掺钛对UO_2微球晶粒生长机制的影响

Investigation of Affecting Mechanism of Doped Titanium on the Grain Growth of UO_2 Microspheres

采用溶胶-凝胶方法制备掺钛0.3%(质量分数,下同)UO2微球,用金相显微镜观察微球微观结构、图像分析仪计算微球晶粒尺寸。对掺钛0.3%UO2微球晶粒长大机制进行了研究。经过计算得到在1 250～1 550℃之间掺钛UO2微球晶粒生长的平均活化能Ea=232.79kJ/mol,明显地低于UO2微球晶粒生长的平均活化能(Ea0=518.32kJ/mol);掺钛UO2微球在烧结后期(1 250℃之后),微球部分区域可能形成高价态的U4O9相,加快了U原子扩散速度,加速了晶粒生长。

The preparation of UOz microspheres with w（Ti）= 0.3% doped titanium by sel-gol method, its microstructure and the grain size by means of the optical microscope and the image analyzer are studied respectively. In addition, we carried out a research on the mechanism of grain growth of UOz microspheres doped with w（Ti）=0. 3%. Based on the calculation, it is obtained that, at the temperature of 1 250 ℃ to 1 550 ℃, the average activa- tion energy of the grain growth of Ti-doped UO2 microspheres, Ea is 232.79 kJ/mol, which is significantly lower than the average grain growth activation energy （E,0-= 518.32 kJ/mol）. In the late sintering period of Ti-doped UOz microspheres（after 1 250 ℃）, there may form U409 in some parts of the microspheres, accelerating U-atom diffusion rate and the grain growth.