Materials Science and Development in Support of Inertial Fusion Energy

Lance SneadSteven Zinkle

Timothy Burchell

Oak Ridge National Laboratory

Presented at the Laser IFE Program WorkshopNaval Research Laboratory, February 6,7 2001

Research Areas Briefly Covered :

• Thermal Conductivity Modeling (SiC, graphite and composites) • Characterizing and Reducing Radiation Induced Dimensional Changes in CFC’s (IFE Funded, 50k$/yr, 3 year)• Advanced Composites and Low Tritium Retaining Materials (For IFE Proposal)

NRL IFE 2/2001

0

100

200

300

400

500

0 200 400 600 800 1000 1200 1400 1600

Temperature (°C)

MKC-1PH

FMI-222

RGTi

H451

Copper

Present-Day High Thermal Conductivity Materials

NRL IFE 2/2001

Thermal Conductivity Modeling (SiC, graphite and composites)

• Irradiation-induced thermal conductivity degradation in ceramics and graphite is dominated by defect-phonon scattering. Understanding this interaction allows accurate modeling and prediction.

1Kirr(T)

=1

Kumklapp(T)+

1KG.B.(T)

+1

Krd(T)

1Krd(T)

=1

Kirr(T)−

1Kunirr(T)

• The defect resistance term, 1/Krd, is a simple, intrinsic material property .

NRL IFE 2/2001

0.01

0.1

1

10

0.01 0.1 1

Neutron Damage (dpa)

Pyrolitic Graphite(K

RT = 1100 W/m-K)

Compilation 1/Krd

H451 Graphite(KRT = 124 W/m-K)

RGTi (KRT

= 450)

MKC1PH (KRT

=519)

Irradiation Temperature 500°C

Thermal Conductivity Modeling (SiC, graphite and composites) - data on defect resistance -

NRL IFE 2/2001

HFIR IrradiationSnead/Burchell

0

1

2

3

4

300 400 500 600 700 800 900 1000 1100 1200

0.0 DPA0.001 DPA0.005 DPA0.01 DPA0.05 DPA0.1 DPA0.5 DPA1 DPA

Th

erm

al

Co

nd

uc

tiv

ity

(W

/cm

-K)

Irradiation Temperature (°C)

unirradiated

irradiated

DPA=displacement per atom

Predicting Thermal Conductivity Degradation of Advanced CFC’s

NRL IFE 2/2001

- combining theroetical model and measured data -

MKC-1PH High Conductivity CFC

Mitsubishi KaseiMKC-1PH CFC

X Y ZYoung'sModulus(GPa)

Unirr.

Irr.

74.0

98.0

-

-

87.6

87.2BendingStrength(MPa)

Unirr.

Irr.

103.9 +/- 6.8

98.4 +/- 2.7

5.8 +/- 2.5 99.2 +/- 17.6

88.9 +/- 8.2CompressiveStrength(MPa)

Unirr.

Irr.

59.8 +/- 6.8

55.9 +/- 3.1

76.7 +/- 14.0

-

59.6 +/- 6.7

51.0 +/- 7.3LengthChange (%)

Irr -0.39 -0.97

Irradiation Induced Dimensional Change in Advanced CFC’s

1000°C, 10 dpa

• Interstitials created during irradiation form new graphitic basal planes leading to highly anisotropic dimensional changes.• Engineering composites can “balance” and minimize such dimensional changes

• There are no very high temperature data on advanced CFC’s.

NRL IFE 2/2001

Oku Data

METS (Mapping Elevated Temperature Swelling) Experiment

Materials : Kth(@RT) Kth(1000°C) (W/m-K) (W/m-K)

A) Mitsubishi Kasei MKC 1PH (unidirectional CFC) >700 ~250B) Fiber Material Inc. FMI-222 (balanced CFC) >450 ~220

Irradiation in HFIR Core Region Temperature Dose (°C) (dpa)

METS-1 Capsule 9 zones in range of 600-1500°C 2METS-2 Capsule “ 600-1500°C 4METS-3 Capsule “ 600-1500°C 10

Status:• All pre-irradiation measurements completed• Capsules fabricated• Irradiation planned to begin this FY. Duration 1, 2 and ~7 months.• Post-irradiation examination to include thermal conductivity and swelling.

NRL IFE 2/2001

SiC/Graphite System: Engineering Low T-3 retention, High Conductivity Material

Why SiC/Graphite fiber

Combines Advantages of SiC composite : Low tritium retention With Advantages of Graphite fibers : Very high thermal conductivity

Where we are

First attempt at manufacture completed--> thermal conductivity promising--> mechanical properties similar to SiC/SiC composites--> tritium retention measurements underway (Causey)

Drawbacks

--> New material system -->Unknown mechanical performance

-->Unknown radiation performance

NRL IFE 2/2001

1

10

100

1000

200 400 600 800 1000 1200 1400

T-3

Ret

enti

on (

app

m)

Irradiation / T-3 Loading Temperature (C)

Non-irradiated, infinite charge time

Non-Irradiated1 hr Charge Time

High Quality Irradiated CFC (Causey, Snead)

Intermediate Quality Irradiated Graphite (Causey, Snead)

Tritium Retention in Graphite

NRL IFE 2/2001

• T-3 attaches to basal plane edges and highly defected structure. More perfect material and/or high temperature allows less retention.

First High Thermal Conductivity SiC/G Composite

• Matrix : CVI SiC • Fibers : Z-direction either Amoco P55 or Thornel K-1100 fiber X-Y direction P-55 fiber. Volume Fraction 44%.• Architecture : Unbalanced 1-1-6 weave 6 tows in Z-direction

Fiber K-1100 P-55 Nicalon Type-S

Kth (W/m-K@RT) ~950 120 15Diameter (micron) 10 10 13Tensile Strength (GPa) 3.1 1.9 2.6Tensile Modulus (GPa) 965 379 420Density (g/cc) 2.2 2.0 3.2

P55 fiber

K-1100 fiber

NRL IFE 2/2001

High Thermal Conductivity SiC/G Composites

0

50

100

150

200

250

300

350

0 1 2 3 4 5 6Deflection (mm)

3 x 4 x 50 mm

19 mm

38 mm

CVI SiC/K-1100,P-55 fiber unbalanced weave compositeMajor fiaber axis || to tensile axis

• Mechanical performance comparable to that of SiC/SiC composites.

• Further development will likely yield improved properties.

• Total of 9 tests on CVI SiC/K1100 fiber

Ultimate Bend Strength 283 ± 30 MPa

Macroscopic Matrix Microcracking ~130 MPa

NRL IFE 2/2001

High Thermal Conductivity SiC/G Composite- infiltration -

• Good inter-bundle infiltration (5-8% void) • Large intra-bundle porosity (13% void)

P

55

P55 tow

P55 tow

NRL IFE 2/2001

High Thermal Conductivity SiC/G Composites- tritium retention -

10

100

1000

104

0 20 40 60 80 100

UnirradiatedNeutron Irradiated

Hydrogen Solubility (appm)

Graphitic Perfection (%)

1

10

100

1000

104

0.001 0.01 0.1 1 10

N3M graphiteFMI-222 CFCMKC-1PH CFC

Tritium Retention (appm)

Radiation Damage (dpa)

• Tritium retention, non-irradiated and irradiated, is highly dependent on graphite perfection. K-1100 type fibers are nearly perfect.

Atsumi dataTirr=600°C

Tload=1000°C

Tirr=200°C

Tload=1000°C

NRL IFE 2/2001

Causey/Sneaddata

High Thermal Conductivity SiC/G Composites - thermal conductivity -

0

50

100

150

200

250

300

350

400

0 200 400 600 800

Th

erm

al C

on

du

ctiv

ity

(W/m

-K)

Temperature (C)

SiC/SiC Composite (transverse)

P55 Graphite/CVI SiC (high TC)

Morton CVD SiC

K1100 Graphite/CVI SiC (high TC)

• At IFE-relevant temp., SiC matrix / graphite fiber :

--> conductivity exceeds present SiC/SiC

--> conductivity exceeds SiC theoretical maximum

--> exceeds SOMBRERO assumptions

NRL IFE 2/2001

0

50

100

150

200

250

300

350

400

0 200 400 600 800 1000

Th

erm

al C

on

du

ctiv

ity

(W/m

-K)

Temperature (C)

CVD SiC/K1100 Non-Irradiated

CVD SiC/K1100 Irradiated

CVD SiCNon-Irradiated

CVD SiC Irradiated

High Thermal Conductivity SiC/G Composites - thermal conductivity -

• At IFE-relevant temp., SiC matrix / graphite fiber :

--> irradiated TC exceeds maximum for SiC

--> exceeds SOMBRERO assumptions

• irradiated values are empirically determined

NRL IFE 2/2001

Future Efforts in Area of IFE Materials

• Continue and complete METS experiment to define high temperature swelling and thermal conductivity of advanced CFC’s.

• Expand work to include tritium retention and second generation materials. Develop data-base for designers.

• Complete thermal defect model for conductivity prediction.

• Continue low-level development of SiC/graphite system. Include piggy-back irradiation experiment and tritium retention measurement.

• Offer collaborative irradiation-effects study in HFIR low-dose, low-cost rabbit facility.

• Leverage current MFE modeling effort and ceramic/diagnostic programs.

NRL IFE 2/2001