Critical hydrogen pressure for HDDR-formed NdFeB powder

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H2 pressure dependence degree of anisotropy DOA (black circle) and coercivity Hci, (red square) in HDDR Nd14Fe77.9B7Al1Cu0.1 magnetic powder. DOA is defined as the normalized difference between the remanence at aligned state and that at non-aligned state for the same sample.
H2 pressure dependence degree of anisotropy DOA (black circle) and coercivity Hci, (red square) in HDDR Nd14Fe77.9B7Al1Cu0.1 magnetic powder. DOA is defined as the normalized difference between the remanence at aligned state and that at non-aligned state for the same sample.  

CMI researchers at Ames Laboratory and Oak Ridge National Laboratory conducted the research for this highlight

Achievement
We have discovered a critical hydrogen pressure to form strong crystal texture in Nd-Fe-B during the Hydrogenation Disproportionation Desorption and Recombination (HDDR) process. To our knowledge, such a critical pressure was previously unknown.

Significance and impact

  • This finding significantly aids the preparation of the high-performance anisotropic Nd-Fe-B magnet powder central to the U.S. bonded magnet industry, including additive manufacturing. 
  • Anisotropic magnet powders obtained via the HDDR route will yield higher energy density bonded magnets (15 – 25 MGOe) with smaller volumes of magnet powder, relative to isotropic powders.
  • Bonded Nd-Fe-B is the primary type of Nd-Fe-B magnet produced in North America; hence, this finding strongly supports the U.S. magnet industry. 

Next steps
Improve magnetic performance via enhanced anisotropy by introducing additional parameters, such as magnetic field during the HDDR process.