Study On Vanadium Based Solid Solution Hydrogen Storage Materials

As a new kind of storage hydrogen material, vanadium-based solid solution alloy has bright future, With high hydrogen storage capacity(3.8wt%), and excellent diffusion rate in vanadium-based hydride. However, now alloy manufacture mainly adopts pure vanadium as raw material, and uses vacuum electric arc or vacuum response melt to preparation, these cause alloy to be expensive, and limit its application. In the article the author on the one hand takes relatively cheap V₂O₅ and NH₄VO₃ as raw material, and uses the Self-propagating High-temperature Synthesis technology (SHS) to produce vanadium-based solid solution alloy, which is of economic significance to synthetically exploited resource of vanadium and titanium in the west of China; On the other hand the author systematically investigated the electronic structure of VH_x and V₅₁M₁₂H₆₄ with quantum chemical method (DV-Xa). The result has an important theoretical role to optimize design of vanadium -based alloy.Through theoretical calculations, it is proved that the self-propagating can sustain the Self-propagating High-temperature Synthesis reaction in the adiabatic combustion temperature and reaction heat per unit mass on the composition of V₂O₅-TiO₂-Cr₂O₃-Ni-Al and NH₄VO₃ - TiCO₂- Ni - Al systems are calculated. Then through many experiments, we have gained the proportion of raw materials for V₃TiNi_0.56Al_0.2, and produced V₃TiNi_0.56Al_0.2 and V₃TiNi_0.56Al_0.2Cr_x(x=0. 1,0.2,0.3) with SHS.The result in the experiment indicates that the microstrucrure of V₃TiNi_0.56Al_0.2 in V₂O₅-TiO₂-Cr₂O₃-Ni-Al and NH₄VO₃-TiO₂-Ni-Al systems with SHS is close to the microstructure of alloys which take pure metal as raw material and by vacuum response smelt. The alloys consist of two phases, the main phase is vanadium-based solid solution, TiNi-based distribute the boundaries of main phase. After activated twice, the charge-discharge test of the electrode is conducted by charging at 100A/g and discharging at 60mA/g. The alloys can reach maximum value of 350mAh/g for V₃TiNi_0.56Al_0.2 with SHS . But the discharge capacity decreases and vanishes at the 10th cycles, Diffusion coefficient of hydrogen is smoll, DH=1.424×10^-12cm²/s.After heat treated of 1173K × 4h and 1573K×4h for V₃TiNi_0.56Al_0.2, alloys still consist of vanadium-based solid solution phase and TiNi-based. Heat treatment diminishes segregation, and the chemical compositions of the alloy is more homogeneous. When the temperature of heat treatment rises, the lattice parameter and...