Carbon Nanotubes-graphene Oxide Research Articles

Numerical assessment of viscoelastic tetra hybrid nanofluid flow across a stretchable rotatory disk under the Soret and Dufour aspects

PurposeFluid flows through rotatory disks are encountered in industrial and practical engineering processes, such as computer storage devices, gas turbine rotators, rotating machinery, air cleaning machines, etc. The primary purpose of this research is to examine the combined aspects of variable electrical conductivity, thermal radiation, Soret and Dufour effects on a magnetohydrodynamic Maxwell single-walled carbon nanotubes–graphene oxide–multi-walled carbon nanotubes–copper (SWCNT–GO–MWCNT–Cu)/sodium alginate tetra-hybrid nanofluid flow through a stretchable rotatory disk.Design/methodology/approachThe modeled administrative equations of the present flow problem are converted to a non-dimensional system of ordinary differential equations by applying suitable similarity conversion and then solved numerically by implementing the bvp4c method. The impressions of noteworthy dimensionless parameters on velocity, temperature, concentration distributions, Nusselt number, skin friction and Sherwood number are reported via graphs and tables.FindingsThe authors figured out that the developed values of the rotation parameter diminish the temperature but enhance both the radial and angular velocities. Further, the mass and heat transmission rates are better for tetra-hybrid nanofluids than for ternary and hybrid nanofluids.Originality/valueThe present study emphasizes a special type of fluid called the tetra-hybrid nanofluid. The existing literature has not discussed the Maxwell tetra hybrid nanofluid flow through a stretchable rotatory disk with variable electrical conductivity. Besides, the novel aspects of magnetohydrodynamics, thermal radiation, Soret and Dufour effects are also incorporated into the present flow problem.

Zinc oxide bridges the nanofillers to enhance the wear resistance and stability of triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have received widespread attention as a means of harvesting mechanical energy from the environment and converting it into electricity. As people continue to explore the field of infinite sensors, traditional TENGs have faced persistent challenges in practical application, mainly due to the poor abrasion resistance and stability of the existing polymers commonly used. Herein, the polyphenylene sulfide (PPS) was melt blended with liquid crystal polymer (LCP) to be used as matrix, and the interfacial bonding strength between the matrix and filler was improved by zinc oxide (ZnO) grafted carbon nanotubes/graphene oxide (CNTs/GO). Under friction conditions of 100 N load and 0.5 m/s, the friction coefficient and wear rate of resultant nanocomposites were significantly reduced to 0.2 and 2.09 × 10-5 mm3/N, respectively. The abrasion resistant TENG (AR-TENG) was fabricated based on 0.3ZnO/CNTs/GO/LCP/PPS exhibited outstanding electrical output performance, which was attributed to the high dielectric constant of 5.3, improved surface roughness and interfacial contact area of composites. Consequently, this study reported a novel approach to tailor AR-TENG into a highly abrasion resistant and stable sensor. This customization enabled the AR-TENG to operate reliably in harsh environments (high temperatures and humidity), thereby expanding its potential applications.

Electrochemical sensor based on PEDOT/CNTs-graphene oxide for simultaneous determination of hazardous hydroquinone, catechol, and nitrite in real water samples

Hydroquinone (HQ), catechol (CC) and nitrite (NT) are considered aquatic environmental pollutants. They are highly toxic, harm humans’ health, and damage the environment. Thus, in the present work we introduce a simple and efficient electrochemical sensor for determination of HQ, CC, and NT simultaneously in wastewater sample. The sensor is fabricated by modifying the surface of a glassy carbon electrode (GCE) by two successive thin films from poly(3,4-ethylenedioxythiophene) (PEDOT) and a mixture of carbon nanotubes-graphene oxide (CNT-GRO). Under optimized conditions the HQ, CC, and NT are successfully detected simultaneously in wastewater sample with changing their concentrations in the ranges (0.04 → 100 µM), (0.01 → 100 µM) and (0.05 → 120 µM), the detection limits are 8.5 nM, 3.8 nM and 6.1 nM, respectively. Good potential peak separations: 117 mV and 585 mV are obtained between the HQ-CC, and CC-NT. The sensor has an excellent catalytic capability toward the oxidation of HQ, CC, and NT due to good synergism between its composite components: PEDOT, GRO and CNTs. The features of the sensor are large active surface area, good electrical conductivity, perfect storage stability, good reproducibility, anti-interference capability and accepted recovery rate for HQ, CC, and NT determination in wastewater sample.

Understanding the role of graphene oxide nanoribbons–functionalized carbon nanotubes–graphene oxide (GNFG) complex in enhancing the fire resistance of cementitious composites

• The effect of GNFG on the fire resistance of cementitious composites was tested. • GNFG had better thermal stability than CNTs at high temperatures. • GNFG presented excellent dispersion and promoted the hydration of cement clinkers within the cement paste. • GNFG better preserves the microstructure and mechanical strength of cement paste at high temperatures. In this study, the enhancement effect of synthesized graphene oxide nanoribbons–functionalized carbon nanotubes–graphene oxide (GNFG) complex on the fire resistance of cementitious composites was investigated by comparing it with two traditional nano-reinforcements, carbon nanotubes (CNTs) and graphene oxide (GO). Ordinary Portland cement (OPC) paste reinforced with GNFG, CNTs, and GO at 0.05 wt% were heated to a target temperature of 200, 400, 600, and 800 °C, and the changes in mass loss, bulk density, surface morphology, and mechanical strength were compared with unreinforced OPC paste. The transformation of the microstructure and variation in the hydration products were also analyzed. GNFG exhibited excellent dispersion in the aqueous solution and good thermal stability at high temperatures. Furthermore, it promoted the hydration of anhydrous cement clinkers to produce a denser microstructure and limit the deterioration of the microstructure and mechanical properties of the cement paste at high temperatures. These results suggest that GNFG can play a crucial role as a novel nano-reinforcing agent to improve the mechanical properties and fire resistance of cementitious materials.

Synthesis of Highly-Dispersed Graphene Oxide Nanoribbons-Functionalized Carbon Nanotubes-Graphene Oxide (GNFG) Complex and Its Application in Enhancing the Mechanical Properties of Cementitious Composites.

In this study, a graphene oxide nanoribbons–functionalized carbon nanotubes–graphene oxide (GNFG) complex was hydrothermally synthesized as a nanomaterial for reinforcing cementitious composites, using a modified Hummers’ method. Three types of components existed in the GNFG: Type I, the functionalized carbon nanotubes–graphene oxide nanoribbons (FCNTs–GNR); and types II and III are graphene oxide (GO) and functionalized carbon nanotubes (FCNTs), respectively, which exist independently. The dispersivity of GNFG and its effects on the mechanical properties, hydration process, and microstructures of cement pastes were evaluated, and the results were compared with those using cement pastes incorporating other typical carbon nanomaterials. The results demonstrated that dispersion of GNFG in aqueous solutions was superior to that of the CNTs, FCNTs, and GO/FCNTs mixture. Furthermore, the highly-dispersed GNFG (0.05 wt.%) improved the mechanical properties of the cement paste after 28 days of hydration and promoted the hydration of cement compared to CNTs, GO, and GO/FCNTs mixture (0.05 wt.%). The results in this study validated the feasibility of using GNFG with enhanced dispersion as a new nano-reinforcing agent for various cementitious systems.

Enhanced electrocatalytic H2S splitting on a multiwalled carbon nanotubes-graphene oxide nanocomposite

A non-precious graphene oxide (GO) based oxidized multiwalled carbon nanotubes (MWCNTs) metal-free electrocatalytic system was fabricated using a chemical method and further used for the electrocatalytic oxidation of hydrogen sulphide (H2S) to hydrogen.

Production and investigation of mechanical properties and electrical resistivity of cement-matrix nanocomposites with graphene oxide and carbon nanotube reinforcements

In this study, two groups of the cement-matrix nanocomposites (CMNC) were produced. The first group was reinforced with either carbon nanotubes (CNT) or graphene oxide (GO), where the equivalent weight% of cement equaled 0.05, 0.1, and 0.15. The second group was reinforced with the hybrid CNT–GO, where the equivalent weight% of cement equaled 0.05 CNT–0.1 GO and 0.1 CNT–0.05 GO. Before producing nanocomposites, the distribution of the nanoreinforcement in water had been investigated using spectrophotometric analysis, scanning electron microscopy, and transmission electron microscopy. The physical and mechanical behaviors of different samples of the produced nanocomposites were evaluated by electrical resistivity and compressive strength tests. The effects of the types and the percentages of the nanoreinforcements on the electrical and mechanical properties of the produced nanocomposites were measured. The results showed that the electrical resistivity of the produced composites decreased with increasing the percentage of CNT, whereas the compressive strength of the cement paste initially increased and then decreased. Also, with increasing the percentage of GO, the compressive strength of the produced composites increased, while the electrical resistivity decreased. Moreover, in comparison with the composites reinforced with either CNT or GO, by using the hybrid reinforcement (CNT/GO), the compression strength increased, while the electrical resistivity decreased.

Magnetic Carbon Nanotubes/Graphene Oxide Nanocomposites: One-Step Controllable Production, and Their Excellent Microwave Absorption Capabilities

In this research, three-dimensional (3D) hierarchical networks of magnetic carbon nanotubes/graphene oxide (CNTs/GO) nanocomposites (NCs) were synthesized by a one-step hydrothermal method with the idea of constructing more interface contacts, double loss mechanism and synergy effect. The obtained results showed that the content of NCs gradually transitioned from CoCO3 to CoxFe3-xO4. And CoCO3-CoxFe3-xO4/CNTs/GO quaternary NCs and CoxFe3-xO4/CNTs/GO ternary NCs could be selectively synthesized when the Co:Fe molar ratio decreased from 1:1 to 1:3. The as-prepared samples displayed excellent microwave absorption properties (MAPs) in terms of the minimum reflection loss (RLmin) and the corresponding absorption bandwidth (FBcor) with the reflection loss values lower than -10 dB. The RLmin and large FBcor values for the as-prepared samples were -54.69 dB and 2.36 GHz, -63.99 dB and 2.48 GHz, -63.36 dB and 2.68 GHz, respectively. The designed 3D hierarchical networked structure of magnetic GO/CNTs NCs displayed outstanding comprehensive MAPs, which could deliver a practical and effective strategy to develop high-performance microwave absorbers, taking into account their low cost, lightweight, and high stability.

MWCNTs-GONRs/Co3O4 electrode with needle-like arrays for outstanding supercapacitors

Multiwalled carbon nanotubes-graphene oxide nanoribbons (MWCNTs-GONRs) exhibit high specific surface area and good electroconductivity because of their unique three-dimensional cross-linking structure with the properties of both CNTs and GONRs. In this study, a hydrothermal method was employed to anchor MWCNTs–GONRs onto a Ni foam (NF) to obtain a precursor substrate. Subsequently, Co3O4 arrays were grown on the NF substrate to synthesize a MWCNTs–GONR/Co3O4 electrode. The electrode showed a capacitance of 846.2 F g−1 at 1 A g−1 and a capacitance retention of 90.1% after 3000 cycles. Furthermore, MWCNTs–GONRs/Co3O4 and active carbon (AC) were used as the positive and negative electrodes, respectively, to assemble a supercapacitor, which delivered a maximum energy density of 38.23 W h kg−1 and a high power density of 6.80 kW kg−1. In addition, the specific capacitance of the device reached a maximum of 91.5% after 9000 cycles. Thus, the MWCNTs–GONRs/Co3O4 electrode showed huge potential for supercapacitor applications.

Carboxylated carbon nanotubes-graphene oxide aerogels as ultralight and renewable high performance adsorbents for efficient adsorption of glyphosate

Environmental contextGlyphosate is a highly effective and widely used organophosphorus pesticide, but its residues can harm the environment and human health. We report a carboxylated carbon nanotubes-graphene oxide aerogel that can efficiently remove glyphosate from water. This technology has great application prospects in dealing with water contaminated with glyphosate. AbstractGlyphosate, an organophosphorus pesticide, has received considerable attention in recent years owing to its carcinogenic potency. The technologies that remove glyphosate in the environment, especially in water, are important. In this work, we prepare a carboxylated carbon nanotubes-graphene oxide aerogel (cCNTs-GA) by the freeze-drying method for the adsorption of glyphosate. The prepared aerogel exhibits an ultra-low density (7.30mgcm−3), good morphology and strong mechanical strength. Meanwhile, a NaOH solution (0.5molL−1) is selected as an eluent and the adsorption parameters for the adsorption of glyphosate are optimised. The properties of the adsorbents after multiple repetitions and the adsorption mechanism of the cCNTs-GA are also studied. The results show that the adsorbent can be recycled more than 20 times and maintains a good adsorption performance. The maximum adsorption capacity of glyphosate at pH 3 is calculated from the Langmuir isotherm model (546mgg−1 at the temperature of 298K), and the cCNTs-GA exhibits a high adsorption affinity and adsorption capacity for glyphosate, as determined by the partition coefficient (PC). The pseudo-second-order kinetic model fits well to the dynamic behaviour. The equilibrium adsorption process follows the Langmuir isotherm model and the adsorption process is mainly controlled by the intraparticle diffusion model. Furthermore, thermodynamic analysis indicates that the adsorption of glyphosate on the cCNTs-GA is exothermic and spontaneous. The adsorbent is used to remove glyphosate from waste water and the adsorption capacity of the cCNTs-GA for glyphosate is higher than other adsorbents, which indicates that the developed adsorbent has a great potential application in environmental pollution treatment.

MWCNTs-GONRs/Co3O4@Ni(OH)2 core-shell array structure with a high performance electrode for supercapacitor

A high-performance electrode for a supercapacitor was developed through a hydrothermal method that entailed the loading of multiwalled carbon nanotubes-graphene oxide nanoribbons (MWCNTs-GONRs) onto a Ni foam (NF) to create a substrate. A core shell array structure of Co3O4@Ni(OH)2 was added onto the substrate and grown. It anchored on the substrate, creating a MWCNTs-GONRs/Co3O4@Ni(OH)2 electrode. The electrode had good electrochemical properties such as a high specific capacitance (2654.7 F g−1), high charge-discharge rates, and a remarkable cycling stability. This was possibly a result of the synergistic effect of the 3D core shell array structure and the MWCNTs-GONRs. We also assembled asymmetric supercapacitors using MWCNTs-GONRs/Co3O4@Ni(OH)2 and active carbon as the positive and negative electrodes, respectively. The supercapacitor had a maximum energy density of 74.85 Wh kg−1 and high power density of 6.80 kW kg−1, with good cycling stability (83.31% capacitance retention after 10,000 cycles). The electrodes we developed and produced are promising and feasible for practical energy application requirements.

Excellent performance MWCNTs-GONRs/Ni(OH)2 electrode for outstanding supercapacitors

Abstract Due to the unconventional properties of MWCNTs-GONRs (multiwalled carbon nanotubes-graphene oxide nanoribbons), we have tried to use it as a carbon resource for supercapacitors. MWCNTs-GONRs/Ni(OH)2 electrode was obtained by hydrothermal method. Velvet α-Ni(OH)2 was prepared above NF (nickel-foam) loaded with MWCNTs-GONRs. This layered design can effectively promote the diffusion of ions and increase the active site for MWCNTs-GONRs/Ni(OH)2 electrode, thus enhancing the electrochemical performance. The electrode exhibits extraordinary electrochemical performances in electrochemical testing, such as supernal specific capacitance (1713.2 F g−1) and prominent working time. In addition, supercapacitors was assembled with MWCNTs-GONRs/Ni(OH)2 and active carbon as materials. Which represents a prominent energy density (41.23 Wh kg−1), high power (6.80 kW kg−1) and prominent cycling stability property (95.18%, 3000 times). The electrode prepared in this work provides a clue to enlighten people for energy storage.

Thermal, mechanical and morphological study of carbon nanotubes-graphene oxide and silver nanoparticles based polyurethane composites

Polyurethane composite foams were prepared by solvent casting method with the addition of carbon nanotubes—graphene oxide and silver nanoparticles. Changes in micro-structural phases of the polymers were analyzed by x-ray diffraction (XRD). Morphological changes in polyurethane foams after dispersion of nanofillers were analyzed by using Field emission Scanning Electron Microscope (FESEM). Fourier Transform Infrared Spectroscopy (FTIR), XRD and FESEM analysis have confirmed the successful incorporation of nanotubes and nanoparticles into the polymer matrix. Further, TGA (Thermo-gravimetric analysis) analysis showed an increase in thermal stability of hybrid composite foam. The addition of nanofillers in the polyurethane foam has increased the tensile strength by 323%. Hybrid foam was conductive in nature and the conductivity is 2 × 10−4 S cm−1.

Highly efficient removal of Gd(III) using hybrid hydrosols of carbon nanotubes/graphene oxide in dialysis bags and synergistic enhancement effect

The spontaneous stacking of graphene oxide (GO) nanosheets for the adsorptive remediation of wastewater has been severely restricting their inherent adsorption ability from being brought into full play. Herein, hydrosols of carbon nanotubes/graphene oxide (CNTs/GO) sealed in dialysis bags were utilized for the highly efficient and re-pollution-free removal of trace Gd(III) from water for the first time. The effects of mass ratio between CNTs and GO (MCNTs: MGO), pH value and contact time on Gd(III) adsorption of CNTs/GO hybrid hydrosol (MCNTs: MGO = 1:6) as well as its adsorption kinetics and thermodynamics were studied by comparison with GO hydrosol. The pH-dependent desorption and regeneration of the CNTs/GO hybrid hydrosol were also investigated. The results showed that CNTs/GO hybrid hydrosols with MCNTs: MGO from 1:8 to 1:2 exhibited the remarkable synergistic enhancement effect. The CNTs/GO hybrid hydrosol with MCNTs: MGO = 1:6 had the theoretical maximum Gd(III) adsorption capacity of 534.76 mg·g−1 (pH = 5.9, t = 60 min, T = 303 K) with a leap of 86.42% compared to GO and remained the sorption capacity of 347.83 mg·g−1 at the fourth cycle, showing the excellent regeneration performance. Moreover, the adsorption of Gd(III) on CNTs/GO hybrid hydrosols agreed well with the pseudo-second-order model and Langmuir isotherm adsorption model. In prospect, CNTs/GO hybrid hydrosols in dialysis bags promises of extensive application in the highly efficient and re-pollution free elimination of metal ions from water.

2D Janus Hybrid Materials of Polymer‐Grafted Carbon Nanotube/Graphene Oxide Thin Film as Flexible, Miniature Electric Carpet

Ultrathin, freestanding polymer hybrid film with macroscopic sizes and molecular thicknesses have received significant interest due to their applications as functional devices, microsensors or nanoactuators. Herein, a 2D Janus hybrid of polymer‐grafted carbon nanotubes/graphene oxide (CNTs/GO) thin film is fabricated using microcontact printed CNTs/GO as photo active surface to grow polymer brushes by self‐initiated photografting and photopolymerization selectively from one side of CNTs/GO film. This achieved 2D Janus hybrid materials with grafted polymer layer as insulative carpet and supported CNTs/GO thin film as conductive element have the potential application as flexible and miniature electric carpet for heating micro‐/nano devices locally.