Methods: Hertzian Indentation, Micro- and Nano-tomography, Scanning Electron Microscopy, Deep Inelastic Neutron Scattering, Neutron Diffraction, Density Functional Theory
Results: Micro-CT (uCT) was used to characterise the volumetric-porosity of fully-cured biocompatible glass samples, accurately tracking fracture branches through three Cartesian axes, in addition to incomplete bottom-initiated cracking. Nanocomputed tomography analyses supported the reliability of the uCT results. Complementary 2-Dimensional fractographic investigation was carried out by optical and scanning electron microscopies, resulting in qualitative feature-resolution towards identification of fracture characteristics. The combined 3-D qualitative assessment of microstructure and fracture features, complemented by 2-D methods, provided an increased understanding of the properties and subsequent mechanism of mechanical failure in these bioglasses. Specifically, cracks preferentially linked the pores and propagated along the glass-matrix interface. Parallel studies of the setting kinetics and associated reaction dynamics were characterised using evolved neutron scattering techniques. Complementary high-level quantum chemical determinations were in agreement and highlighted the need for increasing matrix packing towards enhancing toughness in these materials.
Conclusions: The multi-disciplinary approach described herein provides the most effective means towards the rational characterisation of mechanical failure in biocompatible glasses. The combination of neutron scattering complemented by high-level quantum-mechanical simulations provided insight into setting dynamics. The methodological development is exploitable on related biocompatible systems and represents a new tool towards the rational characterisation, optimisation and design of novel materials for clinical service.