Mixture Of Carbon Nanotubes Research Articles

One-step gas-phase construction of carbon-coated Fe3O4 nanoparticle/carbon nanotube composite with enhanced electrochemical energy storage

Carbon nanotubes (CNTs) as superior support materials for functional nanoparticles (NPs) have been widely demonstrated. Nevertheless, the homogeneous loading of these NPs is still frustrated due to the inert surface of CNTs. In this work, a facile gas-phase pyrolysis strategy that the mixture of ferrocene and CNTs are confined in an isolated reactor with rising temperature is developed to fabricate a carbon-coated Fe3O4 nanoparticle/carbon nanotube (Fe3O4@C/CNT) composite. It is found the ultra-small Fe3O4 NPs (<10 nm) enclosed in a thin carbon layer are uniformly anchored on the surface of CNTs. These structural benefits result in the excellent lithium-ion storage performances of the Fe3O4@C/CNT composite. It delivers a stable reversible capacity of 861 mA ·h·g−1 at the current density of 100 mA·g−1 after 100 cycles. The capacity retention reaches as high as 54.5% even at 6000 mA·g−1. The kinetic analysis indicates that the featured structural modification improves the surface condition of the CNT matrix, and contributes to greatly decreased interface impendence and faster charge transfer. In addition, the post-morphology observation of the tested sample further confirms the robustness of the Fe3O4@C/CNT configuration.

A Performance Study of CNT/TiO&lt;sub&gt;2&lt;/sub&gt;/ PVA Loaded on the Paper Filter for Benzene Treatment from Cigarette Smoke

This work has studied the performance of benzene treatment from cigarette smoke using the prepared CNT/TiO2/PVA loaded on the paper filter in the air purifier reactor. CNT/TiO2 nanomaterial was prepared from a mixture of carbon nanotubes modified with sulfuric acid and titanium dioxide by a simple mixing method in the ambient temperature. CNT/TiO2 nanomaterial was then loaded on the paper filter by a filtrating technique using 12%w/v polyvinyl alcohol (PVA) as a co-polymer. The weight of CNT/TiO2 loaded on the paper filter was fixed at 3 g. The ratios of CNT: TiO2 was varied at 1:5, 1:10, and 1:15 w/w, respectively. The performance of air purifier using CNT/TiO2/PVA loaded on the paper filter with various ratios was investigated on the photocatalytic activity of benzene treatment from cigarette smoke under visible light. The decreased benzene concentrations were analyzed by GC-FID. As the results, the ratio of CNT/TiO2 loaded on the paper filter at 1:10 showed the highest performance by up to 45%, while the ratio of CNT/TiO2 at 1:15 showed 30% and CNT/TiO2 at 1:5 was the lowest of 22%, respectively. This is because adding the optimum CNT to TiO2 can be improved the adsorption efficiency and the ability to degrade benzene from cigarette smoke. Additionally, CNT also assists in reducing the recombination of TiO2 particles that effect to the high performance on the photocatalytic activity. Therefore, the prepared CNT/TiO2/PVA loaded on the paper filter could be used for the air treatment.

Flexible multimodal sensor inspired by human skin based on hair-type flow, temperature, and pressure

Flexible electronic circuits when integrated with different sensors to mimic the human skin can be referred to as E-skin. E-skin can be used for the monitoring of human health, human-machine interface and humanoids. To mimic skin, a variety of sensors have been studied, including those sensitive to different pressures, temperatures, flows, and strain and humidity levels. Herein, we demonstrate a multifunctional sensor encompassed in a single pixel which is inspired by human skin. The proposed device contains a pressure sensor, a temperature sensor and a piezoresistive hair-type flow sensor, the latter of which is fabricated using mixture of carbon nanotubes and polydimethylsiloxane piezoresistive materials. Additionally, the temperature sensor is printed by means of inkjet printing with MWCNT and Ag nanoparticle ink. Finally, all three sensors are vertically stacked to mimic the human skin, demonstrating interference-free characteristics. This study provides a new and cost-effective approach for multimodal sensor applications.

Synergy effect in hybrid nanocomposites based on carbon nanotubes and graphene nanoplatelets

Hybrid nanocomposites reinforced with a mixture of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) have shown improvement in filler dispersion while providing a cost-effective alternative to CNT monofiller composites. Depending on their composition, hybrid composites can exhibit electrical performance superior to either of the constituent monofiller composites due to synergistic effects. In this work, we develop a three-dimensional tunneling-based continuum percolation model for hybrid nanocomposites filled with hardcore particles of elliptical GNPs and cylindrical CNTs. Using Monte Carlo simulations, parametric studies of the filler content, composition and morphology are carried out to analyze the conditions required for synergy in percolation onset and electrical conductivity. Our results suggest that for hybrid systems with well-dispersed fillers, the electrical performance is linked to the number of tunneling junctions per filler inside the percolated network of the nanocomposites. More importantly, hybrid composites filled with specific morphology of GNP and CNT, exhibit synergy in their electrical performance when the monofiller composites of each of those exact fillers have similar percolation onset values. The simulations results are in agreement with relevant experimental data on hybrid nanocomposites.

Frequency modulation of laser ultrasound transducer using carbon nanotube-coated polyethylene microsphere.

An ultrasound transducer was fabricated by dropping a multi-walled carbon nanotube solution containing a mixture of carbon nanotubes and ethoxyethanol directly on the surface of polyethylene microspheres. The frequency modulation depended on the diameter of the polyethylene microspheres. To investigate this relationship, three types of polyethylene microspheres with different diameters were used in simulations and experiments. These specimens were attached to polydimethylsiloxane and glass plates. A comparison revealed that the 50 μm diameter polyethylene spheres coated with carbon nanotubes had the highest ultrasound frequency. This work showed that smaller polyethylene microspheres generate higher ultrasound frequencies.

Mixed convection of single-walled carbon nanotubes in a triangular cavity containing a pentagonal impediment

Mixed convection of nanofluid (a homogeneous mixture of water and single-walled carbon nanotubes) is investigated numerically in a triangular cavity containing an adiabatic pentagonal obstacle close to the top surface. Analytical models are employed for effective thermophysical properties of nanofluid regarding carbon nanotubes and water. The top wall of the cavity is kept at a higher temperature, while the inclined sidewalls are kept at a lower temperature. A constant magnetic field of intensity B0 is introduced in the momentum equation. The effects of radiation and viscous heating on heat transfer are neglected. The impacts of Richardson number on the dimensionless velocity and temperature are presented graphically in terms of streamlines and isotherms. The Galerkin finite element method with a penalty function is employed to obtain the solution of dimensionless partial differential equations. The numerical results are examined for governing parameters, including volume fraction of carbon nanotubes, Richardson, and Hartmann numbers. It is concluded that the Nusselt number increases with increasing the governing parameters in the presence of an adiabatic pentagonal obstacle.

Conjugation with carbon nanotubes improves the performance of mesoporous silicon as Li-ion battery anode

Carbon nanotubes can be utilized in several ways to enhance the performance of silicon-based anodes. In the present work, thermally carbonized mesoporous silicon (TCPSi) microparticles and single-walled carbon nanotubes (CNTs) are conjugated to create a hybrid material that performs as the Li-ion battery anode better than the physical mixture of TCPSi and CNTs. It is found out that the way the conjugation is done has an essential role in the performance of the anode. The conjugation should be made between negatively charged TCPSi and positively charged CNTs. Based on the electrochemical experiments it is concluded that the positive charges, i.e., excess amine groups of the hybrid material interfere with the diffusion of the lithium cations and thus they should be removed from the anode. Through the saturation of the excess positive amine groups on the CNTs with succinic anhydride, the performance of the hybrid material is even further enhanced.

Layer-by-Layer Electrochemical Assembly of Pt/Phosphomolybdic Acid/Poly(diphenylamine)/PGE for Electrocatalytic Oxidation of Methanol

In this work, a layer-by-layer (LbL) electrochemical assembly was fabricated comprising alternating layers of poly(diphenylamine) (PDPA), phosphomolybdic acid (PMA) and Pt particles on a pencil graphite electrode (PGE) surface to prepare a modified electrode for effective oxidation of methanol. For this purpose, initially, the PGE surface was covered with a mixture of chitosan and multi-walled carbon nanotubes (MWCNTs); a layer of oxidized PDPA as a cationic layer was then deposited on the electrode surface by electropolymerization. Next, the anionic PMA was adsorbed on the cationic layer of PDPA via electrostatic forces. Finally, Pt particles were deposited on the electrode surface. This process was repeated several times to obtain multilayer film (Pt/PMA/PDPA)n on the chitosan-MWCNTs/PGE surface, where n is the number of triplet layers. The oxidation current of methanol was substantially increased with an increase to four layers. This study showed that the modified electrode, with good catalytic activity, can be applied as an anode material in direct methanol fuel cells.

3D N, S-co-doped carbon nanotubes/graphene/MnS ternary hybrid derived from Hummers' method for highly efficient oxygen reduction reaction

Designing and preparing oxygen reduction reaction (ORR) catalysts with low cost, high activity and strong stability play a crucial function in the application of fuel cells and metal-air batteries. In this work, we use pristine graphite and carbon nanotubes (CNT) mixture as initial carbon source, and for the first time successfully prepare N, S-co-doped carbon nanotubes/graphene/MnS ternary hybrid (NSCNT/NSG/MnS) by modified Hummers' method followed by a pyrolysis process. The morphology, structure, composition and ORR performance of the obtained sample are measured by scanning electron microscope, X-ray diffraction and lots of other techniques. The results show that the successful synthesis of NSCNT/NSG/MnS is achieved by the combination of effective exploitation of residual Mn and S species and strong reducibility of carbon under high temperature. Besides, we find that the resultant NSCNT/NSG/MnS can not only effectively stabilize and disperse MnS nanoparticles, but also possess large specific surface area, high N content and unique 3D architecture. Compared to other counterparts, the obtained 3D NSCNT/NSG/MnS exhibits superior ORR performance (the onset potential moves positively to 1.00 V; limiting-current density achieves 4.93 mA/cm2; ORR electron transfer number is close to four), which is proven to approach that of commercial Pt/C catalyst.

Unprecedentedly high selective adsorption of Xe/Kr mixtures in carbon nanotubes: A molecular simulation study

Abstract By using grand canonical Monte Carlo (GCMC) simulations, we investigated the adsorption of Xe/Kr mixtures with the mole fractions of Xe ranging from 10% to 90% in single-walled carbon nanotubes (CNTs) having diameters of 0.81 to 2.03 nm, at different temperatures. For the (mole ratio, 20/80) Xe/Kr mixture, the Xe/Kr selectivity decreases with diameter of the CNT at 298 K, while demonstrating a complex dependency on pressure in CNTs. Due to the single-file adsorbate configuration, the smaller (6, 6) CNT achieves a higher adsorption capacity than the (7, 7) CNT. At 1 bar and 298 K, the adsorption of Xe and the Xe/Kr selectivity achieve their maxima, 1.69 mol/kg and 36.3, in the (6, 6) CNT among the CNTs considered, and this optimized selectivity is much superior compared to a large number of metal-organic frameworks (MOFs). We find that increasing temperature generally reduces the adsorptions of Xe and Kr, with an exception that the co-adsorption of Kr is enhanced in the small CNTs for obtaining additional adsorption volume released by the reduced adsorption of Xe. While increasing temperature reduces the Xe/Kr selectivity in all the CNTs, the selectivity decreases with the bulk concentration of Xe in the (6, 6) and (7, 7) CNTs and remains almost independent of Xe concentration in the larger CNTs, at 1 bar. As revealed by the performance coefficient, the (6, 6) CNT holds the best performance on the adsorptive separation of Xe/Kr in all the cases considered in this work. Our findings reveal that the (6, 6) CNT has a great potential on preventing the uncontrolled emission of Kr while facilitating the commercial usage of Xe.

Lanthanum nickel oxide nano-perovskite decorated carbon nanotubes/poly(aniline) composite for effective electrochemical oxidation of urea

Here in, we introduce a modified glassy carbon (GC) electrode with two successive layers of conducting poly(aniline) (PANI) and lanthanum nickel oxide (LNO)-carbon nanotubes (CNT) mixture, (GC/PANI/LNO-CNT), for urea electrooxidation in alkaline medium. The use of La2NiO4 perovskite is advantageous with relatively low weight percentage of Ni (14.6%) compared to other Ni-based catalysts for electrooxidation of urea. The perovskite catalyst is synthesized using microwave-assisted method that reduces chemicals and energy consumption. Perovskite-based catalyst has good ionic and electronic conducting behavior, high oxygen mobility within its lattice with remarkable charge transfer rate. Carbon nanotubes increase the surface area of the electrode and act as a catalyst support to enhance the urea conversion process. Under optimized conditions, the specific current for urea electrooxidation is 1400 mA mg−1 cm−2. The perovskite catalyst and the (PANI/LNO-CNT) composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive analysis (SEM-EDAX). The composite is applicable in temperature range (10 °C to 50 °C), and at different urea concentrations (0.1 M to 1.0 M) in basic (KOH) electrolyte.

Enzymatic degradation of ginkgolic acid by laccase immobilized on novel electrospun nanofiber mat.

Ginkgo biloba leaf extract contains many active ingredients that are beneficial for health. However, ginkgolic acid, one of the major components found in G. biloba extract, may cause serious allergic and toxic side effects. The purpose of this study is to immobilize the laccase system on the electrospun nylon fiber mat (NFM) to hydrolyze the ginkgolic acid in G. biloba leaf extract efficiently. Novel electrospinning technology successfully produced high-quality nanoscopic fiber mats made of a mixture of multi-walled carbon nanotube and nylon 6,6. Laccase that was immobilized onto the NFM exhibited much higher efficiency in the catalyzation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) than nylon 6,6 pellets. After being immobilized onto the NFM, the pH and temperature stability of laccase were significantly improved. The NFM-immobilized laccase could maintain more than 50% of its original activity even after 40 days of storage or 10 operational cycles. The kinetic parameters, including rate constant (K), the time (τ50) in which 50% of ginkgolic acid hydrolysis was reached, the time (τcomplete) required to achieve complete ginkgolic acid hydrolysis, Km and Vmax were determined, and were 0.07 ± 0.01 min-1 , 8.97 ± 0.55 min, 45.45 ± 2.79 min, 0.51 ± 0.09 mM and 0.49 ± 0.03 mM min-1 mg-1 , respectively. The result successfully demonstrated the strong potential of using novel electrospun nanofiber mats as enzyme immobilization platforms, which could significantly enhance enzyme activity and stability. © 2020 Society of Chemical Industry.

Повышение микротвердости хромовых гальванических покрытий с использованием комбинации наноалмазов и нанотрубок

A method to increase the microhardness of the chromium galvanic coating by adding a mixture of carbon nanomaterials (nanodiamonds, single-walled and multi-walled nanotubes, graphene oxide) into a standard chromium galvanic coating electrolyte was proposed. The increase in the microhardness of the chromium galvanic coating was revealed and explained. This is due to a combination of two mechanisms: the introduction of nanodiamonds into the crystal lattice of the coating metal and the appearance of additional crystallization centers on defects in carbon nanotubes. The method of obtaining parts with a higher service life when using traditional chromium galvanic coating, as well as when using multi-walled carbon nanotubes, single-walled carbon nanotubes, nanodiamonds, and graphene oxide separately, was demonstrated. The best result was obtained using a mixture of nanodiamonds and multi-walled carbon nanotubes. The microhardness of the nanomodified chromium galvanic coating was measured, and it was found to increase by 27 %.

The role of carbon nanotubes (CNTs) and carbon particles in green enhanced oil recovery (GEOR) for Arabian crude oil in sandstone core

Green enhanced oil recovery (GEOR) is a chemical enhanced oil recovery (EOR) involving the injection of specific green chemicals (surfactants/alcohols/polymers) that effectively displace oil because of their phase-behaviour properties, which decrease the IFT between the displacing liquid and the oil. Carbon nanoparticles application in EOR has sparked interest in the last few years due to its unique characteristics. Carbon nanotubes (CNTs) are one of the common carbon nanomaterials with EOR potential, but they are not used with green surfactant to improve oil recovery. In addition, the recently developed Date Leaf Carbon Particle (DLCP) method has not been applied to GEOR and requires further study. The role of carbon particles in GEOR is not well understood and requires further investigation. This study was conducted to examine the effectiveness of DLCP and CNT in green surfactant alkyl polyglucoside (APG) for recovering residual oil within rock pores. The study consisted of a set of laboratory experiments. Two formulations of DLCP, CNT and green surfactant mixtures were selected for core-flood experiments based on interfacial tension measurements to examine their potential for EOR. In the first formulation, 0.08% DLCP was mixed with 0.5% APG and produced 45% of tertiary oil and 89% of oil initially in place (OIIP). This formulation produced a significant quantity of incremental oil after water flooding. Lastly, 0.5% APG was blended with 0.08% CNT; this produced about 27% tertiary oil and 77% OIIP.

Carbon Nanotubes and Graphene Radiant Heater Printed on a Cementitious Flooring Substrate: A Feasibility Study

The human activity of heating homes contributes a significant amount of CO2 in the total of the UK Green House Gases and the process of retrofitting residential stock and equipping new dwellings with lower and carbon neutral technologies could be complex, costly and physically challenging. This paper investigates the feasibility of a composite mixture of carbon nanotubes (CNT) and graphene material applied as a printed layer to the underside of a cementitious flooring substrate, acting as a radiant underfloor heater. Screening sample tests confirm instant radiant heating at low DC voltages with remarkably low conduction heat losses through the substrate.

Improvement in Tribological Properties of Plasma-Sprayed Alumina Coating upon Carbon Nanotube Reinforcement

Crushed alumina powder heterocoagulated with 1 or 2 wt.% carbon nanotube (CNT) was used to produce plasma-sprayed coatings with improved tribological properties. Heterocoagulation is a colloidal processing technique, and it was used to produce a homogenous mixture of CNT in alumina. These coatings were compared with a pristine alumina coating using a pin-on-disk setup under various speed–load conditions. A 6-mm-diameter WC–Co ball was used as counterbody. The wear resistance of the coatings increased in the following order: pristine alumina, alumina with 1 wt.% CNT, and alumina with 2 wt.% CNT. Wear progressed by low cycle fatigue, microfracture, and finally pulverization of the already dislodged wear debris on repeated rubbing by the counterbody. The higher wear resistance of the reinforced coatings is attributed to their higher hardness and fracture toughness. The pristine alumina coating was found to crumble owing to diffuse intergranular fracture beneath the surface during rubbing under higher speed and load. Upon crumbling, the pulverized debris assumed a paste-like form and was ejected at the top under the compressive action exerted by the counterbody at its leading edge. The high wear of the pristine alumina coating is attributed to this effect.

Equilibrium structures and flows of polar and nonpolar liquids and their mixtures in carbon nanotubes with rectangular cross sections

Molecular dynamics (MD) simulations of equilibrium structures and flows of polar water, nonpolar argon and methane, and mixtures of water and methane confined by single-walled carbon nanotubes (SWCNTs) with different rectangular cross sections have been performed. The results of these simulations show that equilibrium structures and flows of all confined liquids significantly depend not only on the shape of the SWCNT’s rectangular cross sections but also on the types of liquids inside SWCNTs. The cross sections of equilibrium structures of all confined liquids resemble replicas of cross sections of corresponding SWCNTs. In addition, the equilibrium structures formed by nonpolar argon atoms are most spatially ordered whereas nonpolar water molecules form the least spatially ordered equilibrium structures. It has been found that, for nonpolar methane flows through SWCNTs with rectangular cross sections, there are critical values fxc of the external driving force below which an average flow velocity is equal to nearly zero and above fxc methane molecules can flow. The critical value of the external driving force depends strongly on the shape of rectangular cross sections of SWCNTs under consideration. It has been also found that, for a sufficiently large value of the external driving force, the liquid argon flow through SWCNT with rectangular cross section with the ratio between its sides 1:4 demonstrates the ballistic frictionless regime.

Improved microhardness of chrome galvanic coatings with combining nanodiamonds and nanotubes

The method is developed for obtaining nanomodified galvanic coatings by adding a mixture of nanomaterials to the electrolyte. An experimental study of the microhardness of the precipitate of the technological process of obtaining nanomodified by a combination of nanodiamonds and multilayer carbon nanotubes; by a combination of single-layer carbon nanotubes and multilayer carbon nanotubes of chromium galvanic coating from a standard electrolyte was carried out. When nanodiamonds 12 g/l and multilayer carbon nanotubes “Taunit” 80 mg/l are added to the electrolyte, the microhardness of the chromium coating increases by 27% compared to the chromium coating obtained from the standard chromium plating electrolyte without additives. When single-layer carbon nanotubes 50 mg/l and multilayer carbon nanotubes “Taunit” 80 mg/l are added to the electrolyte, the microhardness of the chromium coating increases by 22% compared to the chromium coating obtained from the standard chromium plating electrolyte without additives. The service life of the parts, the chrome coating on which is obtained from the electrolyte with a mixture of nanodiamonds and multilayer carbon nanotubes “Taunit”, single-layer carbon nanotubes and multilayer carbon nanotubes is significantly higher than when using a traditional chrome coating, as well as using multilayer carbon nanotubes, single-layer carbon nanotubes or nanodiamonds separately.

Carbon nanotubes and carbon fibers in a flash: an easy and convenient preparation of carbon nanostructures using a conventional microwave

The growing interest in nanomaterials in different application fields calls for the implementation of simple, economically appealing, and efficient preparative methods. Among the wide variety of nanomaterials, carbon nanostructures have a special place due to their potential technological applications. Here, we present a fast, cheap, and easy-to-implement microwave-assisted method for the preparation of carbon nanotubes (CNTs) and carbon fibers (CFs) at room pressure conditions. The synthesis involves heating a mixture of graphite and ferrocene contained in a simple glass tube using a conventional microwave oven. A mixture of multi-walled carbon nanotubes (MWCNTs) and Fe3O4 magnetic nanoparticles were obtained quickly (less than 30 s) and in good yields. The products were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Raman spectroscopy.

CNT adalékolt kenőanyag viszkozitásának vizsgálata

Célunk olyan két komponensből álló kenőanyag vizsgálata, melyben a nanoméretű CNT szemcsék egyenletesen szétoszlatva (diszpergálva) vannak jelen a glicerin alapfolyadékban. A cikkben glicerin és szén nanocsövek különböző arányú keverékének viszkozitását elemezzük a hőmérséklettől és a fordulatszámtól függően. Megállapítottuk, hogy a glicerin nyírófeszültsége egyenesen arányos a deformációsebességgel. Ha a kenőanyag 1 m% CNT-t tartalmaz, akkor pszeudoplasztikus jelleget mutat; a nyírófeszültség-nyírási sebesség hatványtörvényszerinti összefüggésében a kitevő a hőmérséklet növelésével csökken.