| In this paper, the utilization of zircon by means of materials synthesis was studied using zircon as the main starting materials, which developed a new route for the comprehensive application of mineral resources. Based on the thermodynamic analysis, ZrO2-SiC and ZrN-Si3N4 composite powders were prepared by carbothermal reduction (nitridation) reaction, and the synthesis mechanisms of them were discussed. Furthermore, the ZrO2-SiC composite powder was applied into Al2O3-C refractories to study the effect of its addition on properties of the refractories. In addition, the Al2O3-ZrO2-SiC-C refractories were prepared by in-situ reaction, and the feasibility of in-situ synthesis of ZrO2-SiC composite in corundum and Al2O3-C refractories was discussed. Moreover, zircon, carbon black, alumina micropowder and fused corundum were used as the starting materials for the preparation of ZrN-Sialon bonded corundum composite to study the properties of the material. The following conclusions were obtained.(1) The effects of partial pressures of CO, SiO, ZrO, N2 and O2 gases on the phase stability in Si-C-O, Zr-C-O, Zr-Si-C-O and Si-C-N-O systems.(2) The effects of heating temperature and La2O3 addition on the synthesis process of ZrO2-SiC composite powder were studied, and the synthesis mechanism and the catalysis action of La2O3 were discussed. The results show increasing the heating temperature and the addition of La2O3 were favorable for the decomposition of zircon and the formation of SiC in this experimental condition. The proper temperature to synthesize ZrO2-SiC composite powder was 1600℃while the sample without La2O3 addition, and the temperature was decreased to 1530℃when the sample added with 2% La2O3.(3) The Al2O3-C refractories were prepared by using fused corundum, natural graphite and phenolic resin as the starting materials and the synthesized ZrO2-SiC composite powder and industrial SiC powder as the additives to investigate the effects of their additions on properties of the refractories, and the mechanisms of oxidation resistance and thermal shock resistance of the additives were discussed. The results show that the bulk density, cold crushing strength, oxidation resistance and thermal shock resistance of the refractories could be improved by the additions of ZrO2-SiC composite powder and industrial SiC powder, however, the apparent porosity was decreased. In this experimental condition, the refractories added with 6% ZrO2-SiC composite powder or industrial SiC powder had the best oxidation resistance and thermal shock resistance.(4) Fused corundum, natural graphite, zircon and carbon black were used as the starting materials for in-situ synthesis of the ZrO2-SiC composite in corundum and Al2O3-C refractories by carbothermal reduction reaction, and the effects of composition of the starting materials, forming pressure and heating temperature on the preparation and properties of the composite were studied. The results show that the Al2O3-ZrO2-SiC composite could be synthesized at 1530℃for 4h in argon gas by using fused corundum, zircon and carbon black as the starting materials. The bulk density of the Al2O3-ZrO2-SiC composite by the addition of 20% zircon and carbon black reached 2.58g/cm3. Moreover, when adding moderate zircon into the Al2O3-C refractories, the Al2O3-ZrO2-SiC-C composite could be synthesized at 1500℃for 4h by in-situ reaction. The bulk density and the mass loss ratio of the synthesized composite reached 2.73g/cm3 and 7.69%, respectively.(5) The effects of composition of the starting materials, heating temperature and holding time on the synthesis process of ZrN-Si3N4 composite powder were studied, and the synthesis mechanism was discussed. The results show that the carbothermal reduction reaction was more sufficient with the increasing of the carbon black content in sample, however, it had an optical value. Increasing the heating temperature and holding time could promote the decomposition of zircon and the formation of Si3N4 and ZrN, and the optimum synthesis condition was mass ratio of zircon and carbon black of 100/40, synthesizing temperature of 1500℃and holding time of 12h.(6) The predominant region diagram of Al2O3-ZrO2-SiO2-C-N2 system was plotted through the thermodynamic data of some reactions to analyze the effects of partial pressure of CO gas and temperature on the stability of phases. In addition, the effects of composition of the starting materials and heating temperature on the preparation process and properties of the ZrN-Sialon bonded corundum composite were studied, and the synthesis mechanism was discussed. The results show that increasing the heating temperature as well as zircon and carbon black content were in favor of the decomposition of zircon and the formation of Sialon and ZrN. In this experimental condition, the proper temperature to synthesize ZrN-Sialon bonded corundum composite was 1500℃.
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