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Jiang D.,Dalian University of Technology | Jiang D.,Key Laboratory for Solar Energy Photovoltaic System of Liaoning Province | Shi S.,Dalian University of Technology | Shi S.,Key Laboratory for Solar Energy Photovoltaic System of Liaoning Province | And 13 more authors.
Renewable Energy | Year: 2015

A hollow silicon ingot was obtained by a solid-liquid separation method inducted by the fountain effect and the formation mechanism of the ingot was also discussed. A layer of solidified shell was formed on the melt surface and the gas dissolved in the melt was separated out. Because of this, the thickness of the shell was gradually increased and expanded due to the sudden change of the chamber pressure leading to the silicon melt being squeezed out from the preset hole of the shell. During this process, the melt left behind contains a high concentration of impurities and can be separated or detached completely from the decontaminated solid. This novel approach has of great potential to inhibit the back diffusion of impurities and to produce a silicon ingot at a high yield rate. © 2014 Elsevier Ltd.

Qiu S.,Xiamen University | Qiu S.,Qingdao Longsun Silicon Technology Company Ltd | Wen S.,Dalian University of Technology | Fang M.,Dalian University of Technology | And 8 more authors.
Vacuum | Year: 2016

A numerical model is proposed to investigate influences of process parameters, including crucible pulling down rates and heater temperature, on crystal growth rates for silicon purification by vacuum directional solidification. The crystal growth rates of a silicon ingot are analyzed based on the interface energy balance equation combining with the temperature field calculated by software of ProCAST, and the segregation behavior of impurities is investigated with the Scheil's equation. The results show that the crystal growth rates decrease linearly with the increase of heater temperature at a fixed value of the crucible pulling down rate, and increase exponentially with the increase of the crucible pulling down rates at a fixed value of the heater temperature. The numerical model is verified by removal of iron impurity from 300 ppmw to 1 ppmw and by the temperature of melt silicon which is recorded by a thermocouple. The results show that numerical results agree well with experimental results. This research is used for adjusting process parameters to control crystal growth during silicon purification by directional solidification. © 2015 Elsevier Ltd. All rights reserved.

Noor Ul Huda Khan Asghar H.M.,Dalian University of Technology | Noor Ul Huda Khan Asghar H.M.,Key Laboratory for Solar Energy Photovoltaic System of Liaoning Province | Noor Ul Huda Khan Asghar H.M.,University of Balochistan | Tan Y.,Dalian University of Technology | And 14 more authors.
Applied Physics A: Materials Science and Processing | Year: 2014

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 × 10-5 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. © 2014 Springer-Verlag Berlin Heidelberg.

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