Plasmonic Metasurfaces Based on Nanopin‐Cavity Resonator for Quantitative Colorimetric Ricin Sensing

In view of the toxic potential of a bioweapon threat, rapid visual recognition and sensing of ricin has been of considerable interest while remaining a challenging task up to date. In this study, a gold nanopin‐based colorimetric sensor is developed realizing a multicolor variation for ricin qualitative recognition and analysis. It is revealed that such plasmonic metasurfaces based on nanopin‐cavity resonator exhibit reflective color appearance, due to the excitation of standing‐wave resonances of narrow bandwidth in visible region. This clear color variation is a consequence of the reflective color mixing defined by different resonant wavelengths. In addition, the colored metasurfaces appear sharp color difference in a narrow refractive index range, which makes them especially well‐suited for sensing applications. Therefore, this antibody‐functionalized nanopin‐cavity biosensor features high sensitivity and fast response, allowing for visual quantitative ricin detection within the range of 10–120 ng mL^?1 (0.15 × 10^?9–1.8 × 10^?9 m ), a limit of detection of 10 ng mL^?1, and the typical measurement time of less than 10 min. The on‐chip integration of such nanopin metasurfaces to portable colorimetric microfluidic device may be envisaged for the quantitative studies of a variety of biochemical molecules.     

Controllable synthesis and photoluminescence properties of ZnO nanorod and nanopin arrays

Well-aligned ZnO nanorods and nanopins are synthesized on a silicon substrate using a one-step simple thermal evaporation of a mixture of zinc and zinc acetate powder under controlled conditions. A self-assembled ZnO buffer layer was first obtained on the Si substrate. The structure and morphology of the as-synthesized ZnO nanorod and nanopin arrays are characterized using X-ray diffraction, and scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. The influence of the background atmosphere on the two ZnO nanostructures has been studied. Two different growth mechanisms are mentioned to interpret the formation of ZnO nanorod and nanopin arrays in our work. The room-temperature PL features the ZnO nanorods exhibit only sharp and strong ultraviolet (UV) emission emissions, which confirms the better crystalline and optical quality than the ZnO nanopins.     

Perspective on Structural Evolution and Relations with Thermophysical Properties of Metallic Liquids

The relationship between the structural evolution and properties of metallic liquids is a long‐standing hot issue in condensed‐matter physics and materials science. Here, recent progress is reviewed in several fundamental aspects of metallic liquids, including the methods to study their atomic structures, liquid–liquid transition, physical properties, fragility, and their correlations with local structures, together with potential applications of liquid metals at room temperature. Involved with more experimentally and theoretically advanced techniques, these studies provide more in‐depth understanding of the structure–property relationship of metallic liquids and promote the design of new metallic materials with superior properties.     

金属载体催化剂涂层制备技术的研究进展

为解决金属载体催化剂活性涂层涂覆困难且使用过程中易剥落的问题,通过对金属载体进行表面处理得到过渡层／膜,其可以提高后续涂层的结合力。介绍了不同金属载体催化剂涂层的制备技术,讨论了各种方法的优缺点,进而提出了金属栽体涂层技术的发展方向。     

Backscatter cross sections for randomly oriented metallic flakes at optical frequencies: full wave approach

The backscatter cross sections for randomly oriented metallic flakes are derived using the full wave approach. The metallic flakes are characterized by their surface height spectral density function. Both specular point and Bragg scattering at optical frequencies are accounted for in a self-consistent manner. It is shown that the average normalized backscatter cross sections (per unit volume) for the randomly oriented metallic flakes are larger than that of metallic spheres.     

表面纳米化对金属材料耐磨性的影响

材料的磨损起源于表面,金属材料的摩擦磨损性能与表面结构密切相关。利用表面纳米化(Surface nanocrystallization)技术可以在金属材料的表面制备出一定厚度的纳米结构表层,从而大大提高金属的耐磨性。结合国内外学者的研究报道,综述了表面纳米化在金属耐磨性方面的影响,讨论了表面纳米化方法与机理以及表面纳米化影响耐磨性的因素,简述了应用表面纳米化技术改善各种金属材料耐磨性的研究和实用成果,最后进行了总结和展望。     

Metallic nanocrystals near ultrasmooth metallic films for surface-enhanced Raman scattering application

We studied the effect of the substrate on the surface-enhanced Raman scattering (SERS) signals of metallic nanocrystal films by making a direct comparison between cases with metallic and semiconducting substrate surfaces. Ag nanoparticles smaller than 10?nm were synthesized and uniform arrays were formed on both ultrasmooth metallic and Si surfaces. These substrates provide reproducible SERS signals with high enhancement factors over large areas. Moreover, a SERS signal about one order of magnitude higher was obtained in the metallic surface case as compared with the Si substrate case, which is attributed to stronger plasmon coupling between the nanoparticles and their charge-conjugate images in the underlying metallic surface. The interpretation of our experimental results was confirmed by our finite difference time domain calculations. The dependence of the interaction between the nanoparticles and the substrate surface on the direction of the incident electromagnetic field is also discussed.     

闭孔泡沫金属三维细观模型建模方法

该文在深入分析闭孔泡沫金属CT扫描图像的基础上,根据其细观结构特点,提出了泡沫金属三维细观模型建模方法。首先,根据闭孔泡沫金属胞孔形状和尺寸分布特性,提出了采用随机椭球体模拟胞孔的建模方法,通过采用随机投放算法,建立了三维胞孔随机投放模型;其次,提出了有限元网格剖分算法,通过引入材料属性识别算法,建立了泡沫金属三维有限元细观模型。在此基础上,研究了冲击荷载下泡沫金属的力学性能,分析了细观损伤破坏机理和能量吸收特性。结果表明,该文建立的三维细观模型,能够较好地反映泡沫金属材料的力学性能和细观损伤破坏机理。     

Atomistic basis for the plastic yield criterion of metallic glass

Because of their disordered atomic structure, amorphous metals (termed metallic glasses) have fundamentally different deformation mechanisms compared with polycrystalline metals. These different mechanisms give metallic glasses high strength, but the extent to which they affect other macroscopic deformation properties is uncertain. For example, the nature of the plastic-yield criterion is a point of contention, with some studies reporting yield behaviour roughly in line with that of polycrystalline metals, and others indicating strong fundamental differences. In particular, it is unclear whether pressure- or normal stress-dependence needs to be included in the plastic-yield criterion of metallic glasses, and how such a dependence could arise from their disordered structure. In this work we provide an atomic-level explanation for pressure-dependent yield in amorphous metals, based on an elementary unit of deformation. This simple model compares favourably with new atomistic simulations of metallic glasses, as well as existing experimental data.     

Elektronenstrahlschweißen von massiven metallischen Gläsern

Electron‐Beam‐Welding of bulk metallic glasses Because of their excellent mechano‐technological properties bulk metallic glasses form a promising, relatively new class of materials. Due to their low thermal stability the weldability of bulk metallic glasses is subject to narrow limits, in case the joining zone shall be prevented from crystallization. The paper at hand describes the status‐quo of the research work on electron beam welding of beryllium‐free, zirconium‐based bulk metallic glasses (Zr_52,5Ti₅Cu_17,9Ni_14,6Al₁₀) carried out at the Welding and Joining Institute at RWTH Aachen University. So far, high quality joints free from defects could be produced, however, it has not beenaccomplished to avoid the crystallization of the joining zone completely. Further research is in progress.     

Making metallic glasses plastic by control of residual stress

Metallic glasses, now that many compositions can be made in bulk, are of interest for structural applications exploiting their yield stress and yield strain, which are exceptionally high for metallic materials. Their applicability is limited by their near-zero tensile ductility resulting from work-softening and shear localization. Even though metallic glasses can show extensive local plasticity, macroscopically they can effectively be brittle, and much current research is directed at improving their general plasticity. In conventional engineering materials as diverse as silicate glasses and metallic alloys, we can improve mechanical properties by the controlled introduction of compressive surface stresses. Here we demonstrate that we can controllably induce such residual stresses in a bulk metallic glass, and that they improve the mechanical performance, in particular the plasticity, but that the mechanisms underlying the improvements are distinct from those operating in conventional materials.     

Selective Breakdown of Metallic Pathways in Double‐Walled Carbon Nanotube Networks

Covalently functionalized, semiconducting double‐walled carbon nanotubes exhibit remarkable properties and can outperform their single‐walled carbon nanotube counterparts. In order to harness their potential for electronic applications, metallic double‐walled carbon nanotubes must be separated from the semiconductors. However, the inner wall is inaccessible to current separation techniques which rely on the surface properties. Here, the first approach to address this challenge through electrical breakdown of metallic double‐walled carbon nanotubes, both inner and outer walls, within networks of mixed electronic types is described. The intact semiconductors demonstrate a ～62% retention of the ON‐state conductance in thin film transistors in response to covalent functionalization. The selective elimination of the metallic pathways improves the ON/OFF ratio, by more than 360 times, to as high as 40 700, while simultaneously retaining high ON‐state conductance.     

Direct identification of metallic and semiconducting single-walled carbon nanotubes in scanning electron microscopy

Because of their excellent electrical and optical properties, carbon nanotubes have been regarded as extremely promising candidates for high-performance electronic and optoelectronic applications. However, effective and efficient distinction and separation of metallic and semiconducting single-walled carbon nanotubes are always challenges for their practical applications. Here we show that metallic and semiconducting single-walled carbon nanotubes on SiO(2) can have obviously different contrast in scanning electron microscopy due to their conductivity difference and thus can be effectively and efficiently identified. The correlation between conductivity and contrast difference has been confirmed by using voltage-contrast scanning electron microcopy, peak force tunneling atom force microscopy, and field effect transistor testing. This phenomenon can be understood via a proposed mechanism involving the e-beam-induced surface potential of insulators and the conductivity difference between metallic and semiconducting SWCNTs. This method demonstrates great promise to achieve rapid and large-scale distinguishing between metallic and semiconducting single-walled carbon nanotubes, adding a new function to conventional SEM.     

Comparison of compressive deformation and fracture behaviors of Zr- and Ti-based metallic glasses with notches

Compressive tests on the Zr- and Ti-based metallic glasses with different notches were investigated to compare their shear fracture mechanism and plastic deformation abilities. It is found that the plasticity of the two metallic glasses can be improved by installing two semicircular symmetrical notches even for the Ti-based metallic glass which has nearly zero compressive plasticity. The enhanced plasticity may be ascribed to the easy initiation of shear bands (SBs) around the notches, and the consequent blocking effect of notches on the propagation of shear bands according to the large-scale stress gradient. Additionally, based on a theoretical model originated from the concept of critical steady shear displacement (CSSD), compared with the sizes of smooth regions on the fracture surface, the plasticity difference of the two different metallic glasses was analyzed quantitatively. The current findings might provide an approach to understand and estimate the difference in the plastic deformation abilities on diverse metallic glasses, as well as the ones with large-scale stress gradient.     

Fabrication of a carbon-nanotube-based field-effect transistor by microcontact printing

The fabrication of a field-effect transistor with both channel material and source and drain electrodes made from carbon nanotubes (CNTs) through patterned deposition of CNT films by microcontact printing is described. Surfactant-dispersed single-walled CNTs are first separated into semiconducting and metallic fractions by gel filtration. The semiconducting and metallic CNTs are then sequentially transferred by dendrimer-coated polydimethylsiloxane stamps onto dendrimer-coated silicon wafers following a printing protocol optimized for this purpose. The resulting CNT micropatterns are visualized by atomic force microscopy. Semiconducting as well as metallic CNTs preserve their characteristic electronic properties within the transferred films. A device composed of a rather thick (ca. 5 nm) and densely patterned film of metallic CNTs cross-printed on top of a thinner (ca. 1.5 nm) and less dense film of semiconducting CNTs shows the typical properties of a field-effect transistor with the metallic CNT stripes as electrodes, the semiconductive CNT stripes as channel material, and the silicon substrate as gate electrode.     

Analysis of the drude model in metallic films

A method, believed to be new, to simulate Drude parameters for collective oscillation of the free carriers in metallic films is proposed. Plasma resonance frequency and relaxation were simulated simultaneously from both the real and the imaginary parts of the dielectric function of a metallic film after consideration of their correlation in the Drude model. As examples, the contributions of the electrons in Ag films and of the free carriers in metallic silicide, NbSi(2) and TaSi(2), films have been studied.     

Self-healing coatings in anti-corrosion applications

Nonmetallic (based on polymers or oxides) and metallic protective coatings are used to protect metal products against the harmful action of the corrosion environment. In recent years, self-healing coatings have been the subject of increasing interest. The ability of such coatings to self-repair local damage caused by external factors is a major factor contributing to their attractiveness. Polymer layers, silica-organic layers, conversion layers, metallic layers and ceramic layers, to mention but a few, are used as self-healing coatings. This paper presents the main kinds of self-healing coatings and explains their self-healing mechanisms.     

Heat and mass transfer between local combustion sites in metallic powder preforms under thermal-explosion conditions

Measurement of temperatures is made at different points in the volumes of exothermic cells and intervening spacings in model powder metallic preform mixtures during their combustion under thermal-explosion conditions. The presence of temperature gradients is found, as are regularities in their change in interrelation with specific features of migration of eutectics and melts formed in a porous metallic skeleton consolidated in a combustion wave. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 387–393, May–June, 1998.     

Effect of Zr on microstructure of metallic glass coatings prepared by gas tunnel type plasma spraying

Metallic glass is one of the most attractive advanced materials, and many researchers have conducted various developmental research works. Metallic glass is expected to be used as a functional material because of its excellent physical and chemical functions such as high strength and high corrosion resistance. However, the application for small size parts has been carried out only in some industrial fields. In order to widen the industrial application fields, a composite material is preferred for the cost performance. In the coating processes of metallic glass with the conventional deposition techniques, there is a difficulty to form thick coatings due to their low deposition rate. Thermal spraying method is one of the potential candidates to produce metallic glass composites. Metallic glass coatings can be applied to the longer parts and therefore the application field can be widened. The gas tunnel plasma spraying is one of the most important technologies for high quality ceramic coating and synthesizing functional materials. As the gas tunnel type plasma jet is superior to the properties of other conventional type plasma jets, this plasma has great possibilities for various applications in thermal processing. In this study, the gas tunnel type plasma spraying was used to form the metallic glass coatings on the stainless-steel substrate. The microstructure and surface morphology of the metallic glass coatings were examined using Fe-based metallic glass powder and Zr-based metallic glass powder as coating material. For the mechanical properties the Vickers hardness was measured on the cross section of both the coatings and the difference between the powders was compared.