水解法制备的掺铁二氧化钛超微粉的热分析、晶粒生长和结构相变

The Thermal Analysis, Crystal Growth and Structure Transformation of Nano-scale TiO2 Prepared by TiCl4 Hydrolysis

研究了用四氯化钛水解制备的纯二氧化钛和分步沉淀，共沉淀方式制备的掺铁二氧化钛的热分解状况，晶化过程。采用Ｘ射线衍射和Ｖｏｉｇｔ单峰分析法计算了这三种样品在各个煅烧温度下的晶体晶粒度。结果表明，四氯化钛水解方法得到的二氧化钛粉为无定形，无定形二氧化钛加热晶化过程是一个持续的过程，并没有以往文献中所报道的明显的晶化温度和晶化放热峰。应用非晶物质晶化晶核生长速率方程计算了晶粒生长活化能并且进行了讨论。

Nano-scaled pure and iron doping Titanium Dioxide prepared by TiCl4 hydrolysis were obtained. Two methods, step precipitation and co-precipitation, were applied in preparing the iron doping samples. The crystallization and decomposition processes were extensively investigated by methods of X-ray diffraction and TEM. The grain sizes under series of calcinating temperatures were computed according to Voigt function analysis. The results of TEM images also justified the computed grain size. The results showed that Titanium Dioxide prepared by TiCl4 hydrolysis is amorphous, and that no obvious crystallization temperature or exothermic peaks were observed, contrary to the some previous reports. The computation applying the nuclei growth equation showed that the crystal grain growth of the pure and co-precipitation samples can be divided into 2 steps. The growth activation energy of the former step is 10. 7kJ mol-1 and 8. 6kJ mol- 1, respectively and that of the latter step is 111. 6kJ. mol - 1. As to the step precipitation samples, there showed no obvious difference in crystal growth activation energies for the 2 steps, and for the transformation of anantase to rutile was almost completed before 600. There was evidence that the iron doping accelerated the transformation of rutile to anatase and this is especially obvious in step precipitation samples.