ИСТИНА

The availability of macro-, meso- and micropores on solid surface defines its real morphology. The micropores are of particular importance because there are no methods for determining the size and volume of micropores, especially in the cases when pore volume is small. A new method of diagnostics of micro porosity of solid is developed. It is based on the kinetic desorption method with the mass spectral analysis of flows of adsorbate desorbing into the high vacuum. After preliminary adsorption of oxygen or nitrogen at temperature of liquid nitrogen, the pumping out and mass spectral recording of gas flow desorbed at the same low temperature from microporous sample are carried out. Distinguishing in the diffusion drag of the gas transport in the pores of various morphology (diameter, volume, shape, the energy of surface-gas interaction) results in the essential difference of the type of isothermal kinetic curves of desorption of which the corresponding diffusion coefficients can be calculated. Owing to the high sensitivity of mass spectral analysis one can determine the micropores of extremely small capacity (10-10 cm3/g). Presence of macropores does not hinder the diagnostics of micropores. Microporous surface morphology of silica glass and other materials obtained by mechanical crushing was studied by proposed method before and after high temperature treatment. The healing of micropores on silica glass and quartz surface at high temperatures (pore surface decreases) and the change in size distribution were detected. The results of the micropore diagnostics of glassy and crystalline samples SiO2 and Al2O3 with low specific surface and with different conditions of surface formation and thermal treatment were correlated with the results of microporous diagnostics by the same method for highly dispersed materials with known structure of micropores (silica, zeolites).