Vacuum distillation refining of metallurgical grade silicon （Ⅰ） ——-Thermodynamics on removal of phosphorus from metallurgical grade silicon

The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refining process of the metallurgical grade silicon was studied via separation coefficient of impurity phosphorus in the metallurgical grade silicon and vapor-liquid equilibrium composition diagram of Si-P binary alloy at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined. The results show that the vacuum distillation should be taken to obtain silicon with less than 10^-7 P, and the impurity phosphorus is volatilized easily by vacuum distillation in thermodynamics. Phosphorus is distilled from the molten silicon and concentrated in vapor phase.     

Thermodynamics of removing impurities from crude lead by vacuum distillation refining

A novel technique was developed to remove impurities from crude lead by vacuum distillation. The thermodynamics on vacuum distillation refining process of crude lead was studied by means of saturated vapor pressure of main components of crude lead, separation coefficients and vapor-liquid equilibrium composition of Pb-i (i stands for an impurity) system at different temperatures. The behaviors of impurities in the vacuum distillation refining process were investigated. The results show that the vacuum distillation should be taken to obtain lead from crude lead, in which Zn, As and partial Sb are volatilized at lower temperature of 923-1023 K. Lead is distilled from the residue containing Cu, Sn, Ag and Bi at higher temperature of 1323-1423 K, but the impurity Bi is also volatilized along with lead and cannot be separated from lead.     

高纯金属镝的制备

为制备高纯度稀土金属Dy以适应高科技发展的需求,在钙热一次还原法生产的Dy-4,Dy-8的基础上,用中频感应炉进行二次精炼和真空蒸馏,并对工艺进行优化选择得出,二次精炼温度为1450℃,保温40min最适宜;真空蒸馏1500℃～1530℃,保温8h最佳。用此工艺所制备的金属Dy的纯度超过国标高纯度Dy-1和Dy-2的要求,接近国外高纯Dy的先进技术指标。     

Ti含量对Ni-14Cr-10P-xTi焊膏连接C/C复合材料组织及性能的影响

将不同质量分数的钛粉加入Ni-14Cr-10P合金粉末中,再配合高分子聚合物制得膏状Ni-14Cr-10P-x Ti活性钎料,用制得的焊膏钎焊C/C复合材料,然后测试了钎焊接头的剪切强度,通过扫描电子显微镜、能谱分析仪、电子探针显微分析仪等对钎焊接头界面组织特征进行分析。结果表明:活性元素Cr、Ti与C/C复合材料表面的C反应而起到表面改性的作用,使得钎料能在C/C复合材料表面润湿、填缝。随着Ti元素加入量的增加,钎焊接头剪切强度先增加再降低。Ti质量分数为1%时,TiC呈颗粒状弥散分布,使得钎料层强化,接头剪切强度增加;当Ti增加到3%时,在界面处形成了连续的Cr_3C_2/TiC脆性材料层,接头剪切强度下降;Ti质量分数达到5%时,Ti与Cr_3C_2反应使得梯度界面层消失,界面物质热膨胀系数差异增大,残余热应力增加,同时Ti与Ni、Cr形成的金属间化合物增加并集中分布在钎料层中,导致接头剪切强度急剧下降。     

Residual stresses and strains in orthogonal metal cutting

The finite element method is used to simulate and analyze the orthogonal metal cutting process under plane strain conditions, with focus on the residual stress and strain fields in the finished workpiece. Various modeling options have been employed. The frictional interaction along the tool-chip interface is modeled with a modified Coulomb friction law. Chip separation is modeled by the nodal release technique based on a critical stress criterion. Temperature-dependent material properties and a range of tool rake angle and friction coefficient values are considered. It is found that while thermal cooling increases the residual stress level, the effects of the rake angle and the friction coefficient are nonlinear and depend on the range of these parameters. The predicted residual stress results compare well with experimental observations available in the literature.     

Si3N4/AgCu/TiAl钎焊接头界面结构及性能

采用AgCu非活性钎料实现了Si3N4陶瓷与TiAl基合金的钎焊,确定接头的典型界面组织结构为:TiAl/Ti3Al+Ti(s,s)/AlCuTi/Ag(s,s)+AlCu2Ti/Ti5Si3+TiN/Si3N4陶瓷。钎焊过程中,活性元素Ti从TiAl母材溶解到钎料中与Si3N4陶瓷发生反应润湿,实现了TiAl与Si3N4陶瓷的连接。随着钎焊温度的升高及保温时间的延长,靠近Si3N4陶瓷的TiN反应层厚度增加,Ag基固溶体中弥散分布的AlCu2Ti化合物聚集长大成块状,导致接头性能下降。当钎焊温度T=860℃,保温时间为5min时接头抗剪强度达到最大值124.6MPa。基于反应热力学及动力学计算TiN层反应激活能Q约为528.7kJ/mol,860℃时该层的成长系数KP=2.7×10-7m/s1/2。     

活性金属部分瞬间液相连接氮化硅陶瓷的研究

采用Ti/Cu/Ti多层中间层在1273 K温度下进行氮化硅陶瓷部分瞬间液相连接,考察了保温时间对连接强度的影响,并对连接界面进行了SEM,EPMA和XRD分析.结果表明,通过Cu-Ti二元扩散促使液相与氮化硅发生界面反应,形成Si3N4/TiN/Ti5Si3+Ti5Si4+TiSi2/TiSi2+Cu3Ti2(Si)/Cu的梯度层.保温时间影响接头反应层厚度,从而影响接头的连接强度根据活性金属部分瞬间液相连接陶瓷的界面行为,建立了活性金属部分瞬间液相连接陶瓷的理论模型.该模型较好地解释了Ti/Cu/Ti和Ti/Ni/Ti连接氮化硅陶瓷的异同点和连接工艺参数的选择.     

稀土金属提纯方法与研究进展

对各种提纯稀土金属方法的机理进行了阐述,包括真空熔炼、电解精炼、真空蒸馏/升华、熔盐萃取、区域熔炼、固态电迁移、电化学脱氧、外吸气剂法、等离子体熔炼(通氢气或通氩气)等。对研究现状和提纯效果进行了总结。杂质去除需采用多种手段结合,同时提升装备水平,以达到提高提纯效果、降低成本、缩短生产周期的目的。     

Ti/Al固相-固相原位反应过程研究

利用超声固结试验制备Ti/Al金属层状复合材料,以光学显微镜观察了材料的微观形貌。采用固相-固相反应方式进行原位反应获得了体积分数不同的层状复合材料,通过EDS以及XRD对Ti/Al原位反应产物进行能谱分析,确定了反应产物的相组成。采取SEM测量反应产物Al_3Ti的层间厚度,建立Al_3Ti的生成量与反应时间的关系。结果表明,在Ti/Al层状复合材料原位反应过程中,当Al未反应完全时,金属间化合物Al_3Ti是唯一产物。在原位反应初期,反应产物积累慢,随着反应时间的推移,反应产物增多且增长速率逐渐增快,反应产物与反应时间呈幂指数函数的关系。     

THE EFFECT OF POWERFUL OXYGEN EVOLUTION METAL-OXIDE ON THE ELECTROOXIDATION OF METHANOL

1. IntroductionThe direct methanol fuel cell (DMFC) is a promising power source for electric vehicles[1--4] 5but its development is hampered by the large anodic overvoltage. For methanol, six electrons must be exchanged for complete oxidation and the oxidation kinetics is inherentlyslowed, so some illtermediates are formed during methanol oxidation. In fuel cells, as theplatinum alone is not a sufficiently active methanol oxidation electrocatalyst, Pt--basedmultimetallic catalysts earn the a…     

电子束熔炼提纯钨中杂质脱除静态动力学研究

研究了电子束熔炼提纯钨过程中典型杂质的脱除,考察了电子束熔炼提纯钨的可行性,对电子束熔炼过程中的除杂动力学进行了分析,并确定了110、130、250 kW功率条件下杂质Fe、Si、Ti的脱除速率控制机制。结果表明:除Mo外,电子束熔炼对基体钨中各种杂质均有不同程度的脱除,其脱除率与饱和蒸气压差存在对应关系;通过分析并结合电子束熔炼实验,确定了Si、Fe、Ti在110 kW时的传质系数分别为0.21、0.56、0.11×10-4 m/s,在130 kW时的传质系数分别为0.83、3.04、1.78×10-4 m/s,在250 kW时的传质系数分别为0.36、2.37、1.48×10-4 m/s,表明其脱除速率控制机制均为液/气界面中的扩散。     

Purification of Alkaline Earth Metals

The study demonstrates that alkaline earth metals can be sublimed or distilled to give metal of very high purity. The metallic impurities are the most easily separated although the other alkaline earth metals require a fractional sublimation. The interstitial elements 0, N and C can be reduced to very low levels if entrainment is prevented by subliming or distilling under a small torr pressure of an inert gas. Hydrogen transfers to the product in either distillation or sublimation and must be removed by vacuum traction from a Ta capsule. Alkaline earth metal purification by sublimation and distillation started in 1960 to supply pure Ca, Ba and Sr for phase equilibria studies and was expanded to provide high purity Ca for metallothermic preparation of very pure rare earth metals as described by Spedding et al.1 The objectives were to produce metals of the lowest possible interstitial solute concentration with a high yield and in a convenient form for handling in inert atmosphere gloveboxes. Enhance d process reliability with regard to product purity also eliminates expensive and time-consuming chemical analyses on each batch of metal.     

VARIATIONAL CALCULATION OF THERMODYNAMIC PROPERTIES OF SUPERCOOLED LIQUID METALS

By means of Gibbs-Bogoliubov (GB) thermodynamic variational calculation,thethermodynamic properties of the supercooled liquid metals,such as the 3rd family elementsAl,Ga and Tl and transition metal Ti were calculated using the hard-sphere (HS) system asreference.The values of mean atomic volume,Helmholtz free energy,internal energy andentropy as well as specific heat at constant volume,isothermal bulk modulus,thermal expan-sion coefficient and specfic heat under constant pressure were evaluated.The glass transitiontemperature,T_g,is easily obtained from the C_p-T plot.The glass forming ability for metalcan be predicted from T_g/T_m,which is in agreement with the experimental results.     

In-situ preparation,modulation and mechanism of refractory metal carbide gradient coating

TiC, ZrC and TaC modified layers were in-situ prepared on graphite matrix by chemical vapor infiltration method with metal salts as the activator. Taking the TiC modified layer as an example, through thermodynamic calculation and experiment, the thermal decomposition process of raw materials (Ti/K₂TiF₆) was analyzed, the formation mechanism of TiC was determined, and the distribution of TiC modified layer was modulated. The results show that activator K₂TiF₆ has higher decomposition temperature than NH₄Cl, which is conducive to improving the utilization rate of raw materials in the gas infiltration process. Increasing the content of Ti powder can increase the concentration of reaction gas and contribute to the formation of TiC modified layer. When the molar ratio of Ti to K₂TiF₆ is 3:1, the surface thickness and infiltration depth of TiC are 5.42 and 136.24 μm, respectively. Increasing the reaction temperature can improve the rate of in-situ reaction and the thickness of TiC surface layer. When the experimental temperature rises to 1600 °C, the TiC surface layer thickness increases to 20.27 μm.     

类蝴蝶翅膀表面微纳结构的制备及其疏水性

在金属表面构筑微纳米粗糙结构后以低表面能物质修饰,可以获得超疏水的金属表面,对实现防水、防腐及表面自清洁等功能具有重要的意义。以钛片为基底,利用简单易行且低成本的喷砂-酸蚀法,对其进行粗糙化处理,并使用低表面能物质氟碳树脂进行表面改性,获得了超疏水性表面。测量了试样表面与蒸馏水的静态接触角,将试样置于空气、模拟海水、质量分数为3%的NaOH和HCl溶液中进行了耐环境测试,观察了试样表面的微观形貌。结果表明:在光滑的钛基底上用氟碳树脂修饰后,得到的疏水表面接触角仅为103°;而钛片表面经喷砂-酸蚀后,再利用氟碳树脂进行疏水化修饰,得到与水接触角为156°的超疏水表面。经表面粗糙化处理和低表面能物质修饰后得到的钛基底上形成了类蝴蝶翅膀表面微纳结构的蜂窝状超疏水表面,具有优异的耐环境性和良好的自清洁效果。     

钛对气保护药芯焊丝熔敷金属组织韧性的影响

通过在气保护药芯焊丝的药粉中直接添加不同量的钛铁,在富氩和CO_2保护气焊接条件下,将钛过渡到熔敷金属中,分析钛对熔敷金属组织韧性的影响.结果表明,运用si-Mn-Ti联合脱氧的药芯焊丝,熔敷金属中生成的夹杂物主要是MnO-TiO_x-Al_2O_3-SiO_2形成的复合氧化物.随着焊丝中钛含量的增加,所形成的夹杂物中Ti元素的含量增加,且夹杂物的尺寸更加集中在O.3～2.0μm范围,对熔敷金属中生成针状铁素体组织的促进作用增强,熔敷金属韧性得到改善;同时,进入熔敷金属组织中的固溶钛,提高了组织的强度和硬度,但过多的固溶钛则恶化组织的韧性.

Abstract：

The effects of Ti content on microstrueture characteristic of deposited metal with flux cored wire were investigated with different contents of Ti-Fe powder under the protection of CO_2 and Ar + 20%CO_2. The results show that the inclusions in deposited metal are mainly complex oxides composed of MnO-TiO_x-Al_2O_3-SiO_2 in SiMn-Ti deoxidized flux cored wire. With the increasing of Ti content in flux cored wire, the content of Ti in the inclusions increases, and most of inclusions are in the range of 0.3～2.0 lan in diameter,which promote the formation of acicular ferrite, thus those contribute to the increased toughness of deposited metal. Dissociative Ti can improve the intensity and the rigidity of microstructure, but it does worse to the microstructure toughness when too much dissociative Ti gets into the microstructure of deposited metal.     

Theoretical analysis of bubble nucleation in GASAR materials

1　INTRODUCTIONPorousmaterialscanbeproducedbyusinganov elmethodcalledGASARdevelopedintheDne propetrovskMetallurgicalInstitute (DMI )ofUkraine[1] .Mostmetal hydrogenbinarysystemshaveaeutecticdecompositionsimilartotheclassicaleutecticsystem .Thesemetalscanbemelted ,saturat edwithhydrogen ,andthendirectionallysolidified ,asshowninFig .1[2 ] .TheporosityofthesolidifiedGASARmaterialscanbevariedthroughprocessvari ablessuchaspressure ,rateanddirectionofcoolinginaprocessbasedongas solideut…     

Reaction layer characterization of the braze joint of silicon nitride to stainless steel

This investigation studies the role of titanium in the development of the reaction layer in braze joining silicon nitride to stainless steel using titanium-active copper-silver filler metals. This reaction layer formed as a result of titanium diffusing to the filler metal/silicon nitride interface and reacting with the silicon nitride to form the intermetallics, titanium nitride (TiN) and titanium suicide (Ti ₅Si₃). This reaction layer, as recognized in the literature, allows wetting of the ceramic substrate by the molten filler metal. The reaction layer thickness increases with temperature and time. Its growth rate obeys the parabolic relationship. Activation energies of 220.1 and 210.9 kj/mol were calculated for growth of the reaction layer for the two filler metals used. These values are close to the activation energy of nitrogen in TiN (217.6 kj/mol). Two filler metals were used in this study, Ticusil (68.8 wt% Ag, 26.7 wt% Cu, 4.5 wt% Ti) and CB4 (70.5 wt% Ag, 26.5 wt% Cu, 3.0 wt% Ti). The joints were processed in vacuum at temperatures of 840 to 900 °C at various times. Bonding strength is affected by reaction layer thickness in the absence of Ti-Cu intermetallics in the filler metal matrix.     

Effects of Ti on the Brazability of Zn-22Al-xTi Filler Metals as Well as Properties of Cu/Al Brazing Joints

设计并采用Zn-Al-Ti系列钎料对Cu和Al异种金属实施了钎焊,并对Zn-22Al-xTi/Cu界面处的相组成和金属间化合物形貌进行了分析。结果表明：在Zn-22Al中添加0.01%至0.05%的Ti可以显著细化钎料组织,而且Zn-22Al-0.03Ti在Cu基板上的铺展面积比Zn-22Al高出60.4%,但Ti的添加会提高Zn-22Al钎料的熔点和熔化区间。另外,在钎料中添加微量的Ti可以优化Cu/Al接头中Cu侧界面化合物的组织并减小其厚度。相比Zn-22Al钎料,Zn-22Al-0.03Ti钎焊所得Cu/Al接头强度要高出13.4%,而且接头断裂位置由化合物层转移至钎料内部。X射线衍射结果显示,钎焊过程中有CuAl2,Cu9Al4,CuZn 3种化合物产生于钎料与Cu基板界面处     

Ostwald ripening and grain growth in Ti(C,N)-based cermets during liquid phase sintering

After liquid phase sintering, core-rim microstructure occurs in the grains of Ti(C,N)-based cermets. The mechanisms of the microstructural evolution during different sintering stages were investigated here. Our theoretical analyses show that the rim thickness of a grain is relatively independent of its initial radius when rim formation is dominated by Ostwald ripening during dissolution-reprecipitation stage, whereas it increases linearly with its initial radius when grain growth during subsequent cooling stage is the dominant mechanism. A geometric analysis via cross-sectioning technique is developed to identify dominant rim formation mechanism. Experiments with Ti(C,N)-based cermets show that rim formation is dominated by grain growth at low sintering temperatures and by Ostwald ripening at sufficiently high sintering temperatures.