Physical and chemical phenomena occurring between solid ceramics and liquid metals and alloys at laser and plasma composite coatings formation: A review

The review describes the physical and chemical phenomena occurring between solid ceramics used as reinforcement and liquid metals and alloys used as matrix in the composite coatings. Initially, the properties of typical matrix metals as Ni, Co, Fe and alloys as Ni-based (NiCr, NiAl, NiCrAlY,…) and Co-based (Stellites) alloys in liquid state are described. Then, the phenomena related to the diffusion of some atoms such as nitrogen or carbon in liquid metals and alloys solidification are described. Subsequently, the phenomena at the interface between liquid metals and alloys and solid ceramics such as oxides or carbides during the coatings' formation are reviewed. Finally, the methods of composite coatings deposition using laser cladding and plasma transferred arc are described and the properties of the composite coatings related to their microstructure are discussed by taking into account the phenomena in melt-pool.     

Interaction of beam and coated metals at high power continuous irradiation

The beam-matter interaction with various coating effects has received continued attention in the high power laser community. Previous works suggest that coatings promote target damage when compared to beaming on uncoated surface. Three types of paint coatings (acrylic urethane, silicone alkyd and stealth blend) and a water coat on metals (Al, Ti and STS) are irradiated with a CO₂ laser. Both strain and temperature measurements are provided for assessing the instantaneous response characteristics of each coating on different metals. A selective combination of surface coats with metals has been proven to be effective in either preventing or enhancing damage, both thermal and mechanical, associated with focused beaming on a target.     

Low-temperature biomimetic formation of apatite/TiO2 composite coatings on Ti and NiTi shape memory alloy and their characterization

Through a low temperature process, a bilayer composite coating was formed on Ti and NiTi shape memory alloy (SMA). The composite coating consisted of a layer of titania, which was formed using a H₂O₂-oxidation and hot water aging technique, and a layer of apatite, which was formed through an accelerated biomimetic process by immersing as-oxidized metals in a high-strength simulated body fluid (5SBF). Various techniques including X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the surfaces of samples at different stages of coating formation and the coatings formed. Bioactive apatite/TiO₂ coatings could be formed on NiTi SMA and firmly bonded to the metal substrate. But there were differences for the formation of the composite coating on Ti and NiTi SMA substrates. The composite coatings formed will render both metals bioactive and hence bone-bonding.     

Deposition of duplex Al2O3/aluminum coatings on steel using a combined technique of arc spraying and plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) is a cost-effective technique that can be used to prepare ceramic coatings on metals such as Ti, Al, Mg, Nb, etc., and their alloys, but this promising technique cannot be used to modify the surface properties of steels, which are the most widely used materials in engineering. In order to prepare metallurgically bonded ceramic coatings on steels, a combined technique of arc spraying and plasma electrolytic oxidation (PEO) was adopted. In this work, metallurgically bonded ceramic coatings on steels were obtained using this method. We firstly prepared aluminum coatings on steels by arc spraying, and then obtained the metallurgically bonded ceramic coatings on aluminum coatings by PEO. The characteristics of duplex coatings were analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The corrosion and wear resistance of the ceramic coatings were also studied. The results show that, duplex Al₂O₃/aluminum coatings have been deposited on steel substrate after the combined treatment. The ceramic coatings are mainly composed of α-Al₂O₃, γ-Al₂O₃, θ-Al₂O₃ and some amorphous phase. The duplex coatings show favorable corrosion and wear resistance properties. The investigations indicate that the combination of arc spraying and plasma electrolytic oxidation proves a promising technique for surface modification of steels for protective purposes.     

Laser–Arc Treatment of Iron–Carbon Alloys with Emissive Coatings and of Carbon–Carbon Composites

The conditions for stabilization of the sustaining spot of an electric arc on the surface of metals and carbon-graphite materials in a wide range of laser-radiation intensities are studied. The use of a laser–arc source with a low intensity of laser radiation and a reverse-polarity arc is substantiated physically for efficient surface treatment of metals with emissive coatings and of carbon–carbon composites.     

Polarization independent broadband terahertz antireflection by deep‐subwavelength thin metallic mesh

Broadband antireflection coatings for passive terahertz (THz) components are extremely important in the application of THz technology. Metallic nano‐films are commonly used for this purpose. Here a new approach to realize polarization independent broadband antireflection in THz range, based on a meta‐surface design is experimentally demonstrated. The internal reflection of a broadband THz pulse (spectral bandwidth of 0.06 – 4 THz) at a Si/air interface can be fully suppressed with a Cr square mesh with deep‐subwavelength dimensions. Small nonuniformity of the meta‐surface structure can enhance the tolerance on structural parameters for achieving the AR condition. The design concept is applicable to other metals and frequency ranges as well, which opens a new window for future AR coatings.     

High performance corrosion resistant polyaniline/alkyd ecofriendly coatings

The growing environmental concerns have led to the formulation of new coating strategies by employing inherently conductive polymers (ICPs) as a key component in order to eliminate the toxic heavy metals from protective coatings. Also, the renewable resources are given increasing priority within chemical industry and the energy community. Emphasis is therefore, processing of polymers from renewable resources which show advantages when compared with petrochemical raw materials and are regarded as an ideal raw material. The present work reports the investigations on the corrosion-resistance performance of soya oil alkyd, containing nano polyaniline (PANI) against mild steel (MS). The corrosion-protective performance was evaluated in terms of physico-mechanical properties, corrosion rate, open circuit potential measurements (OCP) and scanning electron microscopy (SEM) studies. The performance was compared to the reported PANI coatings.     

Mechanically stable and corrosion resistant superhydrophobic sol-gel coatings on copper substrate

Development of the anticorrosion coatings on metals having both passive matrix functionality and active response to changes in the aggressive environment has raised tremendous interest in material science. Using a sol-gel deposition method, superhydrophobic copper substrate could be obtained. The best hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water (as 7 M NH₄OH) at a molar ratio of 1:19.1:4.31 respectively. The surface morphological study showed the ball like silica particles distributed on the copper substrate with particle sizes ranging from 8 to 12 μm. The coatings showed the static water contact angle as high as 155° and the water sliding angle as low as 7°. The superhydrophobic nature was maintained even though the deposited copper substrate was soaked for 100 h in 50% of HCl solution. The coatings are stable against humidity and showed superhydrophobic behavior even after 90 days of exposure. The coatings are mechanically stable and water drops maintained the spherical shape on the bent copper substrate, which was bent more than 90°.     

A simple method for preparation of transparent hydrophobic silica-based coatings on different substrates

A facile, inexpensive, and general approach is explored for the fabrication of transparent silica/organic silicon hybrid sol, which could form transparent hydrophobic coatings on different substrates conveniently. The sol was prepared by using hexamethyldisilazane (HMDS) as a surface-modifying agent and the source of base catalyst required for the hydrolysis of tetraethoxysilane (TEOS). The resulting silica-based coatings on glass slide have shown an optical transmission over the visible range up to 89% (in reference to 100% transmission defined by a plain glass substrate) and high thermal stability. The water contact angle of the film reached 152^○. Hydrophobic coatings with excellent optical transmittance were also successfully formed on writing paper and aluminum foils. The transparent hydrophobic silica-based hybrid sol will have potential applications in creating outdoor building glass, protecting paper files from moisture and preventing metals from corrosion.     

The state of the art and prospects of detonation-synthesis nanodiamond applications in Belarus

Technological features of the commercial production of detonation-synthesis nanodiamonds at the SINTA Joint-Stock Company and the characteristics of the nanodiamonds and diamond-containing mixtures produced are considered. Nanodiamond applications in the production of composite electrolytic coatings that are based on chromium, nickel, gold, and silver, exhibit good service properties, and save on the use of noble metals and electric power are exemplified. Nanodiamond applications for the modification of plastics, antifriction lubricants, and oxide coatings grown by microarc oxidation of aluminum alloys are also considered. The prospective application of nanodiamonds as a raw material in the synthesis of diamond powders and superhard composites by static and shock-wave loading is demonstrated.     

Significant influence of particle surface oxidation on deposition efficiency, interface microstructure and adhesive strength of cold-sprayed copper coatings

The critical velocity for particle deposition in cold spraying is a key parameter, which depends not only on the material type, but also the particle temperature and oxidation condition. The dependency of deposition efficiency of cold spray Cu particles on the particle temperature and surface oxidation was examined. The effect of particle surface oxide scales on the interfacial microstructure and adhesive strength of the cold-sprayed Cu coatings was investigated. The results show that the deposition efficiency significantly increases with increasing the gas temperature but decreases with augmenting the oxygen content of the starting powder. The oxide inclusions at the interfaces between the deposited particles inhibit the effective bonding of fresh metals and remarkably lower the bond strength of the deposited Cu coatings on steel.     

Properties of ZnO in dependence on method of preparation and size distribution in coatings

The problem of environmental protection set strict limits for the use of toxic pigments (e.g., lead, cadmium and other heavy metals). At present, a new generation of pigments called environmental friendly is looked for elimination of these heavy metals. The aim of this work was preparation of different kinds of zinc oxide by various methods, the characterization of these particles and subsequently to pass judgment on their anticorrosion efficiency in coatings.     

管状铝质材料的等离子体电解沉积行为研究

对管状铝质材料的等离子体电解沉积行为进行了研究.测试了不同工作电压和不同电极放置模式条件下铝管内部不同位置的电位分布，并通过显微分析观察，对比了不同电极放置模式对铝管内外壁陶瓷沉积层生长情况的影响.结果表明，不同的电极放置模式下，铝管内外壁陶瓷沉积层生长情况有很大差异.这是因为不同的电极放置模式对铝管内的电场分布具有很大影响，进而影响到铝管内外壁陶瓷层的沉积过程.只有外电极时，由于电场屏蔽作用，不能在铝管内壁形成均匀陶瓷层；在铝管内部加入辅助中心电极后，铝管内部产生均匀电场，这有利于在其内壁形成均匀的陶瓷层. 关键词： 等离子体电解沉积 铝管 表面改性 陶瓷层     

Features of microarc oxidation coatings formation technology in slurry electrolytes

A group of electrolytes composed of different powders entered into electrolyte presents a separate direction in microarc oxidation (MAO) technology. This group of electrolytes is most complex and however it has not been sufficiently studied yet. This paper shows that addition of powders of different nature into electrolyte influences both on properties of obtained coatings and on speed of their formation. The MAO-coatings formed in similar electrolytes-suspensions or slurry electrolytes (SE) contain in their composition an essential share of powder material entered into electrolyte as corpuscles of disperse phase (DP). Different nonmetallic combinations are used: oxides, carbides, borides, nitrides of metals and others. The particular conditions of microarc discharge regime (high temperature and pressure in a zone of breakdown) cause a thermolysis of electrolyte together with weighed corpuscles of solid matter, the realization of plasma chemical reactions on oxidizing surface and provide the synthesis of chemical combinations in an oxide matrix. A new composition of slurry electrolyte which allows improving the quality of obtained coatings on the basis of held investigations was developed.     

A Review of Advanced Composite and Nanostructured Coatings by Solid-State Cold Spraying Process

Cold spraying (CS) has been widely explored over the last decade due to its low process temperature and limited thermal effect on spray materials. As a solid-state process, the inherent deficiencies of traditional thermal spraying such as oxidation, decomposition, and grain growth are avoided. This article summarizes the research work on the fabrication of composites and nanostructured coatings by the promising CS process. After a brief introduction to CS and its deposition mechanisms, the preparation methods of spray powders are classified. Different methods are appropriate for particles of various properties, and the tendency is to design composite powders by combined methods in order to create coatings with specified properties. Then, the co-deposition mechanism of composite particles as well as research findings on metal–metal, metal–ceramic, and metal–intermetallic composite coatings are reviewed concerning the deposition characteristics, microstructure and its relation to properties. Moreover, CS has been used to deposit a variety of nanostructured materials, including metals, metal–ceramic composites, and even ceramics, retaining their nanocrystalline nature in the coating without grain growth or phase transformation. Finally, the potential applications of CS and issues to be addressed in coating deposition are discussed.     

水性涂料中可溶性铅、镉、铬和汞的测定

本文研究了测定水性涂料中可溶性铅、镉、铅和汞的影响因素。结果表明，铅、镉、铬和汞的影响因素。结果表明，铅、镉、铬和汞的溶出量主要取决于酸度、时间、温度、搅拌速度以及膜干燥方式和干燥程度等因素。本法6次测量的相对标准偏差均小于5．5％。     

Structure and properties of copper coatings electrodeposited under X-ray radiation

142-145The influence of X-ray radiation of different wave lengths on the structure and properties of electrodeposited copper coatings is found. It is determined by the methods of X-ray structure analysis and optical and scanning microscopy that, in the process of electrodeposition, X-ray radiation changes the primary structure of electrolyte and leads to a decrease in the grain size of deposits and an increase in the microhardness and degree of dispersion of mosaic blocks. The radiation effect on the process of electrodeposition is accompanied by an increase in the rate of material deposition on the cathode due to intensification of the diffusion of electrolyte components to the cathode.     

三类构型激光脉冲压缩器光栅拼接误差容限比较

建立了包含拼接光栅的三类典型构型(双程Z型、X型及菱型)激光脉冲压缩器的理论模型. 利用光线追迹法计算压缩器引入的相位变化,结合傅里叶变换的方法仿真分析并比较了各压缩器相应的光栅拼接误差容限. 以远场焦斑峰值能量下降到理想值的0.9倍为限确定了三类压缩器光栅拼接误差容限,明确了不同构型激光脉冲压缩器对拼接误差的敏感程度. 这对脉冲压缩器的选型和设计具有指导意义. 关键词： 光栅拼接 脉冲压缩 误差容限 光线追迹     

On the origin of sonoluminescence and sonochemistry

Recent experimental results on the origins of sonoluminescence and sonochemistry are reviewed and the conclusion reached that most observed effects originate from thermal processes associated with a localized hot-spot created by acoustic cavitation. Sonoluminescence is definitively due to chemiluminescence from species produced thermally during cavitational collapse and is not attributable to electric microdischarge. Homogenous sonochemistry follows the behaviour expected for high temperature thermal reactions. Ultrasonic irradiation of liquids containing solid powders dramatically increases their chemical reactivity and improves chemical yields for a wide range of synthetically useful heterogenous reactions. Shock waves generated from the cavitational hot-spot cause high velocity interparticle collisions in such slurries. Brittle solids are shock fragmented, which increases surface area. This increase in reactive surface provides for substantial increases in chemical reactivity. For malleable metal powders, these collisions are sufficiently violent to remove surface oxide coatings and to induce local melting at the site of impact for most metals.