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A mechanically robust flexible transparent conductor with high thermal and chemical stability was fabricated from welded silver nanowire networks (w-Ag-NWs) sandwiched between multilayer graphene (MLG) and polyimide (PI) films. By modifying the gas flow dynamics and surface chemistry of the Cu surface during graphene growth, a highly crystalline and uniform MLG film was obtained on the Cu foil, which was then directly coated on the Ag-NW networks to serve as a barrier material. It was found that the highly crystalline layers in the MLG film compensate for structural defects, thus forming a perfect barrier film to shield Ag NWs from oxidation and sulfurization. MLG/w-Ag-NW composites were then embedded into the surface of a transparent and colorless PI thin film by spin-coating. This allowed the MLG/w-Ag-NW/PI composite to retain its original structural integrity due to the intrinsic physical and chemical properties of PI, which also served effectively as a binder. In view of its unique sandwich structure and the chemical welding of the Ag NWs, the flexible substrate-cum-electrode had an average sheet resistance of ≈34 Ω/sq and a transmittance of ≈91% in the visible range, and also showed excellent stability against high-temperature annealing and sulfurization. [ABSTRACT FROM AUTHOR]

An interdigital transducer structure was fabricated from multilayer graphene on the surface of the Y Z -cut of a LiNbO3 ferroelectric crystal. The multilayer graphene was prepared by CVD method and transferred onto the surface of the LiNbO3 substrate. The properties of the multilayer graphene film were studied by Raman spectroscopy. A multilayer graphene (MLG) interdigital transducer (IDT) structure for surface acoustic wave (SAW) excitation with a wavelength of Λ = 60 μm was fabricated on the surface of the LiNbO3 crystal using electron beam lithography (EBL) and plasma chemical etching. The amplitude–frequency response of the SAW delay time line was measured. The process of SAW excitation by graphene IDT was visualized by scanning electron microscopy. It was demonstrated that the increase in the SAW velocity using graphene was related to the minimization of the IDT mass. [ABSTRACT FROM AUTHOR]

Multilayer graphene (MLG) has attracted considerable attention as an interconnect material owing to its excellent electrical and mechanical properties. Several studies on the formation of MLG on insulators have been reported; however, the process temperature and shape controllability of MLG remain challenging. In this study, we investigated the formation of MLG strips for interconnect via metal-induced layer exchange (LE). The LE of strip-patterned amorphous carbon and Ni formed {002}-oriented high-crystallinity MLG strips at low temperatures (600 °C). While voids were formed inside the strip, continuous MLG was formed at the strip edge, likely due to the remarkable atomic diffusion at the edge. Smaller widths and larger thicknesses of the MLG strip allowed us to form uniform MLG strips without voids, and an electrical conductivity of 1100 S cm–1 was achieved. The technique developed in this study is unique because it overcomes the limitations of conventional MLG fabrication techniques and is promising for MLG interconnect applications. [ABSTRACT FROM AUTHOR]

There has been considerable interest in piezoresistive nanocarbon-loaded polymer films for structural health monitoring, including damage detection and strain monitoring. While good performance has been demonstrated, issues related to practical implementation have received less attention. Here we present sensors made from exfoliated graphite nanoplatelets (xGnP) incorporated into a commercial paint that is applied to Sikorsky aircraft. A formulation and a fabrication method are developed that deliver high piezoresistive strain sensitivity alongside mechanical integrity. At approximately 7 wt% xGnP, the gauge factor in tension is in the range of 30–55, and the effectiveness of the sensors for damage monitoring is demonstrated by the detection of perforations. To obtain a paintable solution, key considerations in choosing the solvent employed for introducing the nanocarbon are compatibility and the ability to keep the nanocarbon suspended, which is achieved using ethyl acetate. The ability to form sensors in situ on aircraft structures requires an uncomplicated method of making robust electrical connections, which is demonstrated here using embedded copper mesh. The strong, often nonlinear, environmental sensitivity of polymer-nanocarbon materials must also be considered in applications; here, increasing temperature and humidity both raise sensor resistance. This work shows that a second, unstrained reference sensor would work well for automatic compensation. Lastly, a method for effecting a repair that employs standard processes and maintains the high gauge factor is demonstrated. With these advances, the paint-xGnP sensors are ready for in-the-field testing on aircraft. [ABSTRACT FROM AUTHOR]

Integrating nanostructured LiFePO4 with carbon substrates is a feasible way to obtain high electrochemical performance for lithium-ion batteries (LIBs). The distribution uniformity of LiFePO4 and contact surface area between LiFePO4 and carbon substrates are crucial for the high electrode performance. In this work, LiFePO4 thin film was synthesized on the flat surface of mechanically exfoliated multilayer graphene (MLG) via chemical deposition of Fe2O3 thin film on MLG and conversion to LiFePO4 by solid phase reaction. To enhance the electrochemical performance, carbon coating and Mn doping were carried out to modify the LiFePO4 thin film. LiFe0.95Mn0.05PO4@C film on MLG (MLG/LiFe0.95Mn0.05PO4@C) exhibits high electrochemical performance. Based on the total mass of the composite, specific discharge capacity of 62.5 mAh g−1 is delivered at a high current density of 10 C. Specific discharge capacity of 126.8 mAh g−1 is maintained after 100 cycles at 0.2 C, exhibiting a capacity retention of 97.5%. This method is suitable for large-scale synthesis of carbon-based LiFePO4 composites at low cost. [ABSTRACT FROM AUTHOR]

Graphene research has developed quite rapidly partially because even a monatomic layer can be visualized with a conventional optical microscope. Although optical properties of multilayer graphene such as optical contrast, reflectance (R), and Raman scattering have been well studied, they are studied independently and the thickness dependence is limited to a rather thin region. In this paper, the evolution of optical properties by thickness from monolayer to multilayer graphene up to 107 nm thick is studied comprehensively. The empirically known change of color of multilayer graphene is confirmed from the R, G and B intensities extracted from the optical images. It is also found that, as far as R for visible light is concerned, multilayer graphene is not necessarily considered as a layered material, and the refractive index for monolayer graphene is applicable even for the thickest multilayer graphene flake in this study. On the other hand, the layered structure and Raman scattering at each layer are essential to reproduce the G-band intensity of Raman scattering (I(G)). Not only the multiple reflection but also the interference of scattered Raman light should be considered for I(G) of multilayer graphene thicker than ∼30 nm.

We investigated gated multilayer graphene with stacking order changes along the armchair direction. We consider that some layers cracked to release shear strain at the stacking domain wall. The energy cones of graphene overlap along the corresponding direction in the k-space, so the topological gapless states from different valleys also overlap. However, these states strongly interact and split due to atomic-scale defects caused by the broken layers, yielding an effective energy gap. We find that for some gate voltages, the gap states cross and the metallic behavior along the stacking domain wall can be restored. In particular cases, a flat band appears at the Fermi energy. We show that for small variations in the gate voltage, the charge occupying this band oscillates between the outer layers. [ABSTRACT FROM AUTHOR]

Field emission (FE) necessitates cathode materials with low work function and high thermal and electrical conductivity and stability. To meet these requirements, we developed FE cathodes based on high-quality wrinkled multilayer graphene (MLG) prepared using the bubble-assisted chemical vapor deposition (B-CVD) method and investigated their emission characteristics. The result showed that MLG cathodes prepared using the spin-coating method exhibited a high field emission current density (~7.9 mA/cm2), indicating the excellent intrinsic emission performance of the MLG. However, the weak adhesion between the MLG and the substrate led to the poor stability of the cathode. Screen printing was employed to prepare the cathode to improve stability, and the influence of a silver buffer layer was explored on the cathode's performance. The results demonstrated that these cathodes exhibited better emission stability, and the silver buffer layer further enhanced the comprehensive field emission performance. The optimized cathode possesses low turn-on field strength (~1.5 V/μm), low threshold field strength (~2.65 V/μm), high current density (~10.5 mA/cm2), and good emission uniformity. Moreover, the cathode also exhibits excellent emission stability, with a current fluctuation of only 6.28% during a 4-h test at 1530 V. [ABSTRACT FROM AUTHOR]

In this study, a multi-layered and bi-directionally excitable plasmon-induced transparency (PIT) device with multiple graphene layers was designed. The PIT window was regulated by controlling the Fermi level of graphene, resulting in an increase in the resonance frequency and dip depth of the PIT transmission valleys with an increase in the Fermi level. Theoretical investigations were then conducted. Subsequently, the influence of interlayer distance, individual component size, and relative positioning of graphene on the performance of PIT was studied. When employed as a biosensor, it could only be utilized under x-polarized TM waves, exhibiting a maximum sensitivity of 8.2THz/RIU. As an optical switch, it exhibited the highest modulation depth of 89.7% at 9.04THz under x-polarized waves, and a maximum modulation depth of 94.6% at 2.8THz under y-polarized waves. This theoretically designed PIT device can have potential applications in both sensors and optical switches. [ABSTRACT FROM AUTHOR]

Graphene/carbon fiber composite laminates were prepared by vacuum assisted resin transfer molding process. The effects of different structural forms of graphene with different mass fractions on the tensile properties of carbon fiber composite laminates were investigated. First, the graphene monolayer and multilayer graphene were distributed evenly into epoxy resin by ultrasonic dispersion. Then, single-layer and multilayer graphene/carbon fiber composite laminates were prepared by vacuum assisted resin transfer molding process. Finally, tensile testing machine was used to test the tensile properties of composite laminates. The results show that when the mass fraction of graphene is 0.03%~0.10%, the tensile properties of the specimens are gradually improved with the increase of the mass fraction of graphene. When the mass fraction of multilayer graphene is 0.03%~0.10%, the tensile properties of the specimens gradually decrease with the increase of the mass fraction of multilayer graphene. [ABSTRACT FROM AUTHOR]

This work investigates the enhancement on lubrication performances of water lubricants by multilayer graphene via molecular dynamics simulation. It is found that the multilayer graphene shows interlaminar sliding in the commensurate or incommensurate pattern and thus contributes to an ultra-low friction. Such ultra-low friction can be degraded by agglomerations of graphene, since these agglomerations complicate spatial behaviors of graphene and limit water diffusions, thus affecting the lubrication performances. Moreover, the synergistic performances of water and multilayer graphene become much more evident than the case with monolayer graphene. In detail, the multilayer graphene can promote water lubricants show multilayer distribution and enhance their local diffusions, and water molecules can induce the overlapping of graphene sheets thus to cause their interlaminar sliding. [ABSTRACT FROM AUTHOR]

The current study applies towards investigate the sintering behavior, microstructure as well as mechanical properties of SiC whisker (SiCw) and multi-layer graphene (MLG) reinforced cemented TiB2 nano-composites fabricated through two-step sintering (TSS), highlighting the critical roles of SiCw and MLG as exceptional strengthening/toughening phases. The sinterability of TiB2–TiC–Ni was somewhat improved as a function of MLG or SiCw incorporation. The addition of SiCw resulted in the grain growth of matrix grains, whereas MLG addition significantly impeded the grain growth of TiB2. TSS is effective in suppressing the grain growth coupled with improving the densification in comparison with conventional sintering (CS). The major toughening mechanisms for SiCw/TiB2–TiC–Ni are SiCw bridging, crack deflection and branching. The major toughening mechanisms for MLG/TiB2–TiC–Ni are MLG bridging/pullout as well as crack deflection/branching/arresting. MLG is a superior reinforcement in comparison with SiCw.

Graphene-coated silicon carbide (SiC@C) core–shell nanostructures have attracted attention in the fields of energy storage and nanoelectronics. In this study, multilayer graphene-coated silicon carbide (SiC) nanowires were obtained through the laser irradiation of a mixture target of graphite powder and silicon (Si) grinding sludge discharged from Si wafer manufacturing. Laser irradiation was performed using an ytterbium (Yb) fiber pulsed laser with a pulse width of 10 ms and a wavelength of 1070 nm with various defocus distances. The effect of laser defocusing on the morphology of the generated nanostructures was investigated. Results showed that nanowires were produced under the defocused conditions, and nanoparticles were observed at the on-focus position. The products obtained under all defocused conditions showed a core–shell structure, and the SiC nanowires were covered by graphene layers. The aspect ratio of the nanowires increased with the defocus distance. Observation of the laser-induced plume using a high-speed camera showed that when the laser was defocused, the plume propagation speed slowed down, and the shape of the plume changed to a swirling vortex. The nanowire formation was closely related to the propagation speed and shape variation of the plume. This successful production of SiC@C core–shell nanowires from Si waste opens up the possibility of the sustainable development of new materials for energy storage and nanoelectronics.Highlights: The shape of the produced nanostructures is changed from nanoparticles to nanowires by defocusing the laser beam. The SiC nanowires have core-shell structures and are covered by multilayer graphene. Under defocused conditions, the plume swirls as a vortex moving at a low speed, thus promoting nanowire growth. [ABSTRACT FROM AUTHOR]

Exploring ceramic-based self-lubricating materials with low coefficient of friction (COF) has become one of the hot directions to advance the service performance and life of high-end equipment. In this work, the tribological properties of multilayer graphene (MLG)/β-Si 3 N 4 whisker (β-Si 3 N 4w)/Si 3 N 4 ceramics were investigated. The effects of load and linear speed on the dry sliding COF were discussed. The friction-reducing and self-lubricating mechanisms of MLG and β-Si 3 N 4w were deeply analyzed according to the wear morphology and mechanical properties of Si 3 N 4 -based ceramics. The friction frequency was proposed to analyze the wear mechanism. Results indicated that MLG and β-Si 3 N 4w led to a breakthrough reduction in COF. At the load of 5–20 N, the COF reached an ultra-low level of 0.04–0.07, which was a further 89.86% lower than the reported studies. The comprehensive enhancement of mechanical properties and the existence of MLG lubricating film were the mainly responsible for the ultra-low COF. The COF of MLG/β-Si 3 N 4w /Si 3 N 4 ceramics raised to 0.24–0.31 at 50–200 mm/s, but it was still 33.88–47.64% lower than that of graphene/Si 3 N 4 ceramics. The increase in COF was attributed to the high wear induced by the raised friction frequency. The furrow wear and adhesive wear were the main wear forms of MLG/β-Si 3 N 4w /Si 3 N 4 ceramics. [ABSTRACT FROM AUTHOR]

Amorphous Fe2O3 has special high electrochemical performance as anode materials of LIBs due to its disorderly arranged atoms. However, the issue of its low intrinsic electric conductivity should be solved rationally and facilely. In this work, amorphous Fe2O3 porous films are chemically deposited on the mechanically exfoliated multilayer graphene (MLG) nanosheets, forming a Fe2O3/MLG/Fe2O3 sandwich nanostructure. The addition of 10 mg of EDTA-2Na is crucial for the formation of amorphous nature and holes in Fe2O3 films on MLG. This composite exhibits better electrochemical performance as LIB anodes than well-crystallized Fe2O3 nanoparticles, amorphous Fe2O3 films without holes and amorphous Fe2O3 isolated nanoparticles on MLG, which are prepared using 0 mg, 5 mg, 20 mg of EDTA-2Na, respectively. The optimized composite delivers a reversible discharge capacity of 1067 mAh g − 1 at 100 mA g − 1 after 100 cycles. Moreover, a capacity of 522 mAh g − 1 is delivered at a high current density of 2 A g − 1 . The high electrochemical performance of the composite is attributed to the amorphous nature and porous film structure of Fe2O3, and well combination of Fe2O3 and highly conductive MLG substrate. A chemical bath deposition method has been developed to synthesize amorphous Fe2O3 films on mechanically exfoliated multilayer graphene (MLG) nanosheets. EDTA is crucial for the crystallization degree and the morphology of Fe2O3. As-prepared amorphous Fe2O3 porous films on MLG showed the best electrochemical performance as LIB anodes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The potential applications of multilayer graphene in many fields, such as superconductivity and thermal conductivity, continue to emerge. However, there are still many problems in the growth mechanism of multilayer graphene. In this paper, a simple control strategy for the preparation of interlayer-coupled multilayer graphene on a liquid Cu substrate was developed. By adjusting the flow rate of a carrier gas in the CVD system, the effect for finely controlling the carbon source supply was achieved. Therefore, the carbon could diffuse from the edge of the single-layer graphene to underneath the layer of graphene and then interlayer-coupled multilayer graphene with different shapes were prepared. Through a variety of characterization methods, it was determined that the stacked mode of interlayer-coupled multilayer graphene conformed to AB-stacking structure. The small multilayer graphene domains stacked under single-layer graphene was first found, and the growth process and growth mechanism of interlayer-coupled multilayer graphene with winged and umbrella shapes were studied, respectively. This study reveals the growth mechanism of multilayer graphene grown by using a carbon source through edge diffusion, paving the way for the controllable preparation of multilayer graphene on a liquid Cu surface. [ABSTRACT FROM AUTHOR]

Realizing industrial‐scale production of HCOOH from the CO2 reduction reaction (CO2RR) is very important, but the current density as well as the electrochemical potential window are still limited to date. Herein, we achieved this by integration of chemical adsorption and electrocatalytic capabilities for the CO2RR via anchoring In nanoparticles (NPs) on biomass‐derived substrates to create In/X−C (X=N, P, B) bifunctional active centers. The In NPs/chitosan‐derived N‐doped defective graphene (In/N‐dG) catalyst had outstanding performance for the CO2RR with a nearly 100 % Faradaic efficiency (FE) of HCOOH across a wide potential window. Particularly, at 1.2 A ⋅ cm−2 high current density, the FE of HCOOH was as high as 96.0 %, and the reduction potential was as low as −1.17 V vs RHE. When using a membrane electrode assembly (MEA), a pure HCOOH solution could be obtained at the cathode without further separation and purification. The FE of HCOOH was still up to 93.3 % at 0.52 A ⋅ cm−2, and the HCOOH production rate could reach 9.051 mmol ⋅ h−1 ⋅ cm−2. Our results suggested that the defects and multilayer structure in In/N‐dG could not only enhance CO2 chemical adsorption capability, but also trigger the formation of an electron‐rich catalytic environment around In sites to promote the generation of HCOOH. [ABSTRACT FROM AUTHOR]

Ni−Fe battery is one of prospective aqueous alkaline batteries due to its high safety, eco‐friendliness and cost‐effectiveness. However, the electrochemical performance of Fe‐based anodes is limited due to the particle aggregation and low electric conductivity. In this work, iron powder is used as a precursor in a chemical bath deposition method. By optimizing the concentration of HNO3, a balanced dissolution‐crystallization process is achieved to obtain uniform Fe2O3 nanospheres in size between 60 and 90 nm, which are separately anchored on ultrasonically prepared multilayer graphene (MLG). This composite delivers specific discharge capacities of 191.1 and 160.8 mAh g−1 at the current densities of 2 and 10 A g−1, respectively. A Ni−Fe battery with the as‐prepared Fe2O3/MLG as anode and Ni(OH)2/MLG as cathode exhibits an energy density of 69.5 Wh kg−1 at a high power density of 3931.6 W kg−1. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a spectral analysis of a Surface Plasmon Resonance (SPR) sensor based on multilayer graphene (MLG) operating as a terahertz refractometer. This device's structure is based on Kretschmann configuration, and the graphene layers are modeled as surface impedances with conductivity described by the Kubo model. The structure's electromagnetic response is obtained from the Generalized Coefficients Model, considering TM excitation performed in a frequency range from 1 to 4Thz. In this approach, we evaluate the sensor response for two, three, four and five layers of graphene, equally doped. To verify the effects of MLG doping, we varied the chemical potential by 0.35eV and 0.70eV. As a result, we present the plasmonic response of the device, verifying the operating frequency range for each case of multilayer graphene. In addition, the sensitivity, FWHM and Figure of Merit (FOM) are calculated to describe the sensor performance in each demonstrated case. From the results presented, we verified that the increase in doping reduces the sensitivity of the sensor, however, it improves its FOM. The validation of the proposed model was carried out from simulations in a software based on the Finite Element Method.

The world is moving rapidly to embrace renewable energy sources. One energy carrier, hydrogen, is a growing player in this field. This study was motivated by a desire to find alternative hydrogen storage mechanisms using processes that are cost effective with low environmental impact and good energy storage efficiency. This paper presents initial research findings on the novel approach of employing the patented RMIT Proton Battery to store atomic hydrogen in a multilayer graphene electrode using an acid electrolyte. This is a very different approach to conventional hydrogen energy storage systems. The paper reveals that one supplier's product achieves a 0.35 wt% reversible hydrogen storage in a multilayer graphene material with 0.35 nm layer separation and a specific surface area of 720 m2/g. [Display omitted] • Multilayer Graphene is a potential material for electrochemical hydrogen storage. • Hydrogen storage of a commercial sample in a Proton Battery unit is reported. • Criteria to synthesise novel electrodes with improved H storage are established. [ABSTRACT FROM AUTHOR]

Multilayer graphene has attracted significant attention because its physical properties can be tuned by stacking its layers in a particular configuration. To apply the intriguing properties of multilayer graphene in various optoelectronic or spintronic devices, it is essential to develop a synthetic method that enables the control of the stacking configuration. This review article presents the recent progress in the synthesis of multilayer graphene by chemical vapor deposition (CVD). First, we discuss the CVD of multilayer graphene, utilizing the precipitation or segregation of carbon atoms from metal catalysts with high carbon solubility. Subsequently, we present novel CVD approaches to yield uniform and thickness-controlled multilayer graphene, which goes beyond the conventional precipitation or segregation methods. Finally, we introduce the latest studies on the control of stacking configurations in bilayer graphene during CVD processes. [ABSTRACT FROM AUTHOR]

In recent years, NbC–Ni cermets has been proposed as a potential substitute for WC-Co cemented carbide in machining and other fields because of its economy and good performance, which has attracted extensive attention of scholars. Research on improving its mechanical properties will help to explore its application potential. Graphene-reinforced NbC–Ni cermets were prepared using a microwave sintering technique, and the effects of multilayer graphene (MLG) on its mechanical properties and microstructure were investigated. The experimental results show that the addition of a certain content of graphene contributes to the densification of the material and inhibits the grain growth. The Vickers hardness, toughness, and bending strength increased and then decreased with an increase in the MLG content. When 0.75 wt% MLG was added, the comprehensive mechanical properties of NbC–Ni cermets were optimal, with a Vickers hardness, fracture toughness, and bending strength of 1297.5 kg/mm2, 18.23 MPa m1/2, and 1464.5 MPa, respectively, which were 12.01%, 38.95%, and 18.97% higher than those without MLG. At low MLG content, the graphene sheet layers were well dispersed in the matrix grain boundaries, whereas graphene agglomerates and pores appeared in cermets with 1 wt% MLG, which degraded their mechanical properties. The strengthening and toughening mechanisms of MLG include grain refinement, large-angle deflection of cracks, crack bridging, and pullout of graphene sheet layers. [ABSTRACT FROM AUTHOR]

In the modern literature, there are practically no data on the electrical characteristics of bituminous binders modified with carbon nanotubes and graphene nanoplates, while they are necessary for the design and development of innovative asphalt pavement compositions sensitive to the super-high-frequency microwave radiation. Contemporary bituminous binders are multi-component systems that may contain polymers, rubbers, synthetic or natural resins, inorganic salts, and even fragrances. As a result of application of modifying additives, bitumen acquires high performance characteristics. A special class of modifiers are micro- and nano-sized electrically conductive fibers and particles (steel wool, carbon fibers, carbon black, carbon nanotubes, graphene nanoplates), the use of which makes it possible to ensure the sensibility of bituminous binders to super-high-frequency microwave radiation and the implementation of the process of healing cracks in an asphalt pavement with its subsequent regeneration. As part of the study, the authors developed an original technique to produce bituminous binders modified with carbon nanotubes and multilayer graphene. Modified bituminous compositions in the concentration range from 0.2 to 6 and from 0.2 to 11 wt. % for multi-walled carbon nanotubes (MWCNT) and multilayer graphene nanoplates (MG), respectively were experimentally obtained. For the first time, the dependence of the specific volume electrical conductivity of bitumen-based nanocomposites on the concentration of nanostructured carbon filler (MWCNT and MG) was researched. The maximum values of electrical conductivity were 4.76×10−4 S/cm and 3.5×10−4 S/cm for nanocomposites containing 6 wt. % MWCNT and 11 wt. % MG, respectively. The study determined the filler volume fractions at the percolation threshold for nanocomposites containing MWCNT and MG. They amounted to 0.22 and 2.18, respectively. The formation of a percolation contour in nanocomposites containing MWCNT occurs at significantly lower filler concentrations compared to bituminous compositions containing MG.

Molecular dynamics simulation is used to study and compare the mechanical properties obtained from compression and tension numerical tests of multilayered graphene with an increased interlayer distance. The multilayer graphene with an interlayer distance two-times larger than in graphite is studied first under biaxial compression and then under uniaxial tension along three different axes. The mechanical properties, e.g., the tensile strength and ductility as well as the deformation characteristics due to graphene layer stacking, are studied. The results show that the mechanical properties along different directions are significantly distinguished. Two competitive mechanisms are found both for the compression and tension of multilayer graphene—the crumpling of graphene layers increases the stresses, while the sliding of graphene layers through the surface-to-surface connection lowers it. Multilayer graphene after biaxial compression can sustain high tensile stresses combined with high plasticity. The main outcome of the study of such complex architecture is an important step towards the design of advanced carbon nanomaterials with improved mechanical properties. [ABSTRACT FROM AUTHOR]

Thickness-controlled multilayer graphene has been attracting wide interest in electronic and spintronic devices due to its tunable electronic structure and spin transport properties. In particular, the strong spin filtering effect in a lattice-matched Ni(111)/multilayer graphene heterostructure provides an ideal platform for developing high-performance spin valves and magnetic tunnel junctions. However, the thickness-controlled synthesis of multilayer graphene on Ni(111) substrates is still a large challenge, which seriously restricts the development of graphene spintronic devices. Here, we report an approximate equilibrium segregation method for large-area multilayer graphene films on Ni(111) substrates by regulating the growth process of carbon dissolution and segregation. The uniformity and coverage of multilayer graphene films are controlled precisely in an atmospheric tube furnace system by modulating the Ni film thickness, gas atmosphere, and cooling rate. Characterization results systematically confirm the production of high-coverage, high-quality multilayer graphene on Ni(111) substrates. This work provides a reliable method for the controllable fabrication of multilayer graphene on single-crystal ferromagnetic substrates, which would contribute to the application of graphene spintronic devices. [ABSTRACT FROM AUTHOR]

In this paper, we present a spectral analysis of a Surface Plasmon Resonance (SPR) sensor based on multilayer graphene (MLG) operating as a terahertz refractometer. This device's structure is based on Kretschmann configuration, and the graphene layers are modeled as surface impedances with conductivity described by the Kubo model. The structure's electromagnetic response is obtained from the Generalized Coefficients Model, considering TM excitation performed in a frequency range from 1 to 4Thz. In this approach, we evaluate the sensor response for two, three, four and five layers of graphene, equally doped. To verify the effects of MLG doping, we varied the chemical potential by 0.35eV and 0.70eV. As a result, we present the plasmonic response of the device, verifying the operating frequency range for each case of multilayer graphene. In addition, the sensitivity, FWHM and Figure of Merit (FOM) are calculated to describe the sensor performance in each demonstrated case. From the results presented, we verified that the increase in doping reduces the sensitivity of the sensor, however, it improves its FOM. The validation of the proposed model was carried out from simulations in a software based on the Finite Element Method. [ABSTRACT FROM AUTHOR]

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Multilayer graphene(MLG) and MLG/Fe2O3composite nanomaterials were prepared by liquid-phase stripping. The prepared MLG, MLG/Fe2O3composite nanomaterials and MLG+Fe2O3mechanically mixed nanomaterials were directly added onto the titanium alloy/steel sliding interface. Subsequently, the dry sliding friction and wear tests were performed, and the friction and wear behavior of TC11 alloys was measured. The X-ray diffractometer, laser Raman spectrometer, scanning electron microscopy, 3D laser scanning microscopy and energy spectrometer were employed to analyze the structure, morphology and component of the worn surface and subsurface for TC11 alloys. The results show that, as for the single additive of MLG, the variation tendency of wear loss and friction coefficient for TC11 alloy is similar to that without any additives. There is only Ti and no other phases on the worn surface. The characteristics of adhesive wear and abrasive wear are presented, which are manifested as plastic tearing, adhesive traces and furrows. Underneath the tribo-layer, there exist a plastic layer, which means that TC11 alloy substrate suffers a plastic deformation during sliding. When MLG/Fe2O3composite nanomaterials and MLG+Fe2O3mechanically mixed nanomaterials are selected as the additives, the wear loss and friction coefficient invariably maintain extremely low values and close to zero, in a certain range of sliding revolutions. There retain the phases of MLG and Fe2O3 on the worn surface. The typical black regions and grey regions are observed, and the tribo-layers are presented a double-layer structure. With an increase of cycles to 25000, the double-layer tribo-layer form with the addition of composite nanomaterials disappear, and the severe wear appears. However, as for the addition of mechanically mixed nanomaterials, the double-layer tribo-layer steadily exists. Therefore, the single addition of MLG is unable to improve the friction and wear properties of titanium alloy. With an addition of MLG to the Fe2O3-contained tribo-layer, a new tribo-layer, i.e. double-layer tribo-layer is formed. This layer simultaneously possesses lubrication and bearing function, resulting in a significant improvement for the friction reduction and wear resistance of titanium alloys. Especially, the titanium alloys present more excellent tribological properties with the addition of mechanically mixed nanomaterials, because of more layers and higher content of MLG in the double-layer tribo-layer.

We employ the random-phase approximation to investigate the effects of temperature and the inhomogeneity of background dielectric on the collective excitations and respective broadening functions in 4-MLG structures. Computations present that the systems have four plasmon modes, corresponding to one in-phase and three out-of-phase oscillations of charged particles. We obtain that plasmon frequency and respective broadening functions behave as increasing functions of temperature with sufficiently large wave vectors. Dissimilarly, in small wave vector regions, the increase in temperature slightly decreases plasmon energy, but further increases in temperature increase this parameter. In addition, as the separation increases, both plasmon frequency and broadening functions significantly reduce, and the inhomogeneity of the dielectric background strongly decreases plasmon energy and its loss. We observe that both temperature and the environment's inhomogeneity should be considered in calculations. • Four plasmon modes exist in the system. • Plasmon frequency and respective broadening functions increases with temperature at sufficiently large wave vectors. • With small wave vector, plasmon energy decreases and then increases with increasing temperature. • As The separation increases, both plasmon frequency and broadening functions significantly decrease. • The inhomogeneity of the dielectric background decreases strongly plasmon energy and its loss. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) of graphene from coal pyrolysis gas provides new ways for both large-scale graphene preparation and high value-added utilization of coal. However, green, efficient and continuous preparation of high-quality multilayer graphene with both good uniformity and ideal structure characteristic remains a great challenge. Herein, we first investigated the influence of main carbonaceous species (CH 4 , C 2 H 6 , C 3 H 8 , CO 2 , and CO) in coal pyrolysis gas on the quality of CVD graphene products. The experimental results indicated that CO 2 and CO have little effect on the growth of graphene, while methane as carbon source is conducive to obtain ideal graphene materials, propane and ethane could also influence structural defects and layer number of graphene products remarkably. On this basis, we designed a mixed gas of methane, ethane, and propane with optimized ratio as simulated coal pyrolysis gas, and successfully prepared high-quality multilayer graphene products on nickel foam from the as-designed simulated coal pyrolysis gas by CVD method. Notably, with a CH 4 :C 2 H 6 :C 3 H 8 ratio of 2:1:1, the graphene products prepared from simulated coal pyrolysis gas outperformed that of raw coal pyrolysis gas in terms of physical structure, layer number, and quality uniformity. The corresponding I 2D /I G value reached 0.97. The graphene growth process and mechanism were investigated and discussed macroscopically and microscopically. This work is of great significance for the intrinsic understanding of CVD growth of graphene from coal pyrolysis gas, and also inspires an efficient and environmentally friendly avenue for high-throughput, uniform production of high-quality graphene materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermal aging behavior of glass fiber reinforced composites has attracted much attention because of its application in elevated temperatures environments. In this study, to improve the thermal aging resistance performance of composites, multilayer graphene was embedded in glass fiber reinforced composites and the damage evolution behaviors of the composites after thermal aging treatments were investigated. The mapping relationship between damage modes and acoustic emission parameters is established by principal component analysis and k‐means clustering methods, then the acoustic emission data were trained by K‐Nearest Neighbor algorithms to obtain a damage modes identification model with positive predictive values above 90%. The results showed that more matrix cracking signals are captured (or matrix cracking accumulation acoustic emission (AE) energy is abruptly raised) at the early stage of loading after 32 days of thermal aging. With the addition of multilayer graphene, the fiber/matrix debonding accumulation AE energy is significantly less than the matrix cracking accumulation AE energy, which is more obvious after thermal aging. Damage initiation and extension obtained by the acoustic emission events help to find the correlation between aging time and interior interface damage mechanism. [ABSTRACT FROM AUTHOR]

In spite of 40 years of experimental studies and several theoretical proposals, an overall interpretation of the complex behavior of the magnetoresistance (MR) of multilayer graphene, i.e. graphite, at high fields (B ≲ 70 T) and in a broad temperature range is still lacking. Part of the complexity is due to the contribution of stacking faults (SFs), which most of thick enough multilayer graphene samples have. We propose a procedure that allows us to extract the SF contribution to the MR we have measured at 0.48 K ≤ T ≤ 250 K and 0 T ≤ B ≲ 65 T. We found that the MR behavior of part of the SFs is similar to that of granular superconductors with a superconducting critical temperature T c ∼ 350 K, in agreement with recent publications. The measurements were done on a multilayer graphene TEM lamella, contacting the edges of the two-dimensional SFs. [Display omitted] [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Research & Development (IJERAD) is the property of International Journal of Engineering Research & Development and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multilayer graphene (MLG) has been proposed as an alternative material for nanometer-wide interconnects. However, it has not been put to practical use, since the process technology that leads to practical use has been immature. Recent advances in MLG processes and applications, such as MLG-capped copper interconnects, the direct deposition of MLG by solid-phase deposition (SPD) at a low temperature, stable intercalation doping to MLG and selective chemical vapor deposition (CVD) of high-crystallinity MLG for inductor and antenna applications are reviewed. Based on these advances, MLG is considered to be approaching the stage of practical application for device metallization and high-frequency devices. Based on the characteristics of MLG as a conductor and recent development trends, the prospects and issues regarding the future practical use of MLG graphene are discussed. [ABSTRACT FROM AUTHOR]

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to overcome the low thermal conductivity of pressure-sensitive adhesives (PSAs), multilayer graphene (MLG) pattern embedded PSA tapes (g-PSAs tapes) were fabricated in this study. First, an acrylic copolymer was synthesized and used as a component of a PSA. The glass transition temperature of the PSA and peel strength of the neat PSA tape were determined as −30 °C and 792 ± 14 gf/25 mm, respectively. Next, g-PSA tapes were fabricated by laminating an uncrosslinked PSA tape onto MLG patterns on a PET film followed by curing. The MLG content of the g-PSA tapes was adjusted with the size of MLG patterns fabricated by using metal masks with various opening sizes. Unlike the neat PSA tape, the peel strength of the g-PSA tapes fluctuated during peeling because of the delamination of the graphene layers. The in-plane thermal conductivity of the stacked g-PSA-2 tape with a graphene content of 21.4 vol% was measured to be 5.51 Wm−1K−1. The mechanical durability of the g-PSA-1 and g-PSA-2 tapes was also measured through a folding test and no delamination of the tapes was observed after 10000 folding cycles. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) and reduced graphene oxide (rGO) have been widely researched as substrates to anchor Fe 2 O 3 nanoparticles. However, both of them suffer from complicated synthesis processes. Multilayer graphene (MLG), simply obtained by ultrasonic exfoliation with graphite, can reduce the cost of actual application due to the facile synthesis. However, it is still a great challenge to anchor Fe 2 O 3 nanoparticles on MLG because of the absence of chemical active sites on its surface. Herein, a chemical deposition method is used to coat highly dispersed ultra-small Fe 2 O 3 nanoparticles on MLG surface. As a comparison, both GO and rGO are also used as substrates to anchor Fe 2 O 3 by the same method. Results show that the oxygen-containing functional groups on substrates have significant effect on the crystal phase and distribution of Fe 2 O 3. A mechanism is thus suggested for the growth of Fe 2 O 3 on MLG, GO and rGO. Among them, the composite of Fe 2 O 3 /MLG shows the highest electrochemical performances for lithium ion battery (LIB) anodes. Specific capacity of 1050 mAh g−1 at 0.1C after 100 cycles are obtained based on the total weight of composite. Low cost, facile synthesis and high electrochemical performances enable Fe 2 O 3 /MLG to be a prospect anode material for LIBs. [ABSTRACT FROM AUTHOR]

Multilayer graphene (MLG) prepared via ultrasonic exfoliation has many advantages such as its low-cost and defect-free nature, high electronic conductivity, and large specific surface area, which make it an apt conductive substrate for TiO2 composites. To synthesize graphene/TiO2 hybrids, traditional methods that greatly depend on the chemical bond of oxygen-containing functional groups on graphene with titanium cations are not applicable due to the absence of these functional groups on MLG. In this work, a facile chemical method is developed to directly deposit TiO2 on the MLG surface without the introduction of chemically active groups. With this method, four types of TiO2 materials, that is pure anatase TiO2 nanoparticles, a mixture of anatase TiO2 nanoparticles and rutile TiO2 nanoflowers, pure rutile TiO2 nanoflowers, and pure rutile TiO2 nanorods, are homogeneously anchored on the MLG surface by controlling the amount of HCl in the reactant. Interestingly, the rutile TiO2 nanorods in the TiO2/MLG composite are assembled by many TiO2 nanowires with an ultra-small diameter and ultra-long length, which provides a better synergetic effect for high performances as LIB anodes than other composites. A specific capacity of 631.4 mAh g−1 after 100 cycles at a current density of 100 mA g−1 is delivered, indicating it to be a valuable LIB anode material with low cost and high electrochemical performances. [ABSTRACT FROM AUTHOR]

Gated trilayer graphene shows an energy gap and three topologically protected gapless states when the stacking order changes from ABC to CBA. Here we investigate such a trilayer, but with a part of the internal layer cut and removed forming a region in trilayer built of only two not connected single graphene layers. We demonstrate that the electronic structure of this region is almost the same as that of the gated trilayer. Curiously, the topological gapless states that appear due to differences in the stacking order of the adjacent trilayers localise mostly in these single graphene layers. Thus, a strong disorder in the internal layer of gated trilayer graphene does not lead to the destruction of its fundamental electronic properties. [ABSTRACT FROM AUTHOR]