【正文】 ch situation, in foreign countries (especially the American) have prepared highperformance transparent AlON ceramics and deploy practical application. The research of AlON ceramic was developed late and the independent technology of largesize high transparent AlON ceramics is not obtained. In addition, as far as the present international study, the high transparent AlON is very difficult to produce as its plicated structure. The temperature for singlephase AlON powder and ceramic production is relative high. The thermal data of this material is not enough and the study on phase diagram of this material is inplete. So it is very important to develop the study of AlON preparation.In this paper, AlON powder was synthesized by modified aluminothermic reduction and nitridation method using Al and Al2O3 powders as raw materials. The preparation technology and effect factors are systemic research and the art for high quality AlON powder production is obtained. Transparent AlON ceramic was 四川大學(xué)博士學(xué)位論文8prepared with this homemade powder and the technology for high transparent sample was obtained. And the phase position, density, transmittance, micromorphology, hardness, strength and hardness were examined. 1. Synthesis of AlON powder The pure AlON powder was prepared by aluminothermic reduction and nitridation method with microsized Al and nanosized Al2O3 powders ballmilled in N2 atmosphere (not in the NH3 atmophere which reported by Weifang Miao)for 24h and calcined in N2 atmosphere. sintering temperature and the ratio of raw materials are the key factors of AlON powder fabrication. Singlephase AlON powder is not pound with rawmaterial of stoichiometry. Reducing the amount of Al from % to 11wt%, singlephase AlON powder(with Al5O6N position) can be obtained by homemade γAl2O3 powder as raw material and with at 1800℃ for 3h. The aluminothermic reduction and nitridation process can be divided into three sections. The first section is low temperature (room temperature800℃), the second section is medium temperature (8001550℃) and the third section is high temperature (15501800℃), and the reaction for each section is Al powder melting, AlN formation and Al2O3 and AlN solid solution. AlN was first produced and then the solid solution of Al2O3 and AlN was pound. AlON was first detected at 1625℃, moreover, reaction velocity increased at 1650℃ and reaction was pleted at 1800℃ for 3h. Thermodynamic analysis showed Al5O6N formation started at 1887K, which was agreement with our experiment. Before AlON phase transition, Al was not stable and transformed Al2O3 or AlN, especially transformed AlN because of N2 atmosphere. The results showed that there is Al2O3 stable in the furnace atmosphere. Therefore, Al2O3 is first produced with remain O2 and the mount of Al2O3 is increased in this section. Stable region of AlON is narrow during this temperature region, so, it is very necessary to heating lowly and carry out insulation for enough time. Due to the instability of Al2O3 in this section, he stoichiometry raw material can not produce singlephase AlON . 四川大學(xué)博士學(xué)位論文9The reaction dynamics showed that the rate of reaction process was mainly depends on the anion, especially for N ion diffusion, so it is necessary to rise high temperature and hold temperature long time. In our experiment, smallsized γAl2O3 and AlN is beneficial to inward diffusion of N ion, which promotes process of reaction.. The mercial samll sized and welldistributed Al2O3 powder using as rawmaterial could decrease calcining temperature about 100℃. It was found that different ratios of rawmaterial can effect on sintering temperature of singlephase AlON. When the amount of γAl2O3 was more than 50%, singlephase AlON was obtained at 1700℃, contrarily, calcining temperature need to increase by 50℃.The grain size of AlON powder made by homemade Al2O3 powder milled for 24h is about 3～10μm. Though the grain shape of few large grain is not regular, the grain shape of small grain is spherical, and also it is good dispersion. The average grain size of AlON powder prepared with five different ratios mercial Al2O3 powder are all blow 5μm and with good dispersion. The powder with pure γAl2O3 as rawmaterial has best properties. The optimum technical of preparation of AlON powder in our work as follow: using Al ( wt%) and mercial γAl2O3 powder as starting material and calcined at 1700℃ for 3h.2. The preparation of transparent AlON ceramicThe biscuit with the diameter of 20mm was prepared with polyvinyl alcohol as adhesive and by dry pressed plus cold isostatic pressed method. It is necessary to eliminate adhesive from powder, discharge technology of green body through tests as follows: The temperature slowly increase to 120℃ for from room temperature and then increase to 500℃ for 2h in order to remove the anic matter.Transparent AlON ceramic can be reach with AlON powder prepared by homemade Al2O3 by sintering at 1880℃ for 10h. The sample is grey black and internal inhomogeneous, transmittance of sample is improved with prolonging of heat preservation time. And the densification was due to the mass transfer by diffusion.四川大學(xué)博士學(xué)位論文10Comparing with the AlON powder prepared by the homemade Al2O3 powder as rawmaterial, the AlON powder prepared by mercial Al2O3 powder has better sintering activity. Meanwhile, transparence of ceramic depend on sintering temperature, the transparence of ceramic at 1880℃ is higher than at 1860℃, more importantly, the transparence of ceramic is sensitive to the amount of sintering additives. An optimum additive of Y2O3 is %. The Mechanism of Y2O3 additive as follows: 1) the lattice distortion of main crystal phase is formed in order to promote sintering of ceramic. 2) The growth of grain is restrained by solute towed mechanism and it is benefit for sintering transparent ceramic.