Study Of Li And Sn Ion Implantation Impact On Chemical State, Crystal Structure And Nano-hardness Of W

Liquid lithium has the advantages of suppressing edge localized modes (ELMs), improving the electron temperature and reducing neutron damage, and so on. At the same time, the principal advantage of applying tin, in particular, is that it has low vapor pressure, low melting point and not readily forming a stable hydride. Hence, liquid lithium or tin provide the most promising candidate to replace traditional solid tungsten plasma facing component (PFC). Although liquid plasma facing component, in particular, liquid lithium has been done a number of experiment researches and showed many dramatic conclusions, lithium or tin penetrate into tungsten material in magnetic confinement fusion condition, which changes properties of physical, chemical and structural of tungsten. In addition, the changes bring also a range of serious challenges, such as retention of hydrogen isotopes. Therefore, it is more meaningful for application of liquid PFC to study interaction of between tungsten and lithium or between tungsten and tin and the change of tungsten properties. Moreover, by new way tungsten material surface is modified.Lithium or tin ions are implanted into tungsten target by MEVVA ion implantation machine to produce a Li-W or Sn-W modified layer. Changes of Chemical composition, surface chemical state, surface layer crystal structure and nano-hardness of tungsten are studied when Li or Sn ions are implanted W. In addition, we discuss that how to be affected for W surface property and mechanical property due to defects caused by interaction of between Li and W or between Sn and W. The Li-W or Sn-W modified layers are analyzed by many testing ways, such as XPS and SRIM process simulation. Firstly, the results show that after Li or Sn ions are implanted into tungsten target, modified layer with a certain thickness are formed and thickness of the Li-W modified layer reach the 200 nm.Secondly, when Li or Sn ions are implanted into tungsten target respectively, the interaction of between Li and W or between Sn and W will change crystal structure of W, causing a lot of defects in W, such as such as lattice distortion, vacancies and self-interstitial atoms, which lead to making diffraction peak broaden or narrow. Thirdly, chemical shift of Li, Sn and W atoms connect with chemical reaction of O and C atoms in the near surface layer. however, point defects, such as vacancies and self-interstitial atoms, can lead to chemical shift in the modified layer, which make binding energy of Li 1s increase by 1.9-2.5 eV and make binding energy of W 4f increase by 0.3-0.5 eV in the Li-W modified layer, and which make binding energy of W 4f7/2, W 4f5/2, W 5p3/2 and W 4p1/2 decrease by 0.3 eV,0.3 eV,0.4 eV and 1 eV-1.4 eV respectively in the Sn-W modified layer, and which make binding energy of Sn 3d5/2 decrease by 0.6 eV-0.7 eV and make binding energy of and Sn 3d3/2 decrease by 0.1 eV-0.3 eV in the Sn-W modified layer. A large number of defects are produced by Sn ion implantation, so they lead to making binding energy of W4f and Sn3d decrease. Fourthly, after Li or Sn ions are implanted into tungsten target respectively, nano-hardness increase obviously comparing with pure W in the modified layer. Fifthly, when a large number of point defects are produced by Li ion implantation, such as vacancies and self-interstitial atoms, they can lead to making surface energy increase and improve surface property of W.