In-situ characterization of borate glass dissolution kinetics by μ-Raman spectroscopy

• Published in: Journal of non-crystalline solids 2015-10, Vol.426, p.116-124
• Main Authors: George, Jaime L., Brow, Richard K.
• Format: Article
• Language: English
• Subjects: Anions; Borate glass; Borates; Dissolution; Glass; Monitoring; Raman; Reaction kinetics; Spectroscopy
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2015.07.003

The dissolution behavior of binary and ternary Na–Ca-borate glasses in phosphate-containing aqueous solutions was studied by micro-Raman spectroscopy. Raman spectra collected from the solutions provided information about the types and concentrations of borate anions released from the glass as a function of time. Boric acid molecules (H3BO3) and tetrahydroxyl borate anions (B(OH)4−) can be detected in solution and their relative concentrations depend on the solution pH. By monitoring the areas under peaks associated with these two species, the overall borate release rates and variations in solution pH were determined. Binary Na-borate glasses exhibit linear dissolution kinetics and the dissolution rates decrease with Na2O-contents up to 30mol%. The ternary Na–Ca-borate glasses exhibit parabolic dissolution kinetics because of the formation of a surface Ca-phosphate phase, and these reaction rates also decrease with increasing [Na2O+CaO] content. •Raman spectroscopy describes reactions of borate glasses in phosphate solutions.•Borate speciation provides information about solution pH.•Dissolution rates depend on the type and concentrations of modifying oxides.•Charge-balanced tetrahedral borate sites react more slowly than trigonal borate sites.•Dissolution kinetics changes from linear to parabolic when Ca-phosphate layers form.