Formation of Nd2Fe14B hydride by milling of anhydride particles in toluene in a closed reactor

Ram, S. ; Banerjee, H. D. ; Haldar, S. ; Ramachandrarao, P. (1997) Formation of Nd2Fe14B hydride by milling of anhydride particles in toluene in a closed reactor Bulletin of Materials Science , 20 (8). pp. 1049-1058. ISSN 0250-4707

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When milling micrometer thin Nd2Fe14B platelets, of an average 1-2 mm diameter, in toluene in a closed reactor, part of the toluene decomposes at the surface of the platelets and yields nascent hydrogen and carbon/low hydrocarbons. The hydrogen diffuses into the Nd2Fe14B platelets and the carbon forms a thin surface passivation layer of the platelets, forming the stable Nd2Fe14BH x, x ≤ 5, hydride at room temperature. On heating in a calorimeter, the hydrogen desorbs off the sample with a well-defined endotherm between 370 and 425 K. An N2 gas atmosphere, if used during the heating, facilitates the H-desorption process with the modified kinetic parameters. For example, the enthalpy of the H-desorption ΔH and the related activation energy Ea have the measured values ΔH = 153 J/g and Ea = 58·2 kJ/mol in argon and ΔH = 256 J/g and Ea = 41·6 kJ/mol in N2. It is argued that N2 gas has a fast reaction with the H atoms desorbing off the thin sample platelets and forms NH3 gas with an instantaneous decrease of the total external gas pressure at the sample. This supports the fast desorption of H atoms in the sample with the modified desorption kinetics in N2 gas.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Nd2Fe14BHx, x ≤ 5; Hydrides; Hydrogen Intercalation; Hydrogen Desorption; Stable Metal Hydride; Thermal Desorption; Mechanical Attrition
ID Code:34868
Deposited On:16 Apr 2011 13:18
Last Modified:16 Apr 2011 13:18

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