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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.42  No.12 (2001)  >  pp.2492-2498

MATERIALS TRANSACTIONS
<<Previous article Vol.42  No.12 (2001)   pp.2492 - 2498 Next article>>

Recycling of Rare Earth Magnet Scraps: Part II Oxygen Removal by Calcium

Ryosuke O. Suzuki1), Akihiko Saguchi1), Wataru Takahashi2), Takashi Yagura1) and Katsutoshi Ono1)
1) Department of Energy Science and Technology, Kyoto University
2) Electronics Materials & Science Research Department, Electronics Engineering Laboratories, Sumitomo Metal Industries, Ltd.


Powder scraps of neodymium-iron-boron permanent magnet were deoxidized by using calcium vapor, liquid or CaCl2 melt at 1223–1273 K . Because the scraps react with the acidic solutions during leaching of the byproduct CaO, the methods for removal of the excess amount of Ca and CaO were studied. When pH was controlled at about 8 during several times leaching, the dissolution of rare earth elements could be minimized. Ca vapor deoxidation could not supply enough amount of Ca through CaO layer. When a large amount of CaCl2 was added, the dissolution rate of CaO into the aqueous solution became faster, but some amounts of rare earth components were lost. The deoxidation by Ca liquid and 5 mass%CaCl2 and the subsequent leaching in distilled water with pH>8 gave the better result so that oxygen, even in heavily oxidized scraps, could be lowered to 0.7 mass%.


Keyword:
recycling of magnet, magnet scraps, thermodynamics of deoxidation, calcium deoxidation, calcium halide flux deoxidation, calcium oxide removal

Received: July 03, 2001
Accepted: November 08, 2001 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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