Decorated Graphene Hybrid Research Articles

Phosphorous‐nitrogen‐boron decorated graphene hybrid for flame retardancy enhancement of epoxy resin

AbstractSoaring development in widely applicable materials raises an urgent demand to develop high‐performance epoxy resin (EP) materials combining superior flame retardancy, smoke suppression and mechanical properties. Phosphorus, boron and nitrogen‐containing flame retardants are high potential environmental‐friendly flame‐retardant additives in polymer manufacturing owing to their low toxicity, molecular diversity, and efficient flame resistance. In this paper, a novel additive flame retardant of RGO‐HCCP@MPB compound was fabricated which involved the functionalization of reduced graphene oxide (RGO) with hexachlorocyclotriphosphazene (HCCP), and the simple complexing RGO‐HCCP with melamine phosphate borate (MPB). The prepared RGO‐HCCP@MPB was then directly mixed with EP matrix to evaluate its flame resistance. It found that the addition of RGO‐HCCP@MPB obviously inhibited the heat release and smoke emission behaviors of EP matrix during combustion. With 5 wt% addition of RGO‐HCCP@MPB in EP, the LOI value of EP/RGO‐HCCP@MPB reached up to 28.4%, the peak heat release rate (PHRR) and the total heat release (THR) decreased by 61.1% and 30.5% compared to neat EP, respectively. Furthermore, the flexural strength and flexural modulus of the EP/RGO‐HCCP@MPB were also promoted compared with that of the pure EP. The flame‐retardant mechanism shows that elements of boron (B), nitrogen (N) and phosphorus (P) in RGO‐HCCP@MPB compound play a synergistic role in the enhancement of the flame retardancy of EP in a combustion.

SYNTHESIS AND CHARACTERIZATION OF GRAPHENE SHEETS DECORATED WITH CARBON BLACK BY DIRECT PYROLYSIS OF A MOLASSES–CARBON BLACK MIXTURE AS A POTENTIAL VERSATILE FILLER FOR RUBBER

ABSTRACT A mixture of molasses and carbon black was pyrolyzed in an inert atmosphere, which resulted in graphene of high quality, comprising of three to four layers on average with carbon black particles distributed over the graphene sheets. Molasses is the viscous dark colored slurry which is obtained at the last stage of refinement of sugar from sugarcane, in which sucrose is present as the major chemical component. Carbon black was also used as a substrate for the growth of graphene. The carbon black decorated graphene hybrid nanostructure was thoroughly characterized by different techniques and improved the failure properties of cured styrene butadiene rubber when incorporated into the rubber matrix. Bound rubber content increased by 50% with the hybrid filler compared to carbon black at 45 phr filler loading. The hybrid filler displayed 63% enhancement in the tensile strength at 2 phr filler loading and 86% increase at 45 phr filler loading, compared to the carbon black filled rubbers at the same loading. The vulcanizates containing the novel filler also exhibited improved abrasion resistance, ice traction, and wet traction and decreased rolling resistance compared to the carbon black filled systems. The new filler exhibited fair value of specific capacitance, 127 F/g when incorporated in an uncured rubber latex matrix. The hybrid filler synthesized, characterized, and studied thus can be classified as a versatile smart filler for rubber nanocomposites with a range of functionalities from mechanical reinforcement to electrochemical properties.

Experimental investigation on thermo-physical properties and heat transfer characteristics of green synthesized highly stable CoFe2O4/rGO nanofluid

The application of spinel ferrite decorated graphene hybrids in heat transfer has been limited mostly due to their poor stability in water. This study reports a straightforward strategy to synthesis a cobalt ferrite/reduced graphene oxide (CoFe2O4/rGO) nanocomposite with high water dispersibility characteristics through the treatment of synthesized hybrid material with Gallic acid (GA) as a green agent at room temperature. A π-π interaction between graphene and the aromatic ring of GA results in a suspension with high stability. The structure of the nanocomposite was investigated in detail by FTIR, XRD, TGA, VSM, Raman spectroscopy, FESEM, and TEM. Also, UV–vis spectroscopy is used to examine the stability of the stability of the CoFe2O4/rGO in the base fluid. The highly stable aqueous nanofluids were subsequently prepared from the products. Thermo-physical analyses of nanofluids revealed that the thermal conductivity ratio of ferrofluid prepared by the obtained CoFe2O4/rGO with 0.9 wt.% load of nanoparticles at 60 °C is rose to 1.46. Besides, the convective heat transfer in laminar flow regime conditions which passes a circular tube under uniform heat flux was examined. The nanofluid with the highest load of nanoparticles (0.9 wt.%) shown the maximum enhancement in Nusselt number of 27.8 % at Reynolds number of 1713.

Effect of metal-based nanoparticles decorated graphene hybrids on flammability of epoxy nanocomposites

To overcome the flammability of epoxy resins (EPs), metal-based nanoparticlesdecorated reduced graphene oxide (rGO) hybrids including Ag@rGO, Cu2O@rGOand TiO2@rGO, were synthesized through microwave irradiation technique and subsequently incorporated into EPs. The structure and morphology of the metal-based nanoparticlesdecorated rGO hybrids were characterized by XRD, XPS, TEM and SEM, which confirmed successful synthesis of the hybrid materials. The metal-based nanoparticles were uniformly deposited to the rGO nanosheets, which could avoid re-stacking of graphene nanosheets. The addition of metal-based nanoparticlesdecorated rGO hybrids significantly diminished the flammability of epoxy nanocomposites. Specifically, the Cu2O@rGO/EP nanocomposite showed 50% and 29% reduction in peak heat release rate and total smoke production, respectively. The reduced flammability was attributed to the improved char yield that restrained the heat and smoke release during combustion. It is prognosticated that metal-based nanoparticles decorated graphene hybrids will provide an efficient solution to improve fire safety of polymeric materials.

Cu(0) and Cu(II) decorated graphene hybrid on improving fireproof efficiency of intumescent flame-retardant epoxy resins

To explore the synergism and mechnism of diverse forms of copper-decorated graphene on improving the fireproof efficiency of ammonium polyphosphate (APP) based polyamide-cured epoxy resin (EP), Cu(0) and Cu(II) decorated graphene hybrids (Cu2+-GO, Cu-rGO and CuO-GNS) were prepared through facile methods and used as synergists in EP/APP system. Cu2+-GO exhibits better synergistic effect with APP than Cu-rGO and CuO-GNS on reducing heat release of EP. Because Cu2+ is easier than Cu and CuO to go through various oxidation states and intermediates, which catalyze EP/APP system rapid formation of protective char layer containing crosslinked junctions of P (V) organic phosphates and Cu (II) salts. CuO-GNS exhibits better smoke suppression and harmful gases reduction in EP/APP matrix, such as aliphatic hydrocarbons, aromatic compounds and CO, due to its better conversion of CO to CO2 through a redox cycle. This work provides a promising strategy for preparation of EP with excellent flame retardancy and smoke suppression at low addition.

Enhanced performance in multilayer-structured nanocomposites using BaTiO3 and Ba0.8Sr0.2TiO3 decorated graphene hybrids

It is challenging to achieve high energy density in conductive fillers/polymer nanocomposites due to their extremely low breakdown strength. In this paper, a novel multi-component and multilayer-structured nanocomposite was designed and investigated, consisting of Ba0.8Sr0.2TiO3 decorated graphene (BST @ RGO)/poly(vinylidene fluoride-chlorotrifluoroethylene) copolymer (P(VDF-CTFE)) composites (R-Layer) as interlayer, and BaTiO3/P(VDF-CTFE) composites (B-Layer) as surface layer. The multilayer-structured nanocomposites were prepared through layer-by-layer solution casting method. Enhanced breakdown strength, energy density, dielectric constant and low dielectric loss were simultaneously obtained in the nanocomposites by the multilayer structure. The maximum dielectric constant of the composites with multi-layered structure was approximately 14, which was increased by 16.67% compared to the pure P(VDF-CTFE) layer, and the dielectric loss was as low as 0.047 at 1 kHz, even lower than pure P(VDF-CTFE) in frequency range from 10 kHz to 1 MHz. The breakdown strength and energy storage density of BRB-3 nanocomposites with 3 R-Layers reached to 220 kV mm−1 and 6.49 J cm−3, respectively. These results demonstrated that designing multi-component and multilayer-structured nanocomposites was an effective approach to fabricate high performance dielectric nanocomposites.

Preparation of Metal Nanoparticle Decorated Graphene Hybrid Composites: A Review

ABSTRACT:In recent years, the graphene/metal nanoparticles (NPs) hybrids have sparked burgeoning interest in varied application fields due to its unique physicochemical properties. In this paper, we present an overview of preparation methods of the graphene/metal NPs hybrids, which includes some common routes as well as other particular strategies. In addition, we introduce a novel physical route to decorate metal NPs upon graphene sheets. Our expectation is that this review will provide references for the exploitation of emerging preparation technologies, and expand application fields for graphene/metal NPs hybrids in the future.

In-situ synthesis of graphene decorated with nickel nanoparticles for fabricating reinforced 6061Al matrix composites

Graphene has attracted a lot of interest to be used as reinforcement in Aluminum matrix composites (AMCs) on account of its superior mechanical properties. However, the most serious and challenging issues in graphene-reinforced AMCs are that reinforcements are quite difficult to disperse uniformly in metal matrix and ensure intimate interfacial bonding simultaneously. In this work, an ultrafine Ni nanoparticles (NPs)-decorated graphene hybrid (indicated with Ni-NPs@GNP) was firstly synthesized by an in-situ chemical vapor deposition method to improve the wettability between metal and carbon nanophase, then the Ni-NPs@GNP/6061Al composite powders were obtained by dispersing the Ni-NPs@GNP into 6061Al alloy particles via a short time intermittent ball milling process. Finally, the Ni-NPs@GNP/6061Al bulk composites were fabricated through hot-pressing sintering of the composite powders. It was demonstrated that good dispersion of reinforcements was achieved in the Ni-NPs@GNP/6061Al composite coupled with remarkably enhanced interfacial bonding by introducing Ni NPs on the graphene, which resulted in the formation of Al3Ni intermetallic at the interface and thus improved the interfacial adhesion between 6061Al and graphene. As a result, the Ni-NPs@GNP/6061Al composite with 0.7wt% reinforcement exhibited much enhanced mechanical properties, namely, a high yield strength of 140MPa together with a tensile strength of 213MPa can be achieved, which were 75% and 30% higher than that of the monolithic 6061Al, respectively. This work provides an inspiring strategy for fabricating 6061Al composites with adjustable mechanical properties as well as controllable interfacial bonding.

Carbon monoxide gas sensing at room temperature using copper oxide-decorated graphene hybrid nanocomposite prepared by layer-by-layer self-assembly

A sub-ppm-level CO gas sensor based on copper oxide (CuO)-decorated graphene hybrid nanocomposite was reported in this paper. The CuO/graphene hierarchical nanocomposite was successfully deposited on a substrate with interdigital microelectrodes via layer-by-layer self-assembly technique. The morphologies, microstructures and compositions of the as-prepared CuO/rGO film were sufficiently characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The gas sensing properties of the CuO/graphene nanocomposite was investigated at room temperature over a wide range concentration of CO gas from 0.25ppm to 1000ppm. The experimental results exhibited not only an unprecedented detection abilities, but also fast response and recovery times, excellent repeatability, good stability and selectivity. The superior sensing mechanism for the presented sensor was ascribed to the hierarchical porous nanostructure and the formed heterojunction at the interfaces between CuO nanoflowers and rGO nanosheets.

Charge transfer and surface defect healing within ZnO nanoparticle decorated graphene hybrid materials.

To harness the unique properties of graphene and ZnO nanoparticles (NPs) for novel applications, the development of graphene-ZnO nanoparticle hybrid materials has attracted great attention and is the subject of ongoing research. For this contribution, graphene-oxide-ZnO (GO-ZnO) and thiol-functionalized reduced graphene oxide-ZnO (TrGO-ZnO) nanohybrid materials were prepared by novel self-assembly processes. Based on electron paramagnetic resonance (EPR) and photoluminescence (PL) investigations on bare ZnO NPs, GO-ZnO and TrGO-ZnO hybrid materials, we found that several physical phenomena were occurring when ZnO NPs were hybridized with GO and TrGO. The electrons trapped in Zn vacancy defects (VZn(-)) within the core of ZnO NPs vanished by transfer to GO and TrGO in the hybrid materials, thus leading to the disappearance of the core signals in the EPR spectra of ZnO NPs. The thiol groups of TrGO and sulfur can effectively "heal" the oxygen vacancy (VO(+)) related surface defects of ZnO NPs while oxygen-containing functionalities have low healing ability at a synthesis temperature of 100 °C. Photoexcited electron transfer from the conduction band of ZnO NPs to graphene leads to photoluminescence (PL) quenching of near band gap emission (NBE) of both GO-ZnO and TrGO-ZnO. Simultaneously, electron transfer from graphene to defect states of ZnO NPs is the origin of enhanced green defect emission from GO-ZnO. This observation is consistent with the energy level diagram model of hybrid materials.

The effect of metal oxide decorated graphene hybrids on the improved thermal stability and the reduced smoke toxicity in epoxy resins

Metal oxide decorated graphene hybrid materials, Co3O4–graphene and SnO2–graphene, were synthesized for improving the thermal stability and suppressing the smoke in combustion for epoxy resins. Incorporation of metal oxide/graphene hybrids leads to significant thermal stabilization: a 37 and 27 °C increment in the temperature of 5% mass loss is observed for SnO2–graphene/EP and Co3O4–graphene/EP, respectively, compared to that of pure EP. The barrier effect of graphene and the restricted mobility of the polymer chains by metal oxide are believed to be the crucial factor for improving the thermal stability. TG-FTIR analysis shows that the amount of organic volatiles of EP is significantly reduced and the toxic CO is suppressed after incorporating SnO2–graphene or Co3O4–graphene, impling the reduced fire hazards. The synergism between the catalysis effect of metal oxide and the adsorption effect of graphene is the possible mechanism for the smoke suppression.

Noncovalently functionalized pristine graphene/metal nanoparticle hybrid for conductive composites

The combination of metal nanostructures and pristine graphene with high quality is highly expected for many applications. A method for the large-scale production of metal nanoparticle (NP)/pristine graphene hybrid and its conductive polymer composites is presented, by a combinatorial process of noncovalent functionalization of defect-free pristine-graphene with Poly(amidoamine) (PAMAM) dendrimer and the homogenous attachment of metal NPs on graphene surface. Stable PAMAM functionalized graphene nanofluid is achieved when there is the absence of solvents. The graphene sheets in the hybrid preserve the intrinsic structure and homogenous dispersion. Silver NP (AgNP) decorated graphene hybrid with homogenous dispersion is realized by using PAMAM as stabilizing and also reducing agents through thermal reduction method. The hybrid is used as nanoscale filler to generate epoxy-based conductive composites for electrical interconnects due to the combined effects of the excellent electrical conductivity of high-quality pristine-graphene at low percolation threshold and enhanced contacts between the fillers by low temperature sintering of AgNPs. This method could lead to the large-scale production of graphene-based composites for a wide range of applications.

In Situ Synthesis of Photoreduced Au Nanoclusters Decorated-Graphene Hybrid as a High Efficient Electrocatalyst

Au nanoclusters with the uniform size of 2 nm decorated on graphene (AuNCs-G) were successfully fabricated by a green photo-reduction method., The composite was characterized by transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR). This one-pot method is cost-effective and convenient. The as-prepared hybrid is very “clean” as a result of the surfactants and stabilizers free formation process, allowing it to express excellent electrocatalytic ability, which was illustrated by using H2O2 as the target model. The formation mechanism of AuNCs-G was also interpreted by density functional theory (DFT), which was quite different from that of Pd nanoparticles decorated graphene. Lower concentration of AuCl4− is favor of formation of smaller Au particles because graphene only has weak absorbility to Au atoms. This mechanism brings further direction to fabricate other noble metallic nanoclusters decorated graphene hybrids.

Sensitive determination of thymol based on CeO2 nanoparticle–decorated graphene hybrid film

A novel thymol electrochemical sensor based on a CeO2 nanoparticle–decorated graphene hybrid was introduced. The hybrid was characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical behavior of thymol on the CeO2/graphene modified glassy carbon electrode was investigated in pH 7.0 phosphate buffer solution by cyclic voltammetry and differential pulse voltammetry. Compared with the bare glassy carbon electrode, the proposed electrode showed improved analytical performance characteristics in catalytic oxidation of thymol. Under the selective conditions, the modified electrode showed a linear voltammetric response for the thymol within a concentration range of 1.0 × 10−7 to 1.8 × 10−5 mol L−1, and a value of 5.0 × 10−8 mol L−1 was calculated for the detection limit (S/N = 3). Furthermore, good selectivity with high sensitivity was obtained for the determination of thymol in real samples.

Preparation and Characterization of Glycyrrhizin-Graphene Hybrid Materials

A glycyrrhizin decorated graphene hybrid materials (GL-G) was synthesized, which is a layer-to-layer sandwich construction. The results of characterization indicate that a photo induced electron transfer process or efficient energy transferring along the GL-G interface. Furthermore, the as-made hybrid material was used as a modifier of the glassy carbon electrode to construct a sensor (GL-G/GCE). Using p-nitrophenol as a model compound, the novel sensor demonstrated a highly enhanced electrochemical activity for it. The peak current of p-nitrophenol was significantly improved at the sensor.

One-step synthesis of metal nanoparticle decorated graphene by liquid phase exfoliation

A novel method for the fabrication of a metal nanoparticle (NP)–graphene hybrid based on the pristine graphene from liquid-phase exfoliation in organic solvents is essential. In the present work, 1-cyanoethyl-2-ethyl-4-methylimidazole (2E4MZ-CN) was employed as a novel stabilizer for graphene sheets in an acetonitrile solution and simultaneously as a reducing agent for metal NPs deposited on the graphene sheets. A homogeneous pristine graphene dispersion is achieved by sonication of natural graphite in an acetonitrile solution of 2E4MZ-CN. Once exfoliated from natural graphite under sonication, the graphene sheets can be stabilized by 2E4MZ-CN through the π–π interaction. Atomic force microscopy, Raman spectroscopy and transmission electron microscopy (TEM) confirm the presence of monolayer and few-layer graphene sheets. The absence of oxidation or destruction of the sp2 character of the carbon is demonstrated by Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Silver NP (AgNP) decorated graphene hybrid is in situ synthesized during the curing process of epoxy resin. Scanning electron microscopy, X-ray diffraction and TEM show that the small particle size and good distribution of AgNPs are realized due to the stabilization of epoxy network. The synthesized AgNP decorated graphene is used as nanoscale filler to prepare highly conductive epoxy-based composites (4 × 10−5 Ω cm). The low temperature sintering of AgNPs attached on the graphene constructs effective electrical network in the epoxy matrix. This method facilitates the preparation of graphene-based materials for various applications.