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Study On The Hydrogen-induced Disproportionation Properties And It's Modification Of Zr2Fe Alloy

Posted on:2017-03-08Degree:MasterType:Thesis
Country:ChinaCandidate:A LiFull Text:PDF
GTID:2311330485987198Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
As a hydrogen-absorbing material, Zr2 Fe alloy had the advantages of high speed and efficiency in hydrogen absorption. It could be applied in the recycling area of hydrogen and its isotopes. But the biggest problem for the usage of Zr2 Fe alloy was that it could be easily forced into disproportionation by the effect of high temperature and hydrogen pressure. The service life of Zr2 Fe alloy could be strongly reduced.On the premise of not changing Zr2 Fe alloy's original crystallographic structure, This paper using the method of elements' replacement to improve the anti-disproportionation reaction capability of Zr2 Fe alloy. The crytall structure and microstructure of the alloy was analyzed by X-ray diffraction?XRD? and scanning electron microscopy?SEM?, the dynamic curve for hydrogen absorption and disproportionation was tested by Sieverts' Law testing system, the thermodynamic properties of the hydride was analyzed by the Differential Scanning Calorimeter.Firstly, the basic structure and properties of Zr2 Fe alloy and its hydride was obtained by the professional testment, the reserching results showed that the melting prepared the Zr2 Fe alloy with single phase, and Zr2 Fe formed into Zr2FeH5 phase after hydrogen absorption and the Zr2FeH5 phase belongs to tetragonal structure. By the analysis on Zr2FeH5 phase after the treatment under different temperatures and same hydrogen pressure, the effect of temperature on the disproportionation reaction process of Zr2FeH5 phase could be obtained. The kinetic curve of Zr2FeH5 phase's disproportionation was measured under different conditions of temperature and pressure, the synergistic effect of temperature and hydrogen pressure on the process of disproportionation reaction was obtained. According to all these results, the temperature range which Zr2FeH5 phase disproportionated rapidly was obtained, also the primary and secondary to the influence of temperature and hydrogen pressure on disproportionation reaction was obtained. The characteristics of hydrogen desorption was analyzed by differential scanning calorimetry?DSC? and X-ray diffraction under heating process, also the enthalpy change during the reactiong was calculated by the DSC data.Based on the formal results, using the element of Ti substituted Zr of Zr2 Fe alloy in different proportions. On the premise of Zr2 Fe alloy's original phase structure, through the analysis for the Zr2 Fe alloy in different Ti sustitutions on hydrogen absorption curve disproportionation kinetic curve and thermodynamic properties of the hydrogen absorption phase, the conclusion that the substitution of Ti in Zr2 Fe alloy was helpful for improving Zr2FeH5 phase's anti-disproportionation ability could be obtained, the best substitution proportion of Ti without changing the structure Zr2 Fe alloy was obtained.On the basis of Ti element's modfication for Zr2 Fe alloy, using Ni substituted Fe of Zr2 Fe alloy. The effect of Ni substituted in different proportions to the structure of Zr2 Fe was tested, the maximum replacement ration of Ni element in Zr2 Fe that maintaining Zr2 Fe alloy's single phase was obtained. The hydrogen-absorbing properties, thermal properties and disproportionation properties of Zr2 Fe alloy with Ni element's replacement was also tested, the conclusion that Ni element's substitution could improve the anti-disproportionation property was proved by these testments.Finally, considering about the working environment and using conditions of the alloy that had been modificated, the testment on the hydrogen pressure and temperature which against disproportionation reaction was carried. The using parameters which disproportionation reaction did not occurred was obtained.Basing on the formal research, the conclusion was drew below:?1? Zr2FeH5 phase would be forced into disproportionation under high temperature and hydrogen pressure, the reaction was identified as 2Zr2FeH5? 3ZrH2+ZrFe2+2H2?; Comparing to the hydrogen pressure, temperature was the main factor that influenced the disproportionation process, the speed of reaction was getting faster as the temperature rised; The temperature range that the disproportionation reaction occurred rapidly was 500?;?2? The substitution amount of Ti element for Zr under 0.03 would not change the original phase structure of Zr2 Fe alloy, Zr2-xTixFe?X?0.03? alloy still remainsthe great activity in hydrogen absorption, the hydrogen storage capacity increased as the substitution of Ti element added. Ti element's substitution made ZrH2 and TiH2 phase appear in Zr2-x TixFe?X?0.03? alloy's hydrogen-absorbing phase, the spread of ZrH2 and TiH2 phase inhibited the disproportionation reaction and slowed the reaction process.?3? The substitution amount of Ni element for Fe under 0.10 would not change the original tetragonal structure of Zr2 Fe alloy, but lattice gap was shortened by Ni element's influence, and the kinetic activity of hydrogen absorption was weakened. The stability of Zr1.97Ti0.03Fe1-yNiy?Y?0.10? alloy's hydride decreased. The substitution of Ni element suppressed the hydride's disproportionation reaction, the anti-disproportionation ability was enhanced. Within 24 hours using time, 300?and 0.62 MPa hydrogen pressure could be used as the safe parameter.
Keywords/Search Tags:Zr2Fe Alloy, Crystallographic Structure, Hydrogenation Kinetics, Disproportionation Kinetics, Thermodynamics
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