Kinetic studies of hydrogen desorption in SmCo 2/17-type sintered magnets

Hydrogen is used as a processing tool in the formation of powder from SmCo 2/17-type sintered magnets for recycling purposes. Fully dense 2/17-type sintered magnets (based on the composition Sm(Co0.70Fe0.21Cu0.07Zr0.02)7.49 were subjected to hydrogen decrepitation (HD) and the degassing behaviour of the resulting hydrogen solution was then studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrogen desorption is shown by DSC as an endothermic peak in the temperature range 433–473 K. The kinetics of degassing was investigated by measuring the mass losses using TGA. Understanding the degassing mechanism is of greater importance in the magnet recycling industry as the full recovery of the magnetic properties of Sm2Co17-type sintered magnets is dependant on the amount of Hydrogen left in the powder after HD processing.