Simulation of Effect of Surface Tension in Molten Silicon During mc-Silicon Growth Process for PV Applications

Silicon - Numerical simulation of melt flow properties were performed for molten silicon for various temperature differences. The finite element method is used to compute the simulation in a 2D...     

Computational Modelling on Heat Transfer Study of Molten Silicon During Multi-crystalline Silicon Growth Process for PV Applications

Multi-crystalline silicon is an important material with advantages of low-production cost and high conversion efficiency for photovoltaic solar cells. Directional solidifi cation has become the main technique for producing mc-Si ingots for solar cell applications. The study is performed in the framework of the incompressible Navier-Stokes equation in the Boussinesq approximation with convection-conduction equations. The computations are carried out in a two dimensional (2D) axisymmetric model by the finite- element method. The influence of the Reynolds numbers, total heat flux and velocity streamline pattern on the silicon melt was simulated and analyzed for various Rayleigh numbers between 10 to 10 ⁶ with the help of a numerical technique. The following key findings are presented in this paper. The velocity field value is increased above 0.02(m/s), heat flux value is increased to 10 ⁴(W/m ²), when the Rayleigh number is increased above 1000. Reynolds numbers are also studied in five parallel horizontal cross-sections of the melt silicon region for various Prandtl numbers at a critical Rayleigh number of 1000. Reynolds numbers are varied between 100 and 10 ⁵ for the Rayleigh numbers between 10 to 10 ⁶. Meanwhile, the melt has high fluctuation when the Prandtl number is increased above 0.01. The flow is converted from laminar to turbulence at a critical Rayleigh number 1000 and Prandtl number 0.01. These results provide important information for controlling the melt fluctuations during the solidification process which are used to increase the average grain size in growing silicon multicrystals and reduce the dislocation density.     

Improving Heat Transfer Properties of DS furnace by the Geometrical Modifications for Enhancing the Multi Crystalline Silicon Ingot (mc-Si) Quality Using Transient Simulation

Silicon - Heat transfer plays a main role on Directional Solidification (DS) process that determines the multi-crystalline silicon (mc-Si) ingot quality. The 2D axi-symmetric model based numerical...     

Numerical Modelling on Industrial Scale Multi-Crystalline Silicon Growth Process at Critical Prandtl Number for PV Applications

Directional solidification (DS) is a very important technique for growing good quality multi-crystalline silicon at a large scale for photovoltaic (PV) solar cells. Time dependent numerical modelling of the temperature distribution, residual stress and dislocation density rate in multi-crystalline silicon ingots grown by directional solidification have been investigated for five growth stages using the finite volume method at the critical Prandtl number, Pr = 0.01. Impurity concentrations of O, C and SiC are calculated in the central region of grown crystal from bottom to top. The history of temperature distribution, stress generation, and dislocation multiplication are tracked in our modelling continuously considering the growth process from the beginning to the end of the solidification process. This paper reports an advanced understanding of the thermal and mechanical behaviour and generation of impurities in grown multi-crystalline ingots. The computational results show good agreement with experimental data for residual stress, dislocation density and impurities formation in grown ingots. From the obtained results, the crystal quality is evaluated under various solidification stages. We found that the above crystal properties undergo a sudden change at the final stage of the solidification process.     

石英坩埚内高纯隔离层在高效多晶硅铸锭中的应用

多晶硅铸锭过程中,石英坩埚侧壁中的杂质通过固相扩散进入并残留在多晶硅锭的边部,形成多晶硅锭边部的低少子寿命区(边部红区).本文通过在坩埚侧壁上制作三种不同成分的高纯隔离层来阻挡坩埚侧壁中的杂质向硅锭中的扩散,以降低硅锭中的边部红区比例.结果表明采用掺钡高纯隔离层可以使硅锭中的边部红区显著变窄,基本消除硅方中的边部红区.     

Effect of Hot Zone Design on Polycrystalline Silicon Ingot Growth Process by Seeded Directional Solidification

Silicon - This paper uses the finite element method for numerical simulation and builds a transient global model to simulate polycrystalline silicon ingot growing process in CGsim software. The...     

Simulation Analysis of Direction Solidification Process with Fixed Partition Block to Grow Multi Crystalline Silicon Ingot

Silicon - The simulation of Directional Solidification (DS) process without partition block and with partition block has been carried to grow multi crystalline silicon (mc-Si) ingot and the results...     

Numerical Investigation of Bottom Grille for Improving Large-Size Silicon Quality in Directional Solidification Process

Silicon - 2D global transient numerical model based on a new large-size ALD-G7 (G7) crystalline silicon ingot furnace is established and experimentally verified. A new pyramid-shaped bottom grille...     

Modelling on Modified Heater Design of DS System for Improving the Quality of Mc-Silicon Ingot

Silicon - Numerical simulation is an important tool for analyzing and optimizing the multi-crystalline silicon ingot growth process for Photovoltaic (PV) applications. Heat transfer plays an...     

Effect of the Silicon Nitride Coating of Quartz Crucible on Impurity Distribution in Ingot‐Cast Multicrystalline Silicon

Multicrystalline silicon ingots were fabricated via the directional solidification method in a vacuum induction furnace using silicon nitride (Si₃N₄) as quartz crucible coating. The effect of Si₃N₄ coating on the impurity content, transference, and distribution in Si ingots was investigated. The results can be summarized as follows: The impurities contained in Si ingots, including Fe, Ca, Mn, Cu, P, and B, were found to decrease at varying degrees when the inner surface of the quartz crucible was coated with Si₃N₄. A mixed layer composted by Si₃N₄ and Si was observed on the surface of the Si ingot. This mixed layer provided microdefects for the nucleation of metallic impurities. The Fe and N contents in the Si/Si₃N₄ mixed layer changed with the same tendency, and FeSi₂ particles formed on the Si/Si₃N₄ crystalline boundary. Both Fe and Ca precipitated in the SiC particles near the Si ingot/Si₃N₄‐coating interface.     

Investigation of Porous Silicon Layers Properties Using Speckle Techniques for Photovoltaic Applications

Speckle imaging technique (SIT) is used as non-destructive testing to obtain indicative speckle patterns with the aim to be applied for photovoltaic solar     

A New Design of Side Heater for 3D Solid-liquid Interface Improvement in G8 Directional Solidification Silicon Ingot Growth

Silicon - G8 ingots have a significant advantage in production capacity and yield improvement for directional solidification silicon. To improve the uniformity of the 3D solid/liquid (S/L)...     

Numerical Study on Effect of Side Insulation Movement in the Multi-crystalline Silicon Growth Process

Silicon - Numerical simulation is the best tool to understand and optimize the directional solidification (DS) process to grow good quality multi crystalline silicon (mc-Si) ingot for PV...     

部分冷凝工艺制取CO模拟分析

随着化工产品深加工的需要,对一氧化碳纯度要求进一步提高（纯度达到98．5％）。所以提高一氧化碳产品纯度对企业节能降耗及增加经济效益等方面均有着至关重要的作用。本文利用Unisim化工流程模拟软件用部分冷凝方法模拟乙二醇工艺中的一氧化碳深冷分离单元。结果表明,用该方法制取的C可满足下游化工生产对CO产品纯度的要求,且装置提取率可达95％。另外,第一换热器表现比较稳定,第二换热器与CO液体节流压力及流量有较大关系。     

Refining of Silicon Using an Induction Furnace in the Fractional Melting Process

A new fractional melting process using an induction furnace and a centrifugal system has been developed for metallurgical-grade silicon (MG-Si) refining. An induction furnace enables rapid heating and therefore reduces the total refining process time. Impurity-rich liquids can be ejected effectively from the MG-Si by the centrifugal force induced by a motor. The impurity behaviors of the refined samples are observed by scanning electron microscope (SEM). The refining efficiency, which depends on sample size and centrifugal force, is evaluated using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectroscopy (ICP-MS). The purity of the refined silicon increases with the centrifugal force. The correlation between the centrifugal force and silicon purity is rationalized using the surface tension of impurity-rich liquids. In spite of the rapid heating rate by induction furnace, the MG-Si is refined and 96.7% of the impurities are removed at rotation speeds of 3000 rpm.     

蓄热式连续推钢加热炉内钢坯加热过程动态数值模拟

基于商业软件CFX4.3和自编程序,建立了一套CFD模拟系统,并以新钢公司80 t/h蓄热式加热炉为对象,对其进行适当简化的三维动态数值模拟研究,分析了钢坯在炉内的加热过程,并与生产记录数据和现场测试进行对比. 结果表明,蓄热式加热炉能获得较好的流场和温度场分布,钢坯出炉前温度达到1460 K以上,钢坯内各节点的温差不超过10 K,基本满足高效、低耗的钢坯加热工作需要. 但本研究的蓄热式加热炉在生产条件下的温度制度仍存在一定的不合理之处,钢坯离开加热段进入均热段时其表面平均温度为1350 K左右,均热段大部分时间内钢坯仍在被加热,影响均热效果,在今后设计和操作加热炉时应加以改进.     

Experimental Investigation for Generation of Micro-Holes on Silicon Wafer Using Electrochemical Discharge Machining Process

Silicon - Electrochemical discharge machining (ECDM) is a versatile machining process due to its applicability to machine different materials regardless to their properties. In this work, machining...     

Numerical Simulation on the Suppression of Crucible Wall Constraint in Directional Solidification Furnace

Silicon - We carried out a global modelling and transient simulation of bulk multi-crystalline silicon (mc-Si) growth in Directional Solidification (DS) furnace. The temperature distribution and...     

Kinetics Model for the Growth of Silicon Carbide by the Reaction of Liquid Silicon with Carbon

The kinetics and mechanism of reaction of glassy carbon with a pure silicon melt or a Si + Mo melt were investigated. The results showed that the growth of a continuous reaction-formed SiC layer followed a fourth-power rate law in the temperature range of 1430° to 1510°C. A model that could explain the fourth-power rate law was developed. In this model, an internal electric field was assumed to be set up over the reaction-formed SiC layer through a negative space charge, and then the diffusion of the carbon-ion vacancies across this layer, driven predominately by this electric field, was considered as the rate-limiting step for the SiC growth. Neither an increase in the processing temperature nor an addition of 10 wt% Mo into the silicon melt had a significant influence on the reaction kinetics. X-ray diffraction analysis revealed that the reaction products were β-SiC, and β-SiC + MoSi₂ for the Si-C and Si-C-Mo reactions, respectively.