Different Contents Of Graphene Research Articles

Effect of Graphene on the Microstructure and Mechanical Properties of WC-Based Cemented Carbide

WC-based cemented carbides were prepared by spark plasma sintering (SPS) of WC-Co-Cr3C2-VC alloy powder by adding different contents of graphene. The phase composition, microstructure, mechanical properties, and magnetic properties of cemented carbide were investigated by means of XRD, SEM, Vickers hardness and fracture toughness tests, and magnetic properties tests. The results showed that the mechanical properties of the specimens show a trend of first increasing and then decreasing with the increase in graphene content. After adding 0.6 wt.% graphene, graphene is uniformly distributed on the substrate in the form of flakes, WC grain size decreases, the hardness of the specimen increases to 2009 HV, the relative density increases to 94.3%, the fracture toughness is 11.72 MPa·m1/2, and the coercivity of the sample is 437.55 Oe. Therefore, cemented carbide with a graphene content of 0.6 wt.% has excellent comprehensive performance (Vickers hardness and fracture toughness).

Self-healing and De-icing Functions of Graphene-carbon Nanotube Synergistic Reinforced Thermoplastic Polyurethane Composites Induced by Current

The integration of structure and function is an important demand for new composite materials in high-technology areas like aerospace, automobile, rail transportation, etc. In this paper, the carbon nanotubes (CNTs) modified graphene (G) reinforced thermoplastic polyurethane (TPU) composites were prepared to improve the interfacial properties of graphene-polyurethane composites and enhance the functionality (self-healing, deicing) of the composites. Firstly, the G-CNT/TPU composites with graphene weight percentages of 1%, 3%, 5%, and 7% were prepared by the solution blending method. Then, the current-induced self-healing behaviors of the composites with prefabricated cracks were studied. Finally, the virgin composite and the healed composite films were tested in tension and the self-healing properties of the CNT-G/TPU composite films. Furthermore, the thermogenic effects of G-CNT/TPU composite with different contents of graphene under various voltages were studied, and the variation of voltage and temperature was obtained. The findings show that the surfaces of the composite films with a graphene content of 1 wt% show little change in temperature and do not have the current repair properties. With the increase in graphene content, the composite film gradually increases in temperature after passing the point and its repair effect also increases, and the repair efficiency of the G-CNT/TPU composite film with 7 wt% graphene content reaches 95%. It also achieves energization and de-icing functions based on its conductive properties. These studies will provide positive guidance for the functionalization of lightweight composites.

Paraffin-Multilayer Graphene Composite for Thermal Management in Electronics

Multilayer graphene-paraffin composites with different contents of graphene (0-10 wt.%) were prepared using an ultra-high shear mixer. The aim is to improve the heat transfer in paraffin wax, which will lead to more-efficient thermal buffering in electronic applications. The multi-layer graphenes obtained by supercritical fluid exfoliation of graphite in alcohol were investigated by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Interesting morphological features were found to be related to the intercalation of paraffins between the multilayer graphene flakes. Thermal properties were also investigated in terms of phase change transition temperatures, latent heat by differential scanning calorimetry and thermal conductivity. It was found that the addition of graphene resulted in a slight decrease in energy storage capacity but a 150% improvement in thermal conductivity at the highest graphene loading level. This phase-change material is then used as a thermal heat sink for an embedded electronic processor. The temperature of the processor during the execution of a pre-defined programme was used as a performance indicator. The use of materials with multilayer graphene contents of more than 5 wt.% was found to reduce the processor operating temperature by up to 20%. This indicates that the use of such composite materials can significantly improve the performance of processors.

Structure formation and physical-mechanical properties of Al-Mg alloy with microadditions of graphene

Composites based on Al-Mg alloy, reinforced with graphene nanofilms, were obtained by in situ synthesis under a layer of salt melt. Using SEM and HRTEM, the morphological and dimensional characteristics of the structural components of composites with different contents of graphene were studied. An experiment on dynamic compression of composites by the Kolsky method was carried out, dynamic properties were measured, and the evolution of a cast structure during high-speed deformation was considered. For the first time, the dynamic properties of composites under loading by plane shock waves have been determined. The dynamic properties of aluminum matrix composites are compared depending on the properties of the non-reinforced alloy.

Synthesis and electrochemical performance of TiNb2O7 nanoparticles grown on electrochemically prepared graphene as anode materials for Li-ion batteries

In this study, the electrochemically exfoliated graphene nanosheets are used as conductive networks to enhance the electrochemical performance of titanium niobium oxide (TNO) nanoparticles as anode for Li-ion batteries (LIBs). The morphological analyses show that without using graphene, the TNO porous microspheres are formed through the self-assembly mechanism. However, by adding different contents of graphene (1, 3, and 5 wt%), the TNO nanoparticles are distributed on the graphene nanosheets. The distribution of the TNO nanoparticles on graphene nanosheets decreases due to the increase in the number of the graphene layer. Accordingly, the effectiveness of graphene nanosheets in enhancing the electrochemical performance of TNO depends on their content. The TNO/3 wt% graphene has the best electrochemical performance among all samples. At 20C, the capacity value of pure TNO is improved by two orders via the addition of 3.0 wt% graphene nanosheets. The capacity retention of the pure TNO at 1C and after 200 cycles is improved by about 25% by the addition of 3.0 wt% graphene nanosheets due to the buffering effect of graphene. However, the higher contents of graphene nanosheets (5.0 wt%) not only cannot improve the properties of TNO but also reduce its capacity.

Low-Temperature Performance of Asphalt Mixtures Modified by Microencapsulated Phase Change Materials with Various Graphene Contents

Microencapsulated phase change materials (PCMs) added to conventional ones can store excessive heat energy and reduce thermal stresses. In this study, melamine–formaldehyde resin phase change microencapsulated PCMs, with different contents of graphene (CG), were added to asphalt mixtures, in order to reduce their low-temperature cracking, induced by thermal stresses. Low-temperature and heat-conducting/storing performance of the obtained mixtures was examined via beam bending tests, semi-circular bending low-temperature performance tests, thermal conductivity tests and volume-specific heat capacity tests. Besides, the prepared asphalt mixtures’ water stability and high-temperature stability values were obtained via freeze-thaw splitting and wheel tracking tests. The low-temperature performance of PCM-modified asphalt mixtures was evaluated via their bending strain energy densities, with one of the PCM-modified asphalt mixtures, namely CGMFPCM3, synthesized by the authors, was 1.7 times higher than that of the common asphalt mixture. Although the dynamic stability of all three PCM-modified mixtures was deteriorated by 68, 50, and 20% compared to the common one, that of CGMFPCM3 still complied with the standard requirement. Thermal conductivity and volume-specific heat capacity of the asphalt mixture at 278.15 K was enhanced by 5 and 43%, respectively, after adding CGMFPCM3. It is recommended for reducing the temperature variation-induced cracking in the asphalt pavement. Thermal conductivity and volume-specific heat capacity can be used for evaluating the temperature-regulating performance of asphalt mixtures.

Electromagnetic Interference Shielding Performances of Graphene Foam/PDMS Force-Sensitive Composites

In this study, a graphene foam/polydimethylsiloxane (GF/PDMS) force-sensitive composite with excellent electrical, mechanical, and electromagnetic interference (EMI) shielding performances was prepared. GF with different contents of graphene was prepared by chemical vapor deposition (CVD) and GF/PDMS composites were prepared by vacuum-assisted impregnation. The electrical test and morphology detection indicated good conductivity and flexibility of the proposed composite. Indeed, the GF/PDMS composite with 0.4 wt% graphene had the highest conductivity (4 S cm−1). The EMI shielding performance of the GF/PDMS composite with 0.4 wt% graphene in the X-band was tested and its EMI shielding effectiveness (SE) was 32 dB. After repeated bending for 10000 times, the EMI SE of the proposed composite exhibited negligible changes. The force sensitivity test showed that the sensitivity of the proposed composite was 8.7 KPa−1 under the tensile strain of 30%–50%. Under the pressure of 600–1000 KPa, the sensitivity of the proposed composite was 0.15 KPa−1. Under the stress of 1000 KPa, the EMI shielding coefficient of the proposed composite was 25 dB, which was reduced by 21.9%. The results demonstrated that GF/PDMS with low filler contents (0.4 wt%) exhibited high conductivity (4 S cm−1), high EMI SE (32 dB), and excellent mechanical properties.

Laminados aeronáuticos multifuncionales y multiesclares con diferentes contenidos en grafeno obtenido por un proceso mecano-químico

This work present the results obtained in the characterization of carbon fiber/epoxy laminates with two singularities: a non-crimp fabric (NCF) was used and the resin was doped with different contents of graphene obtained by a mechanochemical process using carbon nanofibers as starting material. Due to the small lateral size of the graphene particles used, no filtering effect is expected during the laminate manufacturing by RTM. The manufactured panels present a low void content and, in the case of the panel with a graphene content of 0.2 wt.% in the resin, a homogeneous distribution of resin and fiber was obtained along the resin path in the panel during the injection process. The results obtained in the cure evaluation reveal a slight accelerating effect of the cure reaction of the epoxy resin due to the presence of the graphene particles. However, the cure degree and the glass transition temperature of the laminates is very similar. From the mechanical point of view, the interlaminar shear strength increases by 9 % in the panel with graphene/epoxy matrix.

Bi@C Nanospheres with the Unique Petaloid Core-Shell Structure Anchored on Porous Graphene Nanosheets as an Anode for Stable Sodium- and Potassium-Ion Batteries.

Bismuth (Bi) has emerged as a prospective candidate as Na-ion and potassium-ion battery anodes because of its unique advantages of low cost, high theoretical gravimetric capacity (386 mAh g-1), and superior volumetric capacity (3800 mAh cm-3). However, the low electronic conductivity and the huge volume expansion of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinder its practical application. To overcome these issues, we propose a rational design: Bi@C nanospheres with the unique petaloid core-shell structure are synthesized in one step for the first time and then combined with different contents of graphene (GR) nanosheets to form the composites Bi@C@GR. The Bi@C nanospheres with a core-shell structure are beneficial to shortening the transmission path of electrons/ions and reducing the risk from structural rupture of the particles during cycling. In addition, the combination of Bi@C nanospheres and porous GR could greatly improve the conductivity and prevent the aggregation of particles, which is conducive to better cycling stability and rate performance. Consequently, Bi@C@GR-2 presents a superior reversible capacity for sodium storage (300 mAh g-1 over 80 cycles) and potassium storage (200 mAh g-1 over 70 cycles) at 0.1 A g-1. Furthermore, in situ electrochemical impedance spectroscopy and ex situ transmission electron microscopy are carried out to analyze and reflect the kinetic reaction mechanism and the phase change of the Bi@C@GR-2 electrode during the charge/discharge processes.

Effect of graphene modified semi‐conductive shielding layer on space charge accumulation in insulation layer for high‐voltage direct current cable

Space charge accumulation in the insulation layer of high-voltage direct current (HVDC) cable is one of the key factors restricting the development of HVDC cable. The inner semi-conductive layer as an important structure of cable will affect the charge accumulation characteristics in the insulation layer. This work intends to explore the method of modifying the semi-conductive layer with graphene, to suppress charge accumulation in the insulation layer. First, the semi-conductive layer with different contents of Graphene (G) and carbon black (CB) are prepared. Second, the morphology and surface roughness of the cross section are analysed. Further, the effects of the semi-conductive layer on space charge accumulation of the insulation layer are studied by pulsed electro-acoustic method and thermal stimulation depolarisation current method. The experimental results show that a moderate amount of graphene replacing CB can effectively reduce charge accumulation in the insulation layer and inhibit positive temperature coefficient (PTC) effect at the same time. The surface roughness of specimens decreases with the increase of G content from 0 to 3 phr (parts per hundreds of resin), when the CB content decreases from 25 to 10 phr, the surface roughness of specimen increases. The resistivity test shows that doping G can significantly inhibit the PTC effect of the semi-conductive layer. The volume resistivity of the semi-conductive layer decreases with the increase of G content and CB content. In addition, charge accumulation of the insulation layer rises and then drops under the action of the semi-conductive layer.

Graphene으로 개질된 폴리우레탄-에폭시 복합체의 기계적 물성과 Damping 특성

Polyurethane (PU) has received extensive attention in structural engineering due to its excellent mechanical properties and damping properties. In this research, graphene-modified PU-epoxy composites are prepared for the application in structural engineering. The mechanical properties and damping properties of the composites with different contents of graphene are investigated. The damping properties of the composites were also investigated by performing dynamic mechanical analysis (DMA). The results showed that with the increase of graphene content, the tear strength of the composites decreased from 52 to 39 ㎫. Due to the enhancement of appropriate amount of graphene, the tensile strength and elongation at break increase to the maximum value, being 16 ㎫ and 675%, respectively. And DMA tests showed that the damping properties reach the optimal values when the graphene content is 0.2%. The large damping temperature range (ΔT<SUB>0.5</SUB>) is 33 ℃, from -2.9 to 30.1 ℃. The peak of loss factor (η<SUB>max</SUB>) is 0.92 and the integral area (TA) is 36 ℃, much higher than those of the pure PU-epoxy composites. In addition, scanning electron microscopy (SEM) results show that agglomeration appears with higher graphene content.

Bond behavior between graphene modified epoxy coated steel bars and concrete

To study the improvement effect of graphene modified epoxy coating on reinforcement corrosion, the epoxy resin with different content of graphene (the content of graphene was 0%, 0.05% and 0.1%) was prepared, and the anti rust effect of epoxy coating with different content of graphene was studied through experiments. To study the bonding performance between graphene/epoxy coated steel bars and concrete, the central pull-out experiment was carried out. Four different diameters (14 mm, 18 mm, 22 mm, 25 mm), four kinds of coated steel bars (three kinds of graphene modified epoxy coatings and one uncoated) were selected to make the center pull out test specimens. For the three kinds of graphene modified epoxy coatings, the graphene content is 0, 0.05%, 0.1% respectively. The results show that adding a certain amount of graphene into the epoxy coating can improve the corrosion resistance of the coating. The bonding performance between graphene/epoxy coated steel bars and concrete is worse than that of ordinary specimens without coated steel bars. The different content of graphene in epoxy coating has little effect on the bonding performance of epoxy-coated steel bars and concrete. In practical engineering, graphene/epoxy coated steel bars can be applied according to the specifications of ordinary epoxy steel bars.

Thermal conductivity and anti-corrosion of epoxy resin based composite coatings doped with graphene and graphene oxide

In order to improve the heat transfer and corrosion resistance of the coatings, graphene/polyvinyl butyral/epoxy resin (GR/PVB/EP) and graphene oxide /polyvinyl butyral/epoxy resin (GO/PVB/EP) coatings with different contents of graphene (GR) and graphene oxide (GO) were successfully prepared. In this paper, we mainly explore the influence of GR and go doping content on the corrosion resistance of the coating, and the influence of GR and go as two kinds of large layer structure on the corrosion resistance of the composite coating. The OCP curve shows that for the composite coating with the same mass fraction, it is more difficult for the electrolyte ions to reach the metal substrate surface maintained by GR coating at the early stage of corrosion process, indicating that GR coating has a better corrosion protection trend than GO coating. However, the Tafel curve was fitted by the least square method, and the anti-corrosion efficiency of the corresponding coating was calculated. The results show that the GR and GO composite coating with 0.89% mass fraction has higher anti-corrosion efficiency, and the composite coating with 0.89% mass fraction of GO has the highest anti-corrosion efficiency. Compared with the pure EP coating, its anti-corrosion efficiency is as high as 92.57%. The dispersion effect of GR and GO in the substrate is very important to the corrosion resistance of the coating.

Fabrication and Physicochemical Study of B2SA-Grafted Poly(vinyl Alcohol)-Graphene Hybrid Membranes for Dehydration of Bioethanol by Pervaporation.

Tetraethylorthosilicate (TEOS)-crosslinked poly(vinyl alcohol) (PVA) solution was prepared and treated with benzaldehyde 2 sulphonic sodium salt acid (B2SA) for sulfonation. Different contents of graphene were incorporated into B2SA-grafted PVA–TEOS hybrid membrane to improve the membrane stability, mechanical strength, and overall pervaporation performance of the membranes. Membranes were fabricated using the casting technique. Developed membranes were then analyzed for their physicochemical changes by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscope (SEM), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), contact angle analysis (CA), and mechanical strength. The lower d-spacing value observed in WAXD was evidence for the decreased inter-chain distance between the polymer chains. DSC exhibited the enhanced thermal stability of the developed membranes compared to the plane PVA membrane with enhancement in Tg value (106 °C), which was well above the pervaporation experimental temperature. Incorporation of graphene induced higher mechanical strength to the fabricated membranes. Further, the membranes were tested for the pervaporation separation of bioethanol. All the membranes were stable throughout the pervaporation studies, with M-2 G showing the total permeation flux of 11.66 × 10−2 kg/(m2 h) at 30 °C.

Comparative Study on Tribological Behavior of Graphene/Polyimide and Carbon Fibers/Polyimide Composites: A Review

Recently, graphene and carbon fibers have enticed extensive consideration in many scientific fields, they are considered by many scientists to be one of the most promising materials in the 21st century. Due to the uniqueness of their properties was attracted to be used to reinforce polyimide. Impressive graphene properties coupled with those excellent of polyimide composites produced composites materials with good tribological properties, different contents of graphene and its derivatives tend to improve polyimide composites properties particularly friction and wear. Furthermore, nanofillers decorated graphene derivatives showed also an effect on the tribological properties of composites. Carbon fibers coupled with polyimide composites also reviewed and showed a significance in the improvement of the properties of composites materials. The results nanofillers reinforced carbon fibers/polyimide exhibit enhanced tribological properties, which can be applied in various fields. Therefore, this survey article gives an enormous review study of the tribological properties under various conditions of graphene/polyimide and car- bon fibers/polyimide composites. Besides the effects of nanofillers size on tribological properties, preparation, and research challenges were also reviewed.

Magneto‐piezoresistive characteristics of graphene/room temperature vulcanized silicon rubber‐silicon rubber magnetorheological elastomer

AbstractThe effect of graphene with different content on the magneto‐piezoresistive characteristics of graphene/room temperature vulcanized silicon rubber (GR/RTV) magnetorheological elastomer (MRE) was studied, and the relationship between the content of graphene and conductivity of GR/RTV‐MRE was described based on the general effective medium theory. A magneto‐piezoresistive model was established to describe the relationship among resistance, pressure, and magnetic field based on the magnetic dipole and tunneling theory. The samples of GR/RTV‐MRE with different content of graphene were prepared. The experimental platform with magneto‐piezoresistive characteristics controlled by magnetic field was built. The effect of graphene with different content on piezoresistive coefficient of GR/RTV‐MRE was obtained under different magnetic flux density. The experimental results showed that the piezoresistive coefficients of samples with different content of graphene decrease with the increase of magnetic flux density in the range of 0 ~ 80mT. For the same magnetic field, when the volume fraction of graphene is less than 12%, the piezoresistive coefficient is positively correlated with it, when the volume fraction of graphene is more than 12%; the increase of content has little effect on the piezoresistive characteristics. The experimental results are compared with theoretical calculations for correction and error analysis. The results showed that the modified model can well describe the variation of the resistance of GR/RTV‐MRE under magnetic field and pressure.

Comprehensive performance test and analysis of graphene-enhanced chromium-free Dacromet coating

Abstract The proposed work aims to improve the comprehensive properties of the composite coating by adding different content of graphene into the coating solution. Firstly, the formulation of the coating solution was determined by the L16(45) orthogonal test. Secondly, the conventional properties of the coating were tested using the optical microscope and micro-vickers hardness tester. Thirdly, the corrosion resistance of the coating was tested by the rapid ammonium nitrate corrosion test, immersion test, and neutral salt spray test. The changes of the microstructure and composition of the coating before and after corrosion were observed and analyzed using the scanning electron microscope, energy dispersive spectrometer, X-ray diffractometer, and Raman spectrometer, and the Tafel polarization curves and electrochemical impedance spectroscopy of the composite coatings with different graphene contents were tested by electrochemical experiments. The results show that the hardness of the coating increases with the increase in the content of graphene. Graphene intercalates between zinc and aluminum powders in a flaky structure, which reduces the appearance of voids and enhances the protection of chromium-free Dacromet coatings, slows down the penetration of electrolyte solutions and effectively slows down the penetration of corrosive media. The addition of a small amount of graphene can increase the corrosion potential and decrease the corrosion current density of the chromium-free Dacromet coating, the Nyquist low frequency of the coating is higher in the same period and the salt spray resistance of the coating is the best.

Three-dimensional silk fibroin scaffolds incorporated with graphene for bone regeneration.

Porous three-dimensional (3D) silk fibroin (SF) scaffolds were widely applied for bone regeneration and showed excellent biocompatibility and biodegradability. Recently graphene was developed for bone scaffolds due to its osteogenic properties. Thus, we combine the SF and graphene to improve the osteogenic properties of SF scaffolds. In our study, we explored the incorporation of SF scaffolds with graphene to develop osteogenic scaffolds capable of accelerating bone formation. The 3D SF scaffolds were fabricated with different contents of graphene (0, 0.5, and 2%). Fluorescence images showed that the graphene nanosheets were homogeneously dispersed in the SF scaffolds. The addition of graphene affected the microarchitecture of the scaffolds. The G/SF scaffolds were cocultured with rat bone marrow-derived mesenchymal stem cells (rBMSCs) for 21 days. The cell morphology and cell proliferation study suggested that 0 and 0.5% G/SF scaffolds displayed good cell proliferation. In addition, immunofluorescent staining (e.g., osteonectin, osteopontin, and osteocalcin) and ALP activities indicated that the osteogenic properties was more actively exhibited on 0.5% G/SF scaffolds compared with the other groups. Our results indicated that SF scaffolds incorporated with graphene could be an appropriate scaffold for bone tissue engineering.

Synthesis of pineapple slab like morphology of ternary BiVO4/graphene/porphyrin nanocomposite with enhanced visible light photocatalytic activity

In this work, composites of BiVO4 with different contents of graphene are synthesized. Photocatalytic investigations determine that the prepared BiVO4–graphene (BVG) nanocomposite with 0.5% of graphene has higher photocatalytic activity among the synthesized nanocomposites. The photocatalytic efficiency of BVG is 2 times higher than BiVO4. To improve the photocatalytic activity under visible light irradiation, the prepared nanocomposite was photosensitized with porphyrin as strong light harvesting agent. The obtained BVG photosensitized with porphyrin (BVG-P) could completely remove methyl orange dyer in 180 min. Slab-like morphology and the incorporation of porphyrin show to be key factors in high photocatalytic activity of BVG-P.

Effect of multilayer graphene as a reinforcement on mechanical properties of WC-6Co cemented carbide

Different contents of graphene was added to the WC-6Co alloy powder to prepare cemented carbide by low pressure sintering. The microstructure, hardness, transverse rupture strength, fracture toughness and thermal conductivity of cemented carbide were investigated. The results show that graphene was distributed as a reinforcement at the Co phase, WC/WC interface and WC/Co interface. The hardness of the cemented carbide decreased slightly with the increase of graphene content. The transverse rupture strength increased first and then decreased with the increase of graphene content, and reached 2321.2 MPa when the content of graphene is 0.05 wt%. The fracture toughness increased to 13.1 MPa m1/2 after adding 0.05 wt% graphene. The thermal conductivity of the sample with 0.05 wt% graphene was greatly improved. After comprehensive consideration, the cemented carbide with 0.05 wt% graphene has excellent performance and meet the performance indexes of high hardness, strength and toughness.