| Nowadays, ceramic materials as a new type of engineering structural materials are used wildly in aerospace, automobile, metallurgy, chemical industry, machinery and other areas. Machinable glass-ceramic materials is receiving more and more attention from people because of it's excellent aesthetic properties, machinability and Mechanical properties. Currently, Fusion method, Sintering method and Sol-Gel method are used commonly to prepare Glass-Ceramic at home and abroad. The first two method are a complex process which use too much energy. Particle prepared is large size. The sol-gel method is also not suitable for industrial production because of high costs.So the fabrication of mica glass-ceramics is the research emphasis.The preparation method of glass-ceramics in this paper has been improved. According to the mechanism of liquid-phase homogeneous precipitation method, nano-grade sodium fluorophlogopite (NaMg3AlSi3O10F2) glass-ceramic precursor powder was preparated. The machinable mica glass-ceramic powder containing fluorophlogopite (NaMg3AlSi3O10F2) as the main crystalline phase had obtained by heat-treated the precursor powder. After molding and sintering, the mica glass-ceramic was got. By means of DTA/TGA, TEM, XRD, FT-IR, SEM and ESCA, the phase change, microstructure and the evolution of the structure in the preparation of the material were studied. The influences of ceramic composition and structure on its performance were discussed. As well as the machinability of mica glass-ceramic was tested. The main results of the thesis are showed as follow:The nano-precursor powder was preparated by selecting several water-soluble compounds containing Na+, Mg2+, Al3+, Si4+, F- as raw materials of liquid-phase reaction and controling the process parameters. The size of the particle is in the range of 10-20nm, and the secondary particles size were about 100nm. The particle is uniform and have little agglomeration. The morphology of the powder precursor particle prepared is nearly spherical that is a typical amorphous silicate powder. It was found that the fluorophlogopite is to crystallize at about 600℃, and have the largest and least nucleation rate at about 650℃and 700℃respectively. The crystallization temperature at 950℃, the nuclei growth rate of mica glass-ceramic are higher. Meanwhile, a small quantity of nepheline(NaAlSiO4) and forsterite(Mg2SiO4) are also crystallized out in the process. The best heat treatment process is nucleated at 650℃for 2h and crystallized at 950℃for 0.5h. The powder treated by the crystallization heat treatment is mainly lamellar. And the crystallization degree reached about 45%. It was found that nucleation temperature have the greatest impact on crystallization behavior of powder. And then the crystallization temperature, finally holding time.Powder was moulded step by step using one-way pressure. Firstly powder was pressed under the pressure of about 40MPa and keep one min, then pressed to 100MPa and keep two min. The sintering craft is heat insulation 2h at 550℃and 1120℃respectively.The resultes show that the inner main crystal structure of the mica glass-ceramic is formed by lamellar sodium fluorophlogopite which path length is about 10μm, The crystallization degree of the mica glass-ceramic is reached about 52%. The relative density of ceramic is reached 96.8%. It was found that the content of sodium fluorophlogopite crystals increased firstly and then decreased with increasing sintering temperature. Granular forsterite and nepheline of short column structure will both appear if the temperature is too low or too high. The variation trend of this tow crystals opposite to sodium fluorophlogopite crystals.Microstructure has a significant impact on the performance of glass-ceramic. The three-point bending strength rose to a maximum value followed by a fall with a rise of sintering temperature, The suitable sintering temperature is 1120℃. In this temperature environment, glass-ceramics have the highest degree of crystallization. The long-thickness ratio of lamellar crystals is larger, and the degree of interwoven crystals is higher. The three-point bending strength is reached 116.76MPa, and the hardness is 3.23GPa. Experiments confirmed that the material has good machinability.
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