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By LZH | 11 August 2023 | 0 Comments

Thermodynamics of vanadium hydrides

What is vanadium hydride?
A novel magnesium-vanadium hydride synthesized by a gigapascal-high-pressure technique magnesium based vanadium doped hydride was prepared in a high-pressure anvil cell by reacting a MgH2-25%V molar mixture at 8GPa and 873K. However, the refined metal atom composition with vacancies on one of the magnesium sites corresponding to Mg6V is nearly in line with EDX analysis. TPD analysis and TG-DTA also studied the new compound's thermal properties. The new vanadium hydride was found as one subhedral crystal, about 20 μm in size, coexisting with V0 and (V-Al)-alloys enclosed in hibonite. Microprobe analysis of this grain (carried out using a CAMECA 100X electron microprobe at 15 kV, 10 nA, one μm beam size, counting times 20s for peak and 10 s for background) showed only V, with minor Al (~5 atom%). To get information on the crystal structure, the small VH2 fragment was handpicked from the polished section under the reflected light microscope and mounted on a five μm diameter carbon fiber, which was, attached to a glass rod. Then the fragment was tested by single-crystal X ray diffraction. Single crystal X-ray studies were take using a Bruker D8 Venture diffractometer equipped with a Photon III CCD detector, with graphite-monochromatized MoKα radiation. Since we have only one grain, we have prevent destructive analysis to quantify the hydrogen content. The structural data (see below) represent solid proof supporting the VH2 stoichiometry.

Thermodynamics of vanadium hydrides
According to Yukawa et al. (2002), vanadium metal absorbs hydrogen and forms first the β1 phase (V2H low-temperature phase). Then, as the hydrogenation proceeds, the first-order phase transition from the β1 phase to the β2 phase (V2H high-temperature phase) or γ′ (VH) takes place. Finally, the γ phase (VH2) is formed when it is fully hydrogenated. As a result, two plateaus exist in the V-H system's PCT (pressure-composition-temperature) curve. The first plateau corresponds to the coexistence of the α phase (hydrogen solid solution phase) and the β1 phase. However, the β1 phase is so stable that the first plateau pressure for this hydride formation is as low as 0.1 Pa at moderate temperatures. Therefore, the hydrogen desorption reaction from the β1 phase never occurs under moderate conditions, for example, at room temperature. On the other hand, the second plateau marks the coexistence of the β2 phase (VH) and the γ phase, VH2, which corresponds to the natural compound we have identified. As the γ phase is unstable, hydrogen absorption and desorption reactions can occur at moderate temperatures and pressures. For this reason, only about half of the hydrogen dissolved in vanadium metal can be used in the subsequent hydrogen absorption and desorption processes.

Vanadium hydrides at high pressure and temperature
Vanadium hydrides are usually prepared electrolytically by heating vanadium metal with hydrogen (Müller & Weymann, 1986). Therefore, the observed abundance of V0 and V-Al alloys in our samples may suggest that VH2 formed by a localized reaction in the presence of free hydrogen. Suzuki et al. (1989) studied the system (transition metal)-silicate-water at pressures of around 5 GPa and at temperatures ranging from 1000 to 1300 °C using a tetrahedral-anvil high-pressure apparatus and quenching the products isobarically. In their study of the system V-silicate-water, they observed the formation of V-oxide dendrites enclosed in vanadium dihydride, VH2. The petrographic relationships between the two phases clearly showed that hydrogen and oxygen coexisted and dissolved in liquid vanadium at high pressure and temperature. Such a scenario might apply to what is observed in the Mt Carmel samples but with some differences. We found metallic vanadium and (V-Al)-alloys instead of V-oxides, indicating an almost anoxic environment. However, some of the metal inclusions show typical "dense branching structures" (dendrites) (Müller & Weymann, 1986; Griffin et al., 2019a) and are associated with sporadic VH2. This represents striking evidence that free hydrogen was present and could form some VH2 from V0.

Price of Vanadium hydride
Vanadium hydride particle size and purity will affect the product's Price, and the purchase volume can also affect the cost of Vanadium hydride. A large amount of large amount will be lower. The Price of Vanadium hydride is on our company's official website.

Vanadium hydride supplier
Luoyang Tongrun Nano Technology Co. Ltd.  (TRUNNANO) Luoyang City, Henan Province, China, is a reliable and high-quality global chemical material supplier and manufacturer. It has more than 12 years of experience providing ultra-high quality chemicals and nanotechnology materials, including Vanadium hydride, nitride powder, graphite powder, sulfide powder, and 3D printing powder. If you are looking for high-quality and cost-effective Vanadium hydride, you are welcome to contact us or inquire at any time.


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