Leaching behavior of impurities in Ca-alloyed metallurgical grade silicon

Hydrometallurgical Purification of Metallurgical Grade Silicon with Hydrogen Peroxide in Hydrofluoric Acid

“…The extractions of Fe remaining constant may result from high sensitivity of Fe-containing phases to HF. 4,23,27 No significant differences in the purification results were found between silicon treated in 1.0 mol•L −1 HF acid solution and in 2.0 mol•L −1 HF acid solution, suggesting that less concentration of HF will be satisfactory.…”

“…The operating procedures of acid etching were described in detail in our previous study. 23 2.3. Characterization.…”

“…Then some comparisons were done to reveal the morphology evolution of MG-Si before and after acid etching. The operating procedures of acid etching were described in detail in our previous study …”

New Insights into Silicon Purification by Alloying–Leaching Refining: A Comparative Study of Mg–Si, Ca–Si, and Ca–Mg–Si Systems

“…Even though it has been theoretically and experimentally confirmed that P tends to segregate along Si grain boundaries, its segregation coefficient ( k p = 0.35) is still relatively high compared to metallic impurities, which is usually less than 10 –3 . To further improve the extraction efficiency of P and other impurities, considerable attention has been paid to redistribute impurities by adding alloying elements as impurity getters such as calcium (Ca), − magnesium (Mg), − titanium (Ti), aluminum (Al), − copper (Cu), − tin (Sn), , iron (Fe), − and nickel (Ni) . The widely known solvent refining usually involves alloying by Al, Sn, Cu, and Fe with a large amount of metal addition (around or more than 50 wt %).…”

“…Shimpo et al measured the interaction coefficient of Ca and P in the Ca–Si–P system and observed the formation of Ca 3 P 2 along the Si grain boundary. It was also reported that efficient P removal could be achieved by altering the Ca alloying concentration, cooling rate, and leaching conditions. − Mg is a relatively new alloying impurity getter proposed by the NTNU team in recent years, − and more knowledge about Mg is needed, in particular for comparison with the Ca–Si alloying–leaching system. In addition, according to the Zintl–Klemm concept, the mixing of Ca and Mg in Si may show a pronounced variation of the electronic structure compared to the binary silicide as a result of unbalanced valence electron transfer.…”