Search Results (381)

The aim of the present study is to investigate the influence of Nickel–Hexagonal Boron Nitride (Ni-hBN) nanocomposite coatings, deposited using the pulse reverse current electrodeposition technique. This experimental study focuses on assessing the tribological and corrosion properties of the produced coatings on the SS304 substrate. The microhardness of the as-deposited (AD) sample and heat-treated (HT) sample were 49% and 83.8% higher compared to the control sample. The HT sample exhibited a grain size which was approximately 9.7% larger than the AD sample owing to the expansion–contraction mechanism of grains during heat treatment and sudden quenching. Surface roughness reduced after coating, where the Ni-hBN-coated sample measured a roughness of 0.43 µm compared to 0.48 µm for the bare surface. The average coefficient of friction for the AD sample was 42.4% lower than the bare surface owing to the self-lubricating properties of nano hBN. In particular, the corrosion rate of the AD sample was found to be 0.062 mm/year, which was lower than values reported in other studies. As such, findings from the present study can be particularly beneficial for applications in the automotive and aerospace industries, where enhanced wear resistance, reduced friction, and superior corrosion protection are critical for components such as engine parts, gears, bearings and shafts. Full article

The development of metallic coatings as Ni-Co alloys, with particular emphasis on their homogeneity, processability, and sustainability, is of the utmost significance. To address these challenges, the utilization of phenylsalicylimines (PSIs) as additives within deep eutectic solvents (DES) was investigated, assessing their influence on the electrodeposition process of these metals at an intermediate temperature of 60 °C, while circumventing aqueous reaction conditions. The findings demonstrated that the incorporation of PSIs markedly enhances coating uniformity, resulting in an optimal cobalt content of 37% and an average thickness of 24 µm. Electrochemical evaluations revealed improvements in charge and mass transfer, thereby optimizing process efficiency. Moreover, computational studies confirmed that PSIs form stable complexes with Co (II), modulating the electrochemical characteristics of the system through the introduction of the diethylamino electron-donating group, which significantly stabilizes the coordinated forms with both components of the DES. Additionally, the coatings displayed exceptional corrosion resistance, with a rate of 0.781 µm per year, and achieved an optimal hardness of 38 N HRC, conforming to ASTM B994 standards. This research contributes to the development of electroplating bath designs for metallic coating deposition and lays the groundwork for the advancement of sophisticated technologies in functional coatings that augment corrosion resistance and mechanical properties. Full article

In this work, we have used both plain titania nanotubes, TNTs, and their reduced black analogues, bTNTs, that bear metallic conductivity (prepared by solid state reaction of TNTs with CaH₂ at 500 °C for 2 h), as catalyst supports for the oxygen evolution reaction (OER). Ir was subsequently been deposited on them by the galvanic replacement of electrodeposited Ni by Ir(IV) chloro-complexes; this was followed by Ir electrochemical anodization to IrO₂. By carrying out the preparation of the TNTs in either two or one anodization steps, we were able to produce close-packed or open-structure nanotubes, respectively. In the former case, larger than 100 nm Ir aggregates were finally formed on the top face of the nanotubes (leading to partial or full surface coverage); in the latter case, Ir nanoparticles smaller than 100 nm were obtained, with some of them located inside the pores of the nanotubes, which retained a porous surface structure. The electrocatalytic activity of IrO₂ supported on open-structure bTNTs towards OER is superior to that supported on close-packed bTNTs and TNTs, and its performance is comparable or better than that of similar electrodes reported in the literature (overpotential of η = 240 mV at 10 mA cm⁻²; current density of 70 mA cm⁻² and mass specific current density of 258 mA mg_Ir⁻¹ at η = 300 mV). Furthermore, these electrodes demonstrated good medium-term stability, maintaining stable performance for 72 h at 10 mA cm⁻² in acid. Full article

This work explored an electrochemical approach for synthesizing lanthanum-modified nickel oxide (NiO_x:La) as a hole transport layer (HTL) in inverted perovskite solar cells (IPSCs). By varying the La³⁺ concentration, the chemical, charge transport, structural, and morphological properties of the NiO_x:La film and the HTL/PVK interface were evaluated to enhance photovoltaic performance. X-ray photoelectron spectroscopy (XPS) confirmed La³⁺ incorporation, a higher Ni³⁺/Ni³⁺ ratio, and a valence band shift, improving p-type conductivity. Electrochemical impedance spectroscopy and Mott–Schottky analyses indicated that NiO_x:La 0.5% exhibited the lowest resistance and the highest carrier density, correlating with higher recombination resistance. The NiO_x:La 0.5% based cell achieved a PCE of 20.08%. XRD and SEM confirmed no significant changes in PVK structure, while photoluminescence extinction demonstrated improved charge extraction. After 50 days, this cell retained 80% of its initial PCE, whereas a pristine NiO_x device retained 75%. Hyperspectral imaging revealed lower optical absorption loss and better homogeneity. These results highlight NiO_x:La as a promising HTL for efficient and stable IPSCs. Full article

Electro-oxidation of urea (UOR) in alkaline medium is one of the most effective alternative ways of producing green hydrogen, as the oxidation potential in UOR is less and thermodynamically more favorable than conventional water oxidation. The development of cost-effective materials in catalyzing UOR is recently seeking more attention in the research hotspot. Suitably modifying the Ni-based catalysts towards active site creation and preventing surface passivation is much important in this context, following which we reported the synthesis of Ni₃S₂ (NS) supported with CuCo (CC) bimetallic (NSCC). A simple hydrothermal route for NS synthesis and the electrodeposition method for CuCo (CC) deposition is adapted in a self-supported manner. The NS and CC catalysts exhibited sheet-like morphology, as confirmed by SEM and TEM analysis. The bimetallic CC deposition prevented the surface passivation of nickel sulfide (NS) over oxygen evolution reaction (OER) and improved the charge-transfer kinetics. The NSCC catalyst catalyzed UOR in an alkaline medium, which required a lower potential of 1.335 V vs. RHE to attain the current density of 10 mAcm⁻², with a lower Tafel slope value of 131 mVdec⁻¹. In addition, a two-electrode cell setup is constructed with an operating cell voltage of 1.512 V for delivering 10 mAcm⁻² current density. This study illustrates the new strategy of designing heterostructure catalysts for electrocatalytic UOR. Full article

Ni–P–WC–BN(h) nanocomposite coatings were fabricated on 20CrMnTi substrates using ultrasonic-assisted pulsed electrodeposition. 20CrMnTi is a low-carbon steel that is commonly used in the manufacturing gears and shaft components. To enhance the wear resistance and extend the service life of such mechanical parts, ultrasonic-assisted pulsed electrodeposition was employed as an effective surface modification technique. The microhardness, phase structure, surface morphology, and wear behavior of the coating were also characterized. An orthogonal experimental design was employed to examine the effects of current density, bath temperature, ultrasonic power, and pulse duty cycle on the microhardness and wear behavior of the coatings, aiming to optimize the deposition parameters. The optimal process combination was identified as a current density of 3 A·dm⁻², a bath temperature of 55 °C, an ultrasonic power of 210 W, and a duty cycle of 0.7. Under these conditions, the coatings exhibited enhanced hardness and wear resistance. Based on the optimized parameters, additional tribological tests were conducted under various operating conditions to further evaluate wear performance. The results showed that the dominant wear mechanisms were chemical wear and adhesive wear. This study offers new insights into the fabrication of high-performance nanocomposite coatings and expands the application scope of ultrasonic-assisted pulsed electrodeposition in multiphase composite systems. Full article

Efficient and low-cost electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media are essential for sustainable hydrogen production. In this study, Ni electrocatalysts were deposited on pencil graphite using a simple one-step pulsed current electrodeposition method, from both acidic Watts and alkaline citrate baths. The influence of bath type and electrodeposition parameters—current density and temperature—on catalyst morphology and performance for HER was systematically investigated by scanning electron microscopy and electrochemical methods. Linear sweep voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy (EIS) were used to evaluate the electrocatalytic activity, stability, and HER mechanism. The best catalytic performance was achieved for the Ni electrocatalyst deposited from the citrate bath at 50 mA cm⁻² and 40 °C, showing an exchange current density of 0.93 mA cm⁻², a Tafel slope of −208 mV dec⁻¹, and overpotentials of −210 mV and −386 mV at 10 and 100 mA cm⁻², respectively, in 1 M KOH solution. Chronopotentiometry confirmed improved stability and an overpotential reduction of approximately 92 mV as compared to pure Ni, while EIS revealed the lowest charge transfer resistance. It was shown that the electrocatalysts deposited from the citrate bath outperform those from the Watts bath, and electrodeposition at 40 °C is optimal for achieving the highest electrocatalytic activity for HER. Full article

This study focused on investigations of FeCo and FeNi nanowires prepared by template-assisted electrodeposition in polycarbonate membranes. Nanowires with a diameter of 100 nm and length of 6 µm were grown at different cathodic potentials and electrolyte compositions. Scanning electron microscopy images revealed densely packed arrays of continuous nanowires with smooth surfaces without visible porosity, regardless of the applied potential. Chemical analysis of nanowires pointed out weak sensitivity of chemical composition on the electrodeposition potential in the case of FeCo nanowires, in contrast to FeNi nanowires, where the increase of the cathodic potential resulted in higher Ni content. X-ray diffraction studies showed polycrystalline structure for all samples indicating B2 phase (Pm-3m) with isotropic growth of FeCo nanowires and FeNi₃ phase with a preferential growth along [111] direction in the case of FeNi nanowires. The peak broadening suggests a fine crystalline structure for both FeCo and FeNi materials with average crystallite sizes below 20 nm. Magnetic studies indicated an easy axis of magnetization parallel to the nanowire axis for all FeCo nanowires and potential-dependent anisotropy for FeNi nanowires. The present studies thus suggested the feasibility of producing segmented nanowires based on FeNi alloys, while poor chemical sensitivity to the applied potential was observed for the FeCo system. Full article

The novel pyridine oxime-based complexing agents 2-pyridinecarboxaldehyde oxime, 2-acetylpyridine ketoxime and 2-pyridine amidoxime were synthesized for alkaline Zn-Ni alloy electrodeposition, outperforming conventional citrate/TEPA systems in corrosion resistance and microstructural control. The N,O-bidentate chelation mechanism governs metal ion reduction kinetics via diffusion-limited pathways, enabling γ-phase Ni₅Zn₂₁ intermetallic formation and nanocrystalline refinement. Electrochemical and microstructural analyses demonstrate suppressed random nucleation and hydrogen evolution side reactions, leading to enhanced charge transfer resistance and reduced corrosion current density. Notably, 2-pyridine amidoxime achieves ultrasmooth surfaces through defect-free nanocluster growth, while 2-pyridinecarboxaldehyde oxime maximizes γ-phase crystallinity. The synergy between grain boundary density and surface integrity establishes a dual protection mechanism combining barrier layer formation and active dissolution suppression. This work advances microstructure engineering via coordination chemistry, offering a breakthrough over traditional zincate electroplating for high-performance anti-corrosion coatings. Full article

A new brazing process for thin-walled stainless steel was proposed by combining green and efficient Ni-Cr-P electrodeposition with brazing technology. Novel information was attained by analyzing the electrodeposited Ni-Cr-P interlayers and the brazed joints and characterizing them using a combination of advanced techniques. The incorporation mechanisms of impurities (i.e., oxygen and carbon) in the Ni-Cr-P interlayers electrodeposited from a Cr(III)–glycine solution were revealed. The oxygen mainly came from the Cr(III)–hydroxy complexes formed by the hydrolysis and olation between Cr(III) complexes and OH⁻ ions near the cathode. Glycine did not directly participate in the cathode reactions but decomposed on the anode surface. These byproducts (carbonyl compounds) were directly incorporated into the interlayers in a molecular pattern, forming a weak link to the metallic chromium. Brazing test results showed that a certain amount of Cr₂O₃ powder, formed by the decomposition of chromium hydroxides in the interlayers under high-temperature catalysis, would cause the degradation of the brazed joints. Using the step-wise brazing method, the brazing sheets were first annealed to eliminate the impurities by utilizing the strong reducing effect of hydrogen and the weak link characteristics between carbonyl compounds and metallic chromium atoms. An excellent joint with a shear strength of 63.0 MPa was obtained by subsequent brazing. The microstructural analysis showed that the brazed seam was mainly composed of a Ni-Fe-Cr solid solution, the Ni₃P eutectic phase, and small quantities of the Ni₅P₂ phase scattered in the Ni₃P eutectic phase. Fracture mode observations showed that the cracks extended along the interface between the brittle P-containing phase and the primary phase, resulting in fracture. Full article

This study aims to develop high-performance nickel selenide (NiSe) electrodes via a controlled electrodeposition approach, optimizing the number of deposition cycles to enhance electrochemical energy storage capabilities. Nickel selenide electrodes were synthesized at varying electrodeposition cycles (2CY–5CY) and systematically evaluated in both three-electrode and asymmetric supercapacitor (ASC) configurations to determine the optimal cycle for superior performance. Among all, the NiSe-3CY electrode demonstrated the best electrochemical characteristics, delivering a high specific capacitance of 507.42 F/g in a three-electrode setup. It also achieved an energy density of 22.89 Wh/kg and a power density of 584.61 W/kg, outperforming its 2CY, 4CY, and 5CY counterparts. Notably, the 3CY electrode exhibited the lowest series resistance (1.59 Ω), indicative of enhanced charge transport and minimal internal resistance. When integrated into an ASC device (NiSe-3CY//activated carbon), it maintained a specific capacitance of 18.78 F/g, with an energy density of 8.45 Wh/kg and power density of 385.03 W/kg. Furthermore, the device exhibited impressive areal and volumetric capacitances of 351 mF/cm² and 1.09 F/cm³, respectively, with a corresponding volumetric energy density of 0.49 mWh/cm³. Long-term cycling tests revealed excellent durability, retaining 91% of its initial capacity after 10k cycles with a high Coulombic efficiency of 99%. These results confirm that the 3CY electrode is a highly promising candidate for next-generation energy storage systems, offering a balanced combination of high capacitance, energy density, and cycling stability. Full article

Nickel–titanium carbide (Ni-TiC) coatings were synthesized on Q235 steel via double-pulse electrodeposition to enhance surface properties. The influence of TiC concentration on surface morphology, microstructure, and performance was systematically studied using SEM, TEM, XRD, microhardness testing, wear analysis, and electrochemical methods. At low TiC concentrations (2–4 g/L), the coatings exhibited typical cell-like morphology. At 8 g/L, the coating showed a dense structure, refined grains, and broad Ni diffraction peaks. TEM analysis revealed nickel and TiC grain sizes of 97.82 nm and 34.75 nm, respectively. The plating rate remained stable (~36.94 mg·cm⁻²·h⁻¹), while surface roughness increased with TiC content. The 8 g/L TiC coating achieved the highest microhardness (743.13 HV), lowest wear loss (5.43%), and superior corrosion resistance, with a self-corrosion current density of 5.27 × 10⁻⁶ A·cm⁻² and polarization resistance of 7705.62 Ω·cm². These enhancements are attributed to uniform TiC dispersion and grain boundary pinning. Thus, 8 g/L TiC is optimal for fabricating Ni-TiC coatings with improved mechanical and electrochemical performance. This work demonstrates a practical strategy for developing high-performance Ni-based composite coatings via double-pulse electrodeposition. Full article

Electrodeposited composite coatings are widely studied for their potential to improve surface properties such as wear resistance and friction reduction. This study investigates the effect of electrodeposition parameters on the structure, morphology, and tribological performance of three coatings: pure nickel (Ni), Ni–graphite (Ni-G), and Ni–MoS₂ (Ni-MoS₂). Three deposition conditions were selected based on a review of key electrochemical parameters commonly used in the literature. The coatings were analyzed in terms of morphological characteristics, friction and wear resistance. The findings reveal that higher current densities led to increased friction and wear in Ni coatings, while lower pH values promoted finer crystallite sizes and improved tribological behavior. Ni-G coatings exhibited larger cluster formations with reduced friction and wear, especially at low pH, whereas Ni-MoS₂ coatings developed a stable cauliflower-like morphology at pH 2, but showed reduced adhesion and structural integrity at higher pH levels. Scratch resistance tests performed under optimal deposition conditions showed that Ni-G coatings provided the highest resistance to mechanical damage, while Ni-MoS₂ coatings were more susceptible to microcracking and adhesion failure. These results underscore the importance of optimizing deposition parameters to tailor the microstructure and functional properties of composite coatings for enhanced tribological and mechanical performance. Full article

Tailoring the microstructural heterogeneity of metallic coatings is a promising strategy for enhancing their corrosion resistance; however, its systematic optimization remains underexplored. Here in, we present a one-step, scalable electrodeposition strategy to fabricate Ni coatings with tunable nanocrystalline heterostructures on Cu substrates by varying the current density from 1 mA/cm² to 50 mA/cm². The coating with a current density of 10 mA/cm², featuring a heterogeneous nanograin structure of coexisting small and large grains, exhibited optimal corrosion resistance in 3.5 wt.% NaCl solution, with a low self-corrosion current density of 4.48 µA/cm². Electrochemical impedance spectroscopy (EIS) and molecular dynamics (MD) simulations revealed that the heterostructure dispersed Cl⁻ adsorption sites and promoted passivation. High-resolution transmission electron microscopy (HRTEM) revealed that as the current density increased from 10 mA/cm² to 50 mA/cm², the corrosion product transitioned from a crystalline NiOOH structure to an amorphous structure, which correlated with a reduced corrosion resistance. The heterogeneous microstructure enhances durability, offering a cost-effective and alloy-free alternative for offshore applications. These findings provide a theoretical and experimental basis for designing advanced corrosion-resistant coatings. Full article

Medium-entropy alloys (MEAs) exhibit properties comparable or even superior to high-entropy alloys (HEAs). Due to their very good resistance in thermomechanical conditions and corrosive environments and unique electrical and magnetic properties, medium-entropy alloys are good candidates for coating applications. One of the most economically effective methods of producing metallic coatings is electrodeposition. In this work, the structure of an electrodeposited CoFeNi medium-entropy alloy coating on a copper substrate from a metal chlorides solution (FeCl₂ ∙ 4H₂O + CoCl₂ ∙ 6H₂O + NiCl₂ ∙ 6H₂O) with the addition of boric acid (H₃BO₃) was investigated. The coating was characterized by a nanocrystalline structure identified by transmission electron microscopy examination and X-ray diffraction methods. Based on XRD and TEM, the face-centered cubic (FCC) phase of the CoFeNi MEA coating was identified. The high corrosion resistance of the MEA coating in a 3.5% NaCl environment at 25 °C was confirmed by electrochemical tests. Full article