A process for inducing alloy directional solidification growth and strengthening alloy refining process by direct current electric field

Abstract

The invention discloses a technology for inducing alloy directional solidification growth and reinforcing an alloy refining process by an direct current electric field. The technology comprises the following steps: heating a Si-M mother alloy to a corresponding liquidus temperature in order to obtain a Si-M alloy melt, introducing the direct current electric field to the Si-M alloy melt to realize directional movement of silicon atoms in the Si-M alloy melt, enrichment at the bottom of a graphite crucible and formation of a supersaturated area in order to achieve nucleation and growth on a crystal silicon substrate; continuously adding raw material silicon from the top of the graphite crucible in the growth process in order to realize continuous growth of the crystalline silicon; and powering off a heat source after the growth ends to cool and solidify, and powering off a direct current power supply. The technology realizes a highly-accurate directional growth mode, effectively reduces the refining temperature and the fractional condensation coefficients of various impurities, reduces energy consumption, enhances the purifying effect, makes different impurities be afresh distributed under the action of an electric field, and allows silicon to be solidified and precipitated and the silicon atoms to be continuously provided through continuously adding the raw material silicon in order to realize continuous growth of silicon.

Description

technical field [0001] The invention belongs to the technical field of growing and purifying polysilicon by metallurgical technology, and in particular relates to a technique for inducing directional solidification growth of an alloy by a DC electric field and strengthening the refining process of the alloy. Background technique [0002] Metallurgy is a proprietary purification process proposed for the manufacture of solar-grade polysilicon. This method uses metallurgical grade silicon (MG-Si) as the raw material, and optimizes methods such as pickling, slagging and refining, vacuum smelting, energy beam smelting, solidification and refining based on the differences in the physical and chemical properties of impurities and silicon to gradually reduce silicon Medium impurity content to achieve high selectivity and gradient separation of impurities, and finally prepare solar-grade silicon materials; [0003] The alloy solidification and refining method was first proposed by O...

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Problems solved by technology

[0005] Although the purification technology currently researched can purify MG-Si to a certain effect, the refining temperature is lowered, and the energy consumption is also greatly reduced, but due to the introduction of solvent metal, the final product of solidification and refining is alloy phase and primary crystal phase, and there must be Si and Al form a eutectic phase, resulting in limited precipitation of the primary crystal phase. At the same time, the inclusion pollution of the primary silicon by the solvent metal Al is inevitable, which limits the effective separation of the primary silicon and the alloy, makes the subsequent separation procedures cumbersome, and increases production. cost

At the same time, the traditional directional solidification process is controlled by the temperature field. Due to the limitation of the actual experimental equipment, it is difficult to ensure accurate temperature, so that the ideal directional solidification growth effect cannot be achieved.

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