Graphene Nanofillers Research Articles

The effect of graphene on the activation energy of grain growth for the nanocrystalline thermoelectric n-type Bi2Te2.7Se0.3

Even though bismuth telluride is frequently produced by mechanical alloying for thermoelectric materials, no data has been published addressing the thermal behavior and activation energy of the milled n-type Bi2Te2.7Se0.3 powders. This paper studies the activation energy of grain growth for the nanocrystalline n-type Bi2Te2.7Se0.3 and two graphene-Bi2Te2.7Se0.3 composites with different graphene concentrations (0.05 and 0.5 wt.%). Grain size and structural analyses of these samples have been carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal stability of the three samples is investigated by incorporating differential scanning calorimetry data with the Kissinger model. The activation energy of the pristine Bi2Te2.7Se0.3 alloy is found to be 268 kJ/mol. For the composite samples, a lower graphene weight percentage (0.05 wt.%) increased the activation energy to 270 kJ/mol. In contrast, higher amounts of graphene (0.5 wt.%) reduced the activation energy significantly to 254 kJ/mol. The observed effect is found to be directly related to graphene’s exfoliation in the bismuth telluride matrix. These results offer a better understanding of the thermal behavior of the nanocrystalline pristine n-type Bi2Te2.7Se0.3 and the influence of graphene nanofiller on the thermal stability of the bismuth telluride nanocomposites.

Tribological analysis of jute reinforced composites with different nano-fillers

This study investigates the carbon nanoparticle effects on the bulk and surface of jute-epoxy composites. Nano-fillers Graphene Oxide (GO) and Functionalized Graphene (FG) were used for Jute composite preparation. Tests like density, hardness, wear rate, specific wear rate, volumetric wear rate, are and wear resistance done to evaluate the tribological properties. Graphene Oxide and Functionalized Graphene as nano-fillers enhanced the tribological properties. The tribological test is carried by a pin on disc apparatus operating in dry atmospheric conditions and with different sliding speeds of (5 m/s), applied load (50 N), and distance of slide (10,000 m). The weight of fillers taken is (0.50,0.75, 1.0) weight percentage of Graphene Oxide and Functionalized Graphene nano-fillers. Test results showed that jute composite with 0.50 wt% of Functionalized Graphene and Graphene Oxide displayed improved performance at properties like hardness, wear resistance and volumetric wear loss in comparison to samples without any nano-fillers. After the addition of 0.50 wt.%, further addition of nano-fillers degrades the tribological properties of the sample.

Effect of graphene on the mechanical properties and moisture absorption kinetics of nano filler reinforced glass fiber composites

Recently, Graphene nanofillers have been used as a means of enhancing mechanical properties to a great extent. It has outstanding barrier properties, including stiffness at low loads and flame retardancy. It’s wonderful reinforcing properties make Graphene one of the most promising nano-fillers for orthopaedic leg braces. The composites were made by adding Graphene as a nano-filler to epoxy resins at suitable weight percentages (2 %, 4 %, 6 %, 8 %, and 10 %). An experiment on moisture absorption was conducted using a five-layer laminate, which was hand-fabricated and uniformly thick. In accordance with ASTM standards, experiments were conducted to evaluate the effect of Graphene on the mechanical properties and the moisture absorption kinetics of these materials. After absorbing moisture at different temperatures with varying Graphene loading, the nano-filler reinforced GFRP materials were submitted to tensile, flexural, and impact tests. Results of tensile and flexural tests showed Graphene incorporation of up to 4 % weight provided a maximum tensile strength of 92 MPa as well as a maximum flexural strength of 176 MPa. With the addition of 6 % Graphene nano-filler, the impact strength of GFRP composite was enhanced to 5.8 J. In direct result of these experiments, composites have been applied in a diverse range of industries.

A review on graphene/rubber nanocomposites

Abstract The numerous combinations of different rubbers as matrix materials with graphene/graphene derivatives as nanofillers, which are used to fabricate graphene/rubber nanocomposites, are illustrated in this study. The different processing methods for producing graphene/rubber nanocomposites are investigated in depth. Furthermore, based on the results of various experiments performed with the produced graphene/rubber nanocomposites, an attempt is made to establish an outline over the influence of graphene nanofillers inside the rubber matrix. To explain the composite material characteristics, different processes, and the consequence of the incorporation of graphene/graphene derivatives nanofillers, a unique approximation has been accomplished.

Free Vibration Response of FG Porous Joined Hemispherical–Cylindrical–Hemispherical Shell Vessels Reinforced by Graphene Platelet

In this research, the natural frequency behavior of functionally graded (FG) porous joined hemispherical–cylindrical–hemispherical shell vessels reinforced by graphene platelet (GPLs) has been studied for the first time. Three various types of porosity distribution are assumed through the thickness direction of shell vessel. In the two types of porosity patterns, a pattern of porosities in metal matrix is symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in metal matrix. Extended role of mixture and Tsai-Halpin is used to determine the mass density and Young’s modulus of elasticity of the structure, respectively. By employing 3D elasticity theory, Hamilton’s Principal and FEM in conjunction with Rayleigh–Ritz method, the governing equations of motion of the joined shell vessel are obtained and natural frequencies are extracted. The impact of various factors such as coefficient of porosity, several porosity patterns along with different GPLs distributions and weight fraction of graphene nanofillers on natural frequency behavior of FG porous joined hemispherical–cylindrical–hemispherical shell vessels reinforced by GPLs nanofillers has been reported for the first time.

Reduced graphene oxide as an adhesion enhancer of fusion-bonded epoxy coatings

Alternative coating technologies based on advances in polymer engineering have been continuously developed to face the always present challenges of wear in metal surfaces. Fusion-bonded epoxy (FBE), an epoxy-based powder coating, has been widely used in some sectors due to its quick and easy application and the reduction of waste material. FBE is a high-performance composite with approximately 30 wt% microparticles, and the challenge addressed herein is to improve the coating properties by adding a low content of graphene. In this work, new coatings based on FBE and thermally reduced graphene oxide (rGO) were developed and prepared by two different processes: in one case, highly thermally stable and low functionalized graphene (rGO-tre with 4.6 % oxygenated groups) and in the other case, highly exfoliated and more functionalized graphene (rGO-tr with 9.8 % oxygenated groups). FBE/rGO-tr and FBE/rGO-tre nanocomposites were produced in concentrations of 0.1, 0.3, 0.5 and 1.0 wt% in a planetary ball mill. The coated steel plates were heated in a conventional oven at 204 °C, and the curing of the material was confirmed by using differential scanning calorimetry (DSC) analysis. The addition of rGO-tr (1.0 wt%) and rGO-tre (0.5 wt%) improved the adhesion of the nanocomposite coating in the wet test by 104 % and 95 %, respectively, when compared with neat FBE coatings. Small gains in abrasion and hardness were also observed. In addition to the tendency to reduce indentation (micro and nano), it was possible to observe a better recovery of the FBE with the addition of rGO-tr and rGO-tre after the deformation carried out by the tip. The integration of graphene nanofillers of different grades in a ternary composite with silicate microparticles and epoxy powder was successfully achieved, and the adhesion, abrasion and hardness benefit from the synergy between micro- and nanofillers.

Nonlinear static and dynamic isogeometric analysis of functionally graded microplates with graphene-based nanofillers reinforcement

The main contribution of this study is to propose an efficient and straightforward numerical model for exploring size-dependent geometrically nonlinear static and dynamic characteristics of functionally graded microplates reinforced by graphene nanofillers. To accomplish this purpose, modified couple stress theory including only one material length scale parameter is utilized to capture the size-dependent effect while the displacement field of small-scale structures is calculated by using four-variable refined plate theory and von-Kármán assumptions within the framework of isogeometric analysis. In this study, four dispersion patterns of graphene-based nanofillers along the thickness direction of microplate models are investigated under various static or dynamic loads. Solutions of nonlinear governing equation of motion can be obtained based on the Newton–Raphson iterative procedure and Newmark's time integration scheme. The Rayleigh damping is included, for the first time, to explore the influence of damping on the oscillations of functionally graded microplates reinforced by graphene nanofillers under three dynamic loads including step, triangular and half-sine pulses. Herein, several numerical examples are conducted to investigate the influences of a wide range of significant parameters on the geometrically nonlinear behaviors of functionally graded microplates with graphene nanofillers reinforcement. The significant outcomes of the present study can be referred to as benchmark results as well as provide valuable guides for designing small-scale structures with excellent features in the future.

Flexural and dynamic response of carbon/epoxy laminates with graphene nanofillers and Al6061 alloy

The mechanical and vibrational isolation properties of reinforced carbon fibre composites, such as carbon fibre [0]7s/epoxy, carbon fibre [0]6s/Graphene nanopowder/epoxy, and carbon fibre [0]4s/epoxy/Al 6061, are investigated in this research. Ultrasonic stirring was employed in a carbon fiber/graphene-nano powder laminate to reinforce 0.5 weight percent graphene nanoparticles with the resin. The effect of nano-fillers and metal laminate in the carbon fiber composite specimen was analysed by considering glass transition temperature, flexural modulus, and natural frequency. The results show that the Carbon Fiber Reinforced Polymer (CFRP) with graphene shows a 16.9% and 57.5% increment in flexural strength compared to CFRP and CFRP with Al6061 alloy. In contrast, in the DMA test, the glass transition temperature and other parameters show the least difference, whereas the loss modulus is 34.3% and 67% high for CFRP compared to CFRP/graphene and CFRP/Al6061 samples. Furthermore, using graphene nanopowder and aluminium plates reduces the carbon epoxy laminate’s inherent frequency.

Effects of various functional groups in graphene on the tensile and flexural properties of epoxy nanocomposites: a comparative study

In this article, we investigated the effects of different functional groups in graphene on the mechanical performance of epoxy nanocomposites fabricated using the in-situ polymerization method. This study considered pristine graphene and three different varieties of functionalized graphene (–NH2, –COOH, and –OH) with varying weight percent (i.e., 0.25, 0.5, and 1.0 wt%). The functional groups grafted of graphene have been confirmed through Fourier transforms infrared (FTIR) spectra. Microstructural features and fracture surfaces were also examined by field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy. In comparison to pure epoxy, –OH functionalized graphene/epoxy nanocomposites showed a maximum improvement of 37.24% in tensile strength and 38.05% in flexural strength. The improved mechanical properties of epoxy nanocomposites were attributed to homogeneous dispersion, graphene bridging, and better interfacial contact between epoxy and graphene. HIGHLIGHTS The effect of pristine and functionalized graphene on the mechanical properties of epoxy nanocomposites was studied. Nanocomposites were fabricated for three different wt% (0.25, 0.5, and 1.0) of graphene nanofillers. Field emission scanning electron microscopy (FE-SEM) with EDX was used to examine the microstructural features of fractured surfaces. Graphene enhanced the mechanical properties of epoxy nanocomposites.

Probabilistic-based nonlinear stability analysis of randomly reinforced microshells under combined axial-lateral load using meshfree strain gradient formulations

In the present exploration, an effective numerical strategy is developed to examine for the first time different microstructural-dependent features in the nonlinear stability behavior of nanocomposite microshells containing randomly dispersed nanofillers under combinations of axial and lateral compressive loads. Correspondingly, the modified strain gradient theory of elasticity incorporating dilatation, deviatoric stretch, and rotation gradient tensors is applied to the third-order shear flexible shell framework to accommodate the size dependency. The efficacious material properties are captured via Tsai homogenization approach together with a Monte-Carlo simulation based upon a probabilistic-based homogenization scheme. By employing the constructed moving Kriging meshfree-based numerical strategy, the essential boundary conditions are directly enforced at nodes and the Kronecker delta is satisfied comprehensively using correct type of moving Kriging shape function. For the combined loading condition having domination of axial compression, it is seen that by taking a lateral compressive load into account, the region of snap-through experience becomes wider and the associated minimum load switches to a more induced deflection, while a smaller shortening. Furthermore, for particular values of volume fraction and specific area of graphene nanofillers, combining of axial or lateral compressive load causes that the roles of microscale-dependent gradient tensors in the value of critical stability loads of combined compressed microsized shells becomes a bit less.

Experimental Investigation into a New Method of scalable production of Reduced Graphene Oxide for potential industrial graphene nanocomposite manufacture

Graphene has attracted a great attention in the recent years of research innovations mainly due to its unique properties and in particular, its structural composition of one-atom thick sheet of hexagonally arrayed sp2 carbon atoms. This article focuses on a method of synthesis of graphene oxide granules, which can be use as nanofiller in polymer matrix. Polymer nanocomposites reinforced with graphene nanofillers have better mechanical, thermal and electrical properties than pure polymer materials. Some corrugated spherical structures/granules of reduced graphene oxide were produced by a dispersion/drying method. For this purpose the reduced graphene oxide suspension produced in the laboratory by an improved method was mixed on a magnetic stirring and delivered by a peristaltic pump to the granulation zone at a speed 10-20 ml/min. The granulation zone temperature was kept within 40-150°C. The suspension was dispersed by compressed air up to 3 atmospheres. The produced granules were accumulated in a receiver, and dried in the vacuum oven to remove residues of solvents used in the process. The engineered reduced Graphene oxide were analyzed and the material structural-morphology was characterized by XRD, TGA, UV, Raman and SEM.

Study on theoretical modeling and mechanical performance of a spinning porous graphene nanoplatelet reinforced beam attached with double blades

In this article, theoretical modeling and vibration characteristics of a spinning double-blade beam assembly restricted by elastic supports are studied. Graphene nanoplatelet (GPL) reinforcement and porous foamed metal matrix are adopted to make up the assembly structure. Due to the nonuniformity of the porosity and graphene nanofillers, the material properties of the attached blades and beam are considered to change along the blade thickness and beam radius, respectively. They are obtained via the rule of mixture, the open-cell scheme and the Halpin-Tsai micromechanics model. These attached blades and beam are modeled in accordance with the Euler-Bernoulli beam theory and the Rayleigh beam theory, respectively. Via employing the Lagrange’s equation, the equations of motion of the double-blade beam are derived. Then, the natural frequencies of the spinning nanocomposite double-blade beam are calculated by the substructure modal synthesis method and the assumed modes method. A detailed parameter analysis is performed to study the influences of dimension, distribution pattern and weight fraction of GPLs, distribution and coefficient of porosity, length and location of the blades, stiffness and location of supports, and spinning speed on the mechanical behaviors of the double-blade beam assembly.

Conductive epoxidized natural rubber nanocomposite with mechanical and electrical performance boosted by hybrid network structures

Stretchable conductive elastomers have aroused great interest in recent years as candidates for smart rubber materials. A single conductive filler embedded in an elastomer matrix has been demonstrated to provide electrically conductive pathways, but the filler network can be improved by adding a second conductive filler. Herein, reinforced conductive epoxidized natural rubber (ENR) composites were designed to have hybrid nanostructures of multiwalled carbon nanotubes (MWCNT) with few-layer graphene (FLG) nanofillers. With both MWCNT and FLG, the ENR nanocomposites exhibited improved mechanical performance, filler dispersion, and electrical properties. The tensile strength of ENR filled with MWCNT and FLG was remarkably improved, and the Halpin-Tsai model revealed effective reinforcement by the MWCNT/FLG hybrid filler. Meanwhile, the electrical percolation threshold was decreased by 70% from 1.19 vol% for single nanofiller to 0.36 vol% for hybrid nanofiller. The main reasons for remarkable boosting of desirable characteristics of the hybrid nanocomposites are the uniform filler dispersion and the bridging between MWCNT and FLG through π-π interactions and filler-rubber interactions. Thus, ENR reinforced with hybrid nanostructures is a highly promising advanced conductive elastomeric material for smart rubber applications.

Glass Fibre Reinforced Epoxy Composites Modified with Graphene Nanofillers: Electrical Characterization

Composites with improved electrical properties created new pathways in electrical engineering industries. In this work, electrical studies conducted on continuous unidirectional E‐glass fibre‐reinforced epoxy composites modified with three different graphite oxide fillers are discussed. The three different fillers are (i) graphite oxide (GO), (ii) exfoliated graphite oxide (EGO), and (iii) reduced exfoliated graphite oxide (rEGO). Incorporation of GO fillers exhibited significant improvement in the dielectric characteristics of the composites, where it showed 42% enhancement in breakdown strength values. Dielectric constant measurements of GO‐filled composites have also demonstrated considerable enhancement in the values where the fillers promoted interfacial and dipolar polarization phenomena in the material. On the other hand, in the case of EGO and rEGO fillers, conducting nature induced from graphitic structure had significantly reduced the dielectric properties of their composites.

Investigation of flexural properties of epoxy composite by utilizing graphene nanofillers and natural hemp fibre reinforcement

This study aims to determine the optimum reinforcement required to attain the best combination of flexural strength of modified green composites (graphene oxide + hemp fibre reinforced epoxy composites) for potential use in structural applications. An attempt was also made for the combination of graphene and hemp fibres to enhance load-bearing ability. The infusion of hemp and graphene was made by the weight of the base matrix (epoxy composite). Results showed that graphene reinforcement at 0.4 wt.% of matrix showed load-sustaining capacity of 0.76 kN or 760 MPa. In the case of hemp fibre reinforcement at 0.2 wt.% of the matrix, infusion showed enhanced load-bearing ability (0.79 kN or 790 MPa). However, the combination of graphene (0.1 wt.% graphene nanofillers) and hemp (5 wt.% hemp fibre) indicated a load-sustaining ability of 0.425 kN or 425 MPa, whereas maximum deflection was observed for specimen with hemp 7.5 % + graphene 0.2 % with 1.9 mm. Graphene addition to the modified composites in combination with natural fibres showed promising results in enhancing the mechanical properties under study. Moreover, graphene-modified composites exhibited higher thermal resistance compared to natural fibre reinforced composites. However, when nanofiller reinforcement exceeded a threshold value, the composites exhibited reduced flexural strength as a result of nanofiller agglomeration.

Optimisation of Graphene Nanofiller Addition on the Mechanical and Adsorption Properties of Woven Banana/Polyester Hybrid Nanocomposites by Grey-Taguchi Method

Throughout history, techniques have shifted from mainstream metals and minerals to nanocomposites to generate smaller, more practical elements for particular purposes. Natural fibres have greater advantages than glass fibres, such as being cheaper, recyclable, and nonflammable. The main objective of the current experiment is to determine how the accumulation of graphene to hybrid polyester composites reinforced with woven banana fibre affects their mechanical properties. Composites were constructed utilising the hand lay-up process with the following limitations: (i) graphene filler weightiness, (ii) woven banana fibre thickness in gsm, and (iii) number of woven banana layers, all at three different levels. Using the L9 (33) orthogonal design, nine composite samples are generated and tested according to the ASTM standard. According to the grey research, hybrid composites having 5% graphene powder and 350 grammes per square metre of woven banana fibre in three layers have high mechanical strength. Adding fibre content to immaculate polyester increased its mechanical properties in general. As the fibre and filler concentrations grew, more energy was required to break the fibre bundles between the matrix and its resin. The confirmation test by the optimal process value utilising the grey relation analysis is considerably better than the actual test data. Tension strength has improved by 17.14%, bending strength has improved by 96.75%, and impact energy has increased by 16.17%.

Influence of Graphene Nano Fillers and Carbon Nano Tubes on the Mechanical and Thermal Properties of Hollow Glass Microsphere Epoxy Composites

The present work aimed to analyze the roll of carbon nano tubes and graphene nano fillers on the mechanical and thermal characteristics of hollow glass microsphere reinforced epoxy composites. Composites with varying content of hollow glass microballoons (2, 4, 6, 8, and 10 wt %) reinforced in epoxy matrix were fabricated. Additionally, two more types of composites, one with graphene nano fillers and the other with carbon nano tube at a constant 0.5 wt %, were fabricated with varying weight percentages of hollow glass microballoons (2, 4, 6, 8, and 10%). The composites were fabricated using an open mold casting process. Composites were tested for thermal and mechanical properties. The tensile and flexural moduli were found to rise as the HGM concentration increased. Graphene-filled HGM/epoxy composites revealed the highest modulus compared with HGM/epoxy and HGM/CNT/epoxy composites. The impact strength of all composite types decreased as the HGM content increased. Neat epoxy specimens revealed low response as compared with all the composites tested. Further, the thermal conductivity of HGM/epoxy composites was lower as compared with other compositions and neat epoxy. Scanning electron microscopy was used to analyze the surface morphological behavior of the composites subjected to flexural test. It was found that HGM/G/E composites with 10% of HGM and 0.5% of graphene by weight in epoxy matrix were the optimum.

Modified couple stress-based nonlinear static bending and transient responses of size-dependent sandwich microplates with graphene nanocomposite and porous layers

This paper investigates the nonlinear static bending and dynamic transient responses of the rectangular and circular sandwich microplates composed of functionally graded graphene nanocomposite (GNC) face sheets and a porous polymeric core layer based on the modified couple stress theory (MCST) within the isogeometric analysis (IGA) framework. The four-variable higher-order shear deformation refined plate theory (RPT) and the von Kármán large deflection assumption are synthetically employed to describe the kinematics of the microplate. The nonlinear governing equations of motion are derived from the Hamilton’s principle. The nonlinear bending problem is solved by the Newton–Raphson technique under a displacement criterion strategy, while the dynamic responses under transient loads are obtained by the Newmark integration scheme in conjunction with Newton–Raphson iterative procedure. Comparisons are carried out to test the accuracy of iteration procedure in present formulation and the reliability in capturing small scale effect of present model. Obtained outcomes reveal that raising the material length scale (MLS) parameter and volume fraction index of graphene nanofillers both leads to reductions in nonlinear static deflections, dynamic amplitudes of deflection and periods of motion. The examples for porosity coefficient show that embedding pores in core layer leads to slight changes in terms of static and dynamic responses and an improvement in weight reduction of the sandwich microplate.

Thermo-responsive and electro-active shape memory poly(styrene-b-isoprene-b-styrene)/poly(ethylene-co-1-octene)/graphene composites: Effect of size of graphene nanoplatelets

Thermally and electrically triggered poly(styrene-b-isoprene-b-styrene) (SIS) and poly(ethylene-co-1-octene) (PEO) thermoplastic elastomer blend composites having a SIS/PEO weight ratio of 40/60 were prepared by melt blending method. Two different graphene nanoplatelets (GnPs) with different sizes (small size (SG) and big size (BG)) were used as conductive fillers at different amounts. The thermo-responsive and electro-active shape memory performances of the composites as well as their morphological, mechanical and thermal properties were investigated by paying attention to the effect of size and loading degree of the graphene nano-fillers. Both the BG and the SG improved elastic modulus with increase in amount of the fillers. The modulus values increased by 553 % and 507 % for the 50BG and 50SG composites having 50 phr GnPs respectively, as compared to the blend. Heat-triggered thermo-mechanical shape memory tests showed that the BG filler is more advantageous for shape fixing whereas the SG filler is favorable to shape recovery ability. The electrical percolation threshold was achieved at relatively lower content for the BG filler. The 50BG composite exhibited electro-active shape recovery under 25 V, while the SG composite recovered its shape under 65 V. The thermal stability of the blend significantly improved by the use of the both fillers. The degradation onset temperatures of the 50SG and the 50BG composites increased by 25 °C and 10 °C, respectively, compared to the blend.

Static and buckling characteristics of the porous ring reinforced by graphene nanofillers

The present work focuses on the static and buckling characteristics of the confined functionally graded porous (FGP) ring consolidated by graphene nanofillers (GNF). The ring is under a temperature rise field when a point load is applied on the crown position. The Halpin-Tsai micromechanics theory is used to evaluate the distribution of Young’s modulus, and the Gaussian random field theory is used to evaluate the distribution of the porosity and mass density, respectively. The influence of the thermal field on the buckling load is quantized by applying the energy function and nonlinear thin-walled shell theory. The analytical buckling load is examined numerically, and good agreement is obtained. Furthermore, the present analytical and numerical results are verified effectively by other closed-form predictions when the FGP-GNF ring reduces to a homogeneous ring. Finally, comprehensive parametric study is taken by analyzing the effect of parameters on the buckling load. These parameters include the temperature rise, porosity coefficient, weight fraction, geometric parameters of GNF, friction coefficient and Young’s modulus of the medium.