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Using ternary molten salt with a molar ratio of NaCl:KCl:CsCl = 30:24.5:45.5 and ZrCl4 as raw materials to prepare a NaCl-KCl-CsCl-Cs2ZrCl6 composite electrolyte. Characterizing by XRD, ICP-AES, optical microscopy and SEM-EDS, the results showed that when the molar ratio of CsCl:ZrCl4 ≥ 2:1, Cs2ZrCl6 was generated according to the stoichiometric reaction; when the molar ratio of CsCl:ZrCl4 < 2:1, CsCl in molten salt was almost completely converted to Cs2ZrCl6, and there was a ZrCl4 phase. When the molar ratio of CsCl:ZrCl4 = 2:1, with the increase of the reaction temperature and reaction time, the concentration of zirconium ions first increased and then decreased. The optimized preparation process conditions are: the 2:1 molar ratio of CsCl to ZrCl4 in NaCl-KCl-CsCl, 500 °C of reaction temperature of and 3 h of reaction time. Under this condition, 99.68% conversion rate from ZrCl4 to Cs2ZrCl6 was obtained. Taking the prepared NaCl-KCl-CsCl-Cs2ZrCl6 composite electrolyte as a raw material, a preliminary study of molten salt electrolytic refining zirconium was carried out, and a refined zirconium product with a dendrite of 10.61 mm was obtained under the conditions of a zirconium ions concentration of 5%, an electrolysis temperature of 750 °C, a current density of 0.1 A/cm2, and an electrolysis time of 9 h, indicating that the composite electrolyte can be used for the electrolytic refining of zirconium. [ABSTRACT FROM AUTHOR]

Nitride film as a hydrogen permeation barrier on zirconium hydride has seldom been studied. In this work, the zirconium nitride films were prepared on zirconium hydride in an atmosphere of N2 and N2 + H2 at 500~800 °C, with a holding time of 5 h and 20 h, and the mechanisms of film growth and hydrogen permeation were analyzed. The results showed that the film growth was mostly influenced by the temperature, followed by the reaction atmosphere and the holding time. The hydrogen could increase the nitrogen diffusivity during the formation of zirconium nitride films. The in situ nitriding conditions were optimized as 800 °C, N2 + H2 atmosphere, and 5~20 h. The chemical composition of ZrN-based films was mainly comprised of Zr and N, with a minor content of O. In addition, the film exhibited a major phase of ZrN, accompanied by the coexistence of ZrO2, ZrO, ZrN(NH2), and ZrN0.36H0.8, as well as O-H and N-H bonds based on the XPS analysis. The as-prepared ZrN base films in the present study exhibited superior hydrogen permeation resistance to other ZrO2 films previously reported. The hydrogen permeation resistance of the films could be attributed to the following mechanisms, including the chemical capture of hydrogen by the above-mentioned compounds and bonds; the physical barrier of continuous and dense film incurred from the volume effect of different compounds based on Pilling–Bedworth model and the different nitrogen diffusion coefficients at different temperatures. [ABSTRACT FROM AUTHOR]

Summary: A prediction model for hydrogen loss rate (HLR) of coating zirconium hydride at 873 K based on Wagner's model was established using gas chromatograph. A continuous and dense coating of zirconium hydride with bilayer structure was prepared by phosphation‐oxidation method. The oxidation weight gain of coating zirconium hydride specimens at 873 K in a mixture atmosphere of CO2 and He was investigated. The oxidation weight gain law was obtained by fitting Wagner's model, and the release equation of CO were further deduced. The concentration of H2 and CO in the gas phase was measured by gas chromatograph in the closed system under the same conditions. The optimized HLR of coating zirconium hydride was obtained by deducting the amount of CO generated by the reaction of zirconium and CO2 using the release equation of CO. Fitted by Wagner's model, the dependence between optimized HLR and reaction time was obtained, and the loss amount of hydrogen at any moment can be calculated by extrapolated and integrated, thus a prediction model was established. Based on the model, the HLR of coating zirconium hydride is 0.97% in 1 year. Highlights: A prediction model for hydrogen loss rate of coating ZrHx at 873 K was established using gas chromatograph.A continuous and dense coating of ZrHx with bilayer structure was prepared by phosphation‐oxidation method.Fitted by Wagner's model, the equation of hydrogen permeability rate was obtained.The prediction model was further optimized by deducting the amount of CO produced by the reaction of Zr in CO2. [ABSTRACT FROM AUTHOR]