Influence of Al2O3, ZrO2 and TiO2 on the properties of the microporous glasses from the system Na2O-B2O3-SiO2

Abstract

Glasses from the Na2o-B2O3-SiO2 system, doped with AI2O3, ZrO2 and TiO2, were thermally (in the temperature range of 420 to 700 °C) and chemieally treated. During thermal treatment, separation of the borate phase from the silica skeleton occurrred resulting in the formation of an interconnected microstructure. The borates were in the form of small drops joined to each other. In the course of chemical treatment the borates were leached in water and water solutions of acids or bases with the glass becoming very porous. The experiments showed that ZrO2 and TiO2 caused an increase in pore diameter at defmite leaching times. AI2O3, however, decreased it, so that glasses doped with AI2O3 have a greater specific surface. In this case a double-pore distribution occurred. Porous glasses may find application in many branches of science and engineering. The applications depend on the internal arrangement, size and shape of pores. These parameters may be in a wide range modified by a change of the chemical composition. Testing structure and properties of microporous glasses from the system Na2O-B2O3-SiO2 with different additions was the main aim of this work. The following testing methods were applied: DTA, XRD, TEM, infrared spectroscopy and sorption porosimetry.