Proc. Int. Symposium on Glass Problems (Istanbul, Turkey, Sept. 4-6, 1996), v. 1, p. 185-191 (1996)
ABSTRACT. The diffusive transport of water in silica glass affect many important properties and working parameters of this material and its products. The known models of water diffusion based only on kinetic scheme of water interaction with silica matrix forming hydroxyl groups cannot explain the concentration dependence of water diffusion coefficient and some other features of diffusion behaviour of water in glass. The structural-geometric factor should be taken into account as well. During the process of diffusion into glass structure and fast hydroxylation, the breaking of silicon-oxygen bonds occurs, the rings formed by silicon-oxygen tetrahedra disclose, the mean effective diameter of the rings increases, and the water diffusion coefficient rises. The structural-geometric model interprets why crystalline quartz with more dense structure but with straight diffusion channels possesses higher water diffusion coefficients at high temperatures than silica glass.
Laboratory of Catalysis and Gas Electrochemistry