Ratio Of Carbon Nanotubes Research Articles

Preparation of 3D carbon conductive composite derived from nitrogen-rich resin/MWCNT and its application in supercapacitors

Carbon materials are considered as one of the promising materials in supercapacitors because of their distinctive electrochemical properties. In this study, N-doped carbon electrode materials, derived from melamine formaldehyde (MF) resin, a high-performance and N-rich thermosetting resin, used as an electrode active material for supercapacitor application. A simple method was adopted to fabricate the three-dimensional conductive composite materials by mixing the carbon nanotubes (CNTs) to the carbon material with different mass ratios. It was found that the reactant ratio of MF and CNT plays an important role in the improvement of electrochemical behavior. The sample of 7% CNT@MF-C showed a gravimetric specific capacitance of 319.6 F g−1 in 6 M KOH aqueous electrolyte at a current density of 0.5 A g−1, as well as capacitance retention of 97.8% after 10,000 cycles. A remarkable improvement in the electrochemical behavior was obtained by modifying the surface chemistry as well as the electrical conductivity of the carbon. The assembled symmetrical supercapacitors have a high energy density and power density of 9.53 Wh kg−1 and 400 W kg−1, respectively. The presence of porous carbon with intrinsic nitrogen-containing groups makes them more useful as high-performance supercapacitors. Overall, this simple approach exhibits great potential for carbon-based high-performance supercapacitor application.

A numerical comparison among different water‐based hybrid nanofluids on their influences on natural convection heat transfer in a triangular solar collector for different tilt angles

AbstractNatural convection inside a triangular solar collector is investigated numerically for different nanofluids and hybrid nanofluids in this study. The individual effects of Al2O3–water, carbon nanotubes (CNT)–water, and Cu–water nanofluids are observed for different solid volume fractions of nanoparticles (0%–10%). Three types of hybrid nanofluids are prepared using different ratios of Al2O3, CNT, and Cu nanoparticles in water. A comparison is made varying the Rayleigh numbers within laminar range (103–106) for different tilt angles (0°, 30°, 60°, and 90°) of the solar collector. The inclined surface of the triangular solar collector is isothermally cold and the bottom wall (absorber plate) is isothermally hot, whereas the vertical wall with respect to the absorber plate is considered adiabatic. Average Nusselt numbers along the hot wall for different parameters are observed. Streamlines and isotherm contours are also plotted for different cases. Dimensionless governing Navier–Stokes and thermal energy conservation equations are solved by Galerkin weighted residual finite element method. Better convective heat transfer is found for higher Rayleigh number, solid volume fraction, and tilt angle. In the case of hybrid nanofluid, increasing the percentage of the nanoparticle that gives better heat transfer performance individually results in enhancing natural convection heat transfer inside the enclosure.

Computational analysis of the effects of carbon nanotubes on the bending, buckling, and vibration characteristics of carbon fabric/polymer hybrid nanocomposite plates

In this paper, the effects of adding carbon nanotubes (CNTs) on the bending, buckling and free vibration characteristics of carbon fabric/polymer hybrid nanocomposite plates (HNCPs) are investigated using a computational approach. First, a hierarchical finite element micromechanics approach is proposed to estimate the hybrid composite properties. The formation of interfacial region due to the non-bonded van der Waals interactions among the CNTs and polymer is considered. Then, finite element analysis is carried out to compute the mechanical responses of the CNT/carbon fabric hybrid composite structures. It is found that incorporating the CNTs into the carbon fabric-reinforced polymer materials results in an enhancement of buckling capacity and natural frequencies of the HNCPs. The maximum deflection of the traditional carbon fabric/polymer composite plates is decreased by adding the CNTs. A parametric study is accomplished to evaluate the influences of amount and aspect ratio of CNTs, material properties and thickness of interfacial region as well as the thickness and various shapes of plate on the flexural deformation, buckling and vibration characteristics of the HNCPs. The predictions are compared with those available in the literature to verify the validity of the presented computational model.

Tailoring of Thermo-Mechanical Properties of Hybrid Composite-Metal Bonded Joints.

Metallic substrates and polymer adhesive in composite-metal joints have a relatively large coefficient of thermal expansion (CTE) mismatch, which is a barrier in the growing market of electric vehicles and their battery structures. It is reported that adding carbon nanotubes (CNTs) to the adhesive reduces the CTE of the CNT-enhanced polymer adhesive multi-material system, and therefore when used in adhesively bonded joints it would, theoretically, result in low CTE mismatch in the joint system. The current article presents the influence of two specific mass ratios of CNTs on the CTE of the enhanced polymer. It was observed that the addition of 1.0 wt% and 2.68 wt% of multi-walled CNTs (MWCNTs) decreased the CTE of the polymer adhesive from °C (pristine level) to °C and °C, respectively, by 22% and 41% reductions.

Barium Titanate-reinforced Acrylonitrile-Butadiene Rubber: Synergy Effect of Carbon-based Secondary Filler

Acrylonitrile rubber (NBR) composites filled with barium titanate (BT) were prepared using an internal mixer and a two-roll mill. Also, a secondary filler, namely carbon nanotubes (CNT), was added in order to find a potential synergistic blend ratio of BT and CNT. The cure characteristics, tensile and dielectric properties (dielectric constant and dielectric loss) of the composites were determined. It was found that NBR/BT composites with CNT secondary filler, at a proper BT:CNT ratio, exhibited shorter scorch time (ts1) and cure time (tc90) together with superior tensile properties and reinforcement efficiency, relative to the one with only the primary filler. In addition, the NBR/BT-CNT composite with 80 phr BT and 1–2 phr CNT had dielectric constant of 100–500, dielectric loss of 12–100 and electrical conductivity below 10−4 S/m together with high thermal stability. Thus, with a proper BT:CNT mix and filler loading, we can produce mechanically superior rubber composites that are easy to process and low-cost, for flexible dielectric materials application.

Effect of Carbon Nanotubes (CNTs) aspect ratio on the rheology, thermal conductivity and mechanical performance of Portland cement paste

Abstract: Carbon nanotubes (CNTs) are potential candidates to enhance the heat balance of concrete, reducing internal stresses caused by differential heating in massive concrete elements. The higher the aspect ratio (AR) and content of CNTs, the greater the expected thermal conductivity (TC). However, high AR may impair the proper dispersion of CNTs in cementitious matrix, potentially harming the workability and mechanical strength of the composite. This work evaluated the effect of the AR (35, 250, 900, and 3500) and content (0.05% and 0.10%) of CNTs on the TC, rheology (squeeze flow), and mechanical strength of cement paste. Results showed that 0.05% CNT increased the TC of paste by up to 15% for AR of 250, but further increasing AR progressively reduced the TC of the composite. In turn, 0.10% CNT incorporation did not result in significant TC gains. The yield stress and viscosity of the mixes progressively increased as CNTs content and AR increased, by up to 119% compared with plain cement paste. No significant differences were observed in 28-day compressive strength with 0.05% CNT incorporation, while 0.10% CNT led to slight strength reductions for some mixes. Regarding flexural strength, 0.05% incorporation of either CNT decreased the strength of the mixes while 0.10% incorporation generally compensated this reduction, except for the lowest aspect ratio. Overall, CNTs with intermediate AR (around 250) was effective in improving the thermal conductivity of cement paste, increasing it by 15% with relatively low content (0.05%) while did not significantly impair the fresh and mechanical performance of the composite.

Study on Plastic Strengthening Mechanisms of Aluminum Matrix Nano-Composites Reinforced by Nickel Coated CNTs

ABSTRACT The mechanical strength of pure aluminum matrix can be greatly enhanced by adding a small amount of nickel-coated carbon nanotubes (NiCNTs), where the nickel coating helps to the uniform dispersion of carbon nanotubes (CNTs) within the aluminum matrix through decreasing density difference and avoiding CNTs agglomeration. The yield strength of pure aluminum can be increased by 33.3% with 1% weight fraction of NiCNTs. This strengthening effect is caused by three mechanisms: Orowan looping, load bearing, and thermal expansion mismatch which are studied by both finite-element method and analytical method. A series of finite-element analyses using a representative volume element (RVE) method are conducted considering influences of CNTs aspect ratios, volume fraction of hardened zone, and the hardened plastic strain of hardened zone. The results show that the aspect ratio of CNTs is very important in the strengthening of CNT-reinforced composites, and the yield stress increases with increasing aspect ratio. A set of parameters for analytical solutions are optimized that can well describe and accurately predict the experimental data. Both the finite-element analysis and analytical solution are well correlated with the experimental results for Al/NiCNT composites with different weight fractions of CNTs.

Modeling of the Interfacial Stress Transfer Parameter for Polymer/Carbon Nanotube Nanocomposites

The main aim of this paper is to define the interfacial stress transfer parameter s in the Callister model using the Pukanszky model. The parameter s is expressed by the polymer strength, carbon nanotube (CNT) size, and interfacial shear strength. The developed equation is applied to plot the roles of all parameters in the value of s. The reasonable outputs of the developed equation show its accuracy for the CNT nanocomposites. The interfacial shear strength directly handles the parameter s, but the matrix strength has no effect. Thin and long CNT increase the value of s, but thick and short CNT deteriorate it. However, the negligible variation of s within different ranges of CNT dimensions indicates that the CNT size slightly affects the value of s. The parameter B in the Pukanszky model directly handles the parameter s, which is logical because both B and s show the interfacial/interphase properties. In addition, although the aspect ratio of CNT determines the surface area of nanoparticles, it insignificantly manipulates the parameter s.

Strengthening of the magnesium matrix composites hybrid reinforced by chemically oxidized carbon nanotubes and in situ Mg2Sip

Aggregation and weak interfacial bonding limit the superior strengthening potential of the carbon nanotubes (CNTs) in the metal matrix composites. To overcome these challenges, in situ Mg2Si nanoparticles (Mg2Sip) have been hybridized with surface modified CNTs through chemical oxidization. The synergistic strengthening was enhanced by tailoring the volume ratios of CNTs to Mg2Sip in the Mg matrix through powder thixoforming technology. Herein, when 0.3CNTs-1.2Mg2Sip was added, a yield strength, ultimate tensile strength, and elongation of 213 MPa, 271 MPa, and 6.3%, respectively, were obtained, which were 18.3%, 16.8%, and 3.3% higher than those of the 0.75CNTs-0.75Mg2Sip/Mg composites, respectively. The strengthening effects of the CNTs-Mg2Sip reinforcements were more effective than those of the individual 1.5CNTs and 1.5Mg2Sip owing to the effective thermal mismatch and load transfer strengthening mechanisms. In this study, we propose an effective approach to harness the superior performances of the hybrid reinforcements for enhancing the composites.

Gamma irradiation influence on mechanical, thermal and conductivity properties of hybrid carbon nanotubes/montmorillonite nanocomposites

A thermoplastic elastomer (TPE) based nanocomposite with the same weight ratio of hybrid nanofillers composed of carbon nanotubes (CNTs) and montmorillonite nanoclay (DK4) was prepared using a melt blending technique with an internal mixer. The TPE composite was blended from polylactic acid (PLA), liquid natural rubber (LNR) as a compatibilizer and natural rubber (NR) in a volume ratio of 70:10:20, respectively. The weight ratio of CNTs and DK4 was 2.5 wt%. The prepared samples were exposed to gamma radiation at range of 0–250 kGy. After exposure to gamma radiation, the mechanical, thermo-mechanical, thermal and electrical conductivity properties of the composites were significantly higher than unirradiated TPE composites as the irradiation doses increased up to 150 kGy. Transmission electron microscopy (TEM) micrographs revealed the good distribution and interaction between the nano-fillers and the matrix in the prepared TPE hybrid nanocomposites. In summary, the findings from this work definite that gamma irradiation might be a viable treatment to improve the properties of TPE nanocomposite for electronic packaging applications.

Percolation Conduction of Carbon Nanocomposites.

Carbon nanocomposites present a new class of nanomaterials in which conducting carbon nanoparticles are a small additive to a non-conducting matrix. A typical example of such composites is a polymer matrix doped with carbon nanotubes (CNT). Due to a high aspect ratio of CNTs, inserting rather low quantity of nanotubes (on the level of 0.01%) results in the percolation transition, which causes the enhancement in the conductivity of the material by 10–12 orders of magnitude. Another type of nanocarbon composite is a film produced as a result of reduction of graphene oxide (GO). Such a film is consisted of GO fragments whose conductivity is determined by the degree of reduction. A distinctive peculiarity of both types of nanocomposites relates to the dependence of the conductivity of those materials on the applied voltage. Such a behavior is caused by a non-ideal contact between neighboring carbon nanoparticles incorporated into the composite. The resistance of such a contact depends sharply on the electrical field strength and therefore on the distance between neighboring nanoparticles. Experiments demonstrating non-linear, non-Ohmic behavior of both above-mentioned types of carbon nanocomposites are considered in the present article. There has been a model description presented of such a behavior based on the quasi-classical approach to the problem of electron tunneling through the barrier formed by the electric field. The calculation results correspond qualitatively to the available experimental data.

The Effect of Carbon Nanotubes on the Flowability, Mechanical, Microstructural and Durability Properties of Cementitious Composite: An Overview

Excellent mechanical properties and chemical stability make carbon nanotubes (CNTs) some of the most promising nanomaterials that can be used in cementitious composites to improve their performance. However, the difficulty of CNTs’ dispersion within the cementitious structure still exists and thus prevents the homogeneous distribution of CNTs. The homogeneous distribution of CNTs within a composite structure plays an essential role that can have a positive effect on the mechanical performance of CNT-cement composites. This paper introduces the methods for the production of CNTs and provides useful information about the influence of CNTs on the flowability, mechanical performance, microstructural changes and hydration of cement composites. The influences of water-cement ratio, used surfactants and various doses of CNTs on the properties of cementitious composites were also studied.

Facile Fabrication of Nickel Aluminum Layered Double Hydroxide/Carbon Nanotube Electrodes Toward High-Performance Supercapacitors.

The electrode, as one of the key components in supercapacitors, has a pivotal effect on the overall performances. In this work, a series of composite electrode materials are proposed via the combination of nickel aluminum layered double hydroxides (NiAl-LDHs) and carbon nanotubes (CNTs). To begin with, materials with different ratios of the two compositions are fabricated with a coprecipitation method. After that, various characterization methods indicate that the NiAl-LDH/CNT composites exhibit an irregular thin platelet structure with a well-constructed conductive network inside. Furthermore, the effect of the CNT ratio on the electrochemical property is subsequently investigated, which proves that the conductive network of CNTs is beneficial for the transport of the electrons and strengthens the platelet structure. The results show that when the amount of CNTs reaches 1.5 wt %, it can yield a high specific capacitance of 2447 F g–1 at 2 A g–1, with a good cycling stability of 90.1% after 2500 cycles, indicating high application potential in positive electrodes of pseudocapacitors. The synergistic effects of NiAl-LDHs and CNTs are thought to be the main reasons for the good properties of NiAl-LDHs/CNTs composites.

Study of Dispersions of Carbon Nanotubes Modified by the Method of Rapid Expansion of Supercritical Suspensions.

The effectiveness of carbon nanotubes (CNT) deagglomeration by rapid expansion of supercritical suspensions (RESS) in nitrogen and carbon dioxide fluids was studied in this work. Two different mechanisms of deagglomeration were proposed for these two fluids at various temperature and pressure conditions. Ultrasound attenuation spectroscopy was applied as an express method of determining median diameter and aspect ratio of CNTs. At least twofold reduction of the diameter was shown for CNT bundles processed by RESS technique. Aspect ratio of processed CNTs, calculated from acoustic attenuation spectra, increased to 340. These results were in a good agreement with atomic force microscopy data.

The synergic influence of carbon nanotube and nanosilica on the compressive strength of lightweight concrete

Nanomaterials, owing to their extraordinary properties are known to improve the performance of concrete, are widely used in cementitious materials. Many studies have been conducted so far to understand the effects of inclusion of nanomaterials on the concrete while less studies have been conducted on Light Wight Concrete (LWC) especially on the synergic effect of nanomaterials.The influence of carbon nanotubes (CNT) and nanosilica (NS) as reinforcement fillers to increase the compressive strength of lightweight concrete using expanded clay were investigated in this study. Eight batches of samples were made by mixing CNT and NS using ultrasonication technique into the concrete mix, with one being a control system without nano reinforcement fillers to be used as a reference batch. The optimum substitution percentage of 3% for nano reinforcements was incorporated into the concrete by varying the ratio of CNT and NS. The compressive strength tests were conducted according to BS EN 12390: 2000 and BS EN 12350: 2009. From the results, it was found that incorporating 1% NS and 2% CNT, the highest compressive strength of 10.72 MPa can be achieved at 28 days, with percentage of 39% as compared to control sample. However, the incorporation of 3% CNT resulted in a negative effect on the compressive strength gain by a significant drop in compressive strength of −16% at 28 days. Field emission scanning electron microscope (FESEM) test was conducted to further observe the compressive strength behaviour for the obtained results.

Catalytic Preparation of Carbon Nanotubes from Waste Polyethylene Using FeNi Bimetallic Nanocatalyst.

In this work, carbon nanotubes (CNTs) were synthesized by catalytic pyrolysis from waste polyethylene in Ar using an in-situ catalyst derived from ferric nitrate and nickel nitrate precursors. The influence factors (such as temperature, catalyst content and Fe/Ni molar ratio) on the formation of CNTs were investigated. The results showed that with the temperature increasing from 773 to 1073 K, the carbon yield gradually increased whereas the aspect (length-diameter) ratio of CNTs initially increased and then decreased. The optimal growth temperature of CNTs was 973 K. With increasing the Fe/Ni molar ratio in an FeNi bimetallic catalyst, the yield of CNTs gradually increased, whereas their aspect ratio first increased and then decreased. The optimal usage of the catalyst precursor (Fe/Ni molar ratio was 5:5) was 0.50 wt% with respect to the mass of polyethylene. In this case, the yield of CNTs reached as high as 20 wt%, and their diameter and length were respectively 20–30 nm, and a few tens of micrometers. The simple low-cost method developed in this work could be used to address the environmental concerns about plastic waste, and synthesize high value-added CNTs for a range of future applications.

Nonlinear Conductive Characteristics of ZnO-Coated Graphene Nanoplatelets-Carbon Nanotubes/Epoxy Resin Composites.

With the increasing threats arising from the electromagnetic environment, polymeric composites which could exhibit nonlinear conductive characteristics are highly required in the protection of electronic devices against overvoltage. In this research, ZnO nanoparticles are coated onto graphene nanoplatelets (GNPs)-carbon nanotubes (CNTs) hybrid, and then it is embedded in epoxy resin (ER) matrix via solution blending. Based on the characterization results, CNTs are well dispersed across the GNPs which prevent the restacking of GNPs and CNTs. At the same time, ZnO nanoparticles are well-bonded to the surfaces of GNPs-CNTs hybrid. During repeated conductive characteristic measurements, GNPs-CNTs-ZnO/ER composite is able to demonstrate distinctly reversible nonlinear conductive behavior, with high nonlinear coefficients. Especially, the filler content in GNPs-CNTs-ZnO/ER composite is only 12.5% of that in GNPs-ZnO/ER composite reported in our previous work. Moreover, it is shown that the nonlinear coefficients and switching threshold voltage can be modified by controlling the weight ratios of GNPs, CNTs, and ZnO. Finally, the samples with 1:1 weight ratio of GO to MWCNTs (A-6.67 and A-10) exhibit the best reversible nonlinear conductive behavior.

Unique sliding properties of bucky paper and a simple method to control the sliding angle

In this study, an easy and widely applicable method to control the sliding angle of bucky paper (BP), which is a paper-like membrane consisting of carbon nanotubes (CNTs), while maintaining the hydrophobic properties was developed. We prepared BPs using various types of CNTs, and the contact angle insignificantly differs regardless of the type of CNT, but the sliding angle shows a notable difference. The sliding angle of the BP (2°–3°) indicates an excellent water sliding ability for short CNTs, whereas the water droplet on the BP with long CNTs did not slip-down, not even at 90°. By utilizing this feature for hybrid long and short CNTs, the sliding angle can be controlled from 2° to 90° using the CNT ratio.

Free arc liquid-phase dispersion method for the preparation of carbon nanotube dispersion

In this study, a new method of rapid preparation of carbon nanotube (CNT) solution with highly dispersed morphology by free arc excitation is proposed, which shortens the time of the preparation of CNT solution with low concentration. The principle is that the high-energy flow density heat generated by the free arc makes the vaporizable substance coated on the surface of CNTs vaporize rapidly, and then generates the bulk increasing motion, which makes the CNTs aggregates dispersed, and finally forms the CNTs gas-phase dispersion monomer with high dispersion or the cross-linking morphology of few CNTs. In this paper, the influence of gum Arabic (GA) and deionized water (DI water) contents in CNTs mixed electrode on the dispersion of CNTs in different environments (gas phase and liquid phase) is explored. In the limited case of this work, the dispersion effect is better when the mass ratio of CNTs, GA and DI water is 1:0.04:3.96 in the liquid-phase environment. The preparation method reported in this work is expected to be a rapid way to obtain low-concentration nanodispersion.

Optimization and aging of Pt nanowires supported on single-walled carbon nanotubes as a cathode catalyst in polymer electrolyte membrane water electrolyser

A catalyst material containing platinum nanowires supported on single-walled carbon nanotubes (CNTs) is tested thoroughly for the use as a cathode catalyst for polymer electrolyte membrane water electrolyser (PEMEL). The Nafion ionomer content, the platinum to CNT ratio and the thickness of the catalyst layer (CL) is optimized. Long-term measurement with constant current and start-stop cycling of the optimized CL is performed in order to study the durability of the catalyst material. The CLs are characterized ex-situ with TEM, XRD and Raman spectroscopy. During the constant current operation, platinum experiences Ostwald ripening type of degradation and during the cycling, particle agglomeration. The magnitude of platinum degradation is, however, lower than for a commercial Pt/C type of catalyst. Moreover, the CNTs are subjected to carbon corrosion, but the rate of corrosion is observed to be decreasing. Therefore, carbon nanotubes are considered more suitable support material for the cathode catalyst of PEMELs.