Accumulation and desorption of hydrogen isotopes bombarded on Ti-coated surface of metals

Applying the depth-profiling technique using the nuclear reaction D(3He,P)4He, hydrogen behaviors in Ti-deposition layer on substrate of SS304 and nickel have been observed fairly in details. Titanium is deposited on polished surface of SS304 stainless steel and nickel. Implantation of deutrium ions is carried out at three different energies. The low energy implantation (< 1 KeV) is performed by using the experimental set-up for plasma driven permeation of hydrogen. By keeping the probe voltage at 1 KV, a metal specimen is exposed by a flux of deutrium ions of energy less than 1 KeV. Implantation of 15 and 150 KeV is carried out by two different Cockcroft-Walton accelerators. The experimental results are as follows. 1) It seems to be difficult for implanted hydrogen to diffuse into the endothermic substrate. Implanted hydrogen tends to accumulate within the Ti-deposition layer. The upper limit of hydrogen concentration in Ti-deposition layer is - 200 a/o. 2) Concentration of hydrogen in Ti-deposition layer changes discontinuously by annealing within narrow ranges of temperature (< 100 deg C, -300 deg C and -400 deg C). There are three different energy states for hydrogen in Ti-deposition layer corresponding to concentration ranges of < 50 a/o, 50 - 100 a/o and > 100 a/o. By annealing at 450 deg C or higher temperature, all of hydrogen get out into gas-phase through the surface. 3) The thermal behavior of hydrogen in deposition layer is quite different in some cases from that of the metal. (Nogami, K.)