Structural mechanism of water adsorption in hydrophobic micropores from insitu small angle X-ray scattering

The in situ small-angle X-ray scattering (SAXS) of water adsorbed on pitch- based activated carbon fibers (ACF) of pore width nl = 0.8 and 1.1 nm were measured at 303 K and different relative pressures. The SAXS spectrum of AC F of w = 1.1 nm in the direction of desorption did not overlap that in the adsorption direction, showing hysteresis. The density fluctuation data from Ornstein-Zernike (OZ) analysis for the SAXS profiles indicated that water molecules form great clusters in the course of adsorption, but desorption p roceeds through uniform molecular evaporation. (C) 2000 Elsevier Science B. V. All rights reserved.