Microstructure And Properties Of Lightweight Sialon-Mullite Multiphase Refractory Materials

With the development of society,the energy saving and consumption reduction of high temperature industry has been paid more and more attention.Refractory materials are often used in the lining of high-temperature kiln,which playing a very important role in the need of saving energy and reduce consumption.In recent years,the lightweight of refractory materials is one of the important ways to achieve energy saving.This work takes Enshi special kaolin as the main raw material to develop lightweight Sialon-Mullite multiphase materials with high strength,low thermal conductivity and high wear resistance,which is of great significance for the expansion of lightweight refractory materials and the high value-added utilization of Enshi kaolin.This work first studies the influence of raw material composition and heat-treated temperature on the phase compositions,strength and wear resistance of mullite.Secondly,the effects of the type of reductant,the amount of addition and the heat-treated temperature on the synthesis of Sialon powder by kaolin carbothermal reduction and nitridation were studied.On this basis,the influence of Sialon phase introduction mode,introduction amount,sintering atmosphere,heat-treated temperature and other factors on the phase compositions,microstructure,strength and wear resistance of lightweight mullite matrix refractories was systematically studied.According to the above studies,the following conclusions can be drawn:（1）lightweight mullite materials can be synthesized from fine kaolin powder,high bauxite powder,α-Al₂O₃ powder and silica powder.The formation of columnar mullite is beneficial to enhance the strength of the material and correspondingly improve its wear resistance.（2）Using kaolin,reductant（carbon black,metallic aluminium and elemental silicon powder）as the main raw materials,and the composite powder with the relative content of Sialon was 67.1%was prepared by heat reduction at 1500°C for 3 h.heat-treated.Compared with carbon black-silicon composite,carbon black-aluminum and carbon black-aluminum-silicon composite have stronger reduction capacity.Simultaneous introduction of silicon,aluminum and carbon black facilitates the conversion of kaolinite to Sialon phase at 1400-1500°C.（3）Lightweight Sialon-Mullite composites can be prepared by using kaolin and pre-synthesized Sialon composite powder and activeα-Al₂O₃ micropowder as main raw materials,and incubated at 1500-1600°C for 3 h under nitrogen atmosphere.Introducing part of the pre-synthesized composite powder,so that the Sialon content in the sample is 10wt%,the compressive strength at the heat-treated temperature of1600°C can reach 189MPa,and the apparent porosity is kept at about 20%.It is difficult to observe the Sialon phase after heat-treated in air atmosphere,so it can be speculated that most of the Sialon phase has been oxidized,but the compressive strength has improved.（4）Using kaolin,metal aluminum powder,elemental silicon powder,activeα-Al₂O₃ micropowder,carbon black and pre-synthesized Sialon composite powder as main raw materials,the material of Sialon-Mullite can be prepared under the nitrogen atmosphere at 1500-1600°C for 3h,the apparent porosity can be more than 20%.But the material strength and wear resistance decreased with increasing Sialon volume.The sample with a pre-synthesized Sialon composite powder as a seed crystal can be subjected to a compressive strength of 183 MPa after heat-treated at 1600°C.Compared with the lightweight mullite material,the compressive strength of the two is comparable,but the former has a lower pressure.Thermal conductivity and wear rate.heat-treated...