Influence of the Composition and Temperature of Heat Treatment of Porous Glasses on Their Structure and Light Transmission in the Visible Spectral Range

摘要

The pore structure and light transmission of high-silica porous glasses in the visible spectral range have been investigated as a function of the heat treatment temperature and the composition of the initial two-phase alkali borosilicate glass. The character of light transmission in porous glasses has been analyzed in the framework of the concepts of structural features of their pore space and the processes occurring in the porous glass during heating. It has been demonstrated that an increase in the temperature of heat treatment of porous glasses with different compositions leads to an increase in the pore size and a decrease in their specific surface area (with a nearly constant total porosity), which is associated with the processes of overcondensation of pores due to the rearrangement and the change in the packing density of secondary silica particles. It has been revealed that the introduction of phosphate and fluoride ions into the initial sodium borosilicate glass results in an increase in the light extinction coefficient of porous glasses due to the increase in the sizes of phase-separated inhomogeneity regions in the initial two-phase glasses, the formation of larger pores, and the presence of nano-sized microcrystalline phases in porous glasses.