切克劳斯基硅熔体中液流图式研究

单晶硅目前是电子工业中最重要的材料。尽管已经知道用直拉法(SZ法)生长的硅单晶的某些特性——例如旋涡缺陷——与熔体流动情况有密切关系,因而迫切要求了解它的熔体流动图,但由于硅熔体是强腐蚀剂,关于它的流体行为的物理测量很困难,精确地获得硅熔体流动图目前尚不可能。近年来,国外一些学者引用流体动力学对 CZ 法硅熔体做了很多理论估计。在这个     

锶在其氯化物熔体中溶解行为的电化学研究

本文用电化学法,在1073～1123K内,通过测定浓差电池Sr(s)|SrCl_2-Sr(饱和)熔体|SrCl_2-xSr熔体|Mo电动势与温度的关系,研究了锶在SrCl_2熔体中的溶解度和溶解机理,并回归拟合得到锶在SrCl_2熔盐中的溶解度,溶解反应平衡常数和反应自由焓变化与温度的关系方程式。     

铸咀型腔铝熔体流态分析

以两种铸咀型腔熔体流动为研究对象，分析了在常规铸轧和超薄快速铸轧时，铸咀型腔的熔体速度，型腔结构，熔体流动雷诺数的变化对铝熔体流态的影响规律，并得出结论：无论是常规铸轧还是超薄快速铸轧，铸咀型腔体流动都存在不同强度的紊流区域，但是在铸咀出口处为准层流。     

压铸模的设计与制造(中)

6 浇注系统的设计浇注系统对压铸的生产率和压铸件的质量有很大的影响。浇注系统的设置和铸造条件的设定如果不正确,就会导致充填不良或压铸件与压铸模具的烧结,以致不能进行正常生产。但是,把浇注系统的设置与压铸金属熔体的流动性的关系变成实用的理论还有一段距离。因此本节所介绍的只是金属熔体的流动条件对金属熔体流动性的影响。这里     

铁矿石溶解与烧结熔体流动行为机理

 在铁矿石烧结过程中,铁矿石部分溶解于烧结熔体,直接影响熔体的性质,进而影响烧结矿的黏结。为了明晰铁矿石与烧结熔体的相互作用,采用化学纯试剂煅烧法制备以Ca_3.6Fe_14.4O_25.2和CaFe₂O₄矿物为主的铁酸钙系黏附粉。以7种核心铁矿石-铁酸钙系(w(CaO)=15%)黏附粉构成烧结偶为主要研究对象,采用实验室烧结方法,研究了核矿石溶解与烧结熔体流动行为。在此基础上,使用化学纯试剂模拟核矿石的化学组成,考察了核矿石SiO₂、Al₂O₃含量对熔体横向流动面积和核矿石溶解指数的影响规律及机理。结果表明,在核矿石溶解于CaO-Fe₂O₃液相后,形成了交互层区域。核矿石中矿物,尤其是石英,溶解进入熔体,在靠近熔体一侧促使生成复杂CaO-Fe₂O₃系液相,而在靠近核矿石一侧促使简单CaO-Fe₂O₃系液相转变为CaO-Fe₂O₃-SiO₂系液相。靠近熔体一侧析出以铁酸钙系和赤铁矿为主的矿物,而靠近核矿石一侧析出以硅酸盐和赤铁矿为主的矿物。随着核矿石SiO₂含量的增加,一方面,使得溶解进入熔体中的SiO₂数量增加,溶解指数得到提升;另一方面,提升了简单CaO-Fe₂O₃系液相的黏度,从而使得熔体横向流动面积减小。随着核矿石Al₂O₃含量的增加,溶解进入熔体中的Al₂O₃数量增加,进而熔体横向流动面积降低,而核矿石溶解指数升高。Al₂O₃相较于SiO₂对核矿石溶解与熔体流动行为的影响更大。     

Al-Si-Fe合金熔体质量作用浓度的热力学模型

基于原子分子共存理论(AMCT)建立了计算Al-Si二元熔体及Al-Si-Fe三元熔体结构单元质量作用浓度的热力学模型.针对Al-Si二元系熔体,根据FactSage热力学软件计算的活度得到生成复杂分子Al2Si和AlSi的反应的标准摩尔吉布斯自由能的表达式,进而获得了 Al-Si二元熔体中标准摩尔溶解吉布斯能变的表达...     

硅酸盐熔体的结构及热力学性质

本文评述了二元硅酸盐熔体的几种热力学模型,介绍了各种模型假设前提和要点,讨论了这些模型与热力学性质的关系,通过计算实例对不同模型所得的活度,混合自由能及离子分布等进行了比较,指出了各种模型的特点及限制条件。     

铁浴式熔融还原型熔体的性质

研究了铁浴式熔融还原型熔体的组成与性质的关系，测试了熔体对耐火材料的浸润性，分析了熔体中ＦｅＯ浓度，熔体温度，耐火材料的组成及结构，耐火材料中石墨碳含量等对熔体与耐火材料间浸润性的影响，同时测试了熔体组成与流动性的关系，熔体中ＦｅＯ浓度，熔渣碱度对熔体的熔化温度的影响，测定和分析了熔体组成与粘度变化的关系，结果表明，熔中ＦｅＯ浓度是影响熔体性质的最关键因素，ＦｅＯ浓度提高，熔体对耐火材料的润湿能力     

铁液中〔Y〕—〔O〕平衡研究

用直接平衡法研究了1575—1625℃熔体中的[Y]—[O]平衡关系,测得了钇的脱氧常数及钇与氧活度相互作用系数与温度的关系,钇的脱氧产物Y_2O_3的标准生成自由能与温度的关系。给出了1575、1600、1625℃铁液中钇的脱氧平衡图,及平衡时钇活度与氧活度的关系式。     

铝电解槽熔体流动设计参数的研究

本文通过列电解槽熔体流动的研究,从理论上推导出了降低熔体流速所需的条件,提出了获得这些理想条件所要求的设计参数,对如何设计高效能大容量电解槽有一定的参考价值。     

Vacuum Refining of Molten Silicon

Metallurgical fundamentals for vacuum refining of molten silicon and the behavior of different impurities in this process are studied. A novel mass transfer model for the removal of volatile impurities from silicon in vacuum induction refining is developed. The boundary conditions for vacuum refining system??the equilibrium partial pressures of the dissolved elements and their actual partial pressures under vacuum??are determined through thermodynamic and kinetic approaches. It is indicated that the vacuum removal kinetics of the impurities is different, and it is controlled by one, two, or all the three subsequent reaction mechanisms??mass transfer in a melt boundary layer, chemical evaporation on the melt surface, and mass transfer in the gas phase. Vacuum refining experimental results of this study and literature data are used to study the model validation. The model provides reliable results and shows correlation with the experimental data for many volatile elements. Kinetics of phosphorus removal, which is an important impurity in the production of solar grade silicon, is properly predicted by the model, and it is observed that phosphorus elimination from silicon is significantly increased with increasing process temperature.     

Interfacial phenomena between fluxes for continuous casting and liquid stainless steel

Abstract

Casting powders melt on the surface of the liquid metal forming a liquid slag layer. Samples taken during casting revealed convective flows in the flux layer and mass exchange with the liquid metal. It is demonstrated that concentrations of certain elements are considerably higher at the phase boundary than in the bulk of the metal and slag phase. Disturbances of interfacial tension produced by mass and charge transfer evidently cause strong shearing forces which act in parallel with the phase boundary. These forces induce convective movements in the flow boundary layer. Convective flows next to the interface between two liquids have been studied in laboratory experiments using various liquids. The results show that the movement velocity of volume elements next to the interface (due to disturbances of interfacial tension) are dependent on liquid layer thickness and on liquid properties. A new dimensionless number describing this manner of convective flow and suitable for evaluation of experimental results is introduced. Its contribution to the total mass transfer will be shown. A dimensionless function describing the relation between convective flows in the slag layer and mass transport is theoretically developed. Coefficients of this function for Ti transfer into the flux layer have been determined empirically.     

电沉积硅技术的历史和发展趋势

介绍了沉积硅的几种方法。常规的沉积方法为固体粉末法和气相沉积法。固体粉末法要消耗大量的硅铁，且硅层存在气孔；气相沉积法由于涉及气体，其保护措施和密闭性的严格要求使其应用受到了严格的限制。新型的沉积方法为电沉积法。电沉积法涉及高温熔盐，但其所得渗硅层质量性能良好，很受国外工作者的欢迎。本文介绍了各方法的影响因素，回顾了电沉积硅的历史，指出电沉积硅法具有良好的发展趋势。     

Interfacial Convection and Mass Transport in Thin Liquid Layer

Investigations into the phenomenology of convection flows next to the interface between two liquids have been carried out in laboratory experiments using various liquids. Then convection flows have been observed in industrial tests during continuous casting. The results show that the motional velocity of volume elements next to the interface due to disturbances of interfacial tension (produced by mass and charge transfer) depends on liquid layer thickness and on liquid properties. A new dimensionless number is introduced to describe this manner of convective flow; it is also suitable for evaluation of experimental results. Furthermore, a dimensionless function is theoretically developed to describe the relation between convective flows near the interface in the slag layer and mass transport. Casting powders melt on the surface of the liquid metal forming a liquid slag layer. Samples taken during casting have revealed convective flows in the flux layer and mass exchange with the liquid metal. Coefficients of the developed dimensionless function have been determined empirically for Ti‐transport from the interface into the flux layer.     

Thermodynamic Calculations of Melt in Melt Pool During Laser Cladding High Silicon Coatings

Based on the Miedema＇s formation heat model for binary alloys and the Toop＇s asymmetric model for ternary alloys, the formation heat, excess entropy, and activity coefficients of silicon ranging from 1 900 K to 4 100 K in the Fe-Si-C melt formed during the laser cladding high silicon coatings process were calculated. The results indicated that all values of lnγ^0Si, ε^CSi,ρ^SiSi and ρ^CSi are negative in the temperature range and these values increase as the temperature increases. And all values of ε^SiSi and ρ^Si-CSi are positive and these values decrease with increasing temperature. The iso-activity lines of silicon are distributed axisymmetrically to the incident laser beam in the melt pool vertical to the laser scanning direction. And the iso-activity lines of silicon in the front of the melt pool along the laser scanning direction are more intensive than those in the back of the melt pool. The activity of silicon on the bottom of the melt pool is lower than that in the effecting center of laser beam on the top surface of the melt pool and it may be the important reason for the formation of the silicides and excellent metallurgical bonding between the laser cladding coating and the substrate.     

Surface effects and flow conditions in small volume melts with varying sulphur content

The surface effects and flow behaviour in melts with a volume of a few cubic millimetres were investigated using 1 mm thick X5CrNi18‐9 (AISI 304) stainless steel strips after partial remelting by a TIG (tungsten inert gas) burner. In the industrially produced material the S mass content was varied between 20 and 100 ppm. The surface excess of sulphur indicates that the surface saturation was not achieved compared to the values in the Fe‐S system. The thickness of the layer with high sulphur enrichment depends on the S activity and varied between approximately 260 and 460 nm and achieves the bulk S content at a distance of approximately 1.2 μm from the surface. This layer is noticeably thinner than the diffusion boundary layer and considerably thinner than the flow boundary layer. The topography of the rapidly solidified liquid pool makes it possible, taking previously estimated temperature coefficients of surface tension into account, to explain the flow behaviour in the melt with regard to the S content and to the temperature gradients. The results obtained indicate that the shearing force caused by surface tension gradients (Marangoni effect) controls the flow conditions in small volume melts.