Purification of Indium by Zone Refining

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  • Inの帯融精製について
  • In ノ タイユウセイセイ ニ ツイテ

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Abstract

For the zone refining of indium, tow methods were employed: The one is the ordinary method and the other involves a forced cooling of unmolten parts of the ingot bar by setting up two water-cooled copper tubings on both sides of the zone heater. In both cases, spectrographic and polarographic analyses showed clearly that tin, copper, cadmium, magnesium and thallium segregate at the finishing end of the ingot bar, while lead segregates at the beginning end. The recrystallization structure showed also the effect of purification by the zone refining. A slow rate of zone travelling of 17 mm/hr was more efficient in removing impurities than a faster rate of 69 mm/hr. In comparison of the two methods, the method involving the forced cooling was found preferable in consideration of refining efficiency to the ordinary non-cooling method. The reason may be that the forced cooling of both sides of the molten zone keeps a constant zone length throughout the travelling as well as maintains a higher temperature of the molten zone than in the case of ordinary method so as to give a higher diffusivity of impurities in the zone as a result of a steeper temperature gradient at the liquid-solid interfaces.

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