Weight Ratio Of Graphene Research Articles

Study on the competition effects between thermal conductivity and viscosity of graphene reinforced octadecane phase change material

In this study, a combination of microscale molecular dynamics (MD)-based and macroscale computational fluid dynamics (CFD)-based simulations are employed to investigate the effects of graphene with varying mass ratios on the thermal conductivity and viscosity of octadecane, revealing the nature of the competition effects of thermal conductivity and viscosity in the heat transfer process. The results show that graphene can significantly increase the average thermal conductivity of octadecane. But when its synergy angle in the direction of heat flux is close to 90°, the thermal conductivity of nanocomposite phase change materials (NCPCMs) is only 0.125 W·(m·K)−1, which is lower than that of pure octadecane by 18.83 %. The viscosity of NCPCMs decreased significantly with the decrease of graphene weight ratio and the increase of temperature, and the viscosity of NCPCMs with 9.15 wt% and 28.71 wt% at different temperatures was 812.65 % (max) and 313.75 % (min), respectively. Finally, the equilibrium point between the thermal conductivity and viscosity competition effects favors the viscosity side as the graphene mass ratio increases. Accordingly, natural convection became more crucial in the heat transfer process as the graphene mass ratio increased. Consequently, NCPCMs with the best heat transfer performance should possess a low graphene mass ratio, which results in a high Rayleigh number, providing them with high synergistic efficiency.

Effect of quinacridone content on the performance of graphene/epoxy coatings

AbstractIn this article, long‐lasting anti‐corrosion graphene/epoxy coatings were successfully prepared using quinacridone as dispersant by solution mixing method. The results showed that quinacridone and graphene can form π–π bonds and improve the dispersibility of each other in epoxy coatings. Mechanical and anti‐corrosion properties of epoxy coatings with different contents of quinacridone and graphene have been tested, the results showed that the optimum weight ratio of graphene to quinacridone was 2:5. The tensile strength of the epoxy coatings with 0.2 wt% graphene and 0.5 wt% quinacridone reached 8.12 MPa, which was 1.44 times of the pure epoxy coatings. Moreover, the impedance modulus of the coatings reinforced with quinacridone and graphene was greater than 1011 Ω·cm2 after being immersed in 3.5 wt% NaCl solution for 140 days, which was two orders of magnitude higher than that of the pure epoxy coatings. We found that the reason for the improved performance of the epoxy coatings was not only that quinacridone improved the dispersibility of graphene in the coatings, but also more importantly, quinacridone adsorbed on the surface of graphene to form scale‐like crystalline structures, which enables graphene to reduce folds and wrinkles, thus giving full play to the shielding effect of graphene against corrosion factors.

Experimental study on the melting heat transfer of octadecane with passively adding graphene and actively applying an electric field

The low thermal conductivity of organic phase change materials (PCMs) has seriously obstructed the performance of thermal latent-heat thermal storage (LHTS) system. For the first attempt, we experimentally studied the phase-change heat transfer characteristics of octadecane inside a horizontal cavity with the passive addition of nano graphene and the active application of an electric field. The effects of nano graphene weight ratio, direct current (DC) voltage magnitude and polarity on melting heat transfer and their corresponding mechanism are then examined. Results are reported for the real-time melting process, the liquid fraction, and the evolution of absorbed energy. The velocity fields obtained by particle image velocimetry (PIV), the temperature fields measured by fiber Bragg grating (FBG) sensors, and the current-voltage curves are reported to reveal the heat transfer enhancement mechanism. The absorbed thermal energy is increased by 33.6% when nano graphene is added alone. A single electric field promotes the energy absorption by 153.5% where electric field driven flow develops. The net charge is generated by the conduction mechanism. For composite PCMs’ melting, the absorbed energy is enhanced by 124.8% at most when the cavity's bottom wall is exposed to -10.0 kV. However, when +10.0 kV is applied to the bottom wall the electrophoretic deposition takes place, and the combined augmentation effect on absorbed thermal energy is 111.2%. The present results provide a reference for improving the LHTS system's performance through sole or synergistic heat transfer enhancement method.

Low-velocity impact behavior and mechanical characteristics of basalt/glass hybrid composites with graphene filler for enhancing aircraft nose tip

The growing need for eco-friendly, reliable, lightweight yet rigid materials for aircraft structures served as the inspiration for this work. The intention of this research is to examine the microdamage effects of a hybrid composite made of basalt/glass fiber infused with graphene, on the low energy drop weight impact test. Four main methods are used, which encompass the fabrication of composites, low-velocity impact testing, methods for evaluating impacted composites using ultrasound nondestructive testing, and a study of damage morphology through a scanning electron microscope. An E-glass fiber(400 GSM) combined with natural basalt fiber in an 8:2 ratio and infusing graphene nanoparticles is manufactured, to develop a more appealing hybrid composite for aviation industries. The samples of hybrid composite, each varying with 1 % and 2 % graphene weight ratio of fillers with the fibers are used. Eight outer layers made of glass fiber and two inner layers of basalt fiber composite are prepared using hand layup and compression molding methods. Different impact energy levels ranging from 5 J to 48 J are applied to study the propagation of the damage in the composite at low-impact velocities (1.5–3 m/s). The impact damage for glass/basalt with 2 wt% graphene was comparatively 24 % less than that of glass/basalt without infused graphene nanoparticles at the highest impact energy, thus proving addition of natural basalt and graphene filler improves the strength of the composites.

Improving the Mechanical Properties, Roughness, Thermal Stability, and Contact Angle of the Acrylic Polymer by Graphene and Carbon Fiber Doping for Waterproof Coatings

A polymeric coating was enlarged by incorporating carbon-based nanofiller such as graphene (GR), graphene oxide, chopped carbon fibers (CF), etc., into the polymer to be utilized for various technological applications. In this framework, the acrylic polymer composites and hybrid coatings were made by casting a combination of acrylic polymer, GR, and CF at room temperature. The polymer hybrids were composed of different ratios (0.25, 0.5, 1, and 2 wt%) of GR or (0.25, 0.5, 1, and 2 wt%) of GR and 5 wt% CF. The morphology, thermal stability, glass transition, decomposition temperature, roughness, and the contact angle of the prepared polymer composites and hybrids were investigated. The roughness of the fabric surface of acrylic polymer composites was found to be greatly reduced as the weight ratio of GR or GR + 5 wt% CF was increased. The greatest contact angle was determined to be 83.07° for hybrids containing 2 wt% GR + 5 wt% CF, whereas the least roughness was recorded for composite containing 2 wt% GR and equals 1.22 μm. The addition of CF to polymers composites increased the roughness and contact angle of acrylic polymer composites. The maximum thermal stability was observed for acrylic polymer + 2 wt% GR + 5 wt% CF composites. The maximum value of the impact strength was observed for acrylic polymer hybris containing 1 wt% GR + 5 wt% CF. The Shore A hardness was steadily increased with increasing GR or GR + 5 wt% CF in the hybrid’s polymer. The presence of GR or Gr and CF in the formed hybrids polymers has resulted in an improvement in the mechanical properties, wettability, thermal stability, and hydrophobicity, and hence might be employed for waterproofing coatings.

Enhanced Mechanical Property of Acrylic Polymer/Graphene/Carbon Fibers Hybrid for Water Proof Coating

In this work, some mechanical properties of the polymer coating were improved by preparing a hybrid system containing Graphene (GR) of different weight percentages (0.25, 0.5, 1, and 2wt%) with 5wt% carbon fibres (CF) and added to a polymer coating by using casting method. The properties were improved as GR was added with further improvement on adding 5wt% of CF. The impact strength of acrylic polymer with GR increases with increasing weight ratio‏‏ of GR; maximum value was obtained when the polymer coating was incorporated with 1wt% GR and 5wt% CF. The impact strength of acrylic polymer with GR and GR/CF composites incorporated with GR at 1wt% and CF at 5wt%. Hardness increase with increasing weight ratio of Gr and a significant improvement was observed at 1wt% GR and 5wt% CF content. The tensile strength increases more significantly than the acrylic polymer with GR and GR/CF composites incorporated with GR at 1wt% and CF at 5wt%. Pull-off strength for the polymer coating with GR and CF was greater than for the acrylic polymer coating.

Sensitivity of the impact performance of nano reinforced sandwich structures to the material and geometrical variations

The low-velocity impact response of sandwich structures with aluminum face sheets and neat or nano-reinforced polypropylene core was studied. A strain-rate dependent micromechanics model (SRDM) was presented in the literature for predicting the dynamic behavior of nano-reinforced polymers. In the present study, the dynamic behavior of nano-reinforced polypropylene was simulated based on SRDM results. The finite element model was validated against the experimental results. It was shown that the results of the simulation performed by the SRDM model were in very good agreement with the experimental data. Then, the proposed finite element model was used for checking the sensitivity of the impact performance of nano-reinforced sandwich structures to the material and geometrical variations. A special sandwich structure with a core of 1 mm thickness and a face thickness of 1 mm was considered as the base structure. Different material and geometrical variations including doubling the thickness of the core or face sheets, a different weight ratio of graphene, and increasing material parameters of the face sheets up to 90%, were undertaken on the base structure. The results of the present study imply that the optimal amount of graphene should not exceed 0.5 wt.% to improve impact properties. The impact response of nano-reinforced sandwich structures was more sensitive to the variations of the face thickness in comparison to the variations of the core thickness. Moreover, the impact outputs were more sensitive to changes in the yield stress of faces compared to changes in Young’s modulus of faces.

Graphene-Based Nanofluids: Production Parameter Effects on Thermophysical Properties and Dispersion Stability.

In this study, the thermophysical properties and dispersion stability of graphene-based nanofluids were investigated. This was conducted to determine the influence of fabrication temperature, nanomaterial concentration, and surfactant ratio on the suspension effective properties and stability condition. First, the nanopowder was characterized in terms of crystalline structure and size, morphology, and elemental content. Next, the suspensions were produced at 10 °C to 70 °C using different concentrations of surfactants and nanomaterials. Then, the thermophysical properties and physical stability of the nanofluids were determined. The density of the prepared nanofluids was found to be higher than their base fluid, but this property showed a decrease with the increase in fabrication temperature. Moreover, the specific heat capacity showed very high sensitivity toward the graphene and surfactant concentrations, where 28.12% reduction in the property was achieved. Furthermore, the preparation temperature was shown to be the primary parameter that effects the nanofluid viscosity and thermal conductivity, causing a maximum reduction of ~4.9% in viscosity and ~125.72% increase in thermal conductivity. As for the surfactant, using low concentration demonstrated a short-term stabilization capability, whereas a 1:1 weight ratio of graphene to surfactant and higher caused the dispersion to be physically stable for 45 consecutive days. The findings of this work are believed to be beneficial for further research investigations on thermal applications of moderate temperatures.

The influences of graphene and carbon nanotubes on properties of waterborne intumescent fire resistive coating

Mixed carbon materials composed of carbon nanotubes and graphene were applied as fire retardant filler in the fire resistive coating. The fire resistance, thermal stability, water resistance and mechanical properties were investigated respectively. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were used to study the morphology and composition of the carbon chars. The results indicated that the combination of graphene and carbon nanotubes could have a synergistic effect on fire protection and thermal stability. Additionally, when the weight ratio of graphene and carbon nanotubes was 3:1, the coating exhibited “Excellent” fire resistance and flame retardancy index (FRI) was over 10. SEM, EDS, XRD analysis demonstrated that the carbon content of dense carbon layer achieved 40.97% and titanium pyrophosphate was generated. The coating with higher content of graphene exhibited better water resistance, mechanical properties and adhesion level.

FEM Analyses of Low Velocity Impact Response of Sandwich Composites with Nanoreinforced Polypropylene Core and Alu-minum Face Sheets

Sandwich composites with nanoreinforced polypropylene core and aluminum face sheets were studied under low velocity impact using a finite element model. A three dimensional quarter model was implemented to simulate the drop weight impact response of sandwich structures. In order to consider the strain rate dependent behavior of the core and face sheets, the Johnson–Cook material model was used for both of the polypropylene and aluminum layers. Effects of the different weight ratio of nanoparticles, the core thickness and the impactor mass were studied on the impact outputs. Comparing the impact responses of the sandwich structures with different weight ratio of nanoparticles revealed that positioning a polypropylene layer with 0.5% weight ratio of graphene as the core of sandwich panel caused the minimum amounts of damage area and transverse displacement. Adding more amount of nanoparticles did not improved the mechanical response of the sandwich structures. Increasing the impactor mass caused an increase of the contact force and the contact duration. Increasing the core thickness caused a decrease of the contact duration and increase of the contact force. The finite element outputs were well validated against the experimental results.

Balance of catalytic activity and conductivity of Cu2ZnSnS4/graphene counter electrode for dye-sensitized solar cells: using hydrothermal-synthesized kesterite Cu2ZnSnS4 and graphene obtained by product line

The catalytic activity and conductivity of Cu2ZnSnS4/graphene counter electrode for dye-sensitized solar cells (DSSCs) was balanced using hydrothermal-synthesized kesterite Cu2ZnSnS4 and graphene obtained by product line. It was found that the electrocatalytic activity of Cu2ZnSnS4/graphene counter electrode was adjustable by balancing its catalytic activity and conductivity using varied weight ratio of graphene in the composited material of Cu2ZnSnS4/graphene. When the weight percent of graphene was 2% to Cu2ZnSnS4, the catalytic activity and conductivity of Cu2ZnSnS4/graphene counter electrode came to the balanced point, resulting in the best electrocatalytic activity. Under the balanced conditions, the dye-sensitized solar cell devices based on Cu2ZnSnS4/graphene counter electrode show a maximum solar-to-electrical power efficiency of 3.71% (with short-circuit photocurrent density Jsc of 13.24 mA cm−2, open-circuit photovoltage Voc of 0.63 V, and fill factor FF of 0.44), which is higher than that of unbalanced counter electrode. Although the photovoltaic performance of DSSCs based on Cu2ZnSnS4/graphene counter electrode was a little lower than that of DSSCs based on platinum (Pt) counter electrode (4.95%), it is believed that Cu2ZnSnS4/graphene counter electrode would outperform Pt counter electrode by further balancing its catalytic activity and conductivity using higher-quality and more matched Cu2ZnSnS4 and graphene. This strategy to improve the electrocatalytic activity of counter electrode will be helpful for exploring facile synthesis, low-cost, and efficient Cu2ZnSnS4-based composited counter electrode materials.

A new theoretical creep model of an epoxy-graphene composite based on experimental investigation: effect of graphene content

In this paper, the creep behavior of an epoxy-based adhesive reinforced with different weight fractions of graphene up to 0.5 wt% was studied. Creep tests were performed in three stress levels, using the ultimate strength of the neat epoxy as a reference. Results indicated that the presence of graphene up to 0.5 wt% reduces the creep strain and strain rate of the epoxy. However, the dominant behavior in the creep of epoxy–graphene composites is the creep pattern of the neat epoxy. These experimental observations led to development of theoretical creep models to an appropriate creep model for graphene-reinforced composites by introducing a new function of the graphene weight ratio. A scanning electron microscopy analysis indicated that the strong bond between the graphene surface and epoxy matrix limits the mobility of the molecular chains of the neat epoxy and therefore reduces the creep strain.

Pulsed discharge plasma assisted with graphene-WO3 nanocomposites for synergistic degradation of antibiotic enrofloxacin in water

Synergistic degradation of enrofloxacin (EFA) in water by pulsed discharge plasma (PDP) assisted with graphene-WO3 nanocomposites was investigated. The graphene-WO3 nanocomposites with different weight ratio of graphene were prepared by a hydrothermal method, which were characterized by various aspects, such as structure and morphology, chemical bonding state, optical property and electrochemical property. The results showed that graphene could be hybridized with WO3 nanoparticles successfully. Compared to the pure WO3, the specific surface area enhanced and the light absorption range extended in the graphene-WO3 nanocomposites. Moreover, the separation rate of electron–hole pairs accelerated apparently. The result of degradation performance showed that graphene-WO3 nanocomposites significant improved the removal efficiency and first-order kinetic constant of EFA in PDP system. Highest removal efficiency (99.1%) could be obtained with 60 min treatment in PDP system with 3% graphene-WO3 nanocomposite, which was 23.1% higher than that in the sole PDP system. Correspondingly, the synergistic factor could reach 2.82, suggesting that the synergistic effect could be established. In addition, the effect of various factors including catalyst dosage, peak voltage, air flow rate and initial solution concentration on EFA degradation was evaluated. The graphene-WO3 nanocomposite addition further decomposed O3 and improved the generation of OH and H2O2. The mineralization and three-dimensional fluorescence analysis verified that the EFA molecules could be destroyed and lead to the generation of intermediates. Subsequently, the degradation intermediates were identified by liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC). Based on the above analysis, EFA degradation mechanism in the PDP system with graphene-WO3 nanocomposites was proposed finally.

Improving the optoelectrical properties of Cu2ZnSnS4 using gold and graphene nano-fillers

We have investigated photo-response of Cu2ZnSnS4 (CZTS) and have explored ways for enhancing the photo-response and conductivity using suitable nano-compositing strategies. In phase pure CZTS, gold nanoparticles and graphene flakes are used as nanofillers to make nano-composite samples. Photo-response of as-grown CZTS is improved by compositing gold with the observation of Ilight/Idark=1.29. With increasing gold nanoparticle size conductivity improved for CZTS gold composite. Compositing 1% graphene by weight has enhanced the current flow in the CTZS by 125 times. The graphene weight ratio in the composite is limited by absorbance reduction. The demonstrated high-quality CZTS nano-composite samples with improved optoelectrical properties holds tremendous promise for photovoltaic applications.

Flexible and recyclable conductive composite based on few-layered graphene with excellent self-healing capability

Flexible and self-healing conductive materials are highly desired in the development of soft electronics due to their wide applications. Here we report the preparation of a flexible and self-healing conductive composite by simply blending few-layered graphene with poly(dimethylsiloxane)-containing urea segmented copolymer (PDMS-urea) using THF as solvent. The obtained composite materials show excellent electrical conductivity and self-healing capability. The relationship between the conductivity of the composite film and the graphene weight ratio was investigated and the conductivity of composite containing 12 wt% graphene reaches 81.5 S/m. Based on the balanced flexibility and conductivity, the solvent vapor-induced self-healing and material recyclability studies were performed on a 10 wt% graphene doped composite. The severed sample can be readily healed by exposing it to THF vapor at room temperature and the recovery of electrical conductivity comes up to around 95%. Due to the excellent self-healing capability, the composite film cut into tiny pieces can be recycled assisted by THF vapor with only slightly losing its electrical conductivity.

Impact of graphene on the enhancement of electrochemical and photocatalytic performance of Gd2O3 - Graphene nanocomposites

Gadolinium oxide - Graphene (Gd2O3-G) nanocomposites were prepared with different weight ratio of graphene using low temperature solution process. The structural, morphological, electrochemical and photocatalytic properties of the composites were investigated by X-ray diffraction, Raman, FE-SEM, HRTEM, Cyclic voltammetric and photo-degradation analysis. The chemical composition of the composites was studied by elemental mapping analysis using EPMA. The binding states of various elements present in the composites were analyzed by XPS. Cyclic voltammetric studies revealed that the nanocomposite with 5% graphene exhibits the specific capacitance of 26 F g−1, which is higher than that of pure Gd2O3 (18 F g−1). The presence of graphene has greatly enhanced the photocatalytic performance of Gd2O3G composites as the rate of degradation of MB dye is relatively higher in the composites compared to pure Gd2O3. The significant increase in the specific capacitance and rate of degradation of dye suggest that the Gd2O3G is a promising material for energy storage and environmental applications.

Lithium assisted enhanced hydrogenation of reduced graphene oxide-PANI nanocomposite at room temperature

Present study, first time, reveals that lithium and ethylenediamine assisted Benkeser reaction enhanced the hydrogenation process where reduced graphene oxide-PANI (G-PANI) nanocomposites act as storage medium. Varying the weight ratio of graphene and PANI, several samples were synthesized and hydrogenated. The reduced graphene oxide-PANI (G-PANI) and hydrogenated reduced graphene oxide-PANI (HG-PANI) nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectra (FTIR) analysis and thermo gravimetric analysis (TGA). The electrical conductivity with the variation of temperature for the nanocomposites has also been studied. The reduced values of electrical conductivity and percent weight loss in TGA suggested that the hydrogenation occurs. The degree of hydrogenation of reduced graphene oxide-PANI estimated by TGA, revealed 11% (30% reduced graphene oxide-PANI) and 16.04% (50% reduced graphene oxide-PANI), hydrogen storage, which is considerably higher than the reported values of hydrogen storage in individual storage materials like, PANI, graphene and carbon nano tube.

Photocatalytic Degradation of Oxytetracycline by Ternary Mixed Catalyst and Toxicity Assessment Using Boar Sperm.

Response surface methodology was adopted to obtain ternary mixed catalysts of TiO2-loaded ZSM-5 zeolite and graphene. Oxytetracycline was used as challenged toxicant to evaluate the photocatalytic degradation efficiency of the composites. The optimal weight ratio of graphene, TiO2, and ZSM-5 was 1:8:1. The composites were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, fourier transform infrared, N2 adsorption-desorption isotherms, and transmission electron microscope with an energy-dispersive spectroscopy system, etc. Synthesized samples showed high stability and strong visible-light absorption efficiency. The optimal operating conditions of oxytetracycline photocatalytic degradation were achieved over a wide range of pH and temperature. With 0.1 g/L of optimal ternary mixed composite, the photocatalytic degradation of oxytetracycline was nearly reached completion within 150 min at all treatment temperatures at pH 7. Toxicity of degraded oxytetracycline solution was assayed by a boar sperm quality model using fluorescent staining and flow cytometry. During 180 min of photocatalytic treatment, the degraded oxytetracycline solution showed increasing biotoxicity and changed the morphology and function of boar sperm, despite not killing them.

Template-assisted synthesis of NiCoO2 nanocages/reduced graphene oxide composites as high-performance electrodes for supercapacitors.

Here we reported a coordinating etching and precipitating method to synthesize a complex binary metal oxides hollow cubic structure. A novel NiCoO2/rGO composite with a structure of NiCoO2 nanocages anchored on layers of reduced graphene oxide (rGO) were synthesized via a simple template-assisted method and the electrochemical performance was investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy tests as a faradaic electrode for supercapacitors at a graphene weight ratio of 1 wt% (1%). When used as electrode materials for electrochemical capacitors, the NiCoO2/rGO composites achieved a specific capacity of 1375 F g−1 at the current density of 1 A g−1 and maintained 742 F g−1 at 10 A g−1. After 3000 cycles, the supercapacitor based on these nanocage structures shows long-term cycling performance with a high capacity of 778 F g−1 at a current density of 1 A g−1. These outstanding electrochemical performances are primarily attributed to the special morphological structure and the combination of mixed transition metal oxides and rGO, which not only maintains a high electrical conductivity for the overall electrode but also prevents the aggregation and volume expansion of electrochemical materials during the cycling processes.

One-Pot Hydrothermal Synthesis of Hexagonal WO3 Nanorods/Graphene Composites as High-Performance Electrodes for Supercapacitors.

Tungsten oxide (WO3 ) as an electrode material for supercapacitors has always suffered from low capacitance and poor rate capability. In this work, a series of WO3 nanorods/graphene composites with different weight ratios of tungsten oxide nanorods (WO3 NRs) and reduced graphene oxide (rGO) are synthesized successfully through a facile one-pot electrostatic adsorptive hydrothermal method. In these composites, rGO enhances the conductivity, transporting electrons and protons to the WO3 NRs. In addition, rGO can reinforce the structure of the WO3 NRs during frequently occurring redox reactions. At a graphene weight ratio of 1 wt %, the specific capacitance of the WO3 NRs/rGO composite is 343 F g-1 at a current density of 0.2 A g-1 . Compared with pure WO3 as electrodes, the WO3 NRs/rGO composite shows excellent specific capacity, and superior rate performance and cycling stability owing to the combined action of the double layer and pseudocapacitor. This study provides a new convenient approach to promote the electrochemical performance of tungsten oxide.