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Effect of Ga, Nb Addition on Disproportionation Kinetics of Nd-Fe-B Alloy

Journal of Magnetics, Volume 14, Number 4, 31 Dec 2009, Pages 150-154

H. W. Kwon *

(Pukyong National University), J. H. Yu (Korea Institute of Materials Science)

Abstract

The effect of Ga and, Nb addition on the kinetics and mechanism of the disproportionation of a Nd-Fe-B alloy were investigated by isothermal thermopiezic analysis (TPA) using Nd_12.5Fe_(81.1-(x+y))B_6.4Ga_xNb_y (x=0 and 0.3, y= 0 and 0.2) alloys. The addition of Ga and Nb retarded the disproportionation kinetics of the Nd-Fe-B alloy significantly, and increased the activation energy of the disproportionation reaction. The disproportionation kinetics of the Nd_12.5Fe_(81.1-(x+y))B_6.4Ga_xNb_y alloys measured under an initial hydrogen pressure of 0.02 MPa were fitted to a parabolic rate law. This suggested that during the disproportionation of Nd_12.5Fe_(81.1-(x+y))B_6.4Ga_xNb_y alloys with an initial hydrogen pressure of 0.02 MPa, a continuous disproportionation product is formed and the overall reaction rate is limited by the diffusion of hydrogen atoms (or ions).

Keywords: permanent magnets; HDDR; disproportionation kinetics; activation energy; TPA

DOI: 10.4283/JMAG.2009.14.4.150

Full Text: PDF

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