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Photovoltaic solid waste, particularly diamond-wire sawing silicon powder (DWSSP), has emerged as a significant concern in the industry. Consequently, the recycling and reuse of such waste have become a prominent research focus. In this study, focusing on achieving direct recycling and reuse of DWSSP, the key driving factors for effective purification were identified. It was found that simply increasing the melting temperature and time was insufficient to completely remove volatile impurities, and the migration process in the melt had to be taken into consideration. Additionally, this study focused on analyzing the instability model of inter-granular grain growth and its impact on the stable migration of impurities, with particular attention to the microstructure of inter-granular micro-regions. The thermal control directional solidification technique focused on controlling the temperature gradient during the melt solidification process. This approach helped stabilize the microstructure, enhance impurity migration, and ultimately led to a more effective purification of DWSSP., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

As the unavoidable by-products in the production of solar cells, the recycling and reuse of diamond-wire sawing silicon powder (DWSSP) have always been a key issue in the solar energy industry. However, until now, there is no effective method to achieve effective recovery of high-purity silicon. In this work, a new method was proposed to achieve the recycling of DWSSP. Direct current, as an external means, was introduced into the recycling process of DWSSP, and its influence mechanism on impurity removal process was also discussed. By optimizing the local temperature gradient at the front of the Solid-Liquid interface, and the impurity diffusion behavior at the front of the interface was improved. After purification, the impurity content in the silicon ingot is reduced significantly. Among them, Al, as the main metal impurity element was reduced to less than 5ppmw (from 13580ppmw), and Ni (80.78ppmw), Fe (57.60ppmw), Ti (5.79ppmw), etc. decreased to less than 1ppmw. This work improved the purification efficiency of DWSSP, and put forward an optimized recycling method, which is expected to realize the direct reuse of DWSSP in the photovoltaic industry., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Herein, the effects of Si addition on the microstructure and solidification behavior of a new Ni–Co‐based superalloy are investigated. The microstructure of the as‐cast alloys is mainly composed of γ, γ′, (γ–γ′) eutectics, and MC‐type carbides. The results demonstrate that Si addition significantly decreases the size and volume fraction of (γ–γ′) eutectics, while promoting the formation of Si‐rich phase precipitated in front of the (γ–γ′) eutectics. The formation of a Si‐rich phase is induced by the rejection of Ti and Si into the residual liquid during the γ matrix formation. With the increase in Si content, the size distribution of (γ–γ′) eutectics decreases due to the formation of the Si‐rich phase consuming the forming element of (γ–γ′) eutectics. The solidus and liquidus temperatures of the alloy decrease with the increase in Si. However, the range of melting temperature increases. The Si addition promotes the segregation of alloying elements, and Si tends to segregate in the interdendritic region. [ABSTRACT FROM AUTHOR]

High-performance p-type silicon target materials of Co-doped B and Al elements were produced using Ga and P contaminated upgraded metallurgical-grade silicon (UMG-Si) at the industrial scale. The purity of silicon ingots is above 5.5 N after the directional solidification process, which meets market demand. The segregation behavior of elements and compensation effect on the resistivity are discussed. The effective segregation coefficients of B, Al, Ga, and P for ingot No. 1 were approximately 0.66, 0.14, 0.38, and 0.49, respectively. The segregation coefficients of P, Ga, and Al become larger, the segregation effect tends to become smaller, which is attributed to the doped and contaminated elements that have the recombination effect on the holes and electrons. The distribution of resistivity can be regulated precisely by the compensation difference [NA–ND] along the solidified fraction. The mean resistivity of the ingots is approximately 0.013 Ω cm. Prolonging melting time is conducive to the uniform distribution of doping elements. [ABSTRACT FROM AUTHOR]

• Si is purified through electron beam melting assisted by a few oxides. • Melting achieves the oxidation, evaporation, and segregation of impurity. • Pure SiO 2 offers distinct advantages for the oxidation gas phase separation of B. • The content of B and total impurity is as low as 2.92 and 5.66 ppmw, respectively. Removing stubborn B from Si efficiently and simplifying the purification process are critical challenges that must be addressed in the manufacture of solar grade silicon (SoG-Si) via metallurgical routes. Herein, B is flexibly coupled with other impurities separation procedure, so that metallurgical grade silicon (MG-Si) is purified through simplified electron beam melting (EBM) unlocked by a few oxides (0.1 wt%). EBM fulfills three functions including promotion of oxidation, evaporation of impurities, and induction of directional solidification, giving high-temperature field, high vacuum field, and intense melt convection, which not only ensures the smooth process of B oxidation but also favors the co-removal of other impurities, obtaining high purity Si. As a result, purified Si ingot exhibits a low content of B (from 12.76 ppmw to 2.92 ppmw), and the total content of major impurities is reduced from 1217.24 ppmw to 5.66 ppmw. Significantly, pure SiO 2 could more readily access the high-temperature region of Si melt during EBM, offering distinct advantages for the oxidation gas phase separation of B. This work provides an efficient and robust method for expanding ideas of B removal and simplifying metallurgical routes. [ABSTRACT FROM AUTHOR]

Abstract This paper proposes laser granulating technology for recycling harmful silicon powder waste cut by a diamond-wire saw. The silicon block produced by laser was easily melted in a traditional vacuum smelting furnace to form a silicon ingot with a high yield and filling rate, which could reach up to 94.7% and 65.7%, respectively. The removal efficiency of the carbon contamination was 74.2% during laser melting process and reached 86% after 30 min of vacuum smelting. In addition, laser melting process promoted the removal of most metal impurities, such as Al, Na, Ca, Mg, and so on, in the silicon powder waste without introducing any other impurities. The residual impurities could be further removed by vacuum smelting. The experiment revealed that the out capacity of the silicon block melted by a single laser gun was 1.91 kg/h, the energy consumption of laser melting was 2.63 kWh/kg, and the yield of the silicon block exceeded 97% at a laser power of 2000 W, a laser scanning interval of 5 mm, and a scanning speed of 6 mm/s. Therefore, the proposed approach is one of the most simple and efficient silicon powder waste pretreatment methods. Highlights • Laser granulation is proposed for melting silicon powder waste for the first time. • Laser melting process doesn't introduce any other impurities in theory. • The yield of the silicon block melted by laser exceeded 97%. • Granulation can improve the efficiency of the subsequent smelting process. [ABSTRACT FROM AUTHOR]

Boron (B) removal by slag refining using Na2O-SiO2 was investigated in industrial applications. The experimental results showed that the reasonable ratio range of slag to silicon is about 0.7-0.8; the suitable holding time is about 30 min; the concentration of B is reduced from 1.90 ppmw to 0.17 ppmw by three times slag refining; and the removal efficiency of B reaches 91.1%. Moreover, it is discussed that B in silicon is more inclined to be oxidized by Na2O than SiO2 according to thermodynamic analysis and then volatilized to the atmosphere in the form of Na2B2O4 according to kinetic analysis. [ABSTRACT FROM AUTHOR]

The diffusion layer thickness of impurity during directional solidification process was evaluated under different temperature gradient conditions. The thickness of Fe, Cu, Ni and Ti in silicon ingot under 9.74 K/m were 6.19 mm, 4.92 mm, 4.61 mm and 8.70 mm, respectively; The thickness of Fe, Cu, Ni and Ti in silicon ingot under 28.49 K/m were reduced to 3.35 mm, 1.21 mm, 1.85 mm and 5.81, respectively. The diffusion layer thickness was reduced by the large temperature gradient to lead a low effective segregation coefficient. As a result, the impurity concentration of silicon ingot under 28.49 K/m was reduced to 0.94 ppmw. The strong vortex in the solid-liquid boundary interface was enhanced by the large temperature gradient, as the main transport mechanism to accelerate the diffuse of impurity atom in the diffusion layer，which effectively reduced the thickness of diffusion layer. [ABSTRACT FROM AUTHOR]

A theoretical model to determine distribution of iron impurity during silicon purification by directional solidification with fluctuant crystal growth rate is proposed in this paper. The crystal growth rate is fluctuant usually and it has profound effect on the distribution of iron impurity in practical production. The model validation by the distribution of iron impurity during silicon purification by directional solidification in industrial production and the results show that the calculation agrees with existing experimental results. The results also indicate that distribution of iron impurity is directly correlated with the instantaneous value of crystal growth rate. The high fluctuant distribution of iron impurity during silicon purification by directional solidification can be well explained. Many potential applications of the model in practical production are found, such as predicting the distribution of iron impurity with fluctuant crystal growth rate, evaluating the effect degree of production accident, design and optimization of the process parameters and evaluating of maximum yield for raw silicon with different impurity concentration. Silicon purification with low energy consumption is possible based on the research in this paper. [ABSTRACT FROM AUTHOR]

We successfully achieved the continuous melting of silicon powder in a vacuum electron beam melting system. The characteristic of electron beam melting of silicon powder was revealed by comparing the three different approaches to prefabricate the molten silicon pool. The application of silicon block can be regarded as the most efficient method to prefabricate a stable molten silicon pool. Afterward, the silicon powder was added into the molten silicon pool at different rates by a spiral silicon powder feeding device. Finally, all of the silicon powder was melted completely. Although the P removal efficiency decreases with increasing powder feeding rate during the powder feeding process, an appropriate increase in the powder feeding rate is not only beneficial to improve the melting efficiency of silicon powder but also conductive to the improvement in uniformity of the obtained silicon ingot. Therefore, the powder feeding rate of 10 g/min was the best option in this study. Compared with the melting of silicon block, which has been wildly applied, this continuous powder feeding process can be beneficial to saving smelting time and the total cost. [ABSTRACT FROM AUTHOR]

A silicon target material with the purity of 99.999 wt% (99.999%) was prepared by adding Al-B master alloy in directional solidification. The segregation behavior of the dopant and the effect on the resistivity were studied in this work. It was revealed that the AlB particles in the Al-B master alloy will generate the clusters of [B] and [Al] in molten silicon at 1723 K spontaneously. The concentrations of B and Al were increasing gradually along the solidified fraction in the silicon ingot. The measured values of B were in good agreement with the curve of the Scheil's equation below 85% of the solidified fraction. The measured values of Al were fitting well with the curve of the Scheil's equation when the effective segregation coefficient is 0.00378. It was found that the resistivity of the silicon target material was regulated by B co-doped Al simultaneously in directional solidification. [ABSTRACT FROM AUTHOR]

The behavior of boron redistribution in silicon with and without oxide layer after electron beam injection (EBI) was investigated. Special defect shapes were generated on the surface of bare and oxidized silicon wafers. Secondary ion mass spectrometer was used to measure the boron profile. The results showed that after long EBI time, boron tended to be induced from both sides of the transition region between the oxide layer and silicon. For the sample without oxide layer after EBI, boron tended to diffuse towards the surface and its concentration obviously reduced inside the silicon. The results of the study show the potential use of the process in removing boron impurity in silicon. [ABSTRACT FROM AUTHOR]

An effective boron removal method was developed through a process of combining Si–Sn alloy with slag treatment. Boron content in refined silicon and boron removal fraction by slag containing 5 wt% CaO, 25 wt% SiO2and 70 wt% Na2SiO3and was investigated under varied Si–Sn alloy composition, slag/Si–Sn alloy mass ratio and refining time. Boron was effectively removed by adding tin to metallurgical grade silicon. In particular, the boron content in metallurgical grade silicon decreased from 12.92 ppmw to 0.79 ppmw by adding 50 at% tin under a mass ratio of 2:1 (slag:alloy) at 1723 K. The amount of boron removed increased with increasing amount of tin added, mass ratio and refining time. [ABSTRACT FROM AUTHOR]

Aluminum is one of the main impurities in silicon, which can be separated and eliminated by electron beam melting. However, high removal efficiency can be obtained only by increasing melt temperature or extending refining time, resulting in high energy consumption. In this work, the directional solidification of silicon was achieved by electron beam with exponential decreasing power, considering that aluminum has both characteristics of segregation and evaporation. The distributions of aluminum show increasing trend from the bottom to the top of the electron beam melted silicon ingot, which is the same as that after traditional directional solidification. The removal efficiency is improved by the coupling of segregation and evaporation. Compared with traditional electron beam melting, the loss of silicon reduced by more than 52% and the energy consumption reduced by more than 54%. This method is more effective to remove aluminum from silicon with low energy consumption. [ABSTRACT FROM AUTHOR]

Highlights: [•] Solid-state back-diffusion of impurity was controlled to improve the Si purity. [•] Zn addition was designed to separate Si from Si–Al alloy. [•] Zn addition favors more Si precipitation with low B content. [ABSTRACT FROM AUTHOR]

Small amounts of multicrystalline silicon were melted in an electron beam furnace in different experimental conditions in order to investigate the oxygen evaporation behavior during the electron beam melting (EBM) process. The oxygen content level before and after EBM was determined by secondary ion mass spectroscopy. The oxygen content was reduced from 6.177 to 1.629 ppmw when silicon was melted completely at 15 kW with removal efficiency up to 73.6 %. After that, it decreased continually to <0.0517 ppmw when the refining time exceeded 600 s with a removal efficiency of more than 99.08 %. During the melting process, the evaporation rate of silicon is 1.10 × 10 kg/s. The loss of silicon could be reduced up to 1.7 % during oxygen removal process to a desirable figure, indicating EBM is an effective method to remove oxygen from silicon and decrease the loss of silicon. [ABSTRACT FROM AUTHOR]

Abstract: A new method for boron removal from silicon using electron beam injection (EBI) is proposed. After thermal oxidation on monocrystalline silicon (100) wafer at 1000°C for 1h, EBI was used to induce thermal and negative charging effects to enhance boron diffusion in the oxide film and the silicon substrate. This facilitates boron removal from the silicon substrate. The boron concentration in samples was measured by secondary ion mass spectrometry. The results show that EBI reduced the boron concentration in the silicon substrate by 4.83%. [Copyright &y& Elsevier]

Abstract: A multicrystalline silicon ingot was obtained from metallurgical-grade silicon by vacuum induction melting and directional solidification. Based on the concentration distributions of aluminum and calcium along the growth direction, the removal mechanism of such impurities with both high saturated vapor pressures and low segregation coefficients is investigated. The results show that the removal of this type of impurities only depends on evaporation during vacuum induction melting process, thus their contents decrease significantly due to the strongly evaporation under the high temperature and high vacuum conditions. During subsequent directional solidification process, a model including both segregation and evaporation is used to simulate the concentration distribution. The results show that the impurity distribution is controlled by both two mechanisms in the initial stage of solidification and is mainly determined by segregation in the end stage due to the decrease of the diffusibility and evaporability of the impurity atoms. [Copyright &y& Elsevier]

Abstract: Solar energy is expected to be in great demand within the next few years. In relation to this, a global shortage in the solar-grade silicon (SoG-Si) used in the production of solar cells has motivated numerous studies on metallurgical-grade Si (MG-Si) refining. However, improvements in this material are limited by the difficulties involved in reducing boron (B) and phosphorus content. The present study investigated the removal of B using (CaF2)-Al2O3-CaO-SiO2 and Na2SiO3-CaO-SiO2 slag in an ambient air atmosphere in order to refine MG-Si. The mass transfer coefficients of B in molten Si (k d[B]=1.19×10−4 cms−1) and BO1.5 in molten slag ( =1.01×10−5 cms−1) were deduced through kinetic analysis. The mass transfer process of boron oxide limited slag refining; however, secondary slag treatment effectively improved the efficiency of B removal. L B was determined by the combined effect of the oxygen partial pressure and the molten slag structure. [Copyright &y& Elsevier]

Abstract: This paper proposed a theoretical model to determine the thermal contact resistance (TCR) on the surfaces of silicon and copper during electron beam melting. The effect of temperature and pressure on TCR, based on specific melting process conditions, was discussed. Hertz's theory was used to analyze the characteristics of material surfaces and to calculate the relationship between the pressure and distance of contact surfaces, the real contact area and the number of contact asperities combined with the physical characteristics of the material. The geometric parameter of the theoretical model was obtained based on theoretical calculations. The TCR of the entire surface was obtained by analyzing the temperature field of silicon and copper using Ansys and TCR equations. The relationship among TCR, pressure, and temperature were found. The computational results agreed with existing experimental results. [Copyright &y& Elsevier]

Abstract: In this paper a mathematical model is developed to investigate the removal of volatile impurities in molten silicon by electron beam melting (EBM) with a high efficiency and low energy consumption. The temperature distribution of molten silicon is obtained using the commercial software FLUENT. Based on the temperature distribution, the vaporization behaviors of phosphorus and silicon are investigated by Langmiur's vaporization theory. The results show that the evaporation rate of silicon during EBM increases exponentially with the increase of beam power, while, it decreases with the increase of scanning radius. The optimal parameters are discussed from the aspect of efficiency and energy saving. The energy consumption decreases with the decrease of scanning radius and with the increase of the beam power. The optimum values are consider to be with a scanning radius of 0.0339 m and a beam power of 23.4 kW for 0.5 kg silicon when phosphorus is removed from 1.44 × 10−2 to 1 × 10−5 (wt.%). [Copyright &y& Elsevier]

Abstract: Solidification rate has a significant influence on purification of silicon due to segregation of impurities at a liquid–solid interface of a solidifying silicon ingot. A mathematical model is developed to evaluate time-dependent position of the liquid–solid interface and solidification rate of electron beam melted ingots. A series of solidification experiments with different cooling rates are conducted to measure position of a line which separates directionally grown columnar crystals visible in cross-sections of the solidified ingots. Results show that not the whole ingot solidifies directionally when the reduction rate of the beam current is larger than 1.67 mA/s. The position of the dividing line depends on cooling rate and the experimental trend is consistent with that resulted from theoretical simulations. Modeling shows that the solidification rate changes fast when the beam current reduces linearly that is detrimental for segregation of impurities. It also predicts that an exponential reduction of the beam current leads to a uniform solidification rate which is beneficial to segregation of impurities, though not all exponential current reductions lead to this kind of solidification behavior. [Copyright &y& Elsevier]

Abstract: In the current study, a new method for the removal of phosphorus in molten silicon, electron beam candle melting (EBCM), is proposed and discussed. The proposed method combines the characteristics of electron beam melting (EBM) and the high saturated vapor pressure of P in molten Si. Simulation results show the existence of three typical temperature distributions and morphologies of the molten pool that correspond to the different radii of the electron beam circular pattern at constant power. The critical molten pool with the maximum surface area and the minimum depth was determined. EBCM resulting in the critical molten pool was proven to be more effective in the removal of P in molten Si compared with EBM. In addition, the energy utilization ratio was enhanced. [Copyright &y& Elsevier]

Abstract: During the refinement of metallurgical-grade silicon (MG-Si), Al and Ca cannot be reduced to a target level by conducting directional solidification only once. Electron beam candle melting (EBCM) is a new method that can be used to further reduce Al and Ca by directly melting Si ingots after directional solidification. A certain stable molten pool with a maximum surface area and a minimum depth exists and is proven to effectively remove Al and Ca. The energy utilization ratio during EBCM is also compared with that of electron beam melting (EBM). [Copyright &y& Elsevier]

• Non-transfer arc granulation is first proposed for recycling silicon powder waste. • Non-transfer arc granulating process doesn't introduce any other impurities in theory. • The yield of the silicon block granulated by non-transfer arc exceeded 96%. • Granulation method can significantly improve the subsequent smelting efficiency. Non-transfer arc assisted vacuum smelting technology is presented for the first time to recycle harmful silicon powder waste derived from diamond-wire cutting. The final yield and filling rate of silicon could reach 93.9% and 73%, respectively. The oxidation characteristics of silicon powder waste, formation mechanism of a hollow silicon block and removal efficiency of impurities were analyzed in detail to offer profound insights into a non-transfer arc granulation method. The critical conditions for continuous and efficient preparation of a solid silicon block were further confirmed through orthogonal experiments with 7.5 kW welder output power, 3 mm vertical scanning height, and 5 mm/s scanning speed. The yield of the silicon block was more than 96%. Meanwhile, the granulating process demonstrated a favorable effect on removing most impurities, such as C, Al, and Na, without introducing any other impurities. The residual impurities could be further removed by vacuum directional smelting. Given the extremely low equipment cost and huge room for improvement, this work is crucial for large-scale recovery of silicon powder waste. [ABSTRACT FROM AUTHOR]

The behavior of carbon in multicrystalline silicon scraps by electron beam melting was investigated in this study. It was found that the process favors nucleation of SiC on Si 3 N 4. Furthermore, carbon tends to gather to top surface of the ingots with increasing melting time, and the reaction between oxygen and carbon favors carbon migration. The melt convection and temperature gradient caused by electron beam are employed to be the dominate reason the phenomenon occurs. The results can provide guidance in silicon recycling. [ABSTRACT FROM AUTHOR]

Abstract: Purification process of MG-Si was limited by the difficulties involved in reducing boron content. The possibility of removing impurity boron (B) in MG-Si using CaO–Al2O3–SiO2–CaF2 slags was investigated in the present study. Different from traditional research methods, the whole melting process was carried out under atmosphere condition, which was closer to the actual production conditions. The thermodynamic and kinetic mechanisms of B removal were analyzed. Based on the ionic structure theory, the relation between ionic structure of slags at high temperature and optical basicity can be explained firstly. The parameters, including the slag optical basicity, melting time and CaF2 content were discussed. The boron content was reduced from original 25 ppmw to 4.4 ppmw through 120 min melting with the optical basicity of 0.551 and 5 wt% CaF2 additions. [Copyright &y& Elsevier]

Abstract: The purification of metallurgical grade silicon, especially the removal of aluminum, was investigated by electron beam melting and solidification. Small amounts of silicon raw materials were melted in an electron beam furnace with same melting time and different solidification time to obtain the distribution of Al in silicon ingot. The removal mechanisms in different stages were also discussed. The results show that the removal of Al during melting process only depends on evaporation and that during solidification process depends on both segregation and evaporation. The distribution of Al shows an obvious increasing trend from the bottom to the top of the silicon ingot when solidification time is 600 s. The removal efficiency in most area is close to that in the ingot solidified instantaneously, but the energy consumption is less, which is considered to be an effective way for the purification of silicon. [Copyright &y& Elsevier]

Abstract: Small amounts of metallurgical grade silicon were melted in an electron beam furnace in different experimental conditions in order to investigate the aluminum (Al) evaporation behavior during the electron beam melting (EBM) process. Impurity was significantly decreased in the early periods of melting at 9, 15, and 21 kW. These changes slowed down with the extension of the melting time. Moreover, the removal reaction of Al by evaporation from molten silicon during the EBM process occurred in accordance with the first order kinetics. The calculated mass transfer coefficients of Al at 1941, 1964, and 2051 K increased with the increase of melting temperature. The removal rate of Al was controlled by the transportation of Al from the bulk of silicon metal to the molten/vacuum interface within the range of the experimental temperature. [Copyright &y& Elsevier]

Electron beam melting technology can remove volatile impurities from silicon very effectively. However, the strong cooling capacity of water-cooled copper crucible brings high energy consumption, which confines the wide application of this technology. As far as energy utilization is concerned one can see in this paper, the refining process of silicon is improved based on numerical simulation and experimental results. The energy efficiency is increased through using a graphite lining between silicon and the bottom of water-cooled copper crucible. The results show the addition of graphite lining is resulting in increased thermal resistance and the heat loss is reduced. Compared with traditional electron beam melting technology, the temperature of the melt pool is increased at the same power accelerating purification process. The experiment results show that refining cycle time for same amount of material can be reduced while keeping same purification efficiency. As a consequence, the energy consumption is reduced by 33%. • Graphite lining is used to improve energy efficiency during silicon refining by EBM. • Experiments with industrial systems confirm results of working. • The single refining time for silicon purification decreases from 1.5 h to 1 h. • The energy consumption per unit mass during EBM is reduced by 33%. [ABSTRACT FROM AUTHOR]

Arsenic is one of the main impurity elements in silicon. Electron beam melting (EBM) is considered an effective method for the purification of silicon. The removal of arsenic from silicon is performed by electron beam solidification furnace in this paper. The results demonstrated that arsenic could be removed effectively by EBM process with the average removal efficiency up to 95.4% and show the morphology of silicon ingot is less essential to distribution of arsenic impurities in the silicon ingot. The evaporation behavior of arsenic atoms is more important in the process of arsenic removal by EBM. The relationship between the evaporation coefficient of arsenic impurities and temperature was deduced. It provides a reference for further research on removal arsenic in silicon by EBM. • Evaporation mass transfer is the key step for removing arsenic impurities. • The relationship between saturated vapor pressure and temperature of arsenic. • The relationship between evaporation coefficient and temperature of arsenic impurities was deduced. [ABSTRACT FROM AUTHOR]

A new method for SiC elimination from multicrystalline silicon with Al addition by using the chemical reaction between Al and SiC is conducted in this study. Inclusion-free region is obtained when Al addition content increases to 5.4% and 7.9%. SiC particles tend to pile up around Al during the process and precipitate at ingot bottom. Furthermore, Al-Si alloying occurs at the inclusion-free region. The electron probe micro analysis mapping illustrates the existence of carbon in the precipitated Al which indicates the occurrence of chemical reaction between SiC particles and Al during the process. The results can be an effective way to eliminate SiC for silicon scraps recycling. [ABSTRACT FROM AUTHOR]

• An easy and efficient way to comprehensive recycling silicon kerf waste (SKW) and photovoltaic glass waste (PVGPs). • With the additive of PVGPs, the silicon yield has increased from 51.44% to 87.66%. • With the different phase affinity, the transfer of SiO 2 surface-layer and the separation of slag-silicon has been realized. • The network breakers (such as Ca2+ and F-) in the PVGPs destroyed the network structure of SiO 2 and provided a good micro-environment for silicon separation. Large amounts of silicon kerf waste (SKW) and photovoltaic (PV) glass waste are being generated as the PV industry grows. At present, independent approaches have been adopted to recycle these waste materials. In this work, an original approach was first proposed for recycling silicon by using PV glass particles (PVGPs) that refine SKW. Compared with the experiment wherein no PVGPs were added, silicon yield increased from 51.44% to 87.66%. Furthermore, the transfer of the SiO 2 surface-layer and the separation of silicon from slag were realized with different phase affinities. Moreover, network breakers, such as Ca2+ and F−, in PVGPs destroyed the network structure of SiO 2 and provided a favorable microenvironment for silicon separation. This work innovatively used PV glass waste to refine SKW. It is expected to provide a green cleaning solution for the circular development of the PV industry. [ABSTRACT FROM AUTHOR]

A multicrystalline silicon ingot with columnar and irregular grains was obtained from metallurgical-grade silicon (MG-Si) by directional solidification. The segregation behaviors of substitutional and interstitial impurities in different grain morphologies have been studied. The concentration distribution of substitutional impurities (B and Al) in the silicon ingot was accord with the Scheil's equation, which depended on the grain morphology. However, the concentration distribution of interstitial impurities (Fe, Ti, Cu, and Ni) was only accord with the Scheil's equation under the columnar grains growth condition. The difference lattice sites of the impurities will result in the disparate segregation behavior of impurities for columnar and irregular grains growth, which leads to the diverse concentration distribution of substitutional and interstitial impurities in the silicon ingot. Furthermore, the transport mechanism of interstitial and substitutional impurities in front of the solid-liquid interface boundary has been revealed. [ABSTRACT FROM AUTHOR]