| Refractory clay is used as the raw material for the preparation of clay refractory materials.Electric porcelain waste is the waste produced in the electrical porcelain industry.The main components of both are SiO2 and Al2O3,and both are cheap and easily available raw materials.Using cheap raw materials or industrial solid waste which rich in SiO2 and Al2O3 to prepare Al2O3-SiC composite powders is a high-value utilization of raw materials or solid waste,and it is also a new way to develop Al2O3-SiC composite powders synthesis.In this paper,refractory clay and electrical porcelain waste were used as raw materials,and AlO3-SiC composite powders were prepared by electromagnetic induction heating and carbon thermal reduction method.Firstly,the feasibility of preparing Al2O3-SiC composite powder by electromagnetic induction heating method is explored,and the influence of induced current(400A,500A,600A)on the phase of the powder is studied,and the strength of current intensity was determined which can successfully synthesize Al2O3-SiC composite powder.Then,using refractory clay or electric porcelain waste as raw materials,the Al2O3-SiC composite powder was successfully prepared by the carbon thermal reduction method.The effects of heating temperature(1500 ℃,1550℃ 1600 ℃)and the addition amount of rare earth compound which is La2O3(0wt%,0.5wt%,1wt%)on the phase composition and micro morphology of the Al2O3-SiC composite powder were studied.The reaction mechanism during the sintering process was discussed.Finally,the Al2O3-SiC composite powder prepared from refractory clay or electrical porcelain waste as raw materials were added to the low-carbon magnesia-carbon refractories instead of part of the MgO powder(0wt%,2.5wt%,5wt%,and 7.5wt%).The effects of composite powder on the apparent porosity,bulk density,compressive strength,thermal shock resistance,oxidation resistance and slag erosion resistance of low-carbon magnesia-carbon refractories were systematically studied.The results obtained in this paper are as follows:(1)The electromagnetic induction carbothermal reduction method can successfully and rapidly prepare Al2O3-SiC composite powder.The apposite conditions for preparing Al2O3-SiC composite powder were induced current of 600 A and holding time of 15 min.(2)In the process of preparing Al2O3-SiC composite powder,the reaction temperature is the main factor affecting the phase of the final product.When the composite powder prepared from refractory clay was heated at 1500℃,the main crystalline phase of the product was mullite phase,the secondary crystalline phase was β-SiC and a small amount of Fe3Si phase.After heating at 1550℃,the diffraction peak strength of mullite phase is obviously weakened,but there is still some residual.After heating at 1600℃,the diffraction peak of mullite basically disappears,and the diffraction peak of α-Al2O3 appears.After heating at 1500℃and 1550℃,a large amount of amorphous glass phase exists in Al2O3-SiC composite powders prepared from electrical porcelain waste,and the formation of mullite phase is not obvious.When the heating temperature is 1600℃,the diffraction peak strength of amorphous glass phase decreases greatly.In comparison,the carbothermal reduction of electrical porcelain waste is more difficult than that of refratory clay.(3)The addition of rare earth La2O3 can obviously promote the preparation of Al2O3-SiC composite powder.La2O3 can speed up the oxygen transfer in the system,thereby increasing the overall reaction rate of the system,speeding up the crystallization and revivification rate of mullite,and finally promoting the crystallization of SiC.Approporiate addition of La2O3 can reduce the synthesis temperature.In addition,adding a small amount of La2O3 has no obvious effect on the microstructure of the composite powder.(4)The suitable addition amounts of Al2O3-SiC powders prepared from refractory clay to low-carbon magnesia-carbon refractories are 2.5wt%and 5wt%respecfirdy for slag corrosion,thermal shock and oxidation resistance.The addition of Al2O3-SiC composite powder can improve the bulk density,thermal shock resistance,oxidation resistance and slag erosion resistance of low-carbon magnesia-carbon refractories.The slag corrosion resistance of low-carbon magnesia-carbon refractories was improved when the addition amount was 2.5wt%.And the thermal shock resistance and oxidation resistance of low-carbon magnesia-carbon refractories were improved obviously when the addition amount was 5wt%,but the slag corrosion resistance was decreased.(5)The optimal addition amount of Al2O3一SiC powder prepared from electrical porcelain waste is 2.5wt%,and a small amount of Al2O3-SiC powder can improve the material density,thermal shock resistance,oxidation resistance and slag erosion resistance of the material.Excessive addition will destroy the material structure.This composite powder can improve the oxidation resistance of low-carbon magnesia-carbon refractories obviously.If the problem of excessive impurities in the composite can be solved,it will have greater application potential. |
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