Characterization and fracture property of different strontium-containing borate-based glass coatings for Ti6Al4V substrates

This work considered the effect of increasing Strontium ion (Sr2+) content on the structure of a series of glasses based on the B2O3-P2O5-CaCO3-Na2CO3-TiO2-SrCO3 series and their resultant fracture toughness when coated onto a surgical metal substrate. Six glasses with increasing Sr2+ content (0 to 25 mol%) were synthesized and subsequently characterized by X-ray Diffraction (XRD), Differential Thermal Analysis (DTA) and both Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) and Raman Spectroscopy. These techniques confirmed that increased Sr2+ content induced more non-bridging oxygens (NBOs) into the glass network. This would be expected to lead to de-polymerization of the glass structure, as would be evinced by lower glass transition temperatures (Tgs) as Sr2+ increased within the glass series. However, Tg was found to increase with Sr2+ addition, inferring that the strength of the ionic bond between strontium and oxygen (SrO) enhanced network rigidity. The glasses were coated onto Ti6Al4V substrates using an enamelling technique, and the critical strain energy release rates (GIC) of the resultant coating/substrate constructs were measured. The incorporation of 15-25 mol% Sr2+ into the glass network was found to significantly increased the toughness of the glass/Ti6Al4V constructs.