The effects of the hydrogenation-disproportionation-desorption-recombination (HDDR) processing conditions on the microstructure and magnetic properties of NdFeB powders prepared from recycling sintered N42 grade magnets were evaluated. Temperatures below 840 oC and above 900 oC are deleterious to HDDR powders’ properties. The hydrogen pressure, ranging from 60 to 135 kPa, has a major influence on the remanence compared to that on the intrinsic coercivity. The best magnetic properties (Jr = 0.58 T and μ0Hc = 1.15 T) were obtained with Trecomb = 860 °C, PH2 = 135 kPa, and trecomb = 330 s. Such coercivity value corresponds to 93% of the starting material, not achieved yet by optimizing the HDDR process and without using Dy.
A magnetic setup able to characterize magnetic materials in distinct shapes has been implemented using the force magnetometry principle. It consists of a combination of two toroidal magnets, which move along their symmetric axis, and an analytical balance that supports a still sample. Based on the nominal features of the setup employed, the prototype presents a resolution ranging from 13 to 21 nAm 2 , similar to a vibrating sample magnetometer. The feasibility of the system is demonstrated using powder samples. The magnetic field range of the developed device is a function of physical and mechanical features of the magnetic assembly.
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