Surface degradation behaviour of sodium borophosphate glass in aqueous media: Some studies

摘要

The degradation behaviour of phosphate glass with nominal composition, 40Na_2O-10BaO-xB_2O_3-(50-x)P_2O_5, where 0 <=x <= 20 mol percent , was studied in water, HCl and NaOH solutions at room temperature to 60 deg C for different periods extending up to 300 h. These glasses were synthesized by conventional melt-quench technique. Dissolution rates were found to increase with B_2O_3 content in the glass. The dissolution rates for the glass having 10 mol percent B_2O_3 were found to be 0002 g/cm~2 and 0015 g/cm~2 in distilled water and 5 percent NaOH solution, respectively, at room temperature after 225 h of total immersion period, whereas it increased considerably to 0.32 g/cm~2 in 5 percent NaOH at 60 deg C after 225 h. However, glass samples with x = 15 and 20 mol percent B_2O_3 were dissolved in 5 percent HCl solution after 5 h immersion. The degradation behaviour has been correlated with the structural features present in the glass. The optical microscopy of the corroded surface revealed that the corrosion mechanism were different in acid and alkali media.