Multilayer Graphene Nanoplatelets Research Articles

Damping and mechanical behavior of graphene nanoplatelets reinforced Al-30Zn alloy matrix bioinspired laminated composites by two steps flake powder metallurgy

Damping and mechanical properties are often incompatible in metallic materials. In this paper, bio-inspired laminated graphene nanoplatelets (GNPs) reinforced Al-30Zn alloy matrix composites with an outstanding combination of damping-mechanical properties are prepared using a flake powder metallurgy (FPM) process. The increased grain/phase boundary owing to grain refinement improves the intrinsic damping properties of the composites, while the lamellar grains promote the oriented alignment and crack deflection of GNPs. The multilayered GNPs with large specific surface area experienced repeated stretching and compression during cyclic bending deformation, leading to intense interfacial frictional slip, and GNPs' high intrinsic thermal conductivity also helped to dissipate heat quickly, which promoted mechanical energy dissipation. The improvement in mechanical properties is mainly attributed to grain refinement, the load transfer effect of GNPs and their interaction with dislocations. The Al-30Zn-0.5GNPs composites showed the best combination of damping properties and mechanical properties.

Natural coal-derived graphite as rubber filler and the influence of its progressive graphitization on reinforcement performance

This study introduces a reinforcing rubber filler, natural coal-derived graphite (NCDG), evaluating how its progressive structural evolution from meta-anthracite (MA), semi-graphite (SG) to cryptocrystalline graphite (CG) during the natural graphitization process affects their reinforcing performance to styrene-butadiene rubber (SBR) composites. The highly graphitized NCDG fillers exhibit good filler dispersion, more bound rubber content, and well compatibility between filler and rubber matrix when compounded with SBR, and significantly enhance the mechanical properties of SBR composite (tensile strength can reach 22.8 MPa), as well as improving the storage modulus, wet-skid resistance, wear resistance, and electrical conductivity. The formation of microcrystalline multilayer graphene and graphene nanoplatelets exfoliated by mechanical shear stress during ball grinding and rubber compound mixing plays an important role in improving the reinforcement performance of rubber composites. This research provides valuable insights into the utilization of NCDG as a cost-effective and environment-friendly reinforcing filler for rubber composites.

Improved photoelectrochemical performance of tungsten-catalyzed graphene nanoplatelet electrodes prepared by hot-wire chemical vapor deposition at low substrate temperatures

The current increase in demand for graphene in various energy applications such as electrode materials for supercapacitors, batteries, thermoelectric, and hydrogen production via water-splitting, the production of high-quality graphene, considering its fascinating physical and electrical properties, high-yield, and large-area has becoming more challenging at the research and development level. Therefore, in this work, graphene nanoplatelets (GNPs) were directly grown on tungsten nanoparticle (W NP)-coated p-type crystalline silicon and quartz substrates using hot-wire chemical vapor deposition at low substrate temperatures (<500 °C). Prior to the GNP deposition, a plasma process was employed to induce the formation of W NPs, which act as a metal catalyst for facilitating the growth of large-area and multi-layer GNPs. The W NPs were formed at substrate temperatures ranging from 250 to 550 °C, with the largest graphene sheet was grown at 450 °C. Higher substrate temperatures promote the growth of high-quality graphene layers with high intensities of G (IG) and 2D bands (I2D), and high I2D/IG ratio values. The GNP photoelectrode prepared at 450 °C demonstrated better photoelectrochemical responses with the highest photocurrent density of 1.65 mA/cm2 at 1.5 VAg/AgCl, the lowest charge transfer resistance (14.0 kΩ), and the highest donor density (2.57 × 10 28 cm−3) compared to the tungsten carbide thin film and W NP electrodes prepared at the same temperature. The effects of substrate temperature on the optical, structural, and photoelectrochemical properties of the as-grown GNPs are discussed.

Fabrication of nanoporous multilayer graphene nanoplatelets membrane for water desalination

In recent years, graphene-based membranes are extensively explored for desalination process to fulfil the pure water scarcity. Still, there is a noticeable gap in the research on a technique that simultaneously deposits a membrane and also generates pores in the flake of membrane. In this work, we demonstrated a one-step and scalable protocol i.e. a conventional atmospheric plasma spraying (APS) to fabricate a graphene nanoplatelets (GNP) membrane for water desalination application. Various characterization tools: FE-SEM, Raman, and TEM etc. utilized to evaluate the deposition of GNPs flakes and induced sub-nanometer pores in the large area GNP membrane. Plasma-sprayed GNP membrane showed impressive desalination performance in terms of water flux, salt rejection, and permeability around ~67 Lm−2 h−1, ~99 %, and ~ 115 Lm−2h−1bar−1 respectively at 0.6 bar of transmembrane pressure (TMP). This performance of the GNP membrane was attributed to the critical role of graphene in terms of its structures, including induced pores within graphene sheets and its functions. Our deposited GNP membrane is cost-effective and showed the applicability of conventional plasma spraying in the design of nanomaterials-based membranes for various water purification protocols.

Model Approach to Thermal Conductivity in Hybrid Graphene-Polymer Nanocomposites.

The thermal conductivity of epoxy nanocomposites filled with self-assembled hybrid nanoparticles composed of multilayered graphene nanoplatelets and anatase nanoparticles was described using an analytical model based on the effective medium approximation with a reasonable amount of input data. The proposed effective thickness approach allowed for the simplification of the thermal conductivity simulations in hybrid graphene@anatase TiO2 nanosheets by including the phenomenological thermal boundary resistance. The sensitivity of the modeled thermal conductivity to the geometrical and material parameters of filling particles and the host polymer matrix, filler's mass concentration, self-assembling degree, and Kapitza thermal boundary resistances at emerging interfaces was numerically evaluated. A fair agreement of the calculated and measured room-temperature thermal conductivity was obtained.

Mechanism of multilayer graphene nanoplatelets and its effects on the rheological properties and thermal stability of styrene–butadiene–styrene modified asphalt

Multilayer graphene nanoplatelets (GNPs) have the potential to become the next generation of asphalt modifiers for developing sustainable asphalt pavements. This study investigated the reaction mechanism, high-temperature rheological properties, and thermal stability of styrene–butadiene–styrene (SBS) asphalt modified with GNPs. The GNP-modified asphalts were prepared by incorporating 0.5, 1.0, 1.5, and 2.0 wt% GNPs into SBS asphalt. X-ray diffraction, Fourier-transform infrared spectroscopy, fluorescence microscopy, and atomic force microscopy were employed to investigate the interaction mechanism between GNPs and SBS asphalt, and the high-temperature rheological properties were systematically evaluated using dynamic shear rheometer tests. Saturate, aromatic, resin, and asphaltene (SARA) analysis was applied to investigate the fraction variation after incorporating the GNPs into the SBS asphalt, and grey relational analysis was performed to determine the relationship between the SARA fractions and rheological properties. Thermogravimetric analysis–differential scanning calorimetry experiments were conducted to characterize the heat absorption, specific heat capacity, combustion characteristics, and kinetic parameters of the GNP-modified asphalt. The asphalt molecules were intercalated between the GNPs sheets. The addition of GNPs promoted the development of a polymer-rich phase in the SBS asphalt and a stable three-dimensional network, which hindered the migration of particles at high temperatures. The GNPs improved the rheological properties of the asphalt and produced a more elastic response. Furthermore, the GNPs reduced the combustion intensity and stability of SBS asphalt by up to 12.6 % and 15 %, respectively. The specific heat capacity increased by 10.8 %–174.8 %, and the heat absorption decreased by 49.6 %–75.87 %. By reducing the energy of the system, GNPs decrease the degree of disorder. The highest activation energy and enthalpy were 102.83 and 96.72 kJ mol −1 , respectively, and the Gibbs free energy decreased by 39.7 % at a GNP content of 1.5 wt%. However, excessive GNPs may lead to agglomeration and uneven dispersion in SBS asphalt. • The multilayer graphene nanoplatelets (GNPs) was used to modify SBS asphalt. • Compatibility between SBS asphalt and GNPs was good due to formation of intercalated structure. • GNPs can improve the elastic response and rutting resistance at high temperature. • Enthalpy increased by 76.6 % and entropy decreased by 39.7 % at GNPs content of 1.5 wt%. • Specific heat capacity by 174.8 % and lower the heat absorption by 75.87 % after adding 1.5 wt% GNPs.

Effect of graphene on the piezoelectric properties of cement-based piezoelectric composites

Two types of graphene, namely, graphene oxide (GO) and multilayer graphene nanoplatelets (GNPs), were added to a 0–3-type cement-based piezoelectric composite to investigate the piezoelectric properties of the composite. The aforementioned composite contained a cement matrix and lead zirconate titanate inclusions, each of which accounted for 50% of the composite volume. The results obtained by using ultrasonic vibrations and a hydrometer indicated that the optimal dispersion times of GO in pure water and GNPs in ethanol were 30 and 15 min, respectively. The addition of GO to the aforementioned composite decreased the composite’s relative permittivity (εr) and increased dielectric loss and electrical resistance, resulting in difficulties in poling and poor polarization efficiency. GO is not conducive to improving the piezoelectric properties (piezoelectric charge coefficient d33, piezoelectric voltage coefficient g33, εr, and electromechanical coupling coefficient kt) of piezoelectric composites. GNP addition to cement can reduce the resistivity and increase dielectric loss of cement composites. The composites with a lower resistance can be polarized easily. The appropriate addition of GNPs can improve the polarization efficiency, thereby enhancing the piezoelectric properties of cementitious composites. In this study, the optimal addition of GNPs was 0.3%. Wet-mixing of GNP-containing cementitious composites with a superplasticizer in ethanol can further improve the piezoelectric properties of this composite (d33 = 123 pC/N, g33 = 22.6 ×10−3 V·m/N, εr = 615, and kt = 20.2%). The GNP-containing cementitious composite mixed with a superplasticizer exhibited a high kt; thus, this composite has potential for use as a green energy material.

Sound Velocities in Graphene-Based Epoxy Nanocomposites

Elastic properties of epoxy-based nanocomposites (ENCs) filled with bare and TiO2-deposied multi-layered graphene nanoplatelets (MLG) have been tested by using a phase-frequency continuous-wave ultrasound probing (USP). The dian epoxy CHS-EPOXY 520 curried with diethylenetriamine (DETA) was the polymer matrix for the nanocomposites. The nanoplatelets of the specific surface area Sf ~ 790 m2/g consist of several dozen loosely bound monoatomic graphene layers with an area of about least 5×5 μm2. MLG-mass-loading (φf,m) of the nanocomposites varied from 0.1 % to 5.0 % by weight. Anatase- TiO2 particles, being of about 50 nm in diameter and of Sf ~ 1500 m2/g, have been deposited on MLG in mass concentration of about 1 %. Elastic moduli of the ENCs (namely, the Lame’s constants, the Young’s module, the compression module, and the Poisson’s ratio) have demonstrated negligible variation with φf,m varying regardless the type of filling particles. However, MLG:TiO2-hybrid nanoparticles have proven to impact stronger on the moduli as compared to bare MLG. This result shows a capability to modify molecular structure of epoxy resins by controlling surface reactivity of MLG embedded in the resin.

High frequency dielectric characterization of graphene doped flexible ceramics multilayers

This paper explores the tape casting technique to produce flexible heterostructured multilayers composed of graphene nanoplatelets doped Alumina and Ceria doped Nickel Oxide-Gadolinium. Given the excellent mechanical and electrical properties of graphene, multilayers were structured to explore the dielectric properties at a high-frequency regime. The stability of the suspensions, measured by rheological characterization, showed a pseudoplastic behavior. The structural properties of the flexible tapes were analyzed by X-ray diffraction and scanning electron microscopy. Electrical properties obtained through I − V curves showed an insulating behavior. The dielectric characterization was measured at a high-frequency regime (0.01 up to 1.5 GHz). The findings reflect the strong dependence of the dielectric behavior with the multilayer structure and graphene nanoplatelets doping concentration in the Alumina. The results open new perspectives of multifunctionalization flexible ceramics tapes for high-frequency applications.

Active Flutter Suppression and Aeroelastic Response of Functionally Graded Multilayer Graphene Nanoplatelet Reinforced Plates with Piezoelectric Patch

This paper investigates the aeroelastic flutter and vibration reduction of functionally graded (FG) multilayer graphene nanoplatelets (GPLs) reinforced composite plates with piezoelectric patch subjected to supersonic flow. Activated by the control voltage, the piezoelectric patch can generate the active mass and active stiffness that can accordingly increase the base plate’s stiffness and mass. As a result, it changes the GPLs reinforced plate’s dynamic characteristics. The motion equation of the plate-piezoelectric system is derived through the Hamilton principle. Based on the modified Halpin–Tsai model, the effects of graphene nanoplatelets weight fraction and distribution pattern on the dynamic behaviors of the plate are numerically studied in detail. The result illustrates that adding a few amounts of grapheme nanoplatelets can effectually enhance the aeroelastic properties of the plates. Two kinds of control strategies, including the displacement and acceleration feedback control, are applied to suppress the occurrence of the flutter of the plate. It shows that the displacement and acceleration feedback control can improve the critical flutter Mach number of the plate by attaching active stiffness and active mass, respectively. Furthermore, the combined displacement and acceleration feedback control has a better control effect than that of considering only one of them.

Role of multi-layered graphene as an additional fuel on energy release of Al/MoO3 nano-thermite

ABSTRACT Al/MoO3 nano-thermite is successfully reinforced with MLG (multi-layered graphene) using physical mixing synthesis technique, assisted with ultrasonication. MLG nanoplatelets in the nano-thermite (Al/MoO3) are utilised as an additional fuel to replace the conventional fuel, i.e. Al nanoparticles. The chemical composition and stability of samples are analysed by XRD (X-ray diffraction) and Raman techniques. The FESEM (field-emission scanning electron microscopy) and HR-TEM (high-resolution transmission electron microscopy) analysis revealed the morphology, uniform distribution of MoO3 (metal oxide) and Al, MLG (fuels) and also the contact between constituents of the thermite mixture. DSC (Differential scanning calorimetry) results showed that the exothermic behaviours are affected by the gradual replacement of Al by MLG as a fuel and achieved the maximum energy release of 1220 J/g, which is three times higher than 451 J/g, i.e. energy release in the case of Al/MoO3 conventional nano-thermite.

Structural and Dipole-Relaxation Processes in Epoxy-Multilayer Graphene Composites with Low Filler Content.

Multilayered graphene nanoplatelets (MLGs) were prepared from thermally expanded graphite flakes using an electrochemical technique. Morphological characterization of MLGs was performed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Raman spectroscopy (RS), and the Brunauer–Emmett–Teller (BET) method. DGEBA-epoxy-based nanocomposites filled with synthesized MLGs were studied using Static Mechanical Loading (SML), Thermal Desorption Mass Spectroscopy (TDMS), Broad-Band Dielectric Spectroscopy (BDS), and Positron Annihilation Lifetime Spectroscopy (PALS). The mass loading of the MLGs in the nanocomposites was varied between 0.0, 0.1, 0.2, 0.5, and 1% in the case of the SML study and 0.0, 1.0, 2, and 5% for the other measurements. Enhancements in the compression strength and the Young’s modulus were obtained at extremely low loadings ( 0.01%). An essential increase in thermal stability and a decrease in destruction activation energy were observed at 5%. Both the dielectric permittivity () and the dielectric loss factor () increased with increasing over the entire frequency region tested (4 Hz–8 MHz). Increased is correlated with decreased free volume when increasing . Physical mechanisms of MLG–epoxy interactions underlying the effects observed are discussed.

Optical properties of multilayer graphene nanoplatelet (mGNP)/poly(methyl methacrylate) (PMMA) composite flexible thin films prepared by solvent casting

Optical properties of multilayer graphene nanoplatelet (mGNP)/poly(methyl methacrylate) (PMMA) composite flexible thin films prepared by solvent casting

Effect of Secondary Carbon Nanofillers on the Electrical, Thermal, and Mechanical Properties of Conductive Hybrid Composites Based on Epoxy Resin and Graphite.

In this work, we present a comparative study of the impact of secondary carbon nanofillers on the electrical and thermal conductivity, thermal stability, and mechanical properties of hybrid conductive polymer composites (CPC) based on high loadings of synthetic graphite and epoxy resin. Two different carbon nanofillers were chosen for the investigation—low-cost multi-layered graphene nanoplatelets (GN) and carbon black (CB), which were aimed at improving the overall performance of composites. The samples were obtained by a simple, inexpensive, and effective compression molding technique, and were investigated by the means of, i.a., scanning electron microscopy, Raman spectroscopy, electrical conductivity measurements, laser flash analysis, and thermogravimetry. The tests performed revealed that, due to the exceptional electronic transport properties of GN, its relatively low specific surface area, good aspect ratio, and nanometric sizes of particles, a notable improvement in the overall characteristics of the composites (best results for 4 wt % of GN; σ = 266.7 S cm−1; λ = 40.6 W mK−1; fl. strength = 40.1 MPa). In turn, the addition of CB resulted in a limited improvement in mechanical properties, and a deterioration in electrical and thermal properties, mainly due to the too high specific surface area of this nanofiller. The results obtained were compared with US Department of Energy recommendations regarding properties of materials for bipolar plates in fuel cells. As shown, the materials developed significantly exceed the recommended values of the majority of the most important parameters, indicating high potential application of the composites obtained.

Investigation of the dispersion of multi-layer graphene nanoplatelets in cement composites using different superplasticiser treatments

The emergence of nanomaterials research over the past decades, allows the construction sector to turn the cement-based structures into fully digitised, cognitive assets with additional functionalities and improved durability and sustainability performance. Multi-layer graphene nanoplatelets (GNPs) is one such nanomaterial that could be used in cementitious structures. However, the homogenous dispersion of commercially available GNPs has been found to be a key challenge in the literature. This study aimed to develop a practical dispersion protocol to promote the use of GNPs in cementitious systems. Four different commonly used superplasticisers were tested, including a lignosulphonate, a naphthalene-based and two polycarboxylates, along with sonication. The GNPs were characterised using Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and X-Ray Diffraction analysis (XRD). The effect of the different superplasticisers on the GNPs dispersion in water was tested with zeta-potential, while UV–Vis spectroscopy was used to examine the effect of the superplasticiser dosage. This was followed by rheology testing that assessed the impact of the superplasticisers on dispersing the GNPs in cement paste. It was found that dispersion of GNPs in water with sonication is not sufficient and a chemical treatment is also needed. The polycarboxylates that work by a steric hindrance mechanism, by physically separating the GNPs and cement particles, were found to be more effective compared to the plasticisers that work by electrostatic repulsion. This research provides a practical dispersion protocol for GNPs in cementitious systems to promote more advanced construction materials.

Facile synthesis of multilayer graphene nanoplatelets/ZnCo2O4 microspheres with enhanced performance for asymmetric supercapacitors

Multilayer graphene nanoplatelets/ZnCo2O4 (MGNs/ZnCo2O4) microspheres were prepared by two-step method using multilayer graphene exfoliated by polymer mixing method as scaffold. Benefiting from the structural stability of spherical structure and the added active sites of mesoporous construction for redox reactions, the MGNs/ZnCo2O4 microspheres electrode delivers an enhanced specific capacitance of 960 F g−1 at 1 A g−1 and a cycling stability of 78.9% at 5 A g−1 after 2000 cycles. Furthermore, the MGNs/ZnCo2O4//active carbon asymmetric supercapacitor (ASC) exhibits an energy density of 17.78 Wh kg−1 at a power density of 0.75 kW kg−1. The innovative addition of multilayer graphene nanoplatelets to improve conductivity and structure stability is very enlightening to other composite material in supercapacitor.

High-Performance Lithium Sulfur Batteries Based on Multidimensional Graphene-CNT-Nanosulfur Hybrid Cathodes

Although lithium-sulfur (Li-S) batteries are one of the promising candidates for next-generation energy storage, their practical implementation is limited by rapid capacity fading due to lithium polysulfide (LiPSs) formation and the low electronic conductivity of sulfur. Herein, we report a high-performance lithium-sulfur battery based on multidimensional cathode architecture consisting of nanosulfur, graphene nanoplatelets (2D) and multiwalled carbon nanotubes (1D). The ultrasonic synthesis method results in the generation of sulfur nanoparticles and their intercalation into the multilayered graphene nanoplatelets. The optimized multidimensional graphene-sulfur-CNT hybrid cathode (GNS58-CNT10) demonstrated a high specific capacity (1067 mAh g−1 @ 50 mA g−1), rate performance (539 @ 1 A g−1), coulombic efficiency (~95%) and cycling stability (726 mAh g−1 after 100 cycles @ 200 mA g−1) compared to the reference cathode. Superior electrochemical performances are credited to the encapsulation of nanosulfur between the individual layers of graphene nanoplatelets with high electronic conductivity, and effective polysulfide trapping by MWCNT bundles.

Study of energy release in Fe2O3/Al nano-thermite with graphene as an additional fuel

In nano-thermites, due to improper contacts between the reactants in solid-state reaction, the complete energy release during redox-reaction is still challenging. Here, Fe2O3/Al nano-thermite is synthesized with different weight fraction of multi-layered graphene (MLG) nanoplatelets by physical mixing technique. X-ray diffraction reveals that the synthesis method does not change the phase of reactants. The morphology of nano-thermite is examined by scanning electron microscopy and transmission electron microscopy which reveals that MLG nanoplatelets are homogeneously dispersed in the samples. Structural stability of MLG nanoplatelets present in nano-thermite is observed by Raman spectroscopy. The nano-thermite reaction is analyzed by differential scanning calorimetry. The results show that an increase in MLG content in nano-thermite sample Al/Fe2O3, from 0 wt% to 12 wt% is responsible for increase in the corresponding exothermic enthalpy from 71 J/g to 1537 J/g. On the contrary, ignition temperature and activation energy of these samples get reduced with increasing MLG.

Natural frequency, damping and forced responses of sandwich plates with viscoelastic core and graphene nanoplatelets reinforced face sheets

The free and forced vibration analysis of a sandwich plate with the viscoelastic core and face layers reinforced functionally with multilayered graphene nanoplatelets is presented. Different graphene nanoplatelet distributions are considered through the thickness, and the effective properties of the graphene reinforced nanocomposite are obtained by the rule of mixture. The equations of motion are extracted using Hamilton’s principle and assuming the classical thin plate theory for face layers and the first-order shear deformation theory for the thick viscoelastic core. Assuming the simply-supported boundary condition for all edges, the displacement components are proposed by Fourier series and the complex eigenvalue problem is solved to obtain the natural frequencies as well as the loss factors. The results are validated with available investigations, and effects of some important parameters on the free and forced responses of the sandwich plate are studied.

Expression of interfacial Seebeck coefficient through grain boundary engineering with multi-layer graphene nanoplatelets

Expression of energy filtering to boost thermoelectric performance through grain boundary engineering utilising graphene.