Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell (made of pyrolytic boron nitride) with stationary electrodes. Viscosity of th...Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell (made of pyrolytic boron nitride) with stationary electrodes. Viscosity of the binary system Na3AlF6-SiO2 was measured by computerized torsion pendulum method. It was found that conductivity and viscosity varied linearly with temperature in all investigated mixtures. Obtained content dependence of electrical conductivity (isotherms) was divided into two parts. First, one represented the content region up to 10%(mole fraction) of SiO2;second, the region was with a higher content of SiO2 (from 10%up to 40%). While the conductivity considerably decreased with content of SiO2 in the second part; it surprisingly rose in the low content range. A small addition of SiO2 to the molten cryolite (up to 10%) could slightly increase viscosity, but had no influence on the slope of this dependence since it is responsible for a glassy-networks formation in the melt. Further addition of SiO2 to the molten cryolite had a huge effect on the viscosity.展开更多
Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells a...Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon (MG-Si) was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics (CFD) were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.展开更多
The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refinin...The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refining process of the metallurgical grade silicon was studied via separation coefficient of impurity phosphorus in the metallurgical grade silicon and vapor-liquid equilibrium composition diagram of Si-P binary alloy at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined. The results show that the vacuum distillation should be taken to obtain silicon with less than 10-7 P,and the impurity phosphorus is volatilized easily by vacuum distillation in thermodynamics. Phosphorus is distilled from the molten silicon and concentrated in vapor phase.展开更多
A new method for production of solar grade silicon(SoG-Si) at low cost from metallurgical grade silicon(MG-Si) via vacuum metallurgical technique was proposed,which is a promising process to feedstock solar energy sil...A new method for production of solar grade silicon(SoG-Si) at low cost from metallurgical grade silicon(MG-Si) via vacuum metallurgical technique was proposed,which is a promising process to feedstock solar energy silicon material independence of traditional Siemens method. In this procedure,pre-treatment of MG-Si using hydrometallurgical routes to remove the metallic impurities such as iron and aluminum to reduce the production cost is an important process. The influences of acid agents,acid concentration,reaction time and temperature and particle size of raw material ground on the removal efficiency of iron and aluminum impurities were investigated,respectively. The results show that the optimum operation conditions for leaching in acid C are:acid concentration 6 mol/L,temperature 60 ℃,time 4 d,diameter for raw material 50 μm. The removal efficiencies of impurities iron and aluminum are up to 85% and 75%,respectively.展开更多
The kinetics on vacuum refining process of metallurgical grade silicon was studied using maximum evaporation rate,critical pressure and mean free path of phosphorus in the metallurgical grade silicon at different temp...The kinetics on vacuum refining process of metallurgical grade silicon was studied using maximum evaporation rate,critical pressure and mean free path of phosphorus in the metallurgical grade silicon at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined in detail. The results show that the fractional vacuum distillation should be taken to obtain silicon with high purity. Impurity phosphorus volatilize with the maximum evaporation rate of 1.150×105- 1.585×106 g/(cm2·min) in the temperature range of 1 073-2 173 K and the pressure below 2.1 Pa. Because the value of ωmax,P is at least 108 times of ωmax,Si,Si hardly evaporates and remains in the residual,which indicates that phosphorus can be removed from metallurgical grade silicon(MG-Si) completely.展开更多
The removal of boron from metallurgical silicon in slag system of CaO-SiO2-10%CaF2 was investigated. The partition coefficient of boron (LB) between slag and silicon phase was studied under different conditions of s...The removal of boron from metallurgical silicon in slag system of CaO-SiO2-10%CaF2 was investigated. The partition coefficient of boron (LB) between slag and silicon phase was studied under different conditions of slag basicity (CaO/SiO2 ratio), temperature, mass ratio of slag to silicon and gas blowing. The results show that LB has a maximum value of 4.61 when the CaO/SiO2 mass ratio is around 2 at l 873 K. The logarithm of LB is linear to the reciprocal of temperatures in the range of 1 773-1 973 K. LB increases with the increase of mass ratio of slag to silicon, but it does not increase markedly when the ratio excesses 3. Gas blowing can sionificantlv increase the removal of boron, and LR increases with the increase of water vapor content.展开更多
The removal of B and P consumes most of heat energy in Si metallurgical purification process for solar-grade Si. Metal-liquating purification of metallurgical grade silicon (MG-Si), also called Si-recrystallization ...The removal of B and P consumes most of heat energy in Si metallurgical purification process for solar-grade Si. Metal-liquating purification of metallurgical grade silicon (MG-Si), also called Si-recrystallization from metal liquid, was a potential energy-saving method for the removal of B and P efficiently, since Si could be melted at lower temperature by alloying with metal. The selection criteria of metal-liquating system was elaborated, and Al, Sn and In were selected out as the optimum metallic mediums. For Sn-Si system, the segregation coefficient of B decreased to 0.038 at 1 500 K, which was much less than 0.8 at the melting point of Si. The mass fraction of B was diminished from 15×10^-6 to 0.1×10^-6 as MG-Si was purified by twice, while that of most metallic elements could be decreased to 0.1×10^-6 by purifying just once. During the metal-liquating process, the formation of compounds between impurity elements and Si was also an important route of impurity removal. Finally, one low-temperature metallurgical process based on metal-liquating method was proposed.展开更多
基金supported by the Science and Technology Assistance Agency (APVV-0460-10 and SK-CN-0029-12)Slovak Grant Agency (VEGA 2/0116/14 and VEGA 2/0095/12)+2 种基金the National Natural Science Foundation of China (51322406)the Program for New Century Excellent Talents (NCET-13-0107)Ministry of Education of China
文摘Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell (made of pyrolytic boron nitride) with stationary electrodes. Viscosity of the binary system Na3AlF6-SiO2 was measured by computerized torsion pendulum method. It was found that conductivity and viscosity varied linearly with temperature in all investigated mixtures. Obtained content dependence of electrical conductivity (isotherms) was divided into two parts. First, one represented the content region up to 10%(mole fraction) of SiO2;second, the region was with a higher content of SiO2 (from 10%up to 40%). While the conductivity considerably decreased with content of SiO2 in the second part; it surprisingly rose in the low content range. A small addition of SiO2 to the molten cryolite (up to 10%) could slightly increase viscosity, but had no influence on the slope of this dependence since it is responsible for a glassy-networks formation in the melt. Further addition of SiO2 to the molten cryolite had a huge effect on the viscosity.
文摘Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon (MG-Si) was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics (CFD) were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.
基金Project(50674050) supported by the National Natural Science Foundation of ChinaProject(2006BAE01B08) supported by Sustentation Project of Science and Technology of ChinaProject(20060674004) supported by the Doctorial Programs Foundation of Ministry of Education of China.
文摘The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refining process of the metallurgical grade silicon was studied via separation coefficient of impurity phosphorus in the metallurgical grade silicon and vapor-liquid equilibrium composition diagram of Si-P binary alloy at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined. The results show that the vacuum distillation should be taken to obtain silicon with less than 10-7 P,and the impurity phosphorus is volatilized easily by vacuum distillation in thermodynamics. Phosphorus is distilled from the molten silicon and concentrated in vapor phase.
基金Project (50674050) supported by the National Natural Science Foundation of ChinaProject (2006BAE01B08) supported by the Sustentation Project of Science and Technology of ChinaProject (20060674004) supported by PhD Programs Foundation of Ministry of Education of China
文摘A new method for production of solar grade silicon(SoG-Si) at low cost from metallurgical grade silicon(MG-Si) via vacuum metallurgical technique was proposed,which is a promising process to feedstock solar energy silicon material independence of traditional Siemens method. In this procedure,pre-treatment of MG-Si using hydrometallurgical routes to remove the metallic impurities such as iron and aluminum to reduce the production cost is an important process. The influences of acid agents,acid concentration,reaction time and temperature and particle size of raw material ground on the removal efficiency of iron and aluminum impurities were investigated,respectively. The results show that the optimum operation conditions for leaching in acid C are:acid concentration 6 mol/L,temperature 60 ℃,time 4 d,diameter for raw material 50 μm. The removal efficiencies of impurities iron and aluminum are up to 85% and 75%,respectively.
基金Project(50674050) supported by the National Natural Science Foundation of ChinaProject(2006BAE01B08) supported by the Sustentation Project of Science and Technology of ChinaProject(20060674004) supported by Doctorial Programs Foundation of Ministry of Education of China.
文摘The kinetics on vacuum refining process of metallurgical grade silicon was studied using maximum evaporation rate,critical pressure and mean free path of phosphorus in the metallurgical grade silicon at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined in detail. The results show that the fractional vacuum distillation should be taken to obtain silicon with high purity. Impurity phosphorus volatilize with the maximum evaporation rate of 1.150×105- 1.585×106 g/(cm2·min) in the temperature range of 1 073-2 173 K and the pressure below 2.1 Pa. Because the value of ωmax,P is at least 108 times of ωmax,Si,Si hardly evaporates and remains in the residual,which indicates that phosphorus can be removed from metallurgical grade silicon(MG-Si) completely.
基金Project(2007J0012)supported by the Natural Science Foundation of Fujian Province,ChinaProject(2007HZ0005-2)supported by the Key Technological Program of Fujian Province,China
文摘The removal of boron from metallurgical silicon in slag system of CaO-SiO2-10%CaF2 was investigated. The partition coefficient of boron (LB) between slag and silicon phase was studied under different conditions of slag basicity (CaO/SiO2 ratio), temperature, mass ratio of slag to silicon and gas blowing. The results show that LB has a maximum value of 4.61 when the CaO/SiO2 mass ratio is around 2 at l 873 K. The logarithm of LB is linear to the reciprocal of temperatures in the range of 1 773-1 973 K. LB increases with the increase of mass ratio of slag to silicon, but it does not increase markedly when the ratio excesses 3. Gas blowing can sionificantlv increase the removal of boron, and LR increases with the increase of water vapor content.
基金Project (2009BAB49B04) supported by National Key Technologies R&D Program, China
文摘The removal of B and P consumes most of heat energy in Si metallurgical purification process for solar-grade Si. Metal-liquating purification of metallurgical grade silicon (MG-Si), also called Si-recrystallization from metal liquid, was a potential energy-saving method for the removal of B and P efficiently, since Si could be melted at lower temperature by alloying with metal. The selection criteria of metal-liquating system was elaborated, and Al, Sn and In were selected out as the optimum metallic mediums. For Sn-Si system, the segregation coefficient of B decreased to 0.038 at 1 500 K, which was much less than 0.8 at the melting point of Si. The mass fraction of B was diminished from 15×10^-6 to 0.1×10^-6 as MG-Si was purified by twice, while that of most metallic elements could be decreased to 0.1×10^-6 by purifying just once. During the metal-liquating process, the formation of compounds between impurity elements and Si was also an important route of impurity removal. Finally, one low-temperature metallurgical process based on metal-liquating method was proposed.