Phase separation in pyrex glass by hydrothermal treatment: evidence from micro-Raman spectroscopy

In this work, we investigated the formation of porous silica matrix obtaine d by hydrothermal treatment under saturated steam condition from Pyrex (R) glass. This investigation was carried out by scanning electron microscopy ( SEM), infrared spectroscopy (IR), X-ray powder diffractometry (XRD) and Ram an microscopy. We observed the presence of connected and homogeneously dist ributed pores in a non-crystalline silica phase and a detectable interface between silica and remnant glass phases resulting in a framework similar to asymmetric membranes. The results indicate that the process of phase separ ation takes place at lower temperature than that of glass-transition on the surface of the glass phase. Essential reaction between water and silica at supercritical condition together with the formation and leaching of solubl e phase contribute to obtain porous silica matrix, (C) 2001 Elsevier Scienc e B.V. All rights reserved.