Study On Sintering Process Of Sialon-based Refractories By Carbothermal Reduction And Nitridation Of Microcrystalline Muscovite

The natural aluminum silicate minerals are rich in resources, distribute in general, easy mined, choiced, processed, and costs are relatively low, so in the study of Sialon synthesis,they have been one of the hot spots. This paper used the natural microcrystal muscovite as raw material sintered Sialon-based refractory material.In this paper, large number of literatures were referenced to design the specific experiment scheme, such as reaction temperature, heating curve, the reaction of the nitrogen flow, the microcrystalline muscovite particle size and so on. And then used microcrystal muscovite as raw material, carbon black as reducing agent, nitrogen as nitrogen source, we sintered Sialon-based refractory material with the vacuum hot-pressing furnace.The microcrystal muscovite's proportion was 73%, carbon's was 27%, the sintering temperature was 1350℃and 1550℃.According to the change of the sintered samples'thickness (displacement) during the sintering process and testing results such as XRD, SEM, EDAX, flexural strength, Vickers hardness and so on of sample, we researched the phase transition characteristics of the formed products in the sintering process, and based on this, analysis the reaction mechanism of microcrystalline muscovite carbothermal and nitridation reaction during the sintering process.The results were as follows:(1)The sintered phase compositions of the sample were Si₆AlO₆N₅,mullite,AlN,Al₂O₃ at 1350℃. The main reactions of the experiments were:α-quartz started to changeα-Tridymite at 870℃,and produced mullite; mullite, SiO₂ occurred reduction nitridation reaction formed Si₆AlO₆N₅ under the effect of the C; part of the Al₂O₃ nitrided and generated AlN.(2) The sample of 1550℃'s phase composition isβ'-Sialon,Si₆AlO₆N₅,mullite,AlN,Al₂O₃ , the reaction process roughly include: the further nitridation, generating new nitridationβ'- Sialon, micro-crystal muscovite second mullite petrochemical, and there is some Al₂O₃.(3) The samples is brown, the reason is that content of Fe₂O₃, FeO is higher, with the Fe³⁺ more, the Fe²⁺ less.(4) Porosity of the sample is very high, greatly affected the bending strength and hardness of the samples, if we can reduce the porosity of the sample, the sample performance is significantly improved.