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Highly efficient shielding materials with an excellent electromagnetic wave absorption have gained increased attention. A new design was used to provide cellulose paper with a high electromagnetic shielding effectiveness (EMI SE) and improve the absorption performance by constructing an asymmetry sandwich structure that consisted of a dense nickel coating, Fe 3 O 4 nanoparticles and a porous nickel layer. This unique structure caused a "multiple reflection-absorb-reflection" process when the electromagnetic waves penetrated the sample. The EMI absorption (SE A ) and total SE (SE T ) increased with Fe 3 O 4 absorption time increasing at 8.2-12.4 GHz, which was attributed to the synergistic effect between porous nickel layer and Fe 3 O 4 nanoparticles. The SE A and SE T of the sample with a thickness of 0.195 mm can achieved 18.57 and 41.88 dB, respectively. The design was conducive to improving the magnetic and corrosion resistance properties. This study provided a novel path to obtain a low cost and lightweight electromagnetic shielding material that can reduce secondary radiation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Dissimilarities in metal laser welding lead to brittleness in welded joints due to differences in the thermophysical and chemical properties between dissimilar base materials. To overcome such brittleness, the addition of a preset coating onto the base materials as an interlayer is a method for attaining reliable welded joints. Nd:YAG laser butt welding of DP590 dual-phase steel and 304 stainless, both with a thickness of 1 mm, was performed with a preset nickel coating as an interlayer using an electroplating process. The relationship between the microstructure and the mechanical properties of the welded joints was researched, the microstructure and composition of the weldment were analyzed, and the microhardness, tensile strength and corrosion resistance were tested. The results showed that the preset nickel coating increased the content of Ni element in the welded joints, which is beneficial to the formation of lath martensite. The average hardness of the welded joints increased by 12%, and the tensile strength was higher than 370 MPa. The corrosion rate of the welded joints can be slowed down, and the corrosion resistance can be improved by increasing the nickel coating. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized CDs endow a compacted carbon dot/nickel coating with superior mechanical properties. • Efficient Self-lubricating CDs contribute to excellent tribology for carbon dot/nickel coating. • High penetrating energy barrier of Cl makes CDs to be an excellent inhibitor. • Carbon dot/nickel coating provides an effective controlling wear and corrosion to Mg alloy. Due to their self-lubrication and corrosion inhibition properties, carbon dots (CDs) were utilized to endow a nickel coating on a magnesium alloy substrate with superior tribology and anti-corrosion properties. The surface and cross-sectional morphologies confirm that these novel carbon dots remarkably improve the compactness of the nickel coating, leading to much higher hardness and adhesion strength. The carbon dot/nickel coating prepared with 0.5 g/L CDs has a lower wear rate and friction coefficient than the other coatings, demonstrating its excellent self-lubricating performance. Moreover, as demonstrated by electrochemical tests and the formation of corrosion products, this coating exhibits significantly enhanced anti-corrosion performance, with the lowest corrosion current and largest impedance modulus among the prepared coatings. Theoretical calculations confirm that the CDs provide a high energy barrier for the penetrating diffusion of Cl. Thus, the CDs effectively prevent the active penetration of corrosive substances. As a result, the as-prepared carbon dot/nickel nanocomposite coatings can efficiently control the wear and corrosion failures of Mg alloy under some harsh conditions. [ABSTRACT FROM AUTHOR]

The effects of nickel coating and heat treatment on the interfacial bonds of aluminum–iron (Al/Fe) alloys hybrid structures were investigated using microstructural analysis. The application of a nickel coating successfully suppressed the formation of defects such as gaps and oxide scale, improving the physical bonding of the interface. Optimizing the heat treatment conditions generated superior chemical bonding at the interface and facilitated the formation of a nickel-bearing phase in the Al matrix. Also, the types of nickel-bearing phase were influenced by solution treatment and proximity to the interface. By analyzing the isopleth phase diagram of the aluminum system for the ranges of nickel present in the Al, it was confirmed that the Ni:Cu ratio affected the precipitation characteristics of the system. However, when heated under conditions that were optimized for chemical bonding, the Al matrix decreased by approximately 40% (from 100 HV to 60 HV), due to grain growth. The effect of artificial aging increased the hardness of the Al matrix away from the interface by 35% (from 63 HV to 90 HV). On the other hand, this did not occur in the Al matrix near the interface. These results indicate that the nickel that diffused into the Al matrix interfered with the precipitation hardening effect. [ABSTRACT FROM AUTHOR]

In this study, a novel non-enzymatic glucose sensor was successfully produced using nickel electrodeposition on an oil free carbon nanofiber (CNF) mat prepared by electrospinning method. The as-prepared Ni/CNF mat electrode was studied by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The characterization results showed that not only was nickel coating electrodeposited on the CNF mat but also the nickel coating was uniformly deposited on the CNF mat electrode. The electrochemical properties of Ni/CNF mat were evaluated using cyclic voltammetry (CV) and amperometry measurements. It was found that the Ni/CNF mat electrode had good electrocatalytic activity toward the oxidation of glucose and demonstrated a wide linear range of 0.002–5 mM, a low detection limit of 0.57 µM, a rapid response time (2 s), a high selectivity with no interference from other oxidable species, good reproducibility and long-term stability. Moreover, the prepared sensor was used to identify glucose in real sample species. Therefore, Ni/CNF mat electrode due to good analytical performance, cost effective and simple preparation method can be proposed as a promising sensor for non-enzymatic glucose detection. [ABSTRACT FROM AUTHOR]

Abstract The main aim of this paper is to investigate the effect of the coating layer on the thermal properties of Ni-coated graphene sheets. In this regard, non-equilibrium molecular dynamics simulations have been carried out to provide detailed information on the thermal properties of Ni-coated graphene sheets. It has been observed that with increasing coating ratio to 0.5 % , the thermal conductivity reduces to only about 60 % of the corresponding value for the pristine graphene. However, by increasing the coating ratio, thermal conductivity converged to an asymptotic value at the coating ratio equals to 2 %. Keeping this coating percentage fixed, nickel atoms are also distributed on the graphene sheet in different patterns such as random half-side coating, spectral, agglomerated, checkered and strips. It is revealed that by using different nickel coating patterns, thermal properties of the pristine graphene can be highly tunable. Highlights • Thermal conductivity of Ni-coated graphene utilized in lead-free solders is studied. • Effect of Ni coverage on the thermal conductivity of graphene is examined. • Ni coating ratio of 0.5% reduces the thermal conductivity about 60%. • Increasing the ratio to 2%, thermal conductivity converges to an asymptotic value. • Thermal properties of graphene can be highly tunable by different coating patterns. [ABSTRACT FROM AUTHOR]

The basic hypothesis of the research was that the structure of the coating, i.e. the type of defects, affects the mechanical and electrochemical properties, as well as the resistance to cavitation erosion and corrosion. For this purpose, nickel coatings produced by brush-plating technology using two different electrolytes and deposited on X20Cr13 steel were tested. The electrolytes affected the structure and properties of the coatings: one coating had a network of cracks, and the second one had a "cauliflower-like" structure. The hardness and Young's modulus of both coatings were investigated under multi-cycle loading modes. Cavitation erosion resistance was tested in a cavitation tunnel equipped with a barricade system at an inlet pressure of 600 kPa and outlet pressure of 120 kPa. Both nickel coatings protected the substrate against cavitation erosion. The lowest rate of cavitation erosion had a coating with a network of cracks and high hardness. Microscopic examinations showed no influence of the net of cracks on the degradation process. Electrochemical tests confirmed the better corrosion resistance of the compact coating. The compact coating had about an order of magnitude lower corrosion potential and about 100 mV higher corrosion current density than that of the agglomerate coating. The agglomerate coating had electrochemical parameters comparable to the substrate. • Two nickel coatings were produced using brush plating technology. • The nickel electrolyte affected coating structure and properties. • Coating structure affected resistance to cavitation erosion and corrosion. • The net of coating cracks did not reduce CE resistance. [ABSTRACT FROM AUTHOR]

In this study, nickel coating was electrodeposited on low carbon steel (LCS) surface. The effect of current density on surface morphology, crystal orientation and wettability of nickel coatings were comparatively studied. The abrasive resistance of coatings was carried out by self-made equipment. Moreover, the corrosion resistance of the surfaces was investigated by potentiodynamic polarization curves as well as electrochemical impedance spectroscopy (EIS) in the corrosive medium of 3.5 wt.% NaCl solution. The results showed that the surfaces present a micro-nano structure at the current density of 6 A/dm 2 and 8 A/dm 2 , and exhibit superhydrophobicity after modification with myristic acid. The crystal orientation changed with the variation of current densities. It is worth noting that the surface deposited at 6 A/dm 2 showed excellent mechanical stability after abraded by sandpaper for 10 times with interesting bouncing behavior. Moreover, electrochemical measurements showed that the corrosion potential (E corr ) of superhydrophobic surface was ascended from − 0.447 V to − 0.186 V, and the EIS value was up to 1.04 × 10 5 Ω cm 2 , indicating excellent corrosion resistance. The corrosion mechanism is illuminated via equivalent circuits. [ABSTRACT FROM AUTHOR]

Combustion of aluminized solid propellants exhibits phenomena associated with accumulation, agglomeration, ignition, and combustion of micro and nano-size aluminum particles. In general, agglomeration is an undesirable phenomenon, as it turns small particles into relatively large agglomerates, each containing many original particles, resulting in long combustion times which may lead to incomplete reaction, reduced jet momentum, and enhanced slag formation which adds parasite mass and may damage the motor insulation. This article presents a physical mechanism explaining the agglomeration process, revealing that small particles tend to agglomerate more than large particles. In addition, it suggests ways to reduce agglomeration of the aluminum particles via nano-coatings generating reactive heating and promoting ignition. [ABSTRACT FROM AUTHOR]

The wetting of some nonmetals coated with nickel and deposited in vacuum at 700°C using molten aluminum is studied. The sessile drop method and capillary purification are used. The threshold thickness of wetting is 150 nm for most materials and 400 nm for basalt. The high degree of wetting is observed because the metal melt wets better metal coatings than coated nonmetallic materials. Moreover, exothermic reactions to form aluminum nitrides take place in the system. [ABSTRACT FROM AUTHOR]

Protective coatings with superior corrosion resistance and enhanced mechanical properties are still greatly required when applied in challenging environments. In this paper, nickel-graphene oxide nanocrystalline coatings with uniform structure have been fabricated by co-electrodeposition technique. Effects of graphene oxide (GO) in plating solution and applied current density on structural, composition, crystallite size and corrosion-resistant properties of electrodeposited Ni-GO nanocrystalline coatings were compared and investigated systematically. The deposited coatings have a compact, crack-free, silver-gray appearance with lower surface roughness, exhibiting colonies-like morphology. The presence and uniform distribution of graphene oxide on the surface as well as inside nickel coating were confirmed. The crystallite size and crystal plane orientation have no significant alteration in the presence of graphene oxide. The preferred orientation of (200) crystal plane of pure Ni is changed to low energy (111) plane for Ni-GO composites. The average roughness R a of Ni-GO is 3–5 nm. Ni-GO coating contains 2.6–3.9 wt% GO, 95.5–96.9 wt% Ni and some oxygen. With the increase of GO, the corrosion resistance first enhanced to a maximum at 0.2 g L−1 GO. When GO exceeds a certain value, agglomeration occurred, causing uneven dispersion of GO and heterogeneous coarse surfaces. The anti-corrosion capability was enhanced by the incorporation of GO due to the grain refinement and the uniform dispersion of impermeable GO. Current density could change the structure and anti-corrosive features of Ni-GO coating. The Ni-GO nanocrystalline coating possesses enhanced performance, which has a promising application prospect in harsh environments. [Display omitted] • Ni-GO nanocrystalline coatings with uniform structure have been fabricated. • Effects of GO and current density on structural and properties were investigated. • Corrosion behaviors were evaluated by Tafel and EIS techniques. • Preferred orientation of (200) plane of Ni is changed to (111) for Ni-GO. • Corrosion and wear resistance were enhanced by incorporation of GO nanosheets. • Optimized process parameters for best wear and corrosion resistance were proposed. [ABSTRACT FROM AUTHOR]

Abstract: A non-traditional electrodeposition technique carried out under the condition of electrolyte reduced-pressure surface-boiling is presented in this paper. Using this kind of technique, favorably smooth nickel coatings without pinholes and nodules are unexpectedly plated at a rate of up to 0.81mm/h from an additive-free bath. Analysis using SEM, TEM and XRD indicates that, microstructure and properties of the nickel coatings change with increasing of applied current density. The nickel prepared electrochemically from a reduced-pressure boiling bath at 40A/dm2-69A/dm2 have a considerably high microhardness with a range of 300HV-500HV and a good acid resistance. In addition, it features a preferred orientation crystal face of (220). The change in the electrodeposition rate, microstructure and properties of the reduced-pressure electrodeposited nickel coatings mainly results from the comprehensive effects of vacuum degassing and boiling dynamics. The latter involves nucleation, growth, coagulation and burst of boiling bubble and can provide the nickel deposition process with several positive actions [Copyright &y& Elsevier]

Intermediary phases Ni-Al and Fe-Al are promising materials due to their superior properties such as hardness and good resistance against oxidation at high temperatures. Moreover, Fe-Al phases are resistant in sulphur - containing atmospheres. Because of these characteristics, the above mentioned intermetallic phases seem to be prospective for the use in many technical applications such as energetics, chemical or automotive industry in a form of a bulk material or coatings. Presently, the protective aluminide layer is usually prepared by thermal spraying. Nevertheless, this method is not suitable for complex-shaped components. Therefore, the aim of this work was to find an alternative way to prepare layers consisting of nickel or iron aluminides by other technique than thermal spraying. At first, carbon steel samples were coated using galvanic or electroless nickel plating. Coated samples were subsequently submerged into molten aluminium at various temperatures and process durations. The influence of the temperature and duration on the intermetallic phase growth was studied by scanning electron and light microscopy. Thickness and microhardness of the intermetallic layer was also measured. [ABSTRACT FROM AUTHOR]

Polycarbonate was reinforced with nickel coated carbon fiber and various composites were made by changing the fiber content. For comparative study, carbon fiber as such was also used to fabricate composites. Nickel coated carbon fiber was prepared by dip coating method. Scanning electron microscope studies indicated that the thickness of coating was in the rage of 1.0–1.8 µm on a 4–6 µm thick carbon fiber. Tensile and flexural properties of nickel coated carbon fiber composites were found to be higher than that of uncoated composites. Impact properties decreased with increase in fiber content in both coated and uncoated carbon fiber reinforced composites. Nickel coating decreased the notch sensitivity of composites. Significant improvement in abrasion properties were observed upon introduction of nickel coated carbon fibers. Dynamic mechanical analysis studies indicated increase in glass transition temperature with increase in nickel coated carbon fiber content. scanning electron microscope studies indicated uniform distribution of fibers. Two-step degradation was observed in air atmosphere. [ABSTRACT FROM PUBLISHER]

Continuous carbon fiber reinforced aluminum composite samples were produced by squeeze casting method, under applied pressures of 30, 50, and 70 MPa. For production of samples, nickel coated and uncoated carbon fibers with a mean volume fraction of 40% were used. After making the fiber preforms, they were preheated and then were replaced in a casting die. Molten 2024 aluminum alloy having a temperature of 750°C was poured into the die, and different amount of pressures were applied to infiltrate the melt into the carbon fiber bundles. The effect of applied pressure on infiltration mechanism and microstructure of the composite were studied, by evaluating the cross-section of the composite samples, using optical and scanning electron microscopes (SEM). The appropriate applied pressures for producing the composite samples for uncoated and nickel coated fibers were different, and the best results were achieved at 50 and 30 MPa, respectively. A specific or a certain range of pressure seems to be suitable for reaching to an appropriate microstructure in uncoated and coated samples. The results indicated that applying nickel coating on carbon fibers improves the infiltration of molten aluminum into the carbon fiber bundles and thus reduces the pressure required for infiltration significantly. [ABSTRACT FROM AUTHOR]

Abstract: Polyaniline (PANI) coatings were electrochemically synthesized on nickel (Ni) coated mild steel (MS) and their corrosion protection properties were investigated. In this work, the Ni layer (∼1μm thick) was electrodeposited on MS under galvanostatic condition. Thereafter, the PANI coating was deposited over the Ni layer from aqueous salicylate medium by using cyclic voltammetry. These bi-layered composite coatings were characterized by cyclic voltammetry, UV–vis absorption spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The corrosion protection properties of Ni coated MS (Ni/MS) and PANI coated Ni/MS (PANI/Ni/MS) were investigated in aqueous 3% NaCl by using open circuit potential (OCP) measurements, potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). It was shown that the top layer of PANI exhibits a lower porosity behavior with respect to Ni coating and reduces the corrosion rate of Ni/MS almost by a factor of 3500 and increases the lifetime of Ni coating. [Copyright &y& Elsevier]

Abstract: The effects of nickel coating on the torsional behaviors of single-walled carbon nanotubes (SWCNTs) subject to torsion motion are investigated using the molecular dynamics (MD) simulation method. The simulation results show that regardless of chirality, defect or radius, nickel coating can considerably enhance the critical torque of SWCNTs. However, by comparing the critical torsion angle between nickel-coated SWCNTs and corresponding pristine SWCNTs, it is found that nickel coating in small-radius nanotubes does induce a reduction in the critical torsion angle. The results also show that the structural failure of nickel coated imperfect (9,0) SWCNT occurs at an obviously higher critical torque in comparison with uncoated (9,0) SWCNT with a vacancy defect. Furthermore, we also find that the critical torque of a short nickel coated SWCNT is bigger than that of a long one, while the critical torsion angle for a short tube is smaller than that for a long one. [ABSTRACT FROM AUTHOR]

Nickel coating on the carbon–polythene composite plate was prepared by electrodeposition in a nickel sulfate solution in this work. The morphology and cross-sectional microstructure of the nickel coating were examined by scanning electron microscope (SEM) and optical microscope (OM), respectively. The influence of bath temperature on the nickel deposition rate was investigated experimentally. The adhesion between the coating and the substrate was evaluated by the pull-off test. The corrosion behavior of the coating in an aqueous solution of NaCl was studied by electrochemical methods. The results showed that the nickel electrodeposition rate could reach up to 0.68 μm min−1 on average under conditions of cathodic current density of 20 mA cm−2 and bath temperature of 60 °C. It was confirmed that increasing the bath temperature up to 50 °C had a positive effect on the nickel deposit rate, while an adverse effect was observed beyond 60 °C. The adhesion strength between the nickel coating and the substrate can be more than 2.3 MPa. The corrosion potential of the bright coating in the NaCl solution was more positive than that of the dull coating, and the anodic dissolution rate of the bright coating was also far lower at the same polarization potential compared with the dull coating. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to investigate the effect of current density on the grain size of electrodeposited nickel coatings. For this purpose, nanocrystalline nickel coatings were deposited from a Watts bath containing 5 g/l sodium saccharin as an additive, by direct current electroplating at different current densities. X-ray diffraction analysis and modified Williamson–Hall relation were used to determine the average grains size of the coatings. The experimental results showed that the coating grains size decreased sharply by increasing the current density from 10 mA/cm2 to 75 mA/cm2. Nanocrystalline nickel coating with average grain size smaller than 30 nm can be achieved at the current densities higher than 50 mA/cm2. Furthermore, a general and simple theoretical model based on atomistic theory of electrocrystallization has been made in order to find out the relationship between the grain size and current density. According to this model the variation of log (d) versus log (i) was linear which is in accordance with experimental results for the current densities lower than 75 mA/cm2. [Copyright &y& Elsevier]

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Nickel-yttria stabilized zirconia (Ni-YSZ) cermet is widely used as an anode material for solid oxide fuel cells (SOFCs). While the nickel-to-nickel chain maintains the electrical conductivity path, the YSZ contributes to lowering the thermal expansion and inhibits nickel coarsening during high temperature (1000 °C) operation. An electroless technique is employed to prepare a uniform nickel coating on the YSZ powder. The process parameters for this technique are optimized. Notably, the cermet thus prepared shows percolation at a much lower nickel content (10–20 vol.%) compared with those reported in the literature. [Copyright &y& Elsevier]

The quality of diamond wheels for edge grinding flat glass was increased by decreasing the relative consumption of diamond grinding wheels as a result of increasing the durability of the binder and using diamond powders with optimal coating. New diamond wheels based on a metal binder with volume content of nickel powder 40% and diamond powder with nickel coating 56%, which decrease the relative consumption of diamond by 20 - 30% with the roughness of the worked surface remaining unchanged are recommended for commercial use. [ABSTRACT FROM AUTHOR]

In the present study, the impact of copper substrate grain size on the structure of the succeeding electrodeposited nickel film and its consequent corrosion resistance in 3.5% NaCl medium were evaluated before and after functionalization with stearic acid. Nickel layers were electrodeposited on two different copper sheets with average grain size of 12 and 25 µm, followed by deposition of stearic acid film through self-assembly. X-ray diffraction analysis of the electrodeposited nickel films revealed that the deposition of nickel film on the Cu substrate with small (12 µm) and large (25 µm) grains is predominantly governed by growth in the (220) and (111) planes, respectively. Both electrodeposited films initially exhibited a hydrophilic nature, with water-contact angles of 56° and <10°, respectively. After functionalization with stearic acid, superhydrophobic films with contact angles of ~150° were obtained on both samples. In a 3.5% NaCl medium, the corrosion resistance of the nickel layer electrodeposited on the copper substrate with 25 µm grains was three times greater than that deposited on the copper substrate with 12 µm grains. After functionalization, the corrosion resistance of both films was greatly improved in both short and long immersion times in 3.5% NaCl medium. [ABSTRACT FROM AUTHOR]