Preparation and Characterization of Nano porous Silica Glasses for Nuclear waste Immobilization

The current study investigates crystallization and phase separation of a borosilicate glass composition in the system Na 2 O–CaO–Al 2 O3–B 2 O 3 –SiO 2 used for nuclear waste immobilization. At first, base glass composition was prepared by mixing and homogenizing of pure raw materials, melting in an alumina crucible and then casting in a stainless steel mold. Mo 2 O 3 was added in constant values of 0.5, 1.5, 2.5, and 3.5% mole. XRD analysis was carried out to ensure no crystalline phases were formed. Heat treatment was performed at temperature intervals of 620, 650, 680 and 710°C. To study phase separation creation, SEM analysis was carried out. In the next step, acid leaching of phase-separated glasses was performed. Porosity analysis and measurement of specific surface area by BET were performed on acid-leached samples. The results show all samples demonstrate different amounts of phase separation. Also, the highest specific surface area was related to the sample containing 1.5% mole Mo 2 O 3 with two acid-washing steps.