Interface reactions and reaction synthesis of a high temperature composite system

Reactive diffusion during isothermal annealing was examined in a Ti−Al−Si temary system. When a TiAl/TiSi₂ reaction couple was annealed at 1373 K for 200 h, the product phase sequence was observed as TiAl/TiAl₂/Ti₂Al₅/TiAl₃/Ti₅Si₄/TiSi/TiSi₂, in which the integrated diffusion coefficient of Ti₂Al₅ showed the lowest value. A Ti-rich Ti₅Si₃ phase appeared when an additional Ti flux was provided between the TiAl/TiSi₂ reaction. The growth kinetics for both the TiAl/TiSi₂ (direction reaction) and TiAl/Ti/TiSi₂ reactions (Ti biased reaction) were identified, and a comparison of the morphology of the product phases was provided. The chemical potential variation and mass balance exhibited guidance in predicting the diffusion pathway during isothermal annealing. It appears that a biasing reaction (i.e., controlling component flux) is an effective tool for the phase selection and morphology changes during isothermal annealing.     

铁基和镍基高温合金的相变规律与机理

评述了中国科学院金属研究所高温合金和金属间化合物研究组50年来对铁基和镍基高温合金相变的主要研究结果:包括凝固过程中发生的相变,如L→γ+Laves,L→γ+γ',L→γ+M3B2;沉淀反应,过饱和y固溶体中析出GCP相、碳化物和硼化物、硅化物、TCP;γ'相中的沉淀析出和MC碳化物的分解反应.     

Diffusion reaction behaviors of U-Mo/Al dispersion fuel

The uranium (U)-molybdenum (Mo)/aluminum (Al) dispersion fuel that is currently under development for high-performance research reactors has shown complicated diffusion reaction behavior between the U-Mo particles and the Al matrix. Diffusion reactions in U-Mo/Al dispersion fuels were characterized by out-of-pile annealing tests and in-pile irradiation tests in the HANARO research reactor. The effect of the addition of a third element such as silicon (Si), Al, or zirconium (Zr) to U-Mo fuel, and the addition of Si to the Al matrix on the diffusion reaction were also investigated. The growth rate and activation energy for the reaction phases of U-Mo/Al dispersion fuels were obtained. The effect of alloying a small amount of a third element in U-Mo and of Si in the Al matrix on diffusion reaction kinetics was negligible in annealing tests conducted at ∼550 °C. γ phase stability in the U-Mo alloy was enhanced by the addition of 0.1 to 0.2 wt.% Si. The Si accumulated in the interdiffusion layer of U-Mo/Al-Si dispersion fuel annealed at ∼550 °C, whereas Zr migration to the interdiffusion layer of U-Mo-Zr/Al was negligible. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.     

原位冶金反应氧化钨制备碳化钨

在密闭和开放两种环境下,采用原位合成法在采掘机截齿齿体(20CrMnTi)的齿顶孔内制备钨基硬质合金,研究了原位反应的热力学原理、产物的微观组织、成分、相组成及其形成机理。结果表明:在非平衡快速凝固条件下,凝固组织内应力较大,内部有裂纹出现。在相对密闭的环境下反应,生成的产物是W、W2C、Al2O3。W或W2C与Al2O3的界面清晰,产物多孔且硬度高。采用电弧为外加热源,开口情况下WO3大量汽化,导致钨元素大量损失,产物中钨元素的含量很低,几乎没有生成W2C和WC。最后,文中列举了解决这些问题的几种改进措施。     

高能球磨诱发Al,Si/CuO固态还原反应动力学

采用差热分析（DTA）和X射线衍射（XRD）技术研究了球磨燃烧反应发生前不同球磨时间下Al／CuO和Si／CuO体系反应动力学和微观结构变化。结果表明：高能球磨诱发燃烧反应的发生是粉末颗粒细化和均匀化与局部反应、球磨介质污染两方面竞争的结果。球磨时CuO的缺陷形成速率或者氧离子从CuO点阵中通过短路扩散路径向反应界面迁移是球磨诱发Al／CuO燃烧反应的控制步骤。     

超声化学原位合成Al2O3（p）/Al纳米复合材料的组织及其机理（英文）

采用超声化学原位反应,以Al-K2ZrF6-Na2B4O7为反应体系,制备Al2O3(p)/Al纳米复合材料。利用扫描电镜和透射电镜,研究高能超声对复合材料组织和颗粒收得率的影响及加入K2ZrF6对反应过程以及增强颗粒与铝基体的界面的影响。X射线衍射(XRD)、扫描电镜(SEM)与透射电镜(TEM)结果表明:所制备的复合材料增强颗粒为Al2O3,Al2O3颗粒在基体中分布均匀,其形貌为近球形,尺寸20~100nm,界面干净且无界面产物。利用经过二次开发的Image-J软件对Al2O3颗粒收得率进行分析,结果表明,Al2O3颗粒收得率随着超声功率的增大呈现出先增大后减小的变化规律。当超声功率达到0.4kW时,颗粒分布最好且数量最多。并对其反应机理也进行了探讨。     

基于产物分析的铝/铁氧化物纳米复合材料的铝热反应机理(英文)

采用溶胶-凝胶法分别对纳米Al和微米Al进行表面包覆,制备nano-Al/xero-Fe2O3和micro-Al/xero-Fe2O32种复合材料,并对它们的微观结构和物相进行表征。结果表明,纳米Al和微米Al表面均被约20 nm的无定形纳米粒子致密包覆;包覆物中的铁氧比与Fe2O3中的铁氧比大致相当。对2种纳米复合材料以及4种相对应的简单混合物(nano-Al+xero-Fe2O3、nano-Al+micro-Fe2O3、micro-Al+xero-Fe2O3和micro-Al+micro-Fe2O3分别进行DSC分析。对于采用纳米Al作燃料的铝热剂,nano-Al/Xero-Fe2O3、nano-Al+xero-Fe2O3和nano-Al+micro-Fe2O3三者的热谱图没有明显差别;对于采用微米Al作燃料的铝热剂,micro-Al/xero-Fe2O3的反应峰温度较micro-Al+xero-Fe2O3和micro-Al+micro-Fe2O3的分别提高了68.1°C和76.8°C。另外,将4种铝热剂(nano-Al/xero-Fe2O3,nano-Al+micro-Fe2O3,micro-Al/xero-Fe2O3和micro-Al+micro-Fe2O3)同时从室温加热至1020°C,对660°C和1020°C时的产物进行XRD分析。从图谱中共检测出Fe、FeAl2O4、Fe3O4、α-Fe2O3、Al、γ-Fe2O3、Al2.667O4、FeO和α-Al2O3共9种晶体物质。据此推测了可能的反应方程,并以最小自由能原则推出了每种样品最可能的反应过程。     

氨甲苯酸注射液引起溶血反应原因的实验研究

目的: 研究氨甲苯酸注射液引起溶血反应的原因。方法: 按照《中国药典》2010年版二部附录规定测定引起溶血反应的氨甲苯酸注射液及其原料的pH值和摩尔渗透压,考察其引发溶血反应的原因。结果: 氨甲苯酸注射液引发溶血反应的原因与其pH值范围相关,与其摩尔渗透压无关。结论: 产品成品的溶液pH值控制在该品种规定的 4.3～4.5 之间即可达到保证该品种溶血试验符合规定的目的,同时还可避免可能出现的不良反应。     

Al／CuO的高能球磨固态反应

系统研究了Ａｌ／ＣｕＯ的高能球磨固态反应。对Ａｌ含量在２０％～８５％范围内的Ａｌ／ＣｕＯ进行高能球磨,采用Ｘ射线衍射进行物相分析,并对Ａｌ含量分别为２０％和７５％的试验分析了物相随研磨时间的变化,做了差示扫描量热（ＤＳＣ）分析,对比研究了固态还原反应与固态复合反应过程的异同。结果表明,Ａｌ含量不超过２０％时仅发生单纯的还原反应;当Ａｌ含量从２０％分别增加到３５％,５７％,７０％和８５％时,反应为还原与合成共存的复合反应,产物依次为Ｃｕ９Ａｌ４,ＣｕＡｌ２及Ａｌ（Ｃｕ）固溶体和Ａｌ２Ｏ３的复合颗粒。     

面向多功能非贵金属电催化剂的构筑和微尺度解析

相对于贵金属电催化剂制作成本高、地球储量稀少、电化学稳定性低等缺点,制备廉价、能量转换效率高、使用寿命长、环境友好的非贵金属电催化剂是推动能源存储和转换技术快速发展的重要途径.根据电催化过程中电催化析氢反应(Hydrogen Evolution Reaction,HER)、电催化析氧反应(Oxygen Evolution Reaction,OER)及氧还原反应(Oxygen Reduction Reaction,ORR)这三个重要反应类型,概述了水裂解和燃料电池的电化学反应机制,同时归纳了单功能电催化剂、双功能电催化剂、多功能电催化剂及其他电化学材料的设计与制备方法、相互关系和各自功能特点.借助先进的电子显微技术,如扫描电子显微镜、原子力扫描电子显微镜、透射电子显微镜、X射线能谱仪、电子能量损失谱仪等对其微观结构进行表征,重点对其表面形貌、结构、内部成分、元素分布等相关信息进行解析.从提供更丰富的缺陷空位、潜在活性位点、优化界面相互作用、增大电化学比表面积、形成协同效应等方面,分析其在降低成本的同时,提高电催化剂的电导率、增强稳定性的相关机理,以期为非贵金属电催化剂的研究和推广应用提供新策略.     

铸型用焓变涂料材料的研究

对几种物质化学反应过程中的温度变化进行定性实验,选出其中效果较好的几组物质,进行差热分析(DTA),定量测出这些物质的化学反应温度。由焓变涂料效果测试实验得出,碳酸钙、碳与氧化锌、碳与碳酸钠涂料是3种吸热涂料,其中碳酸钙涂料吸热效果最好;碳酸钙与镁、氧化铁与镁、氧化铁与锌涂料是3种放热涂料,其中前两者效果更好。     

Interfacial Reactions between Cu-Zr filler metal and alumina and kinetics of reaction layer growth

The interfacial reactions and kinetics of the reaction layer growth in Cu-Zr/A1₂O₃ system were investigated and compared with those in Cu-Ti/Al₂O₃ system. Therrnodynamic analysis showed that the interfacial reaction can proceed until the activity of aluminum in the Cu-5 at.% Zr filler metal reaches about 0.27 at 1373 K. Growth of reaction layer, ZrO₂, was controlled by the diffusion of oxygen through ZrO₂ layer. The activation energy for ZrO₂ growth was 126 kJ/mol. Instead of using a complex redox reaction, a simple oxidation model between reactive metal and oxygen was found to adequately describe the reaction layers growth in ceramic/metal systems. The parabolic rate constant could be expressed in terms of oxygen vacancy concentration at the reactive metal/reactive metal oxide interface. The slower growth of TiO, in comparison with ZrO₂, can be rationalized using the parabolic rate constant. The lower diffusion coefficient of oxygen vacancy and a less negative free energy change of TiO formation have a dominant effect over the higher oxygen vacancy concentration at the Ti/TiO interface which resulted in slower TiO growth.     

原位冶金反应氧化钨制备碳化钨的研究

在密闭和开放两种环境下,采用原位合成法在采掘机截齿齿体（20CrMnTi）的齿顶孔内制备钨基硬质合金,研究了原位反应的热力学原理、产物的微观组织成分、相组成及其形成机理等。结果表明：在非平衡快速凝固条件下,凝固组织内应力较大,内部有裂纹出现。在相对密闭的环境下反应,生成的产物是 W、W2C、Al2O3。W 或 W2C 与Al2O3的界面清晰,产物多孔且硬度大。采用电弧为外加热源,开口情况下 WO3大量汽化,导致钨元素大量损失,产物中钨元素的含量很低,W2C 和 WC 几乎没有生成。同时列举了解决这些问题的措施。     

Serum effect on the electrochemical behaviour of titanium, Ti6Al4V and Ti6Al7Nb alloys in sulphuric acid and sodium hydroxide

The corrosion behaviour of cp titanium Ti6Al4V and Ti6Al7Nb alloys is investigated in 2 M sulphuric acid and 2 M sodium hydroxide with and without additions of bovine serum in order to get an insight into the effect of a biological electrolyte on the active corrosion of widely used metallic implants. Ti6Al7Nb alloy shows the highest corrosion resistance in 2 M sulphuric acid, whereas it is the least corrosion-resistant in 2 M sodium hydroxide. Bovine serum inhibits the hydrogen evolution as well as the anodic dissolution reactions in both sulphuric acid and sodium hydroxide. However, the cathodic efficiency of serum in sodium hydroxide is significantly higher than in sulphuric acid. Besides, the results suggest that serum forms a 2-D adsorption layer on the implant materials. Additionally, the surface coverage in sodium hydroxide is ca. 90%, while in acidic solutions only ca. 40%.     

Sm,Nd共掺CeO_2固体电解质的制备与性能

分别用固体反应法、溶胶凝胶自蔓延燃烧法和共沉淀法制备了Sm, Nd共掺CeO_2粉体,将粉体压制烧结制成固体电解质.通过XRD和SEM等仪器对该复合电解质的相组成和微观形貌进行了表征,并测量了高温直流电导率.结果表明,3种方法制备的烧结体致密度良好,相对密度都达到了94%以上.电导率达到0.01 S/cm时3种制备方法对应的烧结温度分别为770、639和621 ℃.     

Interfacial reaction between cubic boron nitride and Ti during active brazing

Thermodynamic and reaction process analyses were performed to understand the joining characteristic during high temperature brazing between cubic boron nitride (CBN) grit and a silver-base filler alloy containing Ti as an active element. Experimental information on the microstructure of the brazed joint, the composition of the interface, and the shape of the compounds formed on the surface of the grit was obtained by scanning electron microscopy, energy-dispersive x-ray, and x-ray diffraction. The results indicate that Ti in the molten filler alloy facilitated good wetting between the solid CBN crystals and braze filler alloy. The transition layer formed by the interaction of TiN and TiB₂ was one of the key factors in joining the CBN and steel substrate.     

Reaction mechanism of roasting Zn2SiO4 using NaOH

The reaction kinetics of roasting zinc silicate using NaOH was investigated. The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows: molar ratio of NaOH to Zn₂SiO₄ of 16:1, reaction temperature of 550 °C, and reaction time of 2.5 h. In order to ascertain the phases transformation and reaction processes of zinc oxide and silica, the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures. The final phases of the specimen roasted at 600 °C were Na₂ZnO₂, Na₄SiO₄, Na₂ZnSiO₄ and NaOH. The reaction kinetic equation of roasting was determined by the shrinking unreacted core model. Aiming to investigate the reaction mechanism, two control models of reaction rate were applied: chemical reaction at the particle surface and diffusion through the product layer. The results indicated that the diffusion through the product layer model described the reaction process well. The apparent activation energy of the roasting was 19.77 kJ/mol.     

陶瓷壳型面层材料与Ti46Al1B阀门铸件的界面反应

分别采用Al2O3与Y2O3为壳型面层材料,离心铸造了Ti46Al1B(原子分数,%)合金阀门铸件,通过SEM,XRD以及气体分析等方法,确定壳型内表面物相组成、铸件与壳型反应层厚度以及合金的进氧情况,分析了壳型材料与Ti46Al1B合金的反应机理.结果表明,Y203和A120s壳型与合金的反应层厚度分别约为90和170 pm,使用Y203壳型时铸件进氧少,其热力学稳定性好于Al2O3壳型,与热力学计算结果相符.Y2O3壳型比Al2O3壳型更适合铸造Ti46Al1B阀门.     

高投料量下炼铜闪速炉内熔炼过程的数值模拟

以FLUENT 6.3为计算平台,建立了铜闪速炉熔炼过程数值模型,并针对高投料量下反应塔气粒两相变物理场信息分布变化特点展开仿真研究。结果表明:工艺风入炉后迅速膨胀,并在反应塔中心形成轮廓明显的主体气流柱;主体气流柱内外的温度和氧浓分布梯度变化较大;局部低温出现在精矿喷嘴下方,而高温反应核心区域则下移至反应塔中下部。综合多场耦合仿真结果可知:高投料量条件下精矿粒子与反应配风之间混合力度欠佳是造成高投料量反应塔内熔炼过程反应效率降低的主要原因。     

相图计算在电子材料焊接中的应用

焊料与基体的界面反应对高性能电子材料焊接接头的力学性能和可靠性都有着很重要的影响。把焊接过程分为界面反应和剩余焊料凝固两个过程进行讨论，在相图热力学的基础上，通过计算亚稳相图、比较界面处局部平衡时各相形成驱动力大小，预测了Sn-3．5％Ag／Cu、Sn-25％Ag／Cu和Sn-3．5％Ag／Ni扩散偶界面反应过程中的中间相形成序列；同时利用Scheil—Gulliver凝固模型模拟了Sn-25％Ag／Cu体系中过剩焊料的非平衡凝固过程，预测了焊料在随后冷却过程中的相演变信息。计算预测的结果与前人的实验结果吻合很好。