Aluminothermic Reduction of Quartz Sand
The exothermic reaction of quartz with aluminum is a promising way to make high purity silicon on a large scale — according to 3 Si02 + 4 Al ➙ 2 Al203 + 3 Si A suitable technical process on this basis requires liquid phases of both oxidic and metallic nature acting as solvents for the reaction products. The two liquid and immiscible systems are represented by an Al-Si alloy and an Al2S3 -Al203 -Si02 slag system. The reaction between them is controlled by an adjustable stirring system which is placed at or close to the phase boundary. Silicon is obtained in form of platelets. Their special structure is described in detail. Typical impurity levels are lower than 10 ppma total (except Al). Prior to further refining the product is milled and leached.
KeywordsCrystallization Quartz Hexagonal ECSC
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