X‐ray diffraction (XRD)‐studies on the temperature dependent interface reactions on hafnium,zirconium, and nickel coated monocrystalline diamonds used in grinding segments for stone and concrete machining

Diamond impregnated metal matrix composites are the state of the art solution for the machining of mineral materials. The type of interface reactions between the metal matrix and diamond surface has an essential influence on the tool performance and durability. To improve the diamond retention, the diamonds can be coated by physical vapour deposition with metallic materials, which enforce interface reactions. Hence, this paper focuses on the investigation of the interfacial area on metal‐coated monocrystalline diamonds. Hafnium and zirconium, both known as carbide forming elements, are used as coating materials. The third coating, which is used to determine its catalytic influences when applied as a physical vapour deposition (PVD)‐layer, is nickel. Additionally, the coated diamond samples were heat‐treated to investigate the starting point of the formation of new phases. X‐ray diffraction‐analyses revealed the assumed carbide formation on hafnium and zirconium coated samples. The formation temperature was identified between 800 °C and 1000 °C for hafnium and zirconium coatings.     

Sputter coating of lithium metal electrodes with lithiophilic metals for homogeneous and reversible lithium electrodeposition and electrodissolution

Inhomogeneous lithium (Li) deposition leads to the formation of dendrites and “dead” Li, which is a limiting factor for the commercial success of Li metal batteries (LMBs). Herein, the sputter coating of Li metal electrodes by the sputter deposition method with lithiophilic metals, such as gold (Au) or zinc (Zn), was used in order to improve the electrochemical performance of Li metal electrodes. The structural characterization of such electrodes after the sputter deposition process indicated the presence of the corresponding Li-intermetallic phase (Li₁₅Au₄, LiZn) at the surface of the Li metal electrodes. Morphological investigations showed that the Li-intermetallic phases were able to steer the electrodeposition of Li beneath the Li-intermetallic coating, resulting in homogeneous dispersion of the Li deposits. The electrochemical measurements in symmetrical Li||Li cells also indicated reduced overvoltages. Up to a cycled capacity of 0.2825 mAh/cm², these electrodes showed stable overvoltage for the lithium electrodissolution and electrodeposition process in comparison to pristine Li metal electrodes. Furthermore, in S8||Li cells, the overpotentials of sputter coated Li metal electrodes (Au@Li, Zn@Li) during operation are highly reduced compared to pristine Li metal electrodes. Thus, the results presented here, indicate that sputter coating of Li metal electrodes represents a promising approach to improve the performance of high energy LMBs through engineering of the Li metal interphase.     

Coating deposition and adhesion enhancements by laser surface texturing—metallic particles on different classes of substrates in cold spraying process

A nonsystematic study of metallic particle deposition behavior in kinetic spray process for three classes of substrate materials was performed (metallic, polymer, and ceramic). The particle–substrate contact time, temperature, and area upon impact were estimated for different topographies by numerical analysis. The results indicated that the deformation and the resultant bonding were dependent on the contact shape area. Laser surface texturing was used as a surface prior treatment to create specific topographies. The deposition efficiency and the adhesion strength were evaluated and compared with the numerical results. First, metal–metal couples investigated large adiabatic shear instability at the interface causing intimate adhesive bonds. It was maximized for cavities because the interface temperature and contact area were larger at the interface. Besides, the mechanical anchoring was more efficient with laser gripping zones. Then, metal deposition on polymer was a challenge. Particle embedded in the substrate only if the particle kinetic energy was sufficient to penetrate as far as its diameter. Cold spray process needed to be studied. However, concave shape indicated a larger deposition efficiency by minimizing bounces. Also, metallization of ceramic by cold spray demonstrated a problem due to a nondeformation of the substrate. So, particle compressive states were the key for mechanical anchoring, and it was provided by laser surface texturing. Finally, cold spray parameters and surface topography were dependant. A methodology was established with particle states and particle/substrate properties to adapt the surface topography to enhance deposition efficiency and adhesion. The window of deposition was larger for laser-treated surface. Laser surface texturing enabled an adapted surface structuration for many applications.     

Shape‐Controlled Synthesis of Colloidal Metal Nanocrystals by Replicating the Surface Atomic Structure on the Seed

Controlling the surface structure of metal nanocrystals while maximizing the utilization efficiency of the atoms is a subject of great importance. An emerging strategy that has captured the attention of many research groups involves the conformal deposition of one metal as an ultrathin shell (typically 1–6 atomic layers) onto the surface of a seed made of another metal and covered by a set of well‐defined facets. This approach forces the deposited metal to faithfully replicate the surface atomic structure of the seed while at the same time serving to minimize the usage of the deposited metal. Here, the recent progress in this area is discussed and analyzed by focusing on the synthetic and mechanistic requisites necessary for achieving surface atomic replication of precious metals. Other related methods are discussed, including the one‐pot synthesis, electrochemical deposition, and skin‐layer formation through thermal annealing. To close, some of the synergies that arise when the thickness of the deposited shell is decreased controllably down to a few atomic layers are highlighted, along with how the control of thickness can be used to uncover the optimal physicochemical properties necessary for boosting the performance toward a range of catalytic reactions.     

Surface characterization of silver and palladium modified glassy carbon

In this work, the influence of silver and palladium on the surface of undoped, boron doped and phosphorus doped glassy carbon has been studied. The silver and palladium concentrations in solution, after metal deposition, were measured by atomic absorption spectrophotometer. The morphology of metal coatings was characterized by scanning electron microscopy. In order to investigate the nature and thermal stability of surface oxygen groups, temperature-programmed desorption method combined with mass spectrometric analyses, was performed. The results obtained have shown that silver and palladium spontaneously deposit from their salt solutions at the surface of glassy carbon samples. Silver deposits have dendrite structure, whilst palladium forms separate clusters. The highest amount of both silver and palladium deposits at the surface of sample containing the highest quantity of surface oxide complexes. It has been concluded that carboxyl groups and structure defects are responsible for metal reduction. Calculated desorption energies have shown that the surface modification by metal deposition leads to the formation of more stable surface of undoped and doped glassy carbon samples.     

基于表面金属功能化防红外辐射纯棉织物的制备与表征

以不同紧度的纯棉织物为基材,采用射频磁控溅射技术进行金属化处理,制备出表面覆有不同材料(Cu、Al、Ag)的金属化织物。建立正交实验,系统研究了织物紧度、沉积时间、镀层金属种类对织物防红外辐射性能的影响。借助原子力显微镜(AFM)对溅射前后织物表面的形貌和结构进行了分析;利用傅里叶红外变换光谱仪、紫外光分光光度仪和红外照相机对织物防红外效果进行测试。结果表明:金属种类是影响红外反射率的主要因素(透过率强度对比:CuAlAg),其中紧度83%、沉积时间60min的镀铜织物防红外效果最好。     

Growth and percolation of metal nanostructures in electrode gaps leading to conductive paths for electrical DNA analysis

Metal nanostructures are promising novel labels for microarray-based biomolecular detection. Additional silver deposition on the surface-bound labels strongly enhances the sensitivity of the system and can lead to continuous metal areas, which enable an electrical readout especially for simple and robust point-of-care analyses. In this paper, atomic force microscopy (AFM) was used to study different routes of metal deposition on labelled DNA-DNA duplexes in electrode gaps. Besides the well-established metal-induced silver enhancement, a recently introduced enzymatic silver deposition was applied and proved highly specific. The in situ characterization was especially focused on the nanostructure percolation-the moment at which the nanoparticulate film becomes continuous and electrically conducting. The formation of conducting paths, continuous from one electrode to the other, was followed by complementary electrical measurements. Thereby, a percolation threshold was determined for the surface coverage with metal structures, i.e.?the required metallized area to achieve conductance. Complementary graphic simulations of the growth process and graphic 'conductance measurements' were developed and proved suitable to model the metal deposition and electrical detection. This may help to design electrode arrays and identify optimum enhancement parameters (required seed concentration and shell growth) as well as draw quantitative conclusions on the existing label (i.e.?analyte) concentration.     

Reactive deposition of ultrafine cobalt powders

The particle size distributions of cobalt powders prepared by reactive deposition were examined and correlated with the deposition condition. In reactive deposition, a Co(OH)₂ colloid layer was formed at the electrode surface upon reduction of dissolved oxygen. The colloid layer accelerated the decrease in interfacial Co²⁺ concentration and inhibited crystal growth of the metal, and was therefore instrumental in the formation of fine cobalt particles. The powders from reactive deposition were statistically a factor of two finer and of more uniform size distribution than those from normal electrodeposition. It was found that both the reactive deposition of cobalt powders and the reactive deposition of porous cobalt structures were driven by the same kinetic factors, namely the requirement of maintaining an effective presence of the Co(OH)₂ colloid layer at the electrode surface. Hence a similar dependence on deposition conditions for both processes was obtained.     

The incorporation of preformed metal nanoparticles in zinc oxide thin films using aerosol assisted chemical vapour deposition

The feasibility of Aerosol Assisted Chemical Vapour Deposition (AA-CVD) has been investigated for the growth of zinc oxide (ZnO) films containing preformed metal nanoparticles. The deposition parameters were first established for ZnO thin films, by varying the heating configuration, substrate temperature and deposition time. Films were characterised using Scanning Electron Microscopy and X-Ray Diffraction. As-deposited films, grown at 250 °C, were mostly amorphous and transformed to highly crystalline Wurtzite ZnO at higher substrate temperatures (400-450 °C). A change in the preferential orientation of the films was observed upon changing (i), the substrate temperature or (ii), the heating configuration. Following this, the applicability of the AA-CVD process for the incorporation of preformed nanoparticles (platinum and gold) in ZnO thin films was investigated. It was found that surface agglomeration occurred, such that the ZnO films were capped with an inhomogeneous coverage of the metal. These layers were characterised using Transmission Electron Microscopy and Electron Diffraction. A possible mechanism for the formation of these metal surface clusters is presented.     

The importance of the energetic species in pulsed laser deposition for nanostructuring

This work reports on the optical and structural properties of nanostructured films formed by Ag nano-objects embedded in amorphous aluminium oxide (a-Al(2)O(3)) prepared by alternate pulsed laser deposition (PLD). The aim is to understand the importance of the energetic species involved in the PLD process for nanostructuring, i.e.?for organizing nanoparticles (NPs) in layers or for self-assembling them into nanocolumns (NCls), all oriented perpendicular to the substrate. In order to change the kinetic energy of the species arriving at the substrate, we use a background gas during the deposition of the embedding a-Al(2)O(3) host. It was produced either in vacuum or in a gas pressure (helium and argon) while the metal NPs were always produced in vacuum. The formation of NPs or NCls is easily identified through the features of the surface plasmon resonances (SPR) in the extinction spectra and confirmed by electron microscopy. The results show that both the layer organization and self-assembling of the metal are prevented when the host is produced in a gas pressure. This result is discussed in terms of the deceleration of species arriving at the substrate in gas that reduces the metal sputtering by host species (by ≈58%) as well as the density of the host material (by ≥19%). These reductions promote the formation of large voids along which the metal easily diffuses, thus preventing organization and self-organisation, as well as an enhancement of the amount of metal that is deposited.     

Formation of Au nanostructures through an alumina mask by laser-assisted deposition

We report a new method to produce ordered arrays of metal nanostructures on substrates. The method employs a through-hole nanoporous alumina membrane as a mask that is attached onto the substrate, silicon in this study. The material of deposition, Au in this study, was provided by pulsed laser ablation of a target gold. At an early stage of the deposition, a significant portion of Au penetrated the alumina through-holes and formed an ordered nanodot array on the silicon surface. At the later stage, the through-hole deposition was blocked by the growth of Au film on the top surface of the alumina, so that the heights of the Au nanodots were limited to about 10 nm under current experimental conditions. Subsequent attempts to clean up the top surface of the alumina with a lower power laser illumination resulted in the formation of new nanostructures around the alumina pores, nanospheres, or nanorings, depending on the fluence of the laser and the duration of the cleanup. We will discuss the underlying mechanism of the formation of these nanostructures.     

Synthesis of 1D regular arrays of gold nanoparticles and modeling of their optical properties

Self-organized formation of uniform coating of semiconductor substrate by metal nanoparticles offers a convenient and efficient access to large-scale arrays of uniform metal-semiconductor nanostructures. We used a cheap and facile method of photoinduced chemical gold deposition from an aqueous or alcohol gold salt solution onto semiconductor surface (GaAs, InP). By controlling of both the solution composition and the deposition conditions, gold particles of 10-50 nm in diameter were obtained and the gold covering degree of the semiconductor surface was varied in a wide range. Morphology of the nano/micro structures formed was characterized by atomic force microscopy and scanned electron microscopy with local element analysis. The investigations show that the semiconductor surface patterning can be used for the selective deposition of gold nanoparticles, because they are located predominantly at the tops of the microrelief. We have used specially textured by the anisotropic chemical etching microrelief surfaces of semiconductor single crystal as templates and have obtained nanoparticle arrays in the shape of 1D systems of near parallel quasiperiodical wires. For the periodic 1D array of metal nanowires built into the air-semiconductor interface the spectral and angular dependencies of the transmittance/reflectance of the polarized light have been obtained theoretically using differential formalism. These dependencies demonstrate non-monotonic behaviour at surface plasmon polariton excitation conditions and show possibility of designing functional subwavelength devices.     

Self-assembly of organic acid molecules on the metal oxide surface of a cupronickel alloy

Corrosion of the metal oxide surface of cupronickel (CuNi) alloys is a problem in applications such as household water pipes, industrial pipelines, and marine vessels. On other substrates, thin films have been used as barriers to corrosion. Here, the formation of self-assembled monolayers (SAMs) on the CuNi metal oxide surface has been investigated. Stable, well-ordered SAMs of octadecylphosphonic acid (ODPA) and 16-phosphonohexadecanoic acid (COOH-PA) were formed on the metal oxide surface of CuNi foils (55% Cu/45% Ni) using a solution deposition method. The ODPA modified surfaces could be used to provide a non-reactive barrier that inhibits corrosion of the CuNi metal oxide surface. Meanwhile, COOH-PA films could be used for further surface reactions such as surface initiated polymerization, in which polymer coatings are grown directly from a well-ordered film. Film-modified surfaces were characterized using diffuse reflectance infrared Fourier transform spectroscopy, contact angle analysis, and matrix assisted laser desorption ionization time of flight mass spectrometry. The ability of the films to inhibit corrosion by limiting oxidation of the CuNi surface was assessed using cyclic voltammetry.     

金属表面均三嗪二硫醇纳米聚合薄膜研究进展

综述了均三嗪二硫醇类化合物纳米聚合薄膜在各种金属基底表面的光聚合、热聚合、蒸发聚合及电化学聚合制备方法及在金属防护、材料间粘接、润滑特性、介电特性、超疏水和作为重金属离子处理剂等方面的应用。对该类化合物在不同金属表面的吸附作用和聚合机理进行了归纳、讨论与分析。提出了通过对该类三嗪二硫醇化合物分子进行改性研究,可在金属表...     

电子束沉积SiC/ZrO2热防护层的结构优化及其抗热震性能

高性能辐射热防护层是高超声速飞行器金属热防护系统的重要组成部分。为获得高性能的热防护层,利用L5 EB-PVD电子束物理气相沉积设备在Haynes 214镍基合金表面沉积了SiC/ZrO2防护层,测试了其在热循环条件下的抗热震性能;通过分析其沉积温度及厚度对残余热应力的影响,确定了热防护层的沉积工艺参数。结果表明:热防护层在800℃和900℃循环80次后未出现明显的宏观裂纹;1000℃循环60次后,SiC表面层应力集中区出现裂纹,在交变热应力作用下,裂纹不断扩展形成网状龟裂纹,最终导致热防护层剥落;热膨胀系数不匹配导致热防护层在急冷急热热震过程中产生热应力是导致其失效的主要原因。     

Fabrication of slantingly-aligned silicon nanowire arrays for solar cell applications

Large-area slantingly-aligned silicon nanowire arrays (SA-SiNW arrays) on Si(111) substrate have been fabricated by wet chemical etching with dry metal deposition method and employed in the fabrication of solar cells for the first time. The formation of SA-SiNW arrays possibly results from the anisotropic etching of silicon by silver catalysts. Superior to the previous cells fabricated with vertically-aligned silicon nanowire arrays (VA-SiNW arrays), the SA-SiNW array solar cells exhibit a highest power conversion efficiency of?11.37%. The improved device performance is attributed to the integration of the excellent anti-reflection property of the arrays and the better electrical contact of the cell as a result of the special slantingly-aligned structure. The high surface recombination velocity of minority carriers in SiNW arrays is still the main limitation on cell performance.     

Formation of Ultrafine Metal Particles and Metal Oxide Precursor on Anodized Al by Electrolysis Deposition

1. IntroductionThe oxide film formed on Al by anodizing in acidelectrolytes, e.g.j aqueous sulfuric, oxalic, and phosphoric acid solutions, has a fine porous structure.The pores are open at outer side as shown in Fig.1.The pore dimension is well controllable; its value depends strongly on anodizing electrolyte, moderatelyor weakly on solution concentration, temperature andapplied voltage. When anodizing electrolyte, concentration and temperature are selected, there is a simplerelation between…     

Self-assembly functionalized membranes with chitosan microsphere/polyacrylic acid layers and its application for metal ion removal

Multilayer composite membranes with high removal capability for metal ion were prepared using electrostatic self-assembly (ESA) technique. Especially, self-assembled multilayer of chitosan microspheres and PAA were formed onto charged surface of polyacrylonitrile (PAN) membranes. It was confirmed that the alternate multilayer of chitosan and PAA were deposited on the base membrane surface. The formation of the ESA layer-by-layer of chitosan/PAA or chitosan microspheres/PAA onto the base membrane surface functionally equipped the membrane with removal capability for Cu²⁺. Especially, membranes with chitosan microspheres/PAA ESA layers on the surface showed relatively higher adsorption capability as compared with membranes with chitosan/PAA ESA layers. Besides, the influence of the pH of metal ion solution on the metal ion adsorption property of ESA modified membrane was investigated. It was proposed that the layer-by-layer self-assembled deposition of chitosan microspheres would be a new approach to functionalize membrane with high adsorption capability for metal ions.     

Deposition of platinum clusters on surface-modified Tobacco mosaic virus

Nanoscaled Pt conductors were prepared from genetically engineered Tobacco mosaic virus (TMV) templates through Pt cluster deposition on the outer surface of the TMV. Pt clusters were synthesized and deposited on the engineered TMV with surface-exposed cysteine via the in situ mineralization of hexachloroplatinate anions. This deposition was driven by the specific binding between thiols and the solid metal clusters. In addition, Pt-thiolate adducts are suggested to form on the engineered TMV in aqueous solutions that work as nucleation sites for the formation of the Pt clusters. The specific binding between Pt clusters and the engineered TMV template was investigated using UV/vis spectrophotometry and quartz crystal microbalance (QCM) analysis. The electric conductance of Pt-deposited TMV was greater than that of the uncoated TMV virion particles. This result suggests the application of metal cluster-deposited engineered TMV in future electrical devices such as rapid response sensors.     

Electrophoretic deposition of nanobiocomposites for orthopedic applications: influence of current density and coating duration

Frequently metal implants undergo detachment from the host tissue due to inadequate biocompatibility and poor osteointegration. In view of this, bioactive porous apatite-wollastonite/chitosan nanocomposite coating was prepared using electrophoretic deposition (EPD) technique in the present work. The effect of coating duration and current density on surface characteristics of the nanocomposite coating was assessed using optical microscope and scanning electron microscope. EPD led to the formation of thick and homogeneous coating. Adhesion of the composite coating on titanium substrate was evaluated using tape test and bioactivity of the coatings was studied by immersing in simulated body fluid (SBF). The coating with higher current density and longer coating duration was found to be suitable with improved adhesion and bioactivity for intended metal implants.