Gas transport characteristics through a carbon nanotubule

We report the first determination of the slip coefficient for tubular carbon structures that have been produced by chemical vapor deposition on a porous alumina substrate with nominal pore diameters of 200 nm. A uniform 20-30 nm thick carbonaceous coating was formed over the pores. The permeability of the porous alumina was then measured using a pressure/flow apparatus. A finite element code with adjustable slip boundary conditions was used to model transport through the alumina. In the absence of a carbonaceous material, transport was well described by diffuse reflection at the wall. When a carbon nanotubule was present, however, a tangential-momentum accommodation coefficient, or,, of 0.52 +/- 0.1 was predicted for argon, nitrogen, and oxygen.