Search results for: functionalized reduced graphene oxide

Authors: V. P. Borker, K. S. Rane, A. J. Bhobe, R. S. Karmali

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Effluent of dye industries contains chemicals and organic dyes. Sometimes they are thrown in the water bodies without any treatment. This leads to environmental pollution and is detrimental to flora and fauna. Semiconducting oxide zinc oxide with wide bandgap 3.37 eV is used as a photocatalyst in degrading organic dyes using UV radiations. It generates electron-hole pair on exposure to UV light. If degradation is aimed at solar radiations, bandgap of zinc oxide is to be reduced so as to utilize visible radiation. Thus, in present study, zinc oxide, ZnO is synthesized from zinc oxalate, N doped zinc oxide, ZnO₁₋ₓNₓ from hydrazinated zinc oxalate, cadmium doped zinc oxide Zn₀.₉Cd₀.₁₀ and magnesium-doped zinc oxide Zn₀.₉Mg₀.₁₀ from mixed metal oxalate and hydrazinated mixed metal oxalate. The precursors were characterized by FTIR. They were decomposed to form oxides and XRD were recorded. The compounds were monophasic. Bandgap was calculated using Diffuse Reflectance Spectrum. The bandgap of ZnO was reduced to 3.24 because of precursor method of synthesis leading large surface area. The bandgap of Zn₀.₉Cd₀.₁₀ was 3.11 eV and that of Zn₀.₉Mg₀.₁₀ 3.41 eV. The lowest value was of ZnO₁₋ₓNₓ 3.09 eV. These oxides were used to degrade methylene blue, a model dye in sunlight. ZnO₁₋ₓNₓ was also used to degrade effluent of industry manufacturing colours, crayons and markers. It was observed that ZnO₁₋ₓNₓ acts as a good photocatalyst for degradation of methylene blue. It can degrade the solution within 120 minutes. Similarly, diluted effluent was decolourised using this oxide. Some colours were degraded using ZnO. Thus, the use of these two oxides could mineralize effluent. Lesser bandgap leads to more electro hole pair thus helps in the formation of hydroxyl ion radicals. These radicals attack the dye molecule, fragmentation takes place and it is mineralised.

Keywords: cadmium doped zinc oxide, dye degradation, dye effluent degradation, N doped zinc oxide, zinc oxide

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Authors: Juliana V. Pereira, Adriana S. M. Batista, Jefferson P. Nascimento, Clascídia A. Furtado, Luiz O. Faria

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The combination of the properties of graphene oxide (OG) and PVDF homopolymer makes their combined composite materials as multifunctional systems with great potential. Knowledge of the molecular structure is essential for better use. In this work, the degradation of PVDF polymer exposed to gamma irradiation in oxygen atmosphere in high dose rate has been studied and compared to degradation of PVDF/OG composites. The samples were irradiated with a Co-60 source at constant dose rate, with doses ranging from 100 kGy to 1,000 kGy. In FTIR data shown that the formation of oxidation products was at the both samples with formation of carbonyl and hydroxyl groups amongst the most prevalent products in the pure PVDF samples. In the other hand, the composites samples exhibit less presence of degradation products with predominant formation of carbonyl groups, these results also seen in the UV-Vis analysis. The results show that the samples of composites may have greater resistance to the irradiation process, since they have less degradation products than pure PVDF samples seen by spectroscopic techniques.

Keywords: gamma irradiation, PVDF, PVDF/OG composites, spectroscopic techniques

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Authors: Defne Akay, Bekir S. Kandemir

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In this paper, we investigate the low-lying energy levels of the two-dimensional parabolic graphene quantum dots (GQDs) in the presence of topological defects with long range Coulomb impurity and subjected to an external uniform magnetic field. The low-lying energy levels of the system are obtained within the framework of the perturbation theory. We theoretically demonstrate that a valley splitting can be controlled by geometrical parameters of the graphene quantum dots and/or by tuning a uniform magnetic field, as well as topological defects. It is found that, for parabolic graphene dots, the valley splitting occurs due to the introduction of spatial confinement. The corresponding splitting is enhanced by the introduction of a uniform magnetic field and it increases by increasing the angle of the cone in subcritical regime.

Keywords: coulomb impurity, graphene cones, graphene quantum dots, topological defects

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Authors: Özge Alptoğa, Nuray Uçar, Nilgün Karatepe Yavuz, Ayşen Önen

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Sulfur dioxide (SO₂) is a very toxic air pollutant gas and it causes the greenhouse effect, photochemical smog, and acid rain, which threaten human health severely. Thus, the capture of SO₂ gas is very important for the environment. Graphene which is two-dimensional material has excellent mechanical, chemical, thermal properties, and many application areas such as energy storage devices, gas adsorption, sensing devices, and optical electronics. Further, graphene oxide (GO) is examined as a good adsorbent because of its important features such as functional groups (epoxy, carboxyl and hydroxyl) on the surface and layered structure. The SO₂ adsorption properties of the fibers are usually investigated on carbon fibers. In this study, potential adsorption capacity of GO fibers was researched. GO dispersion was first obtained with Hummers’ method from graphite, and then GO fibers were obtained via wet spinning process. These fibers were converted into a disc shape, dried, and then subjected to SO₂ gas adsorption test. The SO₂ gas adsorption capacity of GO fiber discs was investigated in the fields of utilization of different coagulation baths and reduction by hydrazine hydrate. As coagulation baths, single and triple baths were used. In single bath, only ethanol and CaCl₂ (calcium chloride) salt were added. In triple bath, each bath has a different concentration of water/ethanol and CaCl₂ salt, and the disc obtained from triple bath has been called as reference disk. The fibers which were produced with single bath were flexible and rough, and the analyses show that they had higher SO₂ adsorption capacity than triple bath fibers (reference disk). However, the reduction process did not increase the adsorption capacity, because the SEM images showed that the layers and uniform structure in the fiber form were damaged, and reduction decreased the functional groups which SO₂ will be attached. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) analyzes were performed on the fibers and discs, and the effects on the results were interpreted. In the future applications of the study, it is aimed that subjects such as pH and additives will be examined.

Keywords: coagulation bath, graphene oxide fiber, reduction, SO2 gas adsorption

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Authors: Marianna I. Triantou, Konstantina I. Stathi, Petroula A. Tarantili

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In the present study, the incorporation of graphene into blends of acrylonitrile-butadiene-styrene terpolymer with polypropylene (ABS/PP) was investigated focusing on the improvement of their thermomechanical characteristics and the effect on their rheological behavior. The blends were prepared by melt mixing in a twin-screw extruder and were characterized by measuring the MFI as well as by performing DSC, TGA and mechanical tests. The addition of graphene to ABS/PP blends tends to increase their melt viscosity, due to the confinement of polymer chains motion. Also, graphene causes an increment of the crystallization temperature (Tc), especially in blends with higher PP content, because of the reduction of surface energy of PP nucleation, which is a consequence of the attachment of PP chains to the surface of graphene through the intermolecular CH-π interaction. Moreover, the above nanofiller improves the thermal stability of PP and increases the residue of thermal degradation at all the investigated compositions of blends, due to the thermal isolation effect and the mass transport barrier effect. Regarding the mechanical properties, the addition of graphene improves the elastic modulus, because of its intrinsic mechanical characteristics and its rigidity, and this effect is particularly strong in the case of pure PP.

Keywords: acrylonitrile-butadiene-styrene terpolymer, blends, graphene, polypropylene

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Authors: Wen-Jay Lee, Kuo-Ning Chiang

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The graphene binding with silicon substrate has apparently Schottky barriers property, which can be used in the application of solar cell and light source. Because graphene has only one atom layer, the atomistic structure of graphene binding with the silicon surface plays an important role to affect the properties of graphene. In this work, temperature effect on the morphology of graphene sheet attached on different crystal planes of silicon substrates are investigated by Molecular dynamics (MD) (LAMMPS, developed by Sandia National Laboratories). The results show that the covered graphene sheet would cause the structural deformation of the surface Si atoms of stubtrate. To achieve a stable state in the binding process, the surface Si atoms would adjust their position and fit the honeycomb structure of graphene after the graphene attaches to the Si surface. The height contour of graphene on different plane of silicon surfaces presents different pattern, leading the local residual stress at the interface. Due to the high density of dangling bond on the Si (111)7x7 surface, the surface of Si(111)7x7 is not matching with the graphene so well in contrast with Si(100)2x1and Si(111)2x1. Si(111)7x7 is found that only partial silicon adatoms are rearranged on surface after the attachment when the temperature is lower than 200K, As the temperature gradually increases, the deformation of surface structure becomes significant, as well as the residue stress. With increasing temperature till the 815K, the graphene sheet begins to destroy and mixes with the silicon atoms. For the Si(100)2x1 and Si(111)2x1, the silicon surface structure keep its structural arrangement with a higher temperature. With increasing temperature, the residual stress gradually decrease till a critical temperatures. When the temperature is higher than the critical temperature, the residual stress gradually increases and the structural deformation is found on the surface of the Si substrates.

Keywords: molecular dynamics, graphene, silicon, Schottky barriers, interface

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Authors: Jay J. Vora, Vishvesh J. Badheka

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This work attempts to investigate the effect of oxide fluxes on 6mm thick Reduced Activation ferritic/martensitic steels (RAFM) during Activated TIG (A-TIG) welding. Six different fluxes Al₂O₃, Co₃O₄, CuO, HgO, MoO₃, and NiO were mixed with methanol for conversion into paste and bead-on-plate experiments were then carried out. This study, systematically investigates the influence of oxide-based flux powder and carrier solvent composition on the weld bead shape, geometric shape of weld bead and dominant depth enhancing mechanism in tungsten inert gas (TIG) welding of reduced activation ferritic/martensitic (RAFM) steel. It was inferred from the study that flux Co₃O₄ and MoO₃ imparted full and secure (more than 6mm) penetration with methanol owing to dual mechanism of reversed Marangoni and arc construction. The use of methanol imparted good spreadabilty and coverability and ultimately higher peak temperatures were observed with its use owing to stronger depth enhancing mechanisms than use of acetone with same oxide fluxes and welding conditions.

Keywords: A-TIG, flux, oxides, penetration, RAFM, temperature, welding

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Authors: M. K. Bin Subhan, P. Cullen, C. Howard

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A recent study by the World Corrosion Organization estimated that corrosion related damage causes $2.5tr worth of damage every year. As such, a low cost easily scalable solution is required to the corrosion problem which is economically viable. Graphene is an ideal anti-corrosion barrier layer material due to its excellent barrier properties and chemical stability, which makes it impermeable to all molecules. However, attempts to employ graphene as a barrier layer has been hampered by the fact that defect sites in graphene accelerate corrosion due to the inert nature of graphene which promotes galvanic corrosion at the expense of the metal. The recent discovery of spontaneous dissolution of charged graphite intercalation compounds in aprotic solvents enables defect free graphene platelets to be employed for anti-corrosion applications. These ‘inks’ of defect-free charged graphene platelets in solution can be coated onto a metallic surfaces via electroplating to form a homogeneous barrier layer. In this paper, initial data showing homogeneous coatings of graphene barrier layers on steel coupons via electroplating will be presented. This easily scalable technique also provides a controllable method for applying different barrier thicknesses from ultra thin layers to thick opaque coatings making it useful for a wide range of applications.

Keywords: anti-corrosion, defect-free, electroplating, graphene

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Authors: Nikhil Jain, Yang Xu, Bin Yu

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Hexagonal boron nitride (h-BN) has been used as a substrate and gate dielectric for graphene field effect transistors (GFETs). Using a graphene/h-BN/TiN (channel/dielectric/gate) stack, key material properties of h-BN were investigated i.e. dielectric strength and tunneling behavior. Work function difference between graphene and TiN results in spontaneous p-doping of graphene through a multi-layer h-BN flake. However, at high levels of current stress, n-doping of graphene is observed, possibly due to the charge transfer across the thin h-BN multi layer. Neither Direct Tunneling (DT) nor Fowler-Nordheim Tunneling (FNT) was observed in TiN/h-BN/Au hetero structures with h-BN showing two distinct volatile conduction states before breakdown. Hexagonal boron nitride emerges as a material of choice for gate dielectrics in GFETs because of robust dielectric properties and high tunneling barrier.

Keywords: graphene, transistors, conduction, hexagonal boron nitride, dielectric strength, tunneling

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Authors: Prasanta Sutradhar, Mitali Saha

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With an increasing awareness of green and clean energy, zinc oxide based solar cells were found to be suitable candidates for cost-effective and environmentally friendly energy conversion devices. In this work, we have reported the green synthesis of zinc oxide nanoparticles (ZnO) by thermal method and under microwave irradiation using the aqueous extract of tomatoes as non-toxic and ecofriendly reducing material. The synthesized ZnO nanoparticles were characterised by UV-Visible spectroscopy (UV-Vis), infra-red spectroscopy (IR), particle size analyser (DLS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X- ray diffraction study (XRD). A series of ZnO nanocomposites with titanium dioxide nanoparticles (TiO2) and graphene oxide (GO) were prepared for photovoltaic application. Structural and morphological studies of these nanocomposites were carried out using UV-vis, SEM, XRD, and AFM. The current-voltage measurements of the nanocomposites demonstrated enhanced power conversion efficiency of 6.18% in case of ZnO/GO/TiO2 nanocomposite.

Keywords: ZnO, green synthesis, microwave, nanocomposites, I-V characteristics

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Authors: Kolja Them, Johannes Salamon, Harald Ittrich, Michael Kaul, Tobias Knopp

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Superparamagnetic iron oxide nanoparticles (SPIONs) are nanoscale magnets which can be biologically functionalized for biomedical applications. Stem cell therapies to repair damaged tissue, magnetic fluid hyperthermia for cancer therapy and targeted drug delivery based on SPIONs are prominent examples where the visualization of a preferably low concentrated SPION distribution is essential. In 2005 a new method for tomographic SPION imaging has been introduced. The method named magnetic particle imaging (MPI) takes advantage of the nanoparticles magnetization change caused by an oscillating, external magnetic field and allows to directly image the time-dependent nanoparticle distribution. The SPION magnetization can be changed by the electron spin dynamics as well as by a mechanical rotation of the nanoparticle. In this work different calibration methods in MPI are investigated for image reconstruction of magnetically labeled stem cells. It is shown that a calibration using rotationally immobilized SPIONs provides a higher quality of stem cell images with fewer artifacts than a calibration using mobile SPIONs. The enhancement of the image quality and the reduction of artifacts enables the localization and identification of a smaller number of magnetically labeled stem cells. This is important for future medical applications where low concentrations of functionalized SPIONs interacting with biological matter have to be localized.

Keywords: biomedical imaging, iron oxide nanoparticles, magnetic particle imaging, stem cell imaging

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Authors: Wang-Xi Fan, Yi Ding, Zhong-Dan Tu, Kuo-Shien Huang, Chao-Ming Huang, Jen-Taut Yeh

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Original and/or functionalized activated nanocarbon particles with a quoted specific surface area of 100, 500, 1000 and 1400 m2/g, respectively, were used to investigate the influence of specific surface areas of activated nanocarbon on ultra drawing and ultimate tensile properties of ultrahigh molecular weight polyethylene (UHMWPE), UHMWPE/activated nanocarbon and UHMWPE/ functionalized activated nanocarbon fibers. The specific surface areas of well dispersed functionalized activated nanocarbon in UHMWPE/functionalized activated nanocarbon fibers can positively affect their ultra drawing, orientation, ultimate tensile properties and “micro-fibril” characteristics. Excellent orientation and ultimate tensile properties of UHMWPE/nanofiller fibers can be prepared by ultra drawing the UHMWPE/functionalized activated nanocarbon as-prepared fibers with optimal contents and compositions of functionalized activated nanocarbon. The ultimate tensile strength value of the best prepared UHMWPE/functionalized activated nanocarbon drawn fiber reached 8.0 GPa, which was about 2.86 times of that of the best-prepared UHMWPE drawn fiber prepared in this study. Specific surface area, morphological and Fourier transform infrared analyses of original and functionalized activated nanocarbon and/or investigations of thermal, orientation factor and ultimate tensile properties of as-prepared and/or drawn UHMWPE/functionalized activated nanocarbon fibers were performed to understand the above-improved ultra drawing and ultimate tensile properties of the UHMWPE/functionalized activated nanocarbon fibers.

Keywords: activated nanocarbon, specific surface areas, ultradrawing, ultrahigh molecular weight polyethylene

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Authors: Ashiq Rahman, Sunil Thapa, Shunyao Fan, Niloy K. Dutta

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A 20-GHz and a 50-GHz pulse train are generated using a fiber ring laser setup that incorporates Rational Harmonic Mode Locking. Two separate experiments were carried out using charcoal nanoparticles and graphene nanoparticles acting as saturable absorbers to reduce the pulse width generated from rational harmonic mode-locking (RHML). Autocorrelator trace shows that the pulse width is reduced from 5.6-ps to 3.2-ps using charcoal at 20-GHz, and to 2.7-ps using graphene at 50-GHz repetition rates, which agrees with the simulation findings. Numerical simulations have been carried out to study the effect of varying the linear and nonlinear absorbance parameters of both absorbers on output pulse widths. Experiments closely agree with the simulations.

Keywords: fiber optics, fiber lasers, mode locking, saturable absorbers

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Authors: Bijaya Kumar Sahoo

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The effect of III-V nitride semiconductors on performance of a graphene-on-gold surface plasmon resonance (SPR) biosensor has been investigated theoretically. III-V nitrides (AlN, GaN and InN) have been grown between gold (Au) and graphene layers. The sensitivity and performance of the biosensor have been computed for with and without semiconductors. Due to superior electronic and optical properties, III-V nitrides demonstrate high sensitivity and performance over Si and Ge. The enhancement of evanescent electric field due to III-V nitrides have been computed and found highest for InN. The analysis shows that for a high-sensitive imaging biosensor the required optimal thickness of gold, InN and graphene are respectively 49 nm, 11 nm and 0.34 nm for the light of wavelength =633 nm (red He-Ne laser). This study suggests that InN would be a better choice for fabrication of new imaging SPR biosensors.

Keywords: SPR biosensor, optical properties, III-V nitrides, sensitivity, enhancement of electric field, performance of graphene gold SPR biosensor

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Authors: K. Saravanan, K. A.Rameshkumar, P. Maadeswaran

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The depletion of fossil resources and the rise in global temperatures are two of the most important concerns we confront today. There are numerous renewable energy sources like solar power, tidal power, wind energy, radiant energy, hydroelectricity, geothermal energy, and biomass available to generate the needed energy demand. Engineers and scientists around the world are facing a massive barrier in the development of storage technologies for the energy developed from renewable energy sources. The development of electrochemical capacitors as a future energy storage technology is at the forefront of current research and development. This is due to the fact that the electrochemical capacitors have a significantly higher energy density, a faster charging-discharging rate, and a longer life span than capacitors, and they also have a higher power density than batteries, making them superior to both. In this research, electrochemical capacitors using the Nd2O3/Mn3O4/ N-rGO electrode material is chosen since the of hexagonal and tetragonal crystal structures of Nd2O3 and Mn3O4 and also has cycling stability of 68% over a long time at 50mVs-1 and a high coulombic efficiency of 99.64% at 5 Ag-1. This approach may also be used to create novel electrode materials with improved electrochemical and cyclic stability for high-performance supercapacitors.

Keywords: Nd2O3/Mn3O4/N-rGO, nanocomposites, hydrothermal method, electrode material, specific capacitance, use of supercapacitors

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Authors: Nurhafizah Md. Disa, Nurhayati Binti Abdullah, Muhammad Rabie Bin Omar

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This research intends to identify the existing knowledge gap because of the lack of substantial studies to fabricate and characterize bio-graphene created from Oil Palm Shell (OPS) through the means of pre-treatment and slow pyrolysis. By fabricating bio-graphene through OPS, a novel material can be found to procure and used for graphene-based research. The characterization of produced bio-graphene is intended to possess a unique hexagonal graphene pattern and graphene properties in comparison to other previously fabricated graphene. The OPS will be fabricated by pre-treatment of zinc chloride (ZnCl₂) and iron (III) chloride (FeCl3), which then induced the bio-graphene thermally by slow pyrolysis. The pyrolizer's final temperature and resident time will be set at 550 °C, 5/min, and 1 hour respectively. Finally, the charred product will be washed with hydrochloric acid (HCL) to remove metal residue. The obtained bio-graphene will undergo different analyses to investigate the physicochemical properties of the two-dimensional layer of carbon atoms with sp2 hybridization hexagonal lattice structure. The analysis that will be taking place is Raman Spectroscopy (RAMAN), UV-visible spectroscopy (UV-VIS), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). In retrospect, RAMAN is used to analyze three key peaks found in graphene, namely D, G, and 2D peaks, which will evaluate the quality of the bio-graphene structure and the number of layers generated. To compare and strengthen graphene layer resolves, UV-VIS may be used to establish similar results of graphene layer from last layer analysis and also characterize the types of graphene procured. A clear physical image of graphene can be obtained by analyzation of TEM in order to study structural quality and layers condition and SEM in order to study the surface quality and repeating porosity pattern. Lastly, establishing the crystallinity of the produced bio-graphene, simultaneously as an oxygen contamination factor and thus pristineness of the graphene can be done by XRD. In the conclusion of this paper, this study is able to obtain bio-graphene through OPS as a novel material in pre-treatment by chloride ZnCl₂ and FeCl3 and slow pyrolization to provide a characterization analysis related to bio-graphene that will be beneficial for future graphene-related applications. The characterization should yield similar findings to previous papers as to confirm graphene quality.

Keywords: oil palm shell, bio-graphene, pre-treatment, slow pyrolysis

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Authors: Gansukh Erdenedelger, Doljinsuren Sukhbaatar, Trung Dung Dao, Byeong-Kyu Lee, Han Mo Jeong

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Two kinds of carboxylated thermally reduced graphenes (C-TRGs) having different lateral sizes are examined as a Pickering stabilizer in the suspension polymerization of methyl methacrylate. The size and the shape of the prepared composite particles are irregular due to agglomeration, more evidently when the larger C-TRG is used. In addition, C-TRG is distributed not only on the surface but also inside the composite particles. It indicates that the C-TRG alone is not a stable Pickering agent. However, a very small dosage of acrylic acid remedies all these issues, because acrylic acid interacts with C-TRG and synergizes the stabilizing effect. The compression molded composite of the core/shell poly(methyl methacrylate)/C-TRG particles exhibits a very low percolation threshold of electrical conductivity of 0.03 vol%. It demonstrates that the C-TRG shells of the composite particles effectively form a segregated conductive network throughout the composite.

Keywords: pickering, graphene, polymerization, PMMA

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Authors: Mohammad Shafiul Alam, Mineo Saito

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Graphene-based materials have attracted much attention because they are candidates for post silicon materials. Since controlling of impurities is necessary to achieve nano device, we study hydrogen impurity in multi-layer graphene. We perform local spin Density approximation (LSDA) in which the plane wave basis set and pseudopotential are used. Previously hydrogen monomer and dimer in graphene is well theoretically studied. However, hydrogen on multilayer graphene is still not clear. By using first-principles electronic structure calculations based on the LSDA within the density functional theory method, we studied hydrogen monomers and dimers in two-layer graphene. We found that the monomers are spin-polarized and have magnetic moment 1 µB. We also found that most stable dimer is much more stable than monomer. In the most stable structures of the dimers in two-layer graphene, the two hydrogen atoms are bonded to the host carbon atoms which are nearest-neighbors. In this case two hydrogen atoms are located on the opposite sides. Whereas, when the two hydrogen atoms are bonded to the same sublattice of the host materials, magnetic moments of 2 µB appear in two-layer graphene. We found that when the two hydrogen atoms are bonded to third-nearest-neighbor carbon atoms, the electronic structure is nonmagnetic. We also studied hydrogen monomers and dimers in three-layer graphene. The result is same as that of two-layer graphene. These results are very important in the field of carbon nanomaterials as it is experimentally difficult to show the magnetic state of those materials.

Keywords: first-principles calculations, LSDA, multi-layer gra-phene, nanomaterials

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Authors: Alok Srivastava, Vidit Gupta, Aparna Singh, Chandra Sekher Yerramalli

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Carbon-fiber epoxy composites show extremely high modulus and strength in the uniaxial direction. However, they are prone to fail under low load in transverse direction due to the weak nature of the interface between the carbon-fiber and epoxy. In the current study, we have coated graphene nano-platelets (GNPs) on the carbon-fibers in an attempt to strengthen the interface/interphase between the fiber and the matrix. Vacuum Assisted Resin Transfer Moulding (VARTM) has been used to make the laminates of eight cross-woven fabrics. Tensile, flexural and fracture toughness tests have been performed on pristine carbon-fiber composite (P-CF), GNP coated carbon-fiber composite (GNP-CF) and functionalized-GNP coated carbon-fiber composite (F-GNP-CF). The tensile strength and flexural strength values are pretty similar for P-CF and GNP-CF. The micro-structural examination of the GNP coated carbon-fibers, as well as the fracture surfaces, have been carried out using scanning electron microscopy (SEM). The micrographs reveal the deposition of GNPs onto the carbon fibers in transverse and longitudinal direction. Fracture surfaces show the debonding and pull outs of the carbon fibers in P-CF and GNP-CF samples.

Keywords: carbon fiber, graphene nanoplatelets, strength, VARTM, Vacuum Assisted Resin Transfer Moulding

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Authors: Kai Huang, Assamen Ayalew Ejigu, Mu-Jie Lin, Liang-Chiun Chao

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Nickel oxide and copper-nickel oxide thin films have been successfully deposited by reactive ion beam sputter deposition. Experimental results show that nickel oxide deposited at 300°C is single phase NiO while best crystalline quality is achieved with an O_pf of 0.5. XRD analysis of nickel-copper oxide deposited at 300°C shows a Ni2O3 like crystalline structure at low O_pf while changes to NiO like crystalline structure at high O_pf. EDS analysis shows that nickel-copper oxide deposited at low O_pf is CuxNi2-xO3 with x = 1, while nickel-copper oxide deposited at high O_pf is CuxNi1-xO with x = 0.5, which is supported by Raman analysis. The bandgap of NiO is ~ 3.5 eV regardless of O_pf while the band gap of nickel-copper oxide decreases from 3.2 to 2.3 eV as Opf reaches 1.0.

Keywords: copper, ion beam, NiO, oxide, resistivity, transparent

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Authors: Shaya Mahmoudian, Mohammad Reza Sazegar, Nazanin Afshari

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Graphene, a single layer of carbon atoms in a hexagonal lattice, has recently attracted great attention due to its unique mechanical, thermal and electrical properties. The high aspect ratio and unique surface features of graphene resulted in significant improvements of the nano composites properties. In this study, nano composite fibres made of cellulose and graphene nano platelets were wet spun from solution by using ionic liquid, 1-ethyl-3-methylimidazolium acetate (EMIMAc) as solvent. The effect of graphene loading on the thermal and electrical properties of the nanocomposite fibres was investigated. The nano composite fibres characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. XRD analysis revealed a cellulose II crystalline structure for regenerated cellulose and the nano composite fibres. SEM images showed a homogenous morphology and round cross section for the nano composite fibres along with well dispersion of graphene nano platelets in regenerated cellulose matrix. The incorporation of graphene into cellulose matrix generated electrical conductivity. At 6 wt. % of graphene, the electrical conductivity was 4.7 × 10-4 S/cm. The nano composite fibres also showed considerable improvements in thermal stability and char yield compared to pure regenerated cellulose fibres. This work provides a facile and environmentally friendly method of preparing nano composite fibres based on cellulose and graphene nano platelets that can find several applications in cellulose-based carbon fibres, conductive fibres, apparel, etc.

Keywords: nanocomposite, graphene nanoplatelets, regenerated cellulose, electrical properties

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Authors: M. Haghnegahdar, G. Naderi, M. H. R. Ghoreishy

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Polypropylene(PP)/Ethylene Propylene Diene Monomer (EPDM) samples (80/20) containing 0, 0.5, 1, 1.5, 2, 2.5, and 3 (expressed in mass fraction) graphene were prepared using melt compounding method to investigate microstructure, mechanical properties, and thermal stability as well as electrical resistance of samples. X-Ray diffraction data confirmed that graphene platelets are well dispersed in PP/EPDM. Mechanical properties such as tensile strength, impact strength and hardness demonstrated increasing trend by graphene loading which exemplifies substantial reinforcing nature of this kind of nano filler and it's good interaction with polymer chains. At the same time it is found that thermo-oxidative degradation of PP/EPDM nanocomposites is noticeably retarded with the increasing of graphene content. Electrical surface resistivity of the nanocomposite was dramatically changed by forming electrical percolation threshold and leads to change electrical behavior from insulator to semiconductor. Furthermore, these results were confirmed by scanning electron microscopy(SEM), dynamic mechanical thermal analysis (DMTA), and transmission electron microscopy (TEM).

Keywords: nanocomposite, graphene, microstructure, mechanical properties

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Authors: Maryam Kiani, Abdul Basit Kiani

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Simple hydrothermal method to synthesize new nanocomposites consisting of nitrogen-doped graphene and NiFe₂O₄. By analyzing the X-Ray Powder Diffraction (XRD) images, we confirmed that the NiFe₂O₄ phase is pure and has a Face Centered Cubic (FCC) structure. The average size of the NiFe₂O₄ nanoparticles is approximately 40±2 nm. Additionally, we used X-ray photoelectron spectroscopy (XPS) to study the surface chemical composition and cation oxidation states of both the NiFe₂O₄ nanoparticles and the nitrogen-doped graphene/NiFe₂O₄ nanocomposites. A magnetic interaction between nitrogen doped graphene/NiFe₂O₄ was studied. Increases in hydrothermal synthesis temperature lead to the improved crystalline structure of NiFe₂O₄ nanoparticles, which improves the magnetic properties.

Keywords: nickel ferrite spinal, nitrogen doped graphene, magnetic nanocomposite, hydrothermal synthesis

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Authors: Jhen-Ting Huang, Chia-Chia Chang, Hu-Cheng Weng, An-Ya Lo

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In this study, Co3O4-CNT-Graphene composite electrode was deposited by electrophoretic deposition (EPD) method, where micro polystyrene spheres (PSs) were added for co-deposition. Applied with heat treatment, a hierarchical porosity is left in the electrode which is beneficial for supercapacitor application. In terms of charge and discharge performance, we discussed the optimal CNT/Graphene ratio, macroporous ratio, and the effect of Co3O4 addition on electrode capacitance. For materials characterization, scanning electron microscope (SEM), X-ray diffraction, and BET were applied, while cyclic voltammetry (CV) and chronopotentiometry (CP) measurements, and Ragone plot were applied as in-situ analyses. Based on this, the effects of PS amount on the structure, porosity and their effect on capacitance of the electrodes were investigated. Finally, the full device performance was examined with charge-discharge and electron impedance spectrum (EIS) methods. The results show that the EPD coating with hierarchical porosity was successfully demonstrated in this study. As a result, the capacitance was greatly enhanced by 2.6 times with the hierarchical structure.

Keywords: supercapacitor, nanocarbon tub, graphene, metal oxide

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Authors: Olukunle C. Olawole, Dilip K. De, Moses Emetere, Omoje Maxwell

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Graphene can stand very high temperature up to 4500 K in vacuum and has potential for application in thermionic energy converter. In this paper, we discuss the application of energy dynamics principles and the modified Richardson-Dushman Equation, to estimate the efficiency of solar power conversion to electrical power by a solar thermionic energy converter (STEC) containing emitter made of graphene. We present detailed simulation of power output for different solar insolation, diameter of parabolic concentrator, area of the graphene emitter (same as that of the collector), temperature of the collector, physical dimensions of the emitter-collector etc. After discussing possible methods of reduction or elimination of space charge problem using magnetic field and gate, we finally discuss relative advantages of using emitters made of graphene, carbon nanotube and metals respectively in a STEC.

Keywords: graphene, high temperature, modified Richardson-Dushman equation, solar thermionic energy converter

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Authors: Chejarla Raghunathababu, E. Logashanmugam

Abstract:

An antenna is an assortment of linked devices that function together to transmit and receive radio waves as a single antenna. Antennas occur in a variety of sizes and forms, but the microstrip patch antenna outperforms other types in terms of effectiveness and prediction. These antennas are easy to generate with discreet benefits. Nevertheless, the antenna's effectiveness will be affected because of the patch's shape above a thick dielectric substrate. As a result, a double-pole rectangular microstrip antenna with nanofillers was suggested in this study. By employing nano-composite substances (Fumed Silica and Aluminum Oxide), which are composites of graphene with nanofillers, the physical characteristics of the microstrip antenna, that is, the elevation of the microstrip antenna substrate and the width of the patch microstrip antenna have been improved in this research. The surface conductivity of graphene may be modified to function at specific frequencies. In order to prepare for future wireless communication technologies, a microstrip patch antenna operating at 93 GHz resonant frequency is constructed and investigated. The goal of this study was to reduce VSWR and increase gain. The simulation yielded results for the gain and VSWR, which were 8.26 dBi and 1.01, respectively.

Keywords: graphene, microstrip patch antenna, substrate material, wireless communication, nanocomposite material

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Authors: Arifa Batool, Ghulam Hussain Bhatti, Syed Mujtaba Shah

Abstract:

Inorganic n-type (TiO2, CdO) and p-type (NiO, CuO) metal oxide nanoparticles were synthesized by a facile wet chemical method at room temperature. The morphological, compositional, structural and optical properties were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, FT-IR, XRD analysis, UV/Visible and fluorescence spectroscopy. All semiconducting nanoparticles were photosensitized with Ru (II) based Z907 dye in ethanol solvent by grafting. Grafting of dye on the surface of nanoparticles was confirmed by UV/Visible and FT-IR spectroscopy. The synthesized photo-active nanohybrid was thoroughly blended with P3HT, a solid electrolyte and I-V measurements under solar stimulated radiations 1000 W/m2 (AM 1.5) were recorded. Maximum incident photon to current conversion efficiency (IPCE) of 0.9% was achieved with dye functionalized Z907-TiO2 hybrid, IPCE of 0.72% was achieved with bulk-heterojunction of TiO2-Z907-CuO and IPCE of 0.68% was attained with nanocomposite of TiO2-CdO. TiO2 based Solar cells have maximum Jscvalue i.e.4.63 mA/cm2. Dye-functionalized TiO2-based photovoltaic devices were found more efficient than the reference device but the morphology of the device was a major check in progress.

Keywords: solar cell, bulk heterojunction, nanocomposites, photosensitization, dye sensitized solar cell

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Authors: G. M. Vlasceanu, H. Iovu, E. Vasile, M. Ionita

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Herein, the synthesis and characterization of chitosan-gelatin highly porous scaffold reinforced with graphene oxide, and hydroxyapatite (HAp), crosslinked with genipin was targeted. In tissue engineering, chitosan and gelatin are two of the most robust biopolymers with wide applicability due to intrinsic biocompatibility, biodegradability, low antigenicity properties, affordability, and ease of processing. HAp, per its exceptional activity in tuning cell-matrix interactions, is acknowledged for its capability of sustaining cellular proliferation by promoting bone-like native micro-media for cell adjustment. Genipin is regarded as a top class cross-linker, while graphene oxide (GO) is viewed as one of the most performant and versatile fillers. The composites with natural bone HAp/biopolymer ratio were obtained by cascading sonochemical treatments, followed by uncomplicated casting methods and by freeze-drying. Their structure was characterized by Fourier Transform Infrared Spectroscopy and X-ray Diffraction, while overall morphology was investigated by Scanning Electron Microscopy (SEM) and micro-Computer Tomography (µ-CT). Ensuing that, in vitro enzyme degradation was performed to detect the most promising compositions for the development of in vivo assays. Suitable GO dispersion was ascertained within the biopolymer mix as nanolayers specific signals lack in both FTIR and XRD spectra, and the specific spectral features of the polymers persisted with GO load enhancement. Overall, correlations between the GO induced material structuration, crystallinity variations, and chemical interaction of the compounds can be correlated with the physical features and bioactivity of each composite formulation. Moreover, the HAp distribution within follows an auspicious density gradient tuned for hybrid osseous/cartilage matter architectures, which were mirrored in the mice model tests. Hence, the synthesis route of a natural polymer blend/hydroxyapatite-graphene oxide composite material is anticipated to emerge as influential formulation in bone tissue engineering. Acknowledgement: This work was supported by the project 'Work-based learning systems using entrepreneurship grants for doctoral and post-doctoral students' (Sisteme de invatare bazate pe munca prin burse antreprenor pentru doctoranzi si postdoctoranzi) - SIMBA, SMIS code 124705 and by a grant of the National Authority for Scientific Research and Innovation, Operational Program Competitiveness Axis 1 - Section E, Program co-financed from European Regional Development Fund 'Investments for your future' under the project number 154/25.11.2016, P_37_221/2015. The nano-CT experiments were possible due to European Regional Development Fund through Competitiveness Operational Program 2014-2020, Priority axis 1, ID P_36_611, MySMIS code 107066, INOVABIOMED.

Keywords: biopolymer blend, ectopic osteoinduction, graphene oxide composite, hydroxyapatite

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Authors: Yameen Ahmed, Jamshid Hussain, Farman Ullah, Sohaib Asif

Abstract:

The investigation aims at the synthesis of copper oxide and cobalt oxide nanoparticles using Spinacia oleracea leaf extract. These nanoparticles have many properties and applications. They possess antimicrobial catalytic properties and also they can be used in energy storage materials, gas sensors, etc. The Spinacia oleracea leaf extract behaves as a reducing agent in nanoparticle synthesis. The plant extract was first prepared and then treated with copper and cobalt salt solutions to get the precipitate. The salt solutions used for this purpose are copper sulfate pentahydrate (CuSO₄.5H₂O) and cobalt chloride hexahydrate (CoCl₂.6H₂O). The UV-Vis, XRD, EDX, and SEM techniques are used to find the optical, structural, and morphological properties of copper oxide and cobalt oxide nanoparticles. The UV absorption peaks are at 326 nm and 506 nm for copper oxide and cobalt oxide nanoparticles.

Keywords: cobalt oxide, copper oxide, green synthesis, nanoparticles

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Authors: Pamphile Ndagijimana, Xuejiao Liu, Zhiwei Li, Yin Wang

Abstract:

Enhancing the properties of activated carbon is very imperative for various applications. Indeed, the activated carbon has promising physicochemical properties desired for a considerable number of applications. In this regard, we are proposing an enhanced and green technology for increasing the efficiency and performance of the activated carbon to various applications. The technique poses on the use of natural extracts from tuberous and cereals based-solutions. These solutions showed high potentiality to be used in the synthesis of activated carbon-graphene composite with only 3 mL. The extracted liquid from tuberous sourcing was enough to induce precipitation within a fraction of a minute in contrast to that from cereal sourced. Using these extracts, a synthesis of activated carbon-graphene composite was successful. Different characterization techniques such as XRD, SEM, FTIR, BET, and Raman spectroscopy were performed to investigate the composite materials. The results confirmed a conjugation between activated carbon and graphene material.

Keywords: activated carbon, cereals, extract solution, graphene, tuberous

Procedia PDF Downloads 147