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Synthesis Of Mg Based Hydrogen Storage Alloys By Mechanical Grinding

Posted on:2014-04-27Degree:MasterType:Thesis
Country:ChinaCandidate:C Y ZhouFull Text:PDF
GTID:2251330392471596Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
As the shortage of the natural resouces and the environmental problems brought bythe long-term fossil energy consuming,Human-beings need to find a newenvironment-friendly energy. The hydrogen energy becomes a vital object of research asits perfect properties of the proper price and the large amount of heat release. But thekinetics and thermodynamics of hydrogen storage alloys are poor and easily affected bythe environment,which restrict the development of hydrogen energy. Mg-basedHydrogen Storage Alloys becomes a kind of preferable hydrogen storage materialbecause it has lots advantages, such as the high storage of hydrogen(the mass fraction is4.4wt%in theory),the low price and the easy acquisition of the Mg and Al.Mechanical grinding is employed in the preparation of Mg17Al12.The mosteffective grinding parameters are chosen:a12h-ginding-time, stainless grinding bottles,a600rmp bottles rotary velocity, a20:1ball percentage. The alloys are prepared intheArgon-filled stainless steel bottles.In case the alloys bond on the interior walls of thebottles and hinder the preparation of alloys,the bulk of alloys are broken in theArgon-filledVacuum glove box in every two hours.The surface of alloys were modified,in the meantime the Mg17Al12+M(M=5%Cu、10%Cu、5%Ni、10%Ni、10%B、15%B、10%C、15%C)were prepared by grinding. XRDanalysis and PCT test device were employed to analyses the properties of the alloys inresearching the most effective hydrogen storage alloys.This research demonstrates that all the Mg17Al12which grinded by12h haveeffective hydrogen storage properties. The hydrogen absorption of Mg17Al12is4.17wt%under623K which access the theoretical value(4.4wt%), and the amount of desorptionis54.6wt%under653K.A small amount of Al-Ni phaseand MgCu2was generated in the progress ofhydrogen absorption after the Ni and Cu were added into Mg17Al12+M(M=5%Cu、10%Cu、5%Ni、10%Ni)respectively. These compounds performed as catalysis in theprogress of hydrogen absorption and desorption. Cu modified the surface performanceof the Mg17Al12, and improved its kinetics of hydrogen absorption markedly. Thehydrogen absorptions alloys added by5%Cu and10%Cu were4.07wt%and3.9wt%respectively in240min under623K, and they both access the theoretical values. Thealloys added by Ni and Cu have good desorption plateaus. After the C was added into Mg17Al12by grinding, absorptive abilities in the twolow–temperature groups werenot improved obviously, even were worse than theabilities of pure Mg17Al12, but they did better in high temperatures. The Mg17Al12alloysadded by B have bad hydrogen storage abilities in both low and high temperatures. TheB even hindered the hydrogen absorption of Mg17Al12.In conclusion, the B is not properto be employed in modifying the surface performance of Mg17Al12.The mechanical milling were used to grind Mg, Al, Cu powder with atomic ratio of17:11:1and17:10:2for12h, and get a new composite hydrogen storage alloy. Studieshave found that the hydrogen content of Mg17Al11Cu alloy reaches about4.07wt%in623K,60min。And the hydrogen absorption rate is faster than that of5%Cu. At the sametime, the alloy has perfect hydrogen platform under553K.
Keywords/Search Tags:Mg-Al based hydrogen storage material, ball-milling, composite grinding, Hydrogen-storage-property
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