| Controlled nuclear fusion is considered as an ideal energy source in the future due to its inherent nuclear safety and durability.As one of the most important nuclear fuels for controlled fusion energy,tritium has great strategic significance,economic value and scientific research value.Therefore,tritium storage material used for storage,supply and recovery of deuterium and tritium is one of the key problems affecting the application of controllable nuclear fusion energy.The AB series alloys of intermetallic compounds represented by ZrCo have excellent low-pressure hydrogen isotope capture capability.The dynamic performance of hydrogen(tritium)absorption and release of ZrCo and its relatively mild hydrogen release conditions are regarded as a kind of tritium transport and storage material in ITER/CFETR and other important tritium-related projects.However,helium embrittlement caused by aging of tritium storage alloy is one of the key problems affecting the safe use of materials.It is of great scientific significance and application value for the development of nuclear energy technology such as controlled fusion and national defense technology to systematically study the behavior and residence mechanism of helium in ZrCo materials and to explore the improvement of its tritium storage and helium retention property.In order to improve the helium retention property of ZrCo storage tritium alloy and understand the behavior mechanism of helium in the material,Ti element doping method was used to improve the helium retention property of ZrCo materials.Helium-containing ZrCo and Zr-Ti-Co film samples were prepared by magnetron sputtering techno logy.The microstructure of the helium samples was less damaged and close to the true storage tritium metal material state.The alloy film samples with different helium contents were obtained by changing the argon/helium ratio in the working atmosphere.rutherford backscattering(RBS)and Elastic Ion Recoil(ERD)were used to characterize the concentration and depth of various substances in the thin film samples.The results show that the proportion of metal material composition and target alloy in the sample is consistent and evenly distributed,the helium in the thin film is evenly distributed,and the content of helium in the sample increases with the increase of the amount of helium in argon-helium mixture.The average helium content of ZrCo samples with low,medium and high helium content was 1%,5.9%and 11.8%,respectively,under the condition that QAr/QHe was 1/1,1/3 and 1/6,while the average helium content of Zr0.8Ti0.2Co samples was 1.1%,6.1%and 12%,respectively.Thermal Desorption Spectrometry(TDS)was used to study behavior of helium in helium-containing film samples.By comparing the helium thermal desorption spectra of ZrCo and Zr0.8Ti0.2Co thin film samples with different helium contents,the existence form and evolution behavior of helium atoms in the material were analyzed,which provided basic experimental data for the evaluation helium retention property of ZrCo after doping Ti.The experimental results show that under the condition of lower than 400? no matter the material and helium content changes,only a small amount of surface adsorbed helium is released.This part corresponds to the adsorbed helium and freely diffused helium atoms in the surface area of the thin film.The release peak in the range of 400?-800? is caused by the release of large helium bubbles at grain boundaries or defects.When the proportion of helium atoms in the material reaches 6at.%,the majority of the helium in the film exists in this state.In the release region at 800?-1300?,the release peak was superposed by helium clusters,helium vacancy complexes and small helium bubbles.At the early stage of the simulated aging period,the low helium content ZrCo showed only one release peak corresponding to the small helium bubbles in this region.The low helium content Zr0.8Ti0.2Co sample showed better performance in inhibiting helium migration and accumulation.it can be seen that the doping of Ti makes the helium thermal release peak of ZrCo material shift to the high temperature region,Zr0.8Ti0.2Co showing better helium retention property.The phases of the films were determined by grazing incidence X-ray diffraction(GIXRD),and the crystal structure data of helium-containing ZrCo and Zr0.8Ti0.2Co films were obtained.The results showed that the diffraction peaks of ZrCo and Zr0.8Ti0.2Co samples prepared on Mo substrate were basically the same as those of the sub-strong peaks,and the alloy films formed by sputtering mainly grew along the ZrCo phase(110),indicating that Ti doping did not affect the preferred orientation of the growth of ZrCo alloy films.The experimental results also showed that Zr0.8Ti0.2Co had a stronger inhibition on the tendency of amorphous helium.After high temperature treatment,the phase of the film changed obviously,mainly in the form of ZrO2 and Zr/Co/Ti/Mo ternary or quaternary alloy.The surface morphology of the thin film sample was observed by scanning electron microscope(SEM).When the helium atom ratio in the sample was about lat.%,the sample surface was flat.ZrCo and Zr0.8Ti0.2Co thin film samples showed the phenomenon of grain growth of the film.material after the high temperature thermal attachment test.The grain size of the material doped with Ti was larger and the grain boundary density was lower.Under high temperature conditions,the helium bubble migration and merger effect was enhanced,and the grain boundary became a favorable channel for helium bubble migration.The higher grain boundary density was conducive to the migration and fusion of small helium bubbles,which were then developed into large helium bubbles and burst,corresponding to the migration of the helium heat release peak of Ti doped ZrCo samples to the high-temperature region.The experimental phenomena provide a strong support for the establishment of the micro mechanism of Ti doping affecting the helium immobilization ability of ZrCo alloy film. |
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