Structural characterisation of bioactive glasses

Abstract

Bioactive glasses are of great importance for orthopaedic and dental applications. The macroscopic properties of bioactive glasses, and in particular the rate of dissolution, can be tailored for specific applications by altering the compositions. It is therefore important to understand a compositional-structural-relationship as this will help when predicting glass properties and for optimising the design of future glasses for clinical applications. This thesis focused on the structural-characterisation of a wide range of bioactive glasses that are important for orthopaedic and dental applications. Experimental probes including neutron diffraction, high energy X-ray diffraction, solid-state NMR, supported by complimentary techniques such EXAFS, FTIR, XPS and XRD were used to characterise these glasses. A series of halide containing (CaF2 and CaCl2) bioactive glasses were successfully synthesised and characterised. Despite conflicting reports in the literature, the present study strongly suggests that minimal Si-Cl or Si-F bonds are present in these glasses. Instead halide ions were found to surround calcium ions. The silica network is therefore unaffected by the addition of halides ions. A series of novel zinc silicate-germanate glasses, with potential applications for bone cements, were investigated structurally. Studies revealed both Zn and Ge cations are in a tetrahedra coordination with no evidence of 5, 6-fold coordinations. An increase in the network connectivity of the glass will significant reduce its dissolution. The impact of incorporating Mg and Zn into bioglass was studied since both these ions can act as network intermediates. Whilst Zn was found to be solely tetrahedral Mg had significant fractions of 5 and 6-fold coordinations. The structure of Mg-BMG were investigated using neutron diffraction and molecular dynamics to help deconvolved overlapping partial structure factors. Isotopic neutron diffraction was further used to simplify the individual partial structure factors to further understand the structure of the glasses which is important to optimise its properties.