Properties of porous silica glasses prepared via sol–gel process

Abstract

Porous silica glasses were obtained through sol–gel processing employing tetramethylorthosilicate (TMOS) as precursor, with HNO 3 and HF as catalysts. The gels were heat-treated at temperatures ranging from 400°C to 900°C. Some gels were γ-ray irradiated. Specific surface areas, pore size distributions and solid densities of the gels were obtained by nitrogen sorption and mercury pycnometry. Pore morphology was inferred through curves of nitrogen sorption hysteresis, and an evaluation of pore connectivities and permeabilities were carried out. The shape of the isotherms of gels submitted to different heat treatments was attributed to pores of cylindrical shape. The average pore size was controlled by the HF concentration. The average pore size distribution of gels irradiated with γ-rays decreased. We measured the properties of porous glasses when immersed in aqueous solution containing cesium chloride. Porous silica glasses heat-treated at temperatures above 650°C did not fracture when immersed in aqueous solutions with CsCl.