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采用循环伏安法和线性扫描法对模拟草酸钚沉淀母液中草酸和钚的电化学行为进行研究。研究结果表明,HNO3介质中的H2C2O4在Pt电极上的氧化为不可逆反应。在模拟的草酸钚沉淀母液中,因Pu(Ⅳ)被C2O2-4络合而未出现Pu(Ⅲ)/Pu(Ⅳ)的氧化还原峰,H2C2O4的氧化峰则清晰可见,H2C2O4的氧化反应仍为不可逆过程。对模拟草酸钚沉淀母液进行恒电流电解,考察了模拟母液中Pu(Ⅳ)初始浓度对草酸电解速率的影响以及电解过程中Pu价态的变化。结果表明,钚浓度为0.002~0.1g/L时,对H2C2O4的电解速率影响不大。恒电流密度下电解可将草酸钚沉淀母液中草酸的浓度破坏到0.001mol/L以下,可满足工艺要求。 相似文献
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以Pt-Ti(镀铂钛)为阳极,Ti为阴极,对HNO3介质中的H2C2O4进行恒电流电解,考察HNO3介质中H2C2O4电解动力学特性及其影响因素,并初步探讨HNO3介质中H2C2O4的电解氧化机理。研究结果表明:电流密度控制在25~37mA/cm2、HNO3浓度为2~3mol/L、温度为30~40℃时,电解效果最佳;微量金属离子(Fe3+、MnO-4、Ag+)的存在对H2C2O4的电解起催化作用,能较大提高电解速率;电解氧化法破坏H2C2O4的效率高于KMnO4蒸煮法,在工业中有潜在的应用前景。 相似文献
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氧化硼对铁磷酸盐玻璃陶瓷固化体的影响 总被引:1,自引:0,他引:1
研究了不同B2O3掺量对铁磷酸盐玻璃陶瓷高放废物固化体结构和性能的影响。应用溶出速率法(DR)对固化体进行了化学稳定性测试,使用傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)方法研究了样品的结构。研究结果表明:玻璃陶瓷固化体的主晶相为独居石;B2O3的引入对玻璃陶瓷固化体的化学稳定性影响较大,以10%(摩尔分数)的B2O3代替Fe2O3制得的固化体化学稳定性最佳,其28d的质量浸出率约为7.81×10-9g•cm-2•min-1;试样中存在大量正磷酸基团[PO4]3-和少量焦磷酸基团[P2O7]4-,无偏磷酸基团[PO3]-存在,固化体中的B主要以[BO4]四面体基团形式存在。 相似文献
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本工作研究U3O8粉末制备工艺流程和工艺参数,测试制备出的U3O8粉末的物化性能以及U3O8粉末添加对UO2芯块产品质量的影响。分析结果表明:所制备的U3O8粉末可加到UO2粉末中而被回收利用;控制U3O8粉末加入量,可调节UO2芯块的密度和微观组织,制备出合格的UO2芯块,从而提高了金属铀的直收率和利用率。 相似文献
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离子交换色谱中硼同位素交换反应平衡常数的理论预测 总被引:1,自引:0,他引:1
外部溶液相中B(OH)3与离子交换树脂相中B(OH)4-、B3O3(OH)52-、B3O3(OH)4-之间所发生的同位素交换反应的平衡常数K是离子交换色谱法分离硼同位素研究中的基本参数之一,但难以用实验手段精确测定。本研究利用密度泛函理论(DFT)在B3LYP/6—31G理论水平上计算了气态下B(OH)3、B(OH)4-等的振动频率,用计算得到的频率,基于Urey模型求得B(OH)3、B(OH)4-、B3O3(OH)52-、B3O3(OH)4-的简约配分函数比(RPFR),进而得到同位素交换反应平衡常数。结果表明,B(OH)3和B(OH)4-间的同位素效应显著,其平衡常数K在25 ℃时为1.025 7,B(OH)3与B3O3(OH)52-和B3O3(OH)4-反应的平衡常数较小,分别约为1.017 2和1.008 4。 相似文献
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以天然锆英石、模拟放射性焚烧灰、CaCO3、TiO2、UO2为原料,采用高温固相反应,对人造岩石固化掺铀模拟放射性焚烧灰进行研究。借助XRD、SEM、抗浸出性能测试等分析测试方法,研究固化体的性能。结果表明:在空气气氛下烧结,固化体的晶相为CaZrTi2O7[Ca(Zr,U)Ti2O7]、CaTiSiO5、CaTiO3和CaUO4,一部分U固溶于Ca(Zr,U)Ti2O7中;较多CaZrTi2O7的生成有利于Ca(Zr,U)Ti2O7固溶更多的U;模拟放射性焚烧灰掺量为60%、UO2含量为6.88%的人造岩石固化体,1~35d铀的归一化浸出率为0.17~2.81μg/(cm2•d),42~192d铀的归一化浸出率为0.09~0.13μg/(cm2•d)。 相似文献
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C-276合金在650℃/25MPa超临界水中的腐蚀行为 总被引:1,自引:1,他引:0
研究了HastelloyC-276(C-276)镍基合金在650℃/25MPa超临界水中的腐蚀特性。采用扫描电镜、X射线能谱仪、X射线衍射和X射线光电子能谱分析了氧化膜的腐蚀形貌、组织结构和合金元素分布。研究结果表明,C-276合金在650℃/25MPa的超临界水中的腐蚀过程主要是Ni的溶解,由于不能形成均匀、完整的氧化膜,合金在超临界水中并不具备优越的耐腐蚀性能,其双层结构的氧化膜富Cr而贫Ni、Mo,外层疏松的大颗粒(Ni(OH)2和NiO)为金属溶解和氧化物沉淀形成,内层(Cr2O3)的生长则是水穿过氧化物微孔作用的结果。 相似文献
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金属铀表面氧化动力学的X射线衍射研究 总被引:2,自引:0,他引:2
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46.0kJ/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。 相似文献
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AP1000与一般压水堆不同的是其一回路采用注锌加氢技术,使其一回路氧化膜特性发生变化。试验在高压釜中模拟AP1000一回路水化学工况,研究F304L、F316、690三种反应堆主工艺设备材料表面生成的氧化膜特性。结果表明,氧化膜为双层结构,外层氧化膜成分主要是Fe2O3及Fe3O4。F304L不锈钢与F316不锈钢内层氧化膜主要是ZnCr2O4,注入的Zn元素取代了FeCr2O4中的铁元素,形成了致密的ZnCr2O4 氧化层,内层氧化膜存在少量ZnO和ZnFe2O4。690合金的氧化膜内层为ZnCr2O4,同时存在较高含量的ZnO和ZnFe2O4。与前两者不同的是,690合金的氧化膜含少量的二价镍,以NiFe2O4和NiCr2O4形式存在。加锌加氢使得氧化膜更加致密,也明显变薄。 相似文献
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研究了奥氏体不锈钢304NG(以下简称304NG)在压力为25 MPa,温度分别为500、550、600、650℃超临界水中的腐蚀行为,通过扫描电镜-电子能谱(SEM-EDX)、X射线衍射(XRD)对304NG试样氧化膜微观组织的研究表明:304NG在超临界水中腐蚀后,表面氧化膜由岛状和非岛状2种不同形貌的腐蚀相组成.其中,含岛状腐蚀相的氧化膜具有双层结构,外层为Fe3O4相,内层为Fe3O4和FeCr2O4相;不含岛状腐蚀相的氧化膜为单层结构,氧化膜中含有Fe3O4和FeCr2O4相.同时,304NG在超临界水中氧化膜存在脱落现象,氧化膜脱落程度随温度升高而加剧. 相似文献
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Microstructural analysis and XPS investigation of nodular oxides formed on Zircaloy-4 总被引:2,自引:0,他引:2
In order to study nodular oxidation behavior under LOCA conditions, Zircaloy-4 cladding tubes were oxidized in high-temperature steam ambience and the growth evolution and microstructural properties of the oxides formed on the Zircaloy-4 surfaces were then investigated. Optical metallography showed different growth behaviors of uniform black oxide and localized whitish nodular oxide. The changes in composition and chemical states of the oxides formed on the Zircaloy-4 surface were investigated using X-ray photoelectron spectroscopy (XPS). Anion-deficient and non-stoichiometric ZrO was the main species in initial black uniform oxide surface, while stoichiometric ZrO2 was the main oxide species in the whitish nodular oxide. A stoichiometric composition in the nodular oxide resulted in a decrease in plasticity of the oxide layers. Unlike black uniform oxide, XPS spectrum from the nodular oxide showed clear Sn photopeak, which indicates that Sn species were observed in the nodular oxide only. As a result, it is concluded that the decreased plasticity and localized Sn additives may be the causes of nodular oxide initiation under LOCA conditions. 相似文献
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Low-pressure dielectric barrier discharge(DBD) TiCl4/O2and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy,and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15 o.Compared to titanium oxide films deposited in TiCl4/O2gas mixtures, those in TiCl4/O2/N2gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20 o, while that of undoped titanium oxide films is larger than 64 owhen they are measured after one week. The low-pressure TiCl4/O2plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film’s fragmentation due to the over-high film stress. Optical emission spectra(OES) of TiCl4/O2DBD plasmas at various power supply driving frequencies are presented. 相似文献
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This paper discusses the conversion of nitric oxide (NO) with a low-temperature plasma induced by a catalytic packed-bed dielectric barrier discharge (DBD) reactor.Alumina oxide (Al2O3),glass (SiO2) and zirconium oxide (ZrO2),three different spherical packed materials of the same size,were each present in the DBD reactor.The NO conversion under varying input voltage and specific energy density,and the effects of catalysts (titanium dioxide (TiO2) and manganese oxide (MnOx) coated on Al2O3) on NO conversion were investigated.The experimental results showed that NO conversion was greatly enhanced in the presence of packed materials in the reactor,and the catalytic packed bed of MnOx/Al2O3 showed better performance than that of TiO2/Al2O3.The surface and crystal structures of the materials and catalysts were characterized through scanning electron microscopy analysis.The final products were clearly observed by a Fourier transform infrared spectrometer and provided a better understanding of NO conversion. 相似文献
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《Journal of Nuclear Materials》2003,312(2-3):134-140
The hydrogen absorption and the permeation behavior through the oxide layer formed on modified Zircaloy-4 (Zry-4) alloys were investigated. The modified Zry-4 was prepared by altering the chemical composition of standard Zry-4. The tin content of Zry-4 (1.5 wt%) was reduced to 0.5 wt%, and alloying elements Si, O and Nb were added from 0.01 to 0.2 wt%. The oxide layers were grown in a static autoclave at 360 °C under 18.3 MPa for 150 days. Fick’s law was used to calculate the diffusivity of hydrogen after the steady state of the permeation flux was reached. The diffusivity of hydrogen in the 0.5Sn–0.1Nb–0.1Fe–0.2Cr–0.2O–Zr specimen was lower than that in the 1.5Sn–0.2Fe–0.1Cr–0.1O–0.01Si–Zr and Zry-4 specimens. As the area fraction of precipitates increased, the hydrogen diffusivity increased whereas an inverse relationship between the diffusivity and the amount of the tetragonal phase was observed. In addition to the oxide structural study, the effects of the microstructure of the zirconium alloys such as precipitates and grain boundaries on the hydrogen absorption were studied. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(2):225-232
Recent studies on stress corrosion cracking (SCC) behaviors of austenitic stainless steels in hydrogenated high-temperature water show that low potential SCC (LPSCC) can occur on cold-worked SUS 316 stainless steel (hereinafter, 316SS). In this study, oxide films and crack tips on cold-worked 316SS exposed to hydrogenated high-temperature water were characterized using analytical transmission electron microscopy (ATEM), grazing incidence X-ray diffraction (GIXRD) and Auger electron spectroscopy (AES) in order to study the corrosion and SCC behaviors of these films and crack tips. A double layer structure was identified for the oxide film after a constant extension rate tensile (CERT) test. The outer layer was composed of large particles (0.2–3 μm) of Fe3O4 and the inner layer consisted mainly of fine particles (~10 nm) of FeCr2O4. In addition, nickel enrichment was identified at the metal/oxide interface. Particles of Fe3O4 were also identified on the crack walls. These results indicate that the same electrochemical reactions had occurred inside and outside the crack. The crack tip area was filled with corrosion products of a chromium-rich oxide. In addition, nickel enrichment was observed at the crack tip. The formation of the nickel-enriched phase indicates that a selective dissolution reaction of iron and chromium occurred at the front of the LPSCC crack. 相似文献