1

FABRICATION OF SiC/SiCf COMPOSITE BY VACUUM INFILTRATION AND

HOT PRESSINGParlindungan Yonathan1, Jong-Hyun Lee1, Dang-Hyok Yoon1,

Weon-Ju Kim2 and Ji-Yeon Park2

1School of Materials Science and Engineering, Yeungnam University2Nuclear Materials Research Division, KAERI, Korea

2

Presentation OutlineBackground

SiC/SiCf applications and advantagesFusion reactors applications and issuesMain Goal

MaterialsProcessCompositionDesignResult

SiC/SiCf ExperimentConclusion

3

Background

4

SiC/SiCf Advantages

High specific strengthGood high-temperature propertiesGood fracture resistanceGood thermal conductivityCorrosion and wear resistanceLow induced radioactivity under nuclear environments

5

SiC/SiCf Applications

6

Fusion Reactors

First WallBe, Be-alloy W, W-alloy

SiC/SiCf,C/C

He bubbles

Fusion reactor blanket concept:

• TAURO, European Union (SiC/SiCf)

• ARIES-AT, US (SiC/SiCf)

• DREAM, Japan (Be-Li2O-SiC)

*Fusion technology institute, University Wisconsin

ARIES-AT vertical cross-section

7Permeability issue in SiC/SiCf

Bombardment of high energetic neutrons in to composite surface

Bubbles formation on the surface or blistering

0.86Å

Point defect behavior in ceramics

He and H atoms will move to a porous site, vacancy cluster, and grain boundary to start causing delamination issue

* J.H Kim, Y.D Kwon, Parlindungan Yonathan, I. Hidayat, “The energetic of He and H atoms in the irradiated β-SiC: abinitio approach”

8

Main GoalTo achieve a high density SiC/SiCf composite by maximizing SiC slurry infiltration into SiC woven fiber and finally to attain high structural strength composite materialProcess development high density composite material:

Milling processInfiltration methodSlurry compositionTape casting

Evaluation of material performanceMaterial characteristics and morphologyMechanical properties

9

Materials

10

SiC powder

Average particle size: 52nm(NanoAmor), 30nm(Marketech)Fine & spherical β-SiCBET: 80 m2/g (NanoAmor), 109 m2/g (Marketech)Surface is covered with SiO2 layer thinner than 2nm

β-SiC, Marketech

1.7nm

β-SiC, NanoAmor

11

SiC Woven fiber

2D woven fiber

PyC coated by KAERI

PyC coated design was based on CVI-SiC/SiCfcomposite process

Top view Cross-section view Pyrolitic carbon-coated fiber

3.1Mass density (g/cm3)

2500Tensile strength (MPa)

1600Number of filaments/yarn

7.5Diameter (mm)

(C/Si) 1.08, Al 0.005 Atomic composition

Tyranno-SA Grade-3 Properties

TyrannoTM-SA Grade-3 FiberUbe Industries, Ltd., Tokyo, Japan

(220nm)

12

Sintering Additives

Magnesium Oxide (MgO)Alumina Oxide (Al2O3) Yttrium (III) Oxide (Y2O3)

Sintering additives facilitate the densification of SiC due to its highly covalent bond structureAl2O3/Y2O3/MgO = (0.64/0.26/0.1) wt%*Liquid phase assisted sintering

* KY Lim, DH Jang, YW Kim, JY Park, DS Park," Effect of the processing parameters on the densification and strength of 2D SiC fiber-SiC matrix composites fabricated by slurry infiltration and stacking process

13

Process

14

Process focus

Milling (dispersion)Solid volume fraction in green bodyRate of infiltration and densificationSinterability (pressure, temperature)

Effective infiltrationControllable infiltration

Infiltration

15Ball milling vs. High Energy Milling

@

The most conventional mechanical milling2–200 mm spherical or cylindrical ballsRotation under 200 rpm

Recently introduced (MiniCer, Netzsch)0.01 – 0.8 mm ZrO2 beadsRotation up to 4200rpmVery effective in milling

High energy millBall mill

16

0 20 40 60 80 100 120

0

3000

6000

9000

12000

15000

0 20 40 60 80 100 120

Milling time (hr)

Visc

osity

(mPa

.s)

High energy milling

Ball milling

Milling time (min)

Why HEM

212.

11.1

rlA

φφσ

−=

Rumpf’s Equation:

n

rr

tt

⎟⎟⎠

⎞⎜⎜⎝

⎛=

2

1

2

1

Herring’s scalling laws:

All proposed mechanisms of sintering and densification of ceramic powder compacts agree that the particle size is one of the most important parameters in the rate of progress of these processes.

At constant temp

* Nono Darsono a, Dang-Hyok Yoon a,*, Jaemyung Kim b, “Milling and dispersion of multi-walled carbon nanotubes in texanol”

17

Vacuum Infiltration

Enhance the infiltration by vacuum absorption forceEnhance the composite density in fiber

18

Vacuum InfiltrationThe slurry is infiltrated as the vacuum pressure progressively released to return to surrounding pressure, thereby causing the slurry to be forced through the fiber pores.Advantages:

Using vacuum force to help infiltration processInfiltration can be controlled by altering the vacuum pressure and release of vacuum time.

Vacuum pressure 0.1PaPumping speed 120L/min

SiC Slurry

SiC Fiber

Vacuum onVacuum release

19Vacuum Infiltrated fiber - SEM

Top viewC

ross-section view

Normal infiltration (dipping) Vacuum infiltration

20

Composition

21

Composition

Two types of slurryInfiltration slurry Tape casting (binder 40% wt% wrt. powder)

Two composition variablesSintering additives (2/6/10 wt% wrt. powder)Binder (PVB B-98, 0/5/10/45% wrt. powder)

22Effect of sintering additives

99.89%3.19810NanoAmor

99.16%3.1746NanoAmor

79.02%2.5292NanoAmor

99.55%3.18710Marketech

99.29%3.1786Marketech

69.21%2.2152Marketech

Density (%)Density (g/cm3)

Sintering additives (% w.r.tpowder)Powder Type

Sintering additives

High Energy Milling

Drying

Solvent (Ethanol)

High Energy Milling

Hot Pressing

Density(Archimedes)

SEM

TEM SEM

Drying

Sintering additives

SiCPowder

Bending test (4-point)

2 4 6 8 100

100

200

300

400

500

0

20

40

60

80

100

Marketech Density

Rel

ativ

e D

ensi

ty (%

)

Additive (wt%)

Flexural Strength (MPa)

Marketech Flexural Strength

Relative density & Flexural strength

Nanostructure Density

Nanostructure Flexural Strength

23

Effect of binder

0%NanoAmor4

5%NanoAmor3

10%NanoAmor2

45%NanoAmor1

Binder percentage (w.r.t. powder)Powder TypeNo.

Vacuum infiltration

High energy milling

Binder solution

Cryo-fracture

SEM

Drying

Density(Archimedes)

SEM

Binder burn-out

Hot Pressing

Bending test(4-point)

-5 0 5 10 15 20 25 30 35 40 45 500

10

20

30

40

50

Sintering additives 6%Shear Rate at 42.24/sec

Infiltration slurry viscosity (β−SiC NanoAmor)

Visc

osity

(cP)

Binder (% wrt powder)

0 5 10 45

24SEM pictures of infiltrated fibers after binder burn-out

Fiber cross-section45% binder

Fiber cross-section10% binder

Fiber cross-section5% binder

Fiber cross-section0% binder

Top-view45% binder

Top-view10% binder

Top-view5% binder

Top-view0% binder

25SEM pictures of hot-pressed infiltrated fiber

Fiber cross-section45% binder

Fiber cross-section10% binder

Fiber cross-section5% binder

Fiber cross-section0% binder

Cross-section view45% binder

Cross-section view10% binder

Cross-section view5% binder

Cross-section view0% binder

26

0% 5% 10% 45%

2.4

2.5

2.6

2.7

2.8 Infiltrated fiber hot-pressed density

Density Percentage

Binder content (%)

Den

sity

(g/

cm3 )

80

90 Measured density/True D

ensity (%)

Density of infiltrated fiber

161.43131121.52117.6Flexural Strength (MPa)87.35%83.56%80.83%80.42%Percentage density2.7082.59052.5057142.493143Density45%10%5%0%Binder Composition

0% 5% 10% 45%50

75

1000% 5% 10% 45%

100

150

200

Flexural Strength (MPa)

Relative density & Flexural strength of SiC/SiCf

Rel

ativ

e D

ensi

ty (%

)

Additive (wt%)

Density

FlexuralStrength

27

Composite design

28

Composite structureComposite formed by stacking the SiC green sheet and the infiltrated SiC fibersBinder burn-out at 4000C for 2-hours at 1oC/minHot pressed at 1750oC, 20MPa, 3-hours

SiC infiltrated fiber (NanoAmor)

SiC infiltrated fiber

(Marketech)

Green tape (NanoAmor)

Green tape (Marketech)

SiC green tape

Infiltrated SiCfiber with SiCslurry

SiC/SiCf composite [0o/45o]62-72% fiber volume fraction

Hot pressing

5cm20 infiltrated fibers and

tapes

29

Effect of green tape

Factors:Slurry compositionDispersionZeta potentialViscosity

vacuum infiltration & stack with SiCTapes

HEM (High energy milling)

Binder solution

Cryo-fracture

SEM

Drying

Density(Archimedes)

SEM

Binder burn-out

Sintering (Hot Pressing)

Bending test(4-point)

Tape casting

DISPERSION STABILITY AND ITS EFFECT ON TAPE CASTING OF SOLVENT-BASED SiC SLURRY Jong-Hyun Lee, Parlindungan Yonathan, Dang-Hyok Yoon, Weon-Ju Kim* and Ji-Yeon Park* (Yeungnam University, Korea, * KAERI, Daejeon, Korea)

30Sintered SiC/SiCf

Nano-tape Nano Marketech60

80

100

100

200

300Relative density & Flexural strength of SiC/SiCf

Flexural Strength (MPa)

Rel

ativ

e D

ensi

ty (%

)

Powder type

Sample 1 (Nano-tape)

Sample 2 (Nano)

Sample 3 (Mark-tape)80-90%90-95%98.78%Percent density (%)2.5-2.82.9-3.03.161Density (g/cm3)

CVI-PiPOther Hot pressing

reported value

Vacuum infiltration & Hot pressing

31Mechanical 4point bending test

Sample 1 (Nano-tape)

Sample 2 (Nano)

Sample 3 (Marketech)

NanoAmor(tape)

NanoAmor(no tape)

Marketech(tape)

32Sintered fracture cross-section

NanoAmor+Tape(Before bending test)

NanoAmor+Tape(After bending test)

NanoAmor(After bending test)

Marketech+Tape(After bending test)

NanoAmor+Tape(Before bending test)

NanoAmor+Tape(Before bending test)

33

XRD result

20 30 40 50 60 70 80

β−SiC phase α−SiC phase

XRD result of SiC/SiCf composite

NanoSample 2

MarketechSample 3

Inte

nsity

(a.u

.)

2θ

NanotapeSample 1

The phase structure were changed for both nano powder, however phase change were not observed for marketechpowder

34

Conclusion• High density of SiC/SiCf was achieved at 3.161g/cm3

(98.78%) by vacuum infiltration and hot pressing process.• Flexural strength of 230MPa was achieved with a brittle

fracture mode showing very little fiber pull out. • Phase changed was observed after hot pressing at 1750oC-

20MPa-3hours, showing both alpha and beta-SiC phase in the composite.

• SiC tape improved the sintered density and strength in the SiC/SiCf composite.

• Slurry formulation including sintering additives plays an important role in vacuum infiltration and hot pressing process.

• More intensive experiment on SiC/SiCf interface to improve the composite strength.

35

This project is financial supports by:The Ministry of Knowledge Economy through a Materials &

Components Technology R&D ProgramHighly appreciated

Acknowledgement