铀铌合金表面热氧化膜结构研究

采用X射线光电谱分析技术、结合Ar离子枪溅射,研究了大气环境、不同温度(室温、100、200和300℃)条件下铀铌合金样品表面氧化膜结构的变化情况。实验结果表明:随温度升高,氧化膜厚度增大,氧化膜结构发生明显变化。不同温度热氧化处理后,铀铌合金初始表面Nb主要以Nb2O5形式存在,在Nb2O5与金属Nb之间,总存在一定厚度的NbO及少量其他价态氧化物NbOx(0x1,1x2)的混合层。室温～200℃热氧化合金样品表面铀均以含间隙氧的UO2+x(P型)存在,其U4f7/2结合能较UO2低约0.7eV。室温条件下,氧化膜成分主要为UO2;100、200℃热氧化后,氧化膜中除UO2外,还含有少量P型UO2+x,其U4f5/2卫星峰的结合能为396.6eV。300℃热氧化后的合金样品表面为铀的高价氧化物(U3O8或UOx,2x3),U4f特征峰的结合能分别为381.8和392.2eV;氧化层为UO2和金属铀的混合物。热氧化过程中,温度对铀氧化的影响较对Nb的明显得多。

Study on Thermo-Oxide Layers of Uranium-Niobium Alloy

Surface oxides structure of uranium niobium alloys which were annealed under different temperatures (room temperature, 100, 200, 300 ℃, respectively) in air were studied by X-ray photoelectron spectroscopy (XPS) analysis and depth profile. Thickness of thermo-oxide layers enhance with the increasing oxide temperature, and obvious changes to oxides structure are observed. Under different delt temperatures, Nb₂O₅ are detected on the initial surface of U-Nb alloys, and a layer of NbO mixed with some NbO_x(02O₅ and Nb metal. Dealing samples in air from room temperature to 200 ℃, non-stoichiometric UO_2+x(UO₂ + interstitial oxygen, P-type semiconductor) are found on initial surface of U-Nb alloys, which has 0.7 eV shift to lower binding energy of U 4f_7/2 characteristics comparing to that of UO₂. Under room temperature, UO₂ are commonly detected in the oxides-layer,while under temperature of 100 and 200 ℃, some P-type UO_2+x are found in the oxide layers, which has a satellite at binding energy of 396.6 eV. When annealing at 300 ℃, higher valence oxides, such as U₃O₈ or UO_x (25/2 and U 4f_7/2 peaks are 392.2 and 381.8 eV, respectively. UO₂ mixed uranium metal are the main compositions in the oxide layers. From the results, influence of temperature to oxidation of uranium is more visible than to niobium in uranium-niobium alloys.