A study on the impact of surface and bulk oxidation on the recyclability of NdFeB magnets

Farr, Matthew (2013). A study on the impact of surface and bulk oxidation on the recyclability of NdFeB magnets. University of Birmingham. M.Res.

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Abstract

Oxidation of NdFeB can cause problems when attempting to hydrogen process scrap magnetic material; both with the initiation of hydrogen decrepitation at the surface of the material as well as having a detrimental effect on the mechanical and magnetic properties of the final recycled magnet [Jacobson, 1987; Meakin, 2013]. The aims of this project were to investigate and characterise the surface/near surface oxidation behaviour of bulk NdFeB magnets, in air, at room temperature as well as attempting to track the oxygen content throughout the re-sintering process developed at the University of Birmingham. Surface oxidation appeared to be exclusive to the Nd-rich triple junctions on the surface of the material, which is unlike higher temperature oxidation observed on sintered NdFeB magnets [Li, 2002]. Alloying additions of Dy and Co were also shown to increase the resistance to oxidation of NdFeB magnets. SIMS analysis showed that oxygen was concentrated in the grain boundary phase in the near surface. The oxygen content was shown to increase almost linearly throughout the recycling process outlined in this report with an overall increase of ~1100-1200 ppm, which is much smaller than that observed for commercial primary production of sintered NdFeB magnets.

Type of Work:

Thesis (Masters by Research > M.Res.)

Award Type:

Masters by Research > M.Res.

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