The boundary between carbon nanotubes is an important factor affecting the transport properties of carbon-nanotube-based materials. Recently, carbon nanotube bundles have been shown to have very high thermal anisotropy due to boundaries at $1000{}^{\circ }\mathrm{C}$. However, it is unclear whether the anisotropy is peculiar to this high-temperature region. Here, we conduct an in situ study of the anisotropic thermal properties of bundles of carbon nanotubes by utilizing the phase transition of Sn nanoparticles. The results indicate that the anisotropic thermal properties are not unique to $1000{}^{\circ }\mathrm{C}$. Moreover, observation of two different phase transitions of Sn particles enables the direct comparison of two temperature regions and indicates that carbon nanotube bundles have higher anisotropy at lower temperatures. A simple finite element calculation suggests that the size-dependent thermal conductivity of carbon nanotube bundles can be attributed to the extremely large anisotropy estimated in this study.

Close

PrevNext

View figure in article

• Heat transfer
• Electron microscopy