Možnosti recyklace odpadních magnetů na bázi Nd-Fe-B

Abstract

The recycling of waste magnets based on Nd-Fe-B in order to recover permanent magnets was performed by the "magnet to magnet" method, which applied the process of hydrogen decrepitation and power blending technology. The hydrogen decrepitation was carried out at a temperature of 250 ° C and at a pressure of approximately 0.1 MPa, when the resulting powder was mixed with neodymium hydride NdH2, fine milled in a vibratory ball mill in isopropyl alcohol medium and pressed in a transverse magnetic field. The compacted magnet blanks were sintered at 1118 ° C for 2 hours followed by heat treatment. Based on the results, recycled magnets showed better coercivity and remanence than the initial waste magnets, which were associated with the diffusion of Dy and the formation of a "core-shell" structure of Nd (R)2Fe14B based grains. Another method used to process waste magnets was the strip casting method, which yielded a base alloy applicable in the production of new magnets. Corrosion resistance of selected recycled magnets was performed by electrochemical testing, where the values of corrosion potential Ecor, polarization resistance Rp, corrosion rate (rc) and resistance to pitting corrosion were recorded with polarization curve recording and determination of conventional pitting potential (Ep) and repassivation (Er). Corrosion resistance was also tested by salt spray corrosion test, to which the samples were exposed for 80 h. In this case, the results were evaluated on the basis of the weight gain of the tested samples.