Material Properties Of Carbon Nanotubes Research Articles

Gate Capacitance Coupling of Double-Gate Carbon Nanotube Network Transistors.

Carbon nanotube (CNT) network channels constructed using a high-purity CNT solution for use in CNT thin-film transistors have the advantages of the possibility of requiring a low-temperature process and needing no special equipment. However, there are empty spaces between individual CNTs, resulting in unexpected effects. In this study, double-gate (DG) CNT network transistors were fabricated and measured in four different configurations to observe the capacitive coupling effects between the top gate (TG) and bottom gate (BG) in the DG structure. As a result, the electrical characteristics measured with the BG with a thicker gate oxide while floating the TG were similar to those measured with the TG with a thinner gate oxide. A comparison of the measured transfer curves showed that TG and BG were strongly coupled through the empty spaces in the channels. In addition, we evaluated the capacitance coupling effect due to changes in the CNT density, which is closely related to the empty space of the network channel. Finally, we proposed a method to determine the effective gate capacitance by considering the empty spaces between CNTs, which enabled the accurate evaluation of mobility. The effects of these materials were demonstrated by fabricating transistors using Al2O3, HfO2, and ZrO2 as TG oxide materials. By focusing on considerations based on the properties of CNT materials, our study provides valuable insights into accurate electrical modeling and potential advancements in CNT-based devices.

Development of Microwave Filters with Tunable Frequency and Flexibility Using Carbon Nanotube Paper.

This study aims to exploit the distinctive properties of carbon nanotube materials, which are particularly pronounced at the microscopic scale, by deploying fabrication techniques that allow their features to be observed macroscopically. Specifically, we aim to create a semiconductor device that exhibits flexibility and the ability to modulate its electromagnetic wave absorption frequency by means of biasing. Initially, we fabricate a sheet of carbon nanotubes through a vacuum filtration process. Subsequently, phosphorus and boron elements are separately doped into the nanotube sheet, enabling it to embody the characteristics of a PN diode. Measurements indicate that, in addition to the fundamental diode's current-voltage relationship, the device also demonstrates intriguing transmission properties under the TEM mode of electromagnetic waves. It exhibits a frequency shift of approximately 2.3125 GHz for each volt of bias change. The final result is a lightweight and flexible carbon-based semiconductor microwave filter, which can conform to curved surfaces. This feat underscores the potential of such materials for innovative and effective electromagnetic wave manipulation.

Static analysis and boundary effect of FG-CNTRC cylindrical shells with various boundary conditions using quasi-3D shear and normal deformations theory

In this paper, static analysis and the stress concentration phenomenon of functionally graded carbon nanotubes reinforced composite cylindrical shells with various boundary conditions are explored by using higher-order shear-normal deformation theory and an analytical approach. Five types of distributions of reinforced carbon nanotubes are considered, that is, uniform and four kinds of functionally gradient distribution of carbon nanotubes along with the thickness of the shell. Effective material properties of carbon nanotubes reinforced composite are estimated to the rule of mixture. The governing equations for FG-CNTRC cylindrical shells with various boundary conditions are solved analytically using simple trigonometric series and the Laplace transform. Moreover, the transverse shear and normal stress are reconstructed using 3D linear elasticity equilibrium equations. The present model is validated by comparing its numerical results with those of published works, including the 3D exact model. Using higher-order shear-normal deformation theory, this article has focused on investigating the stress concentration phenomenon, the distribution of stress components in the near-boundary region, and also assessing the effects of various parameters on the stress state of the FG-CNTRC cylindrical shells.

Buckling analysis of FG cylindrical nano shell integrated with CNTRC patches

Buckling analysis of a functionally graded (FG) cylindrical nano shell is studied in this paper based on nonlocal elasticity theory and first-order shear deformation theory. The nano shell is made from a combination of ceramic and metal integrated with carbon-nanotube reinforced composite (CNTRC) sheets on outer radius. The reinforced composite nano shell is resting on Pasternak’s foundation. The governing equations of motion are derived using vitual work principle. The effective material properties of carbon-nanotube reinforced composite (CNTRC) sheets are evaluated using rule of mixture. A comparative study is performed before full presentation of numerical results for verification of the model and solution procedure. A large parametric analysis is performed to investigate effect of dimensions of the core as well as CNTRC sheets, CNT volume fraction, nonlocal parameter, number of CNTRC sheets, FG-index and foundation parameters on the buckling results.

Buckling analysis of thin rectangular FG-CNTRC plate subjected to arbitrarily distributed partial edge compression loads based on differential quadrature method

This paper investigates the buckling behaviors of thin rectangular functionally graded carbon nanotubes reinforced composite (FG-CNTRC) plate subjected to the arbitrarily distributed partial edge compression loads. Three distribution types of carbon nanotubes (CNTs) are considered and the effective material properties of carbon nanotube reinforced composite are given according to the extended rule of mixture, in which the distribution uncertainty of CNTs is also taken into account. Based on the differential quadrature method (DQM) and work equivalent method, the pre-buckling in-plane stress distribution of thin rectangular FG-CNTRC plate are determined firstly. Then the accurate critical buckling loads and buckling modes of FG-CNTRC plate are consequently obtained. By comparing with the results in published literatures, the feasibility and accuracy of present numerical method are validated. Finally, the systematic parametric studies are carried out to elaborate the effects of distribution type, volume fraction and distribution uncertainty of CNTs as well as the distribution width, position and distribution type of partial edge compression loads on the buckling behaviors of thin rectangular FG-CNTRC plate for the first time.

Analysis of sandwich Timoshenko porous beam with temperature-dependent material properties: Magneto-electro-elastic vibration and buckling solution

Vibration and buckling analysis of a magneto-electro-elastic sandwich Timoshenko beam with a porous core and poly-vinylidene fluoride (PVDF) matrix reinforced by carbon nanotubes (CNTs) is considered as face layers and material properties of CNTs and PVDF are assumed to be temperature-dependent. Different CNT distribution patterns including uniform distribution, AV (which top and bottom face sheets have functionally graded-A (FG-A) and functionally graded-V (FG-V) CNT distribution patterns, respectively) and VA patterns are employed. The governing equations of motion are derived based on Timoshenko beam theory, and Navier's solution is used to solve these equations. The sandwich beam resting on a Pasternak foundation and face layers are subjected to electric and magnetic potentials. The effect of different parameters such as porosity coefficient, electric and magnetic potential, parameters of foundation, and geometrical parameters are investigated on vibration and buckling behavior of the sandwich beam. Numerical results of this paper show that porosity distribution has a significant effect on the stiffness of the sandwich beam. The results can be used for future analysis of magneto-electro-mechanical sandwich systems as actuators and sensors.

Nonlinear free vibration analysis of functionally graded rotating composite Timoshenko beams reinforced by carbon nanotubes

In this paper, the linear and nonlinear free vibrations of functionally graded rotating composite Timoshenko beams reinforced by carbon nanotubes are presented. The formulation is based on the assumptions of Timoshenko beam theory in addition to consideration of the nonlinear von Karman strain–displacement relationship. The effective material properties of carbon nanotube reinforced composites are determined employing the Mori–Tanaka micromechanics model and the extended mixture rule. For the carbon nanotube reinforced composite beams, uniform distribution and four types of functionally graded distribution patterns of single-walled carbon nanotube reinforcements are considered. A differential transform method is applied on the nondimensionalized equations of motion to release the flapping modeshapes and the associated natural frequencies. The direct method of multiple scales is implemented to derive the effective nonlinearity and the corresponding nonlinear natural frequency. The accuracy of the present outcomes is validated by the comparison with the results given in the literature. The numerical results are presented in both tabular and graphical forms to investigate the effects of nanotube volume fractions, distribution types of the carbon nanotubes, and rotation speed on linear and nonlinear free vibration characteristics of carbon nanotube reinforced composite beam. The results demonstrate the important role of carbon nanotube distribution profile on linear and nonlinear free vibration features.

Buckling and postbuckling of axially-loaded CNT-reinforced composite cylindrical shell surrounded by an elastic medium in thermal environment

Buckling and postbuckling behaviors of nanocomposite cylindrical shells reinforced by single walled carbon nanotubes (SWCNTs), surrounded by an elastic medium, exposed to a thermal environment and subjected to uniform axial compression are investigated in this paper. Material properties of carbon nanotubes (CNTs) and isotropic matrix are assumed to be temperature dependent, and effective properties of nanocomposite are estimated by extended rule of mixture. The CNTs are embedded into matrix via uniform distribution (UD) or functionally graded (FG) distribution along the thickness direction. Governing equations are based on Donnell’s classical shell theory taking into account von Karman-Donnell nonlinear terms and interaction between the shell and surrounding elastic medium. Three-term form of deflection and stress function are assumed to satisfy simply supported boundary conditions and Galerkin method is applied to obtain load-deflection relation from which buckling and postbuckling behaviors are analyzed. Numerical examples are carried out to analyze the effects of CNT volume fraction and distribution types, geometrical ratios, environment temperature and surrounding elastic foundation on the buckling loads and postbuckling strength of CNTRC cylindrical shells.

A π-type Thermoelectric Generator Wrapped with Doped Single-walled Carbon Nanotube Sheets

The upcoming IoT society requires portable energy harvesters including thermoelectric generators around room temperature. Here we show a prototype, lightweight thermoelectric generator based on doped single-walled carbon nanotubes. The generator is fabricated by the standard printing and cut-and-paste techniques. The 12 cm-scale generator with a commercial DC-DC converter exhibits thermoelectric outputs high enough to drive small devices such as a light-emitting diode (LED). We believe such demonstration facilitates the studies not only of further improvements in the thermoelectric properties of carbon nanotube materials but also of the novel design for thermoelectric generators on the basis of thermal engineering.

Effects of carbon nanotube inclusion into the carbon fiber reinforced laminated composites on flexural stiffness: A numerical and theoretical study

Because of increased usage areas, and advances in characterization of the nanostructured materials, determination of the engineering properties of composites that includes carbon nanotubes has gained importance. It is possible to designate material properties of carbon nanotube based composites theoretically and experimentally. In this study, engineering constants of carbon nanotube based unidirectional carbon fiber reinforced composite lamina determined theoretically with two different approaches. Then, a composite plate whose laminas were stacked up as a [0°/+45°/-45°/90°]s layup was built up in ANSYS, ACP Module. Finally, three point bending analyzes were performed separately under concentrated and distributed load. The results showed that there were negligible differences between the engineering constants obtained from two different theoretical approaches. Engineering constants, E1, E2, G12 and G23, increased as the added carbon nanotube fraction is increased. Besides that, flexural rigidity of composite plate also showed ever-decreasingly increase, as carbon nanotube content is increased. The results of theoretical and numerical bending analyzes exhibited a good agreement with the maximum percentage relative error of 9.1.

Thermal and mechanical buckling analysis of FG carbon nanotube reinforced composite plates using modified couple stress theory and isogeometric approach

Abstract This paper investigates the thermal and mechanical buckling analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) plates by using isogeometric analysis (IGA) based on modified couple stress theory (MCST). A refined hyperbolic shear deformation theory is used for buckling analysis, which satisfies free transverse shear stress conditions on the top and bottom surfaces of plate without a need for shear correction factor. The material properties of carbon nanotube reinforced composite plates are assumed to be temperature-dependent. For numerical analysis the IGA method using B-Spline or Non-Uniform Rational B-Spline (NURBS) functions is employed. The obtained results are compared with those available in the literature. Also, the influence of different parameters on mechanical and thermal buckling analysis is investigated. These parameters include material length scale parameter, boundary conditions, aspect and length-to-thickness ratios of plate, different types of FG-CNTRC distribution, volume fraction of CNTs and temperature dependency.

Uncertainty analysis for wave dispersion behavior of carbon nanotubes embedded in Pasternak-type elastic medium

At nano-scale, the molecular defects and manufacturing tolerances of carbon nanotubes (CNTs) both would introduce inevitable uncertainties. In this paper, a theoretical framework based on interval analysis method is presented to study the wave-dispersion behavior of CNTs embedded in a Pasternak-type elastic medium with uncertain material properties. Different from probabilistic analysis approach, the material properties of CNTs are considered as uncertain-but-bounded variables, which can overcome the massive information required to set up the probabilistic distribution function. Based on the nonlocal Timoshenko beam theory, the wave-dispersion relationship of the embedded CNTs is derived. The upper and lower bounds of the wave frequencies are predicted under different elastic foundation and size scale parameters. It is demonstrated that the uncertain material properties have considerable effect on the wave-dispersion behavior of CNTs, and the size scale and elastic medium will also affect the wave-dispersion response of CNTs significantly. The Monte Carlo simulation is also presented to validate the proposed interval analysis method. The numerical results presented in this paper provide useful guidelines for employing CNTs as reinforced fibers to enhance the conventional composite materials.

Free Vibration Behavior of Carbon Nanotube Reinforced Composite Conical Shell Panel Under Thermal Environment

The free vibration of carbon nanotube reinforced composite conical shell panel is examined under temperature field. In this analysis, single-walled carbon nanotube and poly(m-phenylenevinylene-co-2,5-dioctoxy-pphenylenevinylene) are used as fibre and matrix materials, respectively. The material properties are considered as temperature-dependent. The effective material properties of carbon nanotube reinforced composite panel are evaluated through the extended rule-of-mixture. The finite element model is prepared using commercially available finite element tool ANSYS APDL. An eight node Serendipity shell element (SHELL281) is used to discretize the present conical model. The displacement field is framed in the first-order shear deformation theory with six degrees of freedom. The Block Lanczos eigenvalue extraction method is used to obtain the frequency responses. In order to obtain the appropriate mesh density for the said model, the convergence study is executed for various mesh sizes. The present results are compared and validated with the previously reported results. Finally, the influences of different parameters such as length-to-thickness ratio, volume fraction and temperature on the frequency responses of the carbon nanotube reinforced composite conical shell panel are demonstrated through numerical illustrations. The results reveal that the frequency parameters of conical shell panel enhance with the volume fraction and the length-to-thickness ratio, whereas reduce with the temperature value.

Effect of Perforation on the Bending Behavior of Temperature-Dependent Carbon Nanotube Reinforced Composite Plate

In the present article, the bending behaviour of carbon nanotube reinforced composite plate subjected to thermomechanical loading is examined with and without perforations. For the computational purpose, fully clamped support condition is considered. The carbon nanotube reinforced composite plate is comprised of single-walled carbon nanotube reinforced composite as fibre and PmPV as matrix material. The extended rule-of-mixture is employed to evaluate the temperature-dependent material properties of carbon nanotube reinforced composite panel. The bending responses are obtained through finite element tool ANSYS APDL via eight-nodded shell element (SHELL281) with forty eight degrees-of-freedom per element. The kinematic model of the present carbon nanotube reinforced composite plate is based on the first-order shear deformation theory. To exhibit the efficacy of the present model, the present responses are compared with those of the previously published literature. The effect of different parameters such as temperature, thickness ratio, volume fraction and perforation on the bending behaviour of carbon nanotube reinforced composite plate is illustrated through numerous numerical examples.

Numerical study on the thermal buckling analysis of CNT-reinforced composite plates with different shapes based on the higher-order shear deformation theory

In the present study, based on the higher-order shear deformation plate theory, the unified numerical formulation is developed in variational framework to investigate the thermal buckling of different shapes of functionally graded carbon nanotube reinforced composite (FG-CNTRC) plates. Since the thermal environment has considerable effects on the material properties of carbon nanotubes (CNTs), the temperature-dependent (TD) thermo-mechanical material properties are taken into account. In order to present the governing equations, the quadratic form of the energy functional of the plate structure is derived and its discretized counterparts are presented employing the variational differential quadrature (VDQ) approach. The discretized equations of motion are finally obtained based on Hamilton's principle. In order to convenient application of differential quadrature numerical operators in irregular physical domain, the mapping procedure is considered in accordance to the conventional finite element formulation. Some comparison and convergence studies are performed to show validity and efficiency of the proposed approach. A wide range of numerical results are also reported to analyze the thermal buckling behavior of different shaped FG-CNTRC plates.

Finite rotation three and four nodes shell elements for functionally graded carbon nanotubes-reinforced thin composite shells analysis

In this paper, we address the extension of the Kirchhoff shell model to non-linear analysis of functionally graded carbon nanotubes-reinforced thin composite shells (FG-CNTRCs). The present model can bring up two levels of analysis: geometrically non-linearities and nanostructures with the possibilities of two type of discretization. Either, three and four nodes finite shell elements are implemented to analyze as well as predict the non-linear bending behavior of FG-CNTRC shell structures. Uniform (UD) and three graded distributions of carbon nanotubes (CNTs) which are FG-V, FG-O and FG-X are considered. These distributions are uniaxially aligned in the axial direction of the shell and functionally graded along the thickness direction. The material properties of CNTs are estimated using the modified rule of mixture and the size dependence of these CNTs is taken into account via the introduction of some efficiency parameters. Three numerical examples of FG-CNTRC plates, hyperboloidal and cylindrical shells are presented to highlight the applicability and effectiveness of the present finite element model notably for thin structures. The effect of CNT profiles, CNT volume fractions and others geometrical parameters on non-linear behavior of such structures are also examined.

Free vibration, bending and buckling of a FG-CNT reinforced composite beam

PurposeThe purpose of this paper is to perform a numerical analysis on the static and dynamic behaviors of beams made up of functionally graded carbon nanotube (FG-CNT) reinforced polymer and hybrid laminated composite containing the layers of carbon reinforced polymer with CNT. Conventional fibers have higher density as compared to carbon nanotubes (CNTs), thus insertion of FG-CNT reinforced polymer layer in fiber reinforced composite (FRC) structures makes them sustainable candidate for weight critical applications.Design/methodology/approachIn this context, stress and strain formulations of a multi-layer composite system is determined with the help of Timoshenko hypothesis and then the principle of virtual work is employed to derive the governing equations of motion. Herein, extended rule of mixture and conventional micromechanics relations are used to evaluate the material properties of carbon nanotube reinforced composite (CNTRC) layer and FRC layer, respectively. A generalized eigenvalue problem is formulated using finite element approach and is solved for single layer FG-CNTRC beam and multi-layer laminated hybrid composite beam by a user-interactive MATLAB code.FindingsFirst, the natural frequencies of FG-CNTRC beam are computed and compared with previously available results as well as with Ritz approximation outcomes. Further, free vibration, bending, and buckling analysis is carried out for FG-CNTRC beam to interpret the effect of different CNT volume fraction, number of walls in nanotube, distribution profiles, boundary conditions, and beam-slenderness ratios.Originality/valueA free vibration analysis of hybrid laminated composite beam with two different layer stacking sequence is performed to present the advantages of hybrid laminated beam over the conventional FRC beam.

Flexural wave propagation in fluid-conveying carbon nanotubes with system uncertainties

Many studies have reported that the material properties of carbon nanotubes (CNTs) show a wide range and exhibit a great of uncertainties. The uncertainty, in turn, will affect the physical behaviors of CNTs. In this paper, an iterative algorithm-based interval analysis method is proposed to deal with the flexural wave propagation characteristics of fluid-conveying CNTs with system uncertainties. To make the conclusion more objective, the properties of the material and fluid are all considered as uncertain-but-bounded parameters, which can effectively describe the uncertainties where few data are available to perform the probabilistic analysis. The upper and lower bounds of the wave dispersion curves are predicted to clarify the influences of the uncertain material and fluid properties on the wave propagation behaviors of fluid-conveying CNTs. It is demonstrated that the widths of the wave frequency and phase velocity behave different at different wavelengths. Besides, the bounds predicted by the probabilistic model are given to verify the present model, and the present model is also validated by comparing with the Monte Carlo simulation. The present model provides some useful guides for using CNTs to convey fluid flows.

Forced vibration of fluid conveying carbon nanotubes considering thermal effect and nonlinear foundations

Nonlinear and linear vibrations of fluid conveying carbon nanotubes considering thermal effects are studied. It is assumed that the nanotube conveying fluid flow has a general type of boundary conditions and is supported on a nonlinear Winkler-Pasternak foundation. The nonlocal Euler-Bernoulli beam theory is implemented to develop the governing differential equation of motion of the nanotube system. Furthermore, the surface effect is considered in the vibration modelling of the carbon nanotubes. The influence of the thermal effect combined with the applied longitudinal force on the vibration performance of the system is examined. The Galerkin procedure is employed to obtain the nonlinear ordinary differential equation and the multiple time-scales method is utilized to study the primary vibration resonance of the system. A parametric sensitivity analysis is carried out to reveal the influence of different parameters on the vibration primary resonance and linear natural frequency. The effects of temperature variation, boundary conditions, foundation coefficients and the fluid flow velocity on the primary resonance and natural frequency of the nanotube are investigated. The effect of temperature on the material properties of carbon nanotube is originally combined with the vibration model. Different types of Zigzag carbon nanotubes are considered and the effects of different parameters, namely, the fluid flow velocity and the temperature variations are compared.

Thermoelastic analysis of functionally graded cylinders reinforced by wavy CNT using a mesh‐free method

In this work, thermoelastic analysis of finite length functionally graded (FG) cylinders reinforced by single‐walled wavy carbon nanotube is investigated by a mesh‐free method. The cylinders are subjected to thermal gradient and mechanical loading. The material properties of carbon nanotube (CNT) and polymer matrix are assumed temperature‐dependent and mechanical properties of the nanocomposite are estimated by a micro mechanical model in volume fraction form. CNT distribution has a linear distribution along the radial direction of axisymmetric cylinder. In the mesh‐free analysis, moving least squares shape functions are used for approximation of displacement field in the weak form of equilibrium equation and the transformation method is used for the imposition of essential boundary conditions. Using the mesh‐free method, temperature distribution of the cylinder is derived and then by considering of the temperature, material properties of nanocomposite and stress distribution of the cylinder are derived. So, the effects of CNT distribution pattern and volume fraction, loading (mechanical or thermal), cylinder length and CNT aspect ratio and waviness are investigated on the thermoelastic behavior of the nanocomposite cylinders. POLYM. COMPOS., 39:2190–2201, 2018. © 2016 Society of Plastics Engineers