Dynamics Study on Surface Oxidization of Uranium by X-ray Diffraction
-
摘要: 利用X射线衍射和Rietveld方法研究室温～150 ℃和300 ℃下金属铀表面氧化，对氧化过程中试样的表面结构以及氧化动力学进行分析。将试样表面氧化物随时间的变化作定量计算，绘制出不同温度下金属铀表面的氧化动力学曲线，对50～150 ℃范围内的氧化动力学数据进行拟合，获得不同温度下的氧化反应速率常数，由此得到大气环境下金属铀表面形成UO2的活化能为46.0 kJ/mol。在300 ℃下，氧化产物U3O8逐渐在UO2上形成，其形成过程符合成核生长机理。
-
关键词:
- 金属铀 ,
- 动力学 ,
- X射线衍射 ,
- Rietveld方法
Abstract: he oxidation of uranium metal was studied by X-ray diffraction(XRD) and Rietveld method in the range of 25-150 ℃ and at 300 ℃, respectively. The processes of oxidation to UO2 and U3O8 were analyzed by XRD in order to observe the extent of surface oxidation and the oxide structure. The dynamics expression for the formation of UO2 in the temperature range of 25-150 ℃ was initially nonlinear, but switched to linear at long reaction time, that is, there exist two stages in the UO2 growth kinetics: nonlinear portion and linear portion. Using the kinetic data of linear portion the activation energy of oxidation is obtained to be about 46.0 kJ/mol. The U3O8 forms gradually on UO2 layer at 300 ℃, which accords with the nucleation-and-growth kinetics mechanism.-
Keywords:
- uranium ,
- oxidation kinetics ,
- X-ray diffraction ,
- Rietveld method
-
-
[1] HAYWARD P J, EVANS D G, TAYLOR P, et al. Oxidation of uranium in argon 25% oxygen at 190-610 ℃[J]. J Nucl Mater, 1992, 187:215-222. [2] HAYWARD P J, EVANS D G, TOYLOR P, et al. Oxidation of uranium in steam[J]. J Nucl Mater, 1994, 217:82-92. [3] McGILLIVRAY G W, GEESON D A, GREENWOOD R C. Studies of the kinetics and mechanism of the oxidation of uranium by dry and moist air: A model for determining the oxidation rate over a wide range of temperatures and water vapour pressures[J]. J Nucl Mater, 1994, 208:81-97. [4] 张延志，汪小琳，管卫军，等.大气环境中铀表面结构XRD研究[J]. 原子能科学技术，2003, 37(4):353-357.
ZHANG Yanzhi, WANG Xiaolin, GUAN Weijun, et al. Study on surface of structure of uranium under atmosphere using X-ray diffraction[J]. Atomic Energy Science and Technology,2003,37(4):353-357(in Chinese).[5] McEACHERN R J, CHOI J W, KoláｒM, et al. Determination of the activation energy for the formation of U3O8 on UO2[J]. J Nucl Mater, 1997, 249:58-69.
计量
- 文章访问数: 1064
- HTML全文浏览量: 0
- PDF下载量: 1590
下载:
