纳米TiO_2晶型转化机制探讨

Research on changing mechanism of Nano-TiO_2' s crystal structure

根据统计物理学方法推导出锐钛矿型TiO_2向金红石型TiO_2转化率关系式为InX_A=-v_0texp(-2U_x/kT),其中X_A为TiO_2中锐钛矿型的含量,v_0和U_x分别锐钛矿型TiO_2原子的振动频率和势函数,t、k和T分别为煅烧时间、玻兹曼常数和煅烧温度.TiO_2为三原子分子,理论上v_0和U_x计算十分复杂,本文通过在不同温度及时间下煅烧氨水水解TiOSO_4产物的方式制备了锐钛矿型、混晶型及金红石型纳米TiO_2粉末,将XRD分析所测数据及相应温度、时间条件代入转化率关系式,拟合求得:v_0=5.3×10^(10)/s,U_x=2.71×10^(-12)J.实验所测_A-t及X_A-T曲线与计算拟合曲线吻合较好,说明用氨水水解TiOSO_4产物的方式制备的锐钛矿型纳米TiO_2向金红石型纳米TiO_2的转化为扩散型转变.

Based on the method of statistical physics , the relation equation lnXA-^- rot exp（-2Uz/kT） for the change of anatase TiO2 into rutile TiO2 is established, where XA is the contents of anatase in the sample, v0 and Uz are, respectively, the vibration frequency and potential function of an anatase atom, t, k and T are calcination time, t3oltzmann constant and calcination temperature, respectively. Because TiO2 is a molecule with three atoms, it is very difficulty to calculate its v0 and Uz theoretically. In this article, the nanometer TiO2 powder with different proportion of anatase was got by calcining the hydrolysising products of the TiOSO4 solution under different calcination temperatures or times. The values of v0 and Uz（v0 =5.3 × 10^10/s,Uz=-2.71×10^-12J） were obtained by using the XRD data and corresponding temperature and time. The calculation curves of XA-T and XA-t are in agreement with the experimental results. It shows that the change mechanism from anatase TiO2 to rutile TiO2 is the diffuse one.