Dispersion Of Graphene Research Articles

Insightful database-driven prediction and sensitivity analysis of electrical resistivity of nano-graphite-modified cementitious composites: a supervised machine learning regression

This study presents a novel approach to assessing electrical resistivity (ER) in nano-graphite-modified cementitious composites, a key factor for enhancing their durability and integrity. This innovative framework establishes a new paradigm in the application of ML to material science, highlighting the ability to bridge experimental and computational methods for more reliable and efficient outcomes. Leveraging a dataset of 539 cement-based materials, advanced machine learning (ML) techniques were applied, including the extremely randomized trees (XRF) algorithm, which outperformed traditional models with minimal error metrics (MAE: 37.093, MSE: 4992.581, RMSE: 8.406). The integration of Shapley’s additive explanations (SHAP) analysis further highlights the novelty of this work, revealing testing protocol (MM), ultrasonication time (SN), and graphene dosage (GN) as the most significant factors influencing ER. Longer SN times and higher GN doses reduced ER, while smaller graphene particles (2µm) increased it. Additionally, the water-to-binder (W-B) ratio and sand-to-cement (S-C) ratio showed peak ER values at 0.47 and 2.8, respectively. The four-probe method and lime-water curing produced more reliable and lower ER values compared to other methods. This data-driven methodology offers unprecedented insights into the complex interactions between material properties and ER, providing a powerful tool for optimizing composite formulations. Future research may focus on scaling this approach to larger datasets, investigating the long-term durability of composites, and refining ultrasonication techniques for better graphene dispersion.

Preparation and characterization of nanocomposites based on natural rubber/chlorobutyl rubber/graphene nanoparticle: Effect of feeding sequences, mixer type and nanoparticle concentration

AbstractBlends of natural rubber (NR)/chlorobutyl rubber (CIIR) (50/50), along with their nanocomposites containing varying amounts of graphene nanoparticles (GNPs) with and without silane, were prepared using different feeding sequences and mixers. The results indicated that when GNP was first mixed with NR before adding CIIR, the highest GNP content was found in NR; the oxygen permeability and diffusion coefficient decreased significantly by 37% and 55%, respectively. Conversely, when graphene was initially added to CIIR, it was distributed in both rubbers and at the interface, enhancing phase interaction and achieving a finer morphology. This sample exhibited the greatest improvement in mechanical properties due to specific localization of GNP and increased crosslink density. Using an internal mixer instead of a two‐roll mill improved graphene dispersion, reduced curing time, and enhanced mechanical properties. Although the presence of silane reduced graphene dispersion, it improved mechanical and barrier properties due to increased crosslink density. Oxygen permeability was reduced by up to 36% at 3 phr of GNP content with silane. This research proves that the mixing order and the type of mixing equipment are crucial in determining the final performance of rubber composites, as they significantly influence the dispersion and localization of fillers.Highlights NR/CIIR/GNP nanocomposites were prepared by different methods and evaluated. Adding NR/GNP to CIIR led to more presence of GNP in NR and lower permeability. By adding CIIR/GNP to NR, GNP were placed more at interface, modulus improved. Mixing in an internal mixer improved GNP dispersion compared to a two‐roll mill. Silane improved mechanical and barrier properties of NR/CIIR/GNP nanocomposite.

Dispersion and Stability Behaviour of Graphene and MWCNT Based Nano-Lubricant for Vapour Compression Refrigeration (VCR) System

Incorporating nanoparticles into oil compressors marks a significant advancement in scientific research. It has been widely demonstrated that the inclusion of nanoparticles can markedly improve the system's efficiency by reducing energy consumption, decreasing evaporator temperatures, and increasing condenser temperatures. Nanoparticles made of carbon, including those of metal, metal oxide, and metal hybrids, are particularly valued for their superior properties and are deemed to have considerable potential for achievements. This study focuses on examining the stability of graphene and multi-walled carbon nanotubes (MWCNT) in polyolester (POE) oil as a precursor to replacing conventional lubricating oil in refrigeration systems separately. Graphene nano-lubricants were tested at concentrations ranging from 0.1 to 0.3 g/L with the selected surfactant, cetyltrimethylammonium bromide (CTAB), in a 1:1 ratio, while MWCNT nano-lubricants were tested from 0.5 to 0.7 g/L. All samples were prepared using a two-step method that involved magnetic stirring at 1250 rpm for 45 minutes, followed by ultrasonication for 30 minutes. The samples underwent evaluation through three methods of observation. Initial visual observation was conducted immediately after production, then after a 24-hour settling period, and finally, after seven days, the three most optimal samples were identified. For MWCNT, an additional stability test was necessitated due to the high concentration levels, making it challenging to determine the three most stable concentrations. The UV-VIS spectrophotometer played a crucial role in analyzing the stability of the samples, providing data that enabled more precise results. The absorption peak at a wavelength of 294 nm reached its highest absorption value of 0.892 (a.u.) at a concentration of 0.2 g/L. In the case of MWCNT, after testing all samples, concentrations of 0.5, 0.55, and 0.65 g/L were identified as the best options based on peak absorption at different wavelengths, with their peaks at 4.87, 4.045, and 4.116 (a.u.), respectively. The Zeta Potential Analyzer confirmed the stability of these concentrations, indicating a moderate stability with values around -37.4 mV. This level of stability was also observed in MWCNT samples, with the three chosen concentrations showing excellent stability at 88.4, -84.9, and -137 mV, respectively. Among all tested nano-lubricant samples, those with concentrations of 0.2 g/L and 0.65 g/L for Graphene/CTAB/POE and MWCNT/POE, respectively, demonstrated the highest stability and optimum performance. This suggests that these concentrations have the potential to serve as replacements for POE oil in refrigeration systems.

Graphene reinforced magnesium metal matrix composites by infiltrating coated-graphene preform with melt

Graphene’s exceptional mechanical, electrical, and thermal conductivity capabilities make it an ideal reinforcement for metal matrix composites. However, graphene is hard to be dispersed in the melt metal due to its high surface energy, non-wetting nature, and strong van der Waals interactions between graphene sheets, which weaken the reinforcing efficiency of composites. A novel process by infiltrating the coated-graphene preform with melt magnesium was proposed to improve the dispersion of graphene in the magnesium matrix. Graphene preforms with oriented pores were prepared by a directional freeze-drying method. Magnesium oxide coatings were deposited on the surface of graphene inside the graphene preform using the evaporation of magnesium atoms to enhance the strength as well as the wettability between the preform and magnesium matrix. Magnesium matrix composites were fabricated by liquid-solid pressure infiltrating coated-graphene preform with molten magnesium. The microstructure of graphene preforms and composites and mechanical properties of the composites were characterized. The results show that graphene is uniformly dispersed in the matrix and presents a reticular structure, and the hardness, elastic modulus, and compressive strength of the composite were improved apparently compared to the matrix. This study suggests that the method of preparing composites by infiltration provides a novel strategy for fabricating nano-material reinforced magnesium matrix composites.

Adsorption, Aggregation, and Application Properties of Green Pluronic Aliphatic Alcohol Ether Carboxylic Acids and Nonionic/Amphoteric Surfactants in Water.

In the realm of colloid and interface science, new types of green surfactants, including anionic Pluronic alcohol ether carboxylate (AEC), branched alkyl glucoside (IG), and zwitterionic coconut oil amide propyl betaine (CAB), have been identified and merit further exploration. AEC, characterized by its inclusion of 5 EO and 3.5 PO units, was synthesized, and its behavior in aqueous solutions with IG and CAB was meticulously examined. Their performance in applications such as foam generation, wetting, and the dispersion and stabilization of graphene was also evaluated. At αAE5P3C = 0.5, AE5P3C/CAB exhibited superior surface and interfacial properties compared to AE5P3C/IG. In these hybrid systems, the self-assembly of micelles is predominantly influenced by hydrogen bonding, electrostatic interactions, and hydrophobic forces. Kinetic analysis further confirmed that the driving force for micelle formation in these hybrid systems is enthalpy, with the adsorption process involving a mixed diffusion-kinetic adsorption mechanism. AE5P3C/CAB demonstrated enhanced foaming ability, foam stability, and wetting properties compared to AE5P3C/IG. Intriguingly, the optimal dispersion and stabilization of graphene were achieved with AE5P3C/IG at αAE5P3C = 0.2, providing a foundational basis for its potential application in graphene-based systems. A thorough examination of the synergistic mechanisms and application potential of these three distinct surfactants in aqueous solutions was presented, taking into account various charged ions and the specific hydrophilic and hydrophobic groups of EO and PO. This study not only provides fundamental insights into their intrinsic properties but also offers a fresh perspective for the ongoing exploration of green surfactants.

Graphene Coating and its Effect on Performance of Box Type Solar Cooker: An Experimental Investigation

Background: Solar cookers have been the subject of several theoretical and empirical investigations, with numerous modifications attempted to increase efficiency and security. Solar cookers need much sophisticated research and enhancement work to function better. A thorough grasp of the application of graphene in box-type solar cooking systems is crucial for both solar energy and graphene. Objective: To improve the performance of box-type solar cookers, this patent research aims to offer an experimental investigation and insightful information on of applying graphene coating to the absorber plate and its derivative. Materials and Methods: To ensure equal dispersion of graphene into the black paint, three samples containing (1, 3, and 5wt%) of graphene embedded with the paint were produced with 1mm, 3mm, and 5mm thickness of the coating and stirred at 400 rpm for two hours using a magnetic stirrer. Xray diffraction and scanning electron microscopy have been studied to comprehend the influence of graphene nanoparticles on the surface morphology of the coated absorber panel. Performance evaluations of the box-type solar cookers were conducted with and without a graphene coating on the absorber plate, and data has been recorded for each case. Results: The results of patent research show that the absorber plate with (1, 3, and 5wt.%) of graphene embedded with black paint 1mm, 3mm, and 5mm thickness coating has a maximum thermal efficiency of 41.48% with 97.08 W cooking power, 46% with 109.35 W cooking power, and 49% with 114.77 W cooking power for the average solar irradiation is 978 W/m2. Discussion: It was determined that the cooking power (P), the first figure of merit (F1), and the second figure of merit (F2) were all satisfactorily achieved. Embedding black paint into graphene coating has been shown to significantly influence the heat transmission and thermal performance enhancement of box-type solar cookers, as demonstrated by the findings of X-ray diffraction and Scanning Electron Microscopy analysis. Conclusion: The current research makes it abundantly evident that the incorporation of graphene into the absorber plate of a box-type solar cooker, together with the application of a black paint coating, leads to increased heat transfer rates, which in turn provides an increase in cooking power. Because of this, graphene is an attractive nanomaterial that has the potential to improve the performance of box-type solar cookers, which is the novelty of this research work.

Synthesis of perylene‐PEO hyperdispersants for aqueous graphene dispersion

AbstractGraphene, with excellent thermal conductivity, electrical and corrosion shielding performance has great application potential in the fields of heat dissipation coating, conductive agent and anticorrosion composite coatings. However, due to its large specific surface area, resulting strong aggregation behavior limits its application. Herein, the hyperdispersants with perylene anchoring groups are synthesized through the amidation coupling reaction between diacid anhydride and polyetheramine. The branching degree and length of hydrophilic chains on hyperdispersant are revealed to be the very important factors to affect the dispersion stability of aqueous graphene dispersion. The hyperdispersant with a single hydrophilic chain and the molecular weight 2000 of polyetheramine has the excellent dispersal activity discovered by Rheology, particle size distribution and Raman measurements. The possible mechanism is the strongest anchoring effect of perylene on graphene surface and thus achieving in best effective spatial exclusion stabilization effect of hydrophilic chains.

Influence of different introduction methods of graphene on the mechanical properties and cutting performance of Al2O3/TiB2 ceramic tool materials

This study investigated the effects of incorporating graphene-coated alumina (Al2O3@G) nanoparticles and graphene oxide (GO) on the microstructure, mechanical properties, and cutting performance of Al2O3/TiB2 matrix ceramic tool materials. Compared to the addition of GO, the inclusion of Al2O3@G enhanced the dispersion of graphene in the ceramic tool materials and alleviated defects such as pores caused by graphene agglomeration. Additionally, during sintering, uniformly distributed graphene interwove to form a three-dimensional grid structure owing to grain growth and pore disappearance, increasing the contact area and interface bonding strength between the graphene and the matrix. Based on the results of the microstructure observation and analysis, the favorable interfacial strength not only facilitated load transfer from the ceramic matrix to graphene but also triggered the fracture mechanism of graphene, consuming more fracture energy than the traditional toughening mechanism. The hardness, flexural strength, and fracture toughness of the obtained ATB-G@3.0 ceramic tool material with 3.0 vol% Al2O3@G were measured at 19.52 GPa, 1063.52 MPa, and 9.16 MPa m1/2, respectively, which were 16.82 %, 27.92 %, and 26.87 % higher than those of the ATB-G3.0 ceramic tool material with 3.0 vol% GO. Compared with the ATB-G3.0 ceramic tool, the ATB-G@3.0 ceramic tool displayed superior cutting performance and longer service life when machining hardened steel 40Cr. Furthermore, the addition of Al2O3@G effectively reduced the cutting force, friction coefficient, and cutting temperature of the ceramic tools and enabled the workpiece to achieve better surface processing quality after cutting.

An environmentally sustainable ultrasonic-assisted exfoliation approach to graphene and its nanocompositing with polyaniline for supercapacitor applications

In the present work, a green high-yielding method for the preparation of graphene is introduced via ultrasonic-assisted liquid phase exfoliation (LPE) of graphite in a green solvent medium, since the common preparation method of graphene via graphite oxide is hazardous. A high concentration of 3.2 mg/ml graphene is achieved here in a comparatively short duration of 3 h ultrasonication. By using a mixed solvents strategy (acetophenone and isopropyl alcohol, 1:19 V/V), surface energy requirements needed for the exfoliation of graphite are satisfied here with acetophenone, where isopropyl alcohol further facilitated the exfoliation via non-conventional CH-π and OH-π interactions. Turbostratic graphene in high-yield (16 %) in a simple means of ultrasonic assisted LPE is the added attraction of the present procedure. The less-defective structure of graphene, its few-layered turbostratic nature, and edge functionalization of the sheets are evident from the material characterization via Raman spectroscopy, XRD, TEM-SAED, and XPS analyses. Here, we report a combination of the attractive conducting polymer polyaniline (PANI) with the as-prepared graphene for supercapacitor applications, where the PANI/graphene nanocomposites with different aniline concentrations (PANI1.125/G, PANI4.5/G, and PANI9/G) have been prepared via in-situ polymerization of aniline in the graphene dispersion. The structure and morphology of the nanocomposites are investigated using different characterization techniques which revealed that the molecular structure of the PANI is retained in the nanocomposites even with a strong interaction with graphene. FESEM and TEM images revealed the good coverage of graphene sheets with PANI that limit the volume change of PANI during the repeated charge-discharge processes. Electrochemical studies showed that PANI4.5/G has the highest specific capacitance of 126.16 mF/cm2 at a current density of 1 mA/cm2, resulting from the perfect combination of the pseudocapacitance behavior of the PANI along with the electrical double layer capacitance of graphene. A symmetric supercapacitor device is also fabricated with PANI4.5/G, which showed the highest areal capacitance of 116.38 mF/cm2 similar to that with three-electrode studies and also good cycling stability with 87 % capacitance retention in the specific capacitance after 6000 cycles. It also exhibited an energy density of 16 µWh/cm2 (0.29 Wh/kg) and a power density of 3.99 mW/cm2 (72.72 W/kg).

Effects of graphene nano particles on interfacial microstructure and mechanical properties of Al7150/B4C hybrid nanocomposite fabricated by novel double ultrasonic two stage stir casting technique

In the present research, an Al7150 alloys-based hybrid nanocomposite was fabricated by incorporating boron carbide and graphene nanoparticles through a novel fabrication method of double ultrasonic two-stage stir casting. Initially, the Al-B4C nanocomposite was optimized based on better microstructural and mechanical properties, and then a hybrid nanocomposite was prepared by incorporating graphene nanoparticles into the optimized Al-B4C nanocomposite. Homogeneous dispersion of graphene and boron carbide nanoparticles in Al7150 matrix was successfully achieved due to the double ultrasonic effect analyzed by Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM) analysis. Significant dispersion of nanoreinforcements with enhanced interfacial bonding and dislocation strengthening improved the microstructural and mechanical properties of the Orovan reinforced hybrid nanocomposite. The Vickers microhardness and ultimate tensile strength were improved by 19 % and 47 %, respectively, for the optimized Al-B4C nanocomposite compared to base metal. However, the Vickers microhardness and ultimate tensile strength were significantly improved by 36 % and 57 %, respectively, for the optimized hybrid nanocomposite compared to the base material (BM). The hard AlB2, Al3BC and Al4C3 phases are formed due to the reaction between the matrix and reinforcement during solidification and act as reinforcement within the matrix and resist dislocation movements, resulting in a significant improvement in the mechanical properties of the nanocomposite. Fractography analysis by SEM also confirms the enhanced bonding of graphene nanoparticles as it deforms/slips during fracture and supports the effect of double ultrasonication on the tearing of boron carbide nanoparticles.

Strong and tough graphene/PVC composites with well dispersed graphene via dropwise coagulation and melt blending methods

Toward strong and tough reduced graphene oxide (rGO)/poly(vinyl chloride) (PVC) composites, GO/PVC particles with well dispersed GO are prepared via dropwise coagulation using homogenous GO/PVC dispersion. Then, rGO/PVC composite materials are obtained by reducing GO with VC and melt blending. With low GO content by weight (GO:PVC = 0.2:100), the rGO/PVC composite's tensile strength, elongation at break, Young's modulus and toughness are increased by 100.1 %, 102.4 %, 179.1 % and 432.3 %, respectively. Further, the rGO/PVC particles with high GO content (GO:PVC = 1:100) are applied as functional masterbatch for commercial PVC-based wood plastic composite (WPC). With only 0.07 wt% GO (relative to WPC), the tensile strength, elongation at break, Young's modulus and toughness of WPC are enhanced by 62.4 %, 75.4 %, 57.2 % and 236.3 %, respectively. This study provides a simple approach to obtain strong and tough graphene/PVC composites toward industrial application.

Investigation on the loading rate dependence of electromechanical properties of graphene-cement composites under compressive loading

In this paper, the dependence of the electromechanical properties of graphene-cement composites on the loading rate is studied by combining experiment and theory. The graphene-cement composites are prepared using a wet dispersion technique combined with surfactant assist and ultrasonication treatment. Both monotonic and cyclic compressive experiments with different loading rates are conducted on the graphene-cement composites with different graphene contents to measure their mechanical, electrical and piezoresistive properties. The optimum dosage of graphene in cement matrix is about 0.05 wt%, which can increase the compressive strength by 35.7 % and 34.1 %, and decrease the electrical resistivity to 1.43 and 3.48 × 105 Ω•cm, respectively, after 14 and 28 d curing periods. The uniform dispersion of graphene with less layers endows the graphene-cement composites with very low percolation threshold of electrical conductivity (0.007 wt%), stable piezoresistive response, and good reproducibility. Furthermore, the mechanism of the loading rate on the strain sensing behavior is discussed, and a rate dependent theoretical model of resistance change is proposed to quantitatively predict the electromechanical responses. This study provides guidelines for the fabrication of highly strain-sensitive graphene-cement composites and the rate-dependent evaluation of their electromechanical properties in the fields of intelligent construction.

Thermal conductivity of epoxy/multilayered graphene composites prepared with different curing agents

Epoxy/multilayer graphene (ML-graphene) composites were prepared using different curing agents to control the graphene dispersion by changing the curing reactivity. With increasing initial reactivity, the aggregation size of the ML-graphene decreased and their thermal conductivity increased. In particular, the thermal conductivity of the composite prepared with p-phenylenediamine showed a maximum value of 1.46 W/(m·K) at 25 wt% ML-graphene loading because of the highest initial curing reactivity. The application of a magnetic field led to graphene alignment along the applied field, resulting in two times higher thermal conductivity than that of the corresponding system without magnetic field. The relationship between the interfacial affinity for epoxy/graphene and thermal conductivity was also investigated. As a result, resulting in a biphenyl epoxy composite showed higher thermal conductivity (6.17 W/(m·K)) than that of the bisphenol-A epoxy composite. This is derived that the π-conjugated and planar structure of biphenyl epoxy can easily interact with the surface of graphene.

Effect and mechanisms of type, content, and dispersion method of flash graphene on the rheological behaviors of fresh cement pastes

Flash Joule heating provides a facile, low-carbon, and cost-effective method for upscale graphene production, benefiting the application of graphene in modifying cement-based materials. Understanding the effect and mechanisms of flash graphene (FG) type, content, and dispersion method on the rheological behaviors of cement-based materials is essential for designing and controlling cement-based materials in different application scenarios. Therefore, this study explored the rheological behaviors of cement pastes with 2 different types of flash graphene at 4 different content levels (namely 0.1 wt%, 0.2 wt%, 0.3 wt%, and 0.4 wt% of cement mass) using 3 different dispersion methods (namely water reducer dispersion with ultrasonic treatment, dry mixing with water reducer, and mechanical dispersion with water reducer). The results indicated that the addition of FG generally increases the yield stress and plastic viscosity of fresh cement pastes. The water reducer dispersion with ultrasonic treatment and nano-boron doping shows a good effect in dispersing FG. The influence mechanisms of FG on rheological behaviors of fresh cement pastes are a competition between exert replacement, agglomeration, lubrication, and adsorption effects.

Enhancing tetrafullerene based photosensors and photovoltaic cells by graphene oxide doping

This study explores the postulated potential of tetrafullerene as a charge transport material when combined with dispersed graphene oxide (GO), over concerns about fullerene’s limited performance in similar devices. Incorporating GO is expected to augment carrier concentration, increase surface area, and reduce operating voltages. Devices fabricated with p-Si/tetrafullerene with varying GO concentration exhibit notable enhancements in both dark and illuminated characteristics. The results demonstrate improved electron concentration and transport, leading to enhanced rectification ratios, ideality factors, and interface state densities across a broad bias and illumination range. Notably, devices doped with 0.2GO exhibit the most promising electrical and photoresponse characteristics, showcasing potential for applications in photosensing and photovoltaics.

Fabrication and characterization of rippled graphene/LDPE composites with enhanced hydrogen barrier properties

Hydrogen plays a pivotal role as a sustainable energy carrier, but the cost-effective and efficient production of gas barrier materials for hydrogen storage still poses a considerable challenge. In this research, we investigate the hydrogen barrier properties of nanocomposites based on low-density polyethylene (LDPE) filled with varying concentrations (0–5 wt%) of rippled graphene. The low-density polyethylene rippled graphene (LPRG) nanocomposites were prepared by drop-casting a suspension of graphene with LDPE dissolved in Toluene, which resulted in a uniform dispersion of rippled graphene within the LDPE matrix. Mechanical testing revealed notable improvements in tensile strength (+40%) and Young's modulus (+120%), confirming the reinforcing effect of rippled graphene in the polymer matrix. Results from the thermogravimetric analysis showed that the addition of rippled graphene significantly increased the thermal stability of the material, reporting an increase of 77 °C in the thermal degradation temperature at a nanofiller loading of 1 wt%. Additionally, the incorporation of rippled graphene in the composite improved the thermal conductivity by 161 %. Moreover, it resulted in an electrically percolated network at a critical nanofiller loading of 1 wt%, contributing to enhanced electrostatic discharge safety. Finally, gas permeability tests unveiled a 50% reduction in hydrogen permeability of LPRG with graphene content of 5 wt% compared to pristine LDPE, making graphene/LDPE composites a superior choice for sustainable and efficient hydrogen storage applications.

Paracetamol sensing with a flexible graphene paper electrode modified with MnCo2O4

AbstractBACKGROUNDThe design of new‐generation flexible sensors for medical applications has gained considerable interest in the research community in recent past years. Herein, a free‐standing flexible electrode was developed for the electrochemical determination of Paracetamol (PC). This graphene‐based paper electrode was prepared using graphene and MnCo2O4 dispersion with a mold‐casting method followed by chemical reduction. The morphology and structure of our flexible paper electrode (MnCo2O4/GP) were characterized by scanning electron microscopy, energy‐dispersive, X‐ray diffraction, X‐ray photoelectron, and Raman spectroscopy.RESULTSThe as‐prepared flexible MnCo2O4/GP showed outstanding sensing performance for PC, as compared to GP, due to the excellent electrochemical properties of MnCo2O4. The proposed sensor exhibited a wide linear range of 4.64–1000 μM for electrochemical determination of PC with a low detection limit of 1.39 μM. Furthermore, MnCo2O4/GP was successfully applied for PC syrup and tablets with good accuracy results.CONCLUSIONSFor the first time, the present study demonstrated the fabrication and utilization of MnCo2O4‐modified graphene paper to develop a flexible and sensitive electrode for monitoring PC. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Optimization of Cyanide-Free Composite Electrodeposition Based on π-π Interactions Preparation of Silver-Graphene Composite Coatings for Electrical Contact Materials.

With the rapid development of industrial automation and power electronics, the requirements for electrical contact materials are increasing. However, traditional electrical contact materials encountered significant bottlenecks in terms of performance enhancement and production environmental friendliness. Therefore, this paper proposes a new material design idea that utilizes π-π interactions between graphene and compounds with conjugated structures in order to achieve uniform dispersion of graphene in the metal matrix and thus enhance the performance of composites. Based on this design idea, we used nicotinic acid, which has a conjugated structure and is safe, as the complexing agent, and successfully prepared high-quality silver-graphene (Ag-G) composite coatings with graphene uniformly dispersed in the metal matrix on copper substrates by composite electrodeposition technique. Subsequently, the mechanical properties of composite coatings were investigated by hardness test and X-ray diffractometer, and the tribological properties of the composite coatings and the comprehensive performance under the current carrying conditions were systematically evaluated by using friction and wear tester and load key life tester. The results show that the Ag-G composite coatings have significant advantages in mechanical, tribological, and current carrying conditions. This result not only verifies the feasibility of the design idea of the material, but also provides a new direction for the research and development of electrical contact materials.

Microscopic insights into the aggregation dynamics behavior and tribological properties of graphene

The stable dispersion mechanism of graphene nanoparticles in solid-liquid two-phase lubrication systems still lacks in-depth insights into the dynamic aggregation process at the microscale. Herein, the effects of size difference and defect degree on the agglomeration dynamics behavior and tribological properties of graphene nanosheets were revealed by aggregation, pull-out, and friction molecular dynamics simulations. The results showed that for suspended graphene smaller than 100 nm, the increase in size and defect degree effectively improved the dispersion stability of nanosheets in base oil. Attributed to the rise in size improved solid-liquid chemical affinity and promoted out-of-plane deformation of nanosheets to enhance the steric hindrance effect. The increase in defect degree induced spontaneous wrinkling of nanosheets, leading to enhanced interlayer sliding resistance and thus inhibiting agglomeration behavior. Meanwhile, the rise in nanosheet size and degree of defects sufficiently bear the normal load, effectively avoiding the direct contact of asperities and thus improving the wear and temperature rise at the friction interface. However, friction-induced defective graphene curled to form a “carbon nanotube-like” structure, which reduced the oil film strength and led to deterioration of lubrication performance. The research results will provide certain microscale insights into the dispersion and friction of graphene in base oil.

Completely Monodisperse Graphene Dispersions Imparting Film of High Specific Capacitance

Graphene has emerged as a remarkable material with diverse applications in the field of optoelectronics and energy storage. However, the challenge lies in producing high-quality graphene via liquid phase methods that can match the optoelectronic properties achieved through expensive techniques like chemical vapor deposition (CVD) or micromechanical cleaving. Existing liquid phase methods suffer from issues such as graphene oxidation during production, layer number dispersion, and small flake size, which significantly compromise the overall quality of the material and its potential applications.We demonstrate the synthesis of completely layer number-monodisperse graphene dispersions using anodic electrochemical exfoliation with exceptional optoelectronic properties comparable to CVD-derived graphene. A notable highlight of our research is the high specific capacitance of the film formed from the electrochemically exfoliated graphene dispersions (259- 666 F g-1), which is highly promising for capacitive energy storage applications. We have successfully addressed the difficulties related to oxidation and the uneven distribution of layers, achieving large flake sizes. This progress was achieved by employing a tailored synthesis method maneuvered through electrochemical characterizations and precise management of experimental variables during the intercalation, exfoliation, and further processing steps. Thus, this research contributes significantly to the ongoing advancements in graphene synthesis and graphite intercalation science.