The HDDR (hydrogenation disproportionation desorption and recombination) process can be employed in order to process highly anisotropic nanocrystalline Nd-Fe-B powder which can be aligned in a magnetic field and bonded with resin in order to prepare highly texture magnets [1]. Furthermore, the HD (hydrogen decrepitation) and HDDR methods are very promising routes for functional recycling of Nd-Fe-B magnets (see the Recycling section). The -HDDR process transforms single-crystalline powder particles (typically 50–100 μ m diameter) into polycrystalline particles of the same particle size but which have a grain size of ∼300 nm. This has a beneficial effect on the coercivity of resin bonded magnets produced from this powder.
The unique equipment available in our group allows careful control of the hydrogen pressure during disproportionation and recombination reactions. As the result, a strong biaxial texture can be achieved in the grains comprising each powder particle. This leads to a high remanence in resin bonded magnets produced from this powder as the powder is highly anisotropic and can therefore be easily aligned by a magnetic field.
[1] O. Gutfleisch, K. Güth, T. G. Woodcock, and L. Schultz, Recycling Used Nd-Fe-B Sintered Magnets via a Hydrogen-Based Route to Produce Anisotropic, Resin Bonded Magnets, Advanced Energy Materials, Volume 3, Issue 2 (2013) 151-155.
DOI: 10.1002/aenm.201200337
