Production,properties and applications of microwire and related products

Methods available for the production of microwire, defined as fine filament of circular cross-section and diameter less than 1001 cm, are reviewed, with particular attention being devoted to the versatile Taylor-wire route. The process parameters which are considered to be important in determining the quality of material produced by this and other related techniques, and the types and properties of microwire, are outlined and compared. Techniques for producing related materials, including fibre of non-circular cross-section and narrow ribbon, are also reviewed briefly. In conclusion, a number of potential applications for microwire materials are discussed.     

Aligned two- and three-dimensional structures by directional freezing of polymers and nanoparticles

The preparation of materials with aligned porosity in the micrometre range is of technological importance for a wide range of applications in organic electronics, microfluidics, molecular filtration and biomaterials. Here, we demonstrate a generic method for the preparation of aligned materials using polymers, nanoparticles or mixtures of these components as building blocks. Directional freezing is used to align the structural elements, either in the form of three-dimensional porous structures or as two-dimensional oriented surface patterns. This simple technique can be used to generate a diverse array of complex structures such as polymer-inorganic nanocomposites, aligned gold microwires and microwire networks, porous composite microfibres and biaxially aligned composite networks. The process does not involve any chemical reaction, thus avoiding potential complications associated with by-products or purification procedures.     

Fabrication of submicrometer-sized gold electrodes of controlled geometry for scanning electrochemical-atomic force microscopy

A method for fabricating submicrometer-sized gold electrodes of conical or spherical geometry is described. By generating an electric arc between an etched gold microwire and a tungsten counter electrode, the very end of the gold microwire can be melted and given an overall spherical or conical shape a few hundred nanometers in size. The whole wire is subsequently insulated via the cathodic deposition of electrophoretic paint. By applying a high-voltage pulse to the microwire, the film covering its very end can then be selectively removed, thus exposing a submicrometer-sized electrode surface of predefined geometry. The selective exposure of the preformed end of the microwire is demonstrated by cyclic voltammetry, scanning electron microscopy, and metal electrodeposition experiments. The electrophoretic paint coating provides a low-capacitance, robust insulating film allowing exploration of a very wide potential window in aqueous solution. The submicrometer-sized electrodes can easily be turned into probes suitable for combined scanning electrochemical-atomic force microscopy by bending and flattening the gold microwire so that the tip is borne by a flexible enough arm. The good agreement between theoretical and experimental scanning electrochemical microscopy approach curves thus obtained confirms that only the very end of the tip, of predefined geometry, is exposed to the solution.     

Embedded ferromagnetic microwires for monitoring tensile stress in polymeric materials

Considerable efforts have been made to develop testing non-destructive methods for polymer composite materials. We would like to introduce researchers in the field of smart materials to a new method of monitoring internal stresses. The method can be classified as an embedded sensing technique, where the sensing element is a glass-coated ferromagnetic microwire with a specific magnetic anisotropy. With a diameter 10–100 μm, the microwire impedance acts as the controlled parameter which is monitored for a weak alternating current (AC) in the MHz range. The microwire impedance becomes stress sensitive in the presence of a weak constant axial bias magnetic field. This external parameter allows the impedance stress sensitivity to be easily tuned. In addition, a local bias field may also allow the reconstruction of stress profile when it is scanned along the microwire. The experimental results are analysed using simple magnetostatic and impedance models.     

Moisture-Enabled Electricity Generation: From Physics and Materials to Self-Powered Applications

The exploration of the utilization of sustainable, green energy represents one way in which it is possible to ameliorate the growing threat of the global environmental issues and the crisis in energy. Moisture, which is ubiquitous on Earth, contains a vast reservoir of low-grade energy in the form of gaseous water molecules and water droplets. It has now been found that a number of functionalized materials can generate electricity directly from their interaction with moisture. This suggests that electrical energy can be harvested from atmospheric moisture and enables the creation of a new range of self-powered devices. Herein, the basic mechanisms of moisture-induced electricity generation are discussed, the recent advances in materials (including carbon nanoparticles, graphene materials, metal oxide nanomaterials, biofibers, and polymers) for harvesting electrical energy from moisture are summarized, and some strategies for improving energy conversion efficiency and output power in these devices are provided. The potential applications of moisture electrical generators in self-powered electronics, healthcare, security, information storage, artificial intelligence, and Internet-of-things are also discussed. Some remaining challenges are also considered, together with a number of suggestions for potential new developments of this emerging technology.     

Preparation,properties and chemistry of glass- and glass-ceramic-to-metal seals and coatings

An overview is given outlining the materials and technologies that have been employed in the preparation of glass- and glass-ceramic-to-metal seals and coatings. Metal/non-metal bonding theories are summarized, and the conditions required for the formation of strong chemical bonding are described and discussed. Particular reference is given to the interfacial chemistry involved for individual glass/metal and glass-ceramic/metal combinations. The major factors responsible for the preparation of high-quality seals and coatings, free from porosity and other undesirable defects, are also outlined and discussed. In addition, a number of applications for seals and coatings are briefly described.     

金属氧化物纳米线和纳米棒的制备及应用

本文综述了金属氧化物纳米线、纳米棒研究的新进展。重点评述了气相热化学合成法、热分解前驱物法、溶胶-凝胶电泳沉积法制备纳米线的过程及各自的生长机制，并对金属氧化物纳米线／棒的潜在应用作了介绍。     

Fabrication and characterization of nano/amorphous dual-phase FINEMET microwires

A nano/amorphous dual-phase FINEMET microwire was fabricated directly from molten alloy without any interstage annealing by a home-built melt extraction technique (MET). The microstructure, mechanical and pronounced electromagnetic interference shielding (EMI) effectiveness of this dual-phase microwire has been systematically evaluated. The structural analysis reveals that the as-cast FINEMET microwire consists of two distinct structures, i.e., amorphous and nanocrystalline phase due to their different cooling characteristics. Compared with other reported FINEMET alloys, the extracted microwire exhibits a superior high tensile strength of 1800 MPa. These nanocrystals enabled dual-phase microwires also exhibit large EMI SE values in the frequency range of 8–12 GHz (X-band) due to the multiple magnetic loss mechanisms associated with their intrinsic structural characteristics. The combination of excellent mechanical properties and electromagnetic properties make this kind of melt-extracted dual-phase FINEMET microwire promising for a range of structure and multifunctional applications.     

二氧化钛光生阴极保护材料研究进展

二氧化钛光生阴极保护材料以自身独特的光电特性直接将太阳光转化为电子,降低金属的电势,为金属提供保护,而自身没有消耗,是一种理想的新型阴极保护材料。本文回顾了近年来国内外二氧化钛光生阴极保护材料的发展,重点介绍了纳米二氧化钛的制备和改性方法以及在提高光生阴极保护性能方面的研究工作,探讨了纳米二氧化钛材料的光生阴极保护机理,并对光生阴极保护材料的发展前景进行了展望。     

Microgrid Electrode for Si Microwire Solar Cells with a Fill Factor of Over 80%

Here, a novel microgrid top electrode for highly efficient radial‐junction Si microwire solar cells is demonstrated. The microgrid electrode minimizes optical and electrical losses, thus ensuring proper function of the shallow (sheet resistance of ≈100 Ω sq⁻¹) junction emitter. This leads to effective collection of the photocarriers from the shallow junction emitter through the top electrode without severe Auger/surface recombination, improving the overall power conversion efficiency of the Si microwire solar cell. With an optimized microgrid structure, 1 cm² microwire solar cells show a conversion efficiency of up to 16.5%, with an open‐circuit voltage of 565.2 mV and a short‐circuit current density of 35.9 mA·cm⁻²; this conversion efficiency is 72% higher than that of solar cells with an edge electrode (9.6%). Further, an ≈1 μm thick Ni electrode that is formed by electroplating considerably reduces the metal and contact resistances, which reproducibly yields a fill factor of over 80% (max 81.2%). Thus, the use of a novel microgrid to construct an ideal metal/emitter interface presents a unique opportunity to develop highly efficient microwire solar cells.     

多孔金属材料的制备及应用

根据制备过程中金属的状态，从液相法、固相法、金属沉积法三方面介绍了多孔金属材料的制备工艺。液态金属的发泡可以通过直接吹气法发泡法、金属氢化物分解发泡法来实现；固态金属可以通过粉末冶金法、粉末发泡法、金属空心球法和金属粉末纤维烧结法来实现；与前两种不同的是，金属沉积法是采用化学或物理的方法来实现的。最后，讨论了多孔金属材料在结构材料和功能材料两方面的应用。     

花状纳米金属及金属化合物的合成及其电磁性能研究

三维花状结构的纳米金属及金属化合物材料作为纳米材料的一个重要组成部分,由于其特殊的形貌和复杂的结构而具备许多块状或者低维纳米材料不具备的性质,在光、电、磁、催化和传感方面显示出巨大的应用前景.综述了近年来有关花状结构纳米金属及金属化合物的合成、性能及其应用,分别介绍了花状纳米金属及金属化合物的主要合成方法,阐述了各种花状纳米金属及金属化合物的电磁性质及其在相关领域的应用.     

金属纳米块体材料制备加工技术和应用

综述了国内外块状纳米材料的制备技术进展及存在的问题 ,提出了超短时脉冲电流直接晶化法和深过冷直接晶化法两类潜在的块状金属纳米晶制备技术 ,并对今后的研究及发展前景进行了展望。同时对大块纳米材料的性能特点及应用前景做了展望     

Simple and sensitive electrode design for microchip electrophoresis/electrochemistry

A simple and sensitive electrode design for microchip capillary electrophoresis/electrochemistry (CE-EC) is presented. The system employs metal microwires as the working electrodes for electrochemical detection. Two general approaches for integration of electrodes in microchip CE-EC are commonly used, end-channel and microfabrication. The end-channel approach allows electrode cleaning and the use of chemically modified electrodes; however, the designs generally lack portability and the ability to incorporate multiple electrodes. Microfabrication allows the incorporation of multiple electrodes on-chip and is easily made portable; however, it requires the use of expensive metallization and clean room facilities, and integration of more than one electrode material is challenging. The reported approach aligns a solid metal microwire through the separation channel allowing integration of multiple electrodes and the use of different electrode materials without sacrificing the portability. A detection limit of 100 nM for dopamine was achieved without the use of a decoupler as a result of a higher collection efficiency with the new design.     

Micro‐Macroporous Composite Materials – Preparation Techniques and Selected Applications: A Review

Pores, on several orders of magnitude in size, control the properties of a solid material to a large extent. This is just as true for materials containing pores in the sub‐nanometer range like zeolites as for cellular foam structures with pores of several millimeters in size. All these porous materials have their distinct potential application ranging from heterogeneous catalysis to metal melt filtration. In many cases, the (hierarchical) combination of pores with different size regimes can improve the performance of the respective porous material or can lead to entirely new properties and applications. This review addresses the preparation and properties of microporous‐macroporous composite materials based on cellular foam supports (ceramic, metal, polymer) with a coating of a microporous compound (zeolite, zeotype framework, metal‐organic framework). The manufacturing of these materials can either be performed by dispersion‐based techniques, where the microporous coating is applied from a dispersion onto the cellular support (ex situ), or in situ by crystallization of the microporous compound directly onto the struts of the foam structure. In both cases, the general procedure can be modified by a pretreatment of the cellular support in order to improve the coating layer adherence, the overall amount of deposited material, or to control of the crystal morphology of the microporous compound.

     

聚丙烯腈电纺纤维材料的研究进展

本文综述了静电纺丝法制备聚丙烯腈纤维材料的研究进展,包括聚丙烯腈纳米纤维的制备条件、金属氧化物涂覆聚丙烯腈纳米纤维、聚丙烯腈纳米纤维的碳化、聚丙烯腈/Ag纳米粒子以及聚丙烯腈/碳纳米管复合静电纺丝,对系列丙烯腈共聚物的静电纺丝研究也进行了总结.     

木质素基金属纳米粒子复合材料的制备及其应用研究进展

木质素是一种最丰富的芳香族天然高分子生物质资源,木质素纳米粒子既具有木质素原本特点,还具有纳米材料的纳米效应等特性,在众多功能材料领域具有很大的潜在应用价值,特别是作为绿色还原剂直接还原金属离子生成木质素基金属纳米粒子复合材料,被广泛应用于催化领域等。本文综述了木质素纳米粒子的制备及其在金属离子还原和金属纳米粒子负载的研究进展,重点综述了木质素基金属纳米粒子复合材料在不同应用领域的研究进展,最后总结并展望了木质素在金属纳米粒子复合材料制备和应用中面临的机遇和挑战。      

玻璃包覆Fe79-xCox Si8 B13非晶合金微丝的磁性能

实验以熔融纺丝法制备的玻璃包覆Fe79-xCoxSi8B13非晶合金微丝为对象,分析了微丝成分、尺寸以及玻璃包覆层去除对微丝静磁性能的影响。研究结果表明,玻璃包覆Fe79-xCoxSi8B13非晶合金微丝存在明显的磁各向异性,微丝轴向为易磁化方向;随着Co含量的增加,微丝的饱和磁化强度先增大后减小,Co含量为10%的Fe69Co10Si8B13非晶合金微丝饱和磁化强度最高,为1323emu·cm-3;对于玻璃包覆Fe69Co10Si8B13非晶合金微丝,当芯丝半径与玻璃包覆层厚度比值k约小于0.5时,其轴向磁滞回线为近矩形,表现出大巴克豪森效应;微丝的轴向剩磁比随k值的增大而减小,而微丝径向剩磁比保持很小,仅0.03左右;微丝的轴向和径向矫顽力均随比值k的增大而减小;当芯丝半径为10.9μm、玻璃包覆层厚度为9.7μm(k为1.12)时,去除包覆层后微丝的轴向矫顽力降低30%、径向矫顽力降低11%;而轴向剩磁比降低33%、径向剩磁比降低67%。     

Polar charges induced electric hysteresis of ZnO nano/microwire for fast data storage

We demonstrate an innovative memory device made of a single crystalline ZnO nanowire/microwire that works with a different mechanism from the p-n junction based memristor. A nonsymmetric, Schottky-Ohmic contacted ZnO nano/microwire can serve as a memristor if the channel length is short and the applied frequency is high. The observed phenomena could be explained based on a screening model of the polar charges at the two ends of the wire owing to the crystal structure of ZnO. The polar charges are usually fully screened by free electrons coming from the metal sides. But when the magnitude of the externally applied field exceeds a threshold value, the free electrons that screen the polar surfaces can be pulled away from the interface region, leading to a transient change in the effective height of the local Schottky barrier height owing to the electrical field formed by the polar surfaces of ZnO nanowires, which acts as a resistor with its magnitude depending on the total charges being transported. Such a phenomenon could be used for high density and fast writing/erasing data storage.     

Deeply Reconstructed Hierarchical Ni–Co Microwire for Flexible Ni–Zn Microbattery with Excellent Comprehensive Performance

The rise of flexible electronics calls for efficient microbatteries (MBs) with requirements in energy/power density, stability, and flexibility simultaneously. However, the ever-reported flexible MBs only display progress around certain aspects of energy loading, reaction rate, and electrochemical stability, and it remains challenging to develop a micro-power source with excellent comprehensive performance. Herein, a reconstructed hierarchical Ni–Co alloy microwire is designed to construct flexible Ni–Zn MB. Notably, the interwoven microwires network is directly formed during the synthesis process, and can be utilized as a potential microelectrode which well avoids the toxic additives and the tedious traditional powder process, thus greatly simplifying the manufacture of MB. Meanwhile, the hierarchical alloy microwire is composed of spiny nanostructures and highly active alloy sites, which contributes to deep reconstruction (≈100 nm). Benefiting from the dense self-assembled structure, the fabricated Ni–Zn MB obtained high volumetric/areal energy density (419.7 mWh cm⁻³, 1.3 mWh cm⁻²), and ultrahigh rate performance extending the power density to 109.4 W cm⁻³ (328.3 mW cm⁻²). More surprisingly, the MB assembled by this inherently flexible microwire network is extremely resistant to bending/twisting. Therefore, this novel concept of excellent comprehensive micro-power source will greatly hold great implications for next-generation flexible electronics.