B_2O_3-TiO_2-Mg-C体系燃烧反应热力学与产物结构变化过程研究

STUDY ON THERMODYNAMICS AND STRUCTURE CHANGE PROCESS IN COMBUSTION REACTION OF B_2O_3-TiO_2-Mg-C SYSTEM

对B2 O3-TiO2 -Mg -C体系的燃烧反应热力学进行了研究 ,结果表明 ,该体系化学反应机理为 :Mg先还原B2 O3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 Ti3O5TiOTi2 OTi的逐步过程 .对燃烧合成的产物结构形成机理进行了研究 ,表明当燃烧区的能量传到预反应区时 ,B2 O3首先熔化并均匀地包裹在Mg ,TiO2 和C周围 ,Mg熔化后通过扩散与B2 O3和TiO2 反应 ,随着预反应区温度的升高 ,B2 O3与Mg作用还原出B ,TiO2 与Mg作用还原出Ti,然后Ti与B或C反应形成TiB2 或TiC晶核 ,最后TiB2

The mechanisms of chemical reaction and microstructure formation process in combustion reaction of B 2O 3-TiO 2-Mg-C system were studied. The chemical reaction mechanism was proved as following: the exothermal reactions were happened between Mg-B 2O 3, Mg-TiO 2, and Ti-B at about 620 ℃. In this process, B 2O 3 was reduced to B and TiO 2 was reduced to Ti. Metal Mg was melted and transferred into liquid phase at 650 ℃. At 680 ℃ the reaction between B and Ti was nearly finished and the formation of TiC from the reaction of Ti and C began. TiO 2 was reduced to element Ti step by step through the following way: TiO 2Ti 3O 5 TiOTi 2OTi. Results of SEM micrographs show that B 2O 3 is reduced to B through Mg diffusing in molten B 2O 3 and TiO 2 is reduced to Ti between TiO 2 and Mg. Then, TiB 2 crystal nucleus is formed through the reaction of Ti and B and TiC crystal nucleus is formed through the reaction of Ti and C. Under the high temperature, the TiB 2 and TiC crystal nuclei grown.