Behavior Of Helium In Palladium And Iron Films

The problems caused by helium are common in the research related to fusion energy, nuclear technology and experiments about tritium. They may lead to microstructure changes, aging, severe helium embrittlement and the contaminants of plasma. To solve these problems, we must make it clear that: why helium could state in these materials; what disadvantages whill bring to the performance of these materials by these processes; what the influence factors of these processes and how we could control them. These problemes were came up from metaphase of 20th century, and that from 1970s, with the design of fusion reactor and the research development of its materials, we make it sure that these problems must be solved firstly.Currently, stainless steels are used as the principla wall materials in fusion reactors, and iron is one main ingredient of stainless steel. Meanwhile, palladium has the same electronic configuration as helium and it could be applied for tritim-storage owing to its strongest capacity to retain helium in metals as far as we know. Thus, we choose iron and palladium to perform our research.In this thesis, we prepared palladium and iron films in the substrate through electron beam evaporation, and characterized the composition and structure of the two films. Then helium ions with different energy and dose were implanted in the palladium and iron films. The process of implantation was simulated with SRIM, and the distribution of helium and recoil atoms as well as the damage of the films was got. Through XRD analysis, we found the lattice swelled as the dose of implantation increased in both two films, and the dwelling was related to the existence of recoil atoms and helium-vacancy composites. AFM and SEM results showed that the surface of the two films became flatter because of the sputtering process. Finally, the EPBS and ERDA results testified the existence of helium in both films.In the theory aspect, to explain the swelling phenomena in metal crystal lattice,we simulated the evolvement process between helium and the defectes of iron (general vacancy and self-interstitial atom) in different anneal temperature after the implantation using lattice kinetics monte-karlo program (LKMC). The LKMC program result showed that, both in room anneal temperature and high anneal temperature, most of the helium atoms exist in the metal with the form of helium-vacancy cluster. The result of LKMC simulation could well explain the phenomenon of experiments.