Thermal and electrical conduction properties of vertically aligned carbon nanotubes produced by water-assisted chemical vapor deposition

We present both thermal and electrical conduction properties of vertically aligned carbon nanotubes (VACNTs), synthesized by the water-assisted chemical vapor deposition method using Fe–Ti–O nanoparticles as catalyst. Thermal diffusivity and electrical resistance of VACNTs have been measured by the laser flash method and direct-current four-terminal method, respectively. The VACNTs are found to have thermal diffusivities of the same order as isotropic graphite and the electrical characteristics of semiconductors. The electrical resistance shows a T−1/4 temperature dependence, which implies that the conduction of electrons is dominated by 3D Mott variable range hopping.

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► VACNTs are synthesized by catalytic-CVD method using both Fe–Ti–O catalysts and a small amount of H2O vapor.
► The thermal diffusivity of VACNTs is of the order of that of isotropic graphite.
► The temperature dependences of electrical resistance are characteristics of semiconductors.
► The anisotropy (R⊥/R∥) gradually increases with decreasing temperature.