| 摘要 |
Ultra high purity materials, particularly metallic materials such as magnesium and similarly high volatility materials, are produced by a vacuum distillation method and apparatus to increase purity by approximately five hundred times in a single step. For example, magnesium purity, exclusive of zinc content, is increased from 99.95% to greater than 99.9999%. A distillation column is formed of a high purity (less than 10 ppm ash) graphite, and includes a crucible, a vertical condenser in which horizontal high purity graphite baffles are selectively located at a plurality of levels, for example at nine levels. The column is contained in a three-zone resistance furnace that is controlled to heat the crucible to evaporate the material, maintain the condenser immediately above the crucible to above the boiling point of the material, and maintain the portion of the column thereabove at below the boiling point of the material, preferably with the temperature gradually decreasing with the height of the column. The baffles are spaced along the condenser and are staggered to slow the vapors such that the high purity material reaches its condensation temperature and condenses on one or more selected ones of the baffles. The condenser is split so the baffles can be selectively placed and removed to remove the purified material. Caps at the top and bottom of the column hold the split condenser together.
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