Bioactive Glass Ceramic Composites

Mica-based glass ceramics in the system Na2O-MgO-Al2O3-SiO2-F-were potential candidates as dental ceramics due to its machinability. The application of The CAD/CAM has expanded its application range, but its poor bioactivity restricts its application. The purpose of this study is to increase its bioactivity through adding hydroxyapatite and flouroapatite by powder metallurgy methods and casing methods. Mechanical properties and microstructure of glass ceramics were investigated by means of X-ray diffraction(XRD) scanning electron microscopy(SEM) thermal analysis(DTA) and mechanical testing. By means of P/M methods, we emphasis on the effect of the constituent and process variables on the glass ceramics properties and microstructure; by means of the fusing methods, we stressed on the effect of constituent changes and heat treatments on the phase separation,material properties and microstructure. The results are listed as follows:1) By means of P/M methods, at the same sintering condition, the mica platelets precipitated grow up and interlock with the increase of flourophlogopite contents. The mica platelets and the interlocked structure can deflect and branch crack, so can suppress crack expansion, which leads to the improvement of mechanical properties of glass ceramics. Also the sintering variables can affect material properties. Increase sintering temperature can bring about sinterability in the glass-ceramics. The mica platelets grow up and even lead to the interlocked structure as increase of sintering temperature which results in the improvement of mechanical properties.2) Hot-deformation can lead to the textured microstructure, which bring out better mechanical properties. Hot-deformation also can refine mica crystals.3) By means of casing methods, the phase separations occur in thestudied system. The mechanism changes with the increasing of flouroapatite contents. When the mass percent of flouroapatite is below 20%,the phase separation is achieved by nucleation and growth; as above it, the phase separation is achieved by spinodal decomposition. Also, the phase separation can bring great impact on the subsequent nucleation and crystallization.4) By means of casing methods, process parameters and composition changes have great influence on the mechanical properties and structure of material. As the crystallization temperature and time increase, the crystals coarsen and properties are improved. At the same condition, the mechanical properties decrease and then increase, the interlocked microstructure become incomplete interlocked, the color of glass-ceramics change with increase of flouroapatite content.