Small-angle x-ray diffraction of Kr in mesoporous silica : Effects of microporosity and surface roughness

• Published in: Physical review. B, Condensed matter and materials physics Vol. 72; no. 6; pp. 064122.1 - 064122.7
• Main Authors: HOFMANN, T, WALLACHER, D, HUBER, P, BIRRINGER, R, KNORR, K, SCHREIBER, A, FINDENEGG, G. H
• Format: Journal Article
• Language: English
• Published: Ridge, NY American Physical Society 01-08-2005
• Subjects: ADSORPTION; ADSORPTION ISOTHERMS; BRAGG CURVE; CAPILLARIES; Chemistry; Colloidal state and disperse state; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ELECTRON DENSITY; Exact sciences and technology; FILM CONDENSATION; FRACTALS; General and physical chemistry; INTERFACES; KRYPTON; LAYERS; MATERIALS SCIENCE; POROSITY; POROUS MATERIALS; ROUGHNESS; SILICA; Solid-liquid interface; SUBSTRATES; Surface physical chemistry; SURFACES; VAPORS; X-RAY DIFFRACTION; Liquid-vapor transformations; Pore size; Adsorption; Fractal dimension; Capillarity; Bragg diffraction; Roughness; Condensation; X ray diffraction; Porous material; Silica; Mesoporosity
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/physrevb.72.064122

Kr has been adsorbed in SBA-15, a template-grown mesoporous silica substrate. A volumetric adsorption isotherm is presented. The Bragg peaks of the pore array have been measured by small angle x-ray diffraction and analyzed as function of the filling fraction in terms of the electron density contrast, the radial position of the liquid-vapor interface, and film roughness, both for the regime of film growth and capillary condensation. The results are compared with the theory of Saam and Cole. It is shown that the microporosity of the matrix leads to a delay of capillary condensation. The peculiar dependence of the film thickness on the filling fraction points to a high fractal dimension of the pore walls.