Structure of Hydrated Borate Glasses

Oxide glasses are one of the most important material families, but applications are severely restricted by their main drawback, i.e., high brittleness. Typically, the presence of water leads to easier crack initiation and growth, but recent work has shown that certain glass compositions (e.g., aluminoborates) exhibit an opposite effect. That is, their crack initiation resistance increases significantly upon hydrothermal treatment. There is thus a need to understand glass-water interactions, particularly in borate glasses. Our aim with the current proposal is to characterize the structure of hydrated borate glasses by collecting neutron scattering data at the SANDALS beamline from xH2O·(1-x)B2O3 glasses with x = 0, 0.1, 0.2, 0.33, and 0.4. By doing so, we will obtain the neutron structure factor to high Q values, enabling high-resolution computation of the pair distribution function and thereby quantifying changes in bond lengths and coordination numbers with water content. In total, we will study 13 different glass samples with varying H2O/B2O3 ratios and isotopic substitutions, requiring 5 days of beamtime. The neutron data will be combined with additional structural characterization (solid state 1H, 11B, and 17O NMR and X-ray scattering) and modelling (empirical potential structure refinement). This will enable us to build detailed structural models of the hydrated borate glasses, and in turn better understand how water influences the mechanics of borate-based glasses.