Effect of SiO<inf>2</inf>/B<inf>2</inf>O<inf>3</inf> ratio on the thermophysical and wetting properties of borosilicate glass sealant for glass-metal joint

The decrease of SiO2/B2O3 ratio in the glass sealant composition from 6.23 to 0.74, leads to reduction in its glass transition temperature Tg (590 °C–507 °C) and its crystallization temperature Tc (820 °C to 710 °C). The percentage change in weight loss during heating of glass sealant powder decreased from 78% to 63% with decrease in SiO2/B2O3 ratio. The density of glass sealant increased from 1.47 to 2.11 g/cm3 with decrease of SiO2/B2O3 ratio in the glass sealant composition. The glass sealant composition with lowest SiO2/B2O3 ratio of 0.74 and having a chemical composition (40SiO2-54B2O3-2Al2O3-4Na2O) was considered to be the optimum sealant where the maximum adhesion strength of 2.5 N/mm2 was obtained along with lowest value of contact angle 17° and highest wettability (spreading area value of 585 mm2) of the glass sealant. The optimum value of glass transition temperature (Tg) 507 °C and crystallization temperature (Tc) 710 °C was obtained corresponding to glass sealant composition with the lowest SiO2/B2O3 ratio.