热处理对爆轰合成的纳米TiO_2混晶的结构相变的影响

采用爆轰法制备了纳米TiO2混晶体,初步研究了不同煅烧温度(600℃和720℃)和不同煅烧时间(1 h,2 h,3.5 h和5 h)对其微结构和结构相变行为的影响,并应用热动力学理论讨论了从锐钛矿相到金红石相的结构相变过程和相变机理.研究表明:随着煅烧温度的升高和煅烧时间的增加,纳米TiO2的粒径逐渐增大,混晶中金红石相的含量逐渐提高.与常规方法制备的纳米TiO2不同的是,在相同煅烧温度和煅烧时间下金红石相的平均生长速率明显低于锐钛矿相.锐钛矿相完全相变为金红石的温度也明显低于常规方法报道的相变温度.该研究会对控制纳米TiO2晶体尺寸和批量合成提供一定的理论和实验指导.

Effect of thermal treatment on the structural phase transformation of the detonation-prepared TiO2 mixed crystal nanoparticles

Nanopaticles of TiO₂ mixed crystals (anatase phase and rutile phase) are prepared by detonation method. Morphologies and structural phase transformation behaviors of the as-prepared TiO₂ nanopaticles are investigated for different annealing temperatures (600 ℃ and 720 ℃) and durations of annealing time (1, 2, 3.5, and 5 h). The structural phase transformation process and transformation mechanism are also discussed within the framework of the thermodynamic theory. Results show that with the increase of the annealing temperature and annealing time, the particle size of the detonation-prepared TiO₂ nanoparticles increases gradually and the relative content of rutile phase in the TiO₂ mixed crystal nanopaticles is improved. Compared with the TiO₂ nanoparticles prepared by the conventional methods, the mean growth rate of rutile phase is obviously slower than that of anatase phase at the same annealing temperature and annealing time. It is obvious that the temperature at which the anatase phase completely changes into the rutile phase is lower than that of the TiO₂ nanoparticles prepared by using other methods. These results are helpful for realizing the control of particle size and phase transformation of TiO₂ nanoparticles. Meanwhile, the results can also provide us the theoretical and experimental bases for mass production of TiO₂ nanoparticles in the future.