Study On The Preparation And Properties Of Fluorophlogopite/fluorapatite Glass-ceramics

According to the status and prospect of the current biomaterials research, the author's aim is to develop hard tissue restoration materials with good outlook for the stomatology and orthopaedics.Fluorphlogopite/fluorapatite glass-ceramics materials were prepared.These glass-ceramics materials were studied by using X-ray diffraction (XRD), scanning electron microscope/energy dispersive analysis of X-ray (SEM/EDAX), differential thermal analysis (DTA), Fourier transform infrared reflection spectrum (FTIR) and X-ray analysis. The relationship of the mechanical properties, crystalline phases and microstructures of the fluorphlogopite/fluorapatite glass-ceramics materials was discussed. The possible toughening mechnisms in this glass-ceramics materials were discussed. The growth mechanism and the kinetics of crystallization for the needle-like fluorapatite crystals were investigated. The bioactivity and the biocompatibility of this glass-ceramics materials were evaluated. The conclusions are given as below:(1) The glass-ceramics materials containing Ca-fluorphlogopite and fluorapatite as the main crystalline phases were prepared by melting method with two-step heat treatment. Fluorapatite crystals showed a needle-like morphology, which is similar to that in human bone, and thus made it much more biocompatible and bioactive. The plate-like Ca-fluorphlogopite endowed the materials a good machinability, therefore, the doctor can make it into various required shapes according to different bone defects.(2) With the increasement of the fluorapatite elements content in the raw glass, the mechanical properties of the fluorphlogopite/fluorapatite glass-ceramics materials are increased. When the nominal fluorapatite content increased to 50%, the mechanical properties of the materials arrived to the top value. Compared with the 45S5Bioglass, HA and Bioverit glass-ceramics, the fluorphlogopite/fluorapatite glass-ceramics materials showed a better mechanical properties, which agreed with the required scope of human's compact bone.(3) The toughening mechanisms of fluorphlogopite/fluorapatite glass-ceramics materials are residual stress mechanism and crystal whiskers pull-out mechnism. The aspect ratio of needle-like fluorapatite crystals are more than 10, which made a good contribution to the toughening effects.(4) The growth unit on the c(0001) crystal plane of the fluorapatite crystal showed a circle distribution, which provided a screw dislocation growth mechanism for the fluorapatite crystal. The needle-like fluorapatite crystals showed a conic boss at the tip of the needle, which is the endless growth source of the screw dislocation growth mechanism. The reseans for this screw dislocation are thermal stress field in crystals and interface mismatch between the crystal nuclei and glass matrix.(5) The values of the Avrami parameter, n and the dimensionality of crystal growth, m are found to be n≈2, m=1, which indicates that bulk nucleation is the dominant mechanism in fluorapatite crystallization. It is an indication of a one-dimensional growth of fluorapatite crystals with needle-like morphology and the crystals growth process was controlled by the interface reaction. With the increasement of the fluorapatite content, the activation energy of crystallization for the glass decreased. Thus the fluorapatite crystals precipitated more easier.(6) The animal experiments showed that the animals's diet and spirit are normal, and the animals had no toxic, haemolytic and allergic symptoms. The bad reactions, such as tumidity and bleeding did not appear in operation area, and the cut showed I period healing. These results elementarily showed the fluorphlogopite/fluorapatite glass-ceramics materials have a good biocompatibility.(7) The soaking in simulated body fluid and animal implant experiments showed the fluorphlogopite/fluorapatite glass-ceramics materials have a good bioactivity.