Application of Master Sintering Curve Theory To Predict And Control Nano-Crystalline Ceramic Sintering

Kevin G. Ewsuk, Christopher B. DiAntonio,Donald T. Ellerby, and Denise N. Bencoe

Sandia National LaboratoriesAlbuquerque, NM 87185-1340

Sintering 2003 3rd Intl Conf on the Science, Technology, & Applications of Sintering

September 14-17, 2003University Park, PA

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company for the US Department of Energy under contract No. DE-AC04-94AL8500

A Science-Based Approach Can Be Used To Improve Process Control

The Problem: Processing defects impact manufacturing cost, and component performance and reliability

Science-Based ProcessingForm -> SinterTechnical Solution:

Apply fundamental scientific understanding to design reproducible processes to manufacture high performance and reliability ceramics

• characterization• predictive modeling

Form -> Sinter -> Grind ($$’s)Traditional Processing

Characterization & ModelingAre Advancing Sintering Science

Free sintering of zinc oxide with different green densities.

-0.05

0

0.05

0.1

0.15

0.2

0.25

500 600 700 800 900 1000

Temperature (C)

47% Green Density57% Green Density

500 600 700 800 900 1000

rgreen= 57%

rgreen= 47%

Temperature (°C)

0.0

0.1

0.2 ZnOSintering

Shrink

age

0.893

0.910

0.926

Relative DensityBilayer Sintering Simulation

0.1%3.8883.89W4.790 mm

1.123Hl1.308 mm

1.2%1.001

2.15 mm

Hu1.323 mm

4.0%6.4316.7 mmL8.049 mm

∆ModelExperiment

Modeling• Master Sintering Curve Theory• 3D FE Modeling• Microstructure Modeling

Validation

L

W

Hl

Hu

Bilayer Sintering Experiment

Sintering Model Validation

Characterization• Shrinkage (non-contact video)• Shape Deformation (in-situ)• Constitutive behavior• Pore Characteristics (NMRI)

Densification Can Be PredictedAnd Controlled With The MSC

55

65

85

95

10 10-22 10-20 10-18

θ

AKP53 AluminaQ = 566 kJ/mole55

65

75

85

95 1100 1200 1300 1400 1500

Den

sity

(%)

Master Sintering CurveDensity vs. θ(t,T(t))

1T0t∫ exp(−

QRT)dt θ(t,T(t))=

J. Am. Ceram. Soc., 79 [12] 3211-17 (1996) (t,T(t))

Temperature (°C)

75

Den

sity

(%)

The MSC Offers Processing,Microstructure, & Property Control

1Tot∫ exp(−

QRT)dt ≡ ρ ≡

kγΩDo

(G(ρ))n

3ρΓ(ρ)ρ o

ρ∫ dρSintering TimeAnd Temperature

Microstructure & Materials Properties

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

1E-20 1E-19 1E-18 1E-17 1E-16Theta [log (sec/K)]

Den

sity

(g/c

c)

Average MSC

5oC/min, 750oC

DuPont 951 Green Tape™

2.45 g/cc

5oC/min, 950oC

3.14 g/cc

5oC/min 800oC

2.95 g/cc

2.00 g/cc

5oC/min, 700oC

1.90 g/cc

Two Different ZnO CeramicPowders Were Examined

Nano-Crystalline ZnO Micro-Crystalline ZnO

600 nm 600 nm

790 nm average particle size3.2 m2/g specific surface area

48 nm average particle size30 m2/g specific surface area

The ZnO Powders WereGranulated, Pressed, And Sintered

Micro-Crystalline ZnONano-Crystalline ZnOSpray Granulated (CBM)

3 Wt% 50:50 PVA:PEG

Sieved>45µm to <150 µm

Dry Pressed (5 x 6 x 50 mm bars)18 MPa uniaxial210 MPa Isostatic

Binder Burned outRT - 600°C in Air

Sintered (4 x 5 x 10 mm bars)5, 10, 20, or 30°C/min to 1550°CNetzsch Dilatometer 402

Pan Granulated3 Wt% 50:50 PVA:PEG

Ground and Sieved<150 µm

Dry Pressed (6 x 6mm dia pellets)140 MPa uniaxial210 MPa Isostatic

Binder Burned outRT - 600°C in Air

Sintered5, 10, 20, or 30°C/min to 1550°CNetzsch Dilatometer 402ED

62% TD ZnO Powder CompactsSintered To Greater Than 91% TD

Micro-Crystalline ZnONano-Crystalline ZnOCompact Density (w/o binder)

62.2 ± 0.0% TD

Sintered Density91.3 ± 0.3% TD

Compact Density (w/o binder)62.6 ± 0.0% TD

Sintered Density99.2 ± 0.2% TD

Sintered Density Was Determined From Measured Linear Shrinkage

Nano-Crystalline ZnO

0.86

0.92

0.98

500 600 700 800 900 1000 1100Temperature (°C)

Line

ar S

hrin

kage

30°C/min20°C/min10°C/min

3.5

4.0

4.5

5.0

5.5

6.0

500 600 700 800 900 1000 1100Temperature (°C)

Den

sity

(g/c

c)

30C/min20C/min10C/min

dLLdt

=dρ3ρdt

Nano-Crystalline ZnO SintersFaster Than Micro-Crystalline ZnO

Crystalline ZnO sintering

3.5

4.0

4.5

5.0

5.5

500 600 700 800 900 1000 1100Temperature (°C)

Den

sity

(g/c

c)

30C/min20C/min10C/min

3.5

4.0

4.5

5.0

5.5

700 800 900 1000 1100 1200

Den

sity

(g/c

c)

Temperature (°C)

Nano

Micro

A Consistent Activation Energy (Q) Was Determined For ZnO Sintering

Micro-Crystalline ZnO*Nano-Crystalline ZnOQ for Densification (65-90%TD)

296 ± 21 kJ/moleQ for Densification (65-90%TD)

268 ± 25 kJ/mole

4.9 g/ccy = -31926x + 33.6

5.0 g/ccy = -31995x + 32.7

4.8 g/cc y = -36855x + 38.8

5.1 g/ccy = -40266x + 38.5

2.5

3.0

3.5

4.0

4.5

5.0

5.5

0.00084 0.00088 0.00092 0.00096LN(d

P/dT

* H

eati

ng R

ate

* T

(Kel

vin/

min

)

1/T (Kelvin-1)

Q = slope * R

Q = 276 ± 13 kJ/mole Gupta & Coble - J Am Ceram Soc 1968

A Master Sintering Curve Was Constructed For Micro-Crystalline ZnO

3.5

4.0

4.5

5.0

5.5700 800 900 1000 1100 1200

Den

sity

(g/c

c)

Temperature (°C)

10°C/min

20°C/min30°C/min

3.0

3.5

4.0

4.5

5.0

5.5

10-18 10-16 10-14 10-12

Den

sity

(g/c

c)

Theta (t,T,(t))

Micro-Crystalline ZnO

Q = 296 kJ/mole

A Master Sintering Curve Was Constructed For Nano-Crystalline ZnO

1E-16

3.5

4.0

4.5

5.0

5.5

500 600 700 800 900 1000 1100Temperature (°C)

Den

sity

(g/c

c)

30C/min20C/min10C/min

3.7

4.1

4.5

4.9

5.3

1E-15 1E-14 1E-13 1E-12Theta (t,T(t))

Den

sity

(g/c

c)

Q = 268 kJ/mole

Nano-Crystalline ZnO

Master Sintering CurvePredictions Were Tested & Validated

Nano-Crystalline ZnO Sintering

3.5

3.9

4.3

4.7

5.1

5.5

1E-16 1E-15 1E-14 1E-13 1E-12Theta (t,T(t))

Den

sity

(g/c

c)

30°C/min to 870°C

20°C/min to 780°C

10°C/min to 713°C

5°C/min to 633°C

A Slower Heating Rate MayAlter Sintering And The MSC

• A-16 Al2O3 Sshowsseviation from the MSC at 1°C/min.

• Surface diffusionresults in coarsening at the expense of densification.

55

60

65

70

75

80

85

90

95

10-20 10-19 10-18 10-17 10-16 10-15 10-14

Rela

tive

Den

sity

(%)

(t,T(t))10-13

Alcoa A-16 Alumina

10 - 40 °C/min

θ

1 °C/min

MSC Theory Was AppliedTo Nano-Crystalline ZnO Sintering

Nano-Crystalline ZnO Sintering48 nm average particle size30 m2/g specific surface area

62.6% TD compacts sintered to 99.2% TD

Q = 268 ± 25 kJ/mole

A master sintering curve (MSC) was constructed

3.5

3.9

4.3

4.7

5.1

5.5

1E-16 1E-15 1E-14 1E-13 1E-12Theta (t,T(t))

Den

sity

(g/c

c)

30°C/min to 870°C

10°C/min to 713°C

5°C/min to 633°C