By maintaining a temperature difference between the top
and bottom parts of the reaction vessel, the Mg placed in the
bottom part of reaction vessel evaporates, and then condenses
in the toppart of the reaction vessel. The condensed liquid
Mg drips into the scrap in the iron crucible, and Nd in the
scrapalloy combines with liquid Mg. The Mg–Nd liquid
alloy thus formed is drained through the slit of the iron
crucible into the tantalum crucible placed at the bottom of the
reaction vessel. As the vapor pressure of Nd is extremely low,
c.a. 106 atm even at 1300 K5) (cf. pMg ¼ 0:73 atm @
1300 K), only Mg evaporates out of the Mg–Nd liquid alloy,
and Nd accumulates in the tantalum crucible. The evaporated
Mg once again, condenses at the topof the vessel, and acts as
an extraction medium. Thus Mg circulates in the reaction
vessel, and Nd is continuously extracted from the scrap. If the
scrap was simply dipped in molten Mg, the extraction of Nd
is hindered when the concentration of Nd in Mg–Nd alloy
increases. However, by using the circulating Mg method
employed in this study, fresh Mg is constantly supplied to the
scrapand extraction efficiency is expected to be high even
when a small amount of Mg is used.
By maintaining a temperature difference between the topand bottom parts of the reaction vessel, the Mg placed in thebottom part of reaction vessel evaporates, and then condensesin the toppart of the reaction vessel. The condensed liquidMg drips into the scrap in the iron crucible, and Nd in thescrapalloy combines with liquid Mg. The Mg–Nd liquidalloy thus formed is drained through the slit of the ironcrucible into the tantalum crucible placed at the bottom of thereaction vessel. As the vapor pressure of Nd is extremely low,c.a. 106 atm even at 1300 K5) (cf. pMg ¼ 0:73 atm @1300 K), only Mg evaporates out of the Mg–Nd liquid alloy,and Nd accumulates in the tantalum crucible. The evaporatedMg once again, condenses at the topof the vessel, and acts asan extraction medium. Thus Mg circulates in the reactionvessel, and Nd is continuously extracted from the scrap. If thescrap was simply dipped in molten Mg, the extraction of Ndis hindered when the concentration of Nd in Mg–Nd alloyincreases. However, by using the circulating Mg methodemployed in this study, fresh Mg is constantly supplied to thescrapand extraction efficiency is expected to be high evenwhen a small amount of Mg is used.
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