Abstract
The removal of boron from metallurgical-grade silicon to obtain solar-grade silicon using an alloy-refining method has received widespread attention. To overcome the disadvantages of low recycling efficiency and high cost, a novel approach for boron removal from silicon using CrMnFeNiMe high-entropy alloys (HEAs) has been proposed. A new boron removal recycling process including phase segregation between silicon and HEA, boron transition and enrichment from silicon to HEA, and hydrometallurgy treatment of primary Si-HEA solvent recycling was introduced. This was based on the measurement of the Si-HEA pseudo-phase diagram, activity coefficients of elements in the HEA, and the diffusion coefficient of boron in HEAs. The results proved that HEAs have a higher boron removal ability in silicon refining. This is because the activity coefficients of boron in Si-HEA melt are significantly lower than those in silicon or other binary solvent systems. Furthermore, because the diffusion coefficient is significantly higher under the same circumstances, the boron removal efficiency (EB) reached 95.97% in the first cycle and the primary silicon enrichment rate (ωSi) reached 97.4% owing to HEA-based refining. The hardness of the HEA-based solvent can be increased, and the HEA can be recycled for the fabrication of key parts when boron is saturated. In the recycling process, the yield of silicon was more than 90%. This method has the potential to improve the boron removal efficiency and reduce the cost of preparing high-purity silicon.
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