Structural Modulation And Hydrogen Permeability Of V-Pd(Fe) System Alloys

Hydrogen energy is a sustainable,high combustion calorific value,environmentally friendly and diverse storage form of secondary energy,and the separation and purification process of hydrogen is an important part of the application of hydrogen energy,only Pd-Ag alloys among the current alloy hydrogen permeation membrane materials have achieved commercial application,and these alloys show good hydrogen permeation performance and anti-hydrogen embrittlement performance,but due to the rarity of Pd resources and high cost It is difficult to achieve large-scale industrial applications.The high hydrogen permeability of vanadium（V）,a group VB metal,has become a hot topic of research for many researchers.However,the hydrogen solubility of V metal is high,and the use of pure V as hydrogen permeation membrane material is prone to hydrogen embrittlement,resulting in the destruction of the membrane structure,which cannot meet the hydrogen permeation work.In order to solve the problem of hydrogen embrittlement of V metal,structural modulation of V metal by elemental doping alloying is used to reduce its hydrogen solubility and improve its hydrogen embrittlement resistance.In this paper,we design V-based alloys based on the concept of"lattice matching"and investigate the effects of Fe and Pd doping on the crystal structure and hydrogen embrittlement properties of V-based solid solutions.The main work is as follows:（1）V_100-xFe_x（x=2,4,8）binary solid solution alloy was prepared by the non-self-consuming high vacuum arc melting furnace method,XRD analysis shows that V_100-xFe_x（x=2,4,8）alloy is a single phase structure（BCC）,Fe doping to form V-Fe solid solution,causing a decrease in the metal V lattice constant,lattice shrinkage distortion,the degree of lattice shrinkage distortion increases with the increase of Fe doping.The hydrogen solubility of V-Fe alloy decreases with the increase of doping amount,the enthalpy of hydrogen absorption reaction increases,the mechanical properties are improved,and the hydrogen embrittlement resistance of V-based alloy is improved.It is found that the hydrogen permeation coefficient of V₉₂Fe₈ alloy is 7.85×10^-8 mol H₂m^-1s^-1Pa^-0.5 at 673 K,which has a better overall hydrogen permeation performance and is4.90 times better than that of pure Pd under the same hydrogen permeation conditions.（2）V_100-xPd_x（x=2,4,8）binary solid solution alloy was prepared by the non-self-consuming high vacuum arc melting furnace method,XRD analysis shows that V_100-xPd_x（x=2,4,8）alloy is a single phase structure（BCC）,Pd doping to form V-Pd solid solution,causing an increase in the metal V lattice constant,lattice expansion distortion,the degree of lattice expansion distortion increases with the increase of Pd element doping.Pd doping can significantly reduce the hydrogen solubility of vanadium-based alloys,increase the enthalpy of hydrogen absorption,improve the mechanical properties,and improve the hydrogen embrittlement resistance of V-based alloys.V_100-xPd_x（x=2,4,8）system alloys have high hydrogen permeability coefficients,and the hydrogen permeability coefficient becomes larger with increasing temperature and decreases with increasing doping.It was found that the hydrogen permeation coefficient of V₉₂Pd₈ was 10.221×10^-8 mol H₂ m^-1s^-1Pa^-0.5 at 673 K,which has a very good integrated hydrogen permeation performance and is 6.38 times higher than the hydrogen permeation performance of pure Pd under the same hydrogen permeation conditions.（3）V_100-2xPd_xFe_x（x=1,2,4）ternary alloy was prepared by the non-self-consuming high vacuum arc melting furnace method,and the XRD refinement results showed that the V_100-2xPd_xFe_x（x=1,2,4）ternary alloy has a single-phase structure（BCC）,and the Pd and Fe elements are solidly soluble in metal V.The lattice constants tend to converge to metal V when they are co-doped,and the lattice distortion is minimized.The hydrogen solubility of V metal decreases with the increase of Pd and Fe doping,and the enthalpy of hydrogen absorption also increases,and the hydrogen embrittlement resistance is improved.hydrogen permeation coefficient of V_100-2xPd_xFe_x（x=1,2,4）cast alloy decreases with the increase of doping,and under the same conditions,the hydrogen The hydrogen permeation coefficient is higher than that of the V_100-xFe_x（x=2,4,8）system alloy and lower than that of the V_100-xPd_x（x=2,4,8）alloy under the same conditions.It was found that the higher the doping amount,the lower the hydrogen solubility and the better the hydrogen embrittlement resistance of V-based alloys.At 673 K,the hydrogen permeation coefficient of V₉₂Pd₄Fe₄ was 8.717×10^-8 mol H₂ m^-1s^-1Pa^-0.5,and the alloy showed good comprehensive hydrogen permeation performance,which was 5.45 times higher than that of Pd under the same conditions.The"lattice matching"can maintain the high hydrogen permeation performance of V metal.