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P ARTICLE ARTICLE-STABILIZED STABILIZED FOAMS FOAMS AND AND THEIR THEIR POTENTIAL POTENTIAL APPLICATIONS APPLICATIONS Urs T. Gonzenbach Dr. Sc. ETH Nonmetallic Inorganic Materials, Department of Materials, ETH Zü i h S it l d ETH rich, Switzerland

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  • PPARTICLEARTICLE--STABILIZEDSTABILIZED FOAMSFOAMS ANDAND THEIRTHEIRPOTENTIALPOTENTIAL 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