Silicon Refining by Growing Crystallites in a Hypereutectic Melt of Aluminum with Silicon

Abstract

Silicon is an essential chemical element that plays a very important role in life support on our planet. There is no single area of life on Earth where this most common chemical element is not present; its content is 27-30% of the mass of the Earth's crust. The most common form of its presence in the earth's crust is silicon dioxide, that is, silica. Silica is the main raw material source for semiconductor silicon for modern electrical engineering (production of diodes, transistors, photocells, and integrated circuits). Silicon is widely used in special materials science (alloying special steels, refining melts, and producing aluminum-silicon alloys (silumins). Reducing the cost of high-purity silicon can be achieved by reducing the temperature of the refining process of technical silicon. This scientific work examines the implementation of refining silicon in eutectic silicon melts with aluminum. Crystallization of silicon in hypereutectic melts below the liquidus temperature of the Si-Al phase equilibrium system occurs through the formation of silicon crystallization nuclei from clusters on the surface of the crystallizer - electrodes (rods) made of silicon with a temperature, which is below the temperature of the hypereutectic melt liquidus. The article describes methods for obtaining high-purity silicon and provides scientific justification for the implementation of such a task. The proposed method for producing high-purity silicon has so far been little studied and is of scientific and economic interest, since it can be carried out at relatively low temperatures, for example below 900°C. An important feature of eutectic melts is the stoichiometric content of components, which was the reason for the assumption of the molecular structure of eutectic melts. Eutectic molecules are, in our opinion, compounds of silicon and aluminum clusters.