Preparation Of Helium-charaged Nanocrystalline Film And Study Of Its Helium Storage Characteristic

It is very important to study the behavior of helium in the tritiated materials for the field not only of military but also of nuclear enery.A unique feature of the magnetron sputtering in a He/Ar mixture atmosphere is that nanocrystalline film with helium inside like body material can be obtained. Nanocrystalline titanium films containing helium and LaNiAl films have been deposited by this method in this thesis. Crystallization and helium content in the Ti and LaNiAl films with changing experimental parameters were studied and the storage and release of helium in Ti films further studed. Crystallization and grain size of He-contained Ti film were determined by X-ray diffraction (XRD); Helium content and its distribution were measured by proton backscattering (PBS); Morphology of the films was observed by atomic force microscope (AFM); Existance of helium and its location in the film as well as the grain size are observed by transmission electron microscope (TEM); Trapped sites of helium in the films are analysed by neutre diffraction and thermo desorption spectroscopy (TDS). The results show that:(1)Nanocrystalline titanium films with grain sizes from 7.2nm to 44.2nm and helium content from 58% to 11.6% can be obtained by changing pressure P_Ar, pressure ratio of P_He/P_Ar and substrate temperature.(2)Nanocrystalline Ti films have a great helium storage capacity. The helium content of the films with the grain sizes form 9.9nm to 44.2nm decreases gradually from 38.6 at.% to 9.2 at.%. When it was storaged in room temperature for 12 month, the helium storage content is in the range of 93.4% to 42.6%.(3)Grain refining and cell parameter changing are resulted by the trapping of helium. The Bragg peak of (002) crystal plane of He-charged Ti film shifted to lower angles comparing with that of the pure Ti film and that of (100) crystal plane was unchanged, which indicates the lattice parameter c increases and a keeps the primitive value. The incorporation of helium has an inhibition function to the grain growth of the film.(4)Nanocrystallint titanium film with the He/Ti=22.9% also has the capacity to storage H. The site of helium in crystal lattice and n in He_n-V are changed and a new characteristic appears that the release peaks of helium shift to lower temperature after storaged H.(5)Helium content and the trapped sites of nanocrystalline LaNiAl film are controlled by the quality of LaNiAl sputtering target, P_Ar, pressure ratio of P_He/P_Ar and substrate temperature.(6)Helium-charging LaNiAl films with He/LaNiAl ratio from 5.7 to 13.8 percent can be obtained at the conditions of 2.8=P_He/P_Ar=8, 30℃～220℃and 305℃～325℃. It was found that the Helium existed in Hen-V cluster and prior occupied the (0.38, 0.44, 0.5) site for the middle temperature film, and the helium site was more complicated for the natural raising temperature film.The scientific value of this thesis is that it proved that nanocrystalline titanium films and LaNiAl films with different grain sizes have the capacity of storage helium and hygrogen.A new road has been opened with this thesis that the body materials can be directly transformed into He-charged nanocrystalline and simultaneity the grain size of nanocrystalline film can be controlled. This thesis has been setting up a foundation on studying deeply the mechanism of Helium storage in Ti and the ternary LaNiAl alloy.