| 摘要 |
<PICT:0894132/III/1> Silicon is purified by forming a molten alloy with aluminium, treating the molten alloy with 1-2% of a flux comprising sodium fluoride, cooling so as to form a sponge of large crystals of purified silicon, and separating the crystals. The flux may consist of 80% of sodium chloride and 20% of cryolite. The aluminium may contain silicon, zinc, tin, titanium and lead. The presence of 0,1-2% of lead is advantageous. The rate of cooling may be less than 30 DEG C. per hour. The degree of cooling may be proportional to the time of cooling or the cube thereof. Crystallization may take place in a crucible 1 having an outlet orifice 2, a plug 3, a vibrator 5, and heating element 7. There may be a 5 DEG -10 DEG C. increase in temperature from the bottom to the top of the crucible in order to control crystal formation. Crystallization may be repeated one or more times with aluminium of increasing purity, mother liquor from one treatment being recycled to a preceding treatment. The silicon crystals may be finally purified by physical treatment (e.g. abrasion or floatation) and/or chemical treatment (e.g. with aqua regia). Mother liquor from the crystallization process may be used in the production of an aluminium alloy. Examples are given. |
