PPARTICLEARTICLE--STABILIZEDSTABILIZED FOAMSFOAMS ANDAND THEIRTHEIR

POTENTIALPOTENTIAL APPLICATIONSAPPLICATIONS

Urs T. GonzenbachDr. Sc. ETH

Nonmetallic Inorganic Materials, Department of Materials,ETH Zü i h S it l dETH Zürich, Switzerland

22

33

4AAPPLICATIONSPPLICATIONS OFOF POROUSPOROUS CERAMICSCERAMICS

4

• thermal and corrosion resistance

Advantages

• thermal and corrosion resistance• low density• low thermal conductivityy• controlled permeability• high surface area• …

Applications

• high-temperature thermal insulation• filters for molten metals exhaust gases

pp

• filters for molten metals, exhaust gases• catalyst carriers• bone graftsbone grafts• lightweight materials• …

5DDIRECTIRECT FOAMINGFOAMING

5

but

excessive coarsening in the wet state due to

• Ostwald ripening (difference in Laplace pressures)Ostwald ripening (difference in Laplace pressures)• drainage• coalescence of single bubbles

6CCOARSENINGOARSENING OFOF SURFACTANTSURFACTANT--STABILIZEDSTABILIZED FOAMSFOAMS

6

∆t = 4h

How can the foam stability be improved?How can the foam stability be improved?

7PPICKERINGICKERING EMULSIONSEMULSIONS

7W. Ramsden. “Separation of solids in the surface-layers of solutions and 'Suspensions'. Preliminary Account.”, Proceedings of the Royal Society, 72[479], 156-164,1903.S. U. Pickering. “Emulsions”, Journal of the Chemical Society, 91, 2001-2021,1907.

http://royalsociety.org

any fine particles are able to stabilize oil-in-water emulsions

Percival Spencer Umfreville Pickering

emulsionsenhanced stability compared to surfactant-stabilized emulsionsp g

(1858 – 1920)

8SSTABILIZATIONTABILIZATION OFOF THETHE AIRAIR--WATERWATER INTERFACEINTERFACE

8

Free energy gain by loosing an area of fluid-gas interface

long-chain surfactants

area of fluid gas interface

particles

i l b f i b hi hili ( j i l )particles can be surface active, but are not amphiphilic (expect janus particles)particles strongly held at interface, enhanced stability of the foam

9PPARTICLESARTICLES ININ MIXTURESMIXTURES OFOF IMMISCIBLEIMMISCIBLE PHASESPHASES

9

Oxides: Polymers:condition to obtainAl2O3, ZrO2, SiO2, Ca3(PO4)2,hydroxyapatite,

Polyethylene (PE),Polyvinyldifluoride ,Teflon (PTFE),

FOAMSor

MISTSor

… …O/W EMULSIONS W/O EMULSIONS

10IINN--SITUSITU HYDROPHOBIZATIONHYDROPHOBIZATION OFOF PARTICLESPARTICLES

10

short-chain amphiphilic molecules as surface modifiers

→ high solubility in water→ high concentration of modified particles→ stabilization of large interfacial area

Gonzenbach et al. Angewandte Chemie-International Edition, 2006.

→ stabilization of large interfacial area

1111

TTHEHE FOAMINGFOAMINGPROCESSPROCESS

12SSTABILITYTABILITY OFOF THETHE WETWET FOAMSFOAMS

12

Gillette razor foam

our foams

100μm100μm100μm100μm

Suspension homogeneously foamed throughout the whole volumeImproved wet foam stability compared to state-of-the-art foams

Gonzenbach et al., Journal of the American Ceramic Society, 2007.

5µm

50µm

FFOAMOAM PROCESSINGPROCESSING

1 21 2

suspension foamingpreparation

g

3 4

drying sintering

1515

3cm

1616

100µm

1717

100µm

18PPROPERTIESROPERTIES OFOF POROUSPOROUS ALUMINAALUMINA

18

1919

1µm

20VVERSATILITYERSATILITY OFOF THETHE METHODMETHOD

20

Method can be applied to many different materials, e.g.

Ceramics• Al2O3

• SiO

Metals• Ti

• Al

Polymers• PVDF

• PTFE• SiO2

• ZrO2

• Ca3PO4

• Al

• Ni/Ti

• ...

• PTFE

• PE

• PPCa3PO4

• Cements

• ...

... PP

• ...

1cm 1cm 1cm

CCAPSULEAPSULE PROCESSINGPROCESSING

1 21 2

suspension foamingpreparation

g

3 4

dilution filtration

2222

20µm

2323

2µm

2424

5µm10µm

25PPOTENTIALOTENTIAL APPLICATIONSAPPLICATIONS

25

PPPPLATFORMLATFORMTTECHNOLOGYECHNOLOGYTTECHNOLOGYECHNOLOGY

26FFOAMSOAMS ANDAND EMULSIONSEMULSIONS ATAT ETHZETHZ

26

Ceramic foams Metallic foams Polymeric foams

Ludwig J. Gauckler Jörg F. Löffler Paolo Ermanni

Urs T. Florian StephanElena David Megias- MarioGonzenbach Dalla Torre

pBusatoTervoort

gAlguacil Mücklich

Laboratory of Metal Center of StructureFranziska

KraussAdrienne Nelson Joanna WongIlke

AkartunaPhilip N.

SturzeneggerBen

SeeberNonmetallic Inorganic Materials

Laboratory of Metal Physics and Technology

Center of Structure Technology

KraussAkartuna Sturzenegger Seeber

27AcknowledgmentsAcknowledgments

27

Prof. Dr. Ludwig J. Gauckler, Dr. André R. Studart, Dr. Elena Tervoort

Ilke Akartuna Franziska Krauss Philip Sturzenegger Mario Mücklich

Ambrosini, Jan

Ilke Akartuna, Franziska Krauss, Philip Sturzenegger, Mario Mücklich

Kümin, Cyrill

Bardill, Anita

Bihl, Andreas

Nägeli, Rahel

Seeber, Benedikt

Bonderer, Lorenz

Dietiker, Marianne

Siegfried, Michael

Steinlin, David

Elser, Pierre

Geiser, Valérie

I k B i

Strehler, Claudia

Sturzenegger, Philip

Wi ä hti A dIwanowsky, Boris

Kontic, Roman

Wiprächtiger, Andreas

Funding: ETH Zürich, CIBA, Holcim, CCMX, SPERU

28ThankThank oo !!ThankThank oo !! 28ThankThank youyou!!ThankThank youyou!!

1cm