An IMI-NFG Outreach Activity for Engaging Students in Glass Science

(Pre-College and even University) through inquiry, participation and wonder

William R. Heffner & Himanshu Jain International Materials Institute for Glass

Lehigh University, Bethlehem, PA

Exploring Glass and Material Science through Candy and Common Materials

National Educators Workshop - NEW Fort Wayne, IN November 5, 2012

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Approach: A collection of interrelated experiments using common materials and candy glass (hard candy) – a material that students can make, mold and measure to explore many aspects of serious glass science.

Objectives and Approach of Program

Priorities: • low cost and within the resources of a typical high school student • yet capture relevant and significant principles of glass science • simple enough for the young student to perform independently • interesting enough to hold their attention • rich enough to mimic activities done by the material scientist • developed by glass scientists and refined through student collaboration • inter-related experiments for prolonged engagement & accumulated learning • Available free to all on our website: http://www.lehigh.edu/imi/

Primary Objective: To engage young students with the glass and material science through a series of hands-on, low-budget activities with familiar glassy materials.

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Outline of Experiments and Activities Today • Overview of Sugar Glass System • Material Synthesis – making of candy glass • Pulling “glass” fibers and a fiber drawing tower • Optical characterization Snell’s law demonstration Refractive Index Measurement • Density measurements • Crystallization Birefringence and Detecting Ordering Mechanisms & growth rates in sugar glass Crystallization in PET • Glass Transition Thermal Methods • Electrical conductivity • Demonstration Videos

For more experiments and details see IMI website: http://www.lehigh.edu/imi/

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Material Science – The Sucrose Water Phase Diagram

Student can construct the phase diagram using solubility, freezing point depression and boiling point data for this system. See Mathlouthi and Reiser (ed.), Sucrose Properties and Applications (1995).

I II

III

Heat to: Dissolve Boil to: Reduce H2O Cool quickly to Make Glass Avoid Xtals

Problem with Sucrose: Very prone to crystallization at low water content, even during cooking! 4

Recommend: 2:1 sucrose to corn syrup (by wt.) for good glass with some crystal tendency

Example of how mixing allows tailoring performance of resulting glass 5

The Making of Hard Candy (Glass) – Material Synthesis Phenomenological approach

Sucrose, Corn Syrup and Water are combined and cooked- • first to dissolve into a single liquid phase & • then to remove most of the water. Solution temp provides measure of the water content. Boil to ~ 150° C.

Cost ~ $5 in materials for many batches

Data from Food Industries Manual, 24th ed, (1997). 6

Drawing glassy “candy fibers” has never failed to excite and captivate – whether young (middle school), high school or even adult!

Typical Science Camp Activity or Teacher Workshop examples, properties and structure of glass applications e.g. optics and fiber optics making of candy glass fiber pulling

Candy Glass – A Favorite for the Science Camp

Multiple camps and workshops have provided a wonderful testing ground for what works! 7

Fiber Drawing Tower – Mimics Optical Fiber Manufacturing Process

Opportunity to explore – glass melting, visco-elasticity, heat transfer by radiation, and much more

Lamp

20 W

Lamp

20 W

Thermocouple Probe

Dimmer Switch Voltage Controller

Fiber Spool (Plastic Jar)

Fixed or Sliding Holder

Sugar Glass Rod Monitor or Control Heat input Temperature Draw rate

Candy Rod Preform heated by 20W Lamps

Estimated cost - $20 for Tower and lamps, $10 for dimmer switch control 8

Molding Sugar Glass for Optics – The Hemi Circles

Hemi Circles Ideal for Snell’s Law Demonstration

Near critical angle Above critical angle and Total Internal Reflection Snell’s Law Demonstration

Below critical angle

Internal scattering from bubbles, etc. enhances the demo

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Pfund’s Method

Refractive Index of Candy Glass via Pfund’s Method

Tara Schneider, REU(2005)

n=sqrt(d2+16h2)/d

Requires: •Slab of candy glass ~ 1 cm thick •laser pointer ($5.00) •metric ruler or caliper ($10.00) •ring stand and clamp to hold laser

With practice Tara was able to achieve a std dev of ~ 0.015 (~1%), sufficient to see the index increase of candy glass with boiling temperature. 10

Easy Refractive Index of Flat Glass Pieces Using a Gem Refractometer

Gem refractometers are now available for ~ $100 They provide a very quick and convenient approach to measuring refractive index of common glass items (slides, prisms, windows, etc.) without any construction. Good for ~ 0.5% accuracy.

Also based on total internal reflection at critical angle, so a good follow on to Pfund’s experiment. Trick is the high index hemispherical lens in the unit.

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Student Spectrometer for more accurate Refractive Index Using the Min. Deviation Method

REU student Sean Kelley (2006) develops method for making sugar glass prisms from microscope slide molds and determining index of refraction to four place precision.

index method provides σ ~ 0.0015 (0.1%)

No significant dependence of index on sucrose/ corn syrup ratio.

Candy Glass - Index vs Corn Syrup Content

1.510

1.515

1.520

1.525

1.530

1.535

1.540

1.545

1.550

0 20 40 60 80 100

Percent Corn Syrup

Inde

x (A

vg)

avg

Candy Glass - Index vs Corn Syrup Content

1.510

1.515

1.520

1.525

1.530

1.535

1.540

1.545

1.550

0 20 40 60 80 100

Percent Corn Syrup

Inde

x (A

vg)

avg-candy Sucrose

±2σ

Having spectrometer, cost is a box of microscope slides ($20) and epoxy ($3).

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Specific Gravity = (wt of glass) / (wt of displaced water) = (wt of glass) / {(wt of glass & water) – (wt of glass)}

Glass

water

water

fixed volume

Density Apparatus – Low Cost Student-built Pycnometer

Utilizes Centigram Balance – available in most high school labs and salsa jar with hole and epoxied washer for stiffening - no other costs For candy glass measurements must be made before candy dissolves (much).

REU, Sean Kelly (2006)

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Fisher Scientific 03-247Q Retails at $145

Low Cost Commercial Pycnometer An Alternative to Making Your Own

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Forensic Lab Activity: From broken glass pieces determine the type of glass using the table below:

Compositional Category

Compositional Category

Glass example or type

Additional example

T melt °C

lin. exp coef. α (1/°C)

ref index nd density g/cm3

soda lime silica glass

soda lime silica glass

window glass 1450 90 E-7 1.520

2.53

boro silicate boro silicate pyrex ~1650 32 E-7 1.474 2.23 flint (lead) glass flint (lead) glass N-F2 high

index stemware 900-1400 82 E-7 1.620 3.61

fused silica fused silica UV optics 2200 5.5 x E-7 1.458 2.20

Polariscope constructed from two polarizing sheets can be used to demonstrate the amorphous nature of glass compared to a ordered, birefringent solid such as a quartz crystal.

Birefringence –Tool for Observing Structure in Transparent Materials

Also flow induced order can be demonstrated in glassy plastic. Similar to method used by glass blowers to check for residual stress.

Glass slide – only edges visible

Calcite Crystal – very bright at this orientation

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Excellent Examples of Crystal Growth from Sugar Glass Two Distinct Mechanisms

Interior Crystal Growth From melt at elevated temperatures

Surface Crystal Growth At room temperature with moisture (humidity)

microscope slides provide convenient observation platform 16

Crystalization in 50% RH Chamber (Recipe3)

0

2

4

6

8

10

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0 5 10 15 20 25 30days in 50% RH

Crys

tal w

idth

(mm

)

12/07 (143C)12/05 (145C)

Quantitative Crystal Growth Expt. Moisture mediated surface crystallization at Room Temp

Need only: glass slides, camera, ruler and 50% Rel. Humidity Jar

Growth of outer crystal ring after 6 days at 50% RH

High School science project: Awards at County Sci. Fair & Jr. Acad. of Sci.

Cookie jar with sat. solution MgSO4 for 50% RH chamber

Batch A (143 C) Batch B (145 C)

Rate = 0.4 mm/day

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Student used Image J freeware and calculate crystal area.

Devitrification in Molten Solutions Finding the maximum crystal growth temperature

From NIH at: http://rsbweb.nih.gov/ij/ Oven cost ~ $20 with temp probe

T uniformity ± 1°C typical

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Improved Heater Design for Single Lab Period Contact Heater with Temp Set and Control < $100

Autonics Analog TC Controller (under $40, Factorymotion)

75 W Strip Heater ($30, McMaster Carr)

Stabilizes in minutes and can hold multiple samples Moderate construction skills required.

Dual Temp Unit

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After all samples are cool, examine under crossed polarizers and photograph for analysis of Crystalized Area with Image J.

Sample Analysis for Single Lab Period

Photo and Results for 6 temperatures with Replication

A

B

80 C 90 C 110 C 120 C 133 C 145 C

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Home-made Microscope Hot Stage

For existing lab microscope - transmission & reflection Uses 2-20W cylindrical heaters and dimmer switch control < $40 in cost Photos taken through eyepiece with hand held digital camera & crossed polars.

Enhancing crystal growth studies in molten sugar solutions

75x mag 2.5X obj, 5x eyepiece

20x obj, 10x eye 21

Observing Crystal Growth (125 C)

20 min 50 min

Photographed at 100X magnification through eyepiece with hand held digital camera 22

Multiple Crystal Morphologies

Interesting range of crystal morphologies observed under higher magnification with home-built hot stage. Levenson and Hartel reported some of the same morphologies in their 2004 paper. D.A. Levenson, R.W. Hartel, Journal of Food Engineering, “Nucleation of amorphous sucrose-corn syrup mixtures”

Photographed at 200X magnification through eyepiece with hand held digital camera

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• glassy state at room temperature • Tg near 75 C • easily observable crystallization near 135 C • Tm ~ 235 C.

PET is one of the common plastic materials used for beverage and other food packaging. It can be identified by the recycling code 1.

PET for Both Glass Transition and Crystallization

235 C

135 C

78 C

PET from Sperling, Intro. to Physical Polymer Sci.

Polyethylene Terephthalate

Demonstration of Crystallization from Amorphous PET

appearance to 130 C All white by 135 C )

Simple equipment includes: GE Hotplate ($20, Wal-Mart) Aluminum plate with hole drilled for Thermocouple to monitor temperature TC meter ($30, Harbor Freight) Glass Petri Dish cover

Abrupt melting at 237 C

Crystallization occurs abruptly near 135 C providing a great demo.

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Crystallization in PET under microscopic examination lamellar region in sharp contrast to sucrose crystallization

Pre crystal clear region

~8 u pitch

Milky crystal region

Lamella phase described well for students at http://en.wikipedia.org/wiki/Crystallization_of_polymers 26

http://upload.wikimedia.org/wikipedia/en/5/5c/Spherulite2.PNG

Thermal Analysis with Home-built DTA Getting a handle on Crystallization and the Glass Transition

Advantages •Low Cost •Student Assembled •Can see (and poke) what’s happening

Bath Temp

Differential Temp, ΔT

Enabling student to explore both:

Glass transition

Crystal Melting

and

Candy sample Reference

Beaker filled with oil

Endo

Observing Tg of Sugar Glass

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The Initial, Basic Student DTA •Hot Plate from the lab with •digital cooking thermometer •digital meter with TC probe ($30) •two test tubes and beaker •cooking oil and •hand made holder

Our initial manual data:

The experimentalist can literally watch what is taking place as T rises!

Provides student access to the glass transition and opportunity to explore their own curiosities. Quickly stimulating desire for more data, more experiments! 28

Improved DTA - Automated Data Collection

Adding Parallax Microcontroller and thermocouple module provides flexible, low cost data logging solution for approximately $100. Careful attention to thermal history provide some excellent data on Tg and crystallization phenomena. 29

DIY Data Collected Using Basic Stamp Microcontroller

The Basic Stamp is a microcontroller platform from Parallax Inc. popular among educators for its ease of use, capability, strong support and focus on education.

http://www.parallax.com/ MoBo mother board ($70)

Power Daughterboard ($15)

AD595 Thermocouple IC ($15)

Can read and log analog voltage from TC IC (AD 595) $110 enough for flexible data collection platform for 2 TCs.

Heating and Cooling Curves : Stearic Acid a crystalline standard material with moderately low melting point (~ 70 C).

Saucepan with water & ice

Cooling Option Too!

Note: Tm identified with kink in heating curve at ~ 70 C in good agreement with literature and comparison DSC. Significant under-cooling observed on the cooling scan.

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Clear signal of Tg near the 73° value from DSC as well as the crystallization exotherm near 135° C.

Tg Txtal

Exo

Polyethylene Terephthalate (PET) Chips in Oil

PET chips cut from the screw top of a Nestle water bottle combined with oil to provide thermal contact without melting.

Do not heat to Tm (235 C) as too hot for safety considerations.

Hand-made probe and ultra low current amplifier capable of measuring resistances in the100 G Ω range. Designed with a $3 ultra low current IC chip keeping total cost < $50.

Op Amps IC for Measuring Low Electrical Conductivity in Glass

Electrical Conductivity vs Temp in Glassy Material

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Improved Conductivity Cell with Embedded Heaters and Cooling

Conductivity of Sugar Glass

Anomalous flat region on re-heating found due to water condensation on cooling below dew pt.

Summary • Developed Curriculum of Hands-On Learning Activities to explore

Glass Science • Inter-related and build around candy glass & common materials

materials synthesis physical property measurements crystal growth – both surface and from melts glass transition (DTA and conductivity)

• Designed to engage student in real glass science through hands on participation

• With quantitative results and open ended possibilities • Tested and Student-hardened through

Science Camps, Student Science Projects, REU Activities and Teacher Workshops • Leveraged through Website for open access & wide distribution • An ongoing & growing effort – visit us often for exciting updates

and Share your own ideas and thoughts!

http://www.lehigh.edu/imi/

Collaborations: Another very valuable materials resource for teachers is the Amer. Society of Materials (ASM) They hold summer teacher camps – such as shown here at Ivy Tech in 2012. They have adopted some of our sugar glass activities for inclusion in future programs. See also the Carnegie Mellon MRSEC’s Teacher Camp activities at: http://mimp.materials.cmu.edu/hst/index.html

ASM Materials Camps for Teachers http://www.asminternational.org/

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Acknowledgements: REU students:

Tara Schneider (2006), Sean Kelly (2007) Sarah Horst (2009), Nick Ward, Jordan Davis, Adam Kohn and Paul Sihelnik (2010) Mia Korngruen (2011) Shera Demchak (2012) High school students (science projects): Julian Mark (2012) Jung Hyun (Gloria) Noh (2007, 2008) Isha Jain (2001) Science Teachers Mark Moore (2011) Cory Lowe (2011) Robert Wesolowski – ASM Master teacher and supporter (2011-2) Stefanie Corcoran (2012) Sarah Wing – IMI-NFG Coordinator , video assistant and enthusiastic supporter of all education and outreach NSF’s International Materials Institute for New Functionality in Glass (IMI-NFG): DMR-0409588 and DMR-0844014.

Demonstrations

Polariscope - Observing Order in Transparent Materials (1:39)

Candy Fiber Drawing Tower (1:45)

Writing Crystals with Light (1:13) http://rm1.cc.lehigh.edu:8080/asxgen/dept/IMI/EdVideo/CrystalWriting_768.wmv

Click on pictures to view videos

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http://rm1.cc.lehigh.edu:8080/asxgen/dept/IMI/EdVideo/Polariscope1_best.wmvhttp://rm1.cc.lehigh.edu:8080/asxgen/dept/IMI/EdVideo/FiberDrawFull_780kps.wmvhttp://rm1.cc.lehigh.edu:8080/asxgen/dept/IMI/EdVideo/CrystalWriting_768.wmvhttp://rm1.cc.lehigh.edu:8080/asxgen/dept/IMI/EdVideo/CrystalWriting_768.wmv

Questions and Comments

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An IMI-NFG Outreach Activity �for Engaging Students in Glass Science� (Pre-College and even University) through inquiry, participation and wonder Slide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Multiple Crystal MorphologiesSlide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34SummarySlide Number 36Slide Number 37Slide Number 38Slide Number 39