V.A. Kreisberg, V.P. Rakcheev, T.V. Antropova
Microporosity of porous glasses: new investigation techniques
Glass Physics and Chemistry, 2003, v.29 (6), p. 540-546 (2003)

ABSTRACT
Two new methods are developed for investigating the microporosity of porous materials. The first method, namely, diffusion diagnostics, is based on a computer analysis of the kinetics of gas desorption from a porous material into high vacuum. In this method, the kinetics of gas desorption is measured using mass spectrometry. Another method is based on the analysis of the equilibrium isotherms of gas desorption at low pressures. The microporous and mesoporous substructures of the porous glasses prepared by leaching of two-phase alkali borosilicate glasses in a 3 M HCl solution at 100 C are investigated using both the new methods and the classical adsorption methods. A correlation between the porous structure of glasses and their synthesis and phase separation conditions is revealed. It is demonstrated that porous glasses have a through mesoporous substructure with mean pore diameters ranging from 4 to 15 nm and a polymodal microporous substructure with pore sizes and also medium- and large-sized micropores. It is found that porous glasses contain bottle-shaped pores with sizes corresponding to the micropore range. An increase in the temperature of heat treatment of glasses from 550 to 700 C and an increase in the boron oxide content in the silica phase lead to an increase in the volume of micropores in porous glasses.