Search Results (265)

To address the corrosion and degradation of metallic materials in seawater, tidal, and similar environments, this study employs lysine (C₆H₁₄N₂O₂) to modify graphene oxide (GO) via a hydrothermal process. The modified graphene oxide (f-GO) and poly(l-lysine) (PL) composite was characterized structurally and functionally using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) to characterize its structure and properties. A composite coating was prepared using modified graphene oxide (f-GO) and polyurethane (PU), which underwent electrochemical testing, hardness testing, corrosion rate testing, adhesion testing, impact resistance testing, and salt spray corrosion resistance testing. Experimental results indicate that C-N stretching vibration peaks appeared at all reaction temperatures. At 85 °C, f-GO85 exhibited optimal modification with a layer spacing of 1.471 nm, 72% transmittance, and superior thermal stability, confirming successful lysine grafting onto the GO surface. Corrosion resistance testing of the composite coating revealed enhanced adhesion and impact resistance, reduced corrosion rate, decreased corrosion current density in polarization curves, positive shift in corrosion potential, and higher impedance values in impedance curves, indicating improved coating density and corrosion resistance. Salt spray tests demonstrated that incorporating lysine-modified graphene oxide significantly improved the anti-corrosion performance of polyurethane coatings. Optimal corrosion resistance was achieved when the modified graphene oxide content was 0.2 wt%. Full article

With the rapid depletion of natural graphite, the synthesis of artificial graphite from high-carbon precursors has garnered growing interest. However, conventional artificial graphitization typically requires extremely high temperatures. This study demonstrates that natural halloysite mineral can serve as an effective catalyst to lower the graphitization temperature threshold of anthracite. The results show that halloysite exerts a pronounced catalytic effect within the temperature range of 1400–2300 °C. The enhancement in graphitization is primarily attributed to the formation and subsequent decomposition of intermediate phases between halloysite and the carbon matrix. From 1400 to 1700 °C, the interlayer spacing decreases significantly with halloysite as a catalyst due to the nucleation of highly ordered “multilayer graphene” structures surrounding intermediates. However, these graphene layers exhibit a confined and curved morphology that spatially restricts crystallite growth, resulting in relatively small in-plane (L_a) and stacking (L_c) crystallite dimensions. Moreover, multilayer graphene originating from intermediate crystal corners tends to generate numerous dislocation defects. From 1700 to 2300 °C, significant increases in both L_a and L_c are observed, accompanied by a marked improvement in structural order. This evolution is driven by the progressive inward decomposition of intermediate phases, which causes the “circular-shaped” graphene domains to collapse at the dislocation defects and subsequent straightening of the curved graphene layers. These findings provide new microstructural insights into mineral-catalyzed graphitization mechanisms in anthracite and present a promising pathway toward energy-efficient production of synthetic graphite. Full article

Vacuum circuit breakers (VCBs) have been extensively employed in switching shunt capacitor banks. However, research on the prestrike characteristics of double-break VCBs in making power frequency voltage remains limited. This study aims to investigate the influence of different closing time differences on the prestrike characteristics of double-break VCBs in making power frequency voltage, and to compare these influences with those of single-break VCBs. Experiments were conducted using vacuum interrupters rated at 24 kV, with contacts made of CuCr40 alloy doped with 1 wt% graphene. Taking the closing time of the high-voltage break as the time zero point, three closing time differences (0 ms, 0.727 ms, and −0.347 ms) were set, and experiments were carried out at six closing phase angles (from 0° to 150° in 30° increments) for each condition. The experimental results demonstrate that when the closing of the high-voltage break lags behind that of the low-voltage break by 0.347 ms, the double-break VCB exhibits optimal prestrike performance, where prestrike is almost entirely suppressed except at the 90° phase angle. Furthermore, the prestrike performance during the closing of the double-break VCB is significantly superior to that of the single-break VCB, characterized by a steeper RDDS curve. These findings provide a theoretical basis for the design of control-switching double-break VCBs. Full article

Using molecular dynamics simulations of a planar graphene sheet, we investigate the temperature dependence of its mechanical behavior under uniaxial tensile stress applied either in the armchair or zigzag direction. Stress–strain curves are calculated for different temperatures, and the corresponding dependence of various elastic parameters is discussed. Fracture stress and strain, as well as the Young’s modulus, decrease almost linearly with temperature, in accordance with previous investigations. An almost linear variation in the third-order elastic modulus with temperature is demonstrated, revealing opposite trends for uniaxial loadings in the armchair or zigzag direction. The detailed dependence of the distributions of bond lengths and bond angles both on strain and temperature is presented for the first time, along with approximate analytical expressions. The latter accurately describe the numerically obtained distributions. Full article

This study presents an analytical investigation of the thermomechanical stability of hyperbolic doubly curved shells reinforced with graphene origami auxetic metamaterials (GOAMs) and resting on a Pasternak elastic foundation. The proposed model integrates shell geometry, thermal–mechanical loading, and architected auxetic reinforcement to capture their coupled influence on buckling behavior. Stability equations are derived using the First-Order Shear Deformation Theory (FSDT) and the principle of virtual work, while the effective thermoelastic properties of the GOAM phase are obtained through micromechanical homogenization as functions of folding angle, mass fraction, and spatial distribution. Closed-form eigenvalue solutions are achieved with Navier’s method for simply supported boundaries. The results reveal that GOAM reinforcement enhances the critical buckling load at low folding angles, whereas higher folding induces compliance that diminishes stability. The Pasternak shear layer significantly improves buckling resistance up to about 46% with pronounced effects in asymmetrically graded configurations. Compared with conventional composite shells, the proposed GOAM-reinforced shells exhibit tunable, folding-dependent stability responses. These findings highlight the potential of origami-inspired graphene metamaterials for designing lightweight, thermally stable thin-walled structures in aerospace morphing skins and multifunctional mechanical systems. Full article

Graphene can effectively enhance the impedance matching and dielectric loss capability in dielectric loss/magnetic loss dual-mechanism absorbers, and influences the overall magnetic loss capability of the material through various mechanisms. In this study, carbonyl iron/graphene composite absorbers with different graphene contents were prepared using the solution blending method. An absorbing honeycomb structure was fabricated using aramid honeycomb as the substrate via an impregnation process. The complex permittivity and complex permeability of the materials were tested within the 2–18 GHz frequency band. The absorption capability and mechanism were comprehensively analyzed alongside the reflection loss curves. Furthermore, the influence of graphene on the magnetic loss capability of the dual-mechanism absorbing material was investigated through VSM tests. Research indicates that the content and distribution of graphene can enhance the dispersion of CIP. In addition to a significant improvement in dielectric loss, it also exerts an influence on magnetic loss through a synergistic mechanism. Full article

In order to study the durability of graphene oxide concrete composite in chloride and sulfate environments, graphene oxide concrete composite specimens were immersed in a mixed solution of 5% sodium sulfate and sodium chloride. After dry–wet cycle immersion and long-term natural immersion, the compressive strength, strength reduction rate, and mass loss rate of concrete specimens were tested. The microstructure was analyzed by scanning electron microscopy (SEM), and the durability of graphene oxide concrete composite in chloride and sulfate environments was analyzed. The results show that with the increase in corrosion age, under dry–wet cycle immersion and long-term natural immersion, the compressive strength reduction coefficient and mass loss rate of graphene oxide concrete composite specimens with 0.07% content are the smallest. The stress–strain curve of concrete after corrosion is flatter than that of uncorroded concrete, and the ductility of concrete specimens after corrosion increased. Through microstructure analysis, it can be seen that the internal structure of graphene oxide concrete composite test block is more compact, the hydration products are regulated, the corrosion of concrete is delayed, and the durability performance is better. Graphene oxide is used to improve the strength and durability of concrete, and the recommended dosage is 0.07%. Full article

In this study, the nonlinearity characteristics of bilayer graphene field-effect transistors (Bi-GFETs) are analyzed by using a small-signal equivalent circuit. The static nonlinearity is determined by applying mathematical operation on the drain current equation of Bi-GFETs. Furthermore, the closed expressions for the second- and third-order harmonic distortion (HD) and the intermodulation (IM) distortion of the second- and third-order for Bi-GFETs are analyzed graphically. Dynamic nonlinearity is studied and illustrated in the results by examining the input and output characteristics; i.e., the drain current versus the negative drain to the source voltage and the transfer characteristic curve at various gate voltages controlled by both the top gate as well as the back gate. The characteristic behavior of the gate voltage in Bi-GFETs at short channel lengths is observed and compared; that is, the characteristic curves exhibits strong nonlinearity, with a low power point with some kinks at high gate biasing and a constant linear region at low gate biasing. The quantitative values of the second-order harmonic distortion (HD) and intermodulation distortion (IM) of the proposed analytical model are −40 dB and −45 dB. Quantitative and qualitative outcomes of the characteristics of Bi-GFETs are compared with existing experimental data, which is available in the literature. Full article

To study the adsorption of lanthanide (Ln) atoms on graphene containing a Stone–Wales defect, we used a cluster model (SWG) and performed calculations at the PBE-D2/DNP level of the density functional theory. Our previous study, where the above combination was complemented with the ECP pseudopotentials, was only partially successful due to the impossibility of calculating terbium-containing systems and a serious error found for the SWG complex with dysprosium. In the present study we employed the DSPP pseudopotentials and completely eliminated the latter two failures. We analyzed the optimized geometries of the full series of fifteen SWG + Ln complexes, along with their formation energies and electronic parameters, such as frontier orbital energies, atomic charges, and spins. In many regards, the two series of calculations show qualitatively similar features, such as roughly M-shaped curves of the adsorption energies and trends in the changes in charge and spin of the adsorbed Ln atoms, as well as the spin density plots. However, the quantitative results can differ significantly. For most characteristics we found no evident correlation with the lanthanide contraction. The only dataset where this phenomenon apparently manifests itself (albeit to a limited and irregular degree) is the changes in the closest Ln^…C approaches. Full article

Detecting pharmaceuticals in environmental matrices, particularly in wastewater, is crucial due to their potential environmental occurrence and unpredictable ecological and health-related consequences. These substances, often present in trace amounts, require highly sensitive and selective analytical methods for effective monitoring. A modified version of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method was evaluated to evaluate 18 pharmaceuticals and 2 metabolites in wastewater samples using liquid chromatography with tandem mass spectrometry (LC-MS/MS). The method’s performance was assessed using linearity, recovery, precision, limits of quantification (LOQ) and detection (LOD), and the matrix effect (ME). The final method was based on acetonitrile, Na₂EDTA, citrate buffer, and graphene oxide (GO). Finally, the calibration curves prepared in acetonitrile and the matrix extract showed a correlation coefficient of 0.99. Most of the compounds had LOQ values lower than 0.5 μg⋅mL⁻¹. Recoveries were achieved in the 70–98% range, with RSD lower than 13%. GO allowed the elimination of the ME, which occurred in the range of −11% to 15%. The results indicate that a low-cost and straightforward method is suitable for routinely monitoring pharmaceuticals in wastewater, which is crucial for minimizing the impact of pollutants on aquatic ecosystems. Full article

Loess Plateau is the region with the most concentrated loess distribution and the deepest loess soil layer in the world, and it is facing serious problems of soil erosion and ecological degradation. The nano carbon modification of soil surface properties is a novel strategy for soil improvement and enhancing the soil’s capacity to sequester carbon, which has been extensively researched. However, the mechanisms underlying the influence of carbon surface structure on the efficacy of loess soil remediation remain unclear. Herein, graphene oxide (GO) with a unique two-dimensional structure and adjustable surface properties was optimized as a model carbon filler to investigate the modification effect on loess. As a result, the addition amount of 0.03% GO significantly reduced the disintegration amount of loess, but, if inhibited for a long time, the disintegration effect would weaken. The highly reduced GO can delay the loess disintegration rate due to its enhanced hydrophobicity, but the inhibitory effect fails over a long period of time. After adjusting the reduce degree with a 50% SA (sodium ascorbate), the water-holding capacity of the modified soil in the high suction range is enhanced. This study reveals the synergistic mechanism of the sheet structure and surface properties of GO on the water stability of loess, providing a reference for the prevention and control of soil erosion and ecological restoration in the Loess Plateau. Full article

In this study, gold nanoparticles (AuNPs) and AuNPs-graphene oxide (AuNPs@GO) nanostructures were synthesized in aqueous media using an in-situ photochemical method with bis-acyl phosphine oxide (BAPO) photoinitiator as a photoreducing agent in the presence of HAuCl₄. The parameters for synthesis were arranged to obtain stable and reproducible dispersions with desirable chemical and optical properties. Both AuNPs and AuNPs@GO were employed as sensing platforms for the detection of epinephrine in two concentration ranges: micromolar (µM) and nanomolar (nM). Field emission scanning electron microscopy (FE-SEM), Dynamic Light Scattering (DLS), UV-Vis absorption, fluorescence emission, and Fourier Transform Infrared (FT-IR) spectroscopy techniques were used to investigate the morphological, optical, and chemical properties of the nanostructures as well as their sensing ability towards epinephrine. Fluorescence spectroscopy played a crucial role in demonstrating the high sensitivity and effectiveness of these systems, especially in the low concentration (nM) range, confirming their strong potential as fluorescence-based sensors. By constructing calibration curves on best linear subranges, limit of detection (LOD) and limit of quantification (LOQ) were calculated with two different approaches, SE_intercept and S_y/x. Among all the investigated nanostructures, AuNPs@GO exhibited the highest sensitivity towards epinephrine. The efficiency and reproducibility of the in-situ photochemical AuNPs synthesis approach highlight its applicability in small-molecule detection and particularly in analytical and bio-sensing applications. Full article

In Gen-IV nuclear reactors, structural materials must endure unprecedented levels of neutron irradiation and hydrogen exposure, posing significant challenges for traditional Ni-based alloys. This study evaluates Ni–graphene nanocomposites (NGNCs) as a promising solution, leveraging their inherent radiation tolerance and hydrogen diffusion suppression. Using molecular dynamics simulations, we investigate how Ni/graphene interfaces influence mechanical properties under combined hydrogen permeation and displacement damage. Key parameters, such as hydrogen concentration, displacement damage level, strain rate, and temperature, are systematically varied to assess their impact on stress–strain behavior (including Young’s modulus and tensile strength), with comparisons to single-crystal nickel. Our findings reveal that NGNCs exhibit distinct mechanical responses characterized by serrated stress–strain curves due to interfacial slip. Hydrogen and irradiation effects are complex: low hydrogen levels can increase Young’s modulus, while higher concentrations and irradiation generally degrade strength, with NGNCs being more affected than single-crystal nickel. Additionally, NGNCs show enhanced thermal stability but increased strain rate sensitivity. These results provide critical insights for designing materials that balance reinforcement with environmental resilience in nuclear applications. Full article

Our study develops two configurations of MoS₂ and graphene heterostructures—MoS₂ on graphene (MG) and graphene on MoS₂ (GM)—to investigate biomolecule sensing in field-effect transistor (FET) biosensors. Leveraging MoS₂ and graphene’s distinctive properties, we employ specialized functionalization techniques for each configuration: graphene with MoS₂ on top uses a silane-based method with triethoxysilylbutyraldehyde (TESBA), and MoS₂ with graphene on top utilizes 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE). Our research explores the application of MoS₂–Graphene heterostructures in biosensors, emphasizing the roles of synthesis, fabrication, and material functionalization in optimizing sensor performance. Through our experimental investigations, we have observed that doping MoS₂ and graphene leads to noticeable changes in the Raman spectrum and shifts in transfer curves. Techniques such as XPS, Raman, and AFM have successfully confirmed the biofunctionalization. Transfer curves were instrumental in characterizing the biosensing performance, revealing that GM configurations exhibit higher sensitivity and a lower limit of detection (LOD) compared to MG configurations. We demonstrate that GM heterostructures offer superior sensitivity and specificity in biosensing, highlighting their significant potential to advance biosensor technologies. This research contributes to the field by detailing the creation process of vertical MoS₂–graphene heterostructures and evaluating their effectiveness in accurate biomolecule detection, advancing biosensing technology. Full article

Sealing treatment is widely used as a simple and low-cost process to improve the long-term corrosion resistance of Fe-based amorphous coatings. In this study, an eco-friendly graphene modified waterborne acrylic sealant(WFS) with strong permeability was prepared by emulsion polymerization and GO@SiO₂ was introduced as a reinforcing material to increase the withstand resistance of the hybrid sealant to Cl⁻. A combination of ultrasonic excitation and vacuum sealing effectively promotes the penetration of the waterborne hybrid sealant into the pores of the coating. A 3D X-ray scan confirmed the sealant penetration depth of 160 μm. The natural properties of the emulsion were characterized by a particle size analyzer, FTIR, TGA-DSC and TEM. Potentiodynamic polarization curves and AC impedance spectroscopy analysis showed that GO@SiO₂ has a strong blocking ability to Cl⁻, which greatly promotes the integrity of the passive film. It is anticipated that the novel eco-friendly waterborne hybrid sealants with strong permeability will find applications in a variety of porous hard coatings. Full article