Removal of Boron from Molten Silicon Using CaO–SiO2 Based Slags

Teixeira, Leandro Augusto Viana; Morita, Kazuki

doi:10.2355/isijinternational.49.783

Cited by 127 publications

(52 citation statements)

References 6 publications

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“…The activities and activity coefficients of SiO2 are calculated according to reaction (5) (6) 8) ............... (7) Here, aSiO 2 (9) 9) ......... (10) The relationship between the activities of SiO2 and molar fraction of BO1.5 is shown in Fig. 3.…”

Section: Activity and Activity Coefficients Of Sio2mentioning

confidence: 99%

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Relationship between Structure and Thermodynamic Properties in the CaO–SiO2–BO1.5 Slag System

et al. 2013

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To understand the relationship between thermodynamic properties and structures in the CaO-SiO2-BO1.5 slag system, the thermodynamic properties of BO1.5 and SiO2 were measured by a chemical equilibrium technique and the local structures of boron(B) and silicon(Si) were investigated by 11 B and 29Si magic angle spinning-nuclear magnetic resonance (MAS-NMR) measurements.Activity coefficients of BO1.5 increased with an increase in the BO1.5 content of the slag system. Activity coefficients of SiO2 increased with increasing BO1.5 content and decreased with increasing CaO/SiO2 ratio.By using 11 B MAS-NMR, the existence of two types of B sites was confirmed-three-and fourcoordinated B sites. The relative fraction of four-coordinated B increased with an increase in the BO1.5 content and decreased with an increase in the CaO/SiO2 ratio.29 Si MAS-NMR results revealed that bridging oxygen bonding to Si atoms increased with an increase in the BO1.5 content and decreased with decreasing CaO/SiO2 ratio. The number of non-bridging oxygen atoms bonded to the tetrahedrally coordinated Si atom (NBO/T) was calculated using 29 Si and 11 B MAS-NMR under specific assumptions. By comparing NBO/Ts calculated from these two methods, the number of non-bridging oxygen atoms bonded to three-coordinated B in the studied composition region was estimated to be one.Finally, by comparing the thermodynamic properties with the results of MAS-NMR measurements, it was found that the composition dependences on BO1.5 and SiO2 activity coefficients were dependent on changes in the local structure of B and Si with composition.KEY WORDS: local structure; thermodynamic properties; MAS-NMR; CaO-SiO2-BO1.5 slag system.

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Section: Activity and Activity Coefficients Of Sio2mentioning

confidence: 99%

“…Teixeira et al 1,2) investigated the thermodynamic properties of BO1.5 at 1 823 K in the CaO-SiO2-BO1.5 system in the low BO1.5 content region (<0.25 mass% BO1.5). Their results showed a strong dependence of CaO/SiO2 ratio on the activity coefficient of BO1.5 in the slag system.…”

Section: Introductionmentioning

confidence: 99%

Relationship between Structure and Thermodynamic Properties in the CaO–SiO2–BO1.5 Slag System

et al. 2013

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“…The purification of MG-Si through metallurgical routes such as directional solidification [1,2], slag refining [3][4][5], oxidation with plasma melting [6][7][8][9], and vacuum melting [10,11] has been investigated. The individual process has its own limitations and does not allow removal of all impurities.…”

Section: Introductionmentioning

confidence: 99%

Effect of solidification conditions on the silicon growth and refining using Si–Sn melt

Lei

Yoshikawa

et al. 2015

Journal of Crystal Growth

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Effect of solidification conditions on the silicon growth and refining using si-Sn melt, Journal of Crystal Growth, http://dx.doi.org/10.1016/j. jcrysgro. 2015.08.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Institute of Industrial Science, The University of Tokyo, Tokyo, Japan. AbstractThe solidification refining of Si using a Si-Sn solvent was investigated under various cooling conditions: (1) slow cooling, (2) slow cooling with electromagnetic stirring, and (3) directional solidification with the aim of developing a novel low-cost route for solar-grade Si production. The separation efficiency of refined Si achieved by combining slow cooling and electromagnetic stirring was much higher than that achieved using directional solidification; in addition, the purification efficiency of the refined Si in both methods was similar. The separation mechanism of refined Si from a Si-Sn melt is also discussed. Purification testing of the refined Si revealed that more than 96% of the metallic impurities, approximately 60% B, and over 70% P were removed.

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“…During metallurgical grade Si production, oxidizing treatment is used to remove gangue components as slags from Si melts that are obtained by quartz reduction in the arc furnace. Slag treatment using calcium-oxide-based slags has been researched to remove boron and phosphorus from Si, and is aimed at solar-grade Si production [1][2][3][4] . Because magnesium oxide and calcium oxide are major components of slag in both cases, the incorporation of magnesium (Mg) and calcium (Ca) into molten Si is thermodynamically inevitable 2,3,5,6) and their behavior during solidi cation must be understood.…”

Section: Introductionmentioning

confidence: 99%

Reassessment of Solid Solubilities and Thermodynamic Properties of Magnesium and Calcium in Silicon

Kawanishi

Yoshikawa

2017

Mater. Trans.

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To obtain fundamental knowledge on the behavior of magnesium (Mg) and calcium (Ca) in solid silicon (Si) during solidi cation, the solid solubilities of Mg and Ca in Si were reinvestigated by temperature-gradient zone melting method. Solubilities were measured to be 0.0016-0.0041 mol% for Mg and 0.0006-0.0021 mol% for Ca at 1373-1623 K. The excess Gibbs energies of Mg and Ca in solid Si were determined from their solid solubilities as follows:RT ln γ

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Removal of Boron from Molten Silicon Using CaO–SiO2 Based Slags

Cited by 127 publications

References 6 publications

Relationship between Structure and Thermodynamic Properties in the CaO–SiO2–BO1.5 Slag System

Relationship between Structure and Thermodynamic Properties in the CaO–SiO2–BO1.5 Slag System

Effect of solidification conditions on the silicon growth and refining using Si–Sn melt

Reassessment of Solid Solubilities and Thermodynamic Properties of Magnesium and Calcium in Silicon

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