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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Thermal Conductivity Measurement of Bare Carbon Nanotube Films Using the Photoacoustic Technique

DOI: 10.1615/IHTC15.nmm.009607
pages 5449-5460

Thomas L. Bougher
Department of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA

Cristal J. Vasquez
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology

Baratunde A. Cola
Georgia Institute of Technology, G.W. Woodruff School of Mechanical Engineering, 801 Ferst Drive, Atlanta, GA 30332-0405; Georgia Institute of Technology, School of Materials Science and Engineering, 771 Ferst Drive, Atlanta, GA 30332-0245; Carbice Nanotechnologies, Inc., 397 8th Street NE, Atlanta, GA 30309


KEY WORDS: Nano/Micro scale measurement and simulation, Conduction, photothermal, carbon nanotubes, thermal conductivity

Abstract

The photoacoustic technique was used to measure the thermal conductivity of nanostructured materials without the use of a metal foil or film to absorb laser energy. Using the sample material as the absorption layer eliminates the need to bond the material to a metal foil or deposit a metal film on the sample, which creates an unknown contact resistance between the sample layer and the metal. The measurement technique is demonstrated on vertically aligned carbon nanotube (CNT) arrays, and CNT sheets. Bare samples were measured and compared directly to metal-coated samples. The thermal conductivities of multiwall carbon nanotube (MWCNT) arrays were between 0.4 and 3.1 W/m-K, while the thermal conductivities of the MWCNT sheets were found to be approximately 0.14 W/m-K. The difference between the bare and metal-coated values was less than 25% for five out of the six samples. We believed that in several cases changes in laser absorption within the CNT array caused discrepancies between the two measurements. A decrease in thermal conductivity of MWCNT arrays with height was observed as the array height increased from 15 to 53 ?m.

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