introduction (1)- ceramics? · introduction 2- mechanical spectroscopy high temp. mechanical...

4/1/2011

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GSMGSM

Processing of Nanostructured Ceramics:

Shaping, Sintering and Properties

Mehdi Mazaheri

Nov 2009

Introduction - Ceramics?

low density, low sensitivity to corrosion, high rigidity and hardness even at high temperature

Introduction (1)- Ceramics?

Toughening Mechanism in Ceramics

Crack deflection Peng et al., J. Am.Cerm.Soc., 1988

Introduction (1)- Ceramics?

Toughening Mechanism in Ceramics

(1) Crack deflection(2) Crack bridging (3) Fibers pullout

(1) Crack blunting(2) Crack bridging

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Xia et al, Acta Materialia, 2004. Zhang et al., Nature Materials, 2003

Jiang et al, Scripta Materialia, 2007

Introduction (1)- Ceramics?Grain refining

High temperature mechanical properties

Increasing of fracture toughness

(G.B. sliding accommodated by diffusion or interface reaction mechanisms)

gat room temperature

Nano‐structured ceramics reinforced by nano‐particles or fibers

3 times higher fracture toughness (Zhang et al, Nature Materials, 2003)

Higher creep resistance (Ionascu, EPFL Thesis, 2008)

Interest on Nanostructured Ceramics

Functional Ceramics Structural Ceramics

Krell et al, J. Am. Cerm. Soc, 86 (2003) 546.

From: Nanopowders

Shaping

• Problems

Prosity

In-homogeneity

To:

Nanostructured

Sintering ؟؟Mazaheri et al., J. Am. Ceram. Soc, 2008 (1) 5

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Shaping?

Shaping?

Sintering of n-3Y.TZPMaster Sintering Curve

20 30 40 50 60 70

Tetragonal

Monoclinic

Inte

nsity

2 Theta, o

Non-Isothermal Sintering

(Dillatometric Study)

-12

-8

-4

0

in, %

(a)

0.7

0.8

0.9

1.0

20 K min-1

5 K min-1

nal d

ensi

ty

2 K min-1

gs TTLdLρ

αρ

3

00 )(/11

⎥⎥⎦

⎤

⎢⎢⎣

⎡

−+−=

700 800 900 1000 1100 1200 1300 1400-28

-24

-20

-16

20 K min-1

5 K min-1

2 K min-1

Temperature, οC

Stra

1050 1100 1150 1200 1250 1300 13

0.5

0.6Frac

tio

Temperature, oC

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+0.9

1.0

Master Sintering Curve for n‐3Y.TZP

-21 -20 -19 -18 -17 -160.4

0.5

0.6

0.7

0.8

Frac

tiona

l den

sity

Log θ

Sintering of n-3Y.TZPMechanical behaviour

HARDNESS

Sintering of n‐3Y.TZPMechanical behaviour

Fracture Toughness

Grain Growth S i

Spark Plasma Sintering

(SPS)

Pressure Assisted Sintering

Phase Transformation

Assisted

Using Additives

Effect of Sintering Techniques

Suppression(HP & HIP)

Millimeter and Micro Wave Sintering

Two-step Sintering

(TSS)

Two-step Sintering

(TSS)

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Ng Two Step Sintering

Nano Ceramics ReferencesYttria Chen et al. , NatureZinc Oxide Mazaheri et al J Am Ceram

Simple! Physically Powerful!

Zinc Oxide Mazaheri et al., J. Am. Ceram. Soc.

Alumina Bodisova et al., J. Am. Ceram. Soc.

ZnO Varistors Duran et al. J. Am. Cerm. Soc.YAG Chen et al., Ceram. Int. Tetragonal Stabilized Zirconia (3Y-TZP)

Mazaheri et al., J. Eur. Cer. Soc.

Ba TiO3 Wang et al., J. Am. Ceram. Soc.Titania Mazaheri et al., Scripta Mat.

Second Step; T2

First Step; T1

Time

Tem

pera

ture

Chen et al, Nature, 2000

Grain Growth Suppression

Effect of ShapingTechniquesExperimental:

Raw Material

Shaping

SEM-TEM

BET

XRD

UP, CIP, Slip casting

3Y‐TZP (~75 nm)

Alumina (80‐150 nm)

8YSZ (15‐33 nm)

HA(~93 / ~24 nm)

ZnO (20‐40 nm)

PMN (<100 nm)

Titania (15 nm)1) Conventional sintering (Non-isothermal and Isothermal)

Cold pressing CIP Wet shapiping method

Sintering

Mechanical properties

Microstructural Observation

1. Mechanically Polished Using Diamond Pastes

2. Thermally Etched

3. Intercept Linear Method

isothermal and Isothermal)

2) Two-step sintering

3) Phase transformation sintering

4) Hot pressing

5) Microwave sintering

Sintering of n-ZnOCS-TSS and HP

Conventional Sintering of n-ZnO

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2 Step Sintering of n-ZnO

DiscussionSummarizes Results of TSS

Hot Pressing of n-ZnO

Application?

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Sintering of n-TitaniaCS,TSS and assisted by phase-transformation

Sintering of n-TitaniaCS,TSS and assisted by phase-transformation

Compaction Behavior ؟؟

Processing of 8YSZSintering methods: CS, TSS and Microwave Sintering

Shaping methods: Uniaxial pressing, Slipcasting

Processing of 8YSZShaping methods: Uniaxial pressing, Slipcasting

0 52

0.56

0.60

Solid Load (wt%)

Dry Pressing

nsity

0.45 0.50 0.55 0.60 0.65

Slip Casting

0.95

1.00

nsity

80

100

%)

100 1000

0.32

0.36

0.40

0.44

0.48

0.52

Pc (Critical Pressure ~600 MPa)

Py (Agglomerates Strength ~370 MPa)

Frac

tiona

l Gre

en D

en

Applied Pressure (MPa)

0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50

0.75

0.80

0.85

0.90

Dry Pressing Slip Casting

Frac

tiona

l Fire

d D

en

Fractional Green Density0 50 100 150 200 250 300 350 4000

20

40

60

Dry PressingSlip Casting

Frac

tiona

l Vol

ume

(%

Pore Diameter (nm)

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Processing of 8YSZSintering methods: CS, TSS, MS

Processing of 8YSZSintering methods: CS, TSS, MS

Processing of 8YSZMicrostructure and Mechnical behaviour

CS LMS

HMS TSS

؟

Conclusion 1

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Spark Plasma Sintering

&

Thermo-Mechanical Properties

Spark plasma sintering P

Graphite dieGraphite die

SamplePulsed DC

The first SPS unit in Europe, Dr Sinter 2050, installed in 1998

P

SPS ≥ HP

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Pressure effectPressure effect

Sintering or packing?

⎟⎠⎞

⎜⎝⎛ +⎟⎟⎠

⎞⎜⎜⎝

⎛ Ω=

Δ−r

PkTG

Ddt

LLd sva

gbgb γφδ3

0

295)/(

For Coble creep based grain boundary sliding

in intermediated stage

⎠⎝

⎟⎠⎞

⎜⎝⎛ +⎟⎟⎠

⎞⎜⎜⎝

⎛ Ω=

Δ−r

PkTG

Ddt

LLd sva

gbgb γφδ 2

215)/(

30

in final stage

Dgb : GB diffusion coefficient, δgb : GB width, Ω : atomic volume, G : grain size, k : Boltzmann constant, T : the absolute temperature, γsv is the solid-vapour surface energy, r : pore size. pa : applied stress.

600

650

700

696ºC

500 nm

prior to

Strain rate: 10-5 s-1

MgO Superplasticity⎯ Grain boundary sliding

0.3 Tm vs 0.5Tm

0 5 10 15 20 25 30 35 400

50

100

150

200

250

300

350

400

450

500

550

796ºC

756ºC

Stre

ss (M

Pa)

Strain (%) 500 nm

after

Compressive deformation under constant cross-head speed

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0,006

0,008

0,010

P always on

100MPa 75MPa 50MPa25MPao)

/dt (

s-1)

Strain rate: >10-3 s-1

Grain sliding Diffusion

Densification rate

40 50 60 70 80 90 1000,000

0,002

0,004

25MPa

Relative Density

-d(Δ

L/L

o

0,010

⎟⎠⎞

⎜⎝⎛ +⎟⎟⎠

⎞⎜⎜⎝

⎛ Ω=

Δ−r

PkTG

Ddt

LLd sva

gbgb γφδ3

0

295)/(

in intermediated stage

⎟⎠⎞

⎜⎝⎛ +⎟⎟⎠

⎞⎜⎜⎝

⎛ Ω=

Δ−r

PkTG

Ddt

LLd sva

gbgb γφδ 2

215)/(

30

in final stage

Intermedialte stage, 32%≤ Vp ≤ 10%, no linear relationFinal stage, Vp ≤ 10%, no linear relation

40 50 60 70 80 90 1000,000

0,002

0,004

0,006

0,008

P always on

100MPa 75MPa 50MPa 25MPa

Relative Density

-d(Δ

L/L

o)/d

t (s-1

)

0.015

0.020P at Tf

100P 75P 50P 25P

dt (s

-1)

Densification rate:P at Tf

Strain rate: 10-2 s-1

40 50 60 70 80 90 100

0.000

0.005

0.010

Relative Density

-d(Δ

L/L

o)/d

90

95

100

Den

sity

[%]

92

96

100

900

1100

1300

1500

Den

sity

[%]

Grain Siz

Consolidating YAG under high pressure

80

85

1100 1200 1300 1400 1500 1600

100 MPa - 3 min100 MPa - 6 min 50 MPa - 3 min

Rel

ativ

e D

SPS Temperature [oC]

80

84

88

100

300

500

700

1200 1300 1400 1500 1600

Rel

ativ

e D ze [nm

]

SPS Temperature [oC]

34 nm nc-YAG@ 100 MPa / 3 min

Spherical powder, 34 nmJ. of Euro Ceram. Soc. (2007) , 27(11), 3331-3337

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Densification while retarding solution-reprecipitation

Bright-field TEM image, beta-powder, grain size: 76 nm, SPS 1500oC under 50 MPa for 3 min. Note the aggregate feature of the large grains.

Introduction (2)- Ceramics?Grain refining

High temperature mechanical properties

Increasing of fracture toughness

(G.B. sliding accommodated by diffusion or interface reaction mechanisms)

gat room temperature

Nano‐structured ceramics reinforced by nano‐particles or fibers

3 times higher fracture toughness (Zhang et al, Nature Materials, 2003)

Higher creep resistance (Ionascu, EPFL Thesis, 2008)

Motion of structural defects…Introduction 2- Anelasticity

Standard anelastic solid model

Introduction 2- Mechanical spectroscopy

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Introduction 2- Mechanical spectroscopy High temp. mechanical behavior

Crystallization in glassy phase

Crystallization in glassy phase

Onset of creepMechanical spectroscopy

* Forced torsion pendulum in sub‐resonant mode * Temperature: RT‐ 1600 K* Frequency: 10‐4 and 10 Hz* Vacuum: 10‐3 Pa

Introduction (3) –Application of M.S. in ceramics

High‐temperature plasticity of finefine‐‐grainedgrained ceramicsceramicsproceedsproceeds byby mutually accommodating graingrain boundaryboundary slidingslidingand diffusiondiffusion creepcreep..

Diffusion processes are:‐‐ NabarroNabarro‐‐Herring creep Herring creep ‐‐ Coble creepCoble creep

Grain boundary sliding createsvoids or overlaps that have to beaccommodated by diffusion.

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First results (2) – 3Y.TZP33YY‐‐TZPTZP

Donzel et al, Acta Mater. 2000

Theoretical model for GB slidingTheoretical model for GB sliding

Lakki’s model for GB slidingLakki’s model for GB sliding

tan φ( )ω=ωp=

GKG

ωp =δη

KGd

+ K 2

p

2d KGd

+ K 2

Lakki’s model for GB slidingLakki’s model for GB sliding

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What is the aim of this work?

Yttria Stabilized Zirconia (3Y.TZP)

Silicon nitride based ceramics (SiAlON)

Spark plasma sintering (SPS)

Two‐step sinteirng

SPS apparatus in Lyon

Materials

Hot Press & Spark Plasma Sintering

2073 K, 35 MPa and 4 h

Ca‐SiAlON(Si3N4, AlN, CaO)

Y‐SiAlON Yb‐SiAlON

CO04 CO14

CaxSi12‐3xAl3xOxN16‐xx=0.4, 1.4

YO04 YN04

(Si3N4, AlN, Y2O3/YN)

YbO04 YbN04

(Si3N4, AlN, Yb2O3/YbN

Ca‐SiAlON(Si3N4, AlN, CaH2)

CN04 CN08 CN16

Materials

Hot Press & Spark Plasma Sintering

1773 K, 50 MPa and only 3 min

Si3N4 + 6wt% Al2O3 + 6wt% Y2O3

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Si3N4 based ceramics20x10-3

15

1.00

0.98

0.96

0.94

Relative m

o

YO04 Heating

Cooling

Y40

softening

crystallization

10

5

0

tan

(φ)

150014001300120011001000

Temperature (K)

0.92

0.90

0.88

0.86

odulas (arb. units)

Lakki et al, Acta. Mater., 1995.

Si3N4 based ceramics

10x10-3

8

6

4

2

tan(φ)

1025 K 1050 K1075 K

1.00

0.99

0.98

0.97

0.96

Rel

ativ

e m

odul

us

1025 K 1050 K 1075 K

0

0.01 0.1 1

Frequency, Hz

1075 K 1100 K 1125 K

0.95

0.01 0.1 1

Frequency, Hz

1100 K 1125 K

0.88 0.89 0.90 0.91 0.92 0.93 0.94 0.95 0.96

0.01

0.1

1

Freq

uenc

y, H

z

T -1, K-1

Si3N4 based ceramics(CO04 and CO14)

Same microstructureSame chemical composition of glassy phase

Higher glassy phaseHigher amount

of glassy phase

(Y4O and Y4N)

Y4O

Effect of N/O ratio on glassy phase

Hig

her a

mou

nt

of g

lass

y ph

ase

1. Equiaxed grains (as same!)2. Grain size (as same!)

Y4N

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YbO04 (Si3N4 + AlN + Yb2O3)YbN04 (Si3N4 + AlN + YbN)

Results (Yb4O and Yb4N)


CN04

CN08

35x10-3

30

25

20

15

tan

(φ)

Ca2N Ca4N Ca8N Ca16N

10

5

0

1300125012001150110010501000

Temperature, K


0.3

0.4

Ca16N Ca8N Ca4N

1500 1550 1600 1650 1700 1750

0.0

0.1

0.2 -ΔL/

L 0

Temperature,oC


• Real Si3N4 system

To be published in Acta Materialia

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70x10-3

60

50

40

(φ)

Pure glass


composition

30

20

10

0

tan

150014001300120011001000

Temperature (K)

Higher restoring force

Tg

Results

Mechanical loss spectrum of Si3N4 Processed via SPS

3Y.TZP

0.35

0.30

0.25 F= 1 HzHeating rate = 1 K/min As received SU

Pure zirconia + conventional sinteirng Pure zirconia + sparka plasma sinteirng

0.20

0.15

0.10

0.05

Tan

(φ)

1600140012001000800600400200

Temperature (K)

First results (2) – 3Y.TZP

0.35

0.30

0.25

F= 1 HzHeating rate = 1 K/min As received SU (1) Pure zirconia

(2) 3Y-TZP + 3 wt% CNTs0.20

0.15

0.10

0.05

tan

(φ)

14001300120011001000900800 Temperature (K)

( ) (3) 3Y-TZP + 3 wt% CNTs (2ed test) + 30h anneal

(1) (2)

(3)

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3Y.TZP

A ‐material constantσ – constant applied stressG – shear modulusb – Burger vectord – grain size ΔHact – activation enthalpy (characteristic

for underlying mechanism)R – universal gas constant

Power law equation of creepPower law equation of creep

6

100

2

3

456

n(Φ) x

100

0

Power law equation of creepPower law equation of creep

T=1600 KT=1575 KT=1550 KT=1525 KT=1500 K

2

3

456

tan

4.03.02.01.00.0-1.0-2.0-3.0Ln(Frequency)

Grain growth?Grain growth?

( )( ) ( ) 1tan( ) tan log tan log log( )(10)act

oH

R ln Tωτ ω τ

⎛ ⎞⎡ ⎤Δ⎡ ⎤Φ = Φ = Φ + +⎜ ⎟⎢ ⎥⎣ ⎦ ⋅⎣ ⎦⎝ ⎠

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Grain growth?Grain growth?

Movement in Y direction

-0.00008 -0.00006 -0.00004 -0.00002 0.00000

0

1

2

3

4

5

6

7

ΔΗact= 617 kJ.mol-1

Δ lo

g (f)

Δ T-1

3YTZP + 3 wt% CNTs As received SU

0.195

0.200

0.205

0.195

0.200

0.205

size

0 1x104 2x104 3x104 4x104 5x104

0.175

0.180

0.185

0.190

Tan

(φ)

Holding time (s)

3YTZP + 1.5 wt% CNTs Heating rate = 1 K/min As received SUSoaking temperature = 1600 k

0 1x104 2x104 3x104 4x104 5x104

0.175

0.180

0.185

0.190

Gra

in s

Tan

( φ)

Holding time (s)

3YTZP + 1.5 wt% CNTs Heating rate = 1 K/min As received SUSoaking temperature = 1600 k

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d d0

-1.580.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4

Log (anealing time (h))

Slope = p/n = -0.319

-1.74

-1.72

-1.7

-1.68

-1.66

-1.64

-1.62

-1.6

Log

(tan

(�))

3Y-TZP + 1.5% CNTsAs received

Aneal temperature = 1600 K

Creep model:Interface‐reaction, p=1, n=3

This model to be submitted by end of year

What is the plan for future?Is the model correct?

TEM observation

Creep test

Si3N4 3Y.TZP

1- More investigation on SPS results

2- Different additivesand microstructures

Processing new nano-CMCs by1- grow up CNTs directly (in collaboration with Dr. Magrez)

2- application of TSS and SPS (in collaboration with Prof. Shen and Prof. Fantozzi)

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Acknowledgment

Prof. R. SchallerDr. Daniele MariProf. Z. Shen Prof. G. FantozziDr. C. Yanbing

Les Brenets Border of Switzerland-France

Thanks for you attention

Les Brenets Border of Switzerland-France

introduction (1)- ceramics? · introduction 2- mechanical spectroscopy high temp. mechanical...

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