Study On The Preparation And Tribological Properties Of Fluorphlogopite/Fluorapatite Glass-ceramics

Glass-ceramics have excellent properties such as high mechanical strength, good wear resistance and high chemical resistance, which make it have great prospect in architecture, electronics, space and aircraft, medicine, and so on. Glass-ceramics is prepared using oxide such as SiO2, MgO, Al2O3, etc. The source of the raw materials of glass-ceramics is widely, and the energy consumption and pollution during the process of produce and using of glass-ceramics is lower, therefore glass-ceramics has obtained great research and production. Fluorphlogopite/fluorapatite has good machinable property, bioactivity and biocompatibility, has obtained great developments as dental and orthopedics material, but in these fields, the material must has better mechanical and friction and wear behaviors. But recently, the researchs are mostly focus on the mechanical property and biocompatibility, less in research on friction and wear properties. Apatite is always used as filler in industrial friction material fields, and HA and fluorapatite glass-ceramics both contains apatite, so we believe there is possible that they can be used in industrial friction material fields.The design of the glass matrix of fluorphlogopite/fluorapatite glass-ceramics is based on the silicate phase diagram, and the material was prepared by melting method, the phase compositions and microstructure of the glass-ceramics were analyzed by X-ray diffraction, scanning electronic microscopy and energy spectrum analysis, thermal analysis, transmission electron microscope, atomic force microscope. The relation between the crystalline phase and mechanical property, friction and wear property of the glass-ceramics were investigated. In order to investigate the feasibility of glass-ceramics were used in industrial fields, glass-ceramic and HA matrix composites were prepared by powder metallurgy method, the friction and wear behavior of the composites were investigated. It was found that copper is important to stabilize the friction state of the composites, and the glass-ceramic matrix composite has better friction and wear behavior under high temperature. The thesis contains80 pictures,14tables,151references. The main research contents and results are as follows.(1) The glass-ceramic was prepared by melting method and stepped heat treatment. Fluorphlogopite crystals showed a block or flake shaped morphology, fluorapatite crystals showed a needle-like morphology.(2) The growth mechanism of fluorapatite is screw dislocation growth. The conic tip of the needle is the growth source of the screw dislocation. The growth rate of the c crystal plane is faster than others, so that fluorapatite crystal shows a needle-like morphology.(3) With increasing of the raw material of fluorapatite in the glass-ceramics, the crystallinity of the glass-ceramics was increased markedly, and the mechanical property was improved. When the nominal content of fluorapatite come to40%, the mechanical behavior of the glass-ceramics, such as bending strength, fracture toughness, and micro-hardness reached to the top value, that was93.22MPa,3.74MPa-m1/2,698MPa.(4) With increasing fluorapatite, the friction coefficient of glass-ceramics increased and become stable. When the nominal content of fluorapatite increased to40%, the wear rate of the glass-ceramics was lowed to a third of the original.(5) When there was only fluorphlogopite crystal, the mechanical property is limited. The surface has poor anti-shear ability, so the friction coefficient was low and the wear rate was high, and the surface roughness is high. With increasing fluorapatite, the mechanical property is improved, and the anti-shear ability was also improved, so the friction coefficient increases and the wear rate decreased, and the surface roughness was reduced.(6) When low in fluorapatite, fracture and delamination were easy to happen on the surface, so most of the debris is big in size. The debris and surface is high in residual glass phase, under the effect of the energy accumulated during wear tests, the residual glass phase softened and showed plastic deformation, so the debris showed viscous and the agglomerate phenomena happened. With increasing fluorapatite, the size of the debris was reduced and the agglomerate phenomena were decreased.(7) HA based composite was fabricated by hot pressing with HA, copper fibers, carbon fibers, mica, and potassium titanate. The constant speed wear test showed that with increasing Cu, the friction coefficient was lowed and stabilized, and the wear rate is decreased.(8) Glass-ceramics based composite was fabricated by hot pressing with fluorphlogopite/fluorapatite glass-ceramics, copper fibers, carbon fibers, potassium fitanate, boron nitride, antimony sulfide. The constant speed wear test show that the friction coefficient tended to steady at0.37during100-350℃, and the composite showed a good wear resistance and free from interfere of temperature.(9) The adding of copper fibber could help to form a friction film on the surface of composites, which make contribution to the stable friction coefficient and the decreased wear rate.