Glass-matrix biocomposites: synthesis and characterisation

CaO-SiO2 base glass-matrix/Ti particle biocomposite coatings on Ti6Al4V substrates have been prepared by means of Vacuum Plasma Spray. The base glass is considered bioactive, because, when soaked in a fluid that simulates the inorganic ion concentration of human plasma (SBF), it develops a bonelike apatite layer on its surface. The aim of this research activity was to toughen this brittle bioactive material and to broaden its biomedical applications. Pure titanium was chosen as toughening phase because of its well-known biocompatibility, and Ti6Al4V alloy as substrate because of both its biocompatibility and its mechanical reliability. At first the composites were prepared as bulk materials, by means of a simple sintering process. Then, by ball-milling the sintered composite, the as-obtained “composite powders” were sprayed by Vacuum Plasma Spray (VPS) on the substrate. By means of Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC), the characteristic temperatures of the base glasses were determined. The thermal properties of mixtures of glass powders and different vol% Ti particles were studied by means of DTA, DSC, hot-stage microscopy, and dilatometry, with the aim of optimizing the sintering conditions. Both the bulk and the coated samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), compositional analysis (EDS), Vickers indentations, and leaching tests after soaking in a simulated body fluid (SBF).