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Experimental procedure of vanadium hydride

Vanadium, V–5Cr, and V–5Ti alloys were prepared from 99.9% pure vanadium by arc melting in an argon atmosphere. The nuggets were cold-rolled and punched into tensile specimens for in situ straining experiment with a gauge size of 2×7 mm2 and 0.1 mm in thickness. The samples were evacuated in a quartz tube and annealed in a vacuum at 1000 °C for one h. Hydrogen was doped into the samples in a high-pressure oven at 450 °C with 0.5 and 0.8 MPa hydrogen pressures. The first visible evidence of the effect of hydrogen in the samples comes from early examination during sample preparation. In the electro-polishing process, an acid solution is projected from both sides of the sample, making the material in the center progressively thinner until a hole is formed. Fig. 1 compares the final shape of the electro-polished hole of non-hydrogenated V–5Ti with the same alloy charged with a metal/hydrogen ratio of 0.24. The hydrogen distribution in the samples is not uniform. Regions rich in hydrogen are prone to form the hydride, which makes some regions more brittle than others altering stress distributions and promoting the failure of susceptible regions. Stacking faults bounded by dislocations are promoted in zones where hydrogen is accumulated. The main characteristic of fracture in hydrogenated samples is the formation of barriers that block the free movement of dislocations. The reaction of hydrogen gas with magnesium metal, which is important for hydrogen storage purposes, is enhanced significantly by adding catalysts such as Nb and V and using nanostructured powders. In situ, neutron diffraction on MgNb0.05 and MgV0.05 powders give a detailed insight into the magnesium and catalyst phases that exist during the various stages of hydrogen cycling. During the early stage of hydriding (and deuteride), an MgH1<x<2 phase is observed, which does not occur in bulk MgH2 and, thus, appears characteristic for the small particles. The abundant H vacancies will cause this phase to have a much larger hydrogen diffusion coefficient, partly explaining the enhanced kinetics of nanostructured magnesium. It is shown that under relevant experimental conditions, the niobium catalyst is present as NbH1. Second, a hitherto unknown Mg−Nb perovskite phase could be identified that has to result from the mechanical alloying of Nb and the MgO layer of the particles. Vanadium is not visible in the diffraction patterns, but electron micrographs show that the V particle size becomes very small, 2−20 nm. Nanostructuring and catalyzing the Mg enhance the adsorption speed so much that now temperature variations effectively limit the absorption speed and not, as for bulk, the slow kinetics through bulk MgH2 layers. If you are looking for high quality, high purity and cost-effective anadium hydride, or if you require the latest price of anadium hydride, please feel free to email contact mis-asia.

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