単層カーボンナノチューブの熱物性 Thermal Properties of Single - Walled Carbon Nanotubes ○

Single-walled carbon nanotubes (SWNTs) are expected to be the most exciting material in the nanotechnology. In addition to the outstanding electronic, optical and mechanical properties, thermal properties of SWNTs are quite unique with the high thermal conductivity along the tube axis. The molecular dynamics studies of thermal conductivity of a nanotube and thermal conductance between a nanotube and various materials are reviewed. The experimental approach for physical properties can be possible with the high-purity and aligned SWNT sample. The ACCVD technique using alcohol as the carbon source is reviewed. Several heat transfer problems related to single-walled carbon nanotubes (SWNTs) are considered using molecular dynamics (MD) simulations. The Brenner potential with the simplified form is employed as the potential function between carbon and carbon within a nanotube. MD simulations of thermal conductivity along a nanotube, isotope effect in longitudinal thermal conductivity, and thermal boundary resistance in a junction of nanotubes are reviewed. Then, the heat transfer from an SWNT to various surrounding materials is simulated by MD simulations. Heat transfers between nanotubes in a bundle of nanotubes and between a nanotube and Lennard-Jones fluid are considered. The heat transfer rate can be well expressed by employing the thermal conductance. The value of thermal boundary resistance is compared for nanotube-junction, bundle, and water-nanotubes cases. Recent developments of catalytic CVD generation of single-walled carbon nanotubes (SWNTs) by using alcohol as the carbon source will be discussed. High-purity SWNTs can be generated at relatively low CVD temperatures from metal catalytic particles supported on zeolite or directly dispersed on flat substrates such as meso-porous silica, quartz and silicon. The zeolite support is used for bulk generation and direct growth on substrates is useful for optical or semi-conductor applications. By use of the ethanol, the CVD apparatus can be very simple; the cold-wall CVD with in-situ Raman observation is demonstrated. Recently, the vertically aligned SWNTs mat with about 5 μm is grown on quartz substrates by employing the most efficient activation of catalytic metals.