Mass spectrometer studies of hydrogen desorption from hydrided NdFeB

The desorption of hydrogen from NdFeB powder and unmilled material produced using hydrogen decrepitation as a premilling technique was investigated using a mass spectrometer to monitor the hydrogen partial pressure in the system as the sample was heated under vacuum from room temperature to ~1000°C. A comparison was made between powder exposed to the atmosphere for 10 min and powder exposed for one month. There was found to be a reduction in the amount of hydrogen desorbed from the Nd-rich grain boundary phases, and there was a change in the shape of the desorption peak from the Nd₂Fe₁₄B phase as the level of oxidation increased. Studies were also carried out on alloy hydrided at room temperature in situ, and these showed a variability in the amount of hydrogen desorbed from the Nd-rich grain boundary phases