Title :
The kinetics of oxidation of Nd-Fe-B powders
Author :
Turek, Knysztof ; Liszkowski, Piotr ; Figiel, Henryk
Author_Institution :
Dept. of Solid State Phys., Univ. of Min. & Metall., Krakow, Poland
fDate :
11/1/1993 12:00:00 AM
Abstract :
The kinetics of oxidation of 2.5 μm Nd-Fe-B powder are studied at temperatures 20, 80, 100 and 115 °C. The powdered alloy compromises 62.5 wt.% Fe, 35 wt.% Nd and 1.3 wt.% B. The percentage of weight gain is measured and compared with X-ray spectra recorded after various periods of oxidation. Two stages of oxidation, with powder-like and exponential weight gain reaching a plateau, are distinguished at all temperatures. The effect of changes in phase composition on ferromagnetic properties due to oxidation are examined by a magnetic balance. On the basis of reported measurements, it is concluded that two processes contribute to oxidation of Nd-Fe-B in air, i.e., relatively quick, total oxidation of intergranular Nd and oxidation of Nd2 Fe14B (Φ) which stops at 12% level. The recognition of three products of the oxidation at X-ray spectra, Nd2O3, NdFeO3 and Fe3O4 , makes it possible to deduce a final phase composition
Keywords :
X-ray spectra; boron alloys; ferromagnetic properties of substances; iron alloys; magnetic properties of fine particles; neodymium alloys; oxidation; permanent magnets; powder metallurgy; reaction kinetics; surface chemistry; 100 degC; 115 degC; 2.5 micron; 20 degC; 80 degC; Fe3O4; Nd-Fe-B powders; Nd-Fe-B-O; Nd2O3; NdFeO3; X-ray spectra; exponential weight gain; ferromagnetic properties; intergranular Nd; kinetics; oxidation; phase composition; weight gain; Aging; Corrosion; Grain size; Kinetic theory; Magnetization; Neodymium; Oxidation; Physics; Powders; Temperature;
Journal_Title :
Magnetics, IEEE Transactions on
