Carbon Nanotubes Volume Research Articles

Effect of nonlinear FG-CNT distribution on mechanical properties of functionally graded nano-composite beam

This work focused on the novel numerical tool for the bending responses of carbon nanotube reinforced composites (CNTRC) beams. The higher order shear deformation beam theory (HSDT) is used to determine strain-displacement relationships. A new exponential function was introduced into the carbon nanotube (CNT) volume fraction equation to show the effect of the CNT distribution on the CNTRC beams through displacements and stresses. To determine the mechanical properties of CNTRCs, the rule of the mixture was employed by assuming that the single-walled carbon nanotubes (SWCNTs)are aligned and distributed in the matrix. The governing equations were derived by Hamilton's principle, and the mathematical models presented in this work are numerically provided to verify the accuracy of the present theory. The effects of aspect ratio (l/d), CNT volume fraction (Vcnt), and the order of exponent (n) on the displacement and stresses are presented and discussed in detail. Based on the analytical results. It turns out that the increase of the exponent degree (n) makes the X-beam stiffer and the exponential CNTs distribution plays an indispensable role to improve the mechanical properties of the CNTRC beams.

Micromechanical technique based prediction of effective properties for hybrid smart nanocomposites

The domain of carbon nanotube (CNT) reinforced composites is a colossal and convoluted area of research. The modeling of composite materials under deformation plays a vital role in structural design. A new model that comprises CNT and piezoelectric fibers reinforced in a hybrid smart composite has been proposed, and its effective properties are determined. The resulting composite can be regarded as a cylindrical composite with continuous parallel PZT fiber embedded inside the CNT-reinforced hybrid nanocomposite. The strength of a material based on the micromechanics technique is used to evaluate the proposed hybrid smart nanocomposite's effective elastic and piezoelectric properties. The results illustrate that the introduction of CNTs as reinforcing fibers in the proposed composites has significantly improved the effective elastic and piezoelectric properties. The effects of CNT content and volume fractions were investigated in a hybrid smart nanocomposite.

AC CONDUCTIVITY AND DIELECTRIC STUDY OF THE POLYESTER REINFORCED BY AL/CNT:ZN/AL NANOCOMPOSITE

In this study, composites of carbon nanotubes and zinc matrix have been fabricated by a powder metallurgy method. Firstly, CNT and Zn powders with sizes in the range of (4.5-6.7) nm, respectivel are dispersed at various weight contents (in the range of (2.0% -.1.0 %) in polyester polymer as solvent to get (polyester /CNT-Zn) Nano composite of about 2 mm thickness. The effects of different multi-walled carbon nanotubes (CNTs) contents on the ac conductivity and dielectric properties of the composites were investigated. Ac conductivity measurements of multi-walled carbon nanotubes (CNTs) reinforced polyester have been evaluated. AC conductivity was examined in the frequency range from (100-400k) Hz at ambient temperature.An enhancement of Ac-conductivity, in accordance to percolation theory, was evidenced increasing the weight content of the conductive Nano-filler .The experimental results indicate that the frequency dependent behavior of CNT-Zn /polyester Nano composite can be modeled by R-C circuit, permittivity of material increase with increasing of CNT content. .Also, the results showed that the addition to the zinc matrix of 1% by volume of carbon nanotubes caused increases in the ac conductivity .

Preparation and evaluation of a stable CNT-water based nano cutting fluid for machining hard-to-cut material

Machining hardened steels is always difficult because of its excessive heat generation. That is why, the application of cutting fluid in machining hardened steel is noted for eliminating defects triggered by the high cutting temperature. In this respect, the aim of this paper is to present a stable high volume carbon nanotube based nanofluid which will act as an efficient cutting fluid and perform better than conventional cutting fluid. To fulfill this purpose, the samples with different volumes of Carbon nanotubes were made and their stability was analyzed. Both the sedimentation and zeta potential analysis proved that the sample made with less than 0.4% volume CNTs shows higher stability. Conventional cutting fluid was made with oil mixed in water and compared its properties to all nano fluid samples. All the nano fluid samples showed higher thermal conductivity and lower viscosity than conventional cutting fluid. Furthermore, a milling operation on 42CrMo4 hardened steel material was performed without any fluid, with conventional (Aquatex 3180 oil based cutting fluid) and with nano fluid. Nano fluid was delivered internally to the cutting zone by using a specially designed liquid applicator. Maximum 29% reduction in cutting temperature, 34% reduction in surface roughness, 33% reduction in cutting force and 39% reduction in tool wear was obtained by using the 0.3 vol% nanofluid sample. So, it can be concluded that the 0.3% volume carbon nanotubes based cutting fluid is an appropriate choice to be used in machining hardened materials.

Hybrid effects of steel fiber and carbon nanotube on self-sensing capability of ultra-high-performance concrete

This study aims to examine the feasibility of using steel fibers and carbon nanotubes (CNTs) on developing self-sensing ultra-high-performance concrete (UHPC). For this, four steel fiber types with two different shapes (straight vs. twisted) and three different aspect ratios from 65 to 100 were considered at a fiber volume fraction of 2%. 0.5% by volume of CNTs were simultaneously added. A plain UHPC with only 0.5% CNTs was also fabricated and tested as a control specimen. Test results indicated that the addition of 2% steel fibers was effective in enhancing compressive strength, elastic modulus, tensile strength, and strain capacity of the plain UHPC. The compressive behaviors of UHPC and ultra-high-performance fiber-reinforced concrete (UHPFRC) with CNTs were not predicted based on a fractional change in resistance (FCR) measurement, whereas the total tensile behaviors in terms of both stress-strain and stress-crack opening displacement (COD) curves were quite well simulated based on the FCR measurement and curve-fitting equations suggested. The unintended noise in the FCR of the plain UHPC was largely mitigated by adding the steel fibers, while the highest gauge factor (GF) under tensile load was found for the plain UHPC with CNTs. Using micro steel fibers was more effective in increasing the GF than using macro steel fibers, and better predictive results were obtained for the UHPFRC with straight steel fibers as compared to that with twisted steel fibers.

Frequency analysis of sandwich beam with FG carbon nanotubes face sheets and flexible core using high-order element

ABSTRACTIn the present paper, the vibrational behavior of sandwich beam with a flexible core and anti-symmetric functionally graded carbon nanotubes face sheet is investigated. Carbon nanotubes are considered as functional graded materials in the thickness of the faces and their properties change along the thickness of the face sheets. For the modeling of sandwich beam behavior, the Euler–Bernoulli theory is used for face sheets and the semi-3D elasticity is used for the core, which allowed us to investigate the flexibility of the core. Differential equations of motions are derived using the virtual displacement principle. In this research, a high-order element is presented for solving equations of motion, and then by using this element, the finite element formulation has been extracted and solved. Numerical results are obtained for various boundary conditions, which include simply support, clamped, free-clamped, and simply support-clamped. Also, different volumes of carbon nanotubes have been investigated for different distributions. The results showed that the distribution of the FG-X pattern carbon nanotube leads to the highest natural frequency of the beam. The main conclusion of this research is that, in most cases the FG-O pattern has the lowest natural frequencies and in some cases the FG-Λ pattern has the lowest natural frequencies. In other words, generally, it can be say that the lowest natural frequencies of the sandwich beam with functionally graded carbon nanotubes faces depend on the boundary conditions, thickness ratio, and also the volume fraction of carbon nanotubes. In this paper also the effect of geometric angles of the beam, such as the thickness of the core and face sheet thickness on natural frequency of the system is also investigated.

Multi-scale Simulation of Double-Walled Carbon Nanotube-Reinforced Composites

In this study, a finite element approach is applied to predict the Young’s modulus of a nanocomposite. To do this, a representative volume element was simulated using ANSYS Commercial Software and contained three different phases namely, resin, carbon nanotube and interphase region. The carbon nanotube type considered here was double-walled carbon nanotube and was simulated at molecular scale, while the matrix was simulated at macro-scale which means a multi-scale modeling was applied here. Furthermore, the coupling between the carbon nanotube and matrix was created using linear spring elements. It is worth mentioning that according to Lennard-Jones potential, the van der Walls forces no longer exist at a distance more than 0.85 nm and for this reason the spring bonds were only created at this distance. After simulation of the model, the Young’s modulus of the representative volume element was computed and the results were presented afterwards. Some parametric studies including the effect of double-walled carbon nanotube type, volume fraction and stiffness of the interphase region will also be investigated.

Impact of carbon nanotube geometrical volume on nonlinear absorption and scattering properties

Nonlinear optical (NLO) properties of carbon nanostructures are of great interest due to their broadband spectral response. As carbon nanotubes (CNTs) can be synthesized with various lengths, thicknesses, and numbers of layers, their optical properties can also be different. We have performed side-by-side comparative studies of the relationship between the geometrical volume and NLO properties of CNTs. The real and imaginary components of the third order optical nonlinearity are obtained using well-known Z-scan technique. While the transmission and scattered light are detected using photodiodes, the generated photoacoustic signal is recorded simultaneously using an ultrasonic transducer. Results show an inverse relationship between the volume of CNTs and their NLO properties. This can be attributed to the availability of more nanoparticles within the laser beam profile and concurrent generation of scattering sites upon the absorption of incident radiation.

Properties of CNTs/MoSi2 composites prepared by spark plasma sintering

Molybdenum disilicide (MoSi2) based composites with various contents of carbon nanotubes (CNTs) were fabricated by spark plasma sintering (SPS) in vacuum under a pressure of 25 MPa. The composites obtained under a sintering temperature of 1500 °C and time of 10 min exhibited optimum mechanical properties at room temperature in terms of fracture toughness and transverse rupture strength. MoSi2 based composite with 6.0% CNTs (volume fraction) had the highest fracture toughness, transverse rupture strength and hardness, which were improved by about 25.7%, 51.5% and 24.4% respectively, as compared with pure MoSi2. A Mo4.8Si3C0.6 phase was detected in CNTs/MoSi2 composites by both X-ray diffraction (XRD) method and microstructure analysis with scanning electron microscopy (SEM). It is believed that the fine grains and well dispersed small Mo4.8Si3C0.6 particles had led to a higher hardness and strength of CNTs/MoSi2 composites because of their particle pullout, crack deflection and micro-bridging effects.

Parametric numerical simulation of impact response of carbon nanotube/polymer nanocomposites

A numerical model has been developed using the explicit FE code LS-DYNA in order to study the effect of geometrical and material parameters on the low-velocity impact response of carbon nanotube (CNT)/polymer nanocomposites. The model is based on a Representative Volume Element (RVE). The RVE is prismatic with a rectangular cross-section while the impactor is spherical. The simulations show that the presence of CNT significantly enhances the impact stiffness and the energy absorption capacity of the material. The enhancement increases with the CNT's volume fraction and it is larger at larger impact velocities. The effect of CNT's aspect ratio is found to be minor. The orthotropic behaviour of CNT assigns the RVE a higher energy absorption capacity than the isotropic behaviour at small impact velocities. The prediction of impact damage at large impact velocities indicates that the CNT makes the polymer more susceptible to fracture.

Iron Oxide-Carbon Nanotube Composite for NH3 Detection

Fabrication of iron oxide/carbon nanotube composite structures for detection of ammonia gas at room temperature is reported. The iron oxide/carbon nanotube composite structures are fabricated by in situ co-arc-discharge method using a graphite source with varying numbers of iron wires inserted. The composite structures reveal higher response signals at room temperature than at high temperatures. As the number of iron wires inserted increased, the volume of carbon nanotubes and iron nanoparticles produced increased. The oxidation condition of the composite structures varied the carbon nanotube/iron oxide ratio in the structure and, consequently, the resistance of the structures and, finally, the ammonia gas sensing performance. The highest sensor performance was realized with oxidation heat-treatment condition, in which most of the carbon nanotubes were removed from the composite and iron oxide played the main role of ammonia sensing. The response signal level was 62% at room temperature. We also found that UV irradiation enhances the sensing response with reduced recovery time.

Molecular dynamics simulation of functionalized SWCNT–polymer composites

The analysis of the influence of functionalization on the mechanical properties of the carbon nanotubes (CNTs) has been poorly addressed, especially when compared with the extensive amount of work on pristine CNTs. This article analyzes the effect of carboxylic (COOH), ester (COOCH3), silane (COSiCH3), and vinyl (CH = CH2) groups attached on the surface of single-walled carbon nanotube (SWCNT) on elastic properties of polypropylene (PP) composites reinforced with functionalized SWCNTs along the axial direction of the CNTs by using MD approach. Effect of CNT aspect ratio and volume fraction on the elastic moduli has also been studied. The results show that although chemical functionalization of SWCNTs has been considered as a means to increase the load-transfer efficiency in a nanotube–polymer composite, this functionalization has, in fact, degraded most of the macroscopic elastic stiffness components of the composite materials considered in this study. The decrease in longitudinal modulus of functionalize...

Fabrication of ferrocene functionalised ionic liquid/carbon nanotube nanocomposite modified carbon-ceramic electrode: application to the determination of hydrazine

ABSTRACTA novel ionic liquid, 1-(ferrocenyl butyl)-3-methylimidazolium tetrafluoroborate (Fc-IL), was synthesised. The nanocomposite of Fc-IL and multi-walled carbon nanotubes (MWCNTs) was constructed and used for surface modification of carbon-ceramic electrode. The modified electrode was applied to the determination of hydrazine. Operational parameters such as pH of the solution, ionic liquid volume and amount of carbon nanotubes, which affect the analytical performance of the modified electrode, were optimised. The linear range of the modified electrode toward hydrazine concentration was 0.96–106.10 μg L–1 with a detection limit of 0.64 μg L–1 (S/N = 3). The modified electrode displayed high repeatability, reproducibility, long-term life time and low response time (<3 s). The applicability of this method was further tested by analysing the hydrazine content in boiler-feed water samples containing different concentrations of hydrazine and the results were in good agreement with the spectrophotometry method.

Electrical conduction mechanism of volume and surface resistivities of multi-walled carbon nanotubes doped polyvinyl alcohol (PVA) and the pyroelectric behavior of polyvinylidene difluoride (PVDF) thin films

Electrical conduction mechanism of volume and surface resistivities of multi-walled carbon nanotubes doped polyvinyl alcohol (PVA) and the pyroelectric behavior of polyvinylidene difluoride (PVDF) thin films

Molecular Dynamics Simulation of Noble Gases Adsorption on Carbon Nanotube Bundles

To study the possible application of nanotubes as gas storage materials, noble gases adsorption on carbon nanotube bundles has been studied using the molecular dynamics simulation. Adsorption isotherms of Ar, Kr, and Xe on bundles of (10,10) single walled carbon nanotubes have been investigated at various pressures and temperatures. The results indicate that adsorption occur both internal pore volume and external surface of the open-ended carbon nanotubes. It is found that endohedral and exohedral adsorption coverages depend on temperature. We have also calculated isosteric heat of adsorption, binding energy, and isometric heat capacity. The values of these quantities indicate that carbon nanotube bundles can be used as materials for storage of noble gases.

Electrical and Piezoelectric Behavior of Polyamide/PZT/CNT Multifunctional Nanocomposites

ABSTRACTThree‐phase polyamide 11 (PA 11)/lead zirconate titanate (PZT)/carbon nanotubes (CNT) composites are elaborated by extrusion. The influence of inorganic particles on the electrical properties of conductive composites and the influence of conductive particles on the ferroelectric properties of organic/inorganic composites are both studied. Inorganic particles do not modify the establishment of the electrical percolation path of CNTs either regarding the percolation threshold value or the conductivity reached above this insulator–conductive transition. The dielectric permittivity of two‐phase PA 11/PZT composites is improved with the addition of only 0.2% in volume of CNTs. This three‐phase composite could be proposed for actuation, energy harvesting and damping performances enhancement.

Effective mechanical properties of nanocomposites reinforced with wavy carbon nanotubes

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable reinforcements for composite materials. Nanotube efficiency in reinforcing the matrix depends on the CNT alignment, volume fraction and configuration, as well as matrix properties. In this investigation, finite element method (FEM) is used to investigate the effects of nanotube waviness ratio, volume fraction, and matrix modulus on properties of CNT based polymer nanocomposites. Nanocomposite mechanical properties are evaluated using a 3D nanoscale representative volume element. Models consisting of CNTs with different waviness ratios are created to investigate the effects of nanotube configuration on nanocomposite mechanical properties. Next, the effect of nanotube volume fraction on nanocomposite moduli of elasticity is investigated. Finally, the effects of matrix modulus are investigated by analysing models consisting of matrices with different moduli. The results of this investigation are compared with those found in the literature and good agreement is observed.

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF CNT/Al COMPOSITES FABRICATED BY HIGH ENERGY BALL--MILLING METHOD

The mixture powders of carbon nanotubes (CNTs) and aluminum were high-energy ball-milled, and then the CNT/Al composites with different CNT contents were fabricated using a power metallurgy method. Microstructure examinations show that a certain volume of CNTs can be uniformly dispersed in the Al matrix by ball-milling and the CNTs have a close bonding with the Al matrix. By using an appropriate ball-milling process flow, the CNTs suffer no serious damage. Tensile tests indicate that the composite reinforced by 1.5% (volume fraction) CNTs exhibits the best mechanical performance, and the yield strength is improved by 53.6% compared with the Al matrix. When the CNT volume fraction reaches 3%, lots of clusters are formed in the composite, and therefore the tensile properties are significantly reduced. Both grain refinement and load transfer are proved to be the strengthening mechanisms of the CNT/Al composites.

Free Vibration Analysis of Nanocomposite Plates Reinforced by Graded Carbon Nanotubes Based on First-Order Shear Deformation Plate Theory

AbstractBased on the Mindlin’s first-order shear deformation plate theory this paper focuses on the free vibration behavior of functionally graded nanocomposite plates reinforced by aligned and straight single-walled carbon nanotubes (SWCNTs). The material properties of simply supported functionally graded carbon nanotube-reinforced (FGCNTR) plates are assumed to be graded in the thickness direction. The effective material properties at a point are estimated by either the Eshelby-Mori-Tanaka approach or the extended rule of mixture. Two types of symmetric carbon nanotubes (CNTs) volume fraction profiles are presented in this paper. The equations of motion and related boundary conditions are derived using the Hamilton’s principle. A semi-analytical solution composed of generalized differential quadrature (GDQ) method, as an efficient and accurate numerical method, and series solution is adopted to solve the equations of motions. The primary contribution of the present work is to provide a comparative study of the natural frequencies obtained by extended rule of mixture and Eshelby-Mori-Tanaka method. The detailed parametric studies are carried out to study the influences various types of the CNTs volume fraction profiles, geometrical parameters and CNTs volume fraction on the free vibration characteristics of FGCNTR plates. The results reveal that the prediction methods of effective material properties have an insignificant influence of the variation of the frequency parameters with the plate aspect ratio and the CNTs volume fraction.

Vibrational Energy Transfer between Carbon Nanotubes and Liquid Water: A Molecular Dynamics Study

The rates and magnitudes of vibrational energy transfer between single-wall carbon nanotubes (CNTs) and water are investigated by classical molecular dynamics. The interactions between the CNT and solvent confined inside of the tube, the CNT and solvent surrounding the tube, as well as the solvent inside and outside of the tube are considered for the (11,11), (15,15), and (19,19) armchair CNTs. The vibrational energy transfer exhibits two time scales, subpicosecond and picosecond, of roughly equal importance. Solvent molecules confined within CNTs are more strongly coupled to the tubes than the outside molecules. The energy exchange is facilitated by slow collective motions, including CNT radial breathing modes (RBM). The transfer rate between CNTs and the inside solvent shows strong dependence on the CNT diameter. In smaller tubes, the transfer is faster and the solvent coupling to RBMs is stronger. The magnitude of the CNT-outside solvent interaction scales with the CNT surface area, while that of the CNT-inside solvent exhibits scaling that is intermediate between the CNT volume and surface. The Coulomb interaction between the solvent molecules inside and outside of the CNTs is much weaker than the CNT-solvent interactions. The results indicate that the excitation energy supplied to CNTs in chemical and biological applications is rapidly deposited to the active molecular agents and should remain localized sufficiently long in order to perform the desired function.