1996 Fiscal Year Final Research Report Summary
Production of High Purity Rare Earth Metals by the Continuous Processing Composed of Calciothermic Reduction and Vacuum Melting.
| Project/Area Number |
07455299
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | Nagoya University |
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Principal Investigator |
YAMAUCHI Chikabumi School of Engineering, Nagoya University Professor, 工学部, 教授 (40115647)
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| Co-Investigator(Kenkyū-buntansha) |
FUJISAWA Tohiharu School of Engineering, Nagoya University Professor, 工学部, 教授 (20115629)
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| Project Period (FY) |
1995 – 1996
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| Keywords | reduction / vacuum melting / rare earth metals / neodymium / neodymium fluoride / calcium / oxygen / oxygen analysis |
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| Research Abstract |
1. Preliminary Experiments
DTA revealed calciothermic reduction of NdF_3 starts at 1093 K.The phase diagram of the NdF_3-CaF_2 system was estimated by thermal analysis. The analytical procedures of oxygen content in neodymium using the device in our laboratory were also studied as a function of flux and temperature.
2. Optimization of Calciothermic Reduction of NdF_3
Calciothermic reduction of NdF_3 were studied for various temperatures, reaction periods, and quantities of calcium addition. Optimum conditions for obtaining a lump of neodymium were considered not only based on purity and reduction ratio but also separation between slag and metal, and that between slag and crucible.
3. Optimization of Vacuum Melting
Using commercially produced neodymium and calcium, model experiments of vacuum melting were conducted for various temperatures, reaction periods, initial impurity contents, and stirring condition. Optimum conditions were discussed not only for the removal of volatile impurities but also precipitation of crucible material dissolved during the calciothermic reduction and the vacuum melting.
4. Optimization of the Continuous Processing
On the basis of the previous experimental results, optimum conditions for the continuous processing were determined as follows : calciothermic reduction is carried out for 0.9 ks at 1750 K by the addition of calcium 1.2 times as much as the stoichiometric moles : and vacuum melting is carried out at first for 1.2 ks at 1500 K with stirring, then, by decreasing temperature down to just above the melting point of neodymium, for 3.6ks.
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