Abstract
This paper studies the structure, temperature dependences of electric resistance, and adsorption properties of nanoporous three‐component V‐(N, He) coatings. The coatings were produced using the technique of ion beam assisted deposition, in particular, deposition of vanadium onto a titanium substrate simultaneously bombarding it with N2 + He ions of 30 keV. It is shown, in contrast to V‐N composites that have negative TCR (temperature coefficient of resistance), that the V‐(N, He) coatings have negative TCR only in the temperature range of 250 to 350 ∘C. A specific surface of pores and adsorption characteristics of V‐(N, He) composites depend on preliminary treatment of a titanium surface. A coating deposited onto an untreated substrate has specific surface of 25.5 m2/g. The preliminary irradiation of titanium with N2 + He beam up to a dose of 6 × 1017 ion/cm2 provides the increase in surface area up to 57.6 m2/g. The preliminary ion bombardment provides a considerable increase in hydrogen adsorption capacity of coatings. Especially, such impact is noticeable at the room temperature, when the amount of hydrogen absorbed by a coating that was applied onto a treated surface is more than three times of that absorbed by a coating that was deposited onto nonexposed titanium.
Highlights
Scientists believe that solid-state hydrogen storage devices used for the vehicles should have high net capacity, short fueling time and low desorption temperature
The studies of the initial stage of formation of VN composites including temperature coefficient of resistance (TCR) [1, 13] showed that the state of their grain boundary as well as TCR sign depend on Gibbs energy value of a given nitride
The bombardment of the deposited vanadium coating with the mixed beam of nitrogen and helium ions stimulates the formation of nitride phases whose intercrystal spaces contain equiaxial pores
Summary
Scientists believe that solid-state hydrogen storage devices used for the vehicles should have high net capacity, short fueling time and low desorption temperature In this regard proper consideration is given to metal hydrides and chemical hydrides that are used for these purposes though have definite drawbacks due to properties degradation, heavy weight and problems of waste disposal. The presence of a gas component within a deposited flow and a high degree of process nonequilibrium are required to form a porous coating It was shown recently [1, 2] that in case of ion beam assisted deposition the composites with low phase formation Gibbs energy have nanocrystalline structure whose intercrystal space is filled with nanopores. Such type of treatment provides transformation of a closed porosity into the open one
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