PURPOSE: To easily remove impurities in a metal silicon powder and to obtain a high-quality metal silicon powder by stirring and washing a metal silicon powder slurry at specified temp. with hydrofluoric acid of specified concn. and mineral acid except for nitric acid.
CONSTITUTION: The starting source material is a metal silicon powder obtd. by pulverizing metal silicon blocks and a metal silicon powder obtd. by removing copper from a metal silicon powder containing waste catalyst of copper which is discharged from synthesizing process of silane. This source material is stirred and washed with an acid soln. comprising 0.25-2.5 N hydrofluoric acid and 1-10 N mineral acid except for nitric acid. The metal silicon powder slurry is maintained at 30-90°C while stirring and washing. The slurry after washed with acid is filtered, washed with water and then with a hydrophilic org. solvent of low boiling point, and dried at 30-80°C. Thereby, impurities such as iron, oxygen, Ca, Al, etc., can be easily removed from the metal silicon powder and the metal silicon powder of ≥98wt.% Si quality can be obtd. at low cost.
TAKAHASHI HIROSHI
MAEKAWARA HIDEAKI
ORIMO MITSUMORI
