Hydrogen absorption of NdDyFeCoNbCuB sintered magnets

Hydrogen absorption and desorption characteristics for high coercivity NdDyFeCoNbCuB sintered bulk magnets were studied, by differential scanning calorimetry (DSC) measurement and hydrogenation kinetics measurement. The DSC measurements showed that hydrogenation of Nd-rich phase occurred in the temperature range of 40-185 °C, hydrogenation of the tetragonal (Φ) phase in the temperature range of 185-220 °C, as well as the disproportionation of the Φ phase that occurred in a broad temperature range from around 500 to 800 °C. The hydrogenation kinetics measurements indicated that hydrogen absorption of the bulk magnets at 50 °C absorbed more hydrogen than at 150 °C, although this procedure was slower at 50 °C than at 150 °C. This phenomenon was discussed by means of pressure-concentration-temperature (p-c-T) diagrams.