Enhancing impurities removal from Si by controlling crystal growth in directional solidification refining with Al–Si alloy

Qian, Guoyu; Sun, Liyuan; Chen, Hang; Wang, Zhi; Wei, Kuixian; Ma, Wenhui

doi:10.1016/j.jallcom.2019.153300

Cited by 21 publications

(6 citation statements)

References 37 publications

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“…The occurrence of transient interfacial phenomena related to the mass transfer of calcium has been observed [20] . Qian et al studied the mechanism of Si crystal growth and solid-liquid interface migration and its correlation with impurities removal in directional solidi cation re ning with Al-Si alloy [21] . Some studies also show that industrial silicon slag contains a certain proportion of silicate and glass phase, which is a better raw material for porous microcrystalline glass [22] .…”

Section: Introductionmentioning

confidence: 99%

Study on the Composition and Interface of Waste Silicon Slag After Secondary Refining

Qiao

Liang

Zhao

et al. 2021

Silicon

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Silicon slag is a secondary re ning byproduct from industrial silicon. The content of industrial silicon in silicon slag is about 20% , which has extremely high economic value. To better achieve the recovery and reuse of industrial silicon slag, the morphology of industrial silicon slag, the occurrence state of elements and especially the interfacial structure between silicon and slag were deeply studied in this paper. The macro and micro morphology and surface composition distribution of the silicon slag were observed by microscope, SEM-EDS and Raman spectroscopy. The phase and composition of the silicon slag were analyzed by XRF and XRD. The results showed that the purity of silicon particles in silicon slag is high up to 99% . The size and shape of silicon in silicon slag were quite different. The interface between silicon and slag is clear and there is no obvious two-phase transition zone, which is conducive to the recycling of silicon. The crushing behavior of silicon slag under different pressure was investigated. These results provide a theoretical basis for further crushing silicon slag and recovering silicon particles. When silicon slag was crushed under certain pressure, the fracture surface of large-size silicon was mostly siliconsilicon interface. Therefore, in order to realize the complete dissociation of slag and silicon, the size of the crushing particle needs to be small enough. In this paper, the physical and chemical properties of industrial silicon slag were studied, which provides a theoretical basis for the e cient separation and recovery of silicon in the slag.

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Section: Introductionmentioning

confidence: 99%

Study on the Composition and Interface of Waste Silicon Slag After Secondary Refining

Qiao

Liang

Zhao

et al. 2021

Silicon

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“…For example, the partition coefficient of B and P in the slag refining process is usually less than 10, 10,11 solidification segregation process is close to 1. 12 In addition, when the impurity concentration drops to a certain level, the impurity transfer and reaction driving force are small; thus, the separation efficiency would be significantly reduced. 13 Therefore, ensuring the simultaneous and efficient removal of lowconcentration impurities is the key to upgrading metallurgical purification technology.…”

Section: Introductionmentioning

confidence: 99%

“…The common characteristics of these metal elements are that they have a very small separation coefficient (10 −4 −10 −8 ) in Si, which is conducive to the efficient separation of the medium. 12,16 The second of these metal elements in the electron configuration are more easy to lose one electron to form a variable valence state and has not filled the valence shell d orbitals. These metals are easy to interact with Si, B, and P impurities or form compounds with characteristic chemical structures (such as coordination bonds) to change the activity or phase structure of impurity elements so as to achieve the purpose of chemical reconstruction of impurities.…”

Section: Introductionmentioning

confidence: 99%

“…Two kinds of impurities often come from the contamination of electroplating solution containing pyrophosphate on the diamond wire saw or B/P addition of P/N batteries, which limits the use of recycled Si powder as Si feedstock. − One of the biggest difficulties in the preparation of SoG-Si is how to deeply remove traces of B and P. The small separation coefficient is an important reason for the difficulty in deep separation of the two impurities. For example, the partition coefficient of B and P in the slag refining process is usually less than 10, , and the segregation coefficient of B and P in the solidification segregation process is close to 1 . In addition, when the impurity concentration drops to a certain level, the impurity transfer and reaction driving force are small; thus, the separation efficiency would be significantly reduced .…”

Section: Introductionmentioning

confidence: 99%

“…Its connotation mainly includes two aspects: one is the alloy refining process using a large number of metal liquidating agents; − the other is the process of impurity modification by adding a small amount of impurity modifier on the basis of the molten refining system. ,,− Metal liquidating agents and modifiers are collectively referred to as impurity chemical reconstruction medium, which are mainly transition metals such as Cu, Fe, Sn, Ti, and the main group metals such as Al and Zn. The common characteristics of these metal elements are that they have a very small separation coefficient (10 –4 –10 –8 ) in Si, which is conducive to the efficient separation of the medium. , The second of these metal elements in the electron configuration are more easy to lose one electron to form a variable valence state and has not filled the valence shell d orbitals. These metals are easy to interact with Si, B, and P impurities or form compounds with characteristic chemical structures (such as coordination bonds) to change the activity or phase structure of impurity elements so as to achieve the purpose of chemical reconstruction of impurities …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Qian

Zhou

et al. 2021

ACS Sustainable Chem. Eng.

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Removal of trace impurities such as boron (B) and phosphorus (P) has always been a challenge for the preparation of solar-grade silicon (SoG-Si). Chemical reconstruction has been thought to be an effective way to remove trace impurities by changing the phase structure and location of impurities. The traditional way of the chemical reconstruction of impurities at the grain boundary after solidification inevitably relies on the subsequent separation of crystalline Si and chemical reconstruction medium. Thus, we develop a new method for the chemical reconstruction of B at the front of the solidification interface of the Si alloy, which provides advantages for the in situ separation of the reconstructed impurity phase in the supergravity filtration separation process. The chemical reconstruction of B at the solidification front of the Si alloy has been realized by adding 25–75% of the liquation agent aluminum (Al) and about 10 000 ppm of the impurity modifier agent titanium (Ti) with the help of Thermo-Calc thermodynamic calculation and experimental verification. The influence mechanism of the supergravity field on the precipitation behavior of the chemically reconstructed phase TiB2 is revealed by the derived Maxwell–Stefan (MS) equation under the action of the supergravity field. A special filter-type combined crucible is skillfully designed and strictly controlled to cool the crucible containing the alloy melt at a constant temperature gradient under the supergravity field to achieve in situ separation of impurities at the solid–liquid interface of the Si alloy. The chemical reconstruction phase TiB2 is mainly retained on the surface of crystalline Si during the process of supergravity centrifugal filtration, which is more suitable for the deep removal of the B impurity and B content in Si drops below 1.5 ppm by simple pickling. In addition, the Si–Al–(Ti) alloy with a small amount of impurities obtained after centrifugal filtration separation can be further used for the chemical reconstruction of impurities, and the recycling of chemical reconstruction medium has been achieved. The present work proposes a new idea of chemical reconstruction of impurities at the front of alloy solidification and in situ separation, which expands the way of in situ separation of trace impurities at the solid–liquid interface of the alloy.

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A Novel Method of Purifying Metallurgical-Grade Silicon Using Mn as an Impurity Trapping Agent

Zhu

Wei

et al. 2021

Metall Mater Trans B

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Enhancing impurities removal from Si by controlling crystal growth in directional solidification refining with Al–Si alloy

Cited by 21 publications

References 37 publications

Study on the Composition and Interface of Waste Silicon Slag After Secondary Refining

Study on the Composition and Interface of Waste Silicon Slag After Secondary Refining

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

A Novel Method of Purifying Metallurgical-Grade Silicon Using Mn as an Impurity Trapping Agent

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