INTRODUCTIONMembrane technologies of gas mixture separation are a steadily developing research area [1] and require the creation of selective membranes possessing high permeability, increased mechanical strength, and thermal and chemical resistance. The membranes are manufactured from polymeric and nonorganic mate rials in the form of planar, tubular, and spiral elements [2]. Any damage to such constructions in the process of their use leads to a drastic quality drop of the gas mixture separation.Increasing the effectiveness of gas mixture separa tion is achieved by the use of hollow closed membrane elements. In this area, expensive synthetic glass microspheres based on borosilicate glass are used [3,4], which are subjected to additional processing to improve their permeability (acid etching, doping with rare earth and transition metals).The promising prospects of using silicate glasses as membranes are due to the combination of their high permeability to helium and hydrogen with an extremely low permeability to the heavier gases (oxy gen, nitrogen, methane); moreover, the selectivity of separation of helium-nitrogen and helium-methane gas mixtures reaches the values of 10 5 -10 6 . This is one of the significant technological advantages of silicate glass membranes over polymeric ones [5].An essential influence on the diffusive properties is exerted by phase transformations in the glasses, accompanied by crystallization of phases. For the glass crystalline materials, helium diffusion occurs along two routes: through the anionic lattice of the glass and along the interphase "glass-crystal" bound aries. The contribution of each route to the total diffu sion process depends on temperature. For example, for the quartz glass samples containing cristobalite crystals, at temperatures above 300°C, the preferable route is lattice diffusion of helium with an activation energy of 24 kJ/mol; in the low temperature interval 0-110°C, diffusion along the interphase "glass-cris tobalite" boundaries becomes predominant, for which the activation energy amounts to 18 kJ/mol [6].In the creation of selectively permeable mem branes for gas mixture separation, as well as in the sorption and storage of the desired components (e.g., helium and hydrogen), of special interest are hollow microspheres with a thin glass crystalline shell, which provide increased permeability and mechanic strength. Such microspherical membranes can be made of glass crystalline cenospheres of fly ash, whose special features of morphology and phase composition suggest promising prospects for obtaining certain modern functional materials.Cenospheres, or aluminosilicate hollow micro spheres, are one of the microspherical components of fly ashes of the sialic type [7]; they are characterized by a low (0.2-0.8 g/cm 3 ) bulk density and can be easily isolated in concentrated form by gravitational meth Abstract-We studied the interrelation between the composition, morphology, and helium permeability of the shell of narrow fractions of nonmagnetic nonperforated cenosph...
