Reaction mechanism of self-propagating magnesiothermic reduction of ZrB2 powders

• Published in: Rare metals Vol. 32; no. 4; pp. 408 - 413
• Main Authors: Zheng, Yong-Ting, Li, Hong-Bo, Xu, Zhong-Hai, Zhao, Jing, Yang, Pan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2013; Science and Technology on Advanced Composites in Special Environments Laboratory, Harbin Institute of Technology,Harbin 150001, China%Materials Engineering Department, North China Institute of Aerospace Engineering, Langfang 065000, China
• Subjects: Biomaterials; Chemistry and Materials Science; Energy; Materials Engineering; Materials Science; Metallic Materials; Nanoscale Science and Technology; Physical Chemistry; 二硼化锆; 反应机理; 差热分析; 燃烧合成; 粉体; 自蔓延; 还原工艺; 镁热还原; Reaction mechanism; Zirconium boride; Self-propagating synthesis; Magnesiothermic reduction
• ISSN: 1001-0521; 1867-7185
• DOI: 10.1007/s12598-013-0069-2

Fine zirconium diboride （ZrB2） powders with high purity were successfully prepared by combustion synthesis through magnesiothermic reduction process in Mg-B2O3-ZrO2 system. The reaction mechanism was investigated by differential thermal analysis and quenching experiment. The results show that the whole magnesio-thermic reduction process includes three stages： first, molten B2O3 and Mg formed above the temperature of 650 ℃, and glassy B2O3 and solid ZrO2 particles were coated on the surface of the molten Mg; thus, the hollow balls can be formed when the molten Mg was exuded under capillary function. Second, ZrO2 particles reacted with molten Mg to form Zr and MgO with dissolution-precip-itation mechanism, which released a large amount of heat to induce the diffusion reaction between B203 and Mg to form B and MgO. Last, Zr reacted with B to form ZrB2 grains. The preparation of ZrB2 by self-propagating syn-thesis in Mg-B2O3-ZrO2 system is a solid-liquid-liquid reaction.