Sol-gel自蔓燃法控制合成二氧化钛纳米粉体及性能

采用化学络合溶胶-凝胶法,结合自蔓燃合成工艺制备了结构可控、分散性良好的TiO2纳米粉体.考察了原料组成、凝胶膨胀程度和温度机制对粉体结构、分散性的影响,用漫反射光谱测试了所制备粉体的光吸收性能. 结果表明,将原料中氧化剂与还原剂的摩尔比从2增加到7,在600 ℃的煅烧温度下可以得到金红石含量在25％～68.2％之间的TiO2,这些结构不同的粉体粒度为30 nm左右;凝胶前驱体经过150 ℃充分膨胀炭化,能有效阻止胶粒间氢键的形成,并且能够防止因毛细管作用而导致的凝胶网络坍塌,从而得到单分散无团聚粉体;提高煅烧温度,金红石含量增多、颗粒粒度增大,800 ℃时出现团聚体;用该工艺制备的粉体的光吸收范围发生明显红移,与市售金红石型TiO2相比,反光率下降10％以上;金红石含量为55.5％的混晶型粉体显示出最好的光吸收性能.

Controlled Synthesis of TiO2 Nanometer Powders by Sol-gel Auto-igniting Process and Their Structural Property

Highly dispersed TiO2 nanometer powders with controlled structure were synthesized by chemical complex sol-gel auto-igniting process. The initial oxidant/reductant molar ratio, swelling of gel and temperature schedule were chosen as key variables for the controlled synthesis: by changing the initial oxidant/reductant molar ratio from 2 to 7, TiO2 having a particle size about 30 nm was obtained at 600 ℃ with a mass fraction of rutile ranging from 25％ to 68.2％; sufficient swelling and carbonizing of the gels at 150 ℃ removed non-bridging hydroxyl groups and broke down the hydrogen bonds between particles, so the formation of hard agglomerates was avoided; the mass fraction of rutile and particle size of TiO2 increased with increasing of calcination temperature; agglomerates of TiO2 were formed at 800 ℃. The optical absorption edges significantly shifted to longer wavelengths in the UV-Vis diffuse reflectance spectra of the as-prepared TiO2, and the reflectivity was about 10％ lower than that of commercial TiO2. It was found that the as-prepared TiO2 with the optimal rutile fraction of 55.5％ achieved the best optical absorption.