| Fusion has been considered as a kind of safe and clean energy source with abundant sources of fuel. The International Thermonuclear Experimental Reactor (ITER) is a major international science and technology cooperation project, and it is aimed at carrying out research on controllable magnetic confinement nuclear fusion technology. ZrCo alloy has demonstrated its unique advantages in the field of tritium storage, and it was identified as an important candidate materials for deuterium/tritium storage, supply and recycling in fuel cycle system project of ITER in recent years. However, there are problems that need to be dealt with, e.g. poisoning by impurity gases, hydrogen-induced disproportionation, which caused tritium storage performance degradation.On the basis of the literature review, a serial of ZrCo-based alloys were prepared with Ti, Hf, Sc, Fe, Ni as alloying element via arc-melting and vacuum annealing. Following research contents was carried out via Sievert hydrogen storage method and characterization methods such as XRD, SEM, EDX, TG-DSC, XPS, TPD to study on structure, PCT performance and kinetics of disproportionation of ZrCo alloy with Ti, Sc substituting Zr position and Ni, Fe substituting Co position, and composition distribution, phase structure, in addition, kinetics of hydrogen absorption and desorption, kinetics of disproportionation and isotope effects of Ce-doped Zr0.8Hf0.2Co alloys were studied, and then effect on interaction of impurity gas and ZrCo alloy with Ti, Hf, Sc, Fe, Ni was studied. Research results could promote development of tritium storage material and its application in large-scale deuterium/tritium fuel supply and storage system for ITER with scientific and applicated merit.(1) The major phases of ZrCo alloys with Ti, Sc, Fe, Ni substitution were ZrCo structure, wherein Ti substituting Zr leaded to decrease of lattice constant of ZrCo, and the lattice constant of ZrCo decreased with the content of Ti increased, and Sc, Ni, Fe Co substitution raised lattice constant of ZrCo. Desorption plateau pressure ZrCo alloys raised with content of Ti substitution increased, while Fe substitution led to desorption plateau decrease. Performance of anti-disproportionation of ZrCo with Ti doped was significantly improved, and the ability of anti-disproportionation increased with Ti substitution content increased, however, kinetics of disproportionation reaction of ZrCo with Fe, Sc, Ni doped was promoted in experimental condition. Comparing the rule of temperature of first step of hydrogen desorption, the lattice constant and kinetics of disproportionation, it could be inferred that the radius of hole sizes of less stable hydrogen occupation sites decreased with content of Ti substitution increasing, which reduced the proportion of hydrogen atom occupying8f2and8e site, and driving force of disproportionation decreased. On the contrary, the driving force of disproportionation of ZrCo with Fe, Sc, Ni doped increased. Ti substitution for Zr in ZrCo significantly reduced the initial kinetics of deuterium absorption. And its deuteride showed regular lamellar hydrides structure, which could reduce pulverization effect. And kinetics of hydrogen absorption and desorption decreased with content of Ti substitution increased. ZrCo alloys with Ti substitution in the range of x=0.1-0.2demonstrated good performance of hydrogen storage properties and anti-hydrogen induced disproportionation.(2) Hf Substitution for Zr in ZrCo alloy could improve the initial deuterium absorption kinetics, and also showed good performance on kinetics of hydrogen absorption and desorption. Impurity AB2phase increased with content of Hf substitution increased, which would cause capacity of hydrogen storage decreasing. Hydrogen desorption plateau pressure and performance of anti-hydrogen induced disproportionation of ZrCo significantly increased with increased content of Hf substitution.It is found that temperature, hydrogen pressure and times of disproportionation increment will accelerate kinetics of hydrogen-induced disproportionation. Thermal analysis for ZrCo with Hf substitution show similar rules of mechanism of enhancement of anti-hydrogen induced disproportionation with Ti substitution. ZrCo alloys with Hf substitution in the range of x=0.1-0.2demonstrated good performance of hydrogen storage properties and anti-hydrogen induced disproportionation.(3) Zro.8Hfo.2Co alloys with Ce doped could effectively reduce the formation of AB2and ZrOx impurity phase, which was beneficial to improve the homogeneity of alloy composition, and effectively enhance hydrogen storage capacity of Zr0.8Hf0.2Co alloy. Zro.8Hfo.2Co alloys with Ce doped also showed good performance of anti-disproportionation. It was found that the rate of deuterium-induced dispropor-tionation was slower than rate of hydrogen-induced disproportionation. Zr0.8Hf0.2CoCey-H system showed positive isotope effect at high temperature, and the isotope effect increased with temperature increment. In addition, temperature for the required supply pressure of ZrCoH3could be reduced with Hf,Ti substitution, which could reduce isotope effect in favor of deuterium and tritium supply gas composition control.(4) The kinetics of hydrogen absorption was found in the order of ZrCo0.8Fe0.2> ZrCo> ZrC0.8gNi0.2> Zro.8Hfo.2Co>Zr0.8Sc0.2Co> Zro.8Tio.2Co in hydrogen atmosp-here at room temperature.The resistance against CO poisoning of ZrCo increased with Hf substitution, and the CO poisoning effect of ZrCo would aggravate with Fe, Ti, Sc substitution. Regeneration temperature for modified ZrCo alloys by CO poisoned has been studied. TOF-SIMS, XPS and TPD tests showed that the CO poisoning effect of ZrCo would deterioate with Ti doped. And CO as complex carbon oxide was absorbed on the surface of ZrCo, and Zr and Co elements on surface were mainly in the form of existence of ZrO2and Co (OH)2, respectively. Theoretical calculations showed that CO tend to adsorb on Co top sites and Zr-Zr bridge site with chemisorptions on the ZrCo (110) surface. |
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