| 摘要 |
PURPOSE:To obtain the titled target contg. extremely reduced amounts of alkali metals, radioactive elements, transition metals and high m.p. metals by crystallizing a Ta compound by fractional crystallization, reducing the resulting crystals to form high purity Ta powder, sintering and melting the powder, forming a metallic Ta ingot and working it. CONSTITUTION:Metallic Ta or Ta2O5 is dissolved in hydrofluoric acid or a mixed acid contg. hydrofluoric acid to prepare an aqueous soln. contg. Ta, an aqueous soln. contg. K ions is added and K2TaF7 crystals are deposited to remove radioactive elements and high m.p. metals. The crystals are recovered and reduced with Na to form metallic Ta powder and a product contg. KF and NaF. The Ta powder is recovered by washing, compacted, sintered and melted to remove alkali metals and transition metals. The molten metal is formed into an ingot and the resulting metallic Ta ingot is worked to a desired shape. Thus, the titled target contg. <=50ppb alkali metals, <=5ppb radioactive elements, <=3ppm transition metals and <=3ppm high m.p. metals can be obtd.
|
