Yushi Harada

Scattering of Monatomic Gas Molecules on Vertically Aligned Single‐Walled Carbon Nanotubes

The scattering process of He molecules on vertically aligned single‐walled carbon nanotubes (VA‐SWNTs) was investigated using the molecular beam technique. The accommodation coefficients for VA‐SWNT films on quartz substrates at room temperature are remarkably high compared to those for bare surfaces, demonstrating the effectiveness of the surface modification technique with VA‐SWNT films for enhancing the energy transfer between gas molecules and surfaces. The enhanced energy transfer suggests that gas molecules can easily penetrate deep into the films because of their high porosity and suffer multiple collisions with bundles of SWNTs. The less effective energy accommodation at elevated temperatures, however, implies that the average number of collisions which gas molecules undergo before leaving the films is not large enough to maintain the perfect accommodation even at high temperature.

Energy accommodation of gas molecules with free‐standing films of vertically aligned single‐walled carbon nanotubes

The scattering process of gas molecules on vertically aligned single‐walled carbon nanotubes (VA‐SWNTs) was investigated by the molecular beam technique. To investigate interactions between VA‐SWNT films themselves and helium gas molecules without the presence of substrates, free‐standing films were used. The scattered molecules are divided into three components; reflected molecules, diffusively transmitted molecules, and directly transmitted molecules without interaction with SWNTs. Even with the thin film, most molecules have interacted with the films, which suggests that most molecules have interacted at the randomly oriented layer at the topmost of the films. Because of low accommodation coefficients of helium gas, VA‐SWNTs films are thought to be useful as a surface modification to enhance energy accommodation.