Graphene-based Composites Research Articles

Graphene Effect on Mechanical Properties of Sandwich Panel for Aerospace Structures

This research examines the mechanical properties of graphene-based polymer composites and Nomex honeycomb sandwich using a new strain sensing technique. Sandwich panels are fabricated individually with glass fibre reinforced polymers (GFRP) and face-sheets having different filler ratios of graphene nanoparticles (GNPs). These graphene nanoparticles are oxidized with (UV-O3) ozone to get graphene oxide (GO) which in turn improves resin matrix interfacial strength. Filler ratios of GO 0.0%, 0.2%, 0.6% and 1.0% by weight of poly-epoxy are fabricated for the face-sheets of composite sandwich panels. Graphene-based strain sensors are synthesized having a concentration of GNPs 5% by weight of polystyrene (PS). The strain sensors are pasted on the sandwich panels and four-point bending of the sandwich beams is performed to predict its flexural strength. The response of composite under different filler ratios of graphene oxide on mechanical properties is inspected during mechanical testing of sandwich panels and the results of (PS-GNPs) strain sensors will be compared with the strains produced during mechanical testing.

Graphene-Based Composites as Catalysts for the Degradation of Pharmaceuticals.

The incessant release of pharmaceuticals into the aquatic environment continues to be a subject of increasing concern. This is because of the growing demand for potable water sources and the potential health hazards which these pollutants pose to aquatic animals and humans. The inability of conventional water treatment systems to remove these compounds creates the need for new treatment systems in order to deal with these class of compounds. This review focuses on advanced oxidation processes that employ graphene-based composites as catalysts for the degradation of pharmaceuticals. These composites have been identified to possess enhanced catalytic activity due to increased surface area and reduced charge carrier recombination. The techniques employed in synthesizing these composites have been explored and five different advanced oxidation processes—direct degradation process, chemical oxidation process, photocatalysis, electrocatalyis processes and sonocatalytic/sono-photocatalytic processes—have been studied in terms of their enhanced catalytic activity. Finally, a comparative analysis of the processes that employ graphene-based composites was done in terms of process efficiency, reaction rate, mineralization efficiency and time required to achieve 90% degradation.

A review of FDM and graphene-based polymer composite

Graphene is a carbon that has a unique structure that is excellent in enhancing mechanical, electrical and thermal properties. The fused deposition modelling (FDM) process is a widely used 3D printing method for its low investment and operating cost. Although the FDM process is cheaper and affordable, yet the printed parts are more fragile compare to other 3D printing methods. This paper covers about FDM process and the type of base materials and filler materials. However, the focus is mainly on ABS and graphene. The mechanical properties of ABS/Graphene polymer composite and application of ABS and graphene in the industry were also discussed. Hence, it proved that graphene enhances the properties of ABS. This study is done to improve polymer-based filaments for future references.

Thermal conductivity and elastic modulus of 3D porous/fractured media considering percolation

Pores, vugs, and cracks configurations affect physical and mechanical properties of porous and fractured (PF) media, specifically the percolations of pores/vugs/cracks trigger the dramatic change of conductive-like properties such as thermal conductivity, diffusivity, elastic modulus of PF media. It has been a key but unresolved issue how to accurately capture the percolation thresholds of these complex networks interacted by anisotropic-shaped pores and cracks, and their quantitative effects on the thermal conductivity and elastic modulus of PF media. This work proposes numerical and theoretical strategies for the accurate determination of percolation thresholds of penetrable spheroidal inclusions over a broad range of aspect ratios κ representing prolate pores (1 < κ ≤ 200), vugs (κ = 1) and oblate cracks (0.001 ≤ κ < 1), and the reliable predictions of effective thermal conductivity, diffusivity, and elastic modulus of PF media. The numerical and theoretical strategies include: (1) an extensive Monte Carlo finite-size scaling analysis (MCFSS) for obtaining the statistical values of percolation threshold of porous and fracture networks with κ from 200 to 0.001; (2) a Padé-type percolation model for predicting the percolation thresholds of penetrable spheroidal inclusions over a broad range of aspect ratios; (3) a continuum percolation-based generalized effective medium theory (CP-GEMT) for predicting effective thermal conductivity, diffusivity, and elastic modulus of PF media over the whole range of volume fractions of spheroidal inclusions, including near the percolation threshold. Comparison with extensive experimental, numerical and theoretical results confirms that the present models are capable of accurately determining the percolation thresholds of porous and fracture networks and the effective thermal conductivity, diffusivity, and elastic modulus of PF media as resemble to conductor-superconductor and insulator-conductor. The models can be regarded as a general theoretical framework to shed light on the intrinsic and complex interaction of components, structures and transport and elastic properties in porous and fracture materials, meanwhile the proposed models can be also well utilized to predict the percolation thresholds of spheroidal carbon nanotubes (CNTs) and graphenes, and the effective transport and elastic properties of CNT-/graphene-based composites.

Advances in the Applications of Graphene-Based Nanocomposites in Clean Energy Materials

Extensive use of fossil fuels can lead to energy depletion and serious environmental pollution. Therefore, it is necessary to solve these problems by developing clean energy. Graphene materials own the advantages of high electrocatalytic activity, high conductivity, excellent mechanical strength, strong flexibility, large specific surface area and light weight, thus giving the potential to store electric charge, ions or hydrogen. Graphene-based nanocomposites have become new research hotspots in the field of energy storage and conversion, such as in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion. Graphene as a catalyst carrier of hydrogen fuel cells has been further modified to obtain higher and more uniform metal dispersion, hence improving the electrocatalyst activity. Moreover, it can complement the network of electroactive materials to buffer the change of electrode volume and prevent the breakage and aggregation of electrode materials, and graphene oxide is also used as a cheap and sustainable proton exchange membrane. In lithium-ion batteries, substituting heteroatoms for carbon atoms in graphene composite electrodes can produce defects on the graphitized surface which have a good reversible specific capacity and increased energy and power densities. In solar cells, the performance of the interface and junction is enhanced by using a few layers of graphene-based composites and more electron-hole pairs are collected; therefore, the conversion efficiency is increased. Graphene has a high Seebeck coefficient, and therefore, it is a potential thermoelectric material. In this paper, we review the latest progress in the synthesis, characterization, evaluation and properties of graphene-based composites and their practical applications in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion.

Machinability studies on Al7075-based hybrid composites reinforced with SiC, graphene and CNT

This experimental study analyses the machinability of two composites namely: 1) Al7075-10%SiC-0.1% grapheme; 2) Al7075-10%SiC-0.1% CNT by turning process using uncoated and diamond-like carbon (DLC) coated carbide inserts. Composites were fabricated through united stir and squeeze casting process with ultra-sonification. The effect of graphene and CNT on cutting force, surface roughness, flank wear, crater wear and chip morphology were quantified and presented. Graphene-based composite, recorded the highest cutting force (383.4 N) followed by CNT-based (318.6 N). Higher surface roughness (0.8519 μm) was observed in CNT-based composite and least in (0.4428 μm) graphene-based. CNT-based composite recorded the highest flank wear (0.3544 mm) and graphene-based observed the least flank wear (0.2253 mm). It was also noted that the presence of graphene showed more influence in the chip morphology. Further, the effect of graphene and CNT reinforcements on the micro-structural properties were also investigated.

Preparation of functionalized graphene/thermal conductive polyurethane films

Graphene/polymer composites have been widely used as thermal conductive materials in electronic equipment. However, the development of advanced graphene thermal conductive composites faces many problems, such as easy agglomeration, high interfacial thermal resistance and poor mechanical properties. In our work, new graphene-based polyurethane thermal conductive composites based on octadecylamine (ODA), graphene and thermoplastic polyurethane were prepared. The thermal conductivity(λ) of the composites reached 1.46W/(mK) with loading 20wt.%mRGO, which was increased by 326.02% compared with that of TPU.

Graphene-based Nanomaterials for Fabrication of ‘Pesticide’ Electrochemical Sensors

At present, graphene is one of the most up-to-date materials and it can be applied for various energy conversion devices and sensor technology. In this review article, our main focus is to summarize the role of graphene and its modified surface leading to develop hybrid nanomaterials and its applications in fabrication of pesticide sensor. Graphene based materials demonstrate exclusive electrochemical and optical properties as well as compatibility to absorb a variety of bio-molecules through π-π stacking interaction and/or electrostatics interaction, which make them ideal material to be employed in sensor application. The role of graphene is very crucial in preparing different unique and desirable hybrid functional composites along with nanoparticles, redox mediators, conducting polymers etc. to improve the performance of the sensors. Therefore, they can be easily used as a suitable material applying in fabrication of electrochemical sensors/ biosensors for the detection of organophosphorous and carbamate pesticides. A number of most recent reported works were discussed in which graphene-based hybrid composites show high sensitivity, good catalytic activity, selectivity towards the determination of pesticide either enzymatically or nonenzymatically. The properties of graphene (exceptional charge transport, thermal, optical, mechanical, high surface area, large pore volume and size, an opened ordered structure) play an important role in pesticide detection.

NANOPARTICLES OF NOBLE METALS ON THE SURFACE OF GRAPHENE FLAKES

Carbon is a spread element that has many different reaction combinations. Obtaining new composite materials based on nanoparticles is a very actual and perspective topic because nanoparticles possess unique properties. These properties are retained and even amplified when nanoparticles are located in various matrixes. Furthermore, nowadays, the creation of graphene-based composites and graphene-related structures is a promising area of synthesis of composite nanomaterials. Previous research has determined that graphene has a unique set of electrophysical, thermal, optical, and mechanical properties. In this study, the synthesis of nanocomposites representing nanoparticles of noble metals (Au, Pd, Rh) on the surface of graphene flakes were carried out, and the study of their composition, structure, physical and chemical properties, and possible applications in catalysis. The immobilization of nanoparticles on the surface of graphene oxide and graphene was developed, and the original method of synthesis of nanocomposite noble metal nanoparticles on the graphene flakes surface using supercritical isopropanol as a reduction agent for the transformation of graphene oxide into graphene was created. The study of physical and chemical properties of the obtained nanocomposites and results of the study of obtained nanocomposites as catalysts for model organic reactions of cross-coupling and hydroformylation showed that it is possible to create the graphene-based nanostructures as effective functional nanomaterials. Research on the synthesis of graphene compounds and its unique physical properties form a promising direction in the chemistry and physics of new inorganic functional materials. The resulting nanocomposites can be used in such branches as electrodes for LEDs and solar cells, field-effect transistors, supercapacitors, sensors, fuel cells.

A Novel Phosphorus/Silicon-Containing Flame Retardant—Functionalized Graphene Nanocomposite: Preparation, Characterization and Flame Retardancy

A novel compound (DOPO-V-PA) containing phosphorus and silicon elements was grafted onto the surface of graphene oxide (GO) to obtain a graphene-based flame retardant (GO–DOPO-V-PA). The structure of GO-DOPO-V-PA was characterized and confirmed by FTIR and XPS spectra. AFM measurements showed that the average height of GO-DOPO-V-PA was thicker than that of GO and that the surface of GO-DOPO-V-PA was not uniform, contrary to the surface of the initiator GO before modification. The thermal stability of GO-DOPO-V-PA was greatly improved by the functionalization of GO with DOPO-V-PA, and the residual char of GO-DOPO-V-PA at 600°C increased from 16.45 (GO) to 61.44 wt %. After GO-DOPO-V-PA was incorporated into epoxy resin (EP), the residual char of EP/GO-DOPO-V-PA was almost 3 wt % higher than that of pure EP and EP/GO. Furthermore, EP/GO-DOPO-V-PA exhibited excellent flame retardancy. Compared to the pure EP and EP/GO, the peak heat release rate (pHRR) and total heat release (THR) of EP/GO-DOPO-V-PA both decreased, which was probably caused by the higher residual char of EP/GO-DOPO-V-PA during combustion. Thus, the flame retardancy of the graphene-based composites was improved with the addition of 2 wt % GO-DOPO-V-PA, which was much less than the previously known flame retardant systems, and the graphene has been demonstrated its excellent performance in the fire safety of the polymer materials.

Magnetic graphene-based nanocomposites as highly efficient absorbents for Cr(VI) removal from wastewater.

Due to the merits of their high adsorption and convenient separation, magnetic graphene-based composites have become a promising adsorbent in terms of wastewater treatment. However, recycling and regeneration properties of magnetic graphene-based composites are still a conundrum, which remains to be resolved. Here, Fe3O4/reduced graphene oxide (RGO) (Fe3O4/RGO) nanocomposites were synthesized by one-step solvent-thermal reduction route and used as adsorbents for water purification. It was encouraging to find that the nanocomposites possessed many intriguing properties in removing of Cr(VI) ions, including high adsorption efficiency and excellent recycling and regeneration property. The results indicated that the magnetic separation process of the Fe3O4/RGO nanocomposites only took less than 5s and the maximum removal efficiency of Cr(VI) reached 99.9% under the optimum experimental conditions. Most significantly, the adsorption rate of Cr(VI) can still be as high as 98.13% after 10cycles and the single recycle quality of the nanocomposites can maintain at more than 80%. As a result, the Fe3O4/RGO nanocomposites could be a potential adsorbent for removing heavy metal ions effectively, especially in environmental protection and restoration.

Study of graphene epoxy composites and its recent development in nano science

Abstract The recent development in graphene had a great impact on the physical and chemical properties of any metals or epoxy composites. Our idea is to form a graphene composite that exhibits optimized properties and characters that meet the requirement of the industry field. This paper is a study about properties of graphene when coated with other metals and the application study of graphene with Nanotechnology. Our aim in this project is to fabricate a graphene-based composite that differs the functional and physical properties of the element based on the specific application of radio wave control that protects the human form being affected. Thus, this application can be achieved through coating the graphene on the required element which results in graphene epoxy composite. Various researches were made on this field, yet the application-based survey is still in progress. Thus, we decided to fabricate the epoxy composites based on graphene oxidation.

Research on CuxSy/CoSz/graphene supercapacitor electrode materials

Multilayer graphene was prepared in this study by microwave burst method. Cu9S5/CoS/graphene and CuS/CoS2/graphene composites were obtained by hydrothermal method to regulate the molecular structure and combination of Cu and Co metal sulfides on graphene substrate. Graphite oxide was doped by hydrothermal method, and then Cu9S5/CoS/graphene composite was prepared by microwave explosion method. Raman, SEM and TEM were used to characterize the self-made graphene. Results showed that the multilayer graphene had a bag-like structure which was beneficial to anchor sulfide. Three graphene-based composites were characterized by scanning electron microscopy, X-ray diffraction, energy spectrum analysis and electrochemical properties. Moreover, results showed that CuS/CoS2/graphene had the best electrochemical performance, and its specific capacity reached 324 F/g when the current density was 1 A · g–1, which was much higher than that of the other two samples. Capacity retention rate, interfacial charge transfer resistance and electrolyte diffusion resistance also have advantages.

A Review of Microscale, Rheological, Mechanical, Thermoelectrical and Piezoresistive Properties of Graphene Based Cement Composite.

Extensive research on functionalized graphene, graphene oxide, and carbon nanotube based cement composites has been carried out to strengthen and overcome the shortcomings of construction materials. However, less literature is available on the pure graphene based cement composite. In this review paper, an in-depth study on a graphene-based cement composite was performed. Various structural forms of graphene and classifications of graphene-based nanomaterial have been presented. The dispersion mechanism and techniques, which are important for effective utilization in the construction industry, are reviewed critically. Micro-scale characterization of carbon-based cement composite using thermogravimetric analysis (TGA), infrared (IR) spectroscopic analysis, x-ray diffractometric (XRD) analysis, and morphological analysis has also been reviewed. As per the authors’ knowledge, for the first time, a review of flow, energy harvesting, thermoelectrical, and self-sensing properties of graphene and its derivatives as the bases of cement composite are presented. The self-sensing properties of the composite material are reported by exploring physical applications by reinforcing graphene nanoplatelets (GNPs) into concrete beams.

Fabrication and properties for novel graphene oxide powder with extra large interlayer spacing and high reactivity

Exfoliation and preparation of large interlayer spacing and reactive graphene oxide (GO) powder are of crucial importance and neck technologies for their applications in polymer composites. Herein, we reported an innovative approach to prepare a large interlayer spacing reactive NCO-GO powder by covalent functionalization of GO with 4,4’-diphenylmethane diisocyanate (MDI). The morphology, microstructure, interlayer spacing, dispersion, and thermal stability of the NCO-GO powder were seriously investigated by FT-IR, XPS, XRD, TEM, TG, and Raman. Interlayer spacing of NCO-GO nanosheets was successfully expanded from 0.83 nm to 2.43 nm after modification, the NCO-GO powder showed better dispersion stability than GO in polar solvents and higher decomposition temperature. The fabricated novel NCO-GO powder showed a great prospect in the future to prepare graphene-based PU composites with significantly enhanced electrical conductivity and mechanical properties of PU elastomer.

MnCO3 on Graphene Porous Framework via Diffusion-Driven Layer-by-Layer Assembly for High-Performance Pseudocapacitor.

Diffusion-driven layer-by-layer (dd-LbL) assembly is a simple yet versatile process that can be used to construct graphene oxide (GO) into a three-dimensional (3D) porous framework with good mechanical stability. In particular, the oxygen functional groups on the GO surface are well retained, providing nucleation sites for further chemical reactions to be performed upon. Therefore, such a scaffold should serve as a promising starting material for creating a wide range of 3D graphene-based composites while maintaining a high accessible surface area. Herein, we demonstrate the use of the porous GO macrostructure derived from dd-LbL assembly for the preparation of graphene-MnCO3 hybrid structures. MnCO3 is a newly reported pseudocapacitive material for supercapacitors; however, its electrochemical performance is hampered by its low electrical conductivity and poor chemical stability. Through reaction between KMnO4 and GO during a hydrothermal process, the surface of the porous scaffold was rendered with uniform MnCO3 nanoparticles. With the reduced graphene oxide (rGO) sheets serving as the conductive backbone, the resultant MnCO3 nanoparticles exhibited a capacitance of 698 F g-1 at a charge/discharge current of 0.5 mA (320 F g-1 for the combined rGO and MnCO3 composite). Furthermore, the electrode maintained 77% of its initial capacity even after 5000 cycles of charge/discharge tests at 20 mA.

Pyridinic N–reduced graphene oxide and ZnO composite synergistically enhance photocatalytic performance

This paper reports the synthesis of nitrogen-doped reduced graphene oxide (N-rGO)/zinc oxide (ZnO) composite photocatalysts by one-step hydrothermal method. Taking urea as the nitrogen source, ammonia is released at high temperature, and reduced graphene oxide (rGO) has a strong adsorption effect on ammonia, which is more conducive to improving the nitrogen doping efficiency in the nitrogen doping process. The results of the dye degradation test showed that when the nitrogen content was 4 wt%, the photocatalytic degradation ability of the catalyst was the best, which was 88% higher than that of pure zinc oxide. The X-ray photoelectron spectroscopy (XPS) test showed that the catalytic effect of the sample dominated by pyridinic nitrogen was significantly improved. Besides, fluorescence tests have confirmed that highly conductive rGO can simultaneously capture or transfer photoelectrons within the system, thereby enhancing the photoelectron migration and reducing the private carrier recombination efficiency. N-rGO could act as an active electron accelerator, induce and enhance synergistic coupling, promote photocatalytic redox reactions, and dramatically improve the photocatalytic ability of modified graphene-based composite.

Graphene/polyamide-6 microsphere composites with high electrical and mechanical performance

The development of innovative methods to prepare graphene-based polymer composites with remarkable properties has become a priority due to the many practical applications of these microstructures. Herein, a new technology was used to fabricate composites by combining graphene materials and polymer microspheres. Polyamide 6 (PA6) microspheres were synthesised by reaction-induced phase separation method, and they were wrapped with few-layer graphene (FLG) or graphene oxide (GO) by exfoliated adsorption method, which allows FLG and GO sheets to form a three-dimensional network structure in the PA6 matrix. Electrical and mechanical characterisation led to a distinct improvement in the properties of PA6 composites, which were superior to traditional graphene/polymer composites. Moreover, the process proposed in this work proved to be an effective method to prepare graphene/polymer composites, suitable for industrial production, and can be extended to other kinds of composites with nanofillers.

Correlating the gradient nitrogen doping and electromagnetic wave absorption of graphene at gigahertz

Nitrogen doping has been proved an effective strategy to improve the microwave absorption performance of graphene. However, the detailed investigations correlating the role of nitrogen dopants with dielectric properties and microwave absorption of graphene has not been available. In this work, the gradient nitrogen doped graphene (NG with 0 wt%, 3.7 wt% and 6.86 wt% N content) were prepared via a facile hydrothermal strategy. The effect of nitrogen dopant on microstructure, morphology, chemical composition, complex permittivity, attenuation factor, impedance matching degree and microwave absorption of graphene were systematically investigated. The electromagnetic characterization and CST simulation results reveal that the moderate N-doped graphene (NG-100) endows the optimal microwave absorbing performance, which was attributed to the moderately introduced dipole polarizations, as well as the better balance between attenuation factor and impedance matching degree. The maximum reflection loss (RLmax) of NG-100 is ∼ -55 dB under 3.2 mm, which is five times higher than that of non-doped graphene. Meanwhile, the effective attenuation bandwidth (EAB: < −10 dB) of NG-100 is up to ∼6.82 GHz under 2.6 mm. More importantly, by correlating gradient N-doped graphene with attenuation factor and impedance characteristics, this work provide an approach to the design and construction of graphene-based composites as efficient microwave absorber for realizing practical applications.

Controlled synthesis of α-Fe2O3@rGO core–shell nanocomposites as anode for lithium ion batteries

The fine shape control of metal oxides nanocrystal and component are the key for the preparation of high-performance metal oxides/graphene nanocomposites. Herein, a simpler and practicable in situ one-pot approach was used to synthetize α-Fe2O3@reduced graphene oxide (rGO) core–shell nanocomposites. By controlling the amount of hydrazine hydrate and GO in reaction system, the shape of α-Fe2O3 nanocrystals can be tailored from spindle gradually to ellipsoid and quasi-sphere, and the thickness of enwrapped rGO can also be finely controlled. The as-prepared α-Fe2O3@rGO core–shell composites showed much better lithium storage performance than bare α-Fe2O3 nanocrystals. Owing to the core–shell structure and the high conductivity and stability of rGO nanosheet, the quasi-sphere-α-Fe2O3@rGO composites delivered a high reversible specific capacity up to 971 mAh g−1 at the current density of 0.2 A g−1, retaining 530 mA h g−1 at 2 A g−1 and 361 mA h g−1 at 5 A g−1 after 800 cycles with only 0.05% decay per-cycle. Moreover, the facile approach can provide a new strategy for the fabrication of other shape-size dependent, functional, and multicomponent graphene-based composites.