Search Results (27)

This study investigates the development and sensing profile of synthetic melanin nanoparticle-coated electrodes for the electrochemical detection of heavy metals, including lead (Pb), cadmium (Cd), cobalt (Co), zinc (Zn), nickel (Ni), and iron (Fe). Synthetic melanin films were prepared in situ by the deacetylation of diacetoxy indole (DAI) to dihydroxy indole (DHI), followed by the deposition of DHI monomers onto indium tin oxide (ITO) and glassy carbon electrodes (GCE) using cyclic voltammetry (CV), forming a thin layer of synthetic melanin film. The deposition process was characterized by electrochemical quartz crystal microbalance (EQCM) in combination with linear sweep voltammetry (LSV) and amperometry to determine the mass and thickness of the deposited film. Surface morphology and elemental composition were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). In contrast, Fourier-transform infrared (FTIR) and UV–Vis spectroscopy confirmed the melanin’s chemical structure and its polyphenolic functional groups. Differential pulse voltammetry (DPV) and amperometry were employed to evaluate the melanin films’ electrochemical activity and sensitivity for detecting heavy metal ions. Reproducibility and repeatability were rigorously assessed, showing consistent electrochemical performance across multiple electrodes and trials. A comparative analysis of ITO, GCE, and graphite electrodes was conducted to identify the most suitable substrate for melanin film preparation, focusing on stability, electrochemical response, and metal ion sensing efficiency. Finally, the applicability of melanin-coated electrodes was tested on in-house heavy metal water samples, exploring their potential for practical environmental monitoring of toxic heavy metals. The findings highlight synthetic melanin-coated electrodes as a promising platform for sensitive and reliable detection of iron with a sensitivity of 106 nA/ppm and a limit of quantification as low as 1 ppm. Full article

To address the graphitization of diamond induced by high temperatures during laser cladding of diamond-reinforced composites, this study proposes a laser cladding method utilizing Inconel 718 (IN718) nickel-based alloy as a transition layer which has a lower melting point than the substrate of 45# steel. And then, in order to analyze the detailed characteristics of the samples, scanning electron microscopy (SEM), EDS, Raman spectral analyzer, super-depth-of-field microscope, and friction tests were used. Experimental study and the test results demonstrate that the IN718 transition layer enhances coating performance through dual mechanisms: firstly, its relatively low melting point (1392 °C) reduces the molten pool’s peak temperature, effectively suppressing thermal-induced graphitization of the diamond; on the other hand, simultaneously it acts as a diffusion barrier to inhibit Fe migration from the substrate and weaken Fe–C interfacial catalytic reactions. Microstructural analysis reveals improved diamond encapsulation and reduced interfacial sintering defects in coatings with the transition layer. Tribological tests confirm that samples with the transition layer L exhibit lower friction coefficients and significantly enhanced wear resistance compared to those without. This study elucidates the synergistic mechanism of the transition layer in thermal management optimization and interfacial reaction suppression, providing an innovative solution to overcome the high-temperature damage bottleneck in laser-clad diamond tools. 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

Aluminum solid-state batteries are emerging as one of the most promising energy storage systems, offering advantages such as low cost and high safety. This study adopts a safe and cost-effective approach by alloying and doping the all-solid-state aluminum-ion battery to enhance its electrochemical performance. This research further explores the electrochemical impacts of these modifications on the performance of solid-state aluminum batteries. In this experiment, aluminum-based anodes were deposited onto nickel foil using the thermal evaporation (TE) method. At the same time, the graphite film (GF) cathode material was enriched with sodium (GFN) through a solution-based process. The system was combined with magnesium silicate solid electrolytes to investigate the all-solid-state aluminum-carbon battery′s structural characteristics and charge–discharge mechanisms. The experimental results demonstrate that the aluminum-coated electrode alloying effects and the graphite film modification significantly improve battery performance. The system achieved a maximum specific capacity of approximately 700 mAh g⁻¹, with a cycle life exceeding 100 cycles. Furthermore, the microstructural characteristics and phase structure of the aluminum evaporation film were confirmed. Analysis of ion transport pathways during the charge–discharge cycles of the all-solid-state aluminum-carbon battery revealed that both aluminum and magnesium ions play critical roles in the electrode processes. Full article

The search for cost-effective and scalable electrocatalysts for the hydrogen evolution reaction (HER) remains a critical challenge in advancing sustainable energy technologies. This study presents a novel approach to optimizing nickel-iron (Ni-Fe) alloy coatings on graphite (G) electrodes through a strategic combination of composition tuning, nickel modification, and various electrochemical optimizations. Unlike conventional studies, which primarily focus on static alloy compositions, this work systematically investigates the impact of dynamic nickel modification durations on the catalytic performance and conductivity of Ni-Fe alloys. By addressing the conductivity limitations caused by iron oxidation, the study demonstrates the enhanced HER kinetics achieved with a Ni-modified G/Ni_%95Fe_%5-Ni(60s) electrode. Electrochemical and structural analyses reveal the synergistic effects of nickel modifications on improving active site accessibility, reducing overpotential, and increasing hydrogen production efficiency. This work introduces a scalable methodology for tailoring Ni-Fe catalysts, offering significant advancements in the development of robust, cost-effective electrocatalysts for industrial-scale hydrogen production. Full article

Aluminum and its alloys are widely used in the busbar structures of electrolytic aluminum production. However, they are prone to corrosion and wear damage during use, leading to a decline in current-transmission efficiency and potentially causing safety issues. To repair damaged aluminum busbars, this paper explores the feasibility of using cold spraying technology for surface restoration. Using 6063 aluminum alloy as the substrate, AlZn/nickel-plated graphite composite coatings were applied through cold spraying. The effects of different nickel-plated graphite contents on the microstructure, mechanical properties, and corrosion resistance of the coatings were studied. Annealing treatments (200 °C, 300 °C, 400 °C) were further used to improve the coating’s density and performance. The results show that with an increase in the nickel-plated graphite content, the porosity of the coating gradually increases, while the coating’s density and bond strength improve. Additionally, the annealing treatment significantly enhanced the uniformity and hardness of the coating. Moreover, the cold-sprayed coatings exhibited excellent corrosion resistance, especially in the annealed coatings, which showed superior microstructural stability and lower corrosion current density. This study provides a new technological approach for the repair of aluminum busbars and offers an in-depth discussion on the application of cold spraying technology in the surface restoration of aluminum-based composite materials. Full article

In recent years, laser cladding technology has been widely used in surface modification of titanium alloys. To improve the wear resistance of titanium alloys, ceramic-reinforced nickel-based composite coatings were prepared on a TC4 alloy substrateusing coaxial powder feeding laser cladding technology. Ti (C, N) ceramic was synthesized in situ by laser cladding by adding different contents (10%, 20%, 30%, and 40%) of TiN, pure Ti powder, graphite, and In625 powder. Thisestudy showed that small TiN particles were decomposed and directly formed the Ti (C, N) phase, while large TiN particles were not completely decomposed. The in situ synthetic TiC_xN_1−x phase was formed around the large TiN particles. With the increase in the proportion of powder addition, the wear volume of the coating shows a decreasing trend, and the wear resistance of the surface coating is improving. The friction coefficient of the sample with 40% TiN, pure Ti powder, and graphite powder is 0.829 times that of the substrate. The wear volume is 0.145 times that of the substrate. The reason for this is that with the increase in TiN, Ti, and graphite in the powder, there are more ceramic phases in the cladding layer, and the hard phases such as TiC, Ti(C, N) and Ti2Ni play the role in the structure of the “backbone”, inhibit the damage caused by micro-cutting, and impede the movement of the tearing point of incision, so that the coating has a higher abrasion resistance. Full article

To reduce the metallurgical defects that are prone to occur in the preparation of nickel-based self-lubricating coatings, a method of process co-optimization for magneto-thermal-assisted laser cladding of nickel-based self-lubricating coatings is proposed in this paper. The laser energy density, preheating temperature, and electromagnetic intensity are selected as input factors; the prediction models of coating dilution rate, porosity and microhardness are established by the CCD test method; the interactive effects of the magnetic-thermal-assisted cladding process on the coating response are analyzed, and the optimal process parameter combinations are obtained by using the optimization method of MOPSO-AE-TOPSIS. Finally, the coatings under the parameters are successfully prepared. The results show that the optimal process parameter combinations obtained are laser energy density of 56.8 J/mm², preheating temperature of 350 °C, electromagnetic intensity of 49.1 mT, and the error of the experimental results with this parameter is less than 3% from the algorithm optimization results. When the microstructure of unassisted and magneto-thermal-assisted fields are analyzed by comparison, it is found that the tissues are more homogeneous and finer, and the distribution of graphite is more homogeneous, which proves the effectiveness of the optimization method. Full article

One of the most promising and heavily researched energy storage systems due to their high energy density, rate capability and extended cycle life are lithium-ion batteries. Their performance and efficiency are nonetheless strongly dependent on their constituent materials and design, including the current collectors. One attractive approach in this respect is the use of metal foams as an alternative to the conventional current collectors. This concept is therefore intended to increase the current collectors’ specific surface area and therefore load more active material by nominal area while keeping the cell architectures simple and less costly. In the present work, nickel is chosen as a model system for a proof of concept of a novel manufacturing method for nickel foams using a combination of 3D printing, coating and electroplating. The purpose is to create geometrically well-defined hollow structures with high porosity and specific surface area density that can rival and partially outperform the commercially available nickel foams. To this end, a 3D printer is used to create geometrically flexible and well-defined open-pored disks of HIPS (high-impact polystyrene), which are then spray coated with a graphite-based conducting layer and subsequently electroplated with a 5–30 µm thin layer of nickel from an additive-free nickel sulfamate electrolyte. Following the coating process, the support structure is dissolved with toluene, resulting in structures with a unique combination of porosity in the range of 92.3–99.1% and an ultra-high specific surface area density up to 46 m²/kg. Morphological characterization by light and scanning electron microscopy has proven that the temporarily required polymer substrate can be mildly and completely removed by the suggested room temperature dissolution process. Full article

The study evaluates the mechanical and wear properties of LM26 alloy and its hybrid composites with silicon carbide (SiC) and nickel-coated graphite (Ni-Gr). LM26 aluminum alloy is generally known for its high strength, wear, and corrosion resistance compared to similar materials such as zinc and magnesium. The effect of Ni-Gr was studied, with 2 wt.% was found to provide the best mechanical properties. LM26 composites reinforced with varying percentages of SiC (0 to 30 wt.%) showed the best properties at 20 wt.% reinforcement after fabrication using a bottom pouring type stir casting setup (Two step feeding method). Evaluation of five hybrid LM26 composites through tensile strength, elongation, hardness, impact, porosity, and thermal studies showed that the LM26/2 wt.% Ni-Gr/20 wt.% SiC configuration showed the best filler composition for improved strength. Sliding wear evaluation using experimental and Taguchi analysis was performed at different configurations to identify the best wear resistance. Microstructure studies showed the presence of Ni-Gr particles forming coatings and temperature playing a significant role in the progression of the wear rate. Furthermore, the hybrid composite with 20% SiC and 2% Ni-Gr reinforcement showed the best wear resistance. Full article

The synthesis and characterization of fibrous materials with a hierarchical structure are of great importance for materials sciences. Among this class of materials, microfibers of different natures coated with carbon nanofibers attract special interest. Such coating modifies the surface of microfibers, makes it rougher, and thus strengthens its interaction with matrices being reinforced by the addition of these microfibers. In the present work, a series of hierarchical materials based on carbon microfibers, basalt microfibers, and fiberglass cloth coated with up to 50 wt% of carbon nanofibers was synthesized via the catalytic chemical vapor deposition technique. The initial items were impregnated with an aqueous solution of nickel nitrate and reduced in a hydrogen flow. Then, the catalytic chemical vapor deposition process using C₂H₄ or C₂H₄Cl₂ as a carbon source was carried out. A simple and cost-effective technique for the preparation of the samples of hierarchical materials for transmission electron microscopy examination was developed and applied for the first time. The proposed method of sample preparation for sequential TEM visualization implies an ultrasonic treatment of up to four samples simultaneously under the same conditions by using a special sample holder. As was found, the relative strength of carbon nanofibers coating the surface of microfibers decreases in the order of CNF/CMF > CNF/BMF > CNF/FGC. Two effects of the ultrasonic action on the carbon coating were revealed. First, strongly bonded carbon nanofibers undergo significant breakage. Such behavior is typical for carbon and basalt microfibers. Secondly, carbon nanofibers can be completely detached from the microfiber surface, as was observed in the case of fiberglass cloth. In the case of CNF/CMF material, the graphitized surface of carbon microfiber is coherent with the structure of carbon nanofiber fragments grown on it, which explains the highest adhesion strength of the carbon nanolayer coated on carbon microfibers. Full article

The development and production of thin-film coatings having very low friction is an urgent problem of materials science. One of the most promising solutions is the fabrication of special nanocomposites containing transition-metal dichalcogenides and various carbon-based nanophases. This study aims to explore the influence of graphite-like carbon (g-C) and Ni interface layers on the tribological properties of thin WS₂ films. Nanocrystalline WS₂ films were created by reactive pulsed laser deposition (PLD) in H₂S at 500 °C. Between the two WS₂ nanolayers, g-C and Ni nanofilms were fabricated by PLD at 700 and 22 °C, respectively. Tribotesting was carried out in a nitrogen-enriched atmosphere by the reciprocal sliding of a steel counterbody under a relatively low load of 1 N. For single-layer WS₂ films, the friction coefficient was ~0.04. The application of g-C films did not noticeably improve the tribological properties of WS₂-based films. However, the application of thin films of g-C and Ni reduced the friction coefficient to 0.013, thus, approaching superlubricity. The island morphology of the Ni nanofilm ensured WS₂ retention and altered the contact area between the counterbody and the film surface. The catalytic properties of nickel facilitated the introduction of S and H atoms into g-C. The sliding of WS₂ nanoplates against an amorphous g-C(S, H) nanolayer caused a lower coefficient of friction than the relative sliding of WS₂ nanoplates. The detected behavior of the prepared thin films suggests a new strategy of designing antifriction coatings for practical applications and highlights the ample opportunities of laser techniques in the formation of promising thin-film coatings. Full article

Titanium alloys are widely used in high-tech fields, while its disadvantages such as low hardness, high coefficient of friction and poor wear resistance have restricted its applications. This study focuses on improving the friction and wear resistance of Ti-6Al-4V titanium alloys by means of laser surface alloying with Ni-coated graphite (G@Ni). The results suggest that Ni acts as a protective layer to hinder the direct contact and reaction of C and Ti in the molten pool. A part of graphite is unmelted and finally remains to form a self-lubricating wear-resistant composite coating with a compact structure. The average hardness of the coating is approximately four times that of the substrate owing to the TiC hard phase and compact microstructures as the reinforcing phase. The residual graphite in the coating plays a friction-reduction role during the wear test. The wear resistance is increased to 8.53 times that of the substrate according to wear mass loss. This study can effectively enhance the performance and expand the application of the titanium alloys by improving the wear resistance and reducing the friction. Full article

Nickel-coated graphite (Ni/C) powder has many applications in diverse areas such as paint, print ink, adhesive, conductive rubber, and so on. To increase its stability in harsh environmental conditions, the electroless plating of silver film on Ni/C via ascorbic acid was studied. A silver layer with a thickness of 2.5 μm was successfully plated on Ni/C powder’s surface with an Ag loading of 44.35 wt.%. Silica gel blended with the Ag/Ni/C powder exhibited much higher conductivity under aging conditions of 85 °C and 85% RH for 1000 h than that with pristine Ni/C powder. Further tests showed that the conductivity of Ag/Ni/C powder remained almost unchanged even in an extremely humid and hot condition for 1000 h. Aging tests were carried out for Ag/Ni/C and Ni/C powders under long-term humid and hot conditions (85 °C, 85% RH), in which Ag/Ni/C samples showed much better electromagnetic shielding performance. Due to the excellent properties and reasonable price, the potential applications of Ag/Ni/C in conductive glue and electromagnetic shielding glue could be expected. Full article

This paper describes the use of Supersonic Laser Deposition (SLD) to manufacture nickel/graphite composite coatings on titanium and aluminium substrates. Laser heating is critical for depositing coatings containing up to 13.3 vol% graphite. For a given feedstock composition, the resulting graphite content and average size of the graphite particles retained in the coating increases with laser power, until substrate melting occurs. The effect of the powder type, feedstock composition, and process conditions on coating structure is characterized. The friction and wear behaviour of selected coating compositions is examined. Nickel coatings containing 13.3 vol% graphite demonstrated self-lubricating behaviour with a stable coefficient of friction below 0.14 in pin-on-disc testing. Full article