纳米TiO_2的结构相变和锐钛矿晶粒长大动力学

Structural Transformation of Nano-structure Titania Powders and the Growth Kinetics of Anatase Crystallites

本文用溶胶-凝胶法制备了 TiO_2 纳米粉末,并研究了该粉末的热稳定性.结果表明,当热处理温度<500℃时,粉末粒度增长缦慢,而当温度>500℃时粉末粒度迅速长大.我们应用相变理论计算了锐钛矿晶粒的两阶段长大激活能,结果发现,在>500℃锐钛矿晶粒的长大激活能(90.3kJ/mol)比<500℃相应的值(15.6kJ/mol)高出几倍.XRD 物相分析表明,经550℃热处理后,粉末样品中已经发生了部分锐钛矿→金红石结构相变,这个相变过程严重地影响着锐钛矿晶粒的长大行为.与传统的 TiO_2 材料相比,TiO_2 纳米粉末样品中锐钛矿→金红石的相变温度降低很多,而且这一相变过程在较宽的温度范围内完成.

The thermal stability of titania powders prepared by a Sol-gel method was investigated.Itwas found that the grain size or the particle size of the powders increased slowly with annealingtemperature up to 500℃,but grew rapidly when the annealing temperature was higher than500℃.The activation energies for growth of anatase crystallites in the two temperatureregions were calculated to be 15.6kJ/mol and 90.3kJ/mol respectively.The X-ray diffractionresults suggest that the transformation from anatase phase to rutile phase in the nanometertitania powder starts at 550℃,a temperature much lower than that of the transformationfor conventional titania materials,and can be completed in a wider temperature range up to800℃.This would affect significantly the growth behavior of the anatase crystallite.