Fabrication And Hydrogen Transport Properties Of Novel Nb-Based Hydrogen Permeation Membranes

In recent years,the global hydrogen energy industry has developed rapidly,and technologies such as hydrogen production,hydrogen production and hydrogen filtration are crucial in the above industries.At present,the alloy hydrogen filter materials on the market are generally Pd and its alloys.Since the composition price of Pd is very high,about 600 yuan/g,and resources are limited,low-cost and high-permeability VB metals（Nb,V,and Ta）have become one of the main materials to replace Pd alloys.Among these alloys,Nb-based alloys have excellent hydrogen permeation performance,which has attracted the attention of scholars at home and abroad,and Nb-Zr-Ni and Nb-Hf-Co alloy systems have been developed successively.But so far,there are few reports on the research on Nb-Zr-Co alloys,and the relationship between microstructure and properties has not been established.In addition,the hydrogen-permeable alloy membranes currently prepared at home and abroad are generally sheet-shaped（0.8 mm thick,15 mm in diameter）,and the effective hydrogen-permeable area is small,which hinders the increase of the hydrogen-permeable flow rate.How to improve the shape of the alloy film and increase the flow rate of hydrogen permeation has become another problem restricting the development of the alloy film.To address these needs,a series of studies on the preparation and properties of new Nb-based hydrogen separation alloys were carried out in this paper,the details are as follows:（1）The microstructure and hydrogen transport properties of seven kinds of Nb-Zr Co quasi-binary phase diagrams were studied.The results showed that:with the increase of Nb element content,the primary phase of the alloy gradually transformed from Zr Co phase to BCC-（Nb,Zr）phase,and the primary BCC-（Nb,Zr）phase structure gradually changes from dendrite to short rod,the hydrogen solubility of the alloy increases,the hydrogen solubility coefficient decreases,and the corrosion resistance increases;（2）On the basis of the above research results,the ratio of Zr/Co is further changed to explore the microstructure change law and hydrogen transport performance of the alloy under different ratios.The research results show that the alloy composition located in the phase diagram（Nb,Zr）area,when Zr/Co>1,the primary phases in the alloy are all BCC-（Nb,Zr）phases,and the proportion of primary BCC-（Nb,Zr）phases is positively correlated with the content of Nb element,and also positively correlated with the Zr/Co ratio,where the impurity Zr₂Co phase ratio is positively correlated with the Zr/Co ratio.When Zr/Co<1,the primary phase in the alloy is basically the BCC-（Nb,Zr）phase,and the proportion of the primary BCC-（Nb,Zr）phase is positively correlated with the Nb element content,and there is basically no impurity Zr₂Co phase,But a new（Nb,Zr）₇Co₆phase appeared,and the proportion of this phase was basically negatively correlated with the Zr/Co ratio.Through hydrogen permeation experiments,this paper finds the only alloy composition point 4#(Nb₃₀Zr₃₁Co₃₉)with hydrogen permeation performance among the selected alloy components,and its hydrogen permeation coefficient is about 2.73◇10^-8mol H₂·m^-1·s^-1·Pa^-1/2,1.71 times that of pure Pd;（3）In order to reduce the cost of the alloy film and increase the hydrogen permeation flux of the alloy film,a new type of Nb-based alloy film without Pd catalytic layer was prepared by directional solidification technology,and the hydrogen permeation performance of the above alloy film was preliminarily studied:the research results showed that:directional solidification After solidification,the alloy structure changes from irregular eutectic to eutectic structure aligned along the growth direction,and the hydrogen permeation performance is improved,and the prepared V/DS-Nb₁₅Ti₅₅Fe₃₀/V alloy film has good hydrogen permeation performance and thermal stability.The performance of the Pd-coated catalytic layer of the Nb-based alloy film is far better than that of other Nb-based alloy films;the hydrogen permeation device of the tubular metal film was re-optimized,and the hydrogen permeation performance of the Pd/V/Pd tubular film at 773K was successfully tested using this device.