Novel Alloys as Sintering Techniques for Permanent Magnets


The global permanent magnet market   size is expected to reach €30 billion by 2030 from the current €20 billion; it is attributed to the increasing use in the hybrid electric vehicle production and wind energy. For the HEV the expected increase is from 3 million cars to 26 million cars by 2030. 

Most of the current dominant (PMs) are intermetallic compounds containing rare earth elements e.g. NdPr or Sm and Co, both expensive and originating  mainly from either China or Congo. These natural elements from the periodic table have a fixed atomic radii, fixed valence electron configuration and specific electronegativity, parameters that are crucial for the formation of intermetallic compounds.  By creating artificial elements of the type of HEAs based on multicomponent rare-earth elements (RE-HEAs) and HEAs based on multicomponent transition metal elements (TM-HEAs), we have created a library of elements with tunable atomic radii, valence electron configuration and electronegativity. This approach enhances the opportunities for discovering novel permanent magnets 

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Powder metallurgy is a technology which involves considerable time and energy to convert the starting material to the powder form and shape required and then even more in compacting and producing a solid product and it is suitable for both alloys of the type Nd-Fe-B and Sm-Co.  But here is a new class of materials of the type Sm2Fe17N3 and NdFe12-xTxN~2-2.5,with exceptional magnetization, anisotropy and coercive field, which cannot be sintered with the techniques mentioned above, due to the fact that nitrogen escapes above 500-550 0 C. 

Thus new techniques are needed to sinter the nitride phases. We propose to use :

(a) a rapid heating-dynamic compaction technique, where a low temperature (300-450 0C) is combined with mechanical energy (multi compaction) to produce a dense sintered body with densities close or above 90-92 % and 

(b) molten salt shielded sintering (MS3) of oxidation prone materials and achieve sintering in air of the Nd-Fe-B and the nitride phases for the first time.

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