Fantastic Tales of Super CeramicsFantastic Tales of Super Ceramics

Professor M. L. Mecartney

Department of Chemical Engineering and Materials ScienceUniversity of California, Irvine

My Research Group My Research Group Ph.D. StudentsPh.D. Students

Peter DillonPeter Dillon Tiandan ChenTiandan Chen Sungrok Sungrok

BangBang Lynher Lynher

RamirezRamirez

M.S. StudentsM.S. Students Kevin OlsonKevin Olson

Undergraduate Undergraduate StudentsStudents Daniel StricklandDaniel Strickland

(NSF REU)(NSF REU) Joy TrujilloJoy Trujillo (UC (UC

LEADS)LEADS) Jeremy RothJeremy Roth (SURP) (SURP)

External CollaboratorsExternal Collaborators Professor Trudy Professor Trudy

KrivenKriven, University of , University of IllinoisIllinois

Professor Susan Professor Susan Krumdieck, University Krumdieck, University of Canterbury, NZof Canterbury, NZ

How I found ceramic How I found ceramic science, and discovered a science, and discovered a

lifelifeI was once a lowly Classics major, I was once a lowly Classics major,

studying Greek and Latin at Case studying Greek and Latin at Case Western Reserve University….Western Reserve University….

Then I discovered Materials Science and Then I discovered Materials Science and Engineering – Solid State Physics and Engineering – Solid State Physics and Physical Chemistry!!!Physical Chemistry!!!

Undergraduate research on positron Undergraduate research on positron annihilation in alumina (in Physics) and annihilation in alumina (in Physics) and single crystal deformation of ZrOsingle crystal deformation of ZrO22 (in (in MSE)MSE)

Post B.S./B.A. Post B.S./B.A. WanderingsWanderings

Graduate school – M.S. and Ph.D. in Materials Science Graduate school – M.S. and Ph.D. in Materials Science and Engineering at Stanford University (BaTiOand Engineering at Stanford University (BaTiO33 and and SiSi33NN44))

Post-doctoral research – Max-Plank-Institut in Post-doctoral research – Max-Plank-Institut in Stuttgart, Germany (ZrOStuttgart, Germany (ZrO22))

Faculty positions – University of Minnesota, Faculty positions – University of Minnesota, Minneapolis, then University of California, Irvine Minneapolis, then University of California, Irvine (LiNbO(LiNbO33, Pb(Zr,Ti)O, Pb(Zr,Ti)O33, V, V22OO55, , CaO-BCaO-B22OO33-SiO-SiO22, , (Sr,Ba)Nb(Sr,Ba)Nb22OO66, etc.), etc.)

Fantastic CeramicsFantastic Ceramics

Did you know that ceramic conductors Did you know that ceramic conductors are a critical part of fuel cell are a critical part of fuel cell technology?technology?

Did you know that ceramics can be Did you know that ceramics can be stronger than any other material?stronger than any other material?

Did you know that ceramics can be Did you know that ceramics can be deformed just like metals?deformed just like metals?

Did you know that ceramics can conduct Did you know that ceramics can conduct electricity without any resistance?electricity without any resistance?

Super CeramicsSuper Ceramics

Super ionic conductors for fuel cellsSuper ionic conductors for fuel cells Super strong ceramics for cutting Super strong ceramics for cutting

applications applications Super plastic ceramics for net shape Super plastic ceramics for net shape

formingforming NO CERAMIC NO CERAMIC

SUPERCONDUCTORS IN THIS TALK SUPERCONDUCTORS IN THIS TALK

CERAMICSCERAMICS A ceramic is a compound composed A ceramic is a compound composed

of at least one metallic and non-of at least one metallic and non-metallic element metallic element

Ionic/covalent bondingIonic/covalent bonding

Most Ceramics are Most Ceramics are CrystallineCrystalline

ZrO2 NaCl

Typical Grain / Grain Boundary Typical Grain / Grain Boundary StructureStructure

H.L. Tuller: “Ionic conduction in nanocyrstalline materials.” Solid State Ionics 146, 157 (2000).

Ceramics as Ceramics as Ionic ConductorsIonic Conductors

Loade

Depleted fuel andproduct gases out

Depleted oxidant andproduct gases out

SOFCH2

H2OO O2

PEMFC andPAFC

H2 H2O

O2H+

MCFC

H2

CO2H2O

CO3 CO2

O2

Fuel in Oxidant in

Anode CathodeElectrolyte

(ion conductor)

OVERVIEW OF FUEL CELL TYPES

From Dr. Jack Brouwer NFCRC

Brick Layer ModelBrick Layer Model

Polycrystalline Material Model Equivalent Circuit Model

Modified From S M. Haile, D L West, and J. Campbell, J .Mater. Res. vol 13, pp.1576-1595 (1998).

AFM of YSZ Film on AFM of YSZ Film on Al2O3Al2O3

R.M. Smith, X.D. Zhou, W. Huebner, and H.U. Anderson (2004), "Novel Yttrium-Stabilized Zirconia Polymeric Precursor for the Fabrication of Thin Films," Journal of Materials Research, 19, 2708-2713.

15X Conductivity15X Conductivity IncreaseIncrease in Nano-crystalline Zirconia!in Nano-crystalline Zirconia!

H.L. Tuller: “Ionic conduction in nanocyrstalline materials.” Solid State Ionics 146, 157 (2000).

Increase in GB Increase in GB ConductivityConductivity

X. Guo and Z.L. Zhang (2003), "Grain Size Dependent Grain Boundary Defect Structure: Case of Doped Zirconia," Acta Materialia, 51, 2539-2547.

Propoxide Sol-Gel TF PreparationPropoxide Sol-Gel TF Preparation

Yttrium Isopropoxide

ScandiumIsopropoxide

Zirconium Propoxide

Hydrolysis:70wt% HNO3, 30 wt% H2O

Spin Coat on Si / Al2O3 Substrate 2000RPM, 45s

Bake à Pyrolize + Crystallize

Solution in Isopropanol à 0.2M Alkoxide Concentration

SEM Characterization:Grain Size + Film Thickness

TEM Characterization:Grain Size + Composition

Glancing Incidence XRD (GID):Grain Size + Crystal Structure

Impedance Spectrometry:Ionic Conductivity à Bulk / Grain / Grain Boundary

Stabilizer Conc (mol%): 4Y / 8Y / 4Sc / 8Sc / 4Y:4Sc

Polymer Precursors

CharacterizationPreparation

DSC / TGA AnalysisàDetermine Tvap - Tpyrolysis – Tcrystallization

Evaporate Alcohol / H2O

Acetate Sol-Gel TF PreparationAcetate Sol-Gel TF Preparation

Yttrium Acetate

ScandiumAcetate

Zirconium Acetate

Hydrolize with Ethylene Glycol

Spin Coat on Si / Al2O3 Substrate 3000RPM, 60s

Evaporate Alcohol à Form Gel

Bake à Pyrolize + Crystallize

Solution in MethanolSEM Characterization:

Grain Size + Film Thickness

TEM Characterization:Grain Size + Composition

Glancing Incidence XRD (GID):Grain Size + Crystal Structure

Impedance Spectrometry:Ionic Conductivity à Bulk / Grain / Grain Boundary

Stabilizer Conc (mol%): 4Y / 8Y / 4Sc / 8Sc / 4Y:4Sc

Polymer Precursors

CharacterizationPreparation

Add GPC to Allow Process to Be Carried Out in Open Air

Adjust Viscosity à Add Methanol to 20 cP

DSC / TGA AnalysisàDetermine Tvap / Tpyrolysis / Tcrystallization

Adapted From: R.M. Smith, X.D. Zhou, W. Huebner, and H.U. Anderson (2004), "Novel Yttrium-Stabilized Zirconia Polymeric Precursor for the Fabrication of Thin Films," Journal of Materials Research, 19, 2708-2713.

Multiple Spin Coated LayersMultiple Spin Coated Layers(Ba-Ti on Si Wafer)(Ba-Ti on Si Wafer)

M.C. Gust, N.D. Evans, L.A. Momoda, and M.L. Mecartney, "In-Situ Transmission Electron Microscopy Crystallization Studies

of Sol-Gel Derived Barium Titanate Thin Films," J. Am. Ceram. Soc. 80 [11] 2828-36 (1997).

Cross Sectional SEM Cross Sectional SEM ZrOZrO22 Thin Film on Si Wafer Thin Film on Si Wafer

Typical Grain Size of Typical Grain Size of ZrOZrO22

Burning QuestionsBurning Questions

Will our nanocrystalline zirconia Will our nanocrystalline zirconia thin films be a super ionic conductor thin films be a super ionic conductor when compared to zirconia with a when compared to zirconia with a larger grain sizes?larger grain sizes?

And why?And why?

Stay tuned for Daniel Strickland’s Stay tuned for Daniel Strickland’s talk at the end of the summer!talk at the end of the summer!

High Strength High Strength CeramicsCeramics

50%Al2O3-25%NiAl2O4-25%ZrO2

Fine Grain Ceramics Are Fine Grain Ceramics Are Strong, But…Strong, But…

At high temperatures, the smaller the At high temperatures, the smaller the grain size, the easier to deform a grain size, the easier to deform a material (creep).material (creep).

These materials were developed to be These materials were developed to be high speed cutting tools, the tips of high speed cutting tools, the tips of which may reach 1500°C.which may reach 1500°C.

Will creep be a problem????Will creep be a problem????

Compression Test Compression Test ResultsResults

0

0. 1

0. 2

0. 3

0. 4

0. 5

0. 6

0. 7

0 5000 10000 15000 20000 25000 30000 35000

Time (s)

Tru

e S

trai

n

50%Al2O3-25%NiAl2O4-25%TZP @ 1425C50%Al2O3-25%NiAl2O4-25%TZP @ 1350C

50% Al2O3-25%NiAl2O4-25%TZP

Undeformed

Average Grain Size (m)

Al2O3: 0.76

NiAl2O4 : 0.49

TZP: 0.42

50% Al2O3-25%NiAl2O4-25%TZP

Deformed at 1425°C

Average Grain Size (m)

Al2O3: 1.39

NiAl2O4 : 0.81

TZP: 0.62

Stress ResponseStress Response

1. E-06

1. E-05

1. E-04

1. E-03

10 100

Stress (MPa)

Str

ain

Rat

e (1

/s)

50%Al2O3-25%NiAl2O4-25%TZP @ 1425C50%Al2O3-25%NiAl2O4-25%TZP @ 1350C

Fine Grain Ceramics May Fine Grain Ceramics May be Super Strong at Room be Super Strong at Room

Temperature…Temperature…

…….but very deformable and .but very deformable and soft at high temperatures.soft at high temperatures.

Superplastic Superplastic CeramicsCeramics

SuperplasticitySuperplasticity The ability of polycrystalline solids to exhibit greater than 100% eloThe ability of polycrystalline solids to exhibit greater than 100% elo

ngation in tension, usually at elevated temperatures about 0.5Tngation in tension, usually at elevated temperatures about 0.5Tm m

Constitutive Law Constitutive Law

Where: έ Strain rate Q Activation energy σ Stress Rg Gas constant n Stress exponent T Temperature (K) d Grain size p Grain size exponent

RT

Q

dA

p

n

expε J.Wakai, J.Wakai, Adv. Ceram. Mater., Adv. Ceram. Mater., 19861986

Applications Applications SPF enables net-shape-forming, fabricate unique complex shaSPF enables net-shape-forming, fabricate unique complex sha

pes from a single piece of materials;pes from a single piece of materials; Eliminates parts and process steps, minimizes manufacturing cEliminates parts and process steps, minimizes manufacturing c

ost.ost. Ceramic knives are made by superplastic forming in Japan.Ceramic knives are made by superplastic forming in Japan.

ExamplesExamples

Y-TZP @1450℃ Kyocera Ceramic Knife

Superplastic DeformationSuperplastic Deformation

Grain boundary slidGrain boundary slidinging

Sudhir, Chokshi, J.Am.Ceram.Soc., 2001

Simulation of Grain Boundary Sliding during deformation

0% SiO2, d=10.2µm 1 wt% SiO2, d=2.8µm 3 wt% SiO2, d=1.7µm

5 wt% SiO2, d= 1.6µm 10 wt% SiO2, d=1.2µm

Grain Size 8Y-CSZ Grain Size 8Y-CSZ Sintered 2 hours at Sintered 2 hours at

16001600ºCºC

A Superplastic CeramicA Superplastic Ceramic8 mol% Y8 mol% Y22OO33 Cubic Stabilized ZrO Cubic Stabilized ZrO2 2 + 5 wt.+ 5 wt.

% SiO% SiO22

Optimal Microstructure Optimal Microstructure for Superplasticityfor Superplasticity

The smaller the grain size, the easier The smaller the grain size, the easier to achieve superplastic deformation.to achieve superplastic deformation.

But during high temperature But during high temperature deformation, grains grow to deformation, grains grow to minimize grain boundary interfacial minimize grain boundary interfacial area.area.

Need to design a material in which Need to design a material in which grain growth is limited.grain growth is limited.

How to Create a Stable Fine Grain How to Create a Stable Fine Grain Structure at High TemperaturesStructure at High Temperatures

Grain growth is rapid in single phase materials, slower in two phase materials (zirconia – silica), but should be very limited in a three-phase microstructure

Two-phase structure Three-phase structure

II. II. Experimental ApproachExperimental Approach

Al2O3

(40nm)ZrO2

(26nm)SiO2 Sol(15nm)

Ball Milling

Dry, Sieve and Press

Sintered at 1450℃Compressive Deformation

XRD, SEM, TEM EDS Analysis

3Al2O3 + 2SiO2 = 3Al2O3•2SiO2

Multiphase ceramic Alumina – Zirconia – Mullite

Nanocrystalline Ceramic with Alumina, Mullite, Zirconia

SEM of AZ30M30

0 20 40 60 80 1001E-5

1E-4

1E-3

AZ30M30 AZ15M15 AZ10M10 AZ30

Tru

e S

tra

in R

ate

(/s

)

True Strain (%)5.0 5.2 5.4 5.6 5.8 6.0 6.2

10-5

10-4

10-3

10-2

10-1

100

101

Calculated strain rate

1 s-1 at 1650

0C

Tru

e S

trai

n ra

te (

s-1)

Inverse Temperature (10000/T)

Deformation Behavior

Steady-state deformation of AZ30M30 High strain rate of AZ30M30

Dislocations generated during deformation

AZ30M30 Deformed Mullite Grain

ConclusionsConclusions

1. Nanocrystalline/fine grain ceramics 1. Nanocrystalline/fine grain ceramics maymay be be supersuperior iior ionic conductors (increased efficiency for fuel cells).onic conductors (increased efficiency for fuel cells).

2. Nanocrystalline/fine grain ceramics have 2. Nanocrystalline/fine grain ceramics have supersuperior streior strength at room temperature.ngth at room temperature.

3. Nanocrystalline/fine grain ceramics behave like metal3. Nanocrystalline/fine grain ceramics behave like metals at high temperatures, but this may be useful for s at high temperatures, but this may be useful for supesuperplasticrplastic forming. forming.

Thanks to the Following Thanks to the Following for Research Supportfor Research Support

NSF Division of Materials Research NSF Division of Materials Research National Fuel Cell Research CenterNational Fuel Cell Research Center NSF REU programNSF REU program UCI SURP programUCI SURP program UC LEADS programUC LEADS program Pacific NanotechnologyPacific Nanotechnology Corona Naval BaseCorona Naval Base