Structure and gas permeability of multi-wall carbon nanotube buckypapers

We report on the filtration behavior, scanning electron microscopy (SEM) and gas permeability of multi-wall carbon mats (buckypapers). The SEM-apparent macropore diameter, image fractal dimension and lacunarity (a measure of translational invariance) of the samples averaged at 38 nm, 1.82 and 0.55, respectively. Their N-2 adsorption analysis revealed an average BET specific surface area of 197 m(2)/g, BJH pore diameter of 2.67 nm and FHH fractal dimension of 2.492. These parameters were rather insensitive to the preparation conditions. The effective diffusivity of six common laboratory gases (O-2, N-2, H-2, He, CO2, CH4) through buckypapers of different thicknesses was also measured. Results fell into the 3-12 x 10(-9) m(2) s(-1) range and correlated with the kinetic diameter of the gases. (C) 2007 Elsevier Ltd. All rights reserved.