Zone Refining을 이용한 네오디뮴 정제과정에서의 불순물 거동 분석

Abstract

Zone refining, using a locally-melted zone by high-frequency induction heating, was utilized to purify neodymium (Nd) metal. The traveling rate of the molten zone was set as a parameter during zone refining process. The purification efficiency for each impurity (Al, Cu, Fe, Mn, Se, Ti) in the Nd specimen was analyzed using ICP, and experimental results were compared with the numerical zone refining model. In addition, the effect of the impurity migration on the hardness of Nd was investigated. The result showed that a slower traveling rate of the molten zone was more effective for purification. The distribution coefficient, k, of Al and Mn was 0.87, and the k values of Cu, Fe, and Ti were 0.82, 0.83 and 0.68, respectively. These elements were effective for purification of Nd by zone refining. On the other hand, the k value of Se was greater than 1, thus Se migrated in the same direction as the molten zone traveling. The obtained k values of impurities can be used as guidelines for the purification of Nd by zone refining. The trend of hardness with respect to location was similar to the concentration distribution: low at the starting region and high at the end of specimen for the molten zone traveling. The redistribution of impurities resulted from the formation of the eutectic phase during freezing, and the hardness was proportional to the amount of eutectic phase formation. Therefore, the purification efficiency of the zone-refined Nd can be indirectly estimated by measuring the hardness. †(Received October 18, 2013)