Graphene Particles Research Articles

Ultrasound-activated TiO2/GO-based bifunctional photoreactive adsorbents for detoxification of chemical warfare agent surrogate vapors

Commercial TiO2 (P25), alone or in the presence of graphite oxide (GO), was exposed to ultrasound treatment (US) with the objective to modify the surface of nanoparticles through introducing defects and chemical heterogeneity, and to build the composite with GO of synergistic features. The obtained materials were extensively characterized using XRD, HR-TEM, TA-MS, FTIR, XPS, potentiometric titration, adsorption of nitrogen, and UV/Vis diffuse reflectance techniques. The results showed that the US treatment/activation led to the formation of defects on the surface of the TiO2 nanoparticles, which were associated with an increase in the amount of terminal hydroxy groups, and which resulted in narrowing of the band gap energy. The composite formed upon the ultrasonic activation contained partially reduced GO particles deposited on the surface of TiO2 aggregates and bonded with the titania phase through its carboxylic groups existing at the edges of small defectous graphene particles, leading to a high volume of mesopores formed between the particles/aggregates of the nanoparticles. The US-treated materials showed a superior bifunctional detoxification performance, to adsorb and photocatalytically decompose vapors of a chemical warfare agent surrogate, as a result of the surface alteration/activation and an increase in the porosity.

Novel dispersion analysis and selective quantification of particulate components in graphene nanoplatelets–polymer–polymer hybrid composites

AbstractUp until now, no standard procedure to analyze and quantify the dispersion of particles in the polymer matrix exists. From the conductive hybrid polymer–polymer–graphene nanoplatelets composites we developed, this article attempts to showcase methodologies to analyze and quantify particle with the use of scanning electron microscopy images and collection of the elemental maps of carbon, oxygen, and nitrogen by energy dispersive spectroscopy (EDS) analysis. Image analysis was performed on the resulting map to extract the area and location data of graphene particles by subtracting elemental maps. Shadowing or charging problem in the images acquired from EDS was overcome by the polished surface and analyzing a sample twice using a novel approach of 180° opposed. Merging the data from the two elemental maps, taken 180° opposed, can be an alternative to the use of polished samples. From these different dispersion analysis approaches, it was possible to quantify different particles and their effects on the properties of the composites.

Porous sandwich ceramic of layered silicon nitride-zirconia composite with various multilayered graphene content

The influence of the various content of the multilayered graphene (MLG) on the structural and mechanical properties of the final bulk porous silicon nitride-zirconia (Si 3 N 4 -ZrO 2 ) based ceramics was investigated. The ceramic composites were prepared in the form of the laminated structure with different (5-30-5 wt% and 30-5-30 wt%) MLG content by hot isostatic pressing. Homogeneous distribution of the MLGs, a completed phase transition from α to β-Si 3 N 4 in case of 5 wt% MLG have been observed. The structural examinations revealed that the multilayered graphene and zirconia particles owing to their different sizes and shapes influenced the porous microstructure evolution and the related mechanical properties of the composites. The sandwich structures enhanced the mechanical properties compared to reference ceramic with 30 wt% MLG. The position of the layer with higher graphene content, high ratio of α/β phase of Si 3 N 4 and higher porosity had crucial effect on the final mechanical properties. • 5 or 30 wt% MLG added porous Si 3 N 4 -ZrO 2 composites were sintered by stacking alternative layers. • The mechanical test of 5-30-5 wt% MLG layers showed 2 or 3 times better properties than structure with 30-5-30 wt% MLG. • The main effect on mechanical properties had the layer with 30 wt% MLG having ∼ 66% porosity and high α /β-Si 3 N 4 ratio. • The layer with 5 wt% MLG resulted friction coefficient ∼ 0.5 and with 30 wt% MLG ∼ 0.7 at scratch test at dry condition.

Tribological behavior of cobalt/graphene composite coatings

Pure cobalt and cobalt/graphene composite coatings were fabricated on St37 steel substrates by using the electrodeposition method. The morphology and microhardness of the coatings were investigated. The tribological behavior of the specimens was evaluated under the normal loads of 5, 10, and 15 N and through the sliding distances of 300, 600, and 900 m at the ambient temperature. SEM images revealed that the graphene particles had been appropriately distributed within the cobalt matrix. Both the cobalt and cobalt/graphene composite coatings had a nodular-pyramidal morphology. However, the morphology of composite coating was finer than that of the pure cobalt film. According to the wear results, both the cobalt and composite coatings exhibited a much better wear behavior compared to the steel substrate. The co-deposition of graphene particles decreased the volume loss and friction coefficient of pure cobalt film. The volume loss increased by the increment of the applied load and sliding distance. However, increasing the normal load decreased the average coefficient of friction in all the samples. The main wear mechanism of all the samples was abrasion, except for the substrate at the high normal loads.

Physiochemical and mechanical properties of reduced graphene oxide–cement mortar composites: Effect of reduced graphene oxide particle size

The use of graphene derivatives to improve the performance of cement mortar composites has received significant attention in recent years. However, because of diversity of graphene derivatives and their properties, which depend on their preparation, it is critical to consider their size, surface chemistry, crystallinity, surface area, and impurity. In particular, there is still lack of understanding on the influence of the graphene particle size on the performance of cement mortar composite. This paper presents the study on the size effect of reduced graphene oxide (rGO) on physiochemical and mechanical properties of cement mortar composites. A series of rGOs with different particle sizes were prepared by different sonication times of 1, 2, 4, 6, and 8 h and then added with optimum dosage of 0.1% to the composites. The mechanical test results revealed that the composite containing rGO with 0.1% dosage and particle size of 169.8 ± 5.8 nm prepared with 4 h sonication time has 53% and 91% higher tensile and compressive strengths at 28 days than the plain cement mortar composite, respectively, which are higher than those obtained by the use of rGO with particle size of 245.0 ± 29.3 nm prepared with 1 h sonication time. This is explained by the higher molecular bonding, hydration degree, and crystallinity of the composite incorporating rGO with a smaller particle size. This study provides a valuable contribution toward better understanding of the influence of rGO particle size on the properties of cementitious composites to optimize their performance.

Enhanced thermal conductivity of epoxy composites by introducing graphene@boron nitride nanosheets hybrid nanoparticles

Polymer composites with high thermal conductivity have promising applications for the thermal management of modern electronic devices. Here, a novel strategy is proposed to enhance the thermal conductivity of epoxy composites by employing a hybrid graphene and boron nitride nanoparticle (GBN). In the GBN, boron nitride nanosheets (BNNSs) tightly adsorb onto the surface of graphene via π-π interactions, and act as bridges for conveying phonons as well as barriers for electrons transporting between adjacent graphene particles. The thermal conductivity and dielectric properties of composites containing GBN are then systematically investigated. The thermal conductivity is significantly enhanced (~140%) in GBN/epoxy composites containing only 5 wt% of GBN. High electrical resistivity (3.05 × 1012 Ω·cm) and low dielectric loss (tanδ < 0.08) are also observed. This study provides important insights into the design and fabrication of highly thermally conductive and electrically insulating composites.

Temperature effect on free vibration response of a smart multifunctional sandwich plate

A smart multifunctional sandwich plate with a wide range of applications can be produced by proper arrangement of its layers. This paper offers a smart multifunctional sandwich plate with one central lightweight porous layer, two middle polymer/graphene nanocomposite layers and two active faces made of a piezoceramic material. The coupled effects of temperature conditions and piezoelectric behavior on the natural frequencies of the proposed smart multifunctional sandwich plate located on elastic foundations have been studied in the current research. For the dispersions of graphene particles and pores inside host layers, different functional profiles have been considered. Moreover, graphene particles and polymeric materials with temperature-dependent material properties have been adopted. The mechanical properties of polymer/graphene nanocomposite are evaluated by employing Halpin-Tsai approach which is modified to capture nanoscale effects. Eventually, the coupled governing eigenvalue equations of the proposed smart multifunctional sandwich plate are derived using a third-order theory called TSDT and are studied by a developed meshless solution. In addition, the effects of graphene, porosity, geometric and foundation aspects on the natural frequency of the proposed smart multifunctional sandwich plate are studied. The results disclose that the natural frequencies of the proposed smart multifunctional sandwich plates are improved by embedding pores in core layer due to the remarkable reduction of structural weight. It is worth noting that nanocomposite layers can completely compensate the structural stiffness reduction caused by embedding pores in the core.

Effect of interface configuration on the mechanical properties and dislocation mechanisms in metal graphene composites

The effect of graphene-metal interface on dislocation gliding and generation is a key element in understanding the mechanical properties of graphene metal-matrix composites. Graphene-metal interfaces can impede the propagation of dislocations, which enhances the mechanical properties, particularly the strength. On the other hand, the presence of such interfaces can also act as the dislocation source in the metal matrix, which can significantly weaken the material properties. This implies that graphene will not always improve the mechanical properties of metals, but alternatively, it can even significantly weaken the properties. Whether graphene acts as a dislocation sink or source primarily depends on the metal-graphene interface and also other pre-existing defects in the matrix. In this paper, we investigate these two opposing effects at the atomistic scale, using Molecular Dynamics (MD) simulations. To study the effect of the interface and to isolate the effects of dislocations from defects, we have reinforced a perfect crystal of nickel with graphene. We found that in the perfect crystal, the graphene in any interface structure acts as a defect and weakens the metal matrix. Each interface structure in the composite has a different effect on the system, and the topfcc structure of the graphene-nickel interface results in the least strength reduction. For graphene particles, apart from the interface, edges can also act as a dislocation nucleation site. We investigated the two edges –Zigzag and Armchair edge of graphene– and found that both the edges cause decrease in mechanical strength. Experimental results (always reported an increase in mechanical strength) are in contradiction to what we found in this work. The reason for this contradiction is that in the real metallic system, defects are already present, and those acts as a dislocation source more readily than the graphene. To verify this, we studied the metallic systems having defects in nickel crystal and the graphene is reinforced. Through these studies, we investigate the conditions in which the strengthening mechanisms overcome the weakening mechanisms, and improvement is observed in the mechanical properties, similar to some of the reported experimental works. Our results shed light on the deformation mechanisms in metal-graphene composites and can be used as a guide in designing and fabricating more efficient metal-matrix composites.

Direct light-induced propulsion of vessels filled with a suspension of graphene particles and methanol

The direct propulsion of glassy capsule filled with solution of methanol and disperse graphene foam (GF) particles under irradiation with infrared LED is reported. The vertical propulsion occurred after irradiation of transparent glassy bottom. The velocity of propulsion was dependent of light irradiation power. It was observed that with irradiation the GF particles moved violently and vertically with direction of lighting. It was found that upon light irradiation there is generated efficiently hydrogen upon solution surface. The mechanism of propulsion effect was discussed in terms of the explosive hydrogen-oxygen reaction.

Graphene Nanoparticles (GNP) nanofluids as key cooling media on a flat solar panel through micro-sized channels

Typically, in a solar-to-electricity energy conversion process from a PV solar panel, this mechanism often accompanied with a creation of by-products which refers to unproductive heat on the surface of PV solar panel. This unwanted heat energy produced will lead to reduction of total effective output of electrical parameters due to the negative inversely proportional relationship between PV temperature and output efficiency. Therefore, it is important to cool the temperature of PV panel relatively in optimizing the output efficiency. This paper is focusing on using state-of-arts nano-sized materials (graphene particles (GNP) in a liquid solution) to achieve the cooling desired. In the previous simulation research carried out on the similar subject, it was found that by having multiple channels with equal volume, the cooling effects will be peaked using graphene nanofluids. This paper presents the experimental setup and fabrication methods using GNP nanofluids as key media in studying the effectiveness of GNP in cooling of a flat solar panel through continuous flowing of GNP nanofluids inside multiple micro-sized channels which were made in direct contact with the exposed backside of the PV solar panel. It is expected that GNP with its enhanced thermo-physical properties compared to water, the cooling efficiency will increase subsequently. Cooling effects due to different pumping flowrates were also being studied respectively.

Cobalt/graphene electrodeposits: Characteristics, tribological behavior, and corrosion properties

Cobalt/graphene composite coatings were electrodeposited from the baths containing 0.1–0.5 g/L graphene particles. The effect of graphene particles on structure, morphology, hardness, tribological behavior, and corrosion of the coatings was studied. The results revealed that the pyramidal morphology of the pure Co film became smaller at low graphene concentrations, and changed to needle-shaped at the high concentrations. The presence of graphene in the composite films resulted in the reduction of the cobalt crystallite size and thereby increased the hardness of the coatings. The hardness of Co/0.2 g/L graphene composite coating was 530 Hv that was about 1.6 times higher than the pure Co film. The composite coatings also had better tribological behavior than the steel substrate and the Co film. The lowest volume loss achieved in a composite coating deposited from a bath with 0.2 g/L graphene particles. The most corrosion resistance samples were those electrodeposited from baths with 0.2–0.4 g/L graphene particles. The corrosion current density of these samples in 3.5 wt% NaCl solution was <1 μA/cm2.

Roles of Graphene Additives in Optimizing the Microstructure and Properties of Ni–Cr–Graphene Coatings

The electrodeposition technique was used to fabricate graphene and Cr particle-reinforced Ni–Cr–graphene coatings. The Rietveld refinement was utilized to analyze the microstructure of Ni deposits in the coatings. The properties including micro-hardness and corrosion behaviors of the coatings were also tested. Results showed that the addition of graphene particles contributed to the dendrite like structure on the surface of the Ni–Cr–graphene coating. The crystallite size and [200] texture of the Ni deposits in the Ni–Cr–graphene coatings were significantly decreased by the graphene particles. The crystallite size of 149.8 nm in the Ni-25–Cr-0–graphene coating was reduced to 35 nm in the Ni-25–Cr-8–graphene coating due to the addition of 8 g/L graphene to the electrolyte. The microstructure evolution of the Ni–Cr–graphene coatings brought about an enhancement in micro-hardness and corrosion resistance of the coatings. The micro-hardness of the coatings was improved from 260.1 HV0.2 of the pure Ni coating to 285.9 HV0.2 of the Ni-25–Cr-0–graphene coating and continually to 461.8 HV0.2 of the Ni-25–Cr-8–graphene coating. In corrosion solution (3.5 wt.% NaCl), the corrosion current (6.22 μA/cm2) of the Ni-25–Cr-0–graphene coating could be decreased by about an order of magnitude through the addition of graphene particles, which was 0.33 μA/cm2 for the Ni-25–Cr-8–graphene coating.

Effect of graphene concentration on tribological properties of graphene aerogel/TiO2 composite through controllable cellular-structure

The microstructure design of the packing is a crucial factor in determining the performances of sealing capacity. Graphene aerogel/TiO2 (GA/TiO2) composites were fabricated by an infiltration method using porous GA as a framework. GA with different pore sizes and morphologies was tuned by changing concentration of graphene. The structural morphology of the graphene layer structure transformed into porous structure as the graphene concentrations increased. In addition, mechanical properties and tribological behaviors of GA/TiO2 composites with different graphene concentrations were comparatively investigated. The results show that the TiO2 particles are more uniformly filled into the GA with higher graphene concentration due to the porous separation effect. Therefore, the GA/TiO2 composites of higher concentrations have a better elongation and mechanical properties. Simultaneously, the tribological behavior is excellent owing to the self-lubricating properties of graphene and tiny TiO2, and the TiO2 cluster can effectively prevent the crack propagation. Moreover, the tribological performance of the GA/TiO2 samples under wet friction conditions is better than that under dry friction conditions due to the self-transport operation of lubricants assisted by the through capillary action, besides the self-lubricating effect of graphene and tiny TiO2 particles.

Artificial neural network based prediction on tribological properties of polycarbonate composites reinforced with graphene and boron carbide particle

Polycarbonate (PC) composites filled with Graphene (up to 10 vol%) and Boron carbide particles (up to 5 vol%) are fabricated by Injection molding and subsequently compressed and quenched. An interactive outcome of incorporated Graphene (C) and Boron carbide particles (B4C) are reported. The lowest wear was prevailed for the composition of PC with 10 vol% C and 5 vol% of B4C. Artificial neural network (ANN) proficiency is employed to predict wear properties of polycarbonate based composites. Frictional coefficient and wear are successfully computed by well trained ANN from the experimental database of Graphene and Boron carbide particles reinforced polycarbonate composite. 3-D plots for the predicted Frictional coefficient and wear as a function of testing conditions and material compositions were constituted. The final results are very much in accord with the measured data. A well trained ANN is anticipated to aid for optimum design of composite materials for consistent parameter studies.

In vitro and in vivo Biological Responses to Graphene and Graphene Oxide: A Murine Calvarial Animal Study.

BackgroundGraphene and its derivatives have recently gained popularity in the biomedical field. Previous studies have confirmed that both the mechanical strength and wear resistance of graphene-containing polyethylene have been greatly improved. Therefore, it is being considered as an alternative for artificial joint replacement liners. Based on the literature, the wear debris generated from the traditional polymers used for orthopedic liners could lead to particle-induced osteolysis and, consequently, failure of joint replacement. However, the biological response of this novel graphene-based polymer is still unclear. Therefore, the current study aimed to investigate the in vitro and in vivo biological effects of graphene and graphene oxide (GO) particles on bone.Materials and MethodsThe biological responses of graphene and GO particles were tested via in vitro and murine calvarial in vivo models. In the in vitro model, murine macrophage cells were mixed with particles and hydrogel and printed into two differently designed scaffolds; the induced proinflammatory cytokines were then tested. In the murine in vivo model, the particle size distribution was measured via SEM, and these particles were then administrated in the calvarial area, referring to our established model. A micro-CT and histological analysis were performed to examine the biological effects of the particles on bone health. The data were analyzed via the one-way analysis of variance to determine the differences between the groups.ResultsBoth graphene and GO induced significantly higher TNF-α and IL-6 secretion compared with the control in the three-dimensional in vitro model. In the murine calvarial in vivo test, the graphene and GO particles increased the bone mass compared with the sham groups in the micro-CT analysis. Bone formation was also observed in the histological analysis.ConclusionIn these in vivo and in vitro studies, the graphene and GO wear debris did not seem to induce harmful biological response effect to bone. Bone formation around the skull was observed in the calvarial model instead. Graphene-containing biomaterials could be a suitable new material for application in orthopedic prostheses due to their benefit of eliminating the risk of particle-induce osteolysis.

Influence of open voltage and servo voltage during Wire-EDM of silicon carbides

The high cost of silicon carbide and its associated difficulties in machining due to high hardness have long been a major hindrance towards successful applications in various industries, ranging from marine to aerospace sectors. This imparts a need to identify a suitable machining process that can machine silicon carbides with ease and at the same time generate complicated profiles. Therefore, the present work is an effort to identify the possibility of machining silicon carbides with wire electrical discharge machining process. In the current work, the silicon carbides being fabricated by rapid hot-pressing technique led to in-situ graphene formation. This graphene particles, in turn, aid the electrical discharge machining process by imparting a higher electron transfer rate through the workpiece. The influence of open voltage and servo voltage on the overall machinability were thoroughly investigated with machining rate, kerf width and surface roughness as the output characteristics. The variation in the intensity of discharge energy with open voltages had a direct influence on the formation of discharge crater which in turn, affected the overall output characteristics. This led to a gradual increase in the machining rate and the associated surface roughness with an increase in the open voltage. On the other hand, the increase in the servo voltage from 25 V to 39 V led to an initial increase in the machining rate which again decreases when the servo voltage further increases to 51 V. This variation in the machining rate was mainly due to the varying concentration of discharge, open and arcing pulses with varying servo voltage, with arcing pulses more dominant in lower servo voltage and open pulses in larger servo voltage. A minimum kerf width in the range of 170 µm was obtained in the present study with a wire tool of diameter 150 µm when the servo voltage was maintained at 25 V. Further, the kerf width was observed to increase with an increase in the servo voltage throughout the considered range. This is mainly due to the higher discharge concentration in the transverse direction as compared to the machining direction with an increase in the servo voltages. Moreover, a rougher machined surface with high debris concentration was observed when machined with lower servo voltages for all the considered open voltages. This behavior is mainly attributed by the high arcing phenomenon and ineffective removal of the eroded debris across the small inter-electrode gap by the dielectric fluid.

A poly(3,4-propylenedioxythiophene)/carbon micro-sphere-bismuth nanoflake composite and multifunctional Co-doped graphene for a benchmark photo-supercapacitor.

Efficient storage of sunlight in the form of charge is accomplished by designing and implementing a photo-supercapacitor (PSC) with a novel, cost-effective architecture. Sulfur (S)- and nitrogen (N)-doped graphene particles (SNGPs) are incorporated in a TiO2/CdS photoanode. The beneficial effects of SNGPs such as the high electrical conductance promoting fast electron transfer to TiO2, a suitably positioned conduction band that maximizes charge separation, and its' ability to absorb red photons translate into a power conversion efficiency of 9.4%, for the champion cell. A new composite of poly(3,4-propylenedioxythiophene)/carbon micro-sphere-bismuth nanoflakes (PProDOT/CMS-BiNF) is integrated with the photoanode to yield the PSC. The photocurrent produced under 1 sun irradiance is directed to the supercapacitor, wherein, the synergy between the faradaic and electrical double layer charge accumulation mechanisms of PProDOT and CMS-BiNF bestows storage parameters of an areal capacitance of 104.6 mF cm−2, and energy and power densities of 9 μW h cm−2 and 0.026 mW cm−2. An overall photo-conversion and storage efficiency of 6.8% and an energy storage efficiency of 72% exhibited by the PSC are much superior to those delivered by a majority of the PSCs reported in the literature on the otherwise highly efficient perovskite solar cell or the expensive Ru dye based solar cells.

An innovative process for dispersion of graphene nanoparticles and nickel spheres in A356 alloy using pressure infiltration technique

AbstractIn this paper, a unique, innovative liquid metal infiltration process for the dispersion of graphene in the aluminum (Al) matrix in the presence of nickel spheres is introduced. The nickel spheres impart a reaction that induces wettability with molten Al, hence facilitating the infiltration of Al encapsulating graphene. Raman spectroscopy shows the two‐dimensional bands, thereby confirming the presence of graphene in the infiltrated composite. The microstructure of the infiltrated composite shows the dispersion of graphene, Al‐silicon eutectic, and a reaction product between nickel and Al around nickel spheres. The sample of composite tested in this study exhibits a high contact angle and hydrophobicity, possibly due to the dispersion of graphene particles on the surface of the samples. This presence of graphene on the surface causes a reduction of wetting by water and a decrease in corrosion rate which is demonstrated by polarization testing results.

Non-isothermal curing kinetics of biocomposite from poly(furfuryl alcohol) and graphene oxide or reduced graphene oxide with different contents of oxygen-groups by DSC

The non-isothermal curing kinetics of furfuryl alcohol (FA) with p-toluenesulfonic acid (p-TSA-2 wt%), two graphene oxides with different content of oxygen and a high thermally reduced graphene oxide at different concentrations (2, 4, 6 wt%) were studied by DSC using four heating rates (5, 7.5, 10 and 15 K min−1). The graphene particles were characterized by infrared spectroscopy, Raman spectroscopy, 13C solid-state NMR, and X-ray photoelectron spectroscopy. The formulations highlighted the importance of the amount of graphene as well as the effect of the oxygen groups on the curing process. The results showed that graphene had a catalytic effect on the polymerization reaction of FA depending on the oxidation degree. FA curing presented two well-defined stages: polycondensation at relatively low temperature, and crosslinking at high temperature. The kinetic parameters of Kamal and Kamal-Chern diffusion models were applied successfully for working with experimental data. The double fitting method was used to determine the kinetic parameters and to establish the kinetics equation.

Cohesive Element Model for Fracture Behavior Analysis of Al2O3/Graphene Composite Ceramic Tool Material

The microstructure model of Al2O3/graphene (AG) composite ceramic tool material is established based on Voronoi tessellation. The cohesive element method was used to simulate the crack growth of AG. The effect of cohesive parameters at the grain boundary of Al2O3 and graphene on the crack propagation was investigated. The results show that the grain strength of graphene is too high, the crack propagation to graphene grains will be hindered and cannot propagate forward. Cracks tend to spread along the paths where the crack propagation drive force was high and the resistance was low. When the interface strength between Al2O3 and graphene was at the weak interface, the crack propagation path and length were relatively straight and short. The average energy release rate G C is 1.042 × 10−3 J/m2, which is 2.4% higher than that of single-phase Al2O3 ceramic tool materials. However, if the interface strength between Al2O3 and graphene was at the strong interface, the crack propagated along graphene particles for a short distance, consuming a large amount of fracture energy. Furthermore, the crack will deflect around graphene grains, which increases the crack propagation length. The average energy release rate G C is 1.039 × 10−3 J/m2, which is 2% higher than that of single-phase Al2O3 ceramic tool materials.