Evidence of a quantitative relationship between the degree of hydrogen intercalation and the coercivity of the two permanent magnet alloys Nd[sub 2]Fe[sub 14]B and Nd[sub 2]Fe[sub 11]Co[sub 3]B
- LMGP-URA CNRS, Saint Martin d'Heres (France)
Nd[sub 2]Fe[sub 14]BH[sub x] micron-size loose particles have been synthesized through the well known oxide reduction-diffusion (ORD) technique. When excess Ca is used as reducing agent, an exothermic reaction is observed by washing under water, with the production of native hydrogen that diffuses in the interstitial sites of the alloy. Depending on the experimental conditions, different contents of hydrogen intercalation have been observed, with x ranging from x[approximately]0 to x[approximately]4--5. Cell parameters were observed quickly increasing with hydrogen uptake, resulting in a drastic and regular decrease of the coercivity. In order to understand the relation between the coercivity and the content of hydrogen uptake, 2 to 4 [mu]m size powders or a highly coercive Nd[sub 2]Fe[sub 14]B industrial alloy have been submitted to a native hydrogen environment obtained through different chemical conditions. A very reliable relationship has been established between the cell parameters (and thus the content or interstitial hydrogen) and the coercivity or the alloy particles. The degradation of the coercivity of industrial magnets submitted to moisture corrosion could well result from the formation of low coercive layers -- with a high hydrogen content -- at the surface of grains, resulting in the possibility to initiate reverse nucleus domains.
- OSTI ID:
- 6895652
- Report Number(s):
- CONF-930416-; CODEN: IEMGAQ
- Journal Information:
- IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers); (United States), Vol. 29:6Pt1; Conference: INTERMAG '93: international magnetics conference, Stockholm (Sweden), 13-16 Apr 1993; ISSN 0018-9464
- Country of Publication:
- United States
- Language:
- English
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BORON ALLOYS
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METALLURGICAL EFFECTS
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HYDROGEN ADDITIONS
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MAGNETIC MATERIALS
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360104* - Metals & Alloys- Physical Properties