Synthesis Of Al₂O₃-SiC Composite Ceramic Powders By Carbon Thermal Reduction Method

The influencing factors on preparing Al₂O₃-SiC composite ceramic powders by carbon thermal reduction method were studied systematically. Firstly, the effect of variety of raw materials on reaction was compared. Then the effects of technological conditions on the reaction were investigated, including temperature, soaking time, carbon content and particle size of raw materials, etc. Finally, the effect of catalysts and the addition of catalysts on the reactions were explored.The results show that Al₂O₃-SiC composite ceramics powders can be synthesized under the condition of proper C/SiO₂ mole ratio and over 1600℃, with clay, waste clay brick powder or rectorite as raw materials and anthracite coal or carbon black as reducers. XRD peak of SiC phase intensified with higher temperature. The reduction effect of carbon black is better than anthracite coal.XRD peak of SiC phase increased with the higher C/SiO₂ mole ratio and the most amount of content of SiC can be obtaind when the C/SiO₂ mole ratio is 3～4. It is obvious that increasing carbon content properly will promote the reaction.The content of SiC and corundum phases also increased with more soaking time and more grinding time, which means smaller grain size of raw materials. Apparently more soaking time and more grinding time will be beneficial to the reaction process.Compared with the reactions without catalyst, using Fe₂O₃, FeCl₃, Fe(NO₃)₃, Co(NO₃)₃ or Ni(NO₃)₃ as catalysts could accelerated the carbon thermal reduction reactions. Moreover, the reactions will be further promoted when increase the amount of catalyst properly.SEM results demonstrated that SiC phase interleave distributing in the corundum phase in the Al₂O₃-SiC composite materials. Catalysts are impetus to the growth of SiC and corundum.