| Hydrogen storage alloy is a safe and efficient hydrogen storage medium,and its development plays a key role in the wide application of hydrogen.LaNis alloy is a hydrogen storage alloy with excellent performance and mature development.However,in its application,it is found that non-metallic impurities such as C,N,O and S in the alloy matrix will form CH4,NH3 and H2S along with the hydrogen evolution process of the alloy.Thereby affecting the purity of the hydrogen released from the alloy,resulting in waste of the hydrogen source.In view of the above problems,this thesis systematically and deeply studied the preparation and purification methods of low C high purity LaNis alloy.In this thesis,the effects of various process parameters of plasma arc melting,hydrogen plasma arc melting and hydrogen solution treatment on the change of C content in LaNis alloy were studied.The mechanism of C removal was analyzed and studied.In view of the above problems,this thesis systematically and deeply studied the preparation and purification methods of low C high purity LaNis alloy.In this thesis,the effects of various process parameters of plasma arc melting,hydrogen plasma arc melting and hydrogen absorption dehydrogenation on the change of C content in LaNis alloy were studied.The mechanism of C removal was analyzed and studied.Firstly,the research on plasma arc melting method was carried out.The effects of melting current,melting time and pressure in furnace atmosphere on the content of non-metallic impurities in the alloy were studied.Different plasma atmospheres of erbium-doped and hydrogen-doped were studied.The effect on the content of non-metallic impurities in the alloy.Subsequently,hydrogen plasma arc melting method was developed to study the effects of hydrogen addition,melting time,melting current and furnace pressure change on the effect of C removal.It was found that the increase of hydrogen doping amount,the increase of melting current and the prolongation of melting time in a certain range all improve the effect of removing C,and the decrease of pressure in the furnace atmosphere suppresses the action of removing C.The presence of CH4 was found by the detection of the atmosphere in the furnace after melting,indicating that the impurity C was removed in the form of CH4 during the melting process.According to the variation of alloy C content with the melting process parameters,a set of orthogonal experiments was designed.The effect of hydrogen doping on the content of alloy C was determined by orthogonal test results>melting time>melting current.Under the condition of 230A melting current,the hydrogen doping amount is 25%H2,and the impurity C content in the LaNis alloy obtained after melting for 30 min was reduced to 14 ppm,and the chemical purity of the alloy was 99.9835%.In addition to the traditional melting purification method,this paper explores the effect of hydrogen absorption and dehydrogenation on the C content of the alloy.It was found through experiments that the impurity C in the LaNis alloy was mainly removed in the form of CH4 during hydrogen evolution.The higher the original C content of the alloy,the higher the CH4 content in the H2,and the higher the removal rate of the impurity C in the corresponding alloy.At the same time,as the number of hydrogen absorption cycles of the alloy increases,the CH4 content in the H2 was gradually reduced.The hydrogen absorption dehydrogenation method can effectively reduce the impurity C content inside the alloy without changing the phase structure of the alloy.After mastering the mechanism of hydrogen removal and dehydrogenation in addition to C,this paper further studied the effects of hydrogen absorption,hydrogen treatment temperature and treatment time on the effect of Cremoval.It was found that the change of hydrogen absorption of the alloy had no significant effect on the removal of C,and the content of C in the alloy decreased with the increase of treatment temperature after hydrogen absorption and the prolongation of time. |
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