Characterization of sodium and calcium addition on immediate aqueous interactions of binary borate glasses by dynamic vapour sorption with in-situ Raman

This study describes a novel technique; dynamic vapour sorption (DVS) with in-situ Raman spectroscopy, to investigate the reactivity and mechanisms of aqueous interactions of bioactive borate glasses (BGs). Two melt-derived binary-BGs; (70)B2O3-(30)Na2O and (70)B2O3-(30)CaO (mol%), were investigated to compare the effect of sodium and calcium addition on boron coordination and aqueous interactions, via DVS and dissolution in deionized water. DVS, which gravimetrically measures the effect of exposing BGs to a controlled relative humidity, was applied to quantitatively evaluate their glass-water reactivity. Meanwhile, in-situ Raman monitored structural changes in real-time to demonstrate their different aqueous reactions and characterize vapour- and water-induced crystallization of sodium-borate glasses. In conclusion, correlation of structural changes and reaction rates between vapour- and water-induced reactions validated the coupling of DVS and in-situ Raman as a more sensitive approach to characterize aqueous reactivity and reactions of BGs compared to traditional methods, such as submersion in aqueous solutions.