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Indexed by:期刊论文

Date of Publication:2014-10-25

Journal:JOURNAL OF ALLOYS AND COMPOUNDS

Included Journals:SCIE、EI、Scopus

Volume:611

Page Number:267-272

ISSN No.:0925-8388

Key Words:Si purification; Impurity contamination; Si-Al alloy; Zn

Abstract:During solidification refining of Si, the eutectic alloy ultimately solidifies and becomes enriched with impurity elements according to their small segregation coefficients, which may contaminate the primary Si through the cooling process. Combined with analysis of the morphology of the primary Si, the contamination mechanism was verified for a Si-63.8 wt%Al alloy using various cooling rates in the final cooling stage (873-293 K). By a quenching treatment, the B content in Si was decreased from the initial content of 14.8 to 1.4 ppmw, which is quite close to the value predicted by Scheil's equation. Si cooled down at a rate of 1 K/min showed an increase in impurity content (e.g., B: 4.2 ppmw) owing to solid-state back-diffusion. In order to prevent such contamination, Zn was added to the Si-Al melt at 873 K, which decreased the eutectic temperature and separated Si from the alloy. A final Si amount of 94.1 wt% was recycled without further contamination. (C) 2014 Elsevier B.V. All rights reserved.