Search Results (145)

Graphene, a remarkable two-dimensional material, enhances the mechanical properties of high-entropy alloys as a reinforcing phase. This study investigated the influence of vacancy defects in graphene on the strengthening effect of FeNiCrCoCu high-entropy alloy through molecular dynamics simulations. The findings reveal that vacancy defects diminish graphene’s strength, resulting in its premature failure. In tensile tests, graphene with defects lowers the yield stress of the composite, yet it retains the ability to impede dislocations. Conversely, graphene exhibits a more pronounced strengthening effect during compression. Specifically, when the deletion of C atoms is less than 1%, the impact is negligible; between 1% and 6%, the strengthening effect diminishes; and when it surpasses 6%, the strengthening effect virtually ceases to exist. This research offers a theoretical foundation for optimizing graphene-reinforced composites. Full article

Films of a Ni/Al-layered double hydroxide intercalated with reduced graphene oxide were deposited, by means of a simple and rapid electrochemical synthesis, on Pt electrodes previously submitted to a special cleaning procedure. The aim of the research was to determine whether the better electrocatalytic properties of the Ni(III)/Ni(II) couple, due to the presence of the carbon nanomaterial, as compared to the Ni/Al-LDH alone, could allow glucose detection at physiological pHs, as normally LDHs work as redox mediators in basic solutions. Chronoamperometric experiments were carried out by applying a potential of 1.0 V vs. SCE to the electrode soaked in solutions buffered at pHs from 5.0 to 9.0 to which glucose was continuously added. The steady-state currents increased as the pH solution increased, but at pH = 7.0 the modified electrode exhibited a fast and rather sensitive response, which was linear up to 10.0 mM glucose, with a sensitivity of 0.56 A M⁻¹ cm⁻² and a limit of detection of 0.05 mM. Our results suggest the potential application of Ni/Al-LDH(ERGO) composite for the non-enzymatic detection of glucose or other oxidizable analytes under biological conditions. Full article

This study fabricated a C/C-CuNi composite using the hydrothermal co-deposition method and investigated its friction and wear behavior as well as the underlying mechanisms after being subjected to arc discharge ablation. The results indicate that the graphitization degree of the material matrix was significantly enhanced after arc discharge ablation, accompanied by a transformation in the carbon microstructure. Carbon nanotubes and graphene structures were generated in the arc ablation zone. Under low arc discharge density, limited pits and open pores are formed on the material surface, with the generated graphene structures effectively reducing friction. Specifically, CN-5 exhibited a stable friction coefficient, a wear rate of 5.2 mg/km, and partial self-repair capability. In contrast, CN-10, under high arc discharge density, suffered from structural collapse, matrix-fiber debonding, and extensive open pores, leading to increased surface roughness. The combined effects of frictional heat and Joule heating elevated the wear surface temperature, triggering matrix oxidation and a sharp rise in wear rate to 14.7 mg/km. The wear mechanisms of C/C-CuNi composites under continuous arc conditions involve arc erosion wear, oxidative wear, abrasive wear, and adhesive wear. Full article

Nanotechnology has emerged as a highly focused field of research due to the unique properties of nanometric materials, particularly their large specific surface areas and excellent adsorption capabilities. This study investigated the synthesis of materials based on graphene oxide (GO) functionalized with different metal oxides (MnO₂, Fe₃O₄, CuO, NiO), with potential applications in water decontamination. The morphological, structural, and compositional properties of these nanocomposites were extensively characterized using different experimental techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) for magnetic property evaluation. Preliminary adsorption tests were performed for the removal of pesticides and drugs from aqueous solutions. The synthesized materials demonstrated a higher affinity for selected pesticides compared to drugs. The best removal efficiencies were 98.59% for cymoxanil, 97.93% for triadimefon, 63.33% for sulfamethoxazole, and 99.59% for diclofenac. The results indicate that the functionalization of GO with metal oxides modifies the material’s structure, increasing its potential for environmental applications such as water purification. Full article

Combining carbon materials with oxides in a hybrid electrode is an effective way to control supercapacitor performance in terms of balancing energy and power density with cycling stability. However, it is still unclear how the mixing method of each component affects the supercapacitor performance. In this study, the influence of mixing reduced graphene oxide (rGO) with ilmenite-type nickel-manganese oxide (NiMnO₃) on the capacitive behaviour of the resulting composites is investigated. Two preparation methods are compared: mechanical mixing and ultrasonication. The capacitive characteristics were evaluated in hybrid supercapacitors using 6M KOH electrolyte. The bulk, surface, and morphological changes of the composites after long-term cycling were probed by EIS and ex situ XRD, XPS, and SEM analyses. It is established that the composites obtained by mechanical mixing exhibit better performance due to the stable contact between rGO and NiMnO₃ particles, favourable surface reactions with KOH and preserved morphology of rGO. These findings indicate that efficient hybrid electrodes can be achieved without relying on costly synthesis techniques such as hydrothermal or ultrasonic treatments. Full article

NiFe₂O₄ and TiO₂ are widely studied for photoelectrochemical (PEC) applications due to their unique properties. Nitrogen-doped graphene (NG) and metal–organic frameworks (MOFs), such as MIL-100(Fe) (where MIL stands for Materials of Lavoisier Institute), are commonly incorporated to enhance PEC performance by offering a high surface area and facilitating efficient charge transport. Composite systems are commonly employed to overcome the limitations of individual PEC catalysts. In this study, a highly efficient NiFe₂O₄/NG@MIL-100(Fe)/TiO₂ photoanode was developed to enhance photoelectrochemical water-splitting performance. The composite was synthesized via a hydrothermal method with a two-step heating process. X-ray diffraction confirmed the expected crystal structures, with peak broadening in NiFe₂O₄ indicating reduced crystallite size and increased lattice strain. X-ray photoelectron spectroscopy of the Ni 2p and Fe 2p regions validated the successful integration of NiFe₂O₄ into the composite. Electrochemical analysis demonstrated excellent performance, with linear sweep voltammetry achieving a peak photocurrent density of 3.5 mA cm⁻² at 1.23 V (vs RHE). Electrochemical impedance spectroscopy revealed a reduced charge-transfer resistance of 50 Ω, indicating improved charge transport. Optical and electronic properties were evaluated using UV-Vis spectroscopy and Tauc plots, revealing a direct bandgap of 2.1 eV. The composite exhibited stable photocurrent under amperometric J-t testing for 2000 s, demonstrating its durability. These findings underscore the potential of NiFe₂O₄/NG@MIL-100(Fe)/TiO₂ as a promising material for renewable energy applications, particularly in photoelectrochemical water splitting. Full article

Metal–organic frameworks (MOFs) are regarded as advanced supercapacitor materials owing to their high surface area, redox-active sites, and porosity. However, their insufficient charge carrier mobility remains a critical limitation for practical application. Integrating MOFs with conductive carbon substrates is an effective strategy to break through this limitation. However, conventional carbon materials often require complex preparation methods and pre-activation steps for use in MOF composites. Herein, multilayer graphene (MLG) mechanically exfoliated from expandable graphite is employed as a substrate, and a van der Waals force-assisted chemical deposition method is developed to directly anchor Ni-MOF onto its surface without requiring pre-activation treatment. To optimize the composite, Ni-MOFs with various mass loadings are synthesized on MLG surface. The morphological characteristics and energy storage performance of these composites are thoroughly characterized. Ni-MOF/MLG-0.30 (with a 70.8% Ni-MOF loading on MLG) features a porous stacking structure of well-crystalline Ni-MOF parallelogram nanosheets on MLG, exhibiting optimal electrochemical performance. The composite achieves 1071.4 F·g⁻¹ at 1 A·g⁻¹, and a capacitance retention of 64.9% at the elevated current density of 10 A·g⁻¹. Meanwhile, the composite maintains 63.2% of its initial capacitance after 5000 charge/discharge cycles at 4 A·g⁻¹. A hybrid supercapacitor is fabricated using Ni-MOF/MLG-0.30 cathode and activated carbon anode, delivering 27.9 Wh·kg⁻¹ energy density at 102.5 W·kg⁻¹ power output. Full article

3d transition metal oxides composed of Mn, Fe, Co, and Ni have emerged as promising candidates for supercapacitor electrode materials due to their high theoretical specific capacitance, abundant redox-active sites, variable oxidation states, environmental friendliness, and low cost. Various synthesis strategies have been developed to fabricate these nanostructures, including hydrothermal/solvothermal methods, sol–gel processing, and microwave-assisted synthesis. Among them, microwave irradiation technology, with its rapid heating characteristics and unique thermal/non-thermal effects, offers significant advantages in controlling crystallinity and particle size distribution, suppressing particle agglomeration, and enhancing material purity. Furthermore, microwave effects facilitate the self-assembly and morphological evolution of transition metal oxides, promote the formation of crystal defects, and strengthen interfacial interactions. These effects enable precise microstructural tuning, leading to an increased specific surface area and a higher density of active sites, ultimately enhancing specific capacitance, rate capability, and cycling stability. In recent years, microwave-assisted synthesis has made significant progress in constructing 3d transition metal oxides and their composites, particularly in the development of single-metal and binary-metal oxides, as well as their hybrids with carbon-based materials (e.g., graphene and carbon nanotubes) and other metal oxides. This review systematically summarizes the research progress on microwave-assisted techniques for 3d transition metal oxide-based nanomaterials, with a particular focus on the role of microwave effects in morphology control, interfacial optimization, and electrochemical performance enhancement. Additionally, key challenges in current research are critically analyzed, and potential optimization strategies are proposed. This review aims to provide new insights and perspectives for advancing microwave-assisted synthesis of 3d transition metal oxides in energy storage applications. Full article

The NiWO₄ powder was prepared by combining the hydrothermal method with calcination. Several studies have demonstrated that the NiWO₄/graphene oxide composite can enhance the electrochemical performance of the NiWO₄ material. However, no studies have investigated the use of NiWO₄/graphene oxide composite material as the cathode material in zinc-ion batteries. The successful preparation of the NiWO₄/graphene oxide composite material is verified by various characterization techniques. The NiWO₄/graphene oxide composite, which is meant to be a cathode material, is fabricated into electrode sheets and incorporated into CR2025 coin cells for electrochemical assessment. The experimental results indicate that the material exhibits a high charge–discharge specific capacity with high rates. At a current density of 0.1 A g⁻¹, it has a specific capacity of 490.2 mA h g⁻¹. Even after 2000 charge–discharge cycles at a current density of 1 A g⁻¹, the capacity remains constant at 75.2%. Through calculations, it is found that the charge storage is mainly contributed to by pseudocapacitance. Full article

Doping undermines fairness in sports and threatens athlete health, while conventional detection methods like LC-MS and GC-MS face challenges such as complex procedures, matrix interferences, and lengthy processing times, limiting on-site applications. Two-dimensional (2D) materials, including graphene, MoS₂, and metal–organic frameworks (MOFs), offer promising solutions due to their large surface areas, tunable electronic structures, and special interactions with doping agents, such as hydrogen bonding, π-π stacking, and electrostatic forces. These materials enable signal transduction through changes in conductivity or fluorescence quenching. This review highlights the use of 2D materials in doping detection. For example, reduced graphene oxide–MOF composites show high sensitivity for detecting anabolic steroids like testosterone, while NiO/NGO nanocomposites exhibit strong selectivity for stimulants like ephedrine. However, challenges such as environmental instability and high production costs hinder their widespread application. Future efforts should focus on improving material stability through chemical modifications, reducing production costs, and integrating these materials into advanced systems like machine learning. Such advancements could revolutionize doping detection, ensuring fairness in sports and protecting athlete health. Full article

In recent years, transition metal oxides (TMOs) have emerged as promising candidates for anode materials in lithium-ion batteries (LIBs) owing to their high theoretical capacities. Regrettably, most TMOs exhibit poor electronic/ionic conductivity and undergo substantial volume expansion during the lithiation/delithiation processes. In this study, an electrostatic spinning method using polyacrylonitrile, graphene, and iron(III) acetylacetonate as precursors was employed to synthesize the Fe₃O₄@G/C composite through carbon coating and graphene doping. The composition, phase structure, and morphology of the Fe₃O₄@G/C composite were thoroughly investigated. The electrochemical performance of the Fe₃O₄@G/C composite as a lithium-ion battery anode was evaluated through a continuous charge–discharge cycling test. After 100 cycles at a current density of 0.1 A/g, the specific capacity of the Fe₃O₄@G/C material remained at 595.8 mAh/g. Additionally, the incorporation of graphene leads to a reduction in the electron orbital energy of Fe, which was verified by comparing the density of states (DOS) before and after the doping. Simultaneously, the electrochemical performance of CoO@G/C and NiO@G/C composites further demonstrates that doping transition metal oxides with graphene can enhance their performance as anodes for lithium-ion batteries. We anticipate that this design concept will open new avenues for the development of transition metal oxides (TMOs) and propel their adoption in practical applications. Full article

A supercapacitor’s energy storage capability is greatly dependent on electrode materials. Layered double hydroxides (LDHs) were extensively studied as battery-type electrodes because of their 2D structure and quick intercalation/deintercalation of electrolyte ions. However, the energy storage capability for pristine LDHs is limited by their large aggregation tendency and poor electrical conductivity. Herein, a novel NiCoMn-LDH/SWCNTs (single-walled carbon nanotubes) composite electrode material, with ultrathin NiCoMn-LDH nanosheets dispersedly grown among the highly conductive networks of SWCNTs, was prepared via a facile zeolitic imidazolate framework-67 (ZIF-67)-derived in situ etching and deposition procedure. The NiCoMn-LDH/SWCNTs electrode demonstrates a specific capacitance as large as 1704.3 F g⁻¹ at 1 A g⁻¹, which is ascribed to its exposure of more active sites than NiCoMn-LDH. Moreover, the assembled NiCoMn-LDH/SWCNTs//BGA (boron-doped graphene aerogel) hybrid supercapacitor exhibits a superior capacitance of 167.9 F g⁻¹ at 1.0 A g⁻¹, an excellent energy density of 45.7 Wh kg⁻¹ with a power density of 700 W kg⁻¹, and an outstanding cyclic stability with 82.3% incipient capacitance maintained when subjected to 5000 charge and discharge cycles at the current density of 10 A g⁻¹, suggesting the significant potential of NiCoMn-LDH/SWCNTs as the electrode material applicable in supercapacitors. Full article

Nickel hydroxide has ultra-high energy storage capacity in supercapacitors, but poor electrical conductivity limits their further application. The use of graphene to improve its conductivity is an effective measure, but how to suppress the stacking of graphene and improve the overall performance of composite materials has become a new challenge. In this work, a well-designed substrate of N-doped carbon nanowires with reduced graphene oxide (NCNWs/rGO) was fabricated by growing polypyrrole (PPy) nanowires between GO nanosheets layers and then calcining them at high temperatures. This NCNWs/rGO substrate can effectively avoid the stacking of rGO nanosheets, and provides sufficient sites for the subsequent in situ growth of Ni(OH)₂, forming a uniform and stable Ni(OH)₂/NCNWs/rGO composite material. Benefiting from the abundant pores, high specific surface area (107.2 m² g⁻¹), and conductive network throughout the NCNWs/rGO substrate, the deposited Ni(OH)₂ can not only realize an ultra-high loading ratio, but also exposes more active surfaces (221.3 m² g⁻¹). After a comprehensive electrochemical test, it was found that the Ni(OH)₂/NCNWs/rGO positive materials have a high specific capacitance of 2016.6 F g⁻¹ at a scan rate of 1 mV s⁻¹, and exhibit significantly better stability. The assembled Ni(OH)₂/NCNWs/rGO//AC asymmetric supercapacitor could achieve a high energy density of 85.2 Wh kg⁻¹ at power densities of 381 W kg⁻¹. In addition, the asymmetric supercapacitor has excellent stability and could retain 70.1% of initial capacitance after 10,000 cycles. These results demonstrate the feasibility of using NCNWs/rGO substrate to construct high-performance supercapacitor electrode materials, and it is also expected to be promoted in other active composite materials. Full article

Molten salt reactors (MSRs) offer advantages such as enhanced safety, reduced nuclear waste, and cost effectiveness. However, the corrosive nature of fluoride-based molten salts challenges the longevity of structural materials. Ni-based alloys, like Hastelloy N, have shown resistance to fluoride salt corrosion but suffer from issues like helium embrittlement caused by neutron irradiation. To address these concerns, the incorporation of graphene (Gr) into Ni-based alloys is being explored. Gr’s superior mechanical properties and irradiation tolerance make it a promising reinforcement material. In this study, a Ni-17Mo alloy, a simplified model of Hastelloy N, was combined with reduced graphene oxide (RGO) using powder metallurgy. The effects of milling time and sintering temperature on the microstructure and mechanical properties were systematically studied. The results indicated that optimal sintering at 1100 °C enhanced tensile strength and ductility. Additionally, RGO incorporation improved the alloy’s strength but reduced its elongation. This research highlights the potential of Gr-reinforced Ni-based alloys for advanced MSR applications, offering insights into fabrication techniques and their impact on material properties. Full article

Black-odorous water (BOW) in urban areas poses significant risks to water safety and human health. Chemical oxygen demand (COD) is a critical parameter for the control and monitoring of BOW. However, traditional methods for COD determination are expensive, time-consuming, and involve the use of hazardous chemicals. In this study, reduced graphene oxide (rGO) and transitional metal particles (Cu, Ni) were used as working electrode materials for facile on-site determination of COD in BOW. Three composite materials (rGO/Cu, rGO/Ni, and rGO/Cu/Ni) were synthesized by one-step chemical reduction with different ratios, and their microstructure and chemical composition were characterized. Glucose solution and real water were used to evaluate the electrocatalytic performance of the different sensors. The ternary composite (rGO/Cu/Ni) screen-printed electrode sensor demonstrated excellent performance in COD analysis, with a low limit of detection (18.9 mg L⁻¹), a broad linear detection range from 53 to 1500 mg L⁻¹, and a 1.61% relative error for real water samples. The testing results were highly consistent with those obtained using the standard chromium sulfate method. This study offers promising prospects for the mass production of cost-effective COD electrochemical sensors, facilitating real-time, on-site monitoring of water bodies in major urban areas. Full article