Gas solubility is glasses - principles and structural implications

Gas solubility in a variety of glasses is an integral part of the overall m echanism of gas transport in these materials. There are numerous practical aspects of this problem with substantial commercial implications, e.g,, gas separation and the outgassing and leak testing of vacuum systems. The stat istical thermodynamics of gas solubility can be analyzed in regard to the i nterstitial structure of the glass. The gas atoms or molecules serve as str uctural probes. In turn, the structural analysis gives a basic understandin g of the mechanisms of gas solution, diffusion, and permeation. For example , noble gas solubility in vitreous silica indicates the distribution of int erstitial size is log-normal. This result has been confirmed by analysis of computer-generated models and, in turn, has consequences for the transport of molecular species such as oxygen and water during the thermal oxidation of silicon, Although this paper considers gas solubility in rigid glasses below the glass transition temperature, there are implications for the rela ted problem of gas solubility in glass liquids, another problem of substant ial commercial interest. Recently, the understanding of gas solubility has had an effect on models of geological importance, such as volcanic eruption s and formation of the Earth's atmosphere. (C) 1999 Published by Elsevier S cience B.V. All rights reserved.