Abstract: To explore the effect of raw material pretreatment on their preparation,TiB₂ powders were prepared with TiO₂,B₄C and carbon black as starting materials by the microwave-assisted boron/carbon thermal reduction method,firing at 1 450 ℃ for 20 min.The effects of three raw material pretreatment methods (no pretreatment,ball milling,and ball milling-pressing pellets) on the phase composition and microscopic morphology of the powders were investigated.The results show that after ball milling raw materials for 6 h and firing at 1 450 ℃ for 20 min,the TiB₂ powder obtained has an ideal hexagonal sheet-like structure with an average particle size about 0.52 μm as well as residual C and O contents of 0.254 mass% and 0.556 mass%.No other impurity phases are detected in the product.When using the unpretreated raw materials,there is residual TiC in the reaction products,mainly because the large particle size difference between the raw materials and slow diffusion rate lead to incomplete reaction.After pretreating the raw materials by ball milling-pressing pellets,there are TiBO₃ and Ti₂O₃ residues in the reaction products,mainly because the dense pellets inhibit the CO escape during the reaction,and then the forward progress of the reaction.Combined with the changes in the phase and morphology of the products,it is inferred that the unreacted TiC and TiBO₃ are formed by the reaction of TiO₂ and B₄C.

Key words: TiB₂, boron thermal/carbon thermal reduction method, pretreatment, ball milling, pellet

摘要： 为探究原料预处理对制备TiB₂粉体的作用规律,以TiO₂、B₄C和炭黑作为反应原料,通过微波辅助硼热/碳热还原法在1 450 ℃保温20 min下制备TiB₂粉体,探讨三种不同的原料预处理方式(原料未经预处理、原料球磨和原料球磨-压制球团)对产物的物相组成和微观形貌的影响。结果表明:原料球磨6 h处理后,在1 450 ℃保温20 min下制备出的TiB₂粉体具有理想的六方片状结构,平均粒径约为0.52 μm,且残留C、O含量(w)分别为0.254%和 0.556%,产物中无其他杂相;原料未经预处理时,反应产物中有TiC残留,原因是原料间的粒径差距大,扩散速率缓慢,致使反应不完全;原料经球磨-压制球团处理后,反应产物中有TiBO₃、Ti₂O₃残留,主要是由于致密的球团抑制反应过程中CO逸出,进而抑制反应的正向进行,导致产物中有未反应物质残留。最后,结合产物的物相和形貌变化,推测未反应物质TiC和TiBO₃均由TiO₂和B₄C反应生成。

关键词: TiB₂, 硼热/碳热还原法, 预处理, 球磨, 球团