TiB2-TiC复合粉的自蔓延高温还原合成

热分析结果表明,对于B₂O₃-TiO₂-Mg-C体系,可利用SHS还原技术合成出TiB₂-TiC陶瓷复合粉。其化学反应机理为:Mg先还原B₂O₃和TiO₂,新生的Ti与B和C反应生成TiB₂和TiC; TiO₂的还原经历了TiO₂→TiO→Ti的逐步过程。采用一定的酸洗工艺得到了纯净的TiB₂-TiC陶瓷复合粉。复合粉中包含六方片状TiB₂和圆球状TiC;复合粉中1μm以下颗粒质量百分数超过45%,87%以上的颗粒大小在3μm以下。在TiB₂-TiC中,TiC_<em>y以一种贫碳结构存在,物料中Ti被B或C结合形成TiB₂和TiC_<em>y,y的值为0.7483。

SYNTHESIS OF TiB2-TiC COMPOSITE POWDER BY SHS REDUCTION PROCESS

The mechanism of chemical reaction and microstructure formation process of B2O3-TiO2-Mg-C system were investigated in this paper. The results showed that TiB2-TiC ceramic powder could be obtained by SHS from B2O3-TiO2-Mg-C system. The results of analysis of different thermal analysis (DTA) and X-ray diffraction (XRD) showed the following thermal processes of B2O3-TiO2-Mg-C system: B2O3 was reduced to B and TiO2 was reduced to Ti. Metal Mg was melted at 650℃. At 680 ℃ the reaction between B and Ti nearly finished and the formation of TiC from the reaction of Ti and C began. TiO2 was reduced to element Ti step by step through the following way: TiO2→TiO→Ti. TiB2-TiC composite powder with particle size of 45 percent under 1μm and 87 percent under 3μm was obtained after MgO, the unwanted phase, was removed by leaching in hydrochloric acid. Results of SEM micrographs of TiB2-TiC ceramic multiphase powder showed that the particle size is much smaller than that of single phase TiB2 or TiC produced by the same methods. The mole ratio of Ti and C in TiC was 1∶0.7483.