Evaluation of thermal conductivity of single walled carbon nanotube composite film (SWNT-PVA samples with different length, density and alignment)

T. Sato1, Y. Taguchi2 and Y. Nagasaka2

1School of Integrated Design Engineering, Keio University, Japan
2Department of System Design Engineering, Keio University, Japan

Keywords: thermal conductivity
property: photothermal radiometry
material: carbon nanotubes, polymer nono composite film

Carbon nano tubes (CNTs) are isotope of carbon and CNTs have unique properties. The thermal conductivity of single walled carbon nano tubes(SWNTs) are estimated to be 100~1000 W/m/K, compared to metal materials the thermal conductivity is very high. Since SWNTs have the unique properties, the properties and the full potential of SWNTs-based composites are expected to be superior, but they have not yet been fully investigated. Uniform dispersion and alignment of nanotubes within the polymer matrix are fundamental to produce composites with reproducible and optimal properties. It is expected that the thermal conductivity of polymer is enhanced by the addition of small amount of vertically aligned SWNTs. In order to develop SWNTs nano composite materials, we have to evaluate thermal performance of micro nano-size samples properly. In the present study, we controlled the dispersion and vertical alignment of SWNTs prepared by the alcohol catalytic CVD in the polymer. The SWNT-polymer films are made by infiltrating the polymer into VA-SWNT arrays. We compared different samples having different density and alignment. The sample are SWNT-PVA(polyvinyl alcohol) composite thin films with 5~20 vol.% vertically aligned SWNTs. Thickness of SWNT-PVA layer is 10~50 um, pure-PVA is 10~30 um, and Pt layer evaporated for absorption laser beam is 200 nm. We evaluate alignment of nanotubes by Raman scattering method and measure thickness of SWNT layer by SEM. We have applied photothermal radiometry (PTR) to measure the thermal conductivity of above-mentioned SWNT-PVA samples. PTR is suitable to measure the thermal conductivity of thin film, because it is a contact free and non-destructive method. By improving the extinction ratio of laser diode at high frequency range, we have detected PTR signal up to 10 kHz. We calculated thermal conductivity by carve fitting program and compared SWNT-PVA and pure-PVA.

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