Analysis of gas release from vitreous silica

Gas release measurements were carried out for ‘wet’ (T7030, Vitreosil, T1030, Heralux, Suprasil II) and ‘dry’ (T2030, GE214, SG25A, SG25SC, SG25SF, T7032, Suprasil W) vitreous silicas in the temperature range from room temperature to 1000° C by using a constant heating rate method. It was found that main gases released from ‘wet’ and almost ‘dry’ vitreous silicas were H 2 and H 2O, while those from Suprasil W were CO and O 2. Two maxima in the amount of gas released at around 500 and 900°C were clearly observed for H 2 for high OH containing vitreous silica, i.e., T7030, T1030 and Suprasil II. Low and high temperature H 2 releases are explained in terms of a diffusion process and a dissociation reaction process of SiOH and/or SiH, respectively. The molar extinction coefficients for IR stretching bands of SiOH and SiH are estimated and are found to be 7.0 ± 0.7 and 4.0 ± 0.3 m 2 mol −1, respectively.