Vacuum Distillation, Zone Melting Joint Research Of The Preparation Of High Purity Indium

Indium is a rare and valuable metal. It has emerged as an important strategic metal that is extensively used in electrical industries for its excellent chemical, physical and mechanical performance. At present, the countries all over the world pay close attention to the development and application of indium. Indium has numerous industrial applications, and it is extensively used in the manufacture of liquid crystal displays, semiconductors, and metal organic compound etc. The demand for the preparation of ultra high purity (UHP) In has been primarily promoted by the recent developments in semiconductor industry. So, studying the craft of preparation ultra high purity indium not only can improve the benefits of indium, but also can promote the development in related industry.This dissertation reviewed the status, properties, applications, production of indium at home and abroad. The combination of vacuum distillation and zone refining was adopted to prepare ultra high purity indium from crude indium. The theories of vacuum distillation and the zone refining were analyzed. Regarding the unique advantage of vacuum distillation, we adopted the vacuum distillation to reduce the impurities which the vapor pressure were different from indium. Then the zone refining method was used to remove impurities which the equilibrium distribution coefficient k were different from indium. The5N indium was prepared successfully by this method, and the best craft conditions were obtained.The low-temperature distillation experiments are carried out to study the factor of distillation temperature, distillation time and material layer of thickness which influent the volatile of indium and impurities. The content of impurities which has low boiling point namely Cd、Zn、Tl、Pb in crude indium could be reduce to the standard of5N under the following conditions, distillation temperature about950℃, distillation time about60min and vacuum about5Pa. The direct rate of indium is91.37%.The high-temperature distillation experiments are carried out to study the influence of distillation temperature, distillation time on the impurities. The content of impurities which has high boiling point such as Cu、Fe、Sn、Ni in crude indium could be reduce to the standard of5N under the following conditions, distillation temperature about1075℃, distillation time about120min and vacuum about5Pa. The direct rate of indium is94.32%.The average content of impurity elements of crude indium(99.7%) has been reduced, by employing the two-step vacuum distillation method, to the extent of achieving5N(99.993) indium under the best conditions. And the separation coefficientβ, and activity coefficient yi of impurities are calculated according to the experiments to fill the inadequate dates of the thermodynamics.The zone refining experiments are carried out to study the influence of translation rate and pass times on redistributing of impurities in refined indium. The indium can be refined from99.9977%to99.9991%under the suitable condition:translation rate is3.5mm/min and pass times is10.