熔盐中镁热还原合成二硼化钛纳米粉体

Synthesis of TiB_2 Nanopowder by Magnesiothermic Reduction in Molten Salt

以二氧化钛、硼粉、三氧化二硼、钛粉为原料,金属镁粉为还原剂,在NaCl KCl熔盐中利用镁热还原法合成了TiB2纳米粉体.研究了TiO2-Mg-B和B2O3-Mg-Ti体系在熔盐中合成TiB2粉体的反应过程及机理,分析了两体系中合成TiB2的起始温度、最佳温度、形貌和尺寸的差异,对粉体的物相组成及显微结构进行了表征.结果表明：2个体系合成TiB2的起始温度均为800℃,TiB2的结晶性及纯度随温度升高而提高,最佳合成温度均为1 000℃.经1 000℃保温4h后,TiO2 Mg B体系合成的TiB2粉体形貌不规则,颗粒尺寸约为30～100 nm;而在相同条件下,采用B2O3-Mg-Ti体系合成的立方形态的TiB2粉体颗粒尺寸约为40～200 nm.B2O3在NaCl KCl熔盐中的溶解度较TiO2高,更易被金属Mg还原,因此,B2O3-Mg-Ti体系合成的TiB2结晶性优于TiO2-Mg-B体系.

Titanium boride nanopowder was synthesized via magnesiothermic reduction in NaCl-KCl molten salt with titanium dioxide,boron,boron trioxide,titanium and magnesium as starting materials.The synthesis mechanism of TiB2 powder from molten salt for TiO2 Mg-B system and B2O3-Mg-Ti system was investigated.The starting synthesis temperature,the optimal synthesis temperature,the morphology and size of TiB2 powder for the two systems were analyzed.The phase constitution and microstructure of TiB2 powders were discussed.The results show that TiB2 can be formed at 800 ℃,and the optimal synthesis temperature is 1 000 ℃ for the both systems.The TiB2 synthesized in TiO2-Mg-system and heated at 1 000 ℃ for 4 h shows an irregular morphology in a particle size range of 30 100 nm.The cubic TiB2 powder in a particle size range of 40 200 nm can be obtained in the B2O3 Mg Ti system under the same heating condition.TiO2has a poor solubility in NaCl KCl molten salt,and the solubility of B2 O3 is greater.Since B2O3 can be reduced more easily rather thanTiO2,TiB2 synthesized in B2O3-Mg-Ti system has a better crystallinity.