Effects of zircon on porous structure and alkali durability of borosilicate glasses

Additions of zircon (ZrSiO4) were made to yield alkaline durable porous glasses based on the sodium borosilicate glass system. The glasses were characterised using differential thermal analysis (DTA) to identify the glass transition temperature and crystallisation temperature. The selected heat-treatment caused the glasses to phase separate by a spinodal decomposition mechanism. X-ray diffraction (XRD) was used to identify the crystalline phases. Acid leaching was used to remove the borate phase and create a porous structure. Scanning electron microscopy (SEM) revealed classic interconnected porous morphologies, while energy dispersive X-ray (EDX) analysis confirmed the presence of zirconium (Zr) in the porous silica-rich skeleton. Some of the porous glasses exhibited sharp and uniform pore distributions. Mean pore size ranged from 40 nm to 200 nm with a surface area from 5 to 35 m2/g depending on glass composition and heat-treatment time. Zircon containing porous glasses are 3–4 times more alkali resistant than the parent sodium borosilicate glass.