VGF法生长4英寸GaAs单晶固液界面形状和热应力的数值模拟研究

采用专业晶体生长数值模拟软件CrysMas,模拟了垂直梯度凝固法(VGF)生长4英寸GaAs单晶过程中的固液界面形状,发现晶体在生长过程中固液界面形状经历了由凹到凸的变化.数值模拟结果表明熔体中和晶体中的轴向温度梯度之比小于0.4时,固液界面为凸向熔体,与理论推导结果一致.模拟了晶体生长过程中固液界面附近的晶体中的热应力值,发现固液界面为平界面时晶体中的热应力具有最小值.推导计算了VGF GaAs单晶生长过程中固液界面凹(凸)度的临界值,当固液界面凹(凸)度小于该值时,晶体中的热应力低于临界剪切应力.     

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.     

含硼高硅铁液中碳的氧化规律

以含硼生铁为原料直接冶炼硼钢新工艺的关键问题是硼、硅及碳的氧化规律.利用中频感应炉,刚玉坩埚盛装试样,研究了吹氧条件下,温度为(1 723士25)K时Fe-C-Si、Fe-C-B合金熔体及含硼高硅铁液中碳的氧化规律.结果表明:对于Fe-C-Si熔体,在熔炼开始的15 min内,主要是硅氧化,其氧化率达到88%.之后,碳和硅同时氧化,碳氧化呈线性规律,熔炼进行25 min时,碳的氧化率为44%;对于Fe-C-B合金熔体,硼与碳同时氧化,碳的氧化规律呈线性,但其氧化速率比硼慢得多.熔炼进行27 min时,硼的氧化率已达到96%,而碳的氧化率仅为22%;对于含硼高硅铁液,在熔炼进行的40 min之前,主要是硼和硅氧化,其氧化率分别达到94%和99%.之后,碳、硼、硅同时氧化,碳氧化呈线性规律,当熔炼进行到60 min时,碳的氧化率为93%.     

硅单晶材料发展动态

概述了现代特大规模集成电路对硅单晶片的质量要求、直拉砷单晶生长工艺及晶片加工技术研究进展和硅单晶材料市场现状及发展趋势。     

电磁出钢装置中填装料对固-液界面位置的影响

 在电磁出钢系统中 ,为了提高感应加热效果以实现快速出钢 ,需将固-液界面控制在感应线圈的有效加热区内。设计了模拟钢包上水口处固-液界面测量装置,考察了上水口内在高中低碳钢的出钢温度分别为1550、1600、1620℃时,铁碳合金颗粒的成分、形状、大小对固-液界面的影响规律。结果表明：使用铸铁填装料比使用铸钢填装料时固-液界面的下移量要大,并且成分的影响随着钢液温度的升高有增大的趋势;规则球形颗粒比不规则的砂形颗粒对固-液界面位置影响要大,而且固-液界面的下移量随着填装料粒径的增大而增大;选用粒径为2.0mm的铸铁颗粒作为填充料,当出钢温度为1600和1620℃时,固-液界面位置能够进入有效加热区;当出钢温度为1550℃时,使用粒径为4.0mm的铸铁颗粒做填充料时,固-液界面位置也能够进入有效加热区。     

硫化锰与奥氏体之间半共格界面比界面能的理论计算

根据错配位错理论，提出了对钢中MnS与奥氏体之间半共格界面比理论计算方法，包括比界面能σ1，侧面上的比界面能σ2，MnS沉淀初期侧面上的比界面能σ2和平均比界面能的计算。当MnS尺寸很小时(≤100m)MnS长短轴比为5．3，当继续长大时，长短轴比值降低至1．5左右。     

喷射沉积Si-Al合金的数值模拟结果与分析

采用热辐射修正,模拟了喷射沉积Si-Al合金的凝固过程,研究了熔滴的速度、热交换作用系数、温度、熔滴冷却速度及固相分数与沉积距离的关系,讨论了辐射相修正前后熔滴的温度和固相分数的变化以及雾化压力和沉积距离对固相分数的影响.     

Relation between the Crystal Structure of 35KhGF Steel and the Viscous Flow Characteristics of the Forming Melt

The effect of the crystal structure of 35KhGF steel on the temperature dependence of the kinematic viscosity of the melt has been studied at temperatures of 1450–1780°C. The crystal structure of 35KhGF steel changes as a result of heat treatment, namely, normalizing and tempering. EBSD analysis is used to study the crystal structure of the steel. The kinematic viscosity of the liquid steel is measured by the oscillating crucible method during heating and subsequent cooling. The supercooling of the liquid metal before solidification and the activation energy of viscous flow are dependent on the heat-treatment conditions. This correlation is discussed in terms of metallurgical inheritance.     

Low-Cost Process for Silicon Purification with Bubble Adsorption in Al-Si Melt

The primary silicon and Al-Si alloy have been separated in hypereutectic Al-Si melt by the electromagnetic stirring and directional solidification processes. During the electromagnetic separation process, the behavior of a hydrogen bubble in Al-Si melt has been discussed. Furthermore, the bubble adsorption effect for the Si purification has been revealed. The results show that the bubble cavity formed in the lower part of the sample by pulling it up. The scanning electron microscope along with energy dispersive spectrometer (SEM-EDS) analysis indicated that a lot of impurities were adsorbed onto the surface of the bubble cavity that may be beneficial for the Si purification. By decreasing the pulling-up rates, the size of the bubble cavity in Al-Si alloy increased, which results in the decreasing of the impurity contents in primary silicon. In this work, the impurity content in primary silicon is 10.8 ppmw, which is obviously improved compared with the 777.57 ppmw in metallurgical silicon. It is a low-cost technology that will be a potential route for the Si purification.     

多晶硅生产不存在“高能耗、高排放”

多晶硅是信息产业和太阳能光伏发电产业的基础原材料,世界多个国家将其列为战略性材料。经过多年的努力,2005年洛阳中硅高科技有限公司在国内建成第一条产业化示范线,打破了国外多年的技术封锁和市场垄断,初步形成了一个具有战略意义的新兴产业。本文分析了多晶硅乃至整个光伏行业生产过程中的能源消耗、能源贡献以及对降低GDP能耗的贡献,分析了多晶硅清洁生产过程,以利于行业的长久健康发展。     

Φ200 mm硅单晶的生长工艺特点

在全自动拉晶条件下，讨论了拉制Φ２００ｍｍ硅单晶遇到的新问题。热场配置、工艺参数的选择、石英坩埚的选用等有了更严格的要求。合理的轴向温度梯度和径向温度梯度、低拉速、低晶转及规范的拉晶工艺是拉制大直径单晶的关键。     

工业硅生产能耗分析及节能方向与途径

以国内某工业硅生产企业的能源构成及消耗现状为基础,讨论了工业硅生产的能源消耗问题,提出了工业硅工业今后的主要节能方向和途径。     

Measurement of Solid-Liquid Interfacial Energy for Solid Zn in Equilibrium with the ZnMg Eutectic Liquid

The equilibrated grain boundary groove shapes for solid Zn in equilibrium with the ZnMg eutectic liquid were observed on rapidly quenched samples. The Gibbs–Thomson coefficient for the solid Zn has been determined to be (10.64± 0.43) × 10⁻⁸ K m from the observed grain boundary groove shapes with the present numerical model, and the solid-liquid interfacial energy for the solid Zn in equilibrium with the ZnMg eutectic liquid has been obtained to be (89.16 ± 8.02) × 10⁻³Jm⁻² from the Gibbs–Thomson equation. The grain boundary energy for the solid Zn has also been calculated to be (172.97 ± 20.76) × 10⁻³J m⁻² from the observed grain boundary groove shapes. This article is based on a presentation made in the symposium entitled ”Solidification Modeling and Microstructure Formation: In Honor of Professor John Hunt” which occurred March 13-15, 2006, during the TMS Spring Meeting in San Antonio, Texas, under the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee.     

Relationship between Thermodynamic Parameters for Mn-Fe Melt and Temperature

The carbon solubility in Mn Fe melts were measured at 1 350℃ , 1 375℃, 1 425℃and 1 450℃, and accordingly the calculated equations were obtained. By thermodynamic derivation and calculation, some relationships between thermodynamic parameters for Mn-Fe melt and temperature were obtained.     

Surface and Interface Energies of Complex Crystal Structure Aluminum Magnesium Alloys

Alloying Al with Mg can improve its structural properties but also can lead to the formation of grain-boundary precipitates of β-Mg₂Al₃ that lead to failure by intergranular fracture and corrosion. Simulating the properties of the β phase is difficult because it has a complex structure with more than 1000 atoms per unit cell. We approximate the experimental β structure by the β′ structure, which has about 300 atoms per unit cell, and we compute the fracture behavior of the material from density functional theory calculations of relevant surface and interface energies. We report also on experimental measurements of the orientation and fracture properties of the α-Al(Mg)–β-Mg₂Al₃ interface and compare them with the atomistic simulations. We have computed the surface energy of face-centered cubic α-Al with up to 10 at. pct Mg, as well as the decohesion energy of β′-Mg₂Al₃ and the interfacial decohesion energy between β′-Mg₂Al₃ and pure α-Al with geometry similar to that observed experimentally. We find that the β′-Mg₂Al₃ decohesion energy is nearly isotropic and is lower than the pure Al surface energy and the α-Al–β′-Mg₂Al₃ interface decohesion energy. This result is consistent with the experimental observations of fracture within the β phase rather than at the α-Al(Mg)–β-Mg₂Al₃ interface or within the α-Al(Mg) phase.     

如何提高NTD硅单晶少子寿命

本文简要介绍了NTD硅单晶的退火工艺,通过在一次退火工艺和二次退火升τ工艺中,引入P2O5,结果表明：晶体表面的P2O5保护层在晶体表面的吸除作用能引起晶体内缺陷和杂质的消失,使晶体的少子帮助τ及τ的合格率大幅度升高。     

Distribution of Phosphorus between CaO-CaF2 Slag and Fe-C-P Melt

SymbolList　　a(i) ———Activityofconstituentiinslag ;　　CP———Phosphatecapacityofslag ;　　eji———Interactioncoefficientofconstituentjtoconstituenti;　　f[i] ———Activitycoefficientofconstituentiinmelt;　　Km———Equilibriumconstantofreactionm ;     

直拉法硅表面层熔体流动所遵循的线性规律

本文定量地研究了硅自由表面层熔体的流动规律,用大量实验数据确立了自由表面层熔体径向流动速度与熔体纵横比(D/H)值的线性对应关系。根据这个关系可以成功地解释和处理硅单晶生长过程中的许多相关问题。