超临界二氧化碳处理对铀抗大气腐蚀性能的影响

Influence of Supercritical Carbon Dioxide Treatment on Corrosion Resistance of Uranium in Air

通过对经超临界二氧化碳 (SuperCriticalCarbonDoxide ,SCCO2 )处理的铀样品在 60℃和 70 %相对湿度大气环境中腐蚀增重速度进行测量 ,研究了SCCO2 处理对铀样品抗大气腐蚀性能的影响 ,借助俄歇电子能谱和X射线衍射等表面分析方法 ,对经过SCCO2 处理的铀样品在表面的结构和化学成分进行了分析。实验数据表明 ,在 10MPa、60℃的SCCO2 中浸泡处理 3.0h和 4 .5h后 ,铀样品的抗大气腐蚀速度都较未经过SCCO2 处理的样品有明显的减慢。SCCO2 压力参数影响的实验结果显示 :同样条件下 (60℃ ,3h) ,10MPaSCCO2 处理的样品的抗大气腐蚀性能比 8MPa及 15MPa压力处理的要好 ;相同压力及时间条件下 (10MPa、3h) ,60℃处理的样品的抗腐蚀性能优于 5 0℃处理的。在所有实验中 ,10MPa、60℃的SCCO2 处理 3h后再于 2MPa的CO2 中浸泡 10 8h ,样品的抗腐蚀性能最好。AES分析结果显示 ,经SCCO2 处理后 ,铀表层C、O含量比未处理样品高 ,表明处理过程中有C和O的引入 ;XRD分析发现 ,铀表面与SCCO2 之间的化学反应在表层主要的产物是UO2 。

Corrosion resistance of uranium specimens treated by supercritical carbon dioxide (SCCO-2) was investigated in the atmosphere of 70% relative humidity at 60 ℃. The surface structure and chemical composition of uranium being treated was studied using auger electron spectrum (AES) and x-ray diffraction (XRD) method. Results showed that the corrosion of specimens treated by SCCO-2 of 10 MPa and 60 ℃ for 3 hours or 4.5 hours were both slower than the specimens without treatment. The pressure influence experiments revealed that the SCCO-2 of 10 MPa had a better effect than the SCCO-2 of 8 MPa or 15 MPa in improving the corrosion resistance of uranium at the same pressure (10 MPa) and the same time (3 hours). As to the temperature, the experimental results indicated that 60 ℃ was better than 50 ℃ at the pressure of 10 MPa for 3 hours. Among all experiments, the best corrosion-resistance was obtained under 10 MPa SCCO-2, 60 ℃ for 3 hours and an additional 2 MPa CO-2 dipping for 108 hours. AES results showed that O and C had been introduced to the surface layer. XRD indicated the major reaction product of uranium and SCCO-2 was UO-2. The mechanism of corrosion resistance improvement was proposed too.