High Thermal Conductivity,Mesophase Pitch-Derived

Carbon Foamsby Dr. James Klett

Metals and Ceramics DivisionP.O. Box 2008, Oak Ridge National Laboratory

Oak Ridge, Tennessee, 37831-6087(423) 574-5220

klettjw@ornl.govwww.ms.ornl.gov/cimtech/cimtech.html

Keywords: Graphite Foam, Thermal Conductivity,Thermal Management

ORNL Mesophase-Derived Graphitic Foam

• Graphitic ligaments– Graphitic-like properties (high

, E,

• Dimensionally stable, lowCTE

• No outgassing• Open Porosity• Excellent thermal

management material

Highly Graphitic Structure

Disrupted Junctions

Highly Aligned Ligaments

200 µm

Contact: James Klett865-574-5220klettjw@ornl.gov www.ms.ornl.gov/sections/mpst/Cimtech/default.htm

200 µm

Foreign PrecursorAR mesophase

FOAM B

Domestic PrecursorConoco Mesophase

FOAM A

200 µm

GPa130691.0--Tensile Modulus

microns0032560Average Pore Diameter

45

384

400

1.17

69

16.5

0

0

8.9

Copper

63

890

180

0.81

69

330

337

600

24

0

0

2.88

Aluminum6061

313

691

175

4.53

0.14

3.45

1.0

500

4

0.98

0.75

0.56

ORNLFoam B

Bulk Specific ThermalConductivity

Specific Heat Capacity

Bulk Thermal Conductivity

Bulk Thermal Diffusivity

Compressive Modulus

Compressive Strength

Tensile Strength

Max Operating Temperature inAir

Coefficient of ThermalExpansion

Fraction Open Porosity

Porosity

Density

(W/m·K)/(g/cm3)218

J/Kg·K691

W/m·K127

cm2/s3.11

Thermal Properties

GPa0.18

MPa5.0

MPa--

Mechanical Properties

°C500

ppm/°C--

0.98

0.73

g/cm30.58

ORNLFoam APhysical Properties

High Thermal Conductivity Graphite Foams

Specific Properties vs. Other Materials

346

67

100

45

64

319

444

886

600

1000

346

67

100

45

11

13

4

9

600

1000

133

0 100 200 300 400 500 600 700 800 900 1000

Aluminum 6061

Silver

Copper

Typical 2-D CFRP

Typical 2-D C/C

Amoco SRG

High Performance Carbon Fibers

Vapor Grown Carbon Fibers

CVD Diamond

Single Crystal diamond

Mat

eria

l

Specific Thermal Conductivity [(W/m·K)/(g/cm3)]

[out-of-plane z]

[in-plane x-y]

Heat Transfer of Metallic Heat Sinks

1.3<0.05250Aluminum Foam

ThermalResistance

°C/W

P/L

(psi/in)

Heat TransferCoefficienth, (W/m2·K)

0.7

1-5

<0.05550Aluminum Pin-Finned

<0.0570-350Aluminum Finned Air Flow

Air Flow

Air Cooling

Air Flow

Heat Transfer for Foam Heat Sink with Air Cooling

4500

3100

4600

2000

2500

1500

2100

1000

9000

2600

0.090.5Water

0.090.5Water

0.150.5Water

0.190.5Water

0.041Water

0.13*0.35AirBlind-holes(parallel to air flow)

0.19*1AirBlind-holes(pin fin negative)

0.26*0.05AirPin-Fin

0.38*<0.05AirFinned

0.13*2AirSolid Foam

ThermalResistance

°C/W

P/L

(psi/in)

Heat TransferCoefficienth, (W/m2·K)

Air Flow

Air Flow

Air Flow

Air Flow

Air Flow

Actual devices• Finned foam heat sink running in Pentium 133 computer since

December 12, 1998.

Heat Transfer as a Radiator Design

<0.0530Current Radiator

0.051,000*Finned

0.11,000*Through-holes

210,000*Solid Foam

P/L

(psi/in)

Heat TransferCoefficient

h, (W/m2·K)

Prototype Radiator DemonstratedProcess Water In

Process Water out

Graphite Foam with extended surface area

Overall 22.9 cm x 17.8 cm x 15.27 cm thick

Air flow over fins

and through holes

Through HolesTotal surface area = 7561 cm2

Measured Uo = 1000 W/m2 ·K depending on air humidity

Similar design tested for 800 hp racing engine

Cross Flow Heat Exchangers

Foam rigidized with Carbon CVI for dramatic improvement in durabilitySurface skin produced during manufacture would become impermeable to H2 (alreadydemonstrated in Fuel Cell Bi-polar plate testing)Can be bonded together or “Glued” together during the CVI Process

porous structure allowed deposition to bond structure together

Cross FlowEasiest to Manifold

Counter-Current FlowMost Efficient

Heat Resistant Composites

Standard Polymer Foam/Polymer

Satellite Applications?Thermal Doubler Panel • Current concept spreads heat across

larger area & reduces temperature• Heat is rejected to space with T4

relationship• A very low through thickness thermal

conductivity of current carbon-carbon (20W/m·K) and honeycomb core limits heatrejection

• The higher through-thickness thermalconductivity of the foam (180 W/m·K) willincrease temperature on outside surface

• High temperature on outside surface willincrease radiation

• Smaller panel footprint, or moreelectronics can be utilized.

C/C panel

Structural Panel

High PowerElectronics

Licensee - Poco Graphite, Inc.

• Leading manufacturer of premium, specialtygraphites and silicon carbides

• Over 35 years experience in the following majormarkets

• General Industrial• Aerospace• Biomedical• Semiconductor

• Texas based manufacturing with offices in Illinoisand France

• Applications Engineers based throughout US• Applications Engineers in France, Germany, Italy

and Singapore

POCO Capabilities

• Materials manufacturing facilities• Design Engineering• Machining expertise to produce finished parts

• In process and finished parts inspection and certification

• Post processing facilities for infiltrations,impregnations, purifcation of materials

• Laminations and bonding

• R & D Laboratories for materials testing anddevelopment

PocoFoam Time Line

• June 1999 - Poco Graphite, Inc. acquired theexclusive license to manufacture ORNLdeveloped foam

• Agreement includes field of use license for finished productsincludingw Heat exchangers

w Cooling systems or heat sinks for aerospace, chemical-process, glass, ceramicand medical industries

• April 2000 - Pilot production at POCO began• May 2000 - First sale of PocoFoam material• October 2000 - Full production of PocoFoam

expected to begin• Future Developments

PocoFoam Availability

• Material is available for purchase• Sizes up to 10 x 10 x 1 1/2” are in stock

• Pricing curve is consistent with developmental materials• Alliances are being made with developmental partners