The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magne...The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.展开更多
The purification of metallurgical-grade silicon （MG-Si） has been investigated during electron beam melting （EBM） process. The results show that the phosphorus, calcium and aluminum contents decrease significantly ...The purification of metallurgical-grade silicon （MG-Si） has been investigated during electron beam melting （EBM） process. The results show that the phosphorus, calcium and aluminum contents decrease significantly after melting, and magnesium is partially removed. However, no significant change in content for boron and iron has been found. Langmuir＇s equation and Henry law were used to derive the removal effi-ciency for each impurity element. The free surface temperature was estimated by the Hertz-Knudsen-Langmuir equation and silicon＇s vapor pressure equation. Good agreement was found between measured and calculated impurities＇ removal efficiency for phosphorus, calcium and aluminum, magnesium, boron and iron. The deviation between the two results was also analyzed in depth.展开更多
The finite dissolution model of silicon particles in the aluminum melt is built and calculated by the finite difference method, and the lower dissolution limit of silicon particles in the aluminum melt is proposed and...The finite dissolution model of silicon particles in the aluminum melt is built and calculated by the finite difference method, and the lower dissolution limit of silicon particles in the aluminum melt is proposed and verified by experiments, which could be the origin of microinhomogeneity in aluminum-silicon melts. When the effects of curvature and interface reaction on dissolution are not considered; the dissolution rate first decreases and later increases with time. When the effects of curvature and interface reaction on dissolution are considered, the dissolution rate first decreases and later increases when the interface reaction coefficient （k） is larger than 10 1, and the dissolution rate first decreases and later tends to be constant when k is smaller than 10-3. The dissolution is controlled by both diffusion and interface reaction when k is larger than 10-3, while the dissolution is controlled only by the interface reaction when k is smaller than 10-4.展开更多
We have observed some kinds of defects in unseeded rapid zone-melting-recrystallized(RZMR)Si films formed with a RF-induced graphite strip heater system,using cross-section specimen electron microscope.The observed de...We have observed some kinds of defects in unseeded rapid zone-melting-recrystallized(RZMR)Si films formed with a RF-induced graphite strip heater system,using cross-section specimen electron microscope.The observed defects are subgrain boundaries(SGB),dislocations and microtwins.The most commonly observed defects are SGB which formed as a result of some orientation differences between adjacent grains during their rapid self-nucleation growth.Mixed type SGB were frequently observed,although some pure tilt or twist SGB existed also in the Si films.The rotation angular component around the axis parallel to scanning direction is much larger than that around other axes.SGB consist primarily of arrays of dislocation and have crystallographic angular deviations of one degree or less.During Si film cooling,dislocations and microtwins were formed due to non-uniform thermal stress.The crystallographic characters of the dislocations in Si films are the same as those in common bulk Si single crystals.Their Burgers vectors are b=a/2<110>.Some dis- locations run across the Si film,and the amorphous SiO_2 layers on and underneath the Si film can effectively block the dislocations and prevent them from entering the layers.Microtwins were observed in the Si films sometimes,the twinning planes being{111}.展开更多
Using the Stillinger Weber （SW） potential model,we investigate the thermal stability of pristine silicon nanowires based on classical molecular dynamics （MD） simulations.We explore the structural evolutions and th...Using the Stillinger Weber （SW） potential model,we investigate the thermal stability of pristine silicon nanowires based on classical molecular dynamics （MD） simulations.We explore the structural evolutions and the Lindemann indices of silicon nanowires at different temperatures in order to unveil atomic-level melting behaviour of silicon nanowires.The simulation results show that silicon nanowires with surface reconstructions have higher thermal stability than those without surface reconstructions,and that silicon nanowires with perpendicular dimmer rows on the two （100） surfaces have somewhat higher thermal stability than nanowires with parallel dimmer rows on the two （100） surfaces.Futher-more,the melting temperature of silicon nanowires increases as their diameter increases and reaches a saturation value close to the melting temperature of bulk silicon. The value of the Lindemann index for melting silicon nanowires is 0.037.展开更多
Two rotary furnaces of different construction model were used for the research work. One has no recuperating system and the second one has recuperating system. 60 kg of grey cast iron scrap was charged into each of th...Two rotary furnaces of different construction model were used for the research work. One has no recuperating system and the second one has recuperating system. 60 kg of grey cast iron scrap was charged into each of the furnaces at different time, after preheating the furnaces for 40 minutes. 0.5 kg graphite and 0.2 kg ferrosilicon were charged along with the scrap. The theoretical charge calculations have the composition of the melt as 4.0% carbon and 2.0% silicon. Charges in the furnaces were heated to obtain molten metal suitable for casting at 1350°C. The content of the furnaces was tapped three times after the attainment of 1350°C with 15 minutes interval between each tapping. Optical light emission spectrometer was used to analyze the resulting composition of the tapped samples. For type A furnace (without recuperation), sample A has its carbon and silicon contents reduced compared to expected value by 25.5% and 10.8%, sample B reduced by 29% and 13.4% and sample C reduced by 32% and 17.0% respectively. In Type B furnace (with recuperation), sample D has its carbon and silicon contents reduced by 12.2% and 7.3%, Sample E reduced by 13.0% and 8.0% and sample F reduced by 13.9% and 8.9% respectively.展开更多
Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed af...Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.展开更多
文摘The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.
文摘The purification of metallurgical-grade silicon （MG-Si） has been investigated during electron beam melting （EBM） process. The results show that the phosphorus, calcium and aluminum contents decrease significantly after melting, and magnesium is partially removed. However, no significant change in content for boron and iron has been found. Langmuir＇s equation and Henry law were used to derive the removal effi-ciency for each impurity element. The free surface temperature was estimated by the Hertz-Knudsen-Langmuir equation and silicon＇s vapor pressure equation. Good agreement was found between measured and calculated impurities＇ removal efficiency for phosphorus, calcium and aluminum, magnesium, boron and iron. The deviation between the two results was also analyzed in depth.
基金supported by the National Basic Research Program of China(Grant No.2013CB632203)
文摘The finite dissolution model of silicon particles in the aluminum melt is built and calculated by the finite difference method, and the lower dissolution limit of silicon particles in the aluminum melt is proposed and verified by experiments, which could be the origin of microinhomogeneity in aluminum-silicon melts. When the effects of curvature and interface reaction on dissolution are not considered; the dissolution rate first decreases and later increases with time. When the effects of curvature and interface reaction on dissolution are considered, the dissolution rate first decreases and later increases when the interface reaction coefficient （k） is larger than 10 1, and the dissolution rate first decreases and later tends to be constant when k is smaller than 10-3. The dissolution is controlled by both diffusion and interface reaction when k is larger than 10-3, while the dissolution is controlled only by the interface reaction when k is smaller than 10-4.
基金This research is supported by the National Science Foundatinon of China.
文摘We have observed some kinds of defects in unseeded rapid zone-melting-recrystallized(RZMR)Si films formed with a RF-induced graphite strip heater system,using cross-section specimen electron microscope.The observed defects are subgrain boundaries(SGB),dislocations and microtwins.The most commonly observed defects are SGB which formed as a result of some orientation differences between adjacent grains during their rapid self-nucleation growth.Mixed type SGB were frequently observed,although some pure tilt or twist SGB existed also in the Si films.The rotation angular component around the axis parallel to scanning direction is much larger than that around other axes.SGB consist primarily of arrays of dislocation and have crystallographic angular deviations of one degree or less.During Si film cooling,dislocations and microtwins were formed due to non-uniform thermal stress.The crystallographic characters of the dislocations in Si films are the same as those in common bulk Si single crystals.Their Burgers vectors are b=a/2<110>.Some dis- locations run across the Si film,and the amorphous SiO_2 layers on and underneath the Si film can effectively block the dislocations and prevent them from entering the layers.Microtwins were observed in the Si films sometimes,the twinning planes being{111}.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774127)
文摘Using the Stillinger Weber （SW） potential model,we investigate the thermal stability of pristine silicon nanowires based on classical molecular dynamics （MD） simulations.We explore the structural evolutions and the Lindemann indices of silicon nanowires at different temperatures in order to unveil atomic-level melting behaviour of silicon nanowires.The simulation results show that silicon nanowires with surface reconstructions have higher thermal stability than those without surface reconstructions,and that silicon nanowires with perpendicular dimmer rows on the two （100） surfaces have somewhat higher thermal stability than nanowires with parallel dimmer rows on the two （100） surfaces.Futher-more,the melting temperature of silicon nanowires increases as their diameter increases and reaches a saturation value close to the melting temperature of bulk silicon. The value of the Lindemann index for melting silicon nanowires is 0.037.
文摘Two rotary furnaces of different construction model were used for the research work. One has no recuperating system and the second one has recuperating system. 60 kg of grey cast iron scrap was charged into each of the furnaces at different time, after preheating the furnaces for 40 minutes. 0.5 kg graphite and 0.2 kg ferrosilicon were charged along with the scrap. The theoretical charge calculations have the composition of the melt as 4.0% carbon and 2.0% silicon. Charges in the furnaces were heated to obtain molten metal suitable for casting at 1350°C. The content of the furnaces was tapped three times after the attainment of 1350°C with 15 minutes interval between each tapping. Optical light emission spectrometer was used to analyze the resulting composition of the tapped samples. For type A furnace (without recuperation), sample A has its carbon and silicon contents reduced compared to expected value by 25.5% and 10.8%, sample B reduced by 29% and 13.4% and sample C reduced by 32% and 17.0% respectively. In Type B furnace (with recuperation), sample D has its carbon and silicon contents reduced by 12.2% and 7.3%, Sample E reduced by 13.0% and 8.0% and sample F reduced by 13.9% and 8.9% respectively.
文摘Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.
