Effect of SiO2/B2O3 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 degrees C-507 degrees C) and its crystallization temperature Tc (820 degrees C to 710 degrees 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/cm(3) 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 (40SiO(2)-54B(2)O(3)-2Al(2)O(3)-4Na(2)O) was considered to be the optimum sealant where the maximum adhesion strength of 2.5 N/mm(2) was obtained along with lowest value of contact angle 17 and highest wettability (spreading area value of 585 mm(2)) of the glass sealant. The optimum value of glass transition temperature (Tg) 507 degrees C and crystallization temperature (Tc) 710 degrees C was obtained corresponding to glass sealant composition with the lowest SiO2/B2O3 ratio.