高岭土原位碳热还原制备Al2O3/SiC复相陶瓷材料的研究

摘要

Fabricated Al2O3/SiC composites with the natural mineral of kaolin by in-situ carbothermal reduction and hot-press sintering is set out to elaborate. Kaolin is a natural mineral, and carbon is used as a main raw material. The main purpose is to explore a new synthesis method for the high-performance Al2O3/SiC composites at the relatively low cost. At the beginning, by in-situ carbothermal reduction, Al2O3/SiC composite powder was synthesized with kaolin and carbon in the atmosphere with flowing argon. The whole thermodynamic processes have been analyzed and investigated not only with theory but also with experimental measures. The synthesizing process of Al2O3/SiC composite powder was analyzed with DTA, XRD and SEM. It shows that the synthesizing process is involved in two stages. The first stage is the dehydration decomposition of kaolin itself. The second stage is SiO2 reduced by carbon. Thereupon, the Al2O3/SiC composite powder is produced. The study shows that the optimal synthesizing temperature for Al2O3/SiC composite powder is at 1550℃. Then the Al2O3/SiC composites were fabricated by hot-press technology from the synthesized Al2O3/SiC powder. The sintering additive was used to lower the sintering temperature. The whole processes were conducted in argon atmosphere. The results show that the bending strength of Al2O3/SiC composites attains 420 Mpa, and the relative density and hardness reach 98% and HRA89 respectively.%详细介绍了利用高岭土通过原位反应及热压烧结制备Al2O3/SiC复相陶瓷材料.探索了以天然矿物高岭土,碳作为原材料,低成本合成制备高性能Al2O3/SiC复相陶瓷的新方法.首先,在原位碳热还原反应中,高岭土和碳在流动氩气氛中合成制备Al2O3/SiC复相陶瓷粉,对合成反应的热力学过程进行理论分析和实验研究,对合成的Al2O3/SiC复相陶瓷粉进行了DTA和XRD分析,分析表明陶瓷粉的合成过程分两步,第一步是高岭土自身的脱水,第二步是SiO2被还原的过程及制备出Al2O3/SiC复相陶瓷粉.研究表明,最佳的粉末合成温度为1550℃;其次,Al2O3/SiC复相陶瓷粉通过热压烧结合成制备Al2O3/SiC复相陶瓷,烧结助剂的添加有助于降低烧结温度.复相陶瓷抗弯强度达到420 MPa,相对密度达到98%,硬度HRA89.