Elimination of phosphorus vaporizing from molten silicon at finite reduced pressure

Elimination of phosphorus vaporizing from silicon was investigated. Si-P alloy made from electronic grade silicon was used. All the samples were analyzed by GD-MS. Theory calculation determines that phosphorus evaporates from molten silicon as gas species P and P2 at a finite reduced pressure. The experimental results show that phosphorus mass fraction can be decreased from 0.046% （460ppmw） to around 0.001% （10ppmw） under the condition of temperature 1 873 K, chamber pressure 0.6-0.8 Pa, holding time 1 h. Both experimental data and calculation results agree that at high phosphorus concentration, phosphorus removal is quite dependent on high chamber pressure while it becomes independent on low chamber pressure. The reason is that phosphorus evaporates from molten silicon as gas species P2 at a relatively high phosphorus concentration, while gas species P will be dominated in its vapour at low phosphorus content.

Wetting of pure aluminium on graphite,SiC and Al_2O_3 in aluminium filtration

The wettability of pure aluminium on filter materials and on inclusions is believed to be an important factor affecting the filtration of aluminium. The contact angles of molten aluminium on alumina, SiC and graphite were measured under 10-8 bar high vacuum in the temperature range of 1000-1300 °C. To describe the wetting behaviour of the Al on ceramic at lower temperatures used in filtration and casting aluminium, a semi-empirical calculation was employed. The calculated contact angles at 700 °C were around 97° for alumina, 92° for vitreous graphite, 126° for single- and poly-crystal graphite, and 79° for single crystal SiC, respectively. This indicates that aluminium does not wet alumina or graphite （or Al4C3） around the casting temperature, but wets SiC at this temperature. Thus a priming height is required for aluminium to infiltrate an alumina filter. Increasing temperature can also improve the wettability of Al on ceramic.

Removal of SiC particles from solar grade silicon melts by imposition of high frequency magnetic field

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.

用卡拉加斯烧结矿和阿斯曼矿生产锰硅合金的中试试验比较研究

在150kW中试矿热炉(SAF)中,通过三次试验研究了锰硅合金的生产。其中两次试验是以卡拉加斯烧结矿为原料,第三次试验是以质量比为40/60的卡拉加斯烧结矿和阿斯曼矿混合物为原料。前两次试验生产的合金中Si含量低于阿斯曼矿石与卡拉加斯烧结矿混合物生产的合金中Si含量。锰原料的熔化性能测试结果表明,烧结矿比阿斯曼矿石的熔化温度低,烧结矿有助于生产低硅合金。

A thermodynamic description of the Si-rich Si-Fe system

Phase equilibria in the Si-rich domain of the Si-Fe system have been reassessed based on the recent DTA experimental results. Thermodynamic properties of liquid phase have been reassessed using the associated solution model. The properties of DIA- MOND_A4 mixture phase have been added in order to evaluate the phase equilibria for the pure silicon materials. The assessed system is able to reproduce the experi- mental values in the whole composition range of the Si-Fe system.

Factors influencing dissolution of carbonaceous materials in liquid Fe-Mn

Carbon dissolution from four types of metallurgical cokes and graphite was investigated by using immersion rods in a resistance furnace to clarify the influence of factors governing the rate of carbon dissolution from carbonaceous materials into Fe-Mn melts at 1550℃.The factors studied were the nmicrostructure of carbonaceous materials,roughness,porosity and the wettability between carbonaceous materials and the melt.Carbon/metal in terface was characterised by sea nning electron microscopy accompanied with energy-dispersive X-ray spectrometry to investigate the form at io n of an ash layer.The results showed that coke E had the highest dissolution rate.Surface roughness and porosity of the carbonaceous materials seemed to be dominant factors affecting the dissolution rates.Further,crystallite size did not have a significant effect on the dissolution rates.Solid/liquid wettability seemed to affect the initial stage of dissolution reaction.The dissolution mechanism was found to be both mass transfer and interfacial reactions.