Search Results (262)

Ultra-fine-grained bainitic (UFGB) steels offer excellent mechanical properties, which can be further improved by applying diamond-like carbon (DLC) coatings. However, poor adhesion between the coating and substrate remains a key limitation. Since the steel’s microstructure degrades at high temperatures, enhancing adhesion without heating the substrate is essential. This study investigates surface hardening combined with simultaneous nitrogen and hydrogen doping during the Radio Frequency Chemical Vapor Deposition (RFCVD) process to improve coating performance. Varying gas compositions were tested to assess their effects on coating properties. Nitrogen incorporation decreased hardness from 12 GPa to 9 GPa but improved adhesion, while hydrogen limited damage after coating failure. Optimizing the gas mixture led to enhanced adhesion and wear resistance. Raman and X-ray photoelectron spectroscopy (XPS) analyses confirmed that the optimized coatings had the highest sp³ bond content and elevated nitrogen levels. While both hardness and adhesion contributed to wear resistance, no direct link to coating thickness was found. Overall, co-doping with nitrogen and hydrogen is an effective approach to improve adhesion and wear resistance without requiring high processing temperatures or complex equipment. Full article

This research investigates a novel hybrid E-glass fiber coated with a thin amorphous carbon (coke) layer, referred to as GF@C, designed to enhance the affinity of fiber with a polymer matrix. Acrylonitrile butadiene styrene (ABS), an engineering thermoplastic, was selected as the matrix to form the composite. The carbon coating was produced by pyrolyzing a lubricant oil (Lo) layer applied to the glass fiber strands. To promote the formation of graphite crystallites during carbonization, a small amount (x wt.% of Lo) of coronene (Cor) was added to Lo as a dopant. The resulting doped fibers, denoted GF@C_Lo-Cor(x%), were embedded in ABS at 70 wt.%, leading to significant improvements in mechanical properties. At the optimal doping level (x = 5), the composite achieved a Young’s modulus of 1.02 GPa and a tensile strength of 6.96 MPa, substantially higher than the 0.4 GPa and 3.81 MPa observed for the composite with the pristine GF. This enhancement is attributed to a distribution of graphite crystallites and their graphitization extent in the carbon coating, which improves interfacial bonding and increases chain entanglement. Additionally, GF@C_Lo-Cor(x%)–ABS composites (x = 0 and 5) exhibit significantly higher dielectric constant–temperature profiles than GF–ABS, attributed to the formation of diverse chain adsorption states on the C-coating. Full article

Utilizing renewable energy for green hydrogen production via electrolyzed seawater is a promising technology for the future. However, undesired chlorine evolution and the corrosive nature of seawater are crucial challenges for direct seawater splitting technology. In this work, heterojunctions of CoS₂/FeS₂ encapsulated in N-doped carbon nanocubes (denoted as CoS₂/FeS₂@NC) were designed by proposing the synchronous pyrolysis and vulcanization of polydopamine-coated coordination polymers. Such a synthetic strategy was demonstrated to be effective in increasing the favorable exposure of active sites, moderately regulating electronic structure, and remarkably facilitating charge transfer due to the controllable generation of unique core–shell structures with suitable carbon shells, leading to the excellent bifunctional electrocatalytic performance and enhanced stability of electrocatalysts. As a result, CoS₂/FeS₂@NC can be revealed as a superior water splitting catalyst, possessing a small voltage of 1.75 V and requiring 100.0 mA cm⁻² in 1 M KOH alkaline solution and 1.80 V for alkaline seawater media, with satisfactory long-term stability. This work presents fresh strategies for designing core–shell heterostructures and developing green technology for hydrogen production. Full article

Diamond-like carbon (DLC) coatings have emerged as a focal point in advanced carbon materials research due to exceptional tribological properties, including ultralow friction coefficient, exceptional wear resistance, ultrahigh hardness, and chemical inertness. Deposition of DLC coatings on metal components represents an innovative solution to enhance wear resistance in engineering applications. However, suboptimal adhesion strength between coatings and substrates, coupled with inherent material limitations, critically compromises the tribological performance. This review systematically examines recent advances in improving the wear resistance of DLC-coated metal components. First, the fundamental wear mechanisms governing both metallic substrates and DLC coatings under service conditions are elucidated. Next, three pivotal technologies, substrate material treatment/strengthening, coating structure design, and elemental doping, all demonstrating significant efficacy in wear resistance enhancement, are critically analyzed. Furthermore, a comparative assessment of these techniques reveals the synergistic potential in hybrid approaches. Finally, a concise summary of the outlook is presented. Full article

MXenes have emerged as promising candidates for energy storage and catalyst design. Through detailed density functional theory (DFT) calculations, we designed a series of new 2D composite MXene-based nanomaterials by covering excellent TM₃N₂ MXenes (TM = Nb, Ta, Mo, and W) with graphene or buckled silicene. Our findings demonstrate that this coating can lead to high catalytic activity for hydrogen evolution reactions (HER) in these composite MXene-based systems, with silicene exhibiting superior performance compared to graphene. The relevant carbon and silicon atoms in the coated materials serve as active sites for HER due to complex electron transfer processes. Additionally, doping N or P atoms into graphene/silicene, which have similar atomic radii, but larger electronegativity than C/Si atoms, can further enhance the HER activity of adjacent carbon or silicon atoms, thus endowing the composite systems with higher HER catalytic performance. Coupled with their high stability and metallic conductivity, all these composite systems show great potential as electrocatalysts for HER. These remarkable findings offer new strategies and valuable insights for designing non-precious and highly efficient MXene-based HER electrocatalysts. Full article

The test method for internal stress of titanium-based nitride was optimized via penetration depth and surface roughness. Through the test method, the variations in the mechanical properties due to the ratio of the carbon gradient layer were investigated in terms of internal stress. TiN coatings were deposited on SUS 304 using RF/DC magnetron sputtering, and the penetration depth was adjusted by varying the X-ray power of HR-XRD for test specimens with the same coating thickness of 1 μm. The gradient of diagram for internal stress remained constant regardless of the penetration depth, and this was attributed to the analysis of internal stress focusing on the preferred growth orientation of the coating and excluding the influence of the substrate. In addition, we tested different surface roughness values (0.01 Sa, 0.02 Sa, and 0.03 Sa) to observe the effect on internal stress measurement. The results showed negligible difference in internal stress, confirming that this measurement method is valid for coatings with a surface roughness of 0.03 Sa or less. The test method was applied to analyze the carbon-doped TiZrN coating. TiZrN coatings were deposited on SUS 304, and coating thicknesses of 0.5 μm, 1 μm, and 2 μm were used to control the ratio of the carbon gradient layer. After applying the carbon paste for carbon doping, the TiZrN coating was irradiated with a pulsed laser. The compressive internal stress increased from −1263 MPa to −1687 MPa at a coating thickness of 0.5 μm, where the ratio of the carbon gradient layer was the highest. It was confirmed that the increase in internal stress with the ratio of the carbon gradient layer improved the mechanical properties of the carbon-doped TiZrN coating by laser carburization. Full article

The contamination of aquatic ecosystems by the micropollutants in wastewater discharges is currently a critical issue. Therefore, the development of novel treatment processes and materials is essential to ensure the availability of safe water. The present study aims to develop a photocatalytic material composed of silver nanoparticles (Ag-NPs)-doped TiO₂ supported on a Pyrex^® plate (TiO₂@Ag-NPs) exhibiting catalytic activity under visible irradiation (λ > 400 nm). The effects of Ag-NPs doping on the TiO₂ matrix, the resistance of the coating at the catalyst/substrate interface, and the photocatalytic degradation efficiency of the photocatalyst for a micropollutant (diuron) of the pesticide family were studied. The photocatalyst was characterised using X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectrophotometry, and scratch tests. The solution concentrations were monitored using high-performance liquid chromatography and total organic carbon analyses. A 32% diuron removal was achieved using photocatalytic TiO₂@Ag-NPs under visible irradiation, whereas undoped TiO₂ showed no activity. Furthermore, the effects of the nanoparticle growth mode on the photocatalytic activity of TiO₂@Ag-NPs were explored. The presence of a TiO₂ sublayer ensured the adhesion of the coating and promoted the dispersion of nanoparticles within the matrix. It ensured chemical continuity (TiO₂@Ag-NPs/Pyrex^®), reduced the bandgap, and decreased electron–hole pair recombination. Full article

Silicon-doped tetrahedral amorphous carbon (ta-C:Si) coatings are promising materials for achieving ultralow friction in water-lubricated environments, attributed to the formation of Si(OH)_x-based tribofilms. However, the deposition process via filtered cathodic vacuum arc (FCVA) often introduces large particles into the film, increasing surface roughness and causing accelerated wear during the initial sliding phase, despite the high hardness of the coating. In this study, ball-on-disk tribological tests were performed to investigate the wear behavior of ta-C:Si coatings under water lubrication. Friction coefficients, wear volume, and surface roughness were analyzed over various sliding durations. The Archard wear equation and the plasticity index were used to analyze wear and contact behavior. The friction coefficient decreased from 0.14 to 0.04 within the initial 100 m section, and the surface roughness of ta-C:Si decreased sharply from 0.35 μm to 0.01 μm based on the Rpk parameter during 10 h. Following this period, the plasticity index decreased from an initial value of 1.1 to below 0.6, transitioning to a fully elastic contact stage, marking the onset of steady-state wear after 10 h. These results indicate that the reduction in surface roughness plays a crucial role in stabilizing wear behavior and provide insights into optimizing the long-term performance of ta-C:Si coatings in aqueous environments. Full article

Natural graphite (NG) is abundant and has a high capacity for lithium-ion storage, but its narrow interlayer spacing and poor cyclic stability limit its use in high-performance lithium-ion batteries (LIBs). To address this, a N/S co-doped micro-expanded graphite composite (BFAC@MEG) was prepared by coating micro-expanded graphite (MEG) with N/S-containing amorphous carbon derived from biochemical fulvic acid (BFAC). This enhanced the electrochemical kinetics of lithium ions, improving charge transfer rates and reducing diffusion resistance. GITT results showed a higher Li⁺ diffusion coefficient than MEG and spherical graphite (SG). BFAC@MEG exhibited excellent rate performance, robust storage capacity and remarkable cycling stability. It had a specific capacity of 333 mAh g⁻¹ at 1 C, 205 mAh g⁻¹ at 3 C, and retained 81.57% capacity after 500 cycles. Even at 5 C, BFAC@MEG exhibits a high reversible capacity of 98 mAh g⁻¹ after 200 cycles. After cycling, SEM and XPS analyses revealed a low expansion rate of 15.96% cross-sectional expansion after 300 cycles at 3 C and a stable solid electrolyte interphase (SEI) film rich in LiF and Li₂CO₃. Full article

Non-hydrogenated diamond-like carbon (DLC) films and molybdenum-doped diamond-like carbon (Mo-DLC) films were deposited by direct current magnetron sputtering. The formation was carried out on Si (100) wafers. The influence of molybdenum concentration and deposition temperature on the surface morphology, chemical composition, type of chemical bonds, friction force at nanoscale, and nanohardness of the DLC coatings were investigated by atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and nanoindenter, respectively. The concentration of molybdenum in the films varies from 1.2 at.% to 10.3 at.%. The increase in molybdenum content promotes the graphitization of DLC films, lowering the sp³ site fraction and increasing the oxygen content, which contributes to the reduction in nanohardness (by 21%) of the DLC films. The decrease in the synthesis temperature from 235 °C to 180 °C enhanced the oxygen amount up to 20.4 at.%. The sp³ site fraction and nanohardness of the Mo-DLC films were enhanced with the reduction in the deposition temperature. The film deposited at a substrate temperature of 235 °C exhibited the lowest friction coefficient (CoF) of 0.03, where its molybdenum concentration was 1.2 at.%. The decline in the synthesis temperature increased the CoF of the Mo-DLC films up to seven times. Full article

Copper-doped diamond-like carbon films (Cu-DLC) are effective antibacterial materials and are fabricated using different techniques. By controlling the ratio of the graphite and diamond structures as well as the hydrogen bonds, the biocompatibility, chemical stability, wear resistance, and high hardness of Cu-DLC can be regulated. In this study, three types of Cu-DLC films were deposited on SUS304 substrates using Ar-sputtering with mixed targets comprising different C/Cu ratios. The films’ structures, surface, and antibacterial properties were investigated using electron probe microanalysis, Raman and X-ray photoelectron spectroscopy, atomic force microscopy, and ball-on-disk tests. The Cu concentration in the Cu-DLC films increased with an increase in its content in the target; however, no significant differences were observed in the Raman spectra. The surface composition, roughness, and dynamic friction coefficients were similar across all Cu-DLC films, which displayed smoothness and friction properties similar to those of standard DLC films without Cu. The antibacterial activity (R value) was evaluated as per ISO 22196. Although DLC films exhibited no antibacterial activity (R < 2), all the prepared Cu-DLC films displayed good antibacterial activity (R ≥ 2). The proposed deposition process facilitated Cu-DLC coating, thus promoting its use in the healthcare fields. Full article

A composite (N-rGO@ppy) of N-doped reduced graphene oxide (N-rGO) coated with polypyrrole (ppy) particles was successfully synthesized. The incorporation of N-rGO significantly mitigates the aggregation of ppy synthesized in situ, and the doped N atoms improve the conductivity of graphene oxide (GO), thereby enhancing N-rGO@ppy’s redox properties. Firstly, a glassy carbon electrode (GCE) modified with N-rGO@ppy (N-rGO@ppy/GCE) was used in combination with a bismuth film and square-wave anodic stripping voltammetry (SWASV) for the simultaneous trace analysis of Pb²⁺ and Cd²⁺. N-rGO@ppy/GCE exhibited distinct stripping peaks for Pb²⁺ and Cd²⁺, with a linear range of 1 to 500 μg L⁻¹. The limits of detection (LODs) were found to be 0.080 μg L⁻¹ for Pb²⁺ and 0.029 μg L⁻¹ for Cd²⁺, both of which are significantly below the standards set by the World Health Organization (WHO). Subsequently, the same electrochemical sensing strategy was adapted to a more portable screen-printed electrode (SPE) to accommodate the demand for in situ detection. The performance of N-rGO@ppy/SPE for analyzing Pb²⁺ and Cd²⁺ in actual samples, such as drinking water, milk, and honey, showed results consistent with those obtained from conventional graphite furnace atomic absorption spectrometry (GFAAS). Full article

Silver-white, matte, smooth, and durable deposits of silver-rhenium, with thicknesses ranging from 2.0 to 13.7 μm and containing 0.15 to 13.5 wt.% Re, were obtained with a current efficiency of 66–98% from a developed dicyanoargentate–perrhenate bath based on a borate–phosphate–carbonate silver-plating electrolyte. This study was focused on the influence of bath composition, the [Ag(I)]:[ReO₄⁻] ratio, surfactant additives, applied current density, temperature, and stirring, on the alloys’ composition, structure, morphology, microhardness, adhesion, and porosity. A voltammetric analysis was conducted, considering the influence of ethanolamines on electrode processes. In baths with triethanolamine (TEA), coatings similar to a silver matrix with rhenium doped in mass fractions are likely achievable. Monoethanolamine (MEA) is recommended due to its process-activating properties. All coatings were nanocrystalline (τ = 28.5–35 nm). For deposits containing less than 10 wt.% Re, characteristic silver XRD peaks were observed, while for other deposits, additional peaks attributed probably to Re(VII) and Re(VI) oxides. A linear relationship H_v − τ^−1/2, typical for Hall–Petch plots, was obtained, confirming that grain boundaries play a crucial role in mechanical properties of coatings. The conditions for stable electrochemical synthesis of promising functional Ag-Re coatings of predetermined composition (0.7–1.5 wt.% Re) were proposed for practical use in power electronics and energy sectors for manufacturing electrical contacts operating across a wide temperature range. This was realized by deposition from an Ag-rich bath in the area of mixed electrochemical kinetics, at potential values corresponding to the region of half the limiting current: j = 2.5–6 mA cm⁻², t = 19–33 °C. Full article

In this work, hollow dodecahedral carbon structures with abundant N-doping sites and metal nanoparticles (NC-Co-CNTs) based on MOF-derivative materials were designed and prepared as host materials for lithium metal to ensure uniform lithium deposition on a Cu current collector. NC-Co-CNTs have good electrical conductivity, which ensures fast electron transport and Li⁺ transfer. The carbon nanotubes catalytically derived by Co can promote the uniform distribution of Li⁺ along the hollow dodecahedral carbon surface and deposition inside the cavity, and the larger electronegativity of N-doped sites and lithophilic sites such as Co nanoparticles can effectively adsorb lithium, inducing the Li⁺ to be deposited in the form of spherical lithium in a dendrite-free state, inhibiting the growth of dendritic lithium and improving the electrochemical performance of the lithium metal battery. Based on the above advantages, the electrodes of NC-Co-CNT-based symmetric cells present superior cycling performance for more than 1100 h with low overpotential at 1 mAh cm⁻²/1 mAh·cm⁻². Even cycling at high current density of 5 mA cm⁻² and high deposition parameters of 5 mAh cm⁻², it still cycles for up to 800 h at a relatively low overpotential. Full article

The current environmental pollution and energy crises are global concerns that must be addressed. Considering this background, three perovskites (YMnO₃, Co-doped YMnO₃, and Sn-doped YMnO₃) were synthesized via a sol–gel method and characterized by XRD, SEM, and EDX. Their water-splitting electrocatalytic activity was evaluated in a strongly alkaline medium. The highest activity was observed during hydrogen evolution reaction (HER) experiments on a glassy carbon electrode coated with a catalyst ink containing the Co-doped material. Initially, the HER overpotential value at −10 mA/cm² was 0.59 V, and the Tafel slope was 115 mV/dec. Following a chronoamperometric stability test, the overpotential became 0.46 V and the Tafel slope 119 mV/dec. The higher HER activity of the modified electrode is ascribed to a higher number of catalytic sites exposed to the electrolyte solution and the presence of Carbon Black. The photocatalytic activity of the perovskites was investigated as well, using different experimental conditions and simulated solar irradiation. The results show that the photocatalytic activity can be improved by doping, and the highest removal efficiency is achieved in the presence of the Co-doped YMnO₃ when ~60% of 17α-ethynylestradiol is degraded. Furthermore, the initial pH has no favorable effect on the degradation efficiency. The reusability of Co-doped YMnO₃ was also tested and minimal activity loss was found after three photocatalytic cycles. Full article