with the mac-roscopic level shape distortion,” based on assumptions about the similarity of the macroscopic and mesoscopic strain rates.

Besides Olevsky, the paper (doi:10.1111/j.1551-2916.2012.05083.x) is authored by Andrey Maximenko, Andrey Kuzmov and Evgeny Grigoryev. n

Silicate layer is key to low-temperature bonding of silicon carbide

Researchers at University of Glasgow, Scotland, have been working on build-ing equipment and instruments for studying gravity, on the ground and in space. The team is led by UG professor in the School of Physics and Astron-omy, Sheila Rowan. According to the Institute for Gravitational Research website, the group’s work “is targeted at the development of detectors and signal analysis methods to search for gravita-tional waves from astrophysical sources. Gravitational waves — waves in the curvature of space-time — are a predic-tion of General Relativity.” The website goes on to describe work the group is doing on detection techniques based on kilometer-scale laser interferometry

and other highly sensitive instruments. The instruments require components that are made by precision manu-facturing of highly stable materials: silicon carbide, for example.

Silicon carbide is an attractive material for space and other applications that require strong, lightweight structures. A researcher on the team, Christian Killow, says in an online story on The Engineer website, “Sili-con carbide is very hard and very tough. It’s quite brittle but it’s very good at absorbing impact.”

But, it is not easy to join. Killow continues, “It just kind of sits there and does nothing, so when you want to stick something to it, it’s not very easy to do.”

The Glasgow work builds on hydrox-ide catalysis work first pioneered and patented by Jason Gwo while he was working at Lawrence Livermore National Lab when he was looking for a way to join very flat fused silica pieces for a telescope assembly. Accord-ing to the researchers, Gwo realized that “bonding may occur between flat surfaces of a number of materials if a silicate-like network can be created between the surfaces.”

That is, the molecular structure of the surfaces can be altered in such a way as to encourage a chemical bond between them.

The resulting bonding interfaces are very thin, less than 100 nanometers. According to Killow, “There are a lot of things that can go wrong, but when the bonds go well they very nearly inherit the bulk strength of the materi-als that they’re bonding.”

The chemical-bonding mechanism of hydroxide bonding is a three-step process: hydration and etching; polym-erization; and dehydration. Gwo used alkaline bonding solution, such as sodi-um or potassium hydroxide, or sodium silicate. The solution etches into the

silica and causes polymerization of the surface, causing chains of molecules to form between the joining surfaces.

Chains of hydroxide molecules form naturally on the surfaces of many mate-rials, but not on SiC. The Glasgow group formed a silica layer on the SiC surface, which provided a surface for attaching hydroxide ions by applying a hydroxide-containing bonding solution. The interaction between the hydroxide ions on the bonding surfaces creates the bond in the same way that Gwo joined fused silica pieces.

The process can be used to join SiC to itself or any number of dissimilar materials, such as sapphire, aluminum, silicon and zinc. The thinness and stability of the joint make it especially well suited for manufacturing high-pre-cision equipment and instruments.

According to the story, the bonding process can be tailored to specific appli-cations. But, Killow offers the caveat, “The logistics of bonding things is a strange process. It will either fail spec-tacularly or really work quite well. … We’re still developing the process and refining it.”

In an unusual move, the researchers have made the technology available without charge through the Easy Access IP program at UG.

Visit: www.gla.ac.uk/businessand-industry/technology/easyaccessipdeals/headline_179965_en.html n

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A method for bonding silicon carbide has been devel-oped at the University of Glasgow. This image shows a join between silicon ingots that was made in a simi-lar way.

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ceramics in energy

Investigators at the Georgia Institute of Technology have demonstrated a promising new manufacturing process to form piezoelectrically active fer-roelectric nanotubes based on lead zirconate titanate and other nanostruc-tures. Most importantly, the process can deliver custom-defined shapes, locations and pattern variation across the same substrate. Specialists at Oak Ridge National Laboratory confirmed the work by nanocharacterization.

The Georgia Tech researchers call their technique “soft template infiltra-tion” and say that it could represent a big leap in making nanoelectromechan-ical systems and devices. The break-through comes from using a “soft” poly-meric template that decomposes when the ferroelectric material crystallizes.

According to a news release from the school, the ability to tailor the properties and dimensions of these free-standing structures, plus their strong piezoelectric response, “could ultimately lead to production of actively tun-able photonic and phononic crystals, terahertz emitters, energy harvesters, micromotors, micropumps and nano-

electromechanical sensors, actuators and transducers — all made from the PZT material.”

“We are using a new nanomanu-facturing method for creating three-dimensional nanostructures with high aspect ratios in ferroelectric materials that have attractive piezoelectric prop-erties,” says Nazanin Bassiri-Gharb in the release. She is an assistant professor in Georgia Tech’s Woodruff School of Mechanical Engineering. Bassiri-Gharb and others report on this work in the paper, “Free-Standing Ferroelectric Nanotubes Processed via Soft-Template Infiltration” in Advanced Materials (doi:10.1002/adma.201103993).

In the paper, the authors say they can control the formation of nanotubes with outer diameters in the range of 100–200 nanometers, wall thickness ranges of 5–25 nanometers and aspect ratios as high as 5:1.

Previously, somewhat similar struc-tures have been fabricated using what are grouped into either “top-down” or “bottom-up” processes. According to Bassiri-Gharb, her team looked for a more agile alternative process because top-down methods can cause surface damage (that degrades the ferroelectric and piezoelectric performance) and the existing bottom-up approaches, here-tofore, have not been able to combine precise location and high aspect ratios.

“This technique gives us a degree of control over the three-dimensional process that we’ve not had before,” she says. “When we did the characteriza-tion, we saw a size effect that until now had been observed only in thin films of this material at much larger size scales. … These are truly smart materials, which means they respond to external stimuli, such as applied electric fields, thermal fields or stress fields. Devices made from these materials could be fine-tuned to respond to a different wavelength or to emit at a different wavelength during operation.”

The soft template infiltration tech-

nique begins with making the template. In the group’s report, they discuss using a silicon substrate that has been spin-coated with a polymeric negative elec-tron-beam resist material, followed by electron-beam lithography. (The group notes that a variety of other patterning techniques could be used to create the template.)

Next, a thin layer of aluminum oxide is added on top of template, which is then immersed in a bath containing a sol–gel precursor solution for PZT. After it is pyrolyzed, the material is annealed in a two-step heat-treating process, which crystallizes the material and dissipates the polymer substrate. What remains are freestanding PZT nanotubes connected by the aluminum oxide layer. Alternatively, they can produce nanorods or nanowires, instead of nanotubes, simply by increasing the amount of chemical infiltration.

Making the innovative nanostruc-tures is one thing, but characterizing them is another. Bassiri-Gharb says her group “leveraged a new characterization method available through Oak Ridge to study the piezoelectric response of these nanostructures on the substrate where they were produced.”

Tailored piezoelectric nanostructures via ‘soft template infiltration’

SEM images of the PZT nanotube arrays, all with outer diameters of approximately 100 nanometers. The hexagonal patterns are approximately three micrometers wide.

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Composite SEM image of PZT nanotube arrays and their piezoelectric response as measured by band-excitation PFM (BE-PFM).

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As it turns out, ORNL research-ers, such as coauthors Sergei Kalinin and Alexander Tselev, had a novel technique of their own. The duo, who work at the lab’s Center for Nanophase Materials Sciences, tested a new meth-od that permits high-accuracy, in-situ measurements of the nanoscale piezo-electric properties of the structures. (Kalinin received ACerS’s Ross Coffin Purdy Award in 2003 and is an expert on band excitation scanning force microscopy and functional imaging on the nanoscale.)

The characterization techniques and analysis—worthy of a separate story—made use of what has been called band-excitation piezoresponse force microscopy. The BE-PFM approach, which is based on atomic force micros-copy, allowed Kalinin and Tselev to precisely separate the properties of the AFM tip from those of the PZT sample. According to the news release, the BE-PFM delivered sufficient detail to detect the size-scale piezoelectric effects.

What did they find? Bassiri-Gharb says, ”One of our most important obser-vations is that these piezoelectric nano-materials allow us to generate a four- to six-factor increase in the extrinsic piezoelectric response compared with the use of thin films. This would be a huge advantage in terms of manufac-turing because it means we could get the same response from much smaller structures than we would have had to otherwise use.”

Besides smaller structures, the researchers note in their paper two other big advantages to soft template infiltration. First, “the approach can be tailored for a variety of ceramic materi-als by appropriate choice of sol–gel pre-cursors and processing temperatures.” Second, they continue, “this nanoman-ufacturing method is easily scaled for larger patterned areas by use of nano-imprint lithography instead of EBL for creation of the soft templates.”

Visit: www.mse.gatech.edu n

Innovative catalytic ceramic porous membrane key to Gas2’s pilot gas-to-liquids plant

Processes for turning natural gas-to-liquid fuels have been around for about 200 years, but large-scale adoption of GTL technologies has generally lan-guished in recent years, primarily because of relatively high investment costs in a market where prices tend to fluctuate from year to year. Interest, however, continues in GTL systems, especially with the exploration of shale-based gas reserves in the United States, which might present an abundant feedstock.

Thus, it is timely that a Scottish company, Gas2, which has been plug-ging away at developing lower-cost gas-reforming technologies, announced it is moving ahead with construction this year of a novel pilot reactor plant that it hopes will show that GTL production can be cost competitive.

According to the company, the goal of Gas2’s new £5.5 million facility will be to demonstrate that it can convert “natural gas to liquid hydrocarbon more economically and cleanly than has previously been possible with conven-tional large-scale GTL technologies. … The Gas2 approach is expected to result in considerably lower capital and operational expenditure and a smaller environmental footprint compared to conventional GTL technologies.”

“We are entering a new and exciting phase with the build of the pilot plant which will validate on a larger scale the commercial viability of the Gas2 process. We have a unique technology and process, and the commercial prize is great for a successful outcome,” says Mike Fleming, cofounder and managing director of Gas2.

It appears that the key component of the technology Fleming refers to is a catalytic ceramic-based porous membrane that opens up an alternative route to that being pursued by other developers of small to medium GTL processes.

Generally speaking, the GTL process requires two steps: A feedstock gas is converted into syngas, and then the syngas is converted into liquid hydro-carbon via the Fischer–Tropsch process. Both of these steps can have several complicated stages. For example, the production of syngas typically requires careful generation of steam and oxygen, which is mixed with the feedstock gas.

Gas2 says its catalytic ceramic mem-branes permit a simpler GTL design: The syngas and FT units are still separate, but the stages in each can be reduced. The company is understand-

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First generation of Gas2 ceramic mem-branes before catalytic dressings are applied.

Gas2 membrane dressed with catalyst.

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ceramics in energy

ably tight-lipped about the specifics of their membrane and system, but in the story, “GTL Just Got Smaller,” which appeared last year in The Chemical Engineer, Fleming and Gas2 engineer Ruben Rodriguez wrote that Gas2’s modular GTL technology still uses a two-step process, but each has only two stages. Their patented and trade-marked porous membranes are used in both steps, first in a reactor to achieve catalytic partial oxidation of the feed-stock gas into syngas, and then to transform the syngas to liquid fuels via a membrane running a low-temperature Fischer–Tropsch process.

In the story, they explain, “The technology is designed to work with oxygen-enriched air rather than pure oxygen, eliminating the need for air separation units. There is no need for steam during syngas generation and no compression between the syngas and FT units, reducing the amount of equip-ment and capital expenditure needed.

Meanwhile, the Gas2 porous mem-brane reactors use asymmetric mul-tichannel membranes composed of a porous catalyst support and a filtering layer based on a mix of oxide materials, such as titania and alumina. This gives the membranes greater thermal con-ductivity and an increased surface area for catalyst support, which, coupled with a negligible pressure drop, result in improved heat and mass transfer.

The mechanical strength of the porous membranes allows operability at pressures of up to 80 bar (or about 1,200 psi) and temperatures as high as 1,000°C. The catalyst embedded in the membrane is rhodium for syngas gener-ation, whereas a cobalt catalyst is used to produce liquid fuels in the Fischer-Tropsch reactor.”

Capacity-wise, they say that one barrel of liquid fuel can be produced from 10,000 cubic feet of natural gas (at standard conditions). Gas2 says its system is flexible and will work with stranded gasses, various gasses derived from shale deposits and offshore “asso-ciated” gasses (e.g., unwanted oilfield

gasses that are often flared off). The company says that their FT process can create end products that include “gaso-line, diesel, waxes, ammonia, methanol, hydrogen and ethylene for industrial use.”

Part of what Gas2 wants to dem-onstrate with the pilot plant is how a modular design can offer greater flex-ibility at low cost. On its website, the company says, “The advantage of this modular design is that it can achieve large capacities (between 50–50,000 barrels per day) by adding more modu-lar reactors.” The company says that its syngas and FT units can operate as stand-alone modules, too.

Gas2 says it will build and begin testing the plant this year, and then launch a commercialization phase in 2013. The company reports that mon-ies for the pilot plant are coming from “existing shareholders, including Lime Rock Partners LLP, Robert Gordon University and a group of private inves-tors with substantial interests in the oil, gas and hydrocarbons processing industries.”

Visit: www.gas-2.com n

Alta Devices reports NREL verification of 23.5 percent effi-ciency for counterintuitive solar panel

The steady march to grid parity for solar energy devices continues: A Santa Clara, Calif., maker of gallium arsenide photovoltaic panels, Alta Devices, announced that the NREL verified that its top-line panels operate at 23.5 per-cent efficiency. The ability to deliver an entire high-efficiency panel is a big step forward for the company’s busi-ness, which last year achieved verified record-setting efficiencies as high as 28.2 percent with a single, single-junc-tion PV cell.

This looks to be a record efficiency-level for PV panels. Although, NREL has verified higher efficiencies in other PV arrangements, they have been for a single or small sets of PV cells, not full

panels. (Sanyo asserts that its in-pro-duction silicon heterostructure panels come near to the numbers achieved by Alta, but this has not been verified by NREL.)

In a news release, Alta Devices explains a little bit about its interest in GaAs-based devices. The company says, “Alta chose to focus on GaAs because of its intrinsic efficiency advan-tages as well as its ability to generate electricity at high temperatures and in low light. This means that Alta’s panels have substantially higher energy density than other technologies, generating more kilowatt-hours of energy over the course of a year in real life conditions.”

Some investors have been cautious about GaAs-based solar technologies, because they generally have appeared to require higher-priced materials than, for example, silicon. But the com-pany says, “though GaAs is known for being expensive to produce, Alta has invented a manufacturing technique that enables extremely thin layers of GaAs that are a fraction of the thick-ness of earlier GaAs solar cells. Alta’s cells are about one micron thick. … In utilizing very thin devices that have the highest energy density possible, the cost of the material needed in Alta panels remains low, and the potential costs of an entire solar energy system based on Alta’s technology could be dramatically reduced.”

Alta deposits the GaAs on a thin, flexible film substrate. By focusing on this form factor, Alta says its film “has the potential to be integrated in wholly unique ways and into a variety of appli-cations, including roof and building materials, and numerous military, con-sumer and transportation products.”

The company was cofounded by two well-known California scientists engaged in academic-based energy research, CalTech’s Harry Atwater and University of California at Berkeley’s Eli Yablonovitch. Atwater is direc-tor of the Energy Frontier Research Center on Light-Matter Interactions and director of the Resnick Institute for

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Science, Energy and Sustainability, and Yablonovitch is director of the NSF Center for Energy Efficient Electronics Science, at their respective schools. Alta has received venture capital fund-ing from high-profile groups, such as August Capital and Kleiner Perkins Caufield & Byers.

In a recent story on the Lawrence Berkeley National Lab website, Yablonovitch offered a fundamental defense of GaAs. He said, “Gallium arsenide absorbs photons 10,000 times more strongly than silicon for a given thickness but is not 10,000 times more expensive,” says Yablonovitch. “Based on performance, it is the ideal material for making solar cells.”

But the trick is to extract the high efficiency from GaAs. In a June 2011 release, Yablonovitch explained, “Up until now it was understood that to increase the current from our best solar materials, we had to find ways to get the material to absorb more light. But, the voltage is a different story. It was not recognized that to maximize the voltage, we needed the material to generate more photons inside the solar cell. Counterintuitively, efficient light emission is the key for these high effi-ciencies.”

How are these efficiencies and energy density being achieved? For one thing, it required some open-mindedness. The LBL story describes that a leap in logic had to occur: “Past efforts to boost the conversion effi-ciency of solar cells focused on increas-ing the number of photons that a cell absorbs. Absorbed sunlight in a solar cell produces electrons that must be extracted from the cell as electricity. Those electrons that are not extracted fast enough, decay and release their energy. If that energy is released as heat, it reduces the solar cell’s power output. [LBL’s Owen Miller] calculated that if this released energy exits the cell as external fluorescence, it would boost the cell’s output voltage. ‘This is the central counterintuitive result that per-mitted efficiency records to be broken,’ Yablonovitch says.”

“In the open-circuit condition of a solar cell, electrons have no place to go so they build up in density and, ideally, emit external fluorescence that exactly balances the incoming sunlight. As an indicator of low internal optical losses, efficient external fluorescence is a necessity for approaching the [theoreti-cal efficiency] limit,” Miller said.

In other words, the Alta Devices PV

panels achieve high efficiency by emit-ting certain light while converting solar energy, instead of allowing excess elec-tron energy to build up internal heat.

On the processing side of things, the company says it “is making substantial progress on the build-out of its pilot manufacturing line, which uses mostly off-the-shelf equipment with some proprietary optimizations unique to Alta’s process. Moreover, Alta is start-ing to plan for full-scale production, with activities such as building strategic manufacturing partnerships and select-ing its first large, commercial manufac-turing site.”

Visit: www.altadevices.com n

VO2 foils eyed for mass produc-tion for thermochromic window applications

The notion of making functional and flexible ceramic foils is fascinat-ing, but perhaps a little counterin-tuitive. Nevertheless, there is news of transparent and flexible film foils based on vanadium dioxide developed by Chinese researchers, including ACerS member Yanfeng Gao at the Shanghai Institute of Ceramics. The new VO2 film is being eyed for use in

Conversion efficiencies of the best research solar cells worldwide from 1976 through 2011 for various pho-tovoltaic technologies; efficiencies determined by certified agencies/laboratories.

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thermochromic windows, which retain transparency in the visible range but dynamically regulate the passage of wavelengths that transfer solar heat and energy in the ultraviolet and infrared ranges.

Smart window researchers have had an interest in VO2 because they would like to exploit a particular property: At 68°C (in the case of VO2 bulk single crystals), the material undergoes a reversible, thermally induced phase transition that shifts the optical proper-ties in the near-infrared region from a low-temperature transparent state to a more reflective state.

In an email, Gao says materials based on VO2 nanoparticles, particularly VO2 foils that easily can be used with glass panels, are attractive for applications in construction and automotive industries. Heretofore, making such foils from solu-tions of nanoparticles has been tricky and unreliable because of the instabil-ity of the nanoparticles. But, Gao and his colleagues report in a paper in the Royal Society of Chemistry’s journal, Energy and Environmental Science, that they have figured out a new process that solves previous shortcomings and may be scalable to large-area mass pro-duction.

Gao, who works in SIC’s State Key Laboratory of High Performance Ceramics and Superfine Microstructure, says, “In this paper, we report a novel all-solution process that can be used to prepare transparent, stable and flexible VO2-based composite films. These films exhibit UV-shielding properties and an excellent temperature-responsive thermochromism in the near infrared region.”

The breakthrough? Gao says the answer came when the group coated the VO2 nanoparticles with a thin SiO2 shell. “The shell,” Gao says, “signifi-cantly improved their anti-oxidation and anti-acid abilities.”

Essentially, the VO2 nanoparticles are given a SiO2 shell using tetraethyl orthosilicate (the thickness of the shell can be fine-tuned) and treated with a silane couple to increase dispersion. The last step is to cast the suspension on a PET substrate.

At 13.6 percent solar modulation efficiency, the researchers report in the paper that their VO2-based film is able to match the efficiency levels of other thermochromic films. This also is con-siderably higher than VO2 films pro-duced by sputtering and other methods.

Gao says, “Traditional glass foils are

usually based on thin notable metal lay-ers for reflection of solar irradiation or organic dyes that can absorb solar heat. … The stability of these kinds of foils is still questionable. To our knowledge the current research reports on the first VO2 ceramic foils, and, more impor-tantly, the foils show excellent optical properties (visible transmittance and solar modulation ability, maybe the best in the world).”

As far as “smart” performance goes, Gao et al. report in the paper that they observed while testing a typical sample of the VO2 film, “… in a heating cycle from 35°C to 85°C, the transmittance at 1,500 nanometers decreased from 57.7 percent (at 35°C) to 14.9 percent (at 81°C) gradually. … In a cool-ing cycle, the transmittance of film increased from 14.9 percent (at 75°C) to 57.7 percent (at 35°C).”

The promise of increased energy effi-ciency via thermochromic windows has drawn worldwide attention. Gao says it is a big concern for developing coun-tries, such as China, which already has buildings occupying 52 billion square meters “waiting for new techniques to improve their energy efficiency and to reduce greenhouse gas emissions. We are aiming to develop a new material along with a novel process that can be finally commercialized and used for building glasses.”

Gao says scaling the group’s tech-nique to large-area production is the next challenge, and says that a col-laborative effort is worthwhile. “This method should be considered as a basis for mass production,” he says. “The method should combine with some techniques to efficiently fabricate and to improve performance–cost ratios. … We hope that colleagues working in related fields can join to consider innovations based on the current tech-nology. As an important part of an eco-home, we hope that such kind of smart windows can be applied practically in the near future.”

Visit: http://english.sic.cas.cn/ n

Photographs of sample films at room temperature.

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Much of the basics of electrospin-ning have been figured out, and it is relatively easy to use a desktop appara-tus to spin mats of a particular material or even functionally graded materials. Therefore, a lot the recent emphasis on electrospinning has been devoted to scaling up these systems for mass pro-duction. However, a group of investiga-tors with the University of Alabama at Birmingham’s School of Engineering have come up with an ingenious meth-od of using electrospinning to build a superior three-dimensional scaffold of nanofibers that, it is hoped, will pro-vide a boost to tissue engineering.

The problem the group was trying to solve when they made their discovery was that the typical electrospun mat does not do so well serving as a frame-work for facilitating cell and tissue growth. The fibers’ mass (along with remaining solvents) tended to flatten these mats, making them less than ideal for penetration by growing cells.

Nanoscaffolds support the adhe-sion, growth and function of various cell types as they mature into specific tissues, such as tendons, muscles and bones, during tissue engineering. Yet, the traditional industry method for electrospinning creates densely packed sheet-like structures that prevent cells from penetrating the nanoscaffolds.

In a paper in Biomaterials titled ”Cell infiltration and growth in a low-density, uncompressed three-dimensional electrospun nanofibrous scaffold,” (doi:10.1016/j.biomateri-

als.2010.10.056), UAB’s Ho-Wook Jun and others in his group describe how they created their method to build a three-dimensional “cotton ball” of electrospun polycaprolactone that has the more desirable low-density struc-ture.

The key, according to Jun and the other authors, is to use the inside of a grounded, curved dish—instead of the typical flat-plate collector—coupled with an array of electrospinning syring-es. Aptly, they have named this meth-od “FLUF,” their clever acronym for “focused, low-density, uncompressed nanofiber” mesh scaffold.

In a UAB news release, Bryan A. Blakeney, a recent graduate student and one of the authors is quoted as saying, “Our three-dimensional elec-trospun nanoscaffolds better mimic nature and encourage cells to live longer and generate more viable, or functional, tissues. Think of it like a bowl of rocks: You pour a liquid into the bowl, and the liquid fills all the large gaps between the rocks. But with our 3D nanoscaffold, our rocks, or the fibers that constitute the scaffold, are the size of sand particles. We’ve sepa-rated the grains of sand to create gaps, and the cells fill and penetrate the gaps between the sand grains to form tis-sues.”

In the paper, the group says they tested the performance of the FLUF ePCL material and report, “Cells seeded on the cotton-ball-like scaffold infiltrated into the scaffold after seven

days of growth, compared with no penetrating growth for the traditional electrospun scaffold. Quantitative analysis showed approximately a 40 percent higher growth rate for cells on the cotton-ball-like scaffold over a sev-en-day period, possibly because of the increased space for in-growth within the three-dimensional scaffolds.”

For ceramists, the good news is that the FLUF method is not limited to ePCL and should be suitable to those investigating the use of inorganic fibers for tissue engineering.

In addition to Jun and Blakeney, the authors include Ajay Tambralli, Joel M. Anderson, Adinarayana Andukuri, Dong-Jin Lim and Derrick R. Dean. n

ceramics in biomedicine

UAB group demonstrates techniques to electrospin improved 3D tissue engineering scaffolds

Figure (a) A traditional electrospun scaffold with a flat, two–dimensional structure with no depth for the traditional scaffolds. (b) A cotton-ball-like a Focused, Low density, Uncompressed nanoFiber (FLUF) scaffold shows with a fluffy, three–dimension-al structure of the scaffolds. (c) A cotton ball, which illustrates the relative shape and density of the electrospun nanofibers.

Innovations in Biomedical Materials 2012Sept. 10-13, 2012 | Hilton North Raleigh-Midtown, NC, USA

abstracts due april 2nd

MEDICALMATERIALS

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22 www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 3

th International Congress on Ceramics

July 15-19, 2012 | Sheraton Chicago Hotel & Towers | Chicago, Ill., USAwww.ceramics.org/icc4

th4 including 3rd Ceramic Leadership Summit Track

SIgn Up now To SAve $125.

3rd Ceramic Leadership Summit TrackA one-day program within ICC4, the CLS track explores entrepreneurship and the development of commercial products through directed R&D. It is all about business and technology leadership and connecting leaders within the community.

Shaping the Future of CeramicsBuilding on the success of ICC1’s (2006) “Global Roadmap,” ICC4 brings together more than 600 international leaders in business and research to discuss emerging opportunities that impact the future of ceramics and glass. This meeting focuses on innovations in: •Energy,EnvironmentandTransportation

•BiologyandMedicine

•Aerospace

•NanostructuredCeramics

•Infrastructure

•SecurityandStrategicMaterials

•Electronic,OpticalandMagneticCeramicsandDevices

•ManufacturingandBusiness

•EntrepreneurshipandTechnologyTransfer

•WorkforceDevelopment

Keynote SpeakerMaxine Savitz,GeneralManager(Retired),HoneywellInc.,andVice President,NationalAcademyofEngineering

Plenary SpeakersJohn Tracy,ChiefTechnologyOfficer,BoeingCo.

Athanasios Konstandopulous,ChairmanoftheBoard,Centrefor Research&TechnologyHellas,andDirector,ChemicalProcess EngineeringResearchInstitute

Michael Holman,ResearchDirector,LuxResearch

David S. Bem,GlobalR&DDirector,DowChemicalCo.

Yukio Sakabe,SeniorVicePresident(Retired),MurataManufac- turingCo.

Delbert Day,Curators’ProfessorEmeritusofMaterialsScienceand EngineeringandSeniorInvestigatoroftheGraduateCenterfor MaterialsResearch,MissouriUniversityofScienceandTechnology

Chi-Joon Choi,PresidentandCEO,LCRDivision,SamsungElectro- MechanicsCo.

Gary S. Calabrese,SeniorVicePresidentandDirector,Photovoltaic GlassTechnologies,CorningInc.

Savitz KonstandopulousTracy Holman SakabeBem Day CalabreseChoi

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23 www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 3

ICC4 features these invited speakers: AerospaceJohn Koenig, Southern Research InstituteGlenMandigo, US Advanced Ceramics AssociationToshihiroIshikawa, UBE Industries, Ltd.TakuyaAoki, Japanese Aerospace Exploration

Agency; Chofu Aerospace CenterJayE.Lane, Rolls-Royce Corp.AllanP.Katz, Air Force Research LabDilettaSciti, ISTECRhettJefferies, FAADanielLeiser, NASAJohn Thornton, DSTO, Air Vehicles Division

Biology and MedicineAshokKhandkar, BloXR, LLCMeinhardKuntz, CeramTec GmbHRichardP.Rusin, 3M ESPE Dental ProductsSerenaBest, University of CambridgeChristophe Chaput, 3DCeramEdgarZanotto, Universidade Federal de São Carlos

Electronic, Magnetic, Optical Ceramics and DevicesTakuyaAoki, TDK Technology GroupMichaelLanagan, Pennsylvania State UniversityJohnA.Rogers, University of Illinois at Urbana-

ChampaignAnkeWeidenkaff, EMPA - Swiss Federal Labora-

tories for Materials Testing and ResearchJürgenRödel, Technical University of Darmstadt

Environment, Energy and TransportationKrishan Luthra, GE Global ResearchYutai Katoh, Oak Ridge National LaboratoryRajendraNathBasu, CSIR-Central Glass and

Ceramic Research Institute

WolfgangRossner, Siemens AGS.K.Sundaram, Alfred UniversityAlan(Al)W.Weimer, University of ColoradoMinoruKanehira, Shanghai Institute of Ceramics,

CASJuanC.Nino, University of FloridaMasakiOzawa, Tokyo Institute of Technology,

Research Laboratory for Nuclear ReactorsHasanMandal, Sabancı UniversityManfredSalinger, Pall CorporationPaoloColombo, University of PadovaGeorgeMuntean, Pacific Northwest National

LaboratoryJamesJ.O’Brien, The Dow Chemical CompanyKoichiEguchi, Kyoto UniversityAlvaroMaiadaCosta, PetrobrasYujiIwamato, Nagoya Institute of TechnologyLouisWinnubst, University of TwenteLionelLemay, NRMCADoKyungKim, KAIST

InfrastructureHamlinJennings, Concrete Sustainability Hub, MITRobertMoon, US Forest ServiceLaurentBarcelo, Lafarge Canada, Inc.MariarosaRaimondo, CNR-ISTECToneyCummins, US Army Corps of EngineersAndreasTskebidis, BASFWilasaVichit-Vadakan, Siam Research and

Innovation Co. Ltd.

Nanostructured CeramicsSudiptaSeal, University of Central FloridaLynnetteMadsen, National Science FoundationKathleenK.Eggleson, University of Notre DameLang Tran, Institute of Occupational Medicine

DebraKaiser, Ceramics Division, Material Measurement Laboratory, NIST

JeffreyFagan, Polymers Division, NISTCharlesL.Geraci, NIOSHAngelaHightWalker, Physical Measurements

Laboratory, NISTDonEwert, nanoTox, Inc.

Security and Strategic MaterialsRichardA.Lowden, Oak Ridge National LaboratoryMarcHumphries, Congressional Research ServiceKohmeiHalada, National Institute for Materials

ScienceStanleyC.Woodson, US Army Corp of Engineers

Workforce DevelopmentAngusKingon, Brown University KeithJ.Bowman, Illinois Institute of TechnologyFumiyoKaneko, Japan Society for the Promotion

of Science, DC OfficeHongjieLuo, Shanghai Institute of CeramicsUmeshWaghmare, Jawaharlal Nehru Centre for

Advanced Scientific ResearchMarioAffatigato, Coe CollegeFedericoRosei, Université du QuébecJudithA.Todd, Pennsylvania State UniversityLouisMattosJr., The Coca-Cola CompanyJean-LucAdam, University of RennesPatrickBessler, Fraunhofer GesellschaftAngelaHohl-AbiChedid, PhilipsChristianneCorbett, American Association of

University WomenMaryLynnRealff, Georgia Institute of Technology

Emerging Topics in Ceramics ResearchGregRohrer, Carnegie Mellon University

www.ceramics.org/icc4SIgn Up now To SAve $125.

Tuesday, July 17, 2012

8:45 to 9:40 a.m. - ICC4 Plenary Lecture from Academia to Business, DelbertDay

10:00 a.m. to Noon - Technology Entrepreneurship – The Next Generation of Technology Transfer

Organizer: RichardWeber, Materials Development Inc.

Moderator: TimLavengood, Evanston Technology Innovation Center

Panel Members:•DelbertDay, MoSci Corp. - established glass and ceramics company•CollinAnderson, Digital Innovations - successful technology business•AlexArzoumanidis, Psylotech Inc. - early-stage technology business•JonathanGoodman, Synthesis Intellectual Property LLC - IP lawyer•LeslieMillar, University of Illinois Urbana-Champaign- technology transfer•JohnBanta, IllinoisVentures, LLC - seed and early-stage technology

investment firm

Noon to 1:30 p.m. - Lunch and ICC4 Plenary Lecture

1:40 to 3:40 p.m. - International Technology Transfer & Entrepreneurship Case Studies• Development and Commercialization of High-Performance Ceramics for Oil and Natural-Gas Recovery, JohnHellmann, Pennsylvania State University, United States• Thermoelectric Power Generation in Wide Temperature Region, RyojiFunahashi, National Institute of Advanced Industrial Science & Technology, Japan• TBD, Carmen Cerecedo, General Manager and CEO, Neoker S.L., Spain• From Technology Innovation to Industrialization: A Case of Ceramic Microbeads Based on Gel-Bead Forming, JinlongYang, Tsinghua University, China• Entrepreneurial Success of Balder LTD - Electro-optic Light Shutters for Eye- Protection, JanezPirs, Jozef Stefan Institute, Slovenia

3rd Ceramic Leadership Summit Track

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www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 324

High-temperature

oxide thermoelectrics

Scott Misture and Doreen Edwards

Conversion of waste heat to electrical

energy using oxide thermoelectric

generators might revolutionize the efficient

use of energy in the future.

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ture

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D irect conversion between thermal

and electrical energy using thermoelectric materials may revolutionize energy efficiency throughout mod-ern society. Capturing waste heat and converting it directly to electrical energy using thermoelectric genera-tors is one possibility, and the reverse possibility is

high-efficiency active cooling via the Peltier effect.

The TE effect occurs when a solid is exposed to a temperature gradient, which drives the dif-fusion of charge carriers—either electrons or holes—along the temperature gradient. The Seebeck coefficient (S), some-times called the thermoelectric power, is a material-specific measure of the resulting electri-cal potential. The Peltier effect describes how junctions of dis-similar materials can be heated or cooled depending on the direc-tion of current flow.

Connecting n- and p-type legs as shown in Figure 1 creates a TE module. TE modules are adaptable to many configurations, including thin-film forms, requiring only that the temperature gradient be maintained across the module. A key advantage of TE technologies is scalability, applications that

range from personal electronics to fixed power stations are envisioned.

A TE generator converts heat to electricity by the Seebeck effect when a voltage is created by a temperature difference across a solid. The overall efficiency of the device is captured by a dimensionless figure of merit (ZT), which depends on the materials’ Seebeck coefficient, electrical conduc-tivity (σ), thermal conductivity (k) and absolute temperature (T), according to

ZT = S2σT/k (1)TE materials with ZT ≈ 1 are consid-

ered high-performance materials with potential for commercial application.

Values as high as ZT ≈ 2.5 have been reported for nanostructured semicon-ductors near room temperature, 1–6 how-ever a general goal general goal of the TE research community is to reach ZT ≈ 3 for large-scale commercialization.

As with many technologies, the TE materials themselves limit the overall performance. The performance is linked to electrical and thermal conductivity. TE materials require minimal thermal transport and high electrical conductiv-ity with a large Seebeck coefficient. These requirements lead to the common description of the ideal TE material behaving as an “electron-crystal but phonon-glass,” where the electronic con-ductivity is large, as in a crystal, but the lattice thermal conductivity is small, as in an amorphous solid.

Nanoscale features, although largely crystalline, approach the glassy state in many respects.

Current understanding of phonon transport and electrical behavior points to the use of nanostructured “low-dimensional” solids, where 2D and even 1-D features may substantially increase ZT and decrease thermal conductivity. Notable progress has been made toward decreased lattice thermal conductivity via nanostructured composites, where phonon scattering at interfaces substan-tially decreases thermal conductivity. However, success in using quantum con-finement of charge carriers in nanofea-tures to increase ZT remains elusive.

Thus far, semiconducting materi-als have received the most attention, with materials like SiGe, PbTe and Yb14MnSb11 facilitating high ZT for n- and p-type TE elements. Extensive studies of bulk nanostructured solids clearly show that introducing nanoscale features into the solid is an effective means of decreasing the thermal con-ductivity and, thus, increasing ZT.

Because of the complex interplay between the electrical and thermal behaviors in TEs, other approaches have been used to probe their interre-lationships. For example, the use of 2D superlattice structures has been demon-strated as a means of filtering the low-energy charge carriers and as a means of decreasing thermal transport, where both effects work together to increase ZT.5,6

Figure 1. Schematic of a thermoelectric module.

c o v e r s t o r ybulletin

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25American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

Useful anisotropic properties from hybrid unit-cell structures

Ceramic TEs may allow a jump to higher service temperature regimes because of their stability at high tem-peratures in oxidizing and corrosive environments. The rich crystal chem-istry of oxides encourages strategies of multiscale nanostructuring by consid-ering “hybrid” crystal structures that contain discrete structural blocks or layers. Of course, nanostructuring these hybrid materials or assembling them as highly oriented polycrystalline solids or as composites also is envisioned. The size scales span from the unit-cell to the microscale.

At the unit-cell level, oxide crystal structures offer many options as hybrid structure types, including layered 2D structures and 1-D tunnel structures. With feature sizes less than five nano-meters, the crystallography may define structural features that support quan-tum confinement of charge carriers and disrupt or filter phonons, while

remaining thermodynamically stable during high-temperature operation. For example, in the layered oxides, dopants might be used in specific structural lay-ers. Likewise, there could be variations in layer thickness, interlayer strain and interfacial roughness to optimize ZT. Furthermore, 1-D and 2D structural features may facilitate decoupling of the electrical and thermal transport and offer the ability to exploit highly aniso-tropic properties.

At size scales larger than the unit-cell, nanoscale processing can help achieve desirable bulk structures, nanocomposites and superlattices, all of which remain largely unexplored in oxides. Functionally graded materials also are of interest, as are segmented n- or p-type legs that incorporate mul-tiple TE materials to optimize efficiency along the entire temperature gradient.

Several recent reviews1,5,6 demon-strate that many opportunities exist for the study of oxide TE materials. The layered or hybrid or “natural superlat-

tice” crystalline materials (Figure 2) are the primary oxide TEs thus far discov-ered, but there are several complex 3D or reduced oxides that also show high ZT. Mindful of the controversy related to inaccurate estimates of ZT, generally p-type oxides reach ZT = 1, while the

Figure 2. Layered thermoelectric struc-ture types: (a) p-type K0.5CoO2 (ideal-ized); and (b, c) two members of the Ruddlesden–Popper series, Sr2TiO4 and Sr3Ti2O7. The red polyhedra represent TiO6 units within the structure.

www.ceramics.org/phase

ORDER VERSION 3.3

PHASE EQUILIBRIA DIAGRAMS FOR CERAMIC SYSTEMS

Version 3.3 CD-ROM release includes 900 new fi gures with approximately 1400 new phase

diagrams and provides experimental and calculated data for an unprecedented range

of nonorganic material types.

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www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 326

n-type reach only about half that value at high temperature.

To achieve higher-temperature oper-ation, for example, Thot greater than 1000°C, oxide materials provide several key advantages:

• High-temperature chemical stabil-ity in oxidizing environments;

• Stable microstructures or nano-structures at elevated temperature; and

• Unusually low thermal conductivi-ty, as low as k ≈ 1 watt per meter∙kelvin at 1000°C, across planes in layered crystals at high temperatures.

Layered cobalt-based oxides are p-type conductors achieve ZT > 1 and achieve technologically relevant ZT values exceeding unity at temperatures up to 700°C. Example materials include AxCoO2 and Ca3Co4O9. In contrast, the n-type analogs suffer from low TE efficiency, although very recent reports of high ZT in n-type TEs are promis-ing. For example, the oxygen-deficient fluorite Ga3–xIn5+xSn2O16 has a ZT of approximately 0.3 at 1000 K, and the many variants of doped SrTiO3 have ZT up to approximately 0.4 at 1000 K.

Another class of active materials is highly reduced oxide ferroelectrics. Coupled ferroelectric–thermoelectric materials with oxygen deficiency have shown high-TE power factors and nanoscale features, a result of oxygen vacancy clustering on the size scale of 5–10 nanometers. Examples include the tungsten bronze SrxBa1–xNb2O6-δ and the layered Sr2Nb2O7.

2,7 Indeed,

there have been recent reports (thus far not yet reproduced) of oxide superlattices offering remarkable properties, with ZT = 2.4 estimated for the conducting layer in a SrTiO3/SrTiO3:Nb superlattice.1

The subtleties of the atomic arrangements have an enormous impact on the elec-tronic band structures and, therefore, on the thermopower in oxides. Recent work

has shown that distortions of the TiO6 octahedra in SrO(SrTiO3)n

Ruddlesden–Popper phases dominate the Seebeck coefficient.1 Crystal field splitting resulting from octahedral dis-tortions breaks the spin-orbital degen-eracy of the three titanium t2g orbitals at the bottom of the conduction band, decreasing the density of states, effec-tive mass and Seebeck coefficient. Even slight distortion of the octahedra by a few degrees is sufficient to dra-matically alter the Seebeck coefficient and ZT. For example, SrO(SrTiO3)2 with niobium doping and distorted octahedra has ZT = 0.14. Lanthanide doping, however, yields nearly perfect octahedra and ZT = 0.24. Furthermore, thermal expansion slightly decreases the octahedral distortions, thus improv-ing the Seebeck coefficient at higher temperatures.

A primary advantage of the layered oxides is unusually low thermal con-ductivity normal to the layers and, in some cases, parallel to the layers. For example, highly textured polycrystalline specimens of the ferroelectric materials Bi4Ti3O12 (Aurivillius structure) and Sr2Nb2O10 (SrnNbnO3n+2 homologous series) have k ≈ 1 watt per meter∙kelvin through 1000°C across the layers, which is nearly constant with tempera-ture. In the other two directions, ther-mal conductivity values are 1.5–2 watts per meter∙kelvin, also largely invariant with temperature. Even the in-plane values are substantially lower than

typical ceramics,8 and the cross-plane values are competitive with the state-of-the-art semiconducting materials.4,6

The unusual temperature inde-pendence raises new questions about the thermal transport mechanisms in these complex oxide structures. When phonon scattering from defects is con-sidered and the mean free path is esti-mated on the order of the interatomic spacing, the anisotropy in thermal conductivity is concluded to be attrib-utable to phonon scattering because of the acoustic mismatch between layers with substantially different density and thickness.

Although the 2D nature of layered oxides may be exploited to decrease the thermal conductivity in an anisotro-pic fashion, the necessity to maintain the electrical performance along the temperature gradient must also be con-sidered. Deliberate design of the atomic structures, nanostructures and micro-structures therefore requires knowledge of the anisotropy in the electrical and thermal properties.

Thermoelectric devicesOverall device efficiency depends

on optimum TE performance along the temperature gradient and matched properties of the n- and p-type legs, both of which are difficult to achieve. The thermal, thermoelectric and elec-trical properties are all functions of temperature, as shown schematically in Figure 3. The ZT values for oxide TEs may vary by a factor of 10 from room temperature to high temperature, with peak values generally at higher tem-peratures. In contrast to semiconduc-tors, the thermal conductivity decreases with temperature, generally by a factor of two or more, and it is typical for the thermal conductivity of bulk materials to reach values as low as 1–2 watts per meter∙kelvin at 800–1200°C.

Optimizing the device efficiency is possible using segmented TE materi-als along the temperature gradient or functionally graded materials that have properties optimized for maxi-mum ZT along the temperature gradi-ent. The overall TE device efficiency can be predicted, assuming matched

High-temperature oxide thermoelectrics

Figure 3. Schematic of the temperature dependence of the thermal and electrical conductivities and Seebeck coefficient as well as the resulting ZT.

ZT (d

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Temperature, K

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27American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

n- and p-type legs and temperature-independent ZT values with a hot side temperature of 727 K (1000°C).4 For a cold side of 300 K, an average ZT ~ 1 will yield 20-percent efficiency. Larger thermal gradients improve efficiency. Therefore, for a cold side of 100 K, 20-percent efficiency is achieved at ZT ≈ 0.8. Unfortunately, the assumption of temperature-independent ZT is not generally realistic, as shown in Figure 3. Therefore, oxide TE researchers need to address the opportunities and challeng-es of segmented or graded TE materials.

Designs for full TE modules may prove rather straightforward compared with some existing energy conversion technologies. The TE module has no moving parts and by necessity has only one end operating at elevated tempera-ture. There are challenges related to the stability of nanostructured materi-als, corrosion resistance, thermal expan-sion matching and electrode stability at the hot end, but these challenges appear to be manageable.

OutlookAdvances in oxide TEs, especially

n-type materials, may establish new benchmarks for device efficiency in the high-temperature regime. TE research-ers already are applying some of the knowledge gained in the study of semi-conducting TEs to the oxides.

Fundamental questions remain con-cerning the impacts of 1-D and 2D nanostructures on Seebeck coefficient and thermal conductivity, and oxides likely will provide the best platform for future, studies in heterogeneous 2D crystals. Synthetic heterostructures also may provide new experimental insights, and, of course, computational methods will grow in importance to broaden the knowledge base.

About the authorsScott Misture and Doreen Edwards

are professors at Alfred University. Contact: [email protected].

References1K. Koumoto, Y. Wang, R. Zhang, A. Kosuga and R. Funahashi, “Oxide Thermoelectric Materials: A Nanostructuring Approach,” Annu. Rev. Mater. Res., 40, 363–94 (2010).

2S. Lee, C. Randall, R.H.T. Wilke and S. Trolier-McKinstry, The Penn State Research Foundation, USA, 2010.3A.J. Minnich, M.S. Dresselhaus, Z.F. Ren and G. Chen, “Bulk Nanostructured Thermoelectric Materials: Current Research and Future Prospects,” Energy Environ. Sci., 2 , 466–79 (2009).4G.J. Snyder and E.S. Toberer, “Complex Thermoelectric Materials,” Nature Mater., 7, 105–14 (2008).5T. Kajitani, Y. Miyazaki, K. Hayashi, K. Yubuta, X.Y. Huang and W. Koshibae, “Thermoelectric Energy Conversion and Ceramic Thermoelectrics,” Mater. Sci. Forum, 671, 1–20 (2011).

6C.J. Vineis, A. Shakouri, A. Majumdar and M.G. Kanatzidis, “Nanostructured Thermoelectrics: Big Efficiency Gains from Small Features,” Adv. Mater., 22, 3970–80 (2010).7S. Lee, G. Yang, R.H.T. Wilke, S. Trolier-McKinstry and C.A. Randall, “Thermopower in Highly Reduced n-Type Ferroelectric and Related Perovskite Oxides and the Role of Heterogeneous Nonstoichiometry,” Phys. Rev. B: Condens. Matter Mater. Phys., 79, 134110/134111-134110/134118 (2009).8D.R. Clarke, “Materials Selection Guidelines for Low Thermal Conductivity Thermal Barrier Coatings,” Surf. Coat. Technol., 163–164, 67–74 (2003). n

REGISTRATION COMING SOON!

September 10-13, 2012 Hilton North Raleigh-Midtown, NC, USA

At the intersection of medical practitioners, materials researchers, manufacturers and marketers.

www.ceramics.org/biomaterials2012

Innovations in Biomedical Materials 2012

www.ceramics.org/biomaterials2012

September 10-13, 2012 Hilton North Raleigh-Midtown, NC, USA

At the intersection of medical practitioners, materials researchers, manufacturers and marketers.

Biomaterials 2012 will emphasize collaboration between R&D, medical practitioners, and biomedical materials manufactur-ers/marketers to better develop emerging technologies into marketable products.

– Uses of Bioactive Glass in New Treatments

– Blood Vessel and Nerve Guides

– 3D Scaffolds for Tissue Regeneration

– Malleable Bone Void Fillers

– Wound or Burn Treatment

– Surface Treatments and Coating of Titanium Implants

– Composites

– Sensors

– Biomedical Imaging

– Radiation Treatment

– Hemostasis and Blood Loss Control

MEDICALMATERIALS

Organized by: Endorsed by:

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www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 328

High efficiency nanobulk

thermoelectrics by bottom-up nano-crystal sculpting

and assembly

T hermoelectricity occurs through the coupling of thermal and elec-

tronic currents in dissimilar materials and can convert electrical energy into heat gradients and vice-versa.These complementary conver-sion processes are attractive for solid-state refrigeration and heating and for harvesting electricity from heat without using moving parts (Figures 1(a) and (b)).

The most important factor that determines the conversion efficiency is the thermoelectric figure of merit of the materials, defined as ZT = α2σT/k, where T is the absolute temperature, α the Seebeck coefficient, σ the electrical conductivity and k the thermal conductivity.Obtaining high-ZT materials is an exacting challenge, because k, α and σ are coupled unfavorably (Figure 1(c)).Moreover, different materials systems are required for applications in different temperature ranges. For example, at a given temperature, increasing σ also increases ke—the elec-tronic component of k—and decreases α.

The entailing compromises in materials design and selection have limited ZT in bulk materials to values typically between 0.5 and 1. The highest room-temperature ZT of approximately 1 has been for materials and alloys based on group V–VI com-pounds. Near-room-temperature conversion efficiencies have been low, with the maximum reported being about 8 percent. Consequently, the use of thermoelectric materials is restricted to niche and expensive consumer and defense applications. To expand the scope of thermoelectric applications, it is essential to reach energy conversion efficiencies greater than 15 percent by realizing room- and high-temperature ZT greater than 2.1

Semiconductors offer promise for obtaining high ZT, because—unlike metals that have high σ but high k and low α, and insulators that have very low σ—they offer a good balance of the three properties that are tunable by bandgap engineering and nanostructuring (Figure 1(c)). For example, the phononic thermal conductivity kL decreases with nanostructuring without severely degrading σ that is coupled mainly to the electronic component ke.

Rutvik J. Mehta and Ganpati Ramanath

Bottom-up synthesis through nanostructuring and dop-

ing—which are compatible with the conventional tools

of alloying, compositional control and texturing—holds

promise for realizing nanobulk thermoelectric materials

with ZT values greater than 2.

Figure 1. Schematic thermoelectric devices operating as a solid-state a) power generator and b) cooler. Both n- and p-type thermoelectric materials are required and their qual-ity determines the device performance. c) Graph shows unfavorable coupling between the thermoelectric properties with carrier concentration.

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29American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

Alloying and grain refinement are two broad approaches that have been pursued to increase ZT. Alloying addi-tions of several atomic percent is a well-known method to decrease kL via increased phonon scattering. Recently, there has been a renaissance in the use of sub- to few-atomic-percent doping additions to increase α by effecting changes in the band structure near the Fermi level2,3 that do not significantly decrease σ. A classic example is alloy-ing Bi2Te3 with p-type Sb2Te3 or n-type Bi2Se3 to achieve near-room-tempera-ture ZT of approximately 1.

Theoretical calculations predict that nanostructuring-induced quantum effects can decouple α and σ to yield ZT of 2 to 10. However, it is now well recognized that kL suppression is the main ZT enhancement mechanism in nanostructured materials. For example, ZT of about 2.4 has been obtained in Bi2Te3/Sb2Te3 thin-film multilayers.1 Transmuting such findings to scalable and cost-effective synthesis of high-ZT bulk materials is a major challenge in materials design and processing, but is being addressed. For example, nanostructured bulk (nanobulk) p-type Bi0.5Sb1.5Te3 thermoelectrics with room-temperature ZT of 1.1 to 1.2 have been obtained by compacting powders obtained by high-energy ball milling.4 Although this amounts to 40–50-per-cent ZT enhancement, this process is difficult to apply to high-ZT n-type materials.

Furthermore, such reductive processes limit the ability to control nanostruc-ture size, shape and composition. For example, achieving nanoparticle sizes less than about 100 nanometers is chal-lenging, and the particle shape is usually irregular. In contrast, bottom-up chemi-cal synthesis allows controllable sculpt-ing of the shape, size and composition of nanoscale building blocks, which are the primary units for fabricating nano-bulk thermoelectrics (Figure 2).

Nanobulk V–VI semiconductorsWe can accomplish nanocrystal syn-

thesis for thermoelectric chalcogenides by many wet-chemistry techniques, such as solvothermal,5 hydrothermal,6

polyol,5 microemulsion7 and autoclave methods, besides electrochemical and vapor-based deposition nanocrystal growth techniques. The wet-chemical techniques (Figure 2(a)) yield a variety of morphologies shown in Figures 2(b)–(d), such as single-crystal nanorods,6 nanoparticles,7 nanopolyhedra8 and core–shell telluride/sulfide nanowires,9 depending on the surfactant type and synthesis parameters. Although these techniques provide a rich toolset to sculpt nanostructures, they are not well suited for producing bulk quantities of the material. In particular, the synthesis times range from a few hours to days, and they typically yield only milligrams of materials that need handling in oxygen-free environments.

A recently devised rapid, scalable microwave-stimulated solvothermal synthesis technique, shown in Figure 3, uses organic surfactants with chosen terminal moieties and obviates many of the aforementioned shortcom-ings.5,10–12 The surfactant molecule mediates the reactions between metal-organic precursors in high-boiling-point polyol-based solvents during microwave heating to produce multigram-scale nanocrystals in a few minutes at near-100-percent yields. The surfactants serve as nanostructure sizing and shaping agents. They inhibit oxida-tion by passivating the nanostructure surfaces (Figure 2(e)), which facilitates the handling and long-term storage of the nanopowders and eliminates expensive oxygen-free processing tools. Implementing this approach of

synthesizing nanobulk materials from nanocrystals, to materials that exhibit high ZT in the non-nanostructured form—e.g., V–VI pnictogen chalco-genides—offers scope for further ZT enhancements.

Nanoplates of V–VI compounds with desired composition, doping, aspect ratio and crystal structure are synthe-sized by choosing appropriate surfac-tant–precursor combinations, and size is tuned by adjusting the microwave dose. Low doses produce smaller nanocrystals, which yield smaller grains and, hence, lower kL in nanocrystal assemblies.

Shape also is controllable by micro-wave dose, as demonstrated by the tunable conversion of chalcogenide nanowires to nanotubes through void nucleation and growth12 driven by sul-fur rejection from a supersaturated solid solution. Shape control is attractive for potentially harvesting anisotropic carrier mobilities, μ, and, hence, σ, e.g., by growing the nanostructures in certain crystallographic orientations (anisotropic growth and branching in Figure 2(e)). For example, nanoplates or nanowires of Bi2Te3 with preferred growth direction along the high μ [1120] , may help combine high σ with nano-induced low k.

Moreover, surfactants can provide a knob to tune α and σ through con-trol of the majority carrier type and concentration by perturbing the defect chemistry and electronic structure through adsorption and dopant atom injection (Figure 2(e)). For instance, sub-atomic-percent sulfur doping from

Figure 2. Wet chemistry (a) is used to make nanoscale constituents (b-d), which are assembled into bulk materials. Color-enhanced SEM micrographs show different shapes and sizes of bismuth telluride nanostructures (scale bar lengths in parentheses): (b) nanopolyhedra8 (200 nm), (c) branched core-shell telluride-sulfide nanowires9 (200 nm), and (d) nanoplates5 (100 nm). The illustration (e) shows the multiple roles of the organic surfactants for sculpting nanocrystals.

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mercaptan-terminated surfactants can convert p-type stoichiometric Bi2Te3 to n-type materials,5 and can offset at least some of α2σ factor degradation that often accompanies nanostructuring-induced kL reduction. Thus, combining nanostructuring with doping is a power-ful approach to increase ZT.

Nanobulk V-VI materials fabricated by cold-compaction and sintering of the nanocrystals exhibit 25–250-percent-higher ZT than their non-nanostruc-tured counterparts and state-of-the-art alloys (Figure 3).5 One unique aspect of microwave-stimulated bottom-up syn-thesis is that, even without optimization, p- and n-type nanomaterials with room-temperature ZT greater than or equal to 1 can be fabricated. Single-component as well as multicomponent nanobulks are made from mixtures with preselected volume fractions of nanostructures of different V–VI compounds. Unlike the non-nanostructured counterparts of V–VI compounds, where4 ZT is less than 0.5 at T greater than about 350 K, the ZT of the nanobulk materials peaks at about 1.2 in the 325–380 K range, conducive for harvesting low-grade waste heat. For instance, in sulfur-doped nano-bulk p-type Sb2Te3, the ZT increases

monotonically to ZT equal to about 1 at 420 K, rather than decreasing to ZT less than 0.5 as seen in conventional materi-als, pointing to the effects of doping and temperature on carrier concentration.5

The high ZT results from a combination of low kL and doping-induced retention of high α and σ. Nanostructuring leads to 0.2 < kL ≤ 0.6 watt per meter∙kelvin, which is 40–75-percent lower kL than the non-nanostructured counterparts (Figure 4(a)–(c)).5 These kL values are close to the lower theoretical limit and are caused by phonon scattering by bound-aries of 25–50-nanometer nanograins and nanopores (Figures 4(a) and (b)). Although the nanobulks exhibit a low kL that is about twofold lower than that of silica, a thermal insulator, the elec-trical conductivity is high, 30 ≤ σ ≤ 250 kilosiemens per meter (Figure 4(c)). Such electrically conducting and ther-mally insulating materials are the quint-essential thermoelectric archetypes, referred to as phonon-glass electron-crystals (Figures 4(c) and (d)). The high σ in our nanobulk materials with a high density of interfaces is indeed surprising. It is thought to result from single-crystal-like charge carrier mobili-

ties of μ about equal to 60–350 square centimeters per volt∙second, control over the majority carrier type achieved through sulfur doping and surfactant-passivation-induced oxidation suppres-sion.5 The absence of organic residues that can degrade σ suggests that the surfactants desorb during sintering.7

Sub-atomic-percent sulfur doping leads to high α of –240 ≤ α ≤ 300 microvilts per kelvin for p- and n-type materials, and we can fine-tune them by controlling the carrier concentration (Figure 4(e)).5 The ability to manipu-late α is key for obtaining high ZT because of the quadratic dependence of the latter on the former. Seebeck coef-ficient is a difficult property to control, because it represents the entropy of charge carriers near the Fermi level and is related to the difference in the aver-age hot-carrier energy and the Fermi energy. Hence, it involves tailoring the density of electronic states near the Fermi level.

Besides doping, creating metal–semi-conductor interfaces by hot-carrier filtering13 is another way to increase α. Indeed, heterostructuring pnictogen tel-luride nanoplate crystals with tellurium precipitates11 increases α by 50 percent (Figure 5(a)). One way to achieve het-erostructuring in pnictogen chalcogen-ides is use of precursors that promote the stabilization of multiple oxidation states of the chalcogen during synthe-sis. For example, stabilizing Te2– states promotes formation of bismuth and antimony tellurides, whereas precursors in Te6+ states lead to a reduction to Te0, forming tellurium metal (Figures 5(f) and (g)).11 We can tune the dimensions, extent, shape and density of the heterostructures by simply alter-ing the surfactant concentrations and surfactant–precursor ratios, as shown for Bi2Te3 and Sb2Te3 nanoplates decorated with tellurium nanowires or nanofins.11 The combination of high α and σ through sulfur doping and heterostruc-turing allows the design and processing of novel nanobulk thermoelectrics.

Nanobulk doped oxidesThe bottom-up approach of nano-

structuring and doping applies to other

High efficiency nanobulk thermoelectrics by bottom-up nanocrystal sculpting and assembly

Figure 3. Microwave-based, scalable synthesis used to obtain both n- and p-type high ZT bulk thermoelectric nanomaterials. Rapid microwave synthesis of sulfur-doped nano-plates followed by cold-compaction and sintering yields nanobulk materials. Sulfur doping controls the σ, α and the majority carrier type, while nanostructuring results in very low kL in V-VI alloys. The bar graph compares ZT of our best nanobulk thermoelec-tric materials with the highest ZT non-nanostructured bulk materials (p- or n-Bulk) and nanoparticle-dispersed bulk referred (n-Nano) and a p-type ball milled alloy10 (p-Nano).

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materials systems, such as oxides, that are attractive for high-temperature thermoelectric conversion applications (Figure 6(a)). Zinc oxide is a promising low-cost, high-melting-point mate-rial with high σ and α, but it is lim-ited14 by a high kL of about 5 watts per meter∙kelvin at 1273 K and about 50 watts per meter∙kelvin at 300 K. Non-nanostructured ZnO doped with one or more group III elements15 exhibits 0.4 ≤ ZT ≤ 0.65 at about 1273 K. It is limited to values less than 1 by the relatively large kL. Thus, systems like ZnO are amenable to large ZT enhancements by our approach of nanostructuring and doping, which—together—leads to 50-percent-higher ZT than non-nano-structured10 ZnO because of 20-fold kL decrease while maintaining high α2σ.

We can use the microwave synthesis method described earlier to produce 5–10-nanometer ZnO wurtzite nano-crystals with 0.5 to 2-atomic-percent doping of aluminum, indium or bismuth (Figure 6(a)). The nature and amount of doping strongly influence nanocrystal shape and size. For example, aluminum doping increases the nanocrystal aspect ratio, likely through doping-mediated oxygen stoichiometry changes on select crystal planes. Nanobulk pellets fabricated from the nanocrystals lead to manifold decreases in kL (Figure 6(a)). For example, our undoped nanobulk ZnO shows sevenfold lower room-temperature kL (about 7 watts per meter∙kelvin) compared with non-nanostructured ZnO (Figure 6(b)) because of the former’s average approxi-mately 100-nanometer grain size.

Additionally, unlike the chalcogen-ides, the dopants in ZnO affect α and σ and the nanobulk microstructure and, hence, kL (Figure 6(b)). For example, increasing aluminum-doping levels results in increased phonon scatter-ing, smaller nanocrystals and grain-growth suppression in the nanocrystal assemblies, leading to an additional about fivefold kL diminution over pure nanobulk ZnO, yielding ultralow10 kL of about 1.6–2 watts per meter kelvin (Figure 6(b)). This is supported by about 30–35-percent-smaller grain sizes in aluminum-doped nanobulk

ZnO than that in undoped nano-bulk ZnO, and the presence of about 50–200-nanometer ZnAl2O4 spinel precipitates in the former. However, nanobulk bismuth-doped ZnO pellets fabricated by this approach exhibit larger ZnO nanograins separated by bismuth oxide at the grain boundaries. This results in higher kL than alumi-num-doped nanobulk ZnO, but which has considerably smaller kL than the non-nanostructured materials (Figure 6(b)). These results imply that dopants can alter the microstructure and phase compositions of the nanobulk assem-blies and that aluminum is effective for kL reduction by contributing to small crystal sizes during synthesis and grain refinement during sintering.

Besides diminished kL, the doped

nanobulk ZnO pellets exhibit high room-temperature α in the –300 < α < –200 microvolt per kelvin range together with high σ of about 1–1000 Siemens per meter. These values are comparable to, or higher than, those observed in comparatively doped non-nanostructured ZnO, underscoring the importance and power of combin-ing nanostructuring and doping.10, 14 The enhanced σ results from doping-induced donor states at about 50–250 milli-electron-volts below the conduc-tion band edge in addition to bandgap increase of up to 0.3 electron-volt because of Burstein–Moss and quantum effects.11 Although the doping-induced carrier injection results in high σ, sub-degenerate carrier concentrations favor high α.

Figure 4. (a) Nanobulk bismuth telluride assembled from nanoplates with about 50–200-nanometer grains with grains averaging 30 nanometers and nanopores averag-ing 25 nanometers (red arrows in TEM micrographs). (b) Comparing phononic thermal conductivity of nanobulk Bi2Te3 and non-nanostructured material affected by multiple operative phonon-scattering mechanisms. Mixing Bi2Te3 with Sb2Te3 nanoplates causes phonon scattering on antimony atoms, further lowering kL. (c) Thermal and electrical conductivity of nanobulk Bi2Te3 and Sb2Te3 compared with non-nanostructured material and silica glass. (d) Phonon-glass electron-crystals. Arrows show conduction pathways of mobile electrons but severely hindered phonons. (e) Sulfur-doping of nanostructured Bi2Te3 (inset) results in a larger α than the undoped case.

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High efficiency nanobulk thermoelectrics by bottom-up nanocrystal sculpting and assembly

A unique feature of our alumi-num- and indium-doped nanobulk ZnO is that σ and α show a mono-tonic increase with increasing tem-perature (Figure 6(c)), in contrast to the behavior of non-nanostructured counterparts.10,15 Although the exact mechanism for this behavior is not fully understood, the subdegenerate carrier concentration and/or nanostructuring-

induced electronic structure changes likely are a cause. Because α and σ increase simultaneously with decreasing kL, the ZT increases with temperature, and an almost 50-percent enhance-ment in the ZT above 800 K10 has been observed. These results are of interest for realizing high-ZT thermoelectrics at temperatures of interest for power-harvesting applications (Figure 7).

Future directionsCombining doping and nanostructur-

ing by bottom-up nanocrystal synthesis and assembly is attractive for obtaining bulk thermoelectric materials with high ZT (Figure 7). The approach is versatile and applicable to V–VI semiconductors as well as oxide systems, and we can adapt other thermoelectric materials systems, such as lead-based chalcogen-ides, metal silicides and antimonides for broadening the materials toolkit for a wide range of thermoelectric applica-tions.

Further improvements in ZT might be achieved by custom-designing the shape, size and chemistry of nanoscale building blocks and implementing novel nanostructure assembly and fabrication processes. For example, in addition to obtaining isotropic proper-ties, introducing texture in nanocrystal assemblies through novel chemical synthesis and consolidation processes, such as extrusion and slip casting might offer new possibilities for maximizing anisotropic thermoelectric transport properties.

Exploiting inherent shape anisot-ropy of nanostructures through bulk selective assembly of oriented nano-structures, e.g., stacking of nanoplates through chemically directed assembly methods, also might offer some interest-ing avenues for optimizing properties. For example, engineering a [1120] texture along the heat-flow direction in a Bi2Te3 nanobulk, would realize direction-specific high power factor, typically threefold to sevenfold higher than is seen for the [0001] direction or for polycrystals. The k[1120]/k k[0001] anisotropy is smaller—typically about 2 to 3 times—and we can diminished it by nanostructuring. Effectively, design-ing texture in nanobulk heralds ZT greater than 1.5.

Another avenue to explore is the use of gradients of dopant levels and com-positions together with nanograin-sized gradients. For example, composing the nanobulk material through serial and parallel mixing of nanoplate powders of various sizes, compositions and doping levels might foster new device designs and temperature-dependent proper-

Figure 5. Tuning Seebeck coefficient through nanoheterostructuring. Seebeck voltage plotted as a function of the temperature gradient ΔT across thin-film assemblies of (a) Bi2Te3 nanoplates, (b) Bi2Te3–Te heterostructures, (c) Sb2Te3 nanoplates, (d) Sb2Te3–Te nanofin heterostructures and (e) Sb2Te3–Te nanorod heterostructures. For each sample, the Seebeck coefficient and a representative electron micrograph are shown. (f, g) The tellurium oxidation state controls heterostructuring of Bi2Te3 nanoplates with tellurium nanocrystals.

Figure 6. (a) High-ZT zinc oxide made by cold-pressing and sintering of aluminum-doped ZnO nanocrystals made by microwave-synthesis, yielding a 20-fold lower thermal con-ductivity than non-nanostructured Al-ZnO. Aluminum doping causes retention of bulk-like power factors (α2σ). (b) Thermal conductivity of nanobulk ZnO as a function of doping and associated SEM micrographs. Bright boundary regions are bismuth oxide and bright particles are ZnAl2O4 nanoprecipitates. The inset is a transmission electron micrograph showing nanosized intragranular grains (scale bar is 200 nanometers). (c) Seebeck coef-ficient and electrical conductivity of 0.25-atomic-percent aluminum-doped nanobulk ZnO as a function of temperature.

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ties. In addition, nanopore size, shape, fraction and distribution can be engi-neered by altering nanocrystal assembly processing parameters and sintering time–temperature cycles to manipulate kL to increase ZT (because nanopores below certain sizes have been shown to sustain high σ).5 Finally, the implemen-tation of nanostructuring together with doping on ternary and quaternary alloys of suitable compositions and expanding the dopant candidates, is an attractive means to detangle the unfavorable cou-pling between α, σ and k to realize bulk nanomaterials with ZT greater than 2.

About the authorsRutvik J. Mehta is a post-doctoral

researcher at the department of materials science and engineering at Rensselaer Polytechnic Institute. Ganpati Ramanath is professor of materials science and engineering at Rensselaer Polytechnic Institute. They cofounded ThermoAura Inc., a nano-tech start-up focusing scalable nano-crystal manufacturing to realize novel high ZT thermoelectric materials for transformative applications. Contact: [email protected]

References1R. Venkatasubramanian, E. Siivola, T. Colpitts and B. O’Quinn, “Thin-Film Thermoelectric Devices with High Room-Temperature Figures of Merit,” Nature, 413, 597–602 (2001).2Y.Z. Pei, X.Y. Shi, A. LaLonde, H. Wang, L.D. Chen and G.J. Snyder, “Convergence of Electronic Bands for High-Performance Bulk Thermoelectrics,” Nature, 473, 66–69 (2011).3J.P. Heremans, V. Jovovic, E.S. Toberer, A. Saramat, K. Kurosaki, A. Charoenphakdee, S. Yamanaka and G.J. Snyder, “Enhancement of Thermoelectric Efficiency in PbTe by Distortion of the Electronic Density of States,” Science, 321, 554–57 (2008).4B. Poudel, Q. Hao, Y. Ma, Y.C. Lan, A. Minnich, B. Yu, X. Yan, D.Z. Wang, A. Muto, D. Vashaee, X.Y. Chen, J.M. Liu, M.S. Dresselhaus, G. Chen and Z. Ren, “High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys,” Science, 320, 634–38 (2008).

5R.J. Mehta, Y. Zhang, C. Karthik, B. Singh, R.W. Siegel, T. Borca-Tasciuc and G. Ramanath, “A New Class of Doped Nanobulk High-Figure-of-Merit Thermoelectrics by Scalable Bottom-Up Assembly,” Nat. Mater., 11, 233–40 (2012).6A. Purkayastha, F. Lupo, S. Kim, T. Borca-Tasciuc and G. Ramanath, “Low-Temperature, Template-Free Synthesis of Single-Crystal Bismuth Telluride Nanorods,” Adv. Mater., 18, 496–500 (2006).7A. Purkayastha, S. Kim, D.D. Gandhi, P.G. Ganesan, T. Borca-Tasciuc and G. Ramanath, “Molecularly Protected Bismuth Telluride Nanoparticles: Microemulsion Synthesis and Thermoelectric Transport Properties,” Adv. Mater., 18, 2958–63 (2006).8A. Purkayastha, A. Jain, C. Hapenciuc, R. Buckley, B. Singh, C. Karthik, R.J. Mehta, T. Borca-Tasciuc and G. Ramanath, “Synthesis and Thermoelectric Properties of Thin Film Assemblies of Bismuth Telluride Nanopolyhedra,” Chem. Mater., 23, 3029–31 (2011).9A. Purkayastha, Q.Y. Yan, M.S. Raghuveer, D.D. Gandhi, H.F. Li, Z.W. Liu, R.V. Ramanujan, T. Borca-Tasciuc and G. Ramanath, “Surfactant-Directed Synthesis of Branched Bismuth Telluride/Sulfide Core/Shell Nanorods,” Adv. Mater., 20, 2679–83 (2008).10P. Jood, R.J. Mehta, Y.L. Zhang, G. Peleckis, X.L. Wang, R.W. Siegel, T. Borca-Tasciuc, S.X. Dou and G. Ramanath,

“Al-Doped Zinc Oxide Nanocomposites with Enhanced Thermoelectric Properties,” Nano Lett., 11, 4337–42 (2011).11R.J. Mehta, C. Karthik, B. Singh, R. Teki, T. Borca-Tasciuc and G. Ramanath, “Seebeck Tuning in Chalcogenide Nanoplate Assemblies by Nanoscale Heterostructuring,” ACS Nano, 4, 5055–60 (2010).12R.J. Mehta, C. Karthik, W. Jiang, B. Singh, Y.F. Shi, R.W. Siegel, T. Borca-Tasciuc and G. Ramanath, “High Electrical Conductivity Antimony Selenide Nanocrystals and Assemblies,” Nano Lett., 10, 4417–22 (2010).13D. Vashaee and A. Shakouri, “Improved Thermoelectric Power Factor in Metal-Based Superlattices,” Phys. Rev. Lett., 92, 106103 (2004).14K.P. Ong, D.J. Singh and P. Wu, “Analysis of the Thermoelectric Properties of n-Type ZnO,” Phys. Rev. B, 83, 115110 (2011).15T. Tsubota, M. Ohtaki, K. Eguchi and H. Arai, “Thermoelectric Properties of Al-Doped ZnO as a Promising Oxide Material for High-Temperature Thermoelectric Conversion,” J. Mater. Chem., 7, 85–90 (1997).16X.B. Zhao, X.H. Ji, Y.H. Zhang, T.J. Zhu, J.P. Tu and X.B. Zhang, “Bismuth Telluride Nanotubes and the Effects on the Thermoelectric Properties of Nanotube-Containing Nanocomposites,” Appl. Phys. Lett., 86, 062111 (2005). n

Figure 7. Summary of the factorial ZT enhancements demonstrated in multiple systems for n- and p-type materials for room-temperature cooling and high-temperature power-generation applications by the microwave-based bottom-up route. The ZT values of the corresponding bulk material of same composition are indicated by the lines for compari-son.

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Modeling thermoelectric materials and

devices

T he thermo-electric effect,

a conversion between thermal and electrical energy, was discovered in the early part of the 19th century. It is the basis for how a thermocouple mea-sures temperature and has been used in niche appli-cations for refrigeration and power generation since the 1950s.

Thermoelectric devices have the advantage of containing no moving parts, making them quiet, durable and reliable. It is only recently that advances in materials development, theory and computational tools have suggested that thermoelectric devic-es can compete with traditional refrigeration and power generation technologies.1–5

Modeling and simulation have an important role in the development of materials and devices for thermo-electric energy conversion applica-tions. Atomistic modeling tools (e.g., density functional theory calculations and molecular dynamics simulations) provide strategies for the design of nanostructured materials and help to elucidate the underlying physical

phenomena. Continuum modeling at the device-scale, using thermody-namic cycles, heat transfer analysis and finite-element method calcula-tions, is critical for optimizing the integration of thermoelectric materi-als with devices and for predicting how these devices will interact with their environment.

Thermodynamic cycle and device-level energy balance

A thermoelectric device can be used for refrigeration or for power generation. The schematic dia-gram in Figure 1(a) shows that, in refrigeration, electrical power is sup-plied and thermal energy is moved from a cold sink to a hot sink. The device performance is quantified by the coefficient of performance, defined as the thermal load taken from the cold sink divided by the work input. Figure 1(a) shows that, for power generation, heat transfer from a hot sink to a cold sink pro-duces electrical power. The device performance is quantified by its efficiency, defined as the generated power divided by the thermal load from the hot sink. The maximum COP (coefficient of performance) or efficiency is set by the Carnot limit, TC/(TH–TC). It is a function of the temperatures of the hot and cold sinks, as shown in Figure 1(b).

The remainder of this article dis-cusses thermoelectric refrigeration.

Alan McGaughey

Recent advances in modeling and simula-

tion suggest thermoelectric devices can be

competitive with existing refrigeration and

power generation technologies.

in with . . .

Out with the old . . .

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The modeling tools and techniques dis-cussed, however, are equally applicable to power generation.

A specific definition of a thermo-electric refrigerator starts by considering the single thermoelectric module shown in Figure 2. The module consists of two legs, made from different thermo-electric materials, one n-type and one p-type. The legs are connected in series electrically through metal contacts but are in a parallel arrangement from the standpoint of heat transfer between the hot and cold sinks. In a real device, hundreds of thermoelectric modules are electrically connected in series.

An expression for the maximum COP based on the electrical and thermal properties of the legs can be obtained by performing an energy bal-ance on the module.6 In the thermo-electric refrigerator, a voltage is applied across the module, leading to the flow of electrical current. Two separate energy conversion mechanisms develop. First, there is Peltier cooling at the cold junction (leading to the absorption of energy from the cold sink) and Peltier heating at the hot junction (leading to the release of energy to the hot sink). The magnitudes of the heating and cooling are given by (Sp – Sn)IT = SIT, where Sp and Sn are the Seebeck coef-ficients of the p- and n-type materials, respectively, I the current and T the junction temperature. The Seebeck coefficient is a temperature-dependent material property that describes the voltage induced in a material in the presence of a temperature gradient. It is

positive for a p-type material and nega-tive for an n-type material.

The current flow leads to Joule heat-ing as well as the desired Peltier heating and cooling in the legs. Joule heating is undesirable, because it adds to the heat load at the cold junction, which the Peltier cooling must remove. The strength of the Joule heating is related to the current flow and to the electrical conductivities (σ) of the thermoelectric materials, which will be taken to be same for the n- and p-type materials in this analysis.

The temperature difference between the hot and cold sinks leads to parasitic heat conduction through the legs and an additional, undesirable, heat load at the cold junction. The magnitude of the heat conduction is related to the ther-mal conductivity (k) of the legs, which will be taken to be the same for the n- and p-type materials in this analysis.

An expression is obtained for the COP in terms of the materials proper-ties, leg geometries, temperatures of the hot and cold sinks and the electrical current by performing an energy bal-ance at the hot and cold junctions, including the thermal loads, Peltier heating and cooling, Joule heating and thermal conduction. Increased current leads to increased Peltier heating and cooling (desirable) but also to increased Joule heating (undesirable). There is an optimal current flow that leads to a maximum COP, given by

COP = [TC/(TH – TC)] {[(1 + ZT)1/2 – (TH/TC)]/[(1 + ZT)1/2 + 1]} (1)

This expression for the maximum COP contains the dimensionless parameter ZT, defined by

ZT = (S2σ/k)[(TH + TC)/2] (2)

which is the thermoelectric figure of merit. The product S2σ in the numera-tor is called the power factor. Although there is no theoretical limit to ZT, the COP approaches the Carnot limit, TC /(TH – TC), as ZT approaches infin-ity, as shown in Figure 1(b).

The minds of thousands of scientists and engineers during the past 60 years have been occupied devising schemes for maximizing ZT by manipulating the Seebeck coefficient, electrical con-ductivity and thermal conductivity. However, device-level modeling needs to be addressed before discussing how ZT can be predicted from theory and of the strategies that have emerged for increasing ZT.

The model described by equations (1) and (2) is a simplification of a real device. Issues which need to be con-sidered that make the maximum COP impossible for real devices to achieve.

• First, it is difficult to find n- and p-type materials with the same electri-cal and thermal conductivities (an assumption in the expression for maxi-mum COP).

Figure 1. (a) Thermodynamic cycles for refrigeration and power generation. In a ther-moelectric refrigerator, work input as electrical power allows for heat removal from a cold sink. In a thermoelectric generator, heat transfer from a hot sink produces an electrical potential. (b) Coefficient of performance for a refrigerator operating at room temperature.

Figure 2. Schematic diagram of a single thermoelectric refrigerator module. The hot and cold junctions are electrically insu-lating. This module comprises the detail that is the oval marked “Refrigerator” in Figure 1(a).

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• Second, the electrical contact resistances at material interfaces (e.g., between the thermoelectric legs and the metal contacts, and between the hot and cold sinks and the thermoelec-tric device) lead to a smaller current flow for a given applied voltage. At the same time, thermal contact resis-tances at these interfaces benefit the system by decreasing the parasitic heat conduction losses. Interfacial effects become more important as thermoelec-tric devices are decreased to millimeter scales and below.

• Third, heat transfer to the device—which typically will be oper-ated at temperatures below ambient conditions—by radiation and convec-tion from the surroundings, increases the thermal load at the cold junction and negatively affects performance.

• Fourth, in the presence of a poten-tially large temperature difference, all material properties become temperature (and, thus, location) dependent.

These factors affect the device per-formance by changing the optimal current at which the device should be operated and decreasing the COP that can be realized.

These effects cannot be included accurately in a simple analytical model, and require more detailed modeling using numerical techniques, such as finite-element analysis. Although sig-nificantly more costly than analytical models from a computational perspec-tive, finite-element studies provide an important link between modeling and performance of real devices.

Predicting TE propertiesThe following section explains how

researchers are using modeling to pre-dict the three relevant materials prop-erties–electric conductivity, Seebeck coefficient and thermal conductivity–and how modeling facilities strategies for maximizing ZT.

Electrical conductivity describes how easy it is for electrons to move through a material. Qualitatively, the electrical conductivity is related to the material’s Fermi level, which indicates the energy of the highest occupied elec-tron state. In metals, where the Fermi

level lies in the conduction band, there are free electrons, and the electrical conductivity is high (approximately 107 siemens per meter). In an undoped semiconductor, where the Fermi level lies between the valence band and the conduction band, the electrons are tightly bound to the atomic nuclei, and the electrical conductivity is very low (much less than 1 siemen per meter). In doped semiconductors—the materials typically used in thermoelectric energy conversion applications—the electrical conductivity can be made close to that of metals.

The Seebeck coefficient describes the relationship between an applied voltage and the induced temperature difference (or vice-versa). The Seebeck coefficient also is related to the mate-rial’s Fermi level. The magnitude of the Seebeck coefficient is approximately 10 microvolts per kelvin for metals and approximately 100–500 microvolts per kelvin for doped semiconductors (positive for p-type and negative for n-type). Recall from the device-level discussion that the difference between the Seebeck coefficients of the p- and n-type materials to calculate the ther-moelectric figure of merit ZT.

Thermal conductivity describes how easy it is for thermal energy to transfer through a material by conduction. For solids at room temperature, thermal conductivity varies from about 0.01 watts per meter kelvin for aerogels to a few thousand watts per meter kelvin for carbon nanotubes and graphene. Glass has a room-temperature thermal conductivity of 1.4 watts per meter kelvin and silicon, 140 watts per meter kelvin. Thermal conduction in a solid results from the transport of electrons (kelectron), which dominate in metals, and phonons (kphonon), which dominate in semiconductors and dielectrics. A phonon is a quasi particle (it has no mass) that carries energy waves gener-ated by the vibrations of the atoms. Like a water wave, which carries energy while imparting no net displacement to the individual molecules, a phonon carries energy through a solid with no net mass transfer. Because it is a wave, a phonon has a frequency, wavelength

and velocity. To predict electrical conductiv-

ity, the Seebeck coefficient and the electronic contribution to the thermal conductivity requires knowledge of a material’s electronic band structure (i.e., the energy levels of all the elec-trons in the system) and the mobility of the electrons. The mobility often is expressed using a relaxation time, which gives the average time between the collisions of an electron with other electrons, defects, system boundaries and phonons. Alternatively, the mean free path (the distance an electron trav-els between collisions) is used. Because electrons are quantum mechanical enti-ties, their behavior is governed by the Schrödinger equation, and quantum-based calculations are required. Various techniques are available, but increases in accuracy come at very large increases in computational power, requiring microprocessor clusters or supercomput-ers.

Density functional theory is the most commonly used quantum-based approach. Traditional density func-tional theory underestimates the elec-tronic band gap; recently it has been modified to address this issue, typically by making the calculations more com-plex. It is more challenging to predict the electron relaxation times than the band structure, and simplifying assump-tions typically are made (e.g., that all electrons have the same relaxation time). Once researchers determine the electronic band structure and relax-ation times, they then can calculate the electrical conductivity, Seebeck coeffi-cient and electronic contribution to the thermal conductivity using solutions of the Boltzmann transport equation and definitions of the electrical and thermal fluxes.

Calculating the phonon contribution to the thermal conductivity is analo-gous to that of electrons: It requires the phonon band structure (i.e., how the phonon frequencies are related to their wavelengths) and relaxation times. These quantities can be predicted using molecular dynamics simulations and/or lattice dynamics calculations. In a molecular dynamics simulation, the

Modeling thermoelectric materials and devices

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positions and velocities of a collection of atoms are predicted using Newton’s second law. Because this approach uses the classical framework of Newton’s laws of motion, it is suitable only at high temperatures (typically above the Debye temperature, the temperature above which all thermal vibrations are fully activated), where quantum effects on the phonon mode populations are small. In a lattice dynamics calculation, the atoms are treated as a mass–spring system, leading to a multiple degree-of-freedom vibration problem. Linear (harmonic) analysis allows for the calculation of the frequencies, whereas the relaxation times are obtained by perturbing the harmonic solution with higher-order terms. Lattice dynamics calculations are performed in a quan-tum framework, allowing for the con-sideration of lower temperatures than what can be modeled in a molecular dynamics simulation.

The required inputs to a molecu-lar dynamics simulation or a lattice dynamics calculation are the forces that the atoms in the thermoelectric mate-rial exert on each other. These forces can come from two sources. The first source uses quantum-mechanics-based density functional theory calculations. Although highly accurate and allow-ing for all the thermoelectric properties to be predicted using the same frame-work, this type of phonon calculation is computationally demanding, and the theoretical techniques are still being developed. Only in the past five years have the first fully quantum predic-tions of the phonon contribution to thermal conductivity been made on simple materials (e.g., silicon), but the good agreement found with experiment is encouraging. This quantum-based approach is only feasible as a means to provide the input to lattice dynamics calculations. The computational time required to use quantum calculations to predict the forces between atoms makes it prohibitive to use quantum-based molecular dynamics simulations to pre-dict phonon properties.

Empirical interatomic potentials are the second source for predicting

the forces between atoms. A potential is typically an algebraic expression that pro-vides the energy and forces between pairs or triplets of atoms based on their rela-tive positions. The forms of these poten-tials are selected to capture the nature of the bonding in a spe-cific material (e.g., electrostatic, covalent and van der Waals), and free parameters are chosen so as to reproduce experimental data or predictions from quantum calcula-tions, such as the lattice constant, bulk modulus or defect energies. Because of their simple algebraic form, potentials are used to calculate the forces between atoms many orders of magnitude faster than quantum calculations, allowing for very fast lattice dynamics calculations and molecular dynamics simulations of sufficient length to predict phonon properties.

The disadvantage of this approach is that most of the potentials are fit to structural and mechanical properties and do a poor job of predicting thermal properties (e.g., phonon frequencies and thermal conductivity).

Although using potentials to drive lattice dynamics calculations or molec-ular dynamics simulations can capture the qualitative trends found by experi-ment (e.g., how thermal conductivity varies with temperature), they typically do not have good quantitative predic-tive power. In recent years, however, more effort has been put into develop-ing potentials using phonon properties as input, suggesting that this approach, which is orders of magnitude faster than quantum-based methods, may yet prove to be suitable for accurately predicting the thermal performance of thermo-electric materials.

This discussion on how to predict the electrical conductivity, Seebeck coefficient and thermal conductivity is valid for bulk materials, which was the major focus of thermoelectric research

up to the 1990s. Since then, nanostruc-tured materials have emerged as excit-ing candidates for increasing ZT. Such materials may contain free surfaces, as in a nanowire, or interfaces spaced as closely as a few nanometers, as in a superlattice, which creates additional scattering sites for electrons and pho-nons. Predictions of how electrons and phonons interact with interfaces can also be made using density functional theory calculations, molecular dynamics simulations and lattice dynamics calcu-lations.

Although modeling of a bulk mate-rial can be performed at the unit-cell level, modeling a free surface or inter-face requires much larger computational domains and resources. Furthermore, much of the theoretical methodology for modeling free surfaces and interfaces is still under development.

Maximizing the figure of meritThe above explanation of thermo-

electronic properties and modeling provides a backdrop for looking at the development of thermoelectronic mate-rials during the past half-century.

The emphasis for thermoelectric refrigeration has been on finding mate-rials that maximize ZT to realize a COP as close to the Carnot limit as possible. To compete with traditional technolo-gies, ZT greater than 3 is required.

Although high values of ZT also are desired in power generation, recent emphasis on waste heat recovery (e.g., from the tailpipe of a car) points to a need for thermoelectric materials that are inexpensive, safe and easily pro-

Figure 3. The phonon contribution to thermal conductivity can be reduced by adding defects, interfaces and free surfaces that can scatter phonons. Limits to thermal conductivity are now being reached, but there is still potential to increase the Seebeck coef-ficient by manipulating the electronic band structure.

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Modeling thermoelectric materials and devices

cessed with less emphasis on high ZT values.

The definition of ZT in Equation (2) shows that it is desirable to maximize the Seebeck coefficient (to maximize the Peltier heating and cooling), maxi-mize the electrical conductivity (to minimize Joule heating) and minimize thermal conductivity (to minimize the parasitic heat flow from the hot junc-tion to the cold junction). The ideal thermoelectric material is a so-called phonon-glass, electron-crystal and has the low thermal conductivity of a glass (where the atoms are disordered) but the high electrical conductivity of a crystal (where the atoms are ordered). In bulk materials, these three properties are not independent and their relation-ship hinders ZT. Metals, for example, have a high electrical conductivity but high thermal conductivity and low Seebeck coefficient, making them not useful for thermoelectric energy conver-sion.

In the initial development of ther-moelectric materials in the 1950s and 1960s, doped semiconductors attracted attention because of the ability to control their electronic band structure and achieve ZT values slightly lower than 1. Bismuth and it compounds were the best materials, but issues regarding abundance and toxicity were barriers to large-scale commercialization. Also, the available ZT was simply not high enough to make thermoelectric refrig-erators and generators compete with existing technologies. (The exception was niche applications, such as power generation in deep-space probes, where the excellent durability and reliability of thermoelectric devices offset low efficiencies.) More abundant materials, such as silicon, suffered from high bulk thermal conductivities, leading to ZT values on the order of 0.01 and were of essentially no interest.

A major breakthrough came in the late 1990s, when it was realized that restricting semiconductors to small dimensions (e.g., thin films, nanowires and superlattices) could dramatically decrease their thermal conductiv-ity while maintaining good electrical properties. This thermal conductivity

decrease occurs because the phonon mean free path is typically longer than the electron mean free path. Appropriately spaced boundaries in a material (either interfaces or free sur-faces) can significantly increase phonon scattering, as shown in Figure 3, but not affect electron scattering.

Thus, much of the effort in thermo-electric materials design during the past 15 years has focused on decreasing the phonon contribution to the thermal conductivity.3–5 Initial efforts have probed ordered nanostructures, such as superlattices (periodic one-dimensional arrangement of nanometer-sized layers) or bulk materials with regularly spaced quantum dots. ZT values of about 2 have been reported, but these materials, (e.g., Bi2Te3/Sb2Te3 superlattices,) suffer from slow and costly production.

Noting that the success of superlat-tices comes from the high density of internal interfaces and not the period-icity, researchers have moved toward making bulk-like materials with nano-meter-sized grains, with encouraging results.

Nanostructures with free surfaces also show promise for thermoelectric energy conversion, and experimental measurements of roughened silicon nanowires show dramatic decreases in thermal conductivity, pushing ZT toward unity. Atomic-level modeling is important in understanding these measurements so that the underlying physical mechanisms can be identi-fied and exploited in the design of new materials.

In recent years, researchers have also explored bulk materials, with a particular interest in those with large unit-cells,2 such as skutterudites, which contain angstrom-sized internal pores. Phonon transport in these materials can be hindered by the presence of “rattler” atoms inside these pores or through the small-scale disorder present at the unit cell level.

Outlook for modeling and thermoelectric materials

Current research trends suggest that a lower bound to the phonon contribu-tion to thermal conductivity (approxi-

mately 1 watt per meter∙kelvin) has been reached. Additional gains will be marginal and will not allow for the still-needed increases in ZT. Effort is shifting toward the electron transport properties, with a focus on increasing the Seebeck coefficient through quan-tum confinement and adding resonant impurity states to distort the electronic band structure.

Because of advances in theoretical tools and computational power, mod-eling of thermoelectric materials and devices has emerged as an important component in the progress of pushing ZT higher and identifying new materi-als. Although modeling alone cannot be used to design new materials, it is important in screening materials more efficiently than can be done through experimental fabrication and character-ization. Modeling also allows for identi-fication of the basic physical phenom-ena that govern the transport of charge and heat, allowing for new insights into how materials can be tailored to opti-mize their thermoelectric properties.

About the authorMcGaughey is a professor at

Carnegie Mellon University. Contact: [email protected].

References1A. Majumdar, “Thermoelectricity in Semiconductor Nanostructures,” Science, 303, 777–78 (2004).2G.J. Snyder and E.S. Toberer, “Complex Thermoelectric Materials,” Nat. Mater., 7, 105–14 (2008).3A.J. Minnich, M.S. Dresselhaus, Z.F. Ren and G. Chen, “Bulk Nanostructured Thermoelectric Materials: Current Research and Future Prospects,” Energy Environ. Sci., 2, 466–79 (2009).4D.L. Medlin and G.J. Snyder, “Interfaces in Bulk Thermoelectric Materials,” Curr. Opin. Colloid Interface Sci., 14, 226–35 (2009).5M. Zeberjadi, K. Esfarjani, M.S. Dresselhaus, Z.F. Ren and G. Chen, “Prespectives on Thermoelectrics: From Fundamentals to Device Applications,” Energy Environ. Sci., 5, 5147–62 (2012).6M. Kaviany, Principles of Heat Transfer. Wiley, New York, 2002. n

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OCTOBER 7–11, 2012 DAVID L. LAWRENCE CONVENTION CENTER

PITTSBURGH, PENNSYLVANIA, USAMaterials Science & Technology2012 Conference & Exhibition

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40 www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 3

Issues of scarce materials in the

United StatesStephen W. Freiman and Lynnette D. Madsen

Shortages of rare earth minerals is a visible and important issue

for the economy of the United States as well as national security. Potential shortages loom, too, for other miner-als. This article addresses current issues regarding the scarcity of some miner-als, particularly those of important for producing engineered ceramics. We will introduce the concept of a “criti-cality matrix,” as described in a recent National Research Council report, and we summarize current and poten-tial future activities aimed at relieving these shortages.

The availability of raw materials is crucial to the production of advanced products in numerous areas of the economy, e.g., electronics, aerospace, automotive and is equally important to national security. As an example, the number of elements necessary for the manufacture of computer chips expanded from 11 in the 1980s to potentially 59 elements today.

The automotive industry provides another good example of the expanded range of minerals needed for today’s high-performance and energy-efficient vehicles. Nearly 100 years ago, Henry Ford introduced vanadium into the steel used in the Model T to strengthen the material and reduce the weight of the car. Today’s automobiles include many more functionalities than their predecessors, containing at least 39 minerals, some of which are becoming increasingly difficult to acquire. Of particular importance to the automotive sector

Government and the private sector can take

steps to address scarcity of critical materials

for manufacturing of ceramic materials.

41Nb

25Mn

57La

78Pt

59Pr

Recent government reports address issues and tactics related to scarce and critical raw materials. (Credit: Mn image-Images of Elements; others– Wikipedia.)

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are the platinum group metals (pal-ladium, platinum and rhodium), which are crucial for the operation of catalytic converters. Lithium and several of the rare-earth elements are necessary for rechargeable batteries in electric and hybrid vehicles. Other important products requiring the use of poten-tially scarce minerals include cellular telephones (tantalum), liquid crystal displays (indium), energy-efficient lighting (rare earths), wind turbines (rare earths) and photovoltaic cells (selenium, tellurium, indium).

At one time, the US was relatively self-sufficient with respect to almost all necessary minerals. However, most of the raw materials that are used today in this country are acquired from outside sources, some of which are wholly reli-able.

In most cases availability from for-eign sources is not an issue. Normal trade relationships are in place, and availability of the material at market prices is assured. However, when one source dominates the market and there is political or social discord as well as competing needs, acquisition of the necessary minerals becomes problem-atic. The difficulty in obtaining certain raw materials has raised concern in the US within the government and private sector of how possible shortages of cru-cial starting materials could affect the manufacture of key components and national security.

The scarcity of raw materials and its impact on ceramic research and manufacturing was the primary topic at the September 2011 meet-ing of the Interagency Coordinating Committee on Ceramics Research and Development. This paper discusses the issues behind the scarcities and the mea-sures available to assure that products using scarce materials can continue to be manufactured at reasonable costs.

Scarcity and criticalityA National Research Council report

entitled, “Minerals, Critical Minerals, and the U.S. Economy,”1 states that the availability of the minerals needed for the US economy can be ascribed to five factors:

• Geologic (exis-tence and preva-lence of mineral resources);

• Technical (extraction and processing of the mineral);

• Environmental (safety of mineral processing in terms of the population at large and the envi-ronment and the safety of workers);

• Political (gov-ernmental policy’s effect on access); and

• Economic (via-bility of minerals in terms of the cost that users can and will pay).

Criticality may be defined as when the loss, reduced access to, or significant cost increase of a mineral or mineral product, causes a serious disruption in manufactur-ing, reduction in performance, or unac-ceptable price increase of a manufactured product. Although the above report focused on the commercial aspects of mineral availability, a parallel study dis-cussed the potential impact of raw mate-rial shortages on the US military.2

One of the primary points made in the critical materials report is how to identify when a mineral becomes criti-cal. The NRC committee suggested a “criticality matrix” (Figure 1). The abscissa is the risk of a supply disrup-tion. The ordinate is the impact of a supply restriction on manufacturing and production, i.e., how important is the application. A major point made in the NRC report is that criticality is not a simple yes or no. Rather it is a continuous function of supply risk and impact. Criticality also is time depen-dent: What is not critical today, may be tomorrow, depending on new applica-tions, changes in political climate, etc.

The NRC panel used a number of minerals as examples, also shown in Figure 1. Their placement in the matrix was based on the judgment of the com-mittee.

Of the 11 minerals chosen as

examples, the platinum group metals, rare earths, indium, manganese, and niobium were determined to be critical. The applications in which each of these were needed, e.g., catalytic converters, electronics, batteries and liquid crys-tal displays, were viewed as extremely important. The importance of these applications coupled with the difficulty in finding appropriate substitutes, and the judged risk of supply, placed them in the critical portion of the matrix.

This NRC report also states that three time intervals should be consid-ered when evaluating criticality. In the short term—months to a few years—mineral markets are primarily influenced by unexpected changes in mineral demands, e.g., the Chinese industrial growth and demand. In the medium term—a few to 10 years—mineral users can make substitutions and bring new production facilities on line. In the long term—more than 10 years—producers can invest in innovative activities in mineral exploration, mineral processing, product design and recycling.

Today, any discussion of scarce mate-rials usually begins with rare earths: scandium, yttrium and the lanthanides series. There is significant concern about the availability of various mem-bers of this group for commercial and national security interests. The unique properties of rare earths are based on their f-shell electron structures, impor-

Figure 1. Criticality Matrix showing the 11 minerals examined by the NRC panel.1

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tant for a number of applications, e.g., high-strength magnets. It is the higher atomic number rare earths (termed heavy and often given the acronym HREE) that have the lower-grade ore and greatest usage in key applications, such as magnets, catalysts and phos-phors, that are the more important.

Rare earths are not rare in the earth’s crust compared with many other miner-als, e.g., gold, platinum and palladium. However, they are distributed in such a way that extraction and processing can be difficult and expensive. In addi-tion, the distribution of light and heavy atomic weight elements is critically dependent on the source and chem-istry of the ore from which they are extracted. According to Gschneidner,3 at current production rates, known rare earth supplies should last for 700 years. Gschneidner also points out that with a 10-percent growth rate in use (see footnote), the known availability will be depleted in less than 70 years. At this time, rare earths have become criti-

cal because China, the major source and producer, has cut back on its exports and threatens further restriction in the supply.

Rare earths exist in sufficient abun-dance (ore grade and volume) worldwide. However, many fac-tors are involved in obtaining the refined elements:

• The ratio of the light to heavy rare earths differs substantially among locations.

• The ease of processing, i.e., in terms of extracting a particular rare earth element from the ore and accompanying elements can differ

from one ore source to another, leading to significant variations in the cost of processing.

• Some rare-earth-containing ores contain substantial radioactive byprod-ucts, such as thorium, which can accu-mulate in the tailings after production of the primary material. These tailings must be disposed of in a safe manner.

• The price of rare earths coupled with the cost of production determines the extent to which new mines are sought and processing facilities con-structed. There is a significant time lag—up to five years—between the dis-covery of new sources of rare earths and the delivery of finished materials.

Impact of the scarcity of rare earths

Perhaps the most important use of rare earths is in high-strength magnets. Neodymium-iron-boron and samarium-cobalt are the two most prevalent compositions. NIB is the preferred com-position because of its superior magnetic

properties. In terms of products, the automobile contains the largest quantity of rare earths, as magnets and catalysts.

Dysprosium is frequently substituted for 6 percent of neodymium, because it enhances the magnetic properties of the alloy and reduces its corrosion sus-ceptibility. Portable disc drives depend for their performance on rare-earth magnets.

Europium is a critical element used as the red phosphor in cathode-ray tubes and liquid crystal displays. To date, no substitute for europium has been found for this application. Erbium is an impor-tant component for laser repeaters for maintaining the strength of signals in fiber-optic cables. Rare earths are also used as catalysts and more recently in high-efficiency lighting.

Table 1 provides more detail into the applications where rare earths play a significant role.

Impact of other scarce mineralsOther elements can be considered to

be critical or near-critical. Some short-ages occur because they are mined only as secondary products to other minerals:

– Indium (lighting applications) a byproduct of zinc production;

– Gallium (solar cells and photovol-taics, and GaAs for integrated circuits), a byproduct of bauxite mining, almost wholly obtained from foreign sources;

– Cobalt (additive in rechargeable batteries and fuel cells), a byproduct of nickel and copper production;

– Tellurium (semiconducting prod-ucts, e.g., CdTe), dependent on copper mining; and Rhenium (component of many high-temperature alloys impor-tant to national security), a byproduct of special copper ore mining.

Challenges in a world with limited resourcesNational security

Element shortages present national security and economy problems. The NRC report on the National Stockpile, “Managing Materials for a 21st Century

Issues of scarce materials in the United States

In part as a result of the concern over rare shortages, mining of new ore began at Molycorp’s facilities in 2011.4 Most of the anticipated production has been spoken for and it is accelerating both the modernization and expansion of their processing plant in California. In addition, Molycorp has been granted authorization to com-mence exploratory drilling for heavy rare earths.5 Preliminary exploration at the site has shown rare earth mineralization with an average ore grade of approximately four percent and a relatively high percentage of heavy rare earths.

Table 1. Applications for rare-earth elements

Element Uses

Mixed rare-earth oxide (mischmetal) Polishing compounds, capacitors, steel refining

Lanthanum Nickel-metal hydride batteries, lenses, capacitors, heavy-metal fluoride glasses, petroleum cracking catalysts

Cerium Automotive emission catalysts, glass-polishing media, UV light absorber, stabilizer for zirconia

Praseodymium Additive to NdFeB magnets, zirconia structural ceramics, welders goggles, X-ray tomography

Neodymium Magnets, lasers, glass-coloring agent, capacitors

Samarium Magnets, lasers

Europium TV phosphors, light-emitting diodes, X-ray tomo- graphy

Gadolinium Phosphors, rf communication (phase shifters, tuners, filters), optical lenses, neutron absorbers

Terbium Green phosphors, LEDs, magnetostrictive alloy (Terfenol-D)

Dysprosium Additive to magnets, phosphors, Terfenol-D

Holmium Nuclear control rods, magnets

Erbium Fiber optic amplifier, glass colorant, synthetic gems

Thulium X-ray intensifying screens, metal halide lamps

Ytterbium Optical lenses, pressure sensors

Lutetium Scintillation detectors, optical lenses

Yttrium Sintering aid for silicon nitride, superconductors, optical lenses, metal-alloying agent, laser host, fluorescent lamps

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Military”2 discusses issues relative to defense needs for potentially scarce materials. The report recommends estab-lishing a new system for managing the supply of materials for national defense. It also recommended that the system include an ongoing analytic process to identify materials as part of an integrated and flexible policy framework. The report further recommended that the federal government improve systems for gathering minerals data and information.

Congress recently addressed the issue of criticality in the fiscal year 2011 National Defense Authorization Act.6 In this document strategic materials are defined as “material essential for mili-tary equipment, unique in the function it performs, and for which there are no viable alternatives.”

According to a recent a Congres-sional Research Service Report to Congress,7 the US Department of Defense faces serious challenges in the acquisition of a number of elements used in defense applications. These include actuators in missile guidance systems, disk drive motors, lasers for mine detection, satellite communication systems, sonar and optical equipment. Energy

Clean energy production depends heavily on the availability of a num-ber of scarce elements (Table 2).8 The Department of Energy recently has begun funding research efforts (with total funding to date of $156M) under the Advanced Research Projects Agency Energy program, REACT (Rare Earth Alternatives in Critical Technologies).9 Its goal is to fund early-stage technology alternatives that reduce or eliminate the dependence on rare-earth materials by developing substitutes in key areas: electric vehicle motors and wind generators.Workforce education

One of the other significant issues that can exacerbate the mineral short-age problem is the lack of trained min-ing and mineral-processing personnel.1 In the area of rare earths alone, the decline in employment in the US during recent years was approximately 25,000 to 1,500.10 This reduction reflects the

alteration in mining activity in the US. However, as mines open and re-open, there will be a concomitant increased need for qualified personnel with rough-ly one-in-six being college educated.11

In terms of mineral exploration (and geosciences in general), there is an increasing demographically driven gap resulting in a shortfall between the rate of retirement of an aging workforce and the rate of geology-degree earn-ers. In addition, mining departments in engineering schools in the US have declined significantly in recent decades. At present, there are few universities that have maintained their mining engineering programs (with accredited curricula).11

Increasingly, there is a need for graduates who have an appreciation of one or more areas related to their area of specialization. NSF recently funded a center to improve and inte-grate geosciences across other disci-plines.12,13 Some universities are taking a proactive approach to ensure that students develop a broader perspective. For example, in the Forum Scientum program at Linköping University,14 stu-dents are networked in complementary areas. The renewed interest in the US in sourcing rare-earth and other criti-cal elements should lead to a greater demand for more geologists and geosci-entists who have an interest in minerals and knowledge of economics.

Will the current interest in this area lead to greater enrollment of students? Certainly training the next generation of scientists and engineers to design sustainability into manufacturing will

be important. In this area of sustain-ability one faculty member has devel-oped an undergraduate course on scarce mineral-based and critical materials.15 The course stresses the interrelation-ships between material availability, technical goals and economics. The concept of strategic recycling, including design for recycling and waste stream management is included. It is mostly taught from current literature, which allows for the relative comparisons among approaches in different regions of the world.

As one moves higher up the value-added chain, the more professionals are needed. In addition to mining engineers, beneficiation experts; geo-scientists; chemical, materials and industrial engineers; material scientists; and chemists are needed for further processing of elements and product development and recycling. One NSF mechanism for training university students is the Research Experiences for Undergraduates Program.16 At this time, there are more than 600 active REU sites. Fifteen percent of these sites have co-funding from the DOD. Several of the existing REU sites have a focus on sustainability.Environment: Zero waste and re-use

Another potential route to increasing the supply of scarce elements is recy-cling, or what has been called “urban mining.” Korea and Japan have begun programs toward this end.17 The only metals being recovered on a large scale in Japan are copper, gold and indium.

For success, such recycling programs must be made economically viable.

Table 2 Examples of scarce elements used in clean energy applications (courtesy of US Department of Energy)Application Component Elements

Wind energy Turbines Neodymium, dysprosium

Vehicles Motors Neodymium, dysprosium

Lithium-ion batteries Lithium, cobalt

Nickel-metal hydride batteries Cerium, lanthanum, Neodymium, praseodymium, cobalt

Photovoltaics Copper indium gallium Indium, gallium (di)selenide films

CdTe Films Tellurium

Lighting Phosphors Yttrium, cerium, lanthanum, europium, terbium

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Devices must be designed and engi-neered to permit elemental separation after their useful lifetime. A step toward recycling involves the study of “stocks and flows.” Such a study involves deter-mining where all sources of a particular element exist, and where stores of the element are present in applications or in waste (Figure 2).

There is interest in the engineering community in mining from industrial wastes as well as from initial sources. One such example is an NSF-supported study which has the objective to develop advanced technologies to recycle and process effluents disposed from aluminum manufacturing.18 NSF also has helped the Worcester Polytechnic Institute19 and Colorado School of Mines20 to establish the Center for Resource Recovery and Recycling.21

Role of materials researchThere are a number of additional pos-

sible ways in which the private sector and the government are addressing these potential shortages. One of the obvious choices is to find suitable replacements for the critical elements. In the case of rare earths, this is not easy. The unique magnetic properties of the rare-earth series occur as a result of the f-electron shell. Finding other elements, or combi-nations of elements, that can duplicate the properties of rare earths, while main-taining the same efficiencies, is chal-

lenging. However, through the science of nanotechnology, it may be possible to reduce the quantity of rare earths in each material application.

One NSF-supported project focuses on achieving a better understanding of tellurium isotopes.22 Tellurium is used primarily in industry to form copper, lead and iron alloys and more machin-able stainless steel. As well, it has a wide variety of uses (ceramics, glass fiber, vulcanized rubber, electronics industry) and with CdTe becomes a primary material in solar panels.

To date, the Ceramics Program at NSF has only a few projects that focus on alternatives or approaches that minimize the use of hazardous or scarce minerals or those that enable recycling of specific elements. One exception is the search for lead-free piezoelectrics; use of lead is restricted im many coun-tries because of its toxicity.

Additional on-going and planned US government activities

One of the NSF focus areas for Fiscal Year 2012 is Science, Engineering and Education for Sustainability.23,24 There are many activities and opportunities under SEES that capitalize on NSF’s unique role in helping society address the challenges of achieving sustainabil-ity. The mission of SEES is “to advance science, engineering and education to inform the societal actions needed for

environmental and economic sustainabil-ity and sustainable human well-being.” It is a cross-cutting NSF-wide investment area that will include support for inter-disciplinary research and education.

In addition to REACT, DOE has several Energy Innovation Hubs, such as the Batteries and Energy Storage Energy Innovation Hub, that comple-ment the usual funding mechanisms. Hubs include many investigators span-ning multiple science and engineer-ing disciplines, such as energy policy, economics and market analysis. These efforts are funded at ~$25M per year for an initial period of five years.25

Recently, workshops have been held on scarce minerals that have examined the issues and impact on scientific research and product development. As well, DOE has commissioned a report on rare earths26 outlining a strategy, and NSF has created a website that lists many recent meetings and reports on this topic.27 This topic also has gar-nered attention in Congress and the Executive Branch. For the latter, sever-al interagency working groups (focused on different aspects) are examining the best paths forward. Included in the charge is examining market forces, addressing supply diversification, secur-ing domestic supply chains, providing information to inform government and industry decision-making, addressing environmental concerns and ensuring a prepared workforce.

The Materials Genome Initiative for Global Competitiveness28—introduced in 2011—has the potential to provide a better understanding between the ele-ments used in a material and their subse-quent properties. This effort should also accelerate the process of building compo-nents composed of fewer scarce elements.

Future directionsSteps that can be or are being under-

taken by the private sector and govern-ment to help alleviate the problem. They are listed starting with the acqui-sition and recycling of scarce minerals through product design. An additional overarching issue in this area and over-all in science, technology, engineering

Figure 2. Example of Life Cycle Analysis for copper showing the balance of flows of materials. units are 1000 metric tons.1

Issues of scarce materials in the United States

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45American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

and mathematics fields is attracting and cultivating an educated workforce.Acquisition

• Identify critical elements/minerals and estimate future needs.

• Support efforts to collect data on sourcing of critical elements.

• Improve data exchange and analysis mechanisms and techniques.

• Support development of new geo-physical modeling for discovery of new scarce mineral sources.

• Continue developing trade agree-ments with foreign sources to mini-mize supply disruption risk.

• Make recycling and recovery of scarce elements economically viable.

• Address social aspects of extensive recycling efforts.

Beneficiation• Develop efficient, green extrac-

tion and processing methods that reduce energy, water and organic solvent use.

• Establish metrics. • Develop new chemistry to con-

vert nonpetroleum-based sources of organic molecules to feedstock chemicals.

Product development• Explore nanotechnology to reduce

amounts of an element needed in specific applications.

• Develop earth-abundant substi-tutes for critical elements; optimize materials design from the start.

• Design for recycling. • Deepen understanding of physics

governing structure–property rela-tionship.

Workforce development• Increase incentives to attract a

diverse set of students to pursue relevant disciplines.

• Train new scientists and engineers in sustainable manufacturing.

• Expand traditional university cur-riculum and/or explore approaches to broadening student knowledge base.

AcknowledgmentsThe authors gratefully acknowl-

edge the support of ICCCRD from L. Sloter (DDR&E). Scientific input from D. Cordier (USGS), E. Eide (NRC), M. Hill (Transtech Corp.), P. Lea (NSF), J. McGuffin-Cawley (Case Western Reserve University), S. Scott (University of California-Santa Barbara), A. Schwartz (DOE), E. Starke (U. Va.) and C. Wadia (Office of Science and Technology Policy) is greatly appreciated.

DisclaimerAny opinion, finding and conclu-

sions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF.

About the authorsStephen W. Freiman is president of Freiman Consulting, Potomac, Md. Lynnette D. Madsen is a program director in the Division of Materials Research, US National Science Foundation, Arlington, Va. Contact: steve.freiman @comcast.net.

References1Minerals, Critical Minerals and the U.S. Economy, National Academies Press, 2008.2Managing Materials for a Twenty-First Century Military, National Academies Press, 2008.3K.A. Gschneidner, Presentation at 4th Persh Conference, Arlington, Va,, 2011.4www.molycorp.com/AboutUs/OurHistory.aspx accessed on Jan. 3, 2012.5www.marketwatch.com/story/molycorp-secures-government-approval-to-con-duct-heavy-rare-earth-exploratory-drill-ing-2011-12-16 accessed Jan. 3, 2012.6National Defense Authorization Act (P.L. 11-383, H.R. 6523).7V.B. Grasso, “Rare Earth Elements in National Defense: Background, Oversight Issues and Options for Congress,” Congressional Research Service Report, 2011.

8A. Schwartz, “Critical Materials Strategy” Presentation to ICCCRD, Sept. 9, 2011.9www.arpa-e.energy.gov/ProgramsProjects/REACT.aspx accessed Dec. 28, 2011.10K.A. Gschneidner, “Replacing the Rare Earth Intellectual Capital,” Magnetics Business &Technology, Spring 2011.11www.abet.org/home/, accessed Dec. 5, 2011.12www.nsf.gov/news/news_summ.jsp?cntn_id=121362&WT.mc_id=USNSF_51&WT.mc_ev=click.13www.nsf.gov/awardsearch/showAward.do?AwardNumber=1125331.14www.liu.se/forskning/scientium/about?l=en. 15J.D. McGuffin-Cawley, “Relating the Increasing Scarcity of Mineral-Based Materials to a Materials Science and Engineering Curriculum” in Proceedings of Mid-Atlantic ASEE Conference, Easton, Pa., April 14–16, 2010.16www.nsf.gov/funding/pgm_summ.jsp?pims_id=5517.17“Urban Mining in Japan and Korea,” Asian Technology Information Program Report 11.015, Sept. 2011.18www.nsf.gov/awardsearch/showAward.do?AwardNumber=1103598.19www.nsf.gov/awardsearch/showAward.do?AwardNumber=0968839.20www.nsf.gov/awardsearch/showAward.do?AwardNumber=0968802.21www.wpi.edu/news/20090/cr3.html.22www.nsf.gov/awardsearch/showAward.do?AwardNumber=1047671.23www.nsf.gov/news/news_summ.jsp?cntn_id=118675.24www.nsf.gov/funding/pgm_summ.jsp?pims_id=50470.25www.science.energy.gov/bes/research/doe-energy-innovation-hubs/ accessed Dec. 29, 2011.26www.energy.gov/articles/energy-depart-ment-releases-new-critical-materials-strategy accessed on Dec. 29, 2011.27www.nsf.gov/mps/dmr/icccrd.jsp accessed on Dec. 29, 2011.

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2012 GlASS & OpticAl MAteRiAlS DiviSiON ANNuAl MeetiNGMay 20-24, 2012 | Hilton St. louis at the Ballpark | St. louis, Mo.

www.ceramics.org/gomd2012

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American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org 47

May 20–24, 2012 | Hilton St. Louis at the Ballpark | St. Louis, Missouri USA

Schedule at-a-GlanceSunday, May 20, 2012

Fundamentals of Glass Short Course 9:30 a.m. - 5:00 p.m. Registration 3:00 - 7:00 p.m. Welcome Reception 6:00 - 8:00 p.m.

Monday, May 21, 2012Registration 7:30 a.m. - 5:30 p.m.

Stookey Lecture of Discovery 8:00 - 9:00 a.m. Concurrent Technical Sessions 9:20 a.m. - Noon Lunch on Own Noon - 1:20 p.m. Concurrent Technical Sessions 1:20 - 5:40 p.m. Fundamentals of Glass Short Course 1:30 - 5:00 p.m. Poster Session 6:00 - 8:00 p.m.

Tuesday, May 22, 2012Registration 7:30 a.m. - 5:00 p.m.

George W. Morey Award 8:00 - 9:00 a.m. Concurrent Technical Sessions 9:20 a.m. - Noon

Norbert J. Kreidl Award for Young Scholars* Noon - 1:00 p.m. Lunch on Own Noon - 1:20 p.m. Concurrent Technical Sessions 1:20 - 5:40 p.m. Conference Dinner 7:00 - 10:00 p.m.

Wednesday, May 23, 2012 Registration 7:30 a.m. - 5:00 p.m. Concurrent Technical Sessions 8:00 a.m. - Noon Lunch on Own Noon - 1:20 p.m. Concurrent Technical Sessions 1:20 - 5:40 p.m.

Thursday, May 24, 2012 Registration 7:30 a.m. - Noon

Concurrent Technical Sessions 8:00 a.m. - Noon

*Free boxed lunches will be available to attendees on a first-come, first-served basis.

American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org 47

Invitation to attend GOMD 2012Join the Glass & Optical Materials Division in St. Louis for a

program involving the physical properties and technological processes important to glasses, amorphous solids and optical materials of all types. The meeting will feature four symposia. Sessions headed by technical leaders from industry, government laboratories and academia will cover the latest advances in glass science and technology as well as a focused examination of the amorphous state. The poster session will highlight late-breaking research as well as the annual student poster contest. We look forward to seeing you in St. Louis!

GOMD 2011 program chairs

Hotel informationHilton St. Louis at the Ballpark1 South Broadway | St. Louis, Missouri, 63102Tel: 1-314-421-1776

Room Rates$129.00 plus tax - Single/Double/Triple/Quad$104.00 plus tax - US Government Employee

Make your reservations by April 19th to secure the dis-counted rate. St. Louis is served by the Lambert-St. Louis International Airport (STL), which is approximately 14 miles from the hotel.

Juejun (JJ) HuUniversity of Delaware

J. David Musgraves Clemson University

GOMD leadershipJohn Ballato, Division Chair

Kelly Simmons-Potter, Chair Elect

Shibin Jiang, Vice Chair

Steve Feller, Secretary

SYMPOSIuM I: GlaSS ScIenceSession 1: Glass Structure and PropertiesOrganizers: Sabyasachi Sen, University of California, Davis; Randall E. Youngman, Corning Inc.

This session will focus on studies of glass structure and the structur-al origin of macroscopic properties, covering oxide and non-oxide systems. Contributions will feature short- and intermediate-range structure, as obtained from spectroscopy and diffractometry as well as efforts to understand the impact of thermal history on glass structure and properties.

Glass Structure and Properties I May 21 9:20 a.m. – Noon

Glass Structure and Properties II May 21 1:20 – 5:20 p.m

Glass Structure and Properties III May 22 9:20 a.m. – Noon

Glass Structure and Properties IV May 22 1:20 – 5:40 p.m.

Session 2: non-oxide GlassesOrganizers: Andriy Kovalskyy, Austin Peay State University; J. David Musgraves, Clemson University

The session covers a wide range of topics on fundamentals and applications of non-oxide glasses, such as chalcogenides, fluorides and borides. Scientific areas of interest include basic properties (optical, electrical, thermal), advanced structural studies (EXAFS, XPS, vibrational methods, NMR, positron annihilation, etc.), photo- and radiation-induced effects, temperature-induced phenomena, modeling, aging and relaxation in non-oxide glass networks.

Non-oxide Glasses I May 23 8:00 a.m. – Noon

Non-oxide Glasses II May 23 1:20 – 5:40 p.m.

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Session 3: computer Simulation and Modeling of GlassesOrganizer: Jincheng Du, University of North Texas

This session focuses on recent progresses of atomistic-scale simu-lations of glasses to elucidate their structure and structure–prop-erty relationships through either classical- or first-principle-based approaches. It covers development of empirical potential models to better describe silicate, borate, aluminate, phosphate or mixture of these systems. The session provides an opportunity to discuss the challenges and potential solutions of these challenges of atomistic simulations of glasses.

Atomistic Simulation and May 22 9:20 a.m. – Noon Modeling of Glass I

Atomistic Simulation and May 22 1:20 – 5:40 p.m. Modeling II

Session 4: Glass transition and RelaxationOrganizer: Ulrich Fotheringham, SChOTT AG Inc.

A fundamental understanding of glass transition and relaxation is essential for enabling future breakthroughs in glass science and technology. This session will cover the thermodynamics and dynamics of glass transition and relaxation phenomena from theo-retical and experimental perspectives, with particular emphasis on recent developments.

Relaxation I May 23 8:00 a.m. – Noon

Relaxation II May 23 1:20 – 4:40 p.m.

Session 5: Glass corrosion and Surface ScienceOrganizer: Nathan P. Mellott, Alfred University

Glass is currently a component of, or a candidate for, advanced mate-rial systems utilized in a variety of technological applications, includ-ing photovoltaic modules, biomedical devices and nuclear waste storage. Optimized performance in established applications and successful integration into new market products require an improved fundamental understanding of glass corrosion and surfaces. This session will address a variety of relevant aspects, including atomic to macroscale structural controls on corrosion, surface structure and re-activity, coupling of theoretical and experimental studies of corrosion and the effects of glass corrosion on properties.

Glass Corrosion and May 23 8:00 a.m. – Noon Surface Science I

Glass Corrosion and May 23 1:20 – 5:40 p.m. Surface Science II

Session 6: topological constraints and Rigidity: theory and experimentOrganizer: Pierre Lucas, University of Arizona

Topological constraints theory describes how microscopic bond arrangements govern the thermal, mechanical and transport prop-erties of glasses at the macroscopic level. Topological theories have been successfully applied to oxide glasses, and advances, such

as temperature-dependent constraints, have been brought out. This session will focus on recent developments of theoretical and experimental aspects of the topological description of glasses.

Topological Constraints and May 23 10:20 – 11:40 a.m. Rigidity: Theory and Experiment I

Topological Constraints and May 23 1:20 – 2:20 p.m. Rigidity: Theory and Experiment II

SYMPOSIuM 2: OPtIcal MateRIalS & devIceSSession 1: active Optical MaterialsOrganizers: John Ballato, Clemson University; Shibin Jiang, AdValue Photonics Inc.

Light-emitting and optically active materials and devices are enabling elements within a wide variety of modern technologies. This symposium will address the processing and properties of optical materials as well as design, fabrication and performance of active optical devices. Of particular focus will be inorganic, organic and hybrid glasses and crystals in bulk, think-film or fiber form that exhibit light-emissive, nonlinear, electrooptic, magneto-optic, and related active optical phenomenon.

Active Optical Materials May 24 8:00 – 11:20 a.m.

Session 2: Photosensitivity and laser Modifica-tion of GlassesOrganizers: Mario Affatigato, Coe College; Denise Krol, Univer-sity of California, Davis; Takayuki Komatsu, Nagaoka University of Technology

This session includes presentations in the area of laser interaction with glasses; femtosecond interactions; thermal mechanisms for structural change; laser-induced crystallization; laser damage from electronic mechanisms; laser-induced nanostructures; photosensi-tivity; and laser-induced property changes in glasses.

Photosensitivity and Laser May 21 9:20 a.m. – Noon Modification of Glasses I

Photosensitivity and Laser May 21 1:20 – 3:00 p.m. Modification of Glasses II

Session 3: Optical Fibers and Planar Photonic devicesOrganizers: Juejun Hu, University of Delaware; Norman Anheier, Pacific Northwest National Laboratory

Glasses are important materials for optical fibers and on-chip photonic devices given their excellent optical transparency and capacity for low-loss fiber and planar processing. Novel oxide and non-oxide glass compositions and fabrication technology develop-ment have further enabled emerging applications, such as light emission, nonlinear optical signal processing, evanescent wave spectroscopy and sensing. This session will cover material synthe-

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May 20–24, 2012 | Hilton St. Louis at the Ballpark | St. Louis, Missouri USA

sis and processing as well as device fabrication and applications of innovative device architectures.

Planar Glass Photonics May 22 9:20 – 11:40 a.m.

Optical Fibers May 22 1:20 – 5:40 p.m.

Session 4: Optical absorptionOrganizer: Mark Davis, SChOTT North America Inc.

All aspects relating to absorption and/or redirection of energy in glass and related materials will be the subject of this symposium, including absorption, temperature dependencies, scattering, reflection, energy trapping, resonance behavior and characteriza-tion techniques.

Optical Absorption May 23 8:00 – 10:20 a.m.

Session 5: cancelled

Session 6: Optical ceramics and Glass-ceramicsOrganizer: Robert J. Pavlacka, Army Research Lab

Ceramics with transparency in the visible or IR spectrum are useful for applications such as solid-state lasers, transparent armor, high-temperature windows, missile domes and scintillators. This session will focus on processing, characterization and performance of transparent ceramic materials and devices. Some topics of interest include novel green-forming methods, sintering and advanced densification methods, grain-boundary characterization, optical and mechanical behavior, and device performance.

Optical Ceramics and Glass- May 23 3:20 – 6:00 p.m. Ceramics

SYMPOSIuM 3: cROSS-cuttInG tOPIcSSession 1: Glass and Optical Materials for energy and environmental applicationsOrganizers: Barrett G. Potter, University of Arizona; Kelly Simmons-Potter, University of Arizona; James Marra, Savannah River National Laboratory

These sessions will provide a forum for the discussion of new results in materials and processes for solar energy (e.g., photovoltaics, solar, thermal) and fuel cell development; energy storage strategies; bulk material and thin-film technologies for energy management (optical, thermal); and materials for hazardous and radioactive waste immobi-lization and environmental remediation.

Materials for Fuel Cells and May 21 9:20 a.m. – Noon Energy Storage

Solar Energy Materials May 21 1:20 – 3:00 p.m.

Nuclear Waste Glass May 21 3:20 – 5:00 p.m. Chemistry and Processing

Session 2: nMR Studies of the Structures and dynamics of GlassesOrganizer: Steve Martin, Iowa State University

First, the session will examine the use of various NMR spectros-copies to examine the short- and intermediate-range atomic structure of glasses, supercooled liquids and glassforming liquids. Second, the session will examine the use of various NMR spectros-copies to examine the many dynamic processes that are active in glasses, supercooled liquids and glassforming liquids.

NMR Studies of the May 23 10:20 a.m. – Noon Structure of Glass 1: Mixed Glassformer Systems

NMR Studies of the May 23 1:20 – 3:20 p.m. Structure of Glass 2: ChemicalOrder and Disorder Effects

NMR Studies of Structure May 23 3:20 – 5:40 p.m. of Glass 3: Structure and Dynamics

NMR Studies of the May 24 8:00 – 10:20 a.m. Structure of Glass 4

NMR Studies of the May 24 10:20 a.m. – 12:20 p.m. Structure of Glass 5

Session 3: archeological Glass Science and technologyOrganizers: Denis Strachan, Pacific Northwest National Laboratory; Hongjie Luo, Shanghai Institute of Ceramics, Chinese Academy of Sciences; Weidong Li, Shanghai Institute of Ceramics, Chinese Academy of Sciences

Glass and glassy materials, such as ceramic glazes and enamels on metals and ceramics, are present on many archaeological sites, indicating a sophisticated level of craft practice and materials understanding. For more than 120 years, glass-containing artifacts have been studied for their compositional variability. Although much less constrained than the ideal, natural and manufacturers analogues also provide the possibility of examining experiments of a far greater duration than possible in laboratory experiments.

Archeological Glass Science May 23 8:00 – 10:20 a.m.

and Technology

Session 4: liquid Synthesis and Sol–Gel-derived MaterialsOrganizer: Brian Riley, Pacific Northwest National Laboratory

Liquid and sol–gel materials synthesis routes are becoming more common in laboratory practice. These techniques allow compo-sitional flexibility and often provide a near-room-temperature synthesis route for chemistries that might be difficult to make with compound fusion at high temperatures. Room-temperature synthesis routes require less production energy and allow for more control over microstructure. These material structures often can

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2012 GOMD ANNuAl MeetiNGSign up by April 20th at www.ceramics.org/gomd 2012 to save

be subsequently heat-treated for densification or left in the porous state, depending on the specific application. This session will cover topics related to liquid synthesis and sol–gel-derived materials for various applications.

Liquid Synthesis and Sol–Gel May 21 9:20 a.m. – Noon Derived Materials I

Liquid Synthesis and Sol–Gel May 21 1:20 – 3:20 p.m. Derived Materials II

SYMPOSIuM 4: FeStSchRIFt tO the GlaSS ReSeaRch caReeR OF PROF. delbeRt e. daYSession 1: the Mixed alkali effect and Ion- conducting GlassesOrganizer: David Sidebottom, Creighton University

Prof. Day devoted much of his early career to studying the mixed-alkali effect in oxide glasses, including important contributions on internal friction, ion conductivity and thermal properties. his review article “Mixed-Alkali Glasses—Their Properties and Uses,” J. Non-Cryst. Solids, 21, 343–47 (1976), is the most highly cited paper authored by Prof. Day, and it continues to be cited by researchers in the field. This session will include papers on the mixed-alkali effect as well as papers pertaining to ion-conducting glasses and relaxation phenomena.

The Mixed-Alkali-Effect and May 22 9:20 a.m. – Noon Ion-Conducting Glasses I

The Mixed-Alkali-Effect and May 22 1:20 - 6:00 p.m. Ion-Conducting Glasses II

Session 2: Phosphate Glasses: their Structures, Properties and applicationsOrganizer: Richard Brow, Missouri University of Science & Technology

Prof. Day has studied the properties of phosphate glasses and melts for many years, including early studies of ion-conducting systems. More recently, he discovered that low-temperature iron phosphate glasses can incorporate large concentrations of a widerange of various oxides in their structure, while retaining outstanding chemical durability, thus making them candidates for hosting nuclear wastes. This session will include papers on the iron phosphate glasses, with more general papers on the structure, properties and applications of other phosphate glasses.

Phosphate Glasses: Their May 21 9:20 – 11:40 a.m. Structures, Properties and Applications I

Phosphate Glasses: Their May 21 3:20 – 5:20 p.m. Structures, Properties and Applications II

Session 3: dta and dSc Methods for Glass crystallization StudyOrganizer: Edgar Zanotto, Federal University São Carlos

hundreds of papers about glass crystallization by these methods are published every year. There is thus scope for a serious brain-storming aiming at clarifying what sort of relevant quantitative information one can get from DTA and DSC techniques. With his colleague at Missouri S&T, Prof. Chandra Ray, Prof. Day has made important contributions to the use of differential thermal analytical techniques to characterize nucleation and crystallization kinetics, glassforming tendency and critical cooling rates for glassforming melts. This session will include invited review talks as well as short presentations on the current state-of-the-art in characterizing nucleation and crystallization behavior by DSC and DTA methods.

DTA and DSC Methods for May 24 8:00 a.m. – Noon Glass Crystallization Study

Session 4: Glasses for biomedical applicationsOrganizers: Julian Jones, Imperial College London; Matthew Hall, Alfred University

In 1985, Prof. Day founded Mo-Sci Corporation to produce glass mi-crospheres used to treat inoperable liver cancer. More recently, Prof. Day, his students and colleagues at Missouri S&T have shown that borate-based glasses possess remarkable transformation kinetics to biocompatible materials and have potential applications as scaffolds for bone defects and for soft tissue treatments, including wound healing. This session will provide a forum to present the results of basic and applied research on the use of glass and glass-ceramic materials in the areas of medicine and biotechnology.

Glasses for Bio-Medical May 22 1:20 – 5:00 p.m. Applications

POSteR SeSSIOn & Student POSteR cOMPetItIOn:Organizer: Morten Smedskjaer, Corning Inc.

Session May 21 6:00 – 8:00 p.m.

ShORt cOuRSeFundamentals of Glass Science and technologyRegister for this day-and-a-half short course, taught by Arun K. Varshneya, Saxon Glass. Professional engineers, scientists, administrators and students who wish to rapidly acquire a general idea of glass or append their education in materials engineering should attend. Course topics include commer-cial glass families, glassy state, nucleation and crystallization, phase separation, glass structure, glass technology, batch cal-culations, glass-melting and glass-forming, glass properties and engineering principles, and elementary fracture analysis.

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51American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

MCARE 2012 was attended by almost 250 participants from 20 countries and was bigger and better than ever before. This was the third in the series of interso-ciety, interdisciplinary meetings held every two years on Materi-als Challenges in Alternative and Renewable Energy. It was held Feb. 26 to March 1, 2012, in Clearwater Beach, Fla. There were 30 percent more papers and presentations than in previ-ous meetings, and the feedback received has been extremely positive. After the meeting one participant wrote to the meeting cochairs, George Wicks and Jack Simon, “I think I learned more new technology in four days than four years in college.”

MCARE 2012 had more than 200 excellent technical presentations, including a special opening day set of plenary talks that were all posted on line and for the first time, even before the session was completed. There were

two poster sessions, including one developed by students, that consisted of a poster competition and a unique and entertaining “energy generation competition,” with cash awards.

Also, there were many network-ing events and opportunities every day of the conference, and all participants had the opportu-nity to “ride and drive” two very special vehicles—Toyota’s new Fuel Cell Hydrogen Vehicle and GM’s Chevy Volt.

“This meeting is one of the few examples of all three materials disciplines, along with their re-spective organizations and societ-ies, teaming together to put on a meeting of this type and impor-tance,” said Wicks. The organiz-ing societies were The American Ceramic Society (ceramics/glasses), ASM International, TMS (metals/composites) and SPE (plastics/polymers). MRS and SAMPE endorsed the meeting. n

1ACerS welcomed abut 250 participants, including Kirsten Larson and Jacklyn Whitehead, undergraduate students from California Lutheran University in Thousand Oaks, Calif., and Professor Michael Shaw from the same. 2Al fresco dining at a networking lunch. Coorganizers Jack Simon and George Wicks are at the center, left and right, respectively. 3&4A different look under the hood: Ming Au inspects GM’s Chevy Volt electric car(3) while several attendees have a look at Toyota’s fuel-cell-powered car(4). 5Plenary speakers, Megan McCluer and Jim Ahlgrimm, put final touches on their talk. 6At the student poster session. 7The Iowa State University team of Lisa Rueschhoff, Sam Reeve, Kate Lindley and Logan Kroneman (pictured from left) won the Materials for Energy Conversion contest. They used magnetic induc-tion to generate electric power from wind energy.

MCARE’12 highlights 1 2

3 4

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5 6 7

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resources

Calendar of eventsApril 20129–13 2012 MRS Spring Meeting – Moscone West Convention Center, San Francisco, Calif.; www.mrs.org/spring2012

15–18 The 11th Int’l Conference on Ferrites – Okinawa Convention Center, Okinawa, Japan; www.icf11.jp (post-poned from Nov. 14–18, 2011, because of earthquake and tsunami)

15–18 NanoManufacturing Conference and Exhibits — Hynes Convention Center, Boston, Mass.; http://nanoman-ufacturing/sme.org

19 Toledo Glass and Ceramic Award Presentation and Dinner, organized by the Michigan/Northwest Ohio Section of ACerS – The Toledo Club, Toledo, Ohio; [email protected] or www.ceram-ics.org

24–25 2nd Int’l Symposium on Materials Processing Science with Lasers as Energy Sources – Clausthal University of Technology, Clausthal-Zellerfeld, Germany; www.mpsl-ecers2012.de

26–29 2nd Int’l Advances in Applied Physics & Materials Science Congress – Kremlin Palaca Hotel, Antalya, Turkey; www.apmas2012.org

30–May 3 OTC2012: Offshore Technology Conference – Reliant Park, Houston, Texas; www.otcnet.org/2012

May 20128–10 Powder and Bulk Solids – Stephens Convention Center, Rosemont, Ill.; www.powderbulksolids.com

13–18 Ultra-High-Temperature Ceramics: Materials for Extreme Environment Applications II – Schlosshernstein Conference Hotel, Hernstein, Austria; www.engconfintl.org

15–17 CISILE 2012: The 10th China Int’l Scientific Instrument and Laboratory Equipment Exhibition – China International Exhibition Center, Beijing, China; www.cisile.com.cn/en

15–18 6th Int’l Glass Conference – Saratov Glass Institute, Saratov, Russian Federation; www.icglass.org

20–23 10th Int’l Symposium on Ceramic Materials and Componentsfor

Energy and Environmental Applications – Int’l Congress Center, Dresden, Germany; www.cmcee12.de

20–24 Glass & Optical Materials Division Spring Meerting – Hilton St. Louis at the Ballpark, St. Louis, Mo.; www.ceramics.org/gomd2012

21–24 Int’l Thermal Spray Conference 2012 – Hilton Americas Houston, Houston, Texas; www.asminternational.org/itsc

22–25 Ceramitec 2012 – New Munich Trade Fair Centre, Munich, Germany; www.ceramitec.de

June 20123–6 11th European Society of Glass/ 86th Annual Conference of the German Society of Glass Technology – Maastricht Exhibition and Congress Center, Maastricht, Netherlands; www.hvg-dgg.de

10–12 3rd Advances in Cement-Based Materials: Characterization, Processing, Modeling and Sensing – The University of Texas at Austin, Austin, Texas; www.ceramics.org/cements2012

18–20 AeroMat 2012 Conference and Exposition – Charlotte Convention Center, Charlotte, N.C.; /www. asminternational.org

24–28 ECCM15:15th European Conference on Composite Materials – Venice, Italy; www.eccm15.org

July 20121–4 5th Int’l Conference on Engineering Failure Analysis – Hilton Hotel, The Hague, Netherlands; www.icefaconfer-ence.com

2–6 4th Workshop for New Researchers in Glass Science and Technology — Glasses: Formation, Structure and Strength – Montpellier, France.; www.icglass.org

9–11 Concrete in the Low-Carbon Era – University of Dundee, Dundee, UK; www.ctucongress.co.uk

9–12 IMTCE 2012: 8th Int’l Materials Conference and Exhibition — Sunway Resort Hotel and Spa, Selangor, Malaysia; www.imtce2012.com

15–19 ICC4: 4th Int’l Congress on Ceramics – Sheraton Chicago Hotel & Towers, Chicago, Ill.; www.ceramics.org/icc4

23–27 2nd Global Congress on Microwave Energy Applications – Long Beach, Calif.; www.mrs.org/2gcmea-2012

August 201212–17 Gordon Research Conference on Solid-State Studies in Ceramics: New Insights and New Paradigms for Fracture and Deformation in Ceramics – Mount Holyoke College, South Hadley, Mass.; www.grc.org

13–17 IMRC 2012: XXI Int’l Materials Research Congress – Cancun, Mexico; www.mrs-mexico.org.mx

26–30 ICAMR’12: 2012 Int’l Conference on Advances in Materials Research – COEX, Seoul, South Korea; http://acem12.cti3.com/icamr12.htm

26–31 NANO2012: 11th Biennial Int’l Conference on Nanostructured Materials – Rodos Palace Convention Center, Rhodes, Greece; www.nano2012.org

September 20122–5 ICCCI2012: 4th Int’l Conference on the Characterization and Control of Interfaces for High-Quality Advanced Materials 2012 – Hotel Nikko Kurashiki, Kurashiki City, Japan; www.jwri.osaka-u.ac.jp/~conf/iccci2012/top.html

10–13 Innovations in Biomedical Materials 2012 — Hilton North Raleigh-Midtown, Raleigh, N.C.; www.ceramics.org/biomaterials2012

16–20 XIII Int’l Conference on the Physics of Non-Crystalline Solids – Yichang Three Gorges, Hubei, China; www.xiii-pncs.com

Dates in RED denote new entry in this issue.

Entries in BLUE denote ACerS events.

denotes meetings that ACerS cosponsors, endorses or other- wise cooperates in organizing.

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53American Ceramic Society Bulletin, Vol. 91, No. 3 | www.ceramics.org

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www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 356

In today’s global economy, students are encouraged to broaden their tech-nical and cultural skills through study abroad programs. Spending a semester abroad taking classes is popular, but there also are numerous programs that immerse students in a different culture while par-ticipating in international research.

This article reports on the experi-ences of a few students who have spent time abroad learning and growing technically and culturally, including those of coauthor, Ryan Gebhardt, who spent a summer doing research at the Universität des Saarlandes in Saarbrücken, Germany. Their thoughts and experiences are condensed into a few topics that a travelling student may want to consider. Students told the authors that, despite being more than 1000 miles away, research practices share common elements with a few notable cultural differences.

Meet new peopleWhen working abroad, language

barriers can prove to be difficult in daily tasks, such as buying groceries or ordering food at a restaurant. However, most European students have had at least a few years of learning English. Most students do not get to use this knowledge regularly and are excited to interact with native English speakers. For example, Ryan found that a simple German phrase such as “Sprechen Sie Englisch? Ich komme aus den USA,” which means “Do you speak English? I come from the USA,” is a great conver-sation starter when meeting individuals outside of the lab.

Additionally, do not underestimate

the diversity within a research labora-tory. Similar to the US, laboratories attract scientists from across the world, so the cross-cultural experience can extend well beyond the country being visited. In Germany, for example, it is common for laboratory coworkers to socialize occasionally outside of the work environment, providing an opportunity to get to know German colleagues and visitors from around the world in a casual setting.

Tuition costsAn easy topic to discuss with other

international students is differences in education systems. One large differ-ence that quickly becomes apparent is the difference in tuition costs. Tuition costs vary by region, but, in Europe as a whole, it is significantly less expen-sive to further one’s education past high school compared with the US. For instance, within the past five years in Germany, there have been political changes that resulted in tuition decreas-ing from approximately 600 Euro per semester to essentially free.

This difference can be attributed to differences in each government’s use of tax dollars. In the US, it is common for students to graduate with a large debt load and begin paying off their debt shortly thereafter. However, in Germany, students do not accrue large debts while in school, but rather the population as a whole pays for educa-tional expenses via taxes.

Classroom behaviorAs a research assistant, Ryan found

that attending class was not mandatory. However, he went to a few classes just to supplement the experience abroad. One observation was that there was a collection of students at the front of the classroom paying close attention, while other small clusters of students at the sides or back of the classroom seemed to be preoccupied with making chit chat or using their laptops for enter-

tainment, such as watching videos. In the US, this behavior is highly discour-aged and one wonders whether it is related to students not being required to pay to attend college. At the least, the appearance of attentiveness in the classroom varies significantly between the US and Europe.

Laboratory comparisonsAlthough classroom behavior varies

greatly, the research experience is rath-er similar in both places. A new student needing training about new tools or processes often learns these from a more experienced peer. Sometime later, this skill is passed on to new incoming stu-dents. Although formal, written safety procedures may be followed strictly at first, the unwritten practices often tend to deviate from these procedures over time. These unwritten practices are then passed on through generations of students, decreasing the overall aware-ness of safety in the laboratory.

It is customary for students to work long hours without knowing about the long-term goals and efforts of the proj-ect. This leads to student workers often seeing what appear to be limited results. A researcher’s life in the laboratory var-ies little by location.

The benefits of traveling or studying abroad are numerous, and the opportu-nities should be at least considered by all engineering students.

Ryan Gebhardt is in the MS/BS program in materials science and engineering at Iowa State University. He is from Waltham, Minn., and intends to work in industry on LED or photovoltaic technologies after graduation 2013.John Solomon hails from Boone, Iowa, and is a graduating senior in materials science and engineering at Iowa State University. He has accepted a position as an associate engineer at Caterpillar.

deciphering the discipline

How to speak the language

of international research

Ryan Gebhardt and John Solomon

Guest columnists

www.ceramics.org | American Ceramic Society Bulletin, Vol. 91, No. 356

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June 10-12, 2012 University of Texas at Austin Austin, TX

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