Graphene Oxide-carbon Nanotubes Hybrid Research Articles

Synergic influence of fly ash and graphene oxide-carbon nanotubes hybrid on mechanical, microstructural and porosity properties of cement mortars

The current study investigates the better reinforcing tendency of superplasticizer stabilized carbon nanomaterials hybrid, i.e. FCNT@GO in comparison to the individual carbon nanomaterials, i.e. either graphene oxide (GO) or functionalized carbon nanotubes (FCNTs) on the fly ash blended cement mortars (FCMs). The compressive strength for 0.08% FCNT-FCMs and 0.08% GO-FCMs (by weight percent of cement-FA blend) was improved by 24.9% and 39.8%, in comparison to Control (FA) sample, respectively, at 90 days of curing. However, for FCNT@GO hybrid incorporated mortars, a superior improvement of 52.1% was found at the dosage of 0.16%. On the contrary, the maximum split tensile strength improvement was 64.3% for 0.08% FCNT@GO-FCMs whereas, 0.08% GO-FCMs and 0.16% FCNT-FCMs showed an enhancement of 48.9% and 39.7%, respectively. These results were also compared to the Control (cement) samples. The compressive and tensile strength values for 0.16% FCNT@GO-FCMs (39.7 MPa and 5.2 MPa) were shown to be comparable or even better than the values obtained for Control (cement) mortars (37.6 MPa and 4.1 MPa). The better production of hydration products leading to the densification of the cement-FA matrix in FCNT@GO-FCMs is attributed to the synergic effect of fly ash and carbon nanomaterials in the mortar sample as examined by FE-SEM and XRD studies. Mercury Intrusion Porosimetry (MIP) showed porosity decline by 34.7%, 51.4%, and 57.8% for FCNT-FCMs, GO-FCMs and FCNT@GO-FCMs in comparison to Control (FA), respectively.

Form-stable and light-to-thermal conversion properties of comb-like polymer composite phase change materials for thermal management application

In this paper, composite phase change materials (cPCMs) were prepared by the impregnation method with poly(methyl vinyl ether-alt-maleic anhydride)-g-octadecanol (PM18) comb-like polymer as PCMs and reduced graphene oxide-carbon nanotubes hybrid aerogel (CG-x) that x (the mass ratio between CNT and GO) varies from 0.5 to 2 as supporting matrix. Thermal properties such as phase change enthalpy, thermal repeatability and shape stabilization of cPCMs were investigated by FTIR, DSC, and thermocouple. PM18@CG-x cPCMs exhibit an enhanced shape-stabilization behavior at 80 °C for 30 min and a 300% increased thermal conductivity is realized. PM18@CG-1 cPCMs demonstrate an excellent light-to-thermal conversion capacity and a good thermal energy storage and release ability, and its largest temperature appears at 75.4 °C under 100 mW/cm2 irradiation intensity. Furthermore, the light-to-thermal conversion capability of fabric controlled by the back-bonded PM18@CG-1 slice is investigated, and the influence of irradiation intensity on thermal energy buffering time is also discussed. Through controlling the number of PM18@CG-1 slices, the tailored thermal properties are further analyzed. This method provides a method to approach the shape-stabilized PCMs with good thermal management and photothermal conversion capability.

Balancing the strength and ductility of graphene oxide-carbon nanotube hybrid reinforced aluminum matrix composites with bimodal grain distribution

Graphene oxide-carbon nanotubes hybrid reinforced aluminum matrix composites (GO-CNT/Al) were prepared by powder metallurgy followed by hot extrusion. The strength of the composites was improved by the synergistic effect of carbon nanotubes, in-situ Al4C3 and graphene oxide. Moreover, due to the partially recrystallization of Al matrix promoted by Al4C3, the matrix exhibits a bimodal grain distribution, which helps to enhance strain-hardening and consequently uniform tensile ductility at high flow stresses. Hence the bimodal grain structure of the matrix combined with the nano-reinforcements leads to enhancing of the strength and ductility synergy. The composite shows a high tensile strength of 249 MPa (175 MPa of pure Al) and keeps almost similar tensile ductility with pure Al (uniform elongation of ~23.1%).

Enhancement in mechanical properties of polyamide 66-carbon fiber composites containing graphene oxide-carbon nanotube hybrid nanofillers synthesized through in situ interfacial polymerization

Polyamide 66 (PA66)/carbon fiber (CF) composites with acyl chloride-functionalized GO (AGO) and carbon nanotubes (CNTs) as hybrid fillers were prepared through in situ interfacial polymerization. The optimal ratio of AGO to CNTs in terms of hydrogen bonding in the composites was determined to be 2:1 via thermochemical analyses of the as-prepared PA66/AGO-CNT composites. The optimized hybrid filler-reinforced PA66/CF composites showed improvements in the interfacial shear strength, tensile strengh and storage modulus by 160, 136 and 300%, respectively, compared to the control sample, as well as high damping properties due to an enhanced transcrystalline interphase. The superior interfacial bonding between CF and PA66 is attributed to hydrogen bonding, enhanced dispersion, and the mechanical interlocking effect induced by AGO-CNT hybrids, which lead to effective energy absorption and load transfer.

Reinforced impermeability of cementitious composites using graphene oxide-carbon nanotube hybrid under different water-to-cement ratios

The prominent dispersibility of graphene oxide (GO) and superior mechanical properties of multi-walled carbon nanotubes (MWCNTs) make them potential materials for reinforcing cementitious composites. The aims of this study were to investigate the effectiveness and mechanisms of GO/MWCNT admixtures on the impermeability of cementitious composites. Comparative tests concerning the transport properties between plain cement pastes and GO/MWCNT-OPC pastes at different water-to-cement (W/C) ratios were conducted in this study. Mercury intrusion porosimetry (MIP) tests were carried out to characterize the pore structures of the cement pastes, and the fractal dimensions were utilized to exploit the relationship between the pore structures and permeability-related properties. Power’s model, general effective media (GEM) theory, and scanning electron microscopy (SEM) images were used to illustrate the mechanism of pore structure enhancement. The results imply that mixing GO/MWCNTs into cementitious composites enhances the impermeability of hardened pastes, and the reinforcing efficiency rate in impermeability decreases linearly with the increment of W/C ratio. The fractal dimensions based on the MIP data characterized the pore structures and predicted the transport properties with considerable accuracy. Furthermore, the role of GO/MWCNTs as nucleating sites for hydration reaction and net-like distribution in the composites may explain the impermeability enhancement mechanism induced by the additional GO/MWCNTs. However, GO/MWCNTs tend to re-agglomerate due to the longer setting times at high W/C ratios and lead to a nonuniform distribution of hydration products, which is responsible for the incompetent reinforcing effects.

Effect of graphene oxide-carbon nanotube hybrid filler on the mechanical property and thermal response speed of shape memory epoxy composites

Shape memory polymers (SMPs) will come to act an indispensable part in numerous aspects of human activity. However, the low mechanical strengths and thermal conductivities of SMPs have largely restricted their applications. Remarkable improvements in the mechanical properties and thermal conductivities of SMPs via introducing thermal conductivity fillers have been achieved, though the fillers acted as obstructors or promoters for the thermal response speed of SMPs were unclear. In the present study, ternary hybrid polymeric shape memory composites of graphene oxide/carbon nanotube/waterborne epoxy (GO/CNT/WEP) were fabricated, where GO acted as a non-covalent dispersant for CNT in WEP and as a reactive secondary reinforcing agent to improve the mechanical strength and thermal conductivity of WEP. The experimental results showed that GO and CNT were uniformly dispersed and well incorporated into WEP matrix, significantly enhanced the mechanical properties, thermal conductivity and thermal response speed of the GO/CNT/WEP composites. Moreover, the thermal response speed of the shape memory composites was controlled by their thermal conductivity at low filler content, while the storage modulus was the dominant factor for the thermal response speeds of the shape memory composites at filler content higher than 2 wt%.

Influence of ultrasonication on the dispersion and enhancing effect of graphene oxide–carbon nanotube hybrid nanoreinforcement in cementitious composite

Nano-engineering cement binder using a hybrid of carbon nanotubes (CNTs) and graphene oxide (GO) combines the superior mechanical properties of CNTs and the good dispersibility and affinity of GO. Ultrasonication is a key process implemented in the dispersion of CNTs and GO. The present study characterizes the effect of ultrasonication on the dispersion and size of the GO/CNT particles by using an ultraviolet spectrophotometer and Zetasizer μV detector, respectively. The mechanical properties of GO/CNT-OPC pastes treated with different ultrasonication time and power levels were tested and their microstructure was investigated using scanning electron microscopy and mercury intrusion porosimetry. The results of this study not only reveal that differences in ultrasonication can cause the mechanical properties of the GO/CNT-OPC composite to vary by −11.7–78.8% but also show that the effect of the amount of ultrasonication energy can vary significantly when different ultrasonication time or power levels are adopted. The porosity of the composite is found to have a nonlinear correlation with the ultrasonication. The findings of this study can promote understanding of GO/CNT-OPC composites and help to guide the implementation of ultrasonication in the future.

Graphene–Carbon Nanotube Aerogel with a Scroll-Interconnected-Sheet Structure as an Advanced Framework for a High-Performance Asymmetric Supercapacitor Electrode

Carbon nanomaterials have received much attention due to their good electrochemical performance as electrode materials and as substrates for pseudocapacitive materials. Herein, the graphene–carbon nanotube aerogel (GCA) has been constructed by direct cryodesiccation from the aqueous dispersion of a graphene oxide–carbon nanotube hybrid, the so-called “sol-cryo” method, followed by high-temperature carbonization. The as-obtained GCA with a unique sheet-scroll conjoined architecture not only displays an excellent electrical double-layer capacitive performance but also performs as an ideal three-dimensional template for the perpendicular immobilization of Ni(OH)2 nanosheets. The capacitance of Ni(OH)2@GCA is 1208 F g–1 at 1 A g–1 with 88% retention after 2000 cycles. The Ni(OH)2@GCA//GCA asymmetric supercapacitor exhibits a high energy density of 30 Wh kg–1 at a power density of 820 W kg–1. In addition, this template-free sol-cryo method possesses simplicity and large-scale availability, which provides a nov...

Phase transition and anomalous rheological properties of graphene oxide-carbon nanotube acrylonitrile butadiene styrene hybrid composites

Acrylonitrile butadiene styrene (ABS) nanocomposites with multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (RGO) and graphene oxide-carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites were prepared using twin screw extruder. The effect of these reinforcements on dynamic rheological properties of composites was studied. Different carbon nanofillers significantly enhanced the viscoelastic properties of nanocomposites. The rheological studies showed that the material undergoes viscous to elastic transition for 5 wt % MWCNTs, 10% RGO and 7% GCNTs reinforced in ABS matrix. GCNTs hybrid composites show a higher dispersion as well as effectiveness for increased filler amount as compared to RGO and MWCNTs based ABS composites. The dynamic intersection frequency of GCNTs-ABS composites indicates its superiority over MWCNTs and RGO based ABS composites by solving the problem of restacking of graphene and agglomeration of MWCNTs. Modified Carreau-Yasuda model and Hershcel-Bulkey model have been used to determine the yield stress of the composites and van Gurp-Palmen plot to determine the viscoelastic properties. These models were used to compare the theoretical results with experiment data. Dynamic rheological measurements revealed the viscous-like (G">G') behavior at the lower loading of filler and elastic like (G'>G") behavior at higher loading of carbon nanofiller.

Flexible Micro-Supercapacitors Based on Interdigitated Electrodes of Flash Lamp Annealed Graphene and Carbon Nanotube Composites

We fabricate graphene-carbon nanotube based flexible micro-supercapacitor, using flash lamp annealing. Flash lamp annealing enables the rapid reduction of graphene oxide to graphene in a millisecond time scale and also favors the formation of highly ordered open network of graphene. Interdigitated micro-sized patterns were designed on graphene oxide-carbon nanotube hybrid thin film via laser ablation. Then, flash lamp annealing process converts the insulating graphene oxide to reduced graphene oxide that is conducting at accurate locations. The resulting interdigitated flash lamp annealed graphene-carbon nanotube was then tested as electrode materials for electrochemical capacitors. The electrochemical performance of the electrodes will be presented in terms of volumetric capacitance, energy density and power density.

Synergetic effect of graphene oxide-carbon nanotube on nanomechanical properties of acrylonitrile butadiene styrene nanocomposites

Herein, multiwall carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), graphene oxide-carbon nanotubes (GCNTs) hybrid reinforced acrylonitrile butadiene styrene (ABS) nanocomposites have been prepared by micro twin screw extruder with back flow channel and the effect of different type of fillers on the nanomechanical properties are studied. The combination of both graphene oxide and CNT has enhanced the dispersion in polymer matrix and lower the probability of CNTs aggregation. GCNTs hybrid have been synthesized via novel chemical route and well characterized using Raman spectroscopic technique. The nanoindentation hardness and elastic modulus of GCNTs-ABS hybrid nanocomposites were improved from 211.3 MPa and 4.12 GPa of neat ABS to 298.9 MPa and 6.02 GPa, respectively at 5wt% GCNTs loading. In addition to hardness and elastic modulus, other mechanical properties i.e. plastic index parameter, elastic recovery, ratio of residual displacement after load removal and displacement at the maximum load and plastic deformation energy have also been investigated. These results were correlated with Raman and X-ray photoelectron spectroscopic (XPS) techniques and microstructural characterizations (scanning electron microscopy). Our demonstration would provide guidelines for the fabrication of hard and scratches nanocomposite materials for potential use in, automotive trim components and bumper bars, carrying cases and electronic industries and electromagnetic interference shielding.

Effect of reduced graphene oxide-carbon nanotubes hybrid nanofillers in mechanical properties of polymer nanocomposites

Graphene and carbon nanotubes (CNTs) have tremendous interest as reinforcing fillers due to their excellent physical properties. However, their reinforcing effect in polymer matrix is limited due to agglomeration of graphene and CNTs within the polymer matrix. Mechanical properties by the admixture of reduced graphene oxide (rGO) and CNTs in Poly (methyl methacrylate) (PMMA) prepared by solution mixing method has been investigated. The prepared samples are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy. The hybrid composite shows improvement in the mechanical properties compared to rGO/PMMA and MWCNTs/PMMA composites due to better interaction between rGO-MWCNTs and polymer matrix.

Graphene oxide-carbon nanotubes hybrid co-electrodeposited on graphite sheet as an excellent electrocatalytic material for [VO]2+/[VO2]+ redox reaction in VRFBs

A highly effective GO-CNT/graphite sheet as electrochemical active material for [VO]2+/[VO2]+ redox pairs in vanadium redox flow battery (VRFB) has been developed. The modified sheet was fabricated by co-electrochemical reduction of functionalized carbon nanotubes (fCNTs) and graphene oxide (GO) on graphite sheet. The structures and electrochemical properties of GO-CNT/graphite sheet were studied by scanning electron microscopy, transmission electron microscopy, contact angle measurement, Fourier-transform infrared spectroscopy, Raman spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry (CHA). The morphology studies showed that GO-CNTs hybrid has been uniformly deposited on the surface of graphite sheets. Electrochemical measurements are carried out in a three-electrode half-cell to characterize the electrochemical properties of the GO-CNT/graphite sheet towards the VO2+/VO2+ redox reactions. Results showed that the GO-CNT/graphite electrode exhibits high peak current density and low charge-transfer resistance towards the [VO]2+/[VO2]+ redox reactions compared to bare graphite sheet, confirming good electrocatalytic activity and kinetic reversibility of the modified electrode. The enhanced electrochemical activity can be attributed to the synergetic catalytic effect of GO-CNTs and the large numbers of oxygen-containing functional groups on the GO-CNTs hybrid which can provide more active sites to catalyze the [VO]2+/[VO2]+ redox reactions.

Significant improvement in static and dynamic mechanical properties of graphene oxide–carbon nanotube acrylonitrile butadiene styrene hybrid composites

Herein, hybridization of graphene nanosheets and carbon nanotubes (CNTs) has been made to solve the problem of restacking of graphene nanosheets and agglomeration of CNTs. The multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (RGO) and graphene oxide–carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites have been prepared using micro-twin-screw extruder. The effect of these reinforcements on static and dynamic mechanical properties of composites is studied. The ultimate tensile strength and elastic modulus for 7 wt.% GCNT–ABS composites show enhancement of 26.1 and 71.3% over pure ABS matrix, respectively. Various parameters such as coefficient “C” factor (the ratio of storage modulus of the composite to polymer in glassy and rubbery regions), degree of entanglement, crosslink density and adhesion factor have been calculated to analyze the interaction between fillers and polymer matrix. The 3-D hybrid structure of GCNTs overcomes the associated problem of CNTs agglomeration and graphene restacking. GCNT hybrid composites show higher dispersion as well as effectiveness for increased filler amount as compared to RGO and MWCNTs based composites. GCNTs prove its superiority over MWCNTs and RGO by showing a synergistic effect in the glass transition temperature and storage modulus. Raman spectroscopy and scanning electron microscopy are used to confirm the interaction and distribution of the filler and matrix, respectively.

A sol–gel approach to produce highly dispersed graphene oxide–carbon nanotube hybrid reinforcement into alumina matrix

A sol–gel approach to produce highly dispersed graphene oxide–carbon nanotube hybrid reinforcement into alumina matrix

Preparation and characterization of PEDOT:PSS/reduced graphene oxide–carbon nanotubes hybrid composites for transparent electrode applications

Hybrid composites have been prepared by solution processing method using various MWCNT concentrations in reduced graphene oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (rGO-PEDOT:PSS) matrix. Structural and morphological characteristics of the prepared composite films have been characterized by X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, Raman spectroscopy, UV–visible spectroscopy and Fourier transform infrared spectroscopy. The electrical transport measurement of composites conducted by four-point contacts shows increase in conductivity with MWCNT wt% in the composite system. The enhanced electrical conductivity as a result of improved dispersion of MWCNTs and rGO has been observed barely affecting the optical properties in the visible region. The observed improvement in electrical properties barely affecting its optical properties in the visible region can be attributed to synergistic effect of MWCNTs and rGO networks on the composite. This result suggests that such hybrid composite materials could be used as transparent conductor applications in optoelectronic devices.

Graphene oxide-carbon nanotube hybrid assemblies: cooperatively strengthened OH···O[double bond, length as m-dash]C hydrogen bonds and the removal of chemisorbed water.

Owing to their great significance for energy storage and sensing applications, multi-layer papers consisting of graphene oxide-carbon nanotube (GO-CNT) hybrid sheets were prepared by in situ exfoliation of graphite oxide in the presence of oxidized CNTs (oCNTs). For the first time we elucidate the influence of oCNTs on chemisorbed water (CW), i.e. the water molecules inherently bound to the oxygen functional groups (OFGs) of graphene oxide (GO) and responsible for irreversible structural damage upon thermal reduction processes. We show that oCNTs self-assemble onto GO sheets during the liquid phase processing steps by forming cooperatively strengthened OH···O[double bond, length as m-dash]C hydrogen bonds between the carboxylic groups of the oCNTs and OFGs of GO. At oCNT amounts of about 10 to 15 wt% this leads to the displacement of considerable amounts of CW without altering the original chemical composition of GO. The thermally reduced GO-CNT (rGO-CNT) papers reveal improved sp2 character and an enhancement of the specific capacitance by 75% with respect to thermally reduced GO (rGO), largely due to the effective removal of CW by oxidized CNTs. These findings disclose the relevance of the cooperative hydrogen bonding phenomena in graphene oxide paper/film electrodes for the development of improved electrochemical energy storage and sensing devices.

The removal of uranium(VI) from aqueous solution by graphene oxide–carbon nanotubes hybrid aerogels

Novel graphene oxide–carbon nanotubes (GO–CNTs) hybrid aerogels were fabricated via a freeze-drying method using aqueous solutions of GO and CNTs. The resulting aerogels were characterized by scanning electron microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy and thermal gravity analysis. The three-dimensional GO–CNTs aerogels were used to remove uranium(VI) from aqueous solutions. The results showed that GO–CNTs aerogels had high removal ability to uranium(VI) and could be a promising sorbent for many environment applications.

Selective Dye Adsorption by pH Modulation on Amine-Functionalized Reduced Graphene Oxide–Carbon Nanotube Hybrid

Simultaneous functionalization, reduction, and hybridization of graphene oxide in graphene oxide–multiwall carbon nanotube hybrid were carried out by p-phenylenediamine (rGO–CNT–PPD). The adsorption properties of the hybrid for selective removal of methyl violet (MV) and methyl orange (MO) from their mixture were investigated under different experimental conditions. The adsorption was correlated with the effects of pH, contact time, and temperature. Changing the pH of the solution modulates the selectivity of adsorption behavior of the hybrid. At pH 7.0, it can remove 99.7% MV selectively from the mixture, whereas at pH 3.0, it can remove MO selectively having 98% removal efficiency. The maximum adsorption capacities (qm) of the hybrid for MV and MO are 298 and 294 mg/g, respectively, at 298 K; these values are higher than several previously reported qm values. The kinetics data for both dyes can be well fitted with the pseudo-second-order kinetics model, and the adsorption of both dyes followed a Langmuir adsorption isotherm. The adsorbent can be easily regenerated and reused, and its activity remains the same even after five adsorption–desorption cycles. The rGO–CNT–PPD hybrid could be a promising adsorbent for selective removal of synthetic dyes from their mixture by pH modulation.

Improvement of the mechanical properties and thermal conductivity of poly(ether-ether-ketone) with the addition of graphene oxide-carbon nanotube hybrid fillers

An organic/inorganic nanocomposite was prepared based on poly(ether-ether-ketone) (PEEK) containing either ethyl-aminated or phenyl-aminated GO/MWCNT (E-GC or P-GC) hybrid fillers. The introduction of E-GC and P-GC to the PEEK matrix improved the thermal conductivity and mechanical properties. The thermal conductivities of 1wt.% GO/PEEK increased to 0.36W/mK and the introduction of 0.5wt.% ethyl-aminated and phenyl-aminated MWCNT with 1wt.% chlorinated GO in the PEEK showed enhanced thermal conductivities. The storage modulus of PEEK composite was higher than that of raw PEEK, and the P-GC containing PEEK had the most enhanced value.