Some comments on “Reduction”

Residual gas in closed systems—I: development of gas in fused silica ampoules

“…A significant contribution of hydrogen and water to the gas accumulating in the ampoules is apparently due to the chemical solubility of the species in silica [11,13], the interpretation supported also by the theoretical calculations discussed above. Since most of the species are bound chemically, the concentration of diffusing species is very low and their desorption is much smaller than might be expected based on the total solubility alone.…”

“…The calculations were performed assuming the model of chemically dissolved hydrogen discussed in Refs. [13,24]:…”

“…The outgassing conditions applied are usually based more on a non-quantified rule of thumb approach than on a more solid understanding of the outgassing process. Silica glass has been, and continues to be a subject of many studies, particularly those on diffusion and desorption of hydrogen and water from the material [11][12][13][14][15][16]. However, only a limited number of papers addressed more directly the issue of degassing of silica glass, particularly accumulation of the gases in closed ampoules [10,[17][18][19][20].…”

Chemical annealing of oxygen hole centers in bulk glasses

“…At temperatures greater than 500°C, the diffusing gas not only reacts with oxygen hole centers, but also is able to react with silica matrix in the following manner [18,24]:…”

“…We have tried to estimate the equilibrium constant K eq;2 by simulating the conditions in [21,27] using Eqs. (23) and (24) in cylindrical coordinates (i.e., considering that the reaction with silica matrix is only important). Equilibrium constants are chosen such that they not only match the measured [OH] profile, but also the maximum [OH] content measured at the outside edge of the sample.…”