Search Results (12)

The ongoing development of maritime powers has driven markedly growing requirements for novel naval and civilian vessel categories in recent years. The import temperature of gas turbines is rising, and the issue of corrosion can no longer be ignored, creating an urgent need to develop coatings with high-temperature resistance, corrosion resistance, and good toughness. This study utilized plasma spraying technology to prepare composite AT13 ceramic coatings with 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% GO/Cu (GO:Cu = 1:10) content. It systematically investigated the effects of GO/Cu doping on the porosity, Vickers hardness, fracture toughness, thermal shock resistance, and corrosion resistance of the AT13 coatings while exploring the corrosion behavior of the composite coatings. The experimental results indicate that doping with GO/Cu can effectively fill the pores of the coatings, leading to an overall improvement in coating performance. The coating with 10 wt.% doping (G2) exhibited the best comprehensive performance, with a 72% reduction in porosity compared to the original coating, a 23.2% increase in Vickers hardness, a 31.4% enhancement in fracture toughness, and an 83% decrease in corrosion rate. It also demonstrated the best thermal shock resistance, maintaining a relatively intact surface after 31 days of immersion in artificial seawater, with only a few pitting and cracking defects observed in the areas of corrosion. Full article

Advanced thermal interface materials with high thermal conductivity are crucial for addressing the heat dissipation issue in high-power, highly integrated electronic devices. One great potential way in this field is to take advantage of cooling copper foil (Cu) materials based on graphene (G). However, the current manufacturing of these cooling copper foil materials is accompanied by high cost, process complexity, and environmental problems, which limit their development and application. In this work, a simple, low-cost, environmentally friendly graphene-copper foil composite film (rGO/G-Cu) with high thermal conductivity was successfully prepared using graphene oxide directly as a dispersant and binder of graphene coating. The microstructure characterization, thermal conductivity and thermal management performance tests were carried out on the composite films. The results demonstrate that compared to pure copper foil (342.47 W·m⁻¹·K⁻¹) and 10% PVA/G-Cu (367.98 W·m⁻¹·K⁻¹) with polyvinyl alcohol as a binder, 10% rGO/G-Cu exhibits better thermal conductivity (414.56 W·m⁻¹·K⁻¹). The introduction of two-dimensional graphene oxide effectively enhances the adhesion between the coating and the copper foil while greatly improving its thermal conductivity. Furthermore, experimental results indicate that rGO/G-Cu exhibits excellent heat transfer performance and flexibility. This work is highly relevant to the development of economical and environmentally friendly materials with high thermal conductivity to meet the increasing demand for heat dissipation. Full article

This study investigates the enhancement of wear resistance in CuCrZr rails through the plasma cladding of CuCrZr-GO coatings with a varying graphene oxide (GO) content. The microstructure, phase composition, and mechanical properties of CuCrZr coatings containing 0%, 0.2%, 0.4%, 0.6%, and 0.8% GO were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), ESD surface scanning, friction and wear tests, and hardness analysis. The findings indicated that increasing the GO content from 0% to 0.6% results in a transition in the coating microstructure from columnar to equiaxed crystals, leading to an improved density. However, at 0.8% GO, numerous porosity defects were observed. The coating containing 0.6% graphene oxide (GO) exhibited a superior performance, with a hardness of 75, a friction coefficient of approximately 0.7, and a wear mass of 2.84 mg under a 10 N load. In comparison to the CuCrZr coating lacking GO, the hardness showed an increase of around 4.8%, the friction coefficient decreased by approximately 5.1%, and the wear mass diminished by 59.4%. These findings hold significant implications for extending the operational lifespan of electromagnetic railguns. Full article

Low friction and high wear resistance are critical properties for sliding bearings. In this research, advanced Cu/GO nanocomposite coatings have been developed by a brush plating method to improve the tribological performance of brass-based sliding bearings. A series of brush plating studies under voltages from 2 to 6 V with different GO concentrations (0.2–0.8 g/L) was conducted, and the coating microstructures were characterised by SEM, EDX, GDOES and XRD and the tribological behaviour of the Cu/GO composite coatings were evaluated using dry ball-on-plane tribological tests The experimental results have demonstrated that GO can be successfully introduced into the whole composite coating layer; the Cu/GO composite coatings can reduce the friction of brass and increase its wear resistance by two orders of magnitude, mainly due to the self-lubricating GO added into the coatings. Full article

The rise of antimicrobial resistance has brought into focus the urgent need for the next generation of antimicrobial coating. Specifically, the coating of suitable antimicrobial nanomaterials on contact surfaces seems to be an effective method for the disinfection/contact killing of microorganisms. In this study, the antimicrobial coatings of graphene@curcumin-copper (GN@CR-Cu) were prepared using a chemical synthesis methodology. Thus, the prepared GN@CR-Cu slurry was successfully coated on different contact surfaces, and subsequently, the GO in the composite was reduced to graphene (GN) by low-temperature heating/sunlight exposure. Scanning electron microscopy was used to characterize the coated GN@CR-Cu for the coating properties, X-ray photon scattering were used for structural characterization and material confirmation. From the morphological analysis, it was seen that CR and Cu were uniformly distributed throughout the GN network. The nanocomposite coating showed antimicrobial properties by contact-killing mechanisms, which was confirmed by zone inhibition and scanning electron microscopy. The materials showed maximum antibacterial activity against E. coli (24 ± 0.50 mm) followed by P. aeruginosa (18 ± 0.25 mm) at 25 µg/mL spot inoculation on the solid media plate, and a similar trend was observed in the minimum inhibition concentration (80 µg/mL) and bactericidal concentration (160 µg/mL) in liquid media. The synthesized materials showed excellent activity against E. coli and P. aeruginosa. These materials, when coated on different contact surfaces such medical devices, might significantly reduce the risk of nosocomial infection. Full article

Antifriction materials, such as silver, copper, Babbitt B83, and graphene oxide (GO), were used to prepare running-in coatings on the surface of bronze QSn10-1 by electro-spark deposition (ESD). The analyses of mass transfer, roughness, thickness, morphology, composition, nanoindentation, and tribological properties of the coatings were investigated. The results showed that the running-in coatings were dense with refined grains that were uniformly distributed and in a metallurgical bond state with the tin bronze substrate. At optimum process parameters, the mass transfer was 244.2 mg, the surface roughness was 15.9 μm, and the thickness of the layers was 160 μm. The diffraction peaks clearly indicated the phases corresponding to α-Sn, SbSn, Cu₆Sn₅, and Cu, and a phase of Ag₃Sn appeared. The modulus and the hardness of the running-in coatings were 24.9% and 14.2% of the substrate, and the deformation ratio of the coatings was 10.2% higher than that of the substrate. The friction coefficient of the running-in coatings was about 0.210 after the running-in stage, which was 64.8% of that of the substrate (0.324). The main wear mechanism of the running-in coatings under optimal process parameters is plastic deformation, scratching, and slight polishing. The running-in coating deformation under the action of high specific loads provides the automatic adjustment of parts and compensation for manufacturing errors. Full article

In this study, Cu matrix composites reinforced with reduced graphene oxide-coated submicron spherical Cu (SSCu@rGO) exhibiting both high-strength plastic product (UT) and high electrical conductivity (EC) were prepared. SSCu@rGO results in the formation of Cu₄O₃ and Cu₂O nanotransition layers to optimize the interface combination. In addition, as a flow carrier, SSCu@rGO can also render graphene uniformly dispersed. The results show that SSCu@rGO has a significant strengthening effect on the Cu matrix composites. The relative density (RD) of the SSCu@rGO/Cu composites exceeds 95%, and the hardness, UT, and yield strength (YS) reach 106.8 HV, 14,455 MPa% (tensile strength (TS) 245 MPa, elongation (EL) 59%), and 119 MPa; which are 21%, 72%, and 98% higher than those of Cu, respectively. Furthermore, EC is 95% IACS (International Annealed Copper Standard), which is also higher than that of Cu. The strength mechanisms include transfer load strengthening, dislocation strengthening, and grain refinement strengthening. The plastic mechanisms include the coordinated deformation of the interface of the Cu₄O₃ and Cu₂O nanotransition layers and the increase in the fracture energy caused by graphene during the deformation process. The optimized EC is due to SSCu@rGO constructing bridges between the large-size Cu grains, and graphene on the surface provides a fast path for electron motion. This path compensates for the negative influence of grain refinement and the sintering defects on EC. The reduced graphene oxide-reinforced Cu-matrix composites were studied, and it was found that the comprehensive performance of the SSCu@rGO/Cu composites is superior to that of the rGO/Cu composites in all aspects. Full article

In this work, silver (Ag) decorated reduced graphene oxide (rGO) coated with ultrafine CuO nanosheets (Ag-rGO@CuO) was prepared by the combination of a microwave-assisted hydrothermal route and a chemical methodology. The prepared Ag-rGO@CuO was characterized for its morphological features by field emission scanning electron microscopy and transmission electron microscopy while the structural characterization was performed by X-ray diffraction and Raman spectroscopy. Energy-dispersive X-ray analysis was undertaken to confirm the elemental composition. The electrochemical performance of prepared samples was studied by cyclic voltammetry and galvanostatic charge-discharge in a 2M KOH electrolyte solution. The CuO nanosheets provided excellent electrical conductivity and the rGO sheets provided a large surface area with good mesoporosity that increases electron and ion mobility during the redox process. Furthermore, the highly conductive Ag nanoparticles upon the rGO@CuO surface further enhanced electrochemical performance by providing extra channels for charge conduction. The ternary Ag-rGO@CuO nanocomposite shows a very high specific capacitance of 612.5 to 210 Fg⁻¹ compared against rGO@CuO which has a specific capacitance of 375 to 87.5 Fg⁻¹ and the CuO nanosheets with a specific capacitance of 113.75 to 87.5 Fg⁻¹ at current densities 0.5 and 7 Ag⁻¹, respectively. Full article

Nowadays, metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted significant research attention for gas sensing applications. Herein, a novel composite material is synthesized by combining two p-type semiconductors, i.e., Cu₂O and rGO, and a p-p-type gas sensor is assembled for NO₂ detection. Briefly, polypyrrole-coated cuprous oxide nanowires (PPy/Cu₂O) are prepared via hydrothermal method and combined with graphene oxide (GO). Then, the nanocomposite (rGO/PPy/Cu₂O) is obtained by using high-temperature thermal reduction under Ar atmosphere. The results reveal that the as-prepared rGO/PPy/Cu₂O nanocomposite exhibits a maximum NO₂ response of 42.5% and is capable of detecting NO₂ at a low concentration of 200 ppb. Overall, the as-prepared rGO/PPy/Cu₂O nanocomposite demonstrates excellent sensitivity, reversibility, repeatability, and selectivity for NO₂ sensing applications. Full article

A glassy carbon electrode (GCE) coated with delafossite CuCrO₂ loading on the nitrogen-doped reduced graphene oxide (N-rGO) and multiwalled carbon nanotubes (MWCNT) composite (N-rGO-MWCNT/CuCrO₂) was applied to the hydrogen evolution reaction and Bisphenol-A (BPA) detection. First, the N-rGO-MWCNT composite was prepared by in situ chemical reduction with caffeic acid as a reducing agent. Then, CuCrO₂ was accumulated on the N-rGO-MWCNT surface to form N-rGO-MWCNT/CuCrO₂ composite. The morphology structure of the N-rGO-MWCNT/ CuCrO₂ composite was analyzed by different characterization techniques. Besides, the GCE/N-rGO-MWCNT/CuCrO₂ composite electrode was investigated for hydrogen evolution reaction (HER), which shows an excellent electrocatalytic activity with a low over-potential, increasing reduction current, and a small Tafel slope of 62 mV·dec⁻¹ at 10 mA·cm⁻² with long-term stability. Moreover, the electrochemical determination of BPA was in the range of 0.1-110 µM, and low detection limit of 0.033 µM (S/N = 3) with a higher sensitivity of 1.3726 µA µM⁻¹ cm⁻². Furthermore, the prepared GCE/N-rGO-MWCNT/CuCrO₂ electrode shows effective detection of BPA in food samples with acceptable recoveries. Hence, the finding of GCE/N-rGO-MWCNT/CuCrO₂ can be observed as an impressive catalyst to the electrocatalytic activity of HER and BPA oxidation. Full article

In this paper, we designed Ag nanoparticles coated with a Cu₂O shell, which was successfully decorated on reduced graphene oxide (rGO) via a solid-state self-reduction. The Cu₂O, Ag@Cu₂O, and Ag@Cu₂O-rGO nanocomposites were synthesized and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis, and XPS to evaluate the properties of the composites. In order to compare the chemical catalytic activity, the Cu₂O, Ag@Cu₂O, and Ag@Cu₂O-rGO nanocomposites were employed for the catalytic reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) in aqueous solution. The Ag@Cu₂O-rGO nanocomposite exhibited excellent catalytic activity due to the intense interaction and high degree of electron transfer among Ag, Cu₂O, and rGO. The rGO acted as the platform to bridge the isolated nanoparticles; furthermore, the electrons could quickly transfer from the Ag core to the Cu₂O shell, which improved the chemical catalytic efficiency. Full article

Nanocomposite powders based on metal-coated graphene were synthesized using an in-situ co-reduction method in order to improve wettability and interfacial bonding between graphene and metal. Graphene oxide (GO) of 2~3 atomic layers was synthesized using the Hummer’s method with graphite as a raw material and then dispersed into a dispersing agent solution mixed with N-Methyl pyrrolidone and deionized water to form a homogeneous GO suspension, which was finally added into electroless plating solutions for the reduction process. Copper-coated graphene (Cu@graphene) and nickel-coated graphene (Ni@graphene) were synthesized using this one-step and co-reduction method by mixing salt solutions containing metal ions and GOs into the plating solution. The Cu ions or Ni ions were adsorbed and bonded onto the edges and surfaces of graphene, which was reduced from the GOs using a strong reducing agent of ascorbic acid or sodium borohydride. Crystalline Cu particles with an average size of about 200 nm were formed on the surface of graphene, whereas amorphous or nanocrystalline Ni particles with an average size of 55 nm were formed on the surface of graphene. Distribution of these metal particles on the graphene is homogeneous and highly dispersed, which can effectively improve the sinterability of composite powders. Cohesive energy distribution between graphene and metal interface was analyzed using first-principle calculation method. Formation mechanism of metal coated graphene was identified to be that both the GO and metal ions were simultaneously reduced in the reducing agents and thus a chemical bonding of graphene/metal was formed between the metal particles and graphene. Full article