Effect of heat treatment on the composition of surface layers in lithium silicate glass exposed to acid and salt solutions

摘要

The concentration distribution of lithium ions in the surface layers of the 27Li_2O-73SiO_2 (mol %) glass samples subjected and unsubjected to heat treatment under different conditions after exposure to 0.1 M HCl + y M LiCl (y = 0,1.0,5.0. and 10) solutions is studied by the HF-sectioning technique. It is found that the specific ("molded") layer former on the glass surface upon pouring of a glass melt into a cooled mold affects the leaching processes in both the initial and phase-separated glasses. In the absence of the molded layer, the leaching rate of the initial glass in the acid is lower than that of the phase-separated glass and higher than that of the crystallized glass. The leaching rate of the phase-separated and crystallized samples in the acid with an salt additive is higher than that of the initial salt. Chlorine ions in the acid solution bring about a weakening of the silicon-oxygen netowrk. The profiles of the dissolution rate of glass in a 1% HF solution correlate with the concentration profiles of lithium.