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Synthesis and Research of Mg-based Hydrogen Storage Alloys

Author: GuoQing
Tutor: ChenYuAn
School: Chongqing University
Course: Materials Science and Engineering
Keywords: Mg-Based Hydrogen Storage Alloys Induction Melting Mechanical Alloying Element Substitution
CLC: TG139.7
Type: Master's thesis
Year: 2009
Downloads: 291
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Abstract


Having the advantage of high storage capacity, low density, pollution-free and a relatively low cost, the Mg-based alloys is a promising choice used for hydrogen storage materials. However, there’s still a long way for Mg-based alloys to be used as an ideal carrier of hydrogen because of its bad thermodynamics and kinetics properties in hydrogen absorption and desorption. The reactions occurring during the process of hydrogen storage require a high temperature and the velocity of these reactions is too slow. So a great amount of work focus on overcoming the weakness of Mg-based alloys mentioned above.In this thesis, three groups of Mg-based alloys（Mg-Ni,Mg-Ni-Co, and Mg-Ni-Zr） were prepared by induction melting, and three groups of alloys （Mg-Ni, Mg-Ni-Zr and Mg-Ni-Co） were synthesized by mechanical alloying which were milling by agate ball. These alloys were subjected to detailed examinations, including XRD, SEM analysis, gaseous hydrogen- storage-property testing. Moreover, the thesis has discussed how to improve the process of mechanical alloying. the results showed that:①Mg2Ni,Mg2Ni0.8M0.2（M=Co,Zr） and Mg2Ni0.6M0.4（M=Co,Zr） were prepared by induction melting. The chemical constitution analysis of these alloys showed that Co were dissolved into Mg2Ni successfully, but it was difficult for the Zr to be dissolved into Mg2Ni. XRD results showed that All of the samples prepared by induction melting contained the phase of Mg2Ni and Mg except the sample Mg2Ni which had no phase of Mg in。Because of the exisiting of Mg, the alloys had a good hydrogen absorption capacity, especially Mg2Ni0.6Zr0.4 reached 5.27% in a short time.②The alloys prepared by induction melting after milling improved the temperature of hydrogen absorption and desorption and decreased the time of hydrogen absorption, but it had slightly the capacity of hydrogen absorption decreased; As hydrogen desorption as concerned, it decreased the temperature.③Mg2Ni1-yZry（y=0.2, 0.4）和Mg2Ni1-yCoy（y=0, 0.1, 0.2, 0.4） were synthesized by mechanical alloying. All of them had the main phase Mg2Ni which transformed to the hydride of Mg2NiH4 after absorbing hydrogen. Besides, it was found Co2Mg which had ability of hydrogen absorption in Mg2Ni1-yCoy and Ni7Zr2 in Mg2Ni1-yZry.It did not have the ability of hydrogen absorption. So they reduced the ability of hydrogen absorption, which was the reason that the alloys prepared by induction melting were better than the alloys synthesized by mechanical alloying.④Compared with the samples prepared by induction melting, the samples prepared by mechanical alloying had better kinetics properties and lower temperature for hydrogen absorption and desorption. For the samples prepared by induction melting, the hydrogen storage properties improved as the times of cycle increased. In contrast, for the samples prepared by mechanical alloying, the first cycle had the best hydrogen storage properties.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Other special nature of the alloy > Hydrogen storage alloy
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