CNT Content Research Articles

Nonlinear impulsive and vibration analysis of nonlocal FG-CNT reinforced sandwich plate by considering agglomerations

This paper is focused on impulsive and subsequent vibration response of a nano-scale composite sandwich plate considering both nonlocal effect and nanoparticle agglomerations. In particular, the core is homogeneous polymethyl methacrylate (PMMA) and the face sheet is PMMA matrix with functionally graded carbon nanotubes (short for FG-CNT). The material properties are given by Eshelby-Mori-Tanaka's approach taking into account of CNT agglomerations. The equations of motion for the FG-CNT reinforced nanoplate are derived based on nonlocal strain gradient theory, Reddy's higher order shear deformation theory and von-Karman nonlinear deformation theory. The impulsive and vibration problems for simply supported FG-CNT plates are solved using Galerkin method and Newton iteration method where the solutions have been verified with the literature. By considering impulsion of step load, exponential load and sinusoidal load and, it is found that weaker size effect, fewer CNT agglomerations, higher CNT content, smaller functional gradient, thinner core, bigger aspect ratio and larger length thickness ratio can enhance the stiffness of the nanoplate and thus will induce smaller center displacement during the load process and higher free vibration frequency after unloading, regardless of load type. However, the subsequent vibration amplitude is significantly influenced by the impulsive load type. Among the material parameters, minimizing size effect and agglomerations could greatly improve the structural stiffness whereas the improvement by varying functional gradient is very limited. It is the first time that a FG-CNT reinforced sandwich plate, especially considering nonlocal effect and nanoparticle agglomerations, is treated in the context of impulsive and subsequent vibration problems. The solutions presented in this paper could provide a benchmark for the design and manufacture of such a composite nanoplate.

Investigation of the bending response of carbon nanotubes reinforced laminated tapered spherical composite panels with the influence of waviness, interphase and agglomeration

In the present study, the bending analysis of multi walled carbon nanotubes (MWCNTs) reinforced laminated tapered spherical composite panels subjected to transverse loading conditions is carried out using the finite element method (FEM) with displacement fields derived from high order shear deformation theory. In this regard, the elastic properties of the polymeric nanocomposite, considering the MWCNTs agglomeration, waviness and interphase thickness between the MWCNTs and polymer matrix were computed by employing various micromechanical approaches. Subsequently, glass-fiber were introduced as a reinforcement phase, and the overall elastic properties of a three-phase MWCNT/fiber/polymer hybrid nanocomposite material were obtained using Chamis model. The accuracy of the developed FE formulation were verified using the experimental and numerical data available in the open literature. After verification, the deflection and stresses of the panel are numerically determined for various taper configurations. Further, detailed parametric analysis is carried out to explore the influence of various parameters such as CNT content, agglomeration, waviness, interphase area, thickness ratio, curvature ratio and taper configurations on the bending results of laminated tapered spherical panels. It was observed that an increase in the weight fraction of CNTs, an equal number of agglomeration parameter and the thickness of the interphase have a positive effect in minimizing the deflection and stresses. It was also observed that the TC-2 and TC-3 taper configurations results the highest and lowest deflection. Finally, it can be concluded the current work can serve as a guide for the effective design and development of CNT reinforced composite structures.

Impedance Analysis and Noise Measurements on Multi Walled Carbon Nanotube Networks.

The electrical impedance characteristics of multi-walled carbon nanotube (MWCNTs) networks were studied as a function of CNT concentrations in the frequency range of 1 kHz–1 MHz. The novelty of this study is that the MWCNTs were not embedded in any polymer matrix and so the response of the device to electrical measurements are attributed to the CNTs in the network without any contribution from a polymer host matrix. Devices with low MWCNT packing density (0.31–0.85 µg/cm2) exhibit a frequency independent plateau in the low-frequency regime. At higher frequencies, the AC conductivity of these devices increases following a power law, characteristic of the universal dynamic response (UDR) phenomenon. On the other hand, devices with high MWCNT concentrations (>1.0 µg/cm2) exhibit frequency independent conductivity over the entire frequency range (up to 1 MHz), indicating that conduction in these devices is due to direct contact between the CNTs in the network. A simple single-relaxation time electrical equivalent circuit with an effective resistance and capacitance is used to describe the device performance. The electrical noise measurements on devices with different MWCNT packing densities exhibit bias-dependent low-frequency 1/f noise, attributed to resistance fluctuations.

Low-temperature sintering of ZnAl2O4 ceramics with 4CuO-TiO2-2Nb2O5 composite oxide sintering aid

In this work, 4CuO-TiO2-2Nb2O5 (CTN) composite oxide was added to ZnAl2O4 as sintering aid. XRD analysis revealed that trace amount of new phases formed in the ceramic samples with CTN, which might promote the low temperature sintering of ZnAl2O4 ceramics. The sample with 2 wt% CTN addition sintered at 1125 °C can achieve the highest thermal conductivity of 8.6 W/m·K and the lowest microwave dielectric loss of 3.59 × 10−4. The sintering temperature and thermal conductivity of ZnAl2O4 ceramics decreased while the dielectric constant and loss increased with the increase of the CNT contents. ZnAl2O4 ceramics can be sintered at a low temperature of 950 °C with the CTN content increasing to 10 wt%, which make it a potential material for the low temperature co-fired ceramics (LTCC) application.

Impact of CNT Concentrations on Structural, Morphological and Optical Properties of ZnO: CNT Nano composite Films

In this study, zinc oxide: carbon nanotube (ZnO: CNT) nano composite films with varying CNT concentrations (0,3,5,10, and 15) wt percent were generated utilizing the pulsed laser deposition (PLD) procedure on clean glass substrates at room temperature. The impact of CNT concentration on the structural, morphological, and optical features of ZnO: CNT nano thin films as deposited was examined. X-ray diffraction was used to evaluate the structure of the generated ZnO: CNT thin films, while an atomic force microscope was used to explore the morphological features of the nano films (AFM) and field emission scan electron microscopy (FESEM). The optical properties of prepared thin films were characterized and studied using UV-VIS-NIR spectrophotometer. The structures of prepared ZnO: CNT with different concentration of CNT thin films were polycrystalline. ZnO: CNT nano thin films were synthesized in hexagonal phase and the dominate orientation is (101). The crystallite sizes are 32 and 26 nm for (101) and (100)) planes for ZnO and ZnO: 15% CNT nano films respectively. These crystallite size are decreased with increasing CNT (0, 3,5,10 and 15) wt. %. The lowest grain size can be shown for ZnO, while the largest grain size can be seen in ZnO: CNT nano thin with 15% concentration, whereas FESEM micrographs displayed a typically rough, pronounced microstructure, with surface protrusions. The energy gap (Eg) of ZnO: CNT nano thin film with various concentrations is computed. The result analysis shows that Eg decreased with increasing CNT weight concentration. This type of behaviors make the prepared films are good candidate for broad range of applications such as optoelectronic and display devices.

Selective laser sintering of carbon nanotube–coated thermoplastic polyurethane: Mechanical, electrical, and piezoresistive properties

Flexible and electrically conductive carbon nanotube/thermoplastic polyurethane (CNT/TPU) nanocomposites have been herein fabricated by selective laser sintering (SLS) for the applications of wearable electronics and strain sensors. CNT/TPU nanocomposite powders were systematically developed by a latex-based technique. The effects of CNT content on the SLS processability of nanocomposite powders and the mechanical, electrical, and piezoresistive properties of SLS-printed specimens were investigated. It was found that the CNT improved the electrical conductivity and strain sensing performance of the printed parts, but excessively high CNT content led to high melt viscosity, deteriorated sintering behavior, and hence degraded mechanical properties. The 2.0 wt% CNT/TPU nanocomposite fabricated by SLS exhibited enhanced electrical conductivity (seven orders of magnitude higher than the neat TPU), high piezoresistive sensitivity (gauge factor of 60 at a tensile strain of 20%), and a wide sensing range (0‒130% strain). A mathematical model based on the tunneling theory was established to describe and predict the strain sensing performance of the printed nanocomposites. This study provides profound insights into the development of multi-functional nanocomposites by SLS for their applications in flexible strain sensors.

Effect of stabilization method on the natural convection in an inclined cavity filled with MWCNTs/water nanofluids

The present work has been studied to investigate the effect of stabilization method on natural convection in an inclined cavity filled with MWCNTs/ water. Two cubic enclosures with different aspect ratio and slopes are tested. Non-covalent and covalent functionalization of MWCNT have been done by using gum Arabic (GA) and the amino acid Ethylene diamine (EDA) respectively. The natural convection heat transfer coefficient decreases with incrementing the concentration of nanoparticles. However, the slope of reducing of the heat transfer coefficient in lower concentrations is small and by increasing concentration, this slope enhances. The effect of changing the Rayleigh number is lower than the effect of incrementing the concentration of CNT on the Nusselt number. By reducing the inclination angle from 90° to 0°, the convection heat transfer increases for both covalent and non-covalent functionalized nanoparticles. Also, it was found that changing the inclination angle does not affect the Nusselt number at the low Rayleigh numbers. With incrementing the Rayleigh number and changing the inclination angle, changing of the heat transfer coefficient at Ar = 2 was more than Ar = 1. The free convection heat transfer coefficient of the non-covalent method had more reduction in comparison to the covalent method.

Enhancing Seebeck coefficient and electrical conductivity of polyaniline/carbon nanotube–coated thermoelectric fabric

In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the Seebeck coefficient with the addition of CNT. The electrical conductivity increased from 0.011 to 0.1345 S/cm with the increment of CNT from 0.5 to 10 wt%. The highest Seebeck coefficient of 11.4 μV/K was observed for the sample containing 5 wt% CNT at 338 K where the maximum power factor of 1.598×10−3 μWm−1K−2 was obtained for the fabric coated with nanocomposite containing 10 wt% CNT.

The Effect of Thermal Cycling on the Tensile and Shear Behaviors of the Carbon Nanotube-Reinforced Epoxy

The aim of this research is to study the tensile and shear properties and mechanical behavior of carbon nanotube- (CNT-) reinforced epoxy after the resulting composites have been exposed to different thermal cycling environments. Single-walled carbon nanotubes (SWCNTs) are cylindrical molecules that consist of rolled-up sheet of single-layer carbon atoms (graphene) with a diameter of less than 1 nanometer (nm). Thermal cycling environments can exist in many conditions, such as in-earth orbit for satellites which rotate around the earth and pass through the sun illumination and earth’s shadow, and for airplanes which fly in different altitudes with different temperatures. Carbon nanotube-reinforced epoxy is one of the nanocomposite materials which have been broadly used in many applications such as aerospace, automotive, electronics, and other industries. The goal of this study is to fabricate this nanocomposite with different multiwall and single-wall CNT concentrations and expose it to different thermal cycle numbers and determine the changes in tensile and shear properties and failure characteristics. For this purpose, tension and short-beam tests have been used in this research. The addition of multiwall CNT produces better mechanical properties compared to the use of SWCNT reinforcement. However, unreinforced epoxy showed the highest mechanical properties.

Heat-Treated Ni-CNT Nanocomposites Produced by Powder Metallurgy Route.

Nickel nanocomposites reinforced by carbon nanotubes (Ni-CNTs) are one of the possible candidates for applications in highly demanding industries such as the automotive and aerospace industries. As is well known, one of the limitations on the use of some materials in these applications is thermal stability. Some components in these industries are frequently subjected to high temperatures, which is crucial to understanding their microstructures and, consequently, their mechanical properties. For this reason, the main objective of this research is to understand the microstructural evolution of Ni-CNTs nanocomposites when subjected to heat treatment. The nanocomposites with varying levels of CNT content were produced by powder metallurgy, and unreinforced nickel was used for comparison purposes under the same conditions. The dispersion of CNTs, a critical aspect of nanocomposites production, was carried out by ultrasonication, which already proved its efficiency in previous research. The heat treatments were performed under high vacuum conditions at high temperatures (700 and 1100 °C for 30 and 120 min, respectively). Microhardness tests analyzed the mechanical properties while the extensive microstructural evaluation was conducted by combining advanced characterization techniques such as scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and high-resolution TEM. The obtained results are promising and show that the presence of CNTs can contribute to the thermal stability of the Ni-CNT nanocomposites produced.

Novel paraffin wax/ultra‐high molecular weight polyethylene composite phase change materials modified by carbon nanotubes with excellent combination property

AbstractPhase change materials store and release heat energy in the process of phase change, so as to realize the effective recovery and utilization of heat energy. In this work, ultra‐high molecular weight polyethylene (UHMWPE)@carbon nanotubes (CNT) 3D porous matrix were fabricated by rotary sintering. By vacuum adsorbing paraffin wax (PW) into UHMWPE@CNT porous matrix, composite phase change materials (CPCM) with excellent shape stability and mechanical properties were obtained. In addition, thermal gravimetric analysis (TG) results showed that the thermal stability of PW in CPCM was significantly improved. Moreover, the highest thermal conductivity of CPCM was 0.31 W m−1 K−1 at a relatively low content of CNT, which was 1.71 times that of CPCM without CNT. CNT was uniformly dispersed in the porous matrix of UHMWPE to enhance the thermal properties of CPCM. Especially when the CNT content was 1.5%, the thermal storage performance and photothermal conversion efficiency of CPCM were effectively improved. Therefore, the CPCM prepared by this method with excellent combination property, had great application prospect in energy storage.

Outstanding in-situ CNTs on Fe-pillared nanoclay for high-performance polymer nanocomposites

The successful and novel synthesis of in-situ multi-walled carbon nanotubes (MWCNTs) on a pillared montmorillonite (Mt) nanoclay was achieved. These novel nanofillers were mixed with poly(methyl methacrylate) (PMMA) polymer to study electrical properties of these nanocomposites. The trinuclear Fe (III)-acetato complex, [Fe3(OOCCH3)7·OH·nH2O]+NO3−, was synthesized and analyzed by chemical analysis and FTIR spectroscopy, and was used as the precursor for the CNT synthesis. The complex proved to be an excellent precursor for the synthesis of CNTs. CNT-clay hybrid nanofillers with varying CNT contents and qualities were observed and investigated using XRD, TGA, XPS, Raman, SEM, and TEM. The ID/IG of CNTs decreased from 1.92 for 0.5 CEC of the iron complex to 0.72 for 6 CEC CNTs. The XRD indicated that Mt. layers were intercalated with iron species during the ion-exchange process, and further exfoliated due to the growth of CNTs. The synthesis yield increased at higher iron concentrations, i.e., 83.4% for 6 CEC CNTs. The 6, 7, and 8 CEC CNTs exhibited smaller diameter CNTs, 14.6 (±4.4), 18.2 (±4.4), and 16.5 (±6) nanometers, when compared to those of lower catalyst concentrations. The 8 CEC CNTs showed 3.5 S m−1 of conductivity, and ~ 90% of the sp2 structure. The electrical properties of PMMA nanocomposites showed these these CNT-clay hybrid fillers are effective for charge storage applications.

Effect of Strain on Heating Characteristics of Silicone/CNT Composites.

In this work, silicone/carbon nanotube (CNT) composites were produced using a spread coating process, followed by morphological investigations and determination of their electrical properties and heating behaviour through the application of electric potential. Composites containing varying amounts of CNT (1–7%) were investigated for their thermal behaviour with the use of an IR camera. Subsequently, thermal behaviour and electrical properties were measured when the samples were stretched (up to 20%). With the 7% CNT composites, which had a conductivity of 106 S/m, it was possible to achieve a temperature of 155 °C at a relatively low voltage of 23 V. For high CNT contents, when the potential was controlled in such a way as to maintain the temperature well below 100 °C, the temperature remained almost constant at all levels of strain investigated. At higher potentials yielding temperatures around 100 °C and above, stretching had a drastic effect on temperature. These results are critical for designing composites for dynamic applications requiring a material whose properties remain stable under strain.

Novel PTFE/CNT composite nanofiber membranes with enhanced mechanical, crystalline, conductive, and dielectric properties fabricated by emulsion electrospinning and sintering

Polytetrafluoroethylene/multiwalled carbon nanotubes (PTFE/CNT) nanofiber membranes were prepared by emulsion electrospinning and high temperature sintering. Compared with pure PTFE nanofiber membranes, at low CNT content, the mechanical properties of PTFE/CNT nanofiber membranes were improved. For example, the tensile strength of PTFE/CNT (0.5 wt%) composite nanofiber membranes increased from 2.5 MPa to 5.92 MPa, and the elongation at break increased from 123% to 330%. The conductivity of PTFE/CNT (5 wt%) nanofiber membranes reached 1.5 S/m. Meanwhile, the dielectric constant and dielectric loss of PTFE/CNT (5 wt%) nanofiber membranes are 58.46 and 2372.3 respectively. The PTFE/CNT (1 wt%) composite nanofiber membrane displayed an optimal reflection loss of −53.2 dB with a thickness of 2.0 mm. After adding CNT, water contact angle value was slightly reduced from 135° of pure PTFE to 133.55°, but still has good hydrophobicity. What's more, the obtained PTFE/CNT nanofiber membranes also showed good thermal properties and permeability as well as oil absorption characteristics, endowing it many great potential applications, such as electromagnetic wave absorption, electronic packaging, and oil-water separation and so on.

Influence of water ingress on the electrical properties and electromechanical sensing capabilities of CNT/cement composites

The present study investigated the influences of water ingress on the electrical resistivity and electromechanical sensing responses of CNT/cement composites. The water absorption, mechanical, electrical, and electromechanical sensing characteristics of the composites were assessed in terms of water absorption rate, compressive strength, electrical resistivity, tunneling-induced electrical resistivity, fractional change in the resistivity (FCR), and R-squared value. The water absorption rate increased, and compressive strength decreased as the CNT content and water-to-cement ratios increased. These were ascribed to an addition of the dispersion agent and water which caused microstructures of the composites more porous. In addition, the tunneling-induced electrical resistivity test exhibited that the tunneling effects became more pronounced with increase of the CNT and water contents. In electromechanical sensing test, FCR value reached the highest level at CNT content 0.2%, and R-squared value enhanced as water ingress was reduced. In this regard, it can be concluded that the new types of materials with high hydrophobicity are necessary to improve the stability of the electrical electromechanical sensing capability of the CNT-based cementitious sensors as exposed to the water conditions.

Quantifying Mechanical Abrasion of MWCNT Nanocomposites Used in 3D Printing: Influence of CNT Content on Abrasion Products and Rate of Microplastic Production.

Manufactured nanomaterials (MNMs) are incorporated as "nanofillers" into consumer products to enhance properties of interest. Multiwalled carbon nanotubes (MWCNTs) are known for their unique properties and have many applications in polymers. However, the release of MWCNTs during the nanoenabled product life cycle is concerning. During the use phase, mechanical stresses can produce fragmented materials containing MNMs. The degree of MNM release, the resulting exposure to these materials, and the potential impacts of their release are active research topics. In this study, we describe methodological improvements to study the abrasion of plastics containing MNMs (nanocomposites) and report on characteristics of abrasion products produced and rates of microplastic production. The abrasion device developed for this work allows for the measurement of power inputs to determine scaled release rates. Abrasion rates for plastics used in 3D printing were found to be 0.27 g/m2/s for the PETG polymer and 0.3 g/m2/s for the 2% MWCNT-PETG nanocomposite. Embedded and protuberant MWCNTs appeared to impact the particle size, shape, hydrophobicity, and surface charge of the microplastics, while the inclusion of MWCNTs had a small effect on microplastic production. Measurements of power input to the abrasion process provided a basis for estimating microplastic production rates for these nanocomposites.

Dynamic Characterisation of Honeycomb CNT Reinforced Sandwich Composite Structure

The dynamic characterization of honeycomb sandwich structure with CNT reinforced hybrid composite face sheet is performed using Finite element simulation. The element simulations. The Potential and Kinetic energies of the honeycomb sandwich beam were derived using classical laminate beam theory and Mindlin theory. The governing equations of motion for the sandwich composite beam is made up of Nomex material with a hybrid composite face sheet reinforced with CNT are obtained by applying the Hamilton rule in the finite element model. The functionality of current finite element modeling has been investigated to proving the dynamic properties acquired from the improved finite element model with the solution obtainable in the previous literature. A further various parametric study is performed to understand the effect of CNT content, thickness ratio, and boundary constraints on the honeycomb sandwich composition of dynamic properties with reinforced CNT of the hybrid composite face sheet is performed using finite element simulation. The CNT content in the honeycomb sandwich beam containing a remarkable effect on the natural frequency.

Electrical and Optical Properties of CNTs Additives Chalcogenide Glasses

Glasses have been used as the most versatile engineering materials for more than five decades. Chalcos is a Greek word which means ore former and glasses prepared by particular chalcogenide of group VI element of the periodic table or by their compounds have been known for more than 50 years as an optical material. The primary objective is to provide up to date description of the development in the field of optical and electrical properties of MWCNTs additive chalcogenide glasses. An extensive survey of relevant literature was carried out using sophisticated libraries, virtual media, different research laboratories, internet and also by personal contact with the senior researcher of this field. The exponential increase in D.C. conductivity was observed on increasing the CNT concentration. Inter nanotube connections increase which results in modification of chemical bond formation with increased CNT concentration. It has been observed that the optical band gap of CNT doped chalcogenide glass increases which may be attributed to the fact that CNT added to to the glasses retards the motion of charge carriers and may raise the optical bandgap. The electrical and optical properties of CNT additives chalcogenide glasses have been reviewed. Several applications based on CNT doped glasses have also been discussed, including the development of ionic memories, sensors, optical waveguides, holography, solid-state batteries, optical, and non-linear optical devices.

Fluororubber superhydrophobic coating: preparation, characterisation, and EMI shielding performance

ABSTRACT Herein, we report the preparation and characterisation of fluororubber coated superhydrophobic Poly (ethylene tetrapthalate) (PET) fabric and polyurethane (PU) sponge. The coating surface structure over PET fabric is more stable and hydrophobic (water contact angle (CA) ≥ 153°) with mass ratio 5:1 of fluororubber/carbon nanotubes (CNTs). Fluororubber/CNT coated PET fabric has good wear resistance and hydrophobicity with repeated friction. PU sponge coated with the ratio 8:4 of fluororubber/carbon black (CB) is the best ratio showing water CA ≥ 157°. Fluororubber/CB coated PU sponge has good oil-water separation and repeated oil absorption ability. Its absorption ability to various solvents and oils can reach 20–50 times its own weight. The EMI SE of fluororubber coating in 8.2–12.4 MHz range has improved with the increased CNTs content. The highestEMI SE valuee, i.e. 52.30 db achieved at 2.0 wt% CNT content. Developed fluororubber superhydrophobic coating material has good potential in the EMI shielding application.

Effects of Impedance and Dielectric Loss on the Electromagnetic Shielding Performance of an Ultrathin Carbon Nanotube Buckypaper‐Reinforced Silicon Carbide Nanocomposite

An ultrathin carbon nanotube buckypaper‐reinforced silicon carbide (CNT/SiC) nanocomposite with a thickness of 500 μm and density of 1.78 g cm−3 is prepared by combining a CNT buckypaper preform and an in situ‐synthesized SiC matrix. A uniform CNT distribution and a high CNT content (≈35 vol%) are achieved in the nanocomposite. The SiC matrix is composed mostly of nearly spherical nanograins and submicrometer grains. No residual Si is found. The imaginary permittivity and loss tangent of the nanocomposite throughout the X‐band are 96–257 and 0.44–7.03, respectively. The normalized input impedance is 0.0012–0.0174 over the X‐band. The nanocomposite has an average total shielding effectiveness (SE) of 30 dB throughout the X‐band. The nanocomposite has a reflection coefficient of 0.9651–0.9915, an absorption coefficient of 0.0077–0.0338, and a transmission coefficient of no more than 0.0012 throughout the X‐band, indicating excellent electromagnetic SE. The nanocomposite is well suited for shielding applications, and the SE due to internal absorption (SEA) depends mostly on the impedance matching condition rather than the dielectric loss capacity. The variation with frequency of SEA is not consistent with that of the imaginary permittivity or loss tangent but approximately consistent with that of the normalized input impedance.