添加0.1%Ce对Sn-3.0Ag-0.5Cu焊料与铜基板间的金属间化合物的影响

研究了Sn-3.0Ag-0.5Cu-xCe（x=0,0.1%）焊料合金与Cu基板250℃钎焊及170℃恒温时效时对基体和界面金属间化合物（IMC）的形成与长大行为的影响。结果发现,在Sn-3.0Ag-0.5Cu焊料中添加0.1?后,能够抑制基体和钎焊界面反应及随后时效过程中IMC的形成与生长。焊点最初的界面IMC为Cu6Sn5,时效5 d之后,该两钎焊体系中均发现了Cu3Sn薄层的生成,且随着时效时间的增加,各IMC层厚度有明显的增加趋势。与Sn-3.0Ag-0.5Cu/Cu焊点相比,Sn-3.0Ag-0.5Cu-0.1Ce/Cu钎焊体系焊点界面处的IMC层更为平整和细薄。时效过程中,界面IMC的形成与长大受扩散机制控制。     

金属间化合物电催化剂Pt1Te1/XC-72的制备及其电催化氧化甲醇性能

以氯铂酸和亚碲酸钠为前驱体,采用两步法在醇水体系下得到负载型Pt1Te1金属间化合物前驱体,通过热处理得到负载型金属间化合物电催化剂Pt1Te1/XC-72.采用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）、电子能谱（EDS）和循环伏安方法（CV）对催化剂进行表征.结果表明：所得产物呈有序金属间化合物Pt1Te1结构,平均粒径4.5nm,在碳载体上具有很好的分散性;负载型金属间化合物电催化剂Pt1Te1/XC-72具有较高的电催化氧化甲醇活性,其优秀的催化氧化甲醇活性与Pt形成金属间化合物后所带来的几何及电子结构改变密切相关.     

金属间化合物热容计算的新经验公式

金属间化合物热容计算的新经验公式陈锋杨章远许志宏（中国科学院化工冶金研究所计算机化学开放实验室北京１０００８０）金属间化合物的热容是一个应用很广的物理性质。然而实验值的获取非常有限。因此有必要建立一些估算模型。本文通过对已有金属间化合物热容实验值系统...     

金属间化合物电催化剂在氢电转换器件应用中的研究进展

人类对可持续能源的高度重视,使得绿色环保的氢能成为研究热点。能量转换和存储技术（如燃料电池和电解水）可实现氢能源和电力的相互转换,但实现这些技术的前提是需要开发高效稳定的催化剂。结构有序的金属间化合物具有确定的组成和可调控的几何效应和电子效应的优势,已被探索作为能量转换和存储技术的有效电催化剂,金属间化合物表面均匀的活性位点分布也有利于研究催化剂活性和结构之间联系（即构效关系）的理想模型。本综述首先介绍了氢电转换装置催化剂所面临的挑战以及金属间化合物在电催化中的优势,其次从活性和稳定性的角度重点论述金属间化合物在氢电转换装置中的研究进展,最后总结并展望了金属间化合物电催化剂未来的发展前景。     

树状大分子/金属（化合物）纳米复合材料*

本文综述了一类新的有机/无机杂化材料——树状大分子/金属（化合物）纳米复合材料的研究进展。该杂化纳米材料由树状大分子内或树状大分子间螯合金属离子通过还原生成相应的零价金属纳米粒子或与阴离子反应生成金属化合物的方法制备。其中树状大分子内复合物粒子体积与原树状大分子内负载的金属离子数量有关,树状大分子间复合物粒子体积与树状大分子的浓度和代数有关。     

Pr(Ⅲ)离子在LiCl-KCl熔体中Bi膜W电极上的电化学行为

采用循环伏安、方波伏安、计时电位和开路计时电位等电化学方法研究了Pr（Ⅲ）离子在LiCl-KCl-BiCl₃熔体中W电极上的电化学行为。循环伏安和方波伏安的研究表明,Pr在预先沉积的Bi膜电极上发生欠电位沉积是由于生成了Pr-Bi金属间化合物,导致Pr（Ⅲ）在Bi膜电极上的还原电位比在W电极上还原电位更正。从开路计时电位曲线可以观察到两相共存的Pr-Bi金属间化合物的两个平台。利用开路计时电位计算了723-873 K温度范围内Pr在Pr-Bi合金中的活度和偏摩尔Gibbs自由能以及Pr-Bi金属间化合物的生成Gibbs自由能。通过恒电位电解,在液态Bi电极上得到了Pr-Bi合金,并采用X射线衍射（XRD）和扫描电子显微镜（SEM）附带能量散射谱（EDS）对样品进行了表征,结果表明所得到的Pr-Bi金属间化合物为PrBi₂和PrBi。     

聚丙烯腈在锂金属电池电解质中的应用

随着便携式电子设备、电动汽车和智能电网等快速发展，人们对高能量密度锂金属电池的关注日益增多。锂金属表面不均匀的剥落或沉积会导致锂枝晶生长，锂枝晶容易刺穿隔膜，存在引发电池短路的风险，而且高反应活性的锂金属会与电解液不断反应被消耗，生成不稳定的固体电解质界面（SEI）膜，造成不可逆的容量损失，因此兼顾高能量密度与高安全性是锂金属电池发展应用中亟需解决的关键科学问题。具有强吸电子基团（C≡N）的聚丙烯腈（PAN）聚合物与碳酸酯溶剂中C=O的相互作用能形成更稳定的SEI膜，PAN作为锂负极涂层还能抑制锂枝晶的生长；另外，PAN具有较低的最低未占据分子轨道、较高的电化学稳定性和较宽的电化学窗口，能作为锂金属电池的聚合物电解质，并匹配高电压正极，兼具高能量密度和高安全性，故PAN聚合物在锂金属电池的电解质中有着很大的应用潜力。本文从电解质的不同状态（液态、凝胶、固态）介绍了PAN聚合物在液态电解质中作为隔膜、锂负极保护层以及在凝胶电解质、固态电解质的最新研究成果，并对PAN聚合物在锂金属电池电解质中的发展趋势进行展望。     

镧对Cu_6Sn_5长大驱动力及焊点可靠性的影响

在Sn60 Pb40钎料合金中加入微量稀土元素镧可以抑制表面组装焊点界面处Cu6 Sn5金属间化合物的生长 ,进而使焊点热疲劳寿命提高两倍。基于扩散动力学的热力学计算结果表明 ,添加微量稀土元素镧可降低Cu6 Sn5金属间化合物的长大驱动力 ,但存在一个镧的有效局部摩尔分数范围 ,0 18%是其极限值 ,0 0 8%是其最佳值。     

LiCl-KCl熔盐中Gd(Ⅲ)在Bi电极上的电化学行为及Bi_xGd_y金属间化合物的热力学数据

采用多种电化学技术研究了在723~823 K范围内Li Cl-KCl熔盐中Gd(Ⅲ)在液态Bi电极和Bi膜电极上的电化学行为.利用开路计时电位法估算了Bi-Gd金属间化合物(Bi2Gd,Bi Gd,Bi3Gd4,Bi3Gd5)的活度、相对偏摩尔吉布斯自由能、生成吉布斯自由能、生成焓和生成熵等热力学数据.通过恒电流和恒电位电解,在液态Bi电极上制备了Bi-Gd合金,并采用X射线衍射(XRD)和扫描电子显微镜-能量散射谱(SEM-EDS)表征了其结构.在恒电流电解中所得金属间化合物为Bi Gd,而在恒电位电解中所得金属间化合物为Bi3Gd5.     

镧对Cu6Sn5长大驱动力及焊点可靠性的影响

在Sn60-Pb40钎料合金中加入微量稀土元素镧可以抑制表面组装焊点界面处Cu6Sn5金属间化合物的生长,进而使焊点热疲劳寿命提高两倍。基于扩散动力学的热力学计算结果表明,添加微量稀土元素镧可降低Cu6Sn5金属间化合物的长大驱动力,但存在一个镧的有效局部摩尔分数范围,0．18％是其极限值,0．08％是其最佳值。     

Corrosion behaviour of soldered joints of magnesium alloys and dissimilar materials

In the last decade magnesium based materials have been used in many industrial applications. Problems arise from joining technologies and the corrosion behaviour of joined parts. The present study shows results of a new flux free soldering technology and the study of the corrosion properties of these soldered samples. Joints have been obtained by soldering of magnesium alloy AZ31 samples among each other or to aluminum alloy AlMgSi1 as well as to unalloyed, low-carbon steel. Different corrosion protection layers have been applied by thermal spraying. The corrosive potential of different soldered samples has been examined using current density-potential measurements. The corrosion behaviour of coated samples has been studied by salt spray testing in comparison to uncoated samples.     

A Simple Hydrothermal Route to Large‐Scale Synthesis of Uniform Silver Nanowires

This paper describes the preparation of uniform silver nanowires by reducing freshly prepared silver chloride with glucose at 180 °C for 18 hours in the absence of any surfactants or polymers. Scanning electron microscopy studies indicated that the silver nanowires are about 100 nm in diameter and up to 500 μm in length. High‐resolution transmission electron microscopy analyses showed that the silver nanowires grow perpendicularly to the Ag(200) plane. The silver nanowires are believed to grow through a solid–solution–solid process. Some influential factors on the growth of silver nanowires are also discussed.     

Classification of secondary ion mass spectrometry (SIMS) micrographs to characterize chemical phases

This work demonstrates the potential of multivariate image analysis methods in the extraction of useful, problem dependent information from SIMS images. Specific algorithms have been developed to classify SIMS micrographs manually as well as automatically. A feature selection has been achieved by means of principal component analysis with a subsequent image classification.As an application example for these improved digital image processing tools chemical phases within a soldered industrial metal sample have been identified. This is of highly practical value as it was assumed that during the soldering process inhomogeneities occur along the joint site which cause a cracking of the brazed material under mechanical strain conditions.     

Complementarity of pixe and pige for the characterization of gold items of ancient jewelry

By using strictly non destructive and non radioactive methods of elemental analysis (PIXE and PIGE), using a 3 MeV proton beam to induce prompt emission of characteristic X-rays or gamma-rays of the elements and simultaneous photon-spectroscopy with energy dispersive solid state detectors [Si(Li) and Ge(Li)] followed by a computer assisted data handling system, we have determined the relative amounts of copper, silver, cadmium and gold at the surface of more than 30 ancient gold objects. Results on only two items are discussed here. Traces or significant concentrations of cadmium have been detected at nearly all points on or in the neighbourhood of solders on many objects dating from Roman to early Byzantine times. Cadmium concentrations range between 2 to 75 parts per thousand. This range of variation and the relative concentrations of Au, Ag, Cu and Cd at the surface of the objects studied are very different from the figures obtained during analyses of modern soldering alloys. New approaches to solve the problem of Cadmium in ancient jewelry are indicated.     

Low-temperature synthesis of amorphous carbon nanocoils via acetylene coupling on copper nanocrystal surfaces at 468 K: a reaction mechanism analysis

A new type of amorphous helical carbon nanofibers has been synthesized using copper nanocatalysts and an acetylene gas source at atmospheric pressure. The nanofibers are grown at 468 K, which is the lowest temperature by ordinary metal-catalyzed thermal chemical vapor deposition of hydrocarbon, and exhibit a symmetric growth mode in the form of twin helices. IR, XRD, Raman, and C/H molar ratio analyses reveal a polymer-like structure with a weak trans-polyacetylene feature. The nanofibers are a mixture of solid polymers and a small amount of carbon. A reaction mechanism has been proposed on the basis of the previous studies of acetylene adsorption, desorption properties, and surface reactions on copper (111), (110), and (001) planes under ultrahigh-vacuum (UHV) conditions as well as the results obtained in our study. The reaction mechanism of acetylene on copper single-crystal surfaces under UHV conditions indeed reflects the reaction mechanism under practical catalytic conditions at atmospheric pressure. The nanofibers grow mainly via acetylene coupling to solid polymers on copper nanocrystal surfaces. Acetylene also couples to yield small amounts of liquid oligomers and gaseous products, and undergoes slight carbon deposition during the fiber growth.     

Rapid self-assembly of submicrospheres at liquid surface by controlling evaporation and its mechanism

A simple process is demonstrated to transfer the self-assembly of submicrospheres from solid substrate to liquid surface in fabricating synthetic opal. Irradiating light and controlled airflow are used to control the evaporation of solvent. This process induces solid layer with colors. SEM images of the solid layers show that those layers are synthetic opals for well ordered polystyrene spheres in a hexagonal close-packed structure over a large scale. An absorption peak is also observed at 541 nm in normal transmission spectrum of the fabricated sample. Furthermore, investigation of the phase transitions indicates that nuclei of synthetic opals grow up through accumulating at their bottom and extending at their edges during self-assembly.     

Dry Sintering Meets Wet Silver‐Ion “Soldering”: Charge‐Transfer Plasmon Engineering of Solution‐Assembled Gold Nanodimers From Visible to Near‐Infrared I and II Regions

Achieving highly tunable and localized surface plasmon resonance up to near infrared (NIR) regions is a key target in nanoplasmonics. In particular, a self‐assembly process capable of producing highly uniform and solution‐processable nanomaterials with tailor‐made plasmonic properties is lacking. We herein address this problem through a conjunctive use of wet Ag⁺ soldering and dry thermal sintering to produce nanodimer‐derived structures with precisely engineered charge‐transfer plasmon (CTP). The sintered dimers are water soluble, featuring gradually shifted CTP spanning an 800 nm wavelength range (up to NIR II). Upon silica removal, the products are grafted by DNA to offer surface functionality. This process is also adaptable to DNA‐linked AuNP dimers toward plasmonic meta‐materials via DNA‐guided soldering and sintering.     

Quantum dot nanobarcodes: epitaxial assembly of nanoparticle-polymer complexes in homogeneous solution

Multiplexed nanobarcodes have been prepared with quantum dots (QDs) and alternating amphiphilic copolymers consisting of hydrocarbons and maleic anhydride groups. In homogeneous solution, the QD-polymer complexes grow epitaxially into nanobeads of narrow size dispersity, which has been previously achieved only for micrometer-sized beads in the presence of solid supports. As a result of this new nanostructure formation mechanism, more than 250 QDs can be loaded into a nanobead of 100 nm in diameter. A model assay for sensitive detection of human prostate specific antigen has also been demonstrated using the QD-nanobeads as fluorescent reporters. This nanoparticle-polymer self-assembly technology is capable of producing a variety of nanostructures and is expected to open new opportunities in nanoparticle-based ultrasensitive detection and imaging.     

Supra-aggregates of fiber-forming anisotropic molecules

In this paper, the self-organization of fiber-forming anisotropic molecules is inspected both theoretically and experimentally. In the first part, a theoretical model which extends the de Gennes theory of thin films to assemblies of strongly anisotropic molecules is reported. The model predicts that solid supported thin films made up of fiber-forming discotic molecules can grow with both tangential and radial arrangement of the fibers, respectively leading to the formation of compact and holed supra-aggregates. These last systems form according to the following picture. The tangential growth minimizes the number of unfavorable free ends but introduces elastic strain especially in the central region of the aggregate. To reduce the elastic strain, some molecules are displaced from the central region toward the periphery of the growing aggregate, producing a localized well. In the second part of the paper, we experimentally face the above issue by depositing a strongly anisotropic disk-shaped molecule (rhodamine 123) onto different solid substrates through a spin coating procedure. By employing scanning force microscopy (SFM), the formation of thermodynamically favored fiberlike supramolecules as well as of compact and holed submicron-sized supra-aggregates has been demonstrated. The observed phenomena have been found to depend on the interplay of different parameters such as molecular concentration, evaporation time, and substrate composition. As main features, both theory and experiments show that holed supra-aggregates are more stable beyond a critical aggregation size and that the formation of holes is favored at high supersaturation. The theory seems valuable in extending previous dewetting models developed for fluid films with isotropic interaction forces.     

Analysis of cholesterol oxidation products by Fast gas chromatography/mass spectrometry

The aim of the present study was to set‐up a Fast gas chromatography/mass spectrometry method for the analysis of cholesterol oxidation products (COPs). A silylated mixture of seven oxysterol standards was injected into a Fast GC/MS system. A capillary GC column (10 m×0.1 mm internal diameter×0.1 μm film thickness) coated with 95% dimethyl‐ and 5% diphenyl‐polysiloxane, was used. The method gave a fast (total analysis time=3.5 min) and satisfactory resolution (R>1.2) of the COPs standards, with a good repeatability and sensitivity, similar to those of conventional GC/MS; recoveries were tested on mice liver. Fast GC/MS method suitability for COPs analysis in food was also tested on an oxidized sardine fillet, which had been previously saponified and purified by NH₂ solid‐phase extraction (SPE); a good repeatability and sensitivity was also obtained. The analytical performance of the Fast GC/MS method for the determination of COPs, together with the consequent significant reduction of the analysis time and consumables, demonstrates that Fast GC/MS represents a valid alternative to conventional GC/MS and evinces the great potential of such an analytical technique, which could be applied for both food and biological samples.