Graphene Sheet Nanocomposites Research Articles

Fe-Fe3C Functionalized Few-Layer Graphene Sheet Nanocomposites for an Efficient Electrocatalyst of the Oxygen Reduction Reaction.

Preparation of a high-efficiency, low-cost, and environmentally friendly non-precious metal catalyst for the oxygen reduction reaction (ORR) is highly desirable in fuel cells. Herein, a Fe–Fe3C-functionalized few-layer graphene sheet (Fe/Fe3C/FLG) nanocomposite was fabricated through the vacuum heat treatment technique using ferric nitrate and glucose as the precursors and exhibited a high-performance ORR electrocatalyst. Multiple characterizations confirm that the nanosized Fe particles with the Fe3C interface are uniformly distributed in the FLGs. Electrocatalytic kinetics investigation of the nanocomposite indicates that the electron transfer process is a four-electron pathway. The formation of the Fe3C interface between the Fe nanoparticles and FLGs may promote the electron transfer from the Fe to FLGs. Furthermore, the Fe/Fe3C/FLG nanocomposite not only exhibits high ORR catalytic activity but also displays desirable stability. Consequently, the obtained Fe/Fe3C/FLG nanocomposite might be a promising non-precious, cheap, and high-efficiency catalyst for fuel cells.

Multifunctional sensing properties of polymer nanocomposites based on hybrid carbon nanostructures

The electrical, mechanical, piezoresistive and thermoresistive properties of polysulfone nanocomposites with a total filler concentration of 1 wt.%, using a hybrid combination of multilayer graphene sheets (GSs) and multiwall carbon nanotubes (CNTs) in various relative proportions are investigated. Nanocomposites with only CNTs presented, by far, the highest electrical conductivity, downplaying the role of GSs to improve the electrical conductivity of CNT nanocomposites. On the other hand, adding amounts of CNTs as small as 25 % of the total weight filler concentration, greatly benefited the electrical conductivity of GS nanocomposites. Mechanical properties were also not significantly benefited from the addition of GSs, but important collaborative effects between both types of fillers were found when the nanocomposites were subjected to tensile strain and variations in temperature, improving the piezo- and thermo-resistive sensitivities of the nanocomposites.

Polypyrrole-modified graphene sheet nanocomposites as new efficient materials for supercapacitors

New polypyrrole (PPy)-graphene sheet nanocomposites have been synthesized after making reduced graphene react with tetrazine derivatives through inverse electron demand Diels–Alder reaction. The modified graphene material contains pyridazine units as demonstrated by X-ray photoelectron spectroscopy. Then this functionalized graphene material was coated on an electrode, and PPy was deposited by electrochemical polymerization. The obtained nanocomposites were characterized by FTIR, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while the electrochemical performances were assessed by cyclic voltammetry, electrochemical impedance spectroscopy and charge–discharge experiments. Symmetrical coin cells were made to measure the capacitance in a two-electrode configuration. Polypyrrole-graphene nanocomposites with 40% PPy show the best electrochemical performances, with a very large capacitance per weight (326 F g−1 at 0.5 A g−1 and 250 F g−1 at 2 A g−1) and a small resistance due to a good ion accessibility, which makes it one of the best electrode materials for supercapacitors so far.

Hydrothermal synthesis of CdS nanoparticle/functionalized graphene sheet nanocomposites for visible-light photocatalytic degradation of methyl orange

CdS nanoparticle/functionalized graphene sheet (CdS NP/FGS) nanocomposites were successfully prepared in a one-step hydrothermal synthesis route. The samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy. In addition, the photocatalytic performance of CdS NP/FGS composites and pure CdS in the degradation of methyl orange (MO) was examined using visible light. Results show that the addition of FGS can enhance the photocatalytic performance of CdS NP/FGS composites with a maximum degradation efficiency of 98.1% under visible light irradiation as compared with pure CdS (60.1%). This finding can be attributed to three reasons. First is the strong redox ability of CdS in the nanocomposite with smaller crystal size. Second is the increase in specific surface area for more adsorbed MO. Third is the reduction in electron–hole pair recombination with the introduction of FGS. Based on their high photocatalytic activity, the CdS NP/FGS composites can be expected to be a practical visible light photocatalyst.

Preparation of CdS/Functionalized Graphene Sheets Nanocomposites and Its Photoelectric Properties

Preparation of CdS/Functionalized Graphene Sheets Nanocomposites and Its Photoelectric Properties

Synthesis of CTAB-intercalated graphene/polypyrrole nanocomposites via in situ oxidative polymerization

PPy (polypyrrole)/CTAB (cetyltrimethylammonium bromide) intercalated graphene sheets nanocomposites (PPy/CGN) were prepared via in situ oxidative polymerization of pyrrole in the presence of CTAB intercalated graphene. The morphology and structure of samples were investigated by FE-SEM (field-emission scanning microscope), TEM (transmitting electron microscopy), UV–vis (ultraviolet and visible spectrum), FT-IR (Fourier transform infrared spectrum), XRD (X-ray diffraction), TGA (thermogravimetric analysis), and four-probe electrical conductivity measurements. The results showed that for the PPy/CGN nanocomposites, the disordered structure of CGN disappeared and CGN existed in the form of individual graphene sheet or stacked layers in PPy matrix. The graphene serves as a support material for nano-sized PPy particles. The CGN covered with PPy nanoparticles were confirmed by FE-SEM and TEM. The electrical conductivity of the PPy/CGN nanocomposite achieved 12.06S/cm for the PPy/CGN-5 sample.

Synthesis of Mn3O4-anchored graphene sheet nanocomposites via a facile, fast microwave hydrothermal method and their supercapacitive behavior

Well-crystallized Mn3O4-anchored reduced graphene oxide (rGO) nanocomposites have been successfully synthesized via a facile, effective, energy-saving, and scalable microwave hydrothermal technique for potential application as supercapacitor material. Integrating these nanostructures resulted in a strong synergistic effect between the two materials, consequently leading to a hybrid composite with higher specific capacitance compared to the bare Mn3O4 nanoparticles. The results from different sorts of characterization indicate that the Mn3O4 particles were deposited and anchored on graphene sheets. The capacitance value of the rGO(31.6%)–Mn3O4 nanocomposite reached 153F/g, much higher than that of the bare Mn3O4 (87F/g) at a scan rate of 5mV/s in the potential range from −0.1V to 0.8V. More importantly, a 200% increase in capacitance was observed for the nanocomposite with cycling at 10mV/s due to electrochemical activation and the oxidization of Mn(II,III) to Mn(IV) during cycling, as verified by X-ray photoelectron spectroscopy. There is no observable capacitance fading up to 1000 cycles. The facile synthesis method and good electrochemical properties indicate that the nanocomposite could be an electrode candidate for supercapacitors.

Fabrication of magnetic Ni nanoparticles functionalized water-soluble graphene sheets nanocomposites as sorbent for aromatic compounds removal

The magnetic Ni nanoparticles functionalized water-soluble graphene sheets nanocomposites (Ni@GSs-C(CH3)2COONa) were fabricated via a facile and mild strategy. We designed a simple and efficient approach (the addition of cyano radicals) to improve the water solubility of nanocomposites. The Ni@GSs-C(CH3)2COONa nanocomposites had great potential as an effective absorbent for removing aromatic compounds from waste water owing to their rapid absorption rate, high absorption capacity, convenient magnetic separation and re-use property.

Thermal conductivity of carbon nanotubes and graphene in epoxy nanofluids and nanocomposites

We employed an easy and direct method to measure the thermal conductivity of epoxy in the liquid (nanofluid) and solid (nanocomposite) states using both rodlike and platelet-like carbon-based nanostructures. Comparing the experimental results with the theoretical model, an anomalous enhancement was obtained with multiwall carbon nanotubes, probably due to their layered structure and lowest surface resistance. Puzzling results for functionalized graphene sheet nanocomposites suggest that phonon coupling of the vibrational modes of the graphene and of the polymeric matrix plays a dominant role on the thermal conductivities of the liquid and solid states.PACS: 74.25.fc; 81.05.Qk; 81.07.Pr.

Effective Heat Transfer Properties of Graphene Sheet Nanocomposites and Comparison to Carbon Nanotube Nanocomposites

By incorporating nanoinclusions (carbon nanotubes, graphene sheets) with exceptional thermal conductivity into a polymer matrix, one would expect to improve the heat performance of resulting nanocomposites. However, the effective thermal conductivity of carbon-based nanocomposites is strongly influenced by the Kapitza interfacial resistance. In this study, a comparison between carbon nanotubes and graphene sheet nanocomposites that takes into account dispersion patterns of the nanoinclusions and the Kapitza resistance is performed by means of a Monte Carlo simulation. It is found that graphene-based nanocomposites can be more efficient thermal conductors than carbon nanotube ones not only because of smaller Kapitza resistance but also because of the geometry of the graphene sheet. When the Kapitza resistance is reduced by appropriate functionalization of the graphene sheets and when the graphene sheet inclusions yield nematic patterns, our calculations suggest the possibility of obtaining composite materi...

Synthesis of Size-Tunable Anatase TiO2 Nanospindles and Their Assembly into Anatase@Titanium Oxynitride/Titanium Nitride−Graphene Nanocomposites for Rechargeable Lithium Ion Batteries with High Cycling Performance

This paper embarks upon three levels of undertaking ranging from nanomaterials synthesis to assembly and functionalization. First, we have prepared size-tunable anatase TiO(2) nanospindles via a hydrothermal process by using tubular titanates as self-sacrificing precursors. Second, we have densely dispersed the TiO(2) nanospindles onto functional graphene oxides (GO) via a spontaneous self-assembly process. After annealing of the TiO(2)/GO hybrid nanocomposite in an NH(3) gas flow, the TiO(2) surface was effectively nitridated and the GO was reduced to graphene sheets (GS) in order to further fortify the electronic functionality of the nanocomposite. Third, the anatase@oxynitride/titanium nitride-GS (TiO(2)@TiO(x)N(y)/TiN-GS) hybrid nanocomposite was studied as an anode material for lithium-ion batteries (LIBs), showing excellent rate capability and cycling performance compared to the pure TiO(2) nanospindles. Our systematic studies have revealed that the TiO(2)@TiO(x)N(y)/TiN-GS nanocomposites with graphene nanosheets covered with the TiO(2)@TiO(x)N(y)/TiN nanospindles on both sides provide a promising solution to the problems of poor electron transport and severe aggregation of TiO(2) nanoparticles by enhancing both electron transport through the conductive matrix and Li-ion accessibility to the active material from the liquid electrolyte. More generally, the size-tunable TiO(2) nanospindles with their unique (101) outer surface planes provide an archetype for the in depth investigation of their surface-specific and size-dependent physicochemical properties.

Properties of Waterborne Polyurethane/Functionalized Graphene Sheet Nanocomposites Prepared by an in situ Method

AbstractNanocomposites of waterborne polyurethane (WPU) with functionalized graphene sheets (FGS) were prepared by an in situ method. The morphology observed by transmission electron microscopy showed that pristine nanosize FGS can be finely dispersed in a WPU matrix so that it can efficiently improve the conductivity of WPU. The modulus improvement by the reinforcing effect of FGS was more evident than our previous results of nanocomposites prepared by a physical mixing method, showing that the interactions between FGS and WPU were improved when made by the in situ method. In addition, the FGS enhanced the crystallization of the soft segment of WPU evidently; however, it reduced that of the hard segment. The thermal degradation of WPU was accelerated by FGS.magnified image

Preparation and Physical Properties of Waterborne Polyurethane/Functionalized Graphene Sheet Nanocomposites

AbstractA nanocomposite of waterborne polyurethane (WPU) was prepared with functionalized graphene sheets (FGSs) which are a new type of nano‐sized conductive filler. The FGS were finely dispersed in a polymer matrix to improve the conductivity of the WPU. Conductivity of about 105 times that of pristine WPU was attained using two parts FGS per 100 parts of the matrix polymer. The FGS reduced the hard segment crystallinity of the WPU, which lowered the modulus of the WPU at room temperature. This modulus reduction became more evident in the temperature region above the glass transition temperature of the hard segment.magnified image

The effect of nanoparticle shape on polymer‐nanocomposite rheology and tensile strength

AbstractNanoparticles can influence the properties of polymer materials by a variety of mechanisms. With fullerene, carbon nanotube, and clay or graphene sheet nanocomposites in mind, we investigate how particle shape influences the melt shear viscosity η and the tensile strength τ, which we determine via molecular dynamics simulations. Our simulations of compact (icosahedral), tube or rod‐like, and sheet‐like model nanoparticles, all at a volume fraction ϕ ≈ 0.05, indicate an order of magnitude increase in the viscosity η relative to the pure melt. This finding evidently can not be explained by continuum hydrodynamics and we provide evidence that the η increase in our model nanocomposites has its origin in chain bridging between the nanoparticles. We find that this increase is the largest for the rod‐like nanoparticles and least for the sheet‐like nanoparticles. Curiously, the enhancements of η and τ exhibit opposite trends with increasing chain length N and with particle shape anisotropy. Evidently, the concept of bridging chains alone cannot account for the increase in τ and we suggest that the deformability or flexibility of the sheet nanoparticles contributes to nanocomposite strength and toughness by reducing the relative value of the Poisson ratio of the composite. The molecular dynamics simulations in the present work focus on the reference case where the modification of the melt structure associated with glass‐formation and entanglement interactions should not be an issue. Since many applications require good particle dispersion, we also focus on the case where the polymer‐particle interactions favor nanoparticle dispersion. Our simulations point to a substantial contribution of nanoparticle shape to both mechanical and processing properties of polymer nanocomposites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1882–1897, 2007