A Review of Slag Refining of Silicon Alloys

Thomas, Sridevi; Barati, Mansoor; Morita, Kazuki

doi:10.1007/s11837-020-04474-0

Cited by 10 publications

(3 citation statements)

References 37 publications

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“…[ 3 ] For the refining slag, its metallurgical function is mainly to desulfurize and deoxidize, absorb inclusions, maintain steel temperature, and prevent the steel from absorbing air. [ 4 ] For the mold flux used in continuous casting, its main function is to maintain temperature, prevent secondary oxidation, absorb inclusions, lubricate the casting, and control heat transfer. [ 5 ] The metallurgical function of slag is closely related to its physical properties such as viscosity [ 6 ] and surface tension, [ 7 ] which are essentially determined by its microscopic structure.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO₂–Al₂O₃–Li₂O System

Jiao,

Guo,

Chen

et al. 2023

steel research int.

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To further understand the structural behavior of Al3+ in the CaO‐SiO2‐Al2O3‐Li2O system melt, molecular dynamics simulations were used to analyze the microstructure of the melt under different basicity conditions. The results showed that the bond length of Al‐O was longer than that of Si‐O and was less stable than Si‐O. The stability of the [AlO4]5‐ tetrahedral structure was lower than that of the [SiO4]4‐ tetrahedral structure. With the increase of basicity, there was almost no effect on the Si‐O bond, but it caused the bond length of Al‐O to shorten and the bond length of Ca‐O to increase. At the same time, this led to the breakdown of complex aluminum‐oxygen ion clusters and the increase of the distance between O‐O atomic pairs. With the increase of basicity, the decrease in system energy promoted the gradual regularization of high‐coordinated Al ions under sufficient cation conditions, so that complex structures, such as O(Al,Al,Si) and O(Al,Al,Al), were transformed into simple structures, such as Al‐O‐Al, and the average value of the O‐Al‐O bond angle was closer to the ideal tetrahedral bond angle, and the proportion of tetrahedra increased. When the melt aggregation degree decreased, if two adjacent [AlO4]5‐ tetrahedra were connected by the same O, the distance between them would become larger, which also caused the average value of the Al‐O‐Al bond angle to gradually increase. The [SiO4]4‐ tetrahedra were more likely to be combined with [AlO4]5‐ tetrahedra. At the same time, the degree of decrease in Si‐O‐Al was not as great as that of Si‐O‐Si. CaO preferentially dissociates to provide O2‐, which in turn depolymerizes the Si‐O‐Si network structure to form non‐bridging oxygen Si‐O, and when basicity is sufficient, it will substantially depolymerize Si‐O‐Al to form Si‐O and Al‐O.This article is protected by copyright. All rights reserved.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO₂–Al₂O₃–Li₂O System

Jiao,

Guo,

Chen

et al. 2023

steel research int.

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“…Ultra-pure silicon (9 N) for electronic applications is produced by chemical vapor deposition techniques such as the Siemens method. Considering the high energy intensity of these processes and the difference in silicon purity required for application in microelectronics and in photovoltaics (6-7 N), developing processes for the mass production of silicon for photovoltaic applications has been the subject of much investigation [1][2][3][4][5]. Metallurgical techniques have been particularly focused on because of their scalability.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Analysis of Boron and Phosphorus Removal from Si-Fe Alloy by CaO-Al2O3-SiO2-Na2O Slag

Taposhe

Khajavi

2023

Processes

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A hybrid process of slag and solvent refining was used to remove boron and phosphorus from silicon. Quaternary slag of CaO-Al2O3-SiO2-Na2O was employed to remove boron (B) and phosphorus (P) from Si-20 wt% Fe alloy at 1300 °C. A slag-to-metal ratio of one was used at different reaction times. The mass transfer coefficient of B and P in the slag and alloy phases was calculated to determine the rate-limiting step. The mass transfer coefficients of B in the alloy and slag phases were 6.6 × 10−7 ms−1 and 2.8 × 10−7 ms−1, respectively. The mass transfer coefficients of P in the alloy and slag phases were determined to be 7.5 × 10−8 ms−1 and 3.5 × 10−7 ms−1, respectively. The rate-limiting stage of the slag–alloy reaction kinetics was mass transport in the liquid slag for B and mass transport in the alloy phase for P.

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“…To date, considerable work has been done to investigate the effect of slag properties on the B removal efficiency. A number of slag systems have been studied and reviewed, [7,[11][12][13][14] such as CaO-SiO 2 , [15][16][17][18][19] CaO-MgO-SiO 2 , [20][21][22] CaO-BaO-SiO 2 , [6,18] CaO-Na 2 O-SiO 2 , [5,23,24] CaO-ZnO-SiO 2 , CaO-Al 2 O 3 -SiO 2 , [25][26][27] CaO-MgO-Al 2 O 3 -SiO 2 , [28,29] CaO-SiO 2 -CaCl 2 , [30][31][32] CaO-SiO 2 -CaF 2 , [24,33,34] and so on. The B removal ability of different slags can be evaluated by the widely used B distribution coefficient (L B ) between the slag and metal in molten state:…”

Section: Introductionmentioning

confidence: 99%

Effects of La2O3 Addition into CaO-SiO2 Slag: Structural Evolution and Impurity Separation from Si-Sn Alloy

Zhu

Azarov

et al. 2021

Metall Mater Trans B

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Boron (B) and phosphorus (P) are the most problematic impurities to be removed in the production of solar-grade silicon by the metallurgical process. In this work, the distribution of B and P between CaO-(La2O3)-SiO2 slags and Si-10 mass pct Sn melt was experimentally studied. B distribution coefficient increased from 2.93 in binary CaO-SiO2 slag to 3.33 and 3.65 with 2 and 10 mass pct La2O3 additions, respectively. In the followed acid-leaching experiments, the slag-treated Si-Sn alloys exhibited higher B and P removal than that of the initial alloy without slag treatment. Molecular dynamics simulations were performed to study the effect of La2O3 addition on the slag structural and transport properties. A novel oxygen classification method was proposed to distinguish the different structural roles of La and Ca in the CaO-La2O3-SiO2 system. It was found that La3+ prefers to stay in the depolymerized region, mostly connects with 6-7 non-bridging oxygen, and requires a weak charge compensation with Ca2+. Possible silicothermic reduction was evaluated to discuss the slag chemistry and the mass transfer between slag and metal phase. A thermodynamic model was derived to theoretically study the alloying effect on impurity distribution in slag refining where positive interaction coefficient and high alloying concentration were found most beneficial to improve the impurity removal.

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A Review of Slag Refining of Silicon Alloys

Cited by 10 publications

References 37 publications

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO₂–Al₂O₃–Li₂O System

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO₂–Al₂O₃–Li₂O System

Kinetic Analysis of Boron and Phosphorus Removal from Si-Fe Alloy by CaO-Al2O3-SiO2-Na2O Slag

Effects of La2O3 Addition into CaO-SiO2 Slag: Structural Evolution and Impurity Separation from Si-Sn Alloy

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A Review of Slag Refining of Silicon Alloys

Cited by 10 publications

References 37 publications

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO2–Al2O3–Li2O System

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO2–Al2O3–Li2O System

Kinetic Analysis of Boron and Phosphorus Removal from Si-Fe Alloy by CaO-Al2O3-SiO2-Na2O Slag

Effects of La2O3 Addition into CaO-SiO2 Slag: Structural Evolution and Impurity Separation from Si-Sn Alloy

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Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO₂–Al₂O₃–Li₂O System

Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO₂–Al₂O₃–Li₂O System