Effect of heat treatment on 7Na2O–23B2O3–70SiO2 glass

Porous 7Na2O–23B2O3–70SiO2 glass was successfully fabricated by acid leaching treatment and phase-separation. The 2 mol/l hydrochloric acid (HCl) solution treatment was used for 24 h. Thermal analysis and X-ray diffraction were used to identify the temperature range of heat-treatment. The average pore size and the pore volume were investigated by a nitrogen adsorption instrument, and SEM was used to characterize the appearance of the porous glass. The results show that the average size of pores changed from 3.75 nm to 3.03 nm when heat treated at 640–680 °C for 6 h. In addition, when heat treated at 640 °C for 6–24 h, the pore size fell from 3.75 nm to 3.66 nm. The surface area and pore volume become larger with the increase in both temperature and heat treatment time.