Gas transport in vertically-aligned carbon nanotube/parylene composite membranes

Vertically-aligned carbon nanotube (VACNT) composite membranes were fabricated by impregnating carbon nanotube (CNT) forests with poly-para-xylylene (parylene-C) through room-temperature chemical vapor deposition (CVD). Transport properties of diverse gases through the CNT/parylene membranes were investigated. The gas permeances scaled inversely with their molecular weights in accordance with Knudsen model and the value of permeance was about 30 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to the atomically smooth interiors of CNTs. In addition, the gas permeance values in this work were higher than those reported for other VACNT membranes, due to the smaller membrane thickness and good crystallinity of the CNTs.