Graphene Fillers Research Articles

Effect of nano-Cu-loaded graphene fillers on tribological properties of PTFE based composite coatings

The Polytetrafluoroethylene(PTFE)-based composite coating has been widely used in the tribology field due to the high strength of graphene(GNS) and the self-lubricating property of PTFE. However, the weak interfacial bonding between GNS and PTFE inhibits the tribological performance of PTFE-based composite coatings. In this study, the composite coating is in situ fabricated by loading Cu nanoparticles on the GNS surface, and the microstructure, bonding, friction, and wear properties of the composite coating were investigated. The results showed that the interfacial bond strength, friction, and wear properties of Cu@GNS-PTFE coating are higher than those of pure PTFE and GNS-PTFE coating. Compared with the PTFE coating, the Cu@GNS-PTFE coating with the optimal ratio(5%) can increase the bond strength by 24.6% and reduce the wear rate by 42.2%. The lubrication mechanism of the Cu@GNS-PTFE coating is the Cu nanoparticle can increase the interfacial bonding property of GNS and PTFE from both mechanical interlocking and chemical activity, which can promote the synergistic lubrication of GNS and PTFE, and provide a theoretical basis for the further application of PTFE and GNS.

Investigation of mixed matrix membranes of graphene and acid‐treated graphene fillers in cellulose acetate and polyetherimide polymers for CO2 separation from biogas

AbstractGas separation membranes are crucial for upgrading biogas by separating carbon dioxide (CO2) from biogas, thereby enhancing its calorific value and reducing greenhouse gas emissions. This study aims to improve CO2/CH4 separation using mixed‐matrix membranes (MMMs) by incorporating graphene (Gr) and acid‐treated graphene (AGr) fillers in a cellulose acetate (CA) polymer matrix. Similarly, polyetherimide (PEI) MMMs were also prepared with Gr and AGr fillers to draw a comparison. Various characterization techniques, including Fourier transform infrared spectroscopy, differential scanning calorimetry, field emission scanning electron microscopy, Raman spectroscopy, and X‐ray diffraction, were employed to investigate the structural and morphological properties of the membranes and fillers. Gas permeation tests using a model biogas mixture (40% CO2 and 60% CH4) revealed that the 0.1%AGr/CA membrane achieved the highest CO2 permeability of 43 Barrers, which is approximately 307% more than that of the pure CA membrane, and showed a CO2/CH4 selectivity of 14.80. The 0.5%Gr/PEI membrane demonstrated the best performance among PEI‐based MMMs, with a CO2 permeability of 17.48 Barrers and a CO2/CH4 selectivity of 8.96. These results indicate that the incorporation of Gr and AGr significantly enhances the gas separation performance over pure CA and PEI membranes.Highlights Graphene (G) and acid‐treated Gr‐based cellulose acetate (CA) and polyetherimide (PEI) mixed‐matrix membranes (MMMs) were fabricated. Model biogas was used for testing CO2 and CH4 gas permeation. The 0.1% AGr/CA MMM showed 307% higher CO2 permeability than pure CA. The 0.5% Gr/PEI MMM showed 435% higher CO2 permeabilit than pure PEI. Structural properties were confirmed by Fourier transform infrared spectroscopy, differential scanning calorimetry, field emission scanning electron microscopy, Raman, and X‐ray diffraction.

Preparation of the fluorinated graphene/epoxy resin anti-corrosion composite coating

In order to enhance the corrosion resistance of epoxy resin (EP) coating system, we put forward a facile approach to prepare hydrophobic fluorinated graphene (FG) filler for the EP coating by one-pot hydrothermal reaction in this work. Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle measuring instrument and scanning electron microscopy (SEM) were employed for the FG characterization. The SEM images of fracture morphology revealed that FG uniformly dispersed in epoxy resin matrix. Additionally, the excellent water resistance and the lower coefficient of friction of FG/EP coating was confirmed through the water absorption test and friction and wear test machine. The electrochemical impedance spectroscopy (EIS) demonstrated that the impedance value at the low frequency (|Z|0.01Hz) of 0.50 wt% FG/EP was 3.49 × 107 Ω·cm2 after being immersed in 3.5 wt% NaCl solution for 60 days, which was about 2 orders of magnitude higher than that of the pure EP coating (4.74 × 105 Ω·cm2). The 0.50 wt% FG/EP coating exhibited the superior anti-corrosion performance due to the FG with the two-dimensional sheet structure, uniform dispersion and hydrophobicity properties.

Design of epoxy composites via molecular orbital modulation and enhanced π-πF interactions achieving synchronous improvement of electrical and mechanical performance

The stacked aromatic rings in bisphenol A epoxy resins provide good mechanical properties and thermal stability while leading to the transport of conjugated delocalized electrons, which dramatically affects the insulation properties of the material. This contradiction leads to performance bottlenecks in epoxy-based encapsulation materials, further limiting the development of high-voltage semiconductor devices. In this study, fluorophenyl-modified epoxy monomers (FPMEPs) are designed to enrich the intermolecular interactions in an aromatic system while inhibiting the charge transport process, thereby solving the contradiction between the electrical and mechanical properties. Firstly, FPMEP with high insulation properties was designed by theoretical calculations and then synthesized by highly selective click chemistry. The fluorophenyl modulates the molecular orbitals of epoxy monomers and acts as a deep trap to inhibit charge injection and transport processes. Further, the π-πF stacking between the aromatic system and fluorophenyl enhances the interaction of the matrix molecules and solves the dispersion problem of fluorinated graphene (FG) fillers. The FPMEP/FG composites thus exhibit a considerable improvement in electrical and mechanical properties (breakdown strength of 39.8 kV/mm, dielectric loss of 0.011@50 Hz, tensile strength of 68.8 MPa, and adhesive strength of 2.15 MPa), and demonstrate good water repellency and aging durability. This matrix-filler synergistic modification strategy provides new insights into the design of insulation material.

Flexible poly (vinylidene fluoride) composite with magnetite-modified graphene: Electromagnetic shielding in X-band

Electromagnetic pollution, or electromagnetic interference (EMI), is a phenomenon that has arisen due to the fast spread of electronic gadgets. To overcome EMI problem, polymer-based composites have sparked considerable attention among researchers owing to their superior qualities. Hence, this work utilizes magnetite-modified graphene (MMG) filler with polyvinylidene fluoride (PVDF) polymer to form polymer composites in various proportions ranging from 2 to 10 wt% to study the EM properties in the X-band. It was observed that the sample composite having a MMG filler content of 10 wt% possesses a relatively higher electrical conductivity of 0.65 S/cm as compared to the other prepared composites in this research work. The same sample composite also attained a total shielding efficacy of 53.04 dB at a thickness of 3 mm. Moreover, it was observed that the filler has improved the material's thermal stability and microwave absorption capacity, making it a high-efficiency EMI shielding material appropriate for usage in the electronic and aviation industries.

Structural design of two types of composites with high resistance to atomic oxygen attack based on polyimide matrices: a molecular dynamics simulation study

Because of their exceptional properties, polyimide (PI) polymers are widely used in various types of spacecraft. However, in low Earth orbit, spacecraft using these polymers are susceptible to atomic oxygen (AO) erosion, which will cause them to lose their original performance. Covering the PI surface with a protective coating and adding fillers to the PI matrix are two traditional methods to improve the AO erosion resistance of PI. However, a single protective method does not provide a good protective effect and does not necessarily balance the relationship between the AO resistance of the composites and other properties, such as mechanical properties. The structural design of composites can perfectly solve such problems. Therefore, two kinds of AO-resistant materials based on the PI matrix are designed in this paper, one is a hybrid-filled composite with nano-silica filler and graphene filler, and the other is a double-layer coated composite based on the structural design of a traditional bulletproof vest. And the AO incidence simulation of these two types of materials was carried out using ReaxFF-based MD simulation. The results show that the mixed filling of graphene and nano-silica not only greatly improves the AO resistance of the PI matrix, but also greatly improves the tensile mechanical properties of the matrix by adjusting the appropriate mixing ratio. The structure of PI-Gr-SiO2 (The structures are PI, Gr and SiO2 from bottom up, respectively. SiO2 will be the first to take the impact of AO.) possesses excellent resistance to AO erosion, and at the end of 64 ps of AO erosion, the PI matrix did not suffer any damage. This paper provides a new idea of material structure design using the MD method, which provides a new approach to improve the AO erosion resistance of PI and is expected to design new composites adapted to a variety of extreme environments in the future.

Experimental and theoretical analysis on the thermomechanical properties of functionally graded graphene nanoplatelet reinforced cement composites

Graphene reinforced cement composites (GRCCs) have attracted great attention due to their excellent mechanical and physical properties. Instead of uniform distribution, the functionally graded distribution of graphene fillers can effectively utilize the mechanical and physical properties of the reinforcements while reducing cost. This paper is the first attempt to combine experimental analysis and theoretical modelling to investigate the thermomechanical properties of functionally graded graphene nanoplatelet (GNP) reinforced cement composites (FG-GNPRCCs). Samples with uniform (profile H) and functionally graded (profiles X, O and A) distribution of GNPs were prepared and tested. Among all the FG distribution patterns as involved, profile X exhibited the most pronounced enhancement. Compared to the uniform distribution at room temperature, the loss factor and storage modulus of profile X increased by 19.3 % and 19.5 %, respectively. Based on the effective medium theory (EMT) and Mori-Tanaka (MT) model, a parallel triple-inclusion model was developed to predict the thermal conductivity of GNPRCCs. The effects of coated GNP, agglomeration and the attributes of pores (i.e., size, shape and porosity) on the thermomechanical properties of the composites were considered. Dynamic mechanical analysis revealed that profile X had the best energy dissipation and the extent of inelastic deformation within the temperature range from −50 °C to 70 °C. In contrast, profile A is beneficial for scenarios that desire a gradual transition and controlled stress along a certain direction.

Influence of nano graphene filler on hardness, impact strength and density of glass epoxy composites

AbstractThis study investigates the effects of graphene reinforcement on the hardness and impact strength of glass epoxy composites. Four different materials were examined: pure epoxy (EP), glass epoxy (GE), glass epoxy with 1 wt.% graphene (GE1), and glass epoxy with 2 wt.% graphene (GE2). The results show that the incorporation of graphene significantly enhances the hardness of the composites. Pure epoxy (EP) exhibited a Shore D hardness of 60 and an impact strength of 0.09 J/m2. The glass epoxy (GE) showed a reduction in hardness to 56 but an increased impact strength of 0.15 J/m2 due to the inclusion of 33 wt.% glass fiber. Further addition of graphene in GE1 and GE2 led to notable improvements in hardness, reaching 68 and 74 Shore D, respectively. However, the impact strength displayed a decrease with the inclusion of graphene, with GE1 and GE2 showing values of 0.13 and 0.11 J/m2, respectively. When transitioning from pure epoxy (EP) to glass epoxy (GE), there is a 6.67% decrease in hardness, while the impact strength increases by 66.67%. Introducing 1 wt.% of graphene to the glass epoxy (GE1) results in a 21.43% increase in hardness but a 13.33% decrease in impact strength. Further adding 2 wt.% of graphene (GE2) leads to an additional 8.82% increase in hardness, though the impact strength decreases by 15.38%. X‐ray diffraction (XRD) analysis has revealed nano graphene presence and distribution, while fractography has revealed its effectiveness in enhancing interfacial adhesion and toughening mechanisms. Furthermore, XRD identifies potential changes in crystallinity or phase composition induced by nano graphene incorporation, further elucidating the composite's structure and properties. The study highlights the novel and significant trade‐offs encountered in optimizing the mechanical properties of epoxy‐based composites by incorporating graphene and glass fiber.

Exploring the role of graphene filler on mechanical properties of cotton/viscose hybrid composites

Exploring the role of graphene filler on mechanical properties of cotton/viscose hybrid composites

Copper-Graphene Composite (CGC) Conductors: Synthesis, Microstructure, and Electrical Performance.

Improving the electrical performance of copper, the most widely used electrical conductor in the world is of vital importance to the progress of key technologies, including electric vehicles, portable devices, renewable energy, and power grids. Copper-graphene composite (CGC) stands out as the most promising candidate for high-performance electrical conductor applications. This can be attributed to the superior properties of graphene fillers embedded in CGC, including excellent electrical and thermal conductivity, corrosion resistance, and high mechanical strength. This review highlights the recent progress of CGC conductors, including their fabrication processes, electrical performances, mechanisms of copper-graphene interplay, and potential applications.

Effect of composite processing technique on tribological properties of 3D printed PLA-graphene composites

The present study investigates the effect of processing method on the tribological behavior of 3D-printed Polylactic acid (PLA)/graphene composite samples. Two different methods, electrochemical (EG) and chemical exfoliation (HG) of graphite, are used to prepare graphene fillers. The PLA/graphene composites are processed using two different solvents, chloroform (CHCl3) and dimethylformamide (DMF). Various PLA/graphene composite combinations are prepared by varying filler type, solvent type, and filler loading. The 3D printable composite feedstock filaments are prepared using a single-screw Desktop extruder. Fused Filament Fabrication (FFF) is employed to print samples for tribological tests. The coefficient of friction (COF) and wear rate are evaluated using the ball-on-flat reciprocating sliding wear tests. It was observed that COF was reduced by 76 % with 0.5 wt% loading of filler. The wear mechanism has changed from predominant abrasive wear in neat PLA to adhesive wear for composites. Further, the interactive effect of process parameters is studied using ANOVA. The results indicate that filler type and filler loading significantly influence weight loss. The solvent type has a minimum effect.

Suitably Incorporated Hydrophobic, Redox-Active Drug in Poly Lactic Acid-Graphene Nanoplatelet Composite Generates 3D-Printed Medicinal Patch for Electrostimulatory Therapeutics.

Polymer carbon composites have been reported for improved mechanical, thermal and electrical properties to provide reduced side effect by 3D printing personalized biomedical drug delivery devices. But control on homogeneity in loading and release of dopants like carbon allotropes and drugs, respectively, in the bulk and on the surface has always been a challenge. Herein, we are reporting a methodological cascade to achieve a model, customizable, 3D printed, homogeneously layered and electrically stimulatory, PLA-Graphene nanoplatelet (hl-PLGR) based drug delivery device, called 3D-est-MediPatch. The medicinal patch has been prepared by 3D-printing a Nic-hl-PLGR composite obtained by incorporating a redox active model drug, niclosamide (Nic) in hl-PLGR. The composite of Nic-hl-PLGR was characterized in three sequentially complex forms─composite film, hot melt extruded (HME) filament, and 3D printed (3DP) patches to understand the effect of filament extrusion and 3D-printing processes on Nic-hl-PLGR composite and overall drug incorporation efficiency and control. The incorporation of graphene was found to improve the homogeneity of the drug, and the hot melt extrusion improved the dispersion of drug and graphene fillers in the composite. The electroresponsive drug release from the Nic-hl-PLGR composite was found to be controllably accelerated compared to the drug release by diffusion, in simulated buffer condition. The released drug concentration was found to reach within the IC50 range for malignant melanoma cell (A375) and showed in vitro selectively, with reduced effects in noncancerous, fibroblast cells (NIH3T3). Further, the feasibility of application for this system was assessed in generating personalized 3D-est-MediPatch for skin, liver and spleen tissues in ex-vivo scenario. It showed excellent feasibility and efficacy of the 3D-est-MediPatch in controlled and personalized release of drugs during electrostimulation. Thus, a model platform, 3D-est-MediPatch, could be achieved by suitably incorporating a hydrophobic, redox-active drug (niclosamide) in poly lactic acid-graphene nanoplatelet composite for electrostimulatory therapeutics with reduced side effects.

A unified hybrid micromechanical model for predicting the thermal and electrical conductivity of graphene reinforced porous and saturated cement composites

Graphene fillers have gained widespread attention as functional reinforcements for cement composites due to their excellent physical properties. The prediction of the thermal and electrical properties of graphene reinforced cement composites (GRCCs) is of great importance for developing intelligent and multifunctional civil engineering materials and structures. In this current work, a unified hybrid micromechanical model combining effective medium theory (EMT) and Mori-Tanaka-Benveniste (MTB) is developed to simultaneously predict the thermal and electrical conductivity of the GRCCs with considering pores and saturation, in which mechanisms including phonon transport, electron tunnelling and Maxwell-Wagner-Sillars (MWS) polarization are incorporated. Graphene nanoplatelets (GNPs) reinforced cement composites (GNPRCCs) samples are prepared and tested to validate the developed unified model. The results show that the electrical conductivity of the GNPRCCs is more sensitive to saturation than the thermal conductivity. When the porosity n = 0.2 and the GNP concentration is 1 wt%, the relative thermal and electrical conductivity increases by 5 % and 193 %, respectively, when the saturation index increases from 0.6 to 1. Elongated pores are more favorable for the formation of ionic networks for electrical conductivity in the saturated GNPRCCs, while spherical pores are more beneficial for heat transport. Elongated graphene fillers are preferred for enhancing both the thermal and electrical conductivity of dry and saturated GNPRCCs. The work is envisaged to provide guidelines for developing multifunctional cement composites.

Screw Extrusion as a Scalable Technology for Manufacturing Polylactide Composite with Graphene Filler

Screw Extrusion as a Scalable Technology for Manufacturing Polylactide Composite with Graphene Filler

Float-stacked graphene–PMMA laminate

Semi-infinite single-atom-thick graphene is an ideal reinforcing material that can simultaneously improve the mechanical, electrical, and thermal properties of matrix. Here, we present a float-stacking strategy to accurately align the monolayer graphene reinforcement in polymer matrix. We float graphene-poly(methylmethacrylate) (PMMA) membrane (GPM) at the water–air interface, and wind-up layer-by-layer by roller. During the stacking process, the inherent water meniscus continuously induces web tension of the GPM, suppressing wrinkle and folding generation. Moreover, rolling-up and hot-rolling mill process above the glass transition temperature of PMMA induces conformal contact between each layer. This allows for pre-tension of the composite, maximizing its reinforcing efficiency. The number and spacing of the embedded graphene fillers are precisely controlled. Notably, we accurately align 100 layers of monolayer graphene in a PMMA matrix with the same intervals to achieve a specific strength of about 118.5 MPa g−1 cm3, which is higher than that of lightweight Al alloy, and a thermal conductivity of about 4.00 W m−1 K−1, which is increased by about 2,000 %, compared to the PMMA film.

Conductive polymer biocomposites based on poly(3-hydroxybutyrate) and poly(butylene adipate-co-terephthalate) with various graphene fillers for thermistor applications

Conductive polymer biocomposites based on poly(3-hydroxybutyrate) and poly(butylene adipate-co-terephthalate) with various graphene fillers for thermistor applications

Fluorinated Graphene Fillers for High-Performance Solid-State Lithium Batteries

Solid-state batteries (SSBs) are expected to revolutionize the field of energy storage due to their superior safety and high energy density, which result from the use of lithium metal as the negative electrode. However, the development of solid-state electrolytes (SSEs), the key component of SSBs, is quite crucial. SSEs have high thermal stability, high mechanical strength, and a wide electrochemical window but lack enough ionic conductivity; which is one of the most challenging aspects. Incorporating suitable active or inert fillers in the solid polymer electrolyte matrix is one of several methods adopted to improve the ionic conductivity of pure polymer SSEs. Two-dimensional graphene-based fillers are a promising option as they provide a high surface area for creating an abundant interface with the polymer matrix creating a continuous pathway for lithium-ion transport and simultaneously their robust nature improves the mechanical strength of the electrolyte. Pristine graphene is electronically conducting in nature owing to the continuous sp2 carbon linkages, but the electronic conductivity can be suppressed by disrupting the sp2 bonds by heteroatom functionalization on the graphene. This study investigates the heteroatom functionalization of graphene to obtain various graphene-based fillers such as graphene oxide (GO), reduced graphene oxide (rGO), and fluorinated graphene oxide (FGO) and their effectiveness when introduced into a polymer SSE matrix for LiNi0.8Co0.1Mn0.1O2-based SSBs. FGO filler outperforms others in terms of ionic conductivity, thermal stability, enhanced electrochemical potential window, and compatibility of the SSE. The optimized ratio of FGO fillers in SSE demonstrates excellent electrochemical performance, enabling long-term Li plating/stripping with small overpotential and stable cycling of Li/ LiNi0.8Co0.1Mn0.1O2 full cells. This work highlights the notable potential of FGO materials in improving the comprehensive properties of polymer SSEs and promoting the applications of polymer SSEs in high-performance SSBs.

Experimental and numerical studies on the mechanical characteristics of Timoho fiber epoxy composites with nanofiller addition

AbstractThis study is focused on the investigation of the mechanical characteristics of Timoho fiber (TF) epoxy composites with graphene as the filler material, both experimentally and numerically, for high‐velocity impacts. The composites were prepared by the compression molding process with varying wt.% of graphene. An experimental approach was undertaken to study the behavior of the composites under different wt.% of graphene. To validate the results obtained in the experimental approach, numerical studies were conducted. It was observed that there was an enhancement in the mechanical properties with the addition of graphene. For tensile strength, there was an increase of 33.17% when comparing the controlled sample (0% graphene) and the sample with 2% graphene content. Subsequently, there was an increase of 36.48%, 58.02%, and 29.79% when comparing the controlled samples and samples with 2% graphene, respectively, for flexural, impact, and interlaminar shear strength (ILSS). However, it was observed that after the addition of 2 wt.% of graphene, the mechanical strength decreased due to the agglomeration of graphene inside the composite, which was confirmed using the SEM analysis. For the numerical study, ANSYS workbench was employed, and simulation was conducted using finite element analysis (FEA) for the tensile and flexural test. The numerical findings were found to be reasonably close to the experimental values, with variations ranging from a minimum of 2% to a maximum of 15%. In the design of experiments, Taguchi's approach was used to determine the effect of a variety of parameters on the tensile behavior of the TF epoxy composites.Highlights 2 wt.% of graphene was observed to be the optimum concentration of graphene. The decline in mechanical properties was observed at 3 and 4 wt.% of graphene. Agglomeration of graphene filler in the composite was confirmed using SEM. ANOVA showed that wt.% of graphene made the top contribution to tensile strength. The nanographene‐incorporated TF composites can be used for lightweight applications.

Graphene-based phononic crystal lenses: Machine learning-assisted analysis and design

The advance of artificial intelligence and graphene-based composites brings new vitality into the conventional design of acoustic lenses which suffers from high computation cost and difficulties in achieving precise desired refractive indices. This paper presents an efficient and accurate design methodology for graphene-based gradient-index phononic crystal (GGPC) lenses by combing theoretical formulations and machine learning methods. The GGPC lenses consist of two-dimensional phononic crystals possessing square unit cells with graphene-based composite inclusions. The plane wave expansion method is exploited to obtain the dispersion relations of elastic waves in the structures and then establish the data sets of the effective refractive indices in structures with different volume fractions of graphene fillers in composite materials and filling fractions of inclusions. Based on the database established by the theoretical formulation, genetic programming, a superior machine learning algorithm, is introduced to generate explicit mathematical expressions to predict the effective refractive indices under different structural information. The design of GGPC lenses is conducted with the assistance of the machine learning prediction model, and it will be illustrated by several typical design examples. The proposed design method offers high efficiency, accuracy as well as the ability to achieve inverse design of GGPC lenses, thus significantly facilitating the development of novel phononic crystal lenses and acoustic energy focusing.

Graphite- and Graphene-Based Polymer Nanocomposites for Flexible Sensors and Actuators in Health Care and Soft Robotics Applications

Flexible sensors and actuators have broad applications in the fields of wearable electronics for health, sports, functional textiles, robotics and cobot applications. Graphene-or graphite-based polymer nanocomposites are promising materials for the development of soft sensors and actuators. This study investigates strain sensing properties of silicon rubber with various graphene filler concentrations (8wt%-12wt%). Current-voltage characteristics have been measured under various strains. We obtain that the sensor’s electrical resistance, for a given voltage, can be approximated by a linear fit of the logarithmic resistance as function of the extension ratio of the sensor. The obtained mechanically induced logarithmic resistor behavior of the polymer nanocomposite is highly promising for the development of electronic sensing and control. Furthermore, thin film graphite layers were investigated on highly stretchable silicone membranes.