Nano Archive

Application of Mg-x wt% MmNi5 (x = 10-70) nanostructured composites in a hydrogen storage device

Vijay , R and Sundaresan , R and Maiya , M. P and Srinivasa , Murthy S (2007) Application of Mg-x wt% MmNi5 (x = 10-70) nanostructured composites in a hydrogen storage device. International journal of hydrogen energy, 32 (13). pp. 2390-2399. ISSN 0360-3199

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Abstract

Large batches (800 g) of nanostructured Mg-xwt% MmNi5 (x = 10-70) composites were prepared by ball milling elemental Mg with MmNi5 in an attritor for 12h under hydrogen atmosphere. There was no alloy formation between Mg and MmNi5 within the milling times employed. The grain size of Mg in the composite varied from 28 to 45 nm, increasing with Mg content, whereas that of MmNi5 was constant at 12nm, irrespective of its concentration in the composite. BET surface area of the milled composites was in the range of 25 to 58m2/g, increased with MmNi5 content. The absorption kinetics and capacities of these composites were measured at 100, 200 and 300°C under 30 bar hydrogen pressure on a small sample of about 8 g. The samples absorbed at all the temperatures, the absorption rate increases with increase in MmNi5 content. But the rates decreased marginally with temperature and attained steady state in less than 400s even at 100°C. However, the hydrogen absorption capacity of the composites followed the Mg content at all the temperatures, with Mg-10wt% MmNi5 showing the highest capacity of 5.1 wt%. MmNi5 has a significant effect on the absorption of hydrogen by Mg at temperatures as low as 100°C, even though hydride of MmNi5was not present in the hydrogenated composite. The nanostructure of Mg together with distribution of MmNi5 on grain surface/grain boundary of Mg appears to have enhanced the absorption, with MmNi5 probably acting as a conduit for hydrogen diffusing into Mg grain. The performance of hydrogen storage device with larger quantities of Mg-MmNi5 composites (350-500 g) was evaluated in the temperature range of 100-150°C with supply pressure of 10-30 bar. The absorption rates and quantity of hydrogen absorbed increased with supply pressure and decreased with temperature. The fraction a was more than 70% in compositions with up to 10-30 wt% MmNi5, but was much lower at higher MmNi5 content. The absorption behaviour of these composites followed the same trend as in the case of testing on smaller sample size.

Item Type:Article
Subjects:Physical Science > Nanophysics
Physical Science > Nano objects
Material Science > Nanochemistry
Material Science > Nanostructured materials
Divisions:Faculty of Engineering, Science and Mathematics > School of Physics
Faculty of Engineering, Science and Mathematics > School of Chemistry
ID Code:5624
Deposited By:JNCASR
Deposited On:11 Aug 2009 07:20
Last Modified:11 Aug 2009 07:20

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