非水解溶胶-凝胶碳热还原氮化合成TiN粉体的形成过程

Synthesis mechanism of TiN powders via carbothermal reduction and nitridation process based on nonhydrolytic sol-gel method

以四氯化钛和异丙醚为主要原料，二氯甲烷为溶剂，采用非水解溶胶-凝胶法制备的TiO2凝胶为钛源，按n（C）：n（Ti）为11．4引入相对分子质量为1300000的聚乙烯吡咯烷酮（PVP）作为碳源，采用碳热还原氮化法合成TiN粉体。通过TG—DTA、XRD和FE-SEM研究了碳热还原氮化过程中TiN粉体的形成历程。结果发现，在800—1000℃碳热还原3h，锐钛矿型TiO2转变为金红石型TiO2；在1000-1200℃碳热还原氮化3h，金红石型TiO2转变为Ti3O5，并逐渐氮化生成TiOxNy；在1300℃碳热还原氮化3h，TiOxNy开始转变为TiN，但其氮化并不完全，延长氮化时间至5h，剩余的TiOxNy全部转化为TiN。TEM和纳米粒度分析仪测试表明，合成的TiN颗粒发育良好，呈近似方形结构，约为250nm，粒径分布在0．4-1.1μm。

TiQ gel was prepared by non-hydrolytic sol-gel method using titanium tetrachloride and isopro- pyl ether as raw materials, and dichloromethane as solvent. TiN powders were synthesized by carbothermal reduction and nitridation of TiO2 gel as titanium source and polyvinylpyrrolidone （PVP, molecular weight 1300 000） as carbon source based on il. 4 of n（C）： n（Ti）. The synthesis mechanism of TiN powders was investigated by TG-DTA, XRD and FE-SEM during carbothermal reduction and nitridation. The result shows that anatase TiO2 transforms to rutile TiO2 during carbothermal reduction and nitridation at 800 - 1 000℃ for 3 h;rutile TiO2 transforms to Ti3O5 ,then to TiOxNy gradually during carbothermal reduction and nitridation at 1 000 - 1 200℃ for 3 h;TiN appears gradually during carbothermal reduction and nitridation at 1 300℃ for 3 h, and the nitridation is not complete, but TiOxNy is converted completely to TiN when the nitridation time is lengthened to 5 h. The results of TEM micrographs and nano particle size distribution show that TiN crystals of approximate square structure are synthesized well with about 250 nm of dimensions, and the particle size is between 0.4 and 1.1μm.