Carbon Nanotube Epoxy Research Articles

Bending Analysis of Multiwall Carbon Nanotube Reinforced Functionally Graded Composite Cylindrical Shell

The curved structural components of aircraft, automobiles, and marine vessels, such as cylindrical panels, are primarily exposed to loading, which can result in bending failure, particularly in lightweight structures. The bending analysis of cylindrical panels made of functionally graded multiwall carbon nanotube (FG-MWCNT) epoxy composites is subjective in this study. In the first section, FG-MWCNT composite cylindrical panels are simulated in the ANSYS software. There are three methods for distributing uniaxially aligned reinforcements. The material properties of the carbon nanotubes uniformly distributed and functionally graded over the thickness of the shell structure are estimated using an extended rule of mixture micromechanical model that incorporates certain useful characteristics. To demonstrate the effectiveness and applicability of the proposed finite element approach, deflection data are presented. The analysis of the shell structure's bending includes an investigation of the impact of CNT volume fraction, boundary condition, lengthto-thickness ratio, and other geometrical factors

Effect of immediate curing at elevated temperatures on the tensile and interfacial properties of carbon fiber-epoxy composites

Elevated temperature conditions known to improve curing from the onset and during the process of immediate curing are not available in the field, which can hinder the mechanical performance of these strengthening systems. In this study, mechanical testing and material characterization were conducted to identify the effects of subjecting nanomodified epoxy and fiber-reinforced nanomodified epoxy composites to room temperature (RT) (30 °C) and elevated temperature (110 °C) from the onset of curing. Static tensile testing and interfacial adhesion tests were conducted to evaluate the mechanical performance. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to determine curing characteristics to inform on the immediate curing of nanomodified resins cured under the two temperature conditions. Scanning electron microscopy was performed to identify Carbon nanotube (CNT) dispersion characteristics. Overall, due to the incorporation of CNTs in epoxy, RT curing results in upto 62% increase in strain at failure. By supplying additional energy during immediate curing with elevated temperatures, a 51% increase in strength and 42% increase in Youngs Modulus can be observed in the nanomodified epoxy. In CFRP-epoxy composites, due to the incorporation of CNTs in the epoxy, RT curing results in upto 27% increase in strain at failure. By supplying additional energy during immediate curing with elevated temperatures, upto 133% increase in strain at failure is observed and upto 17% increase in strength is observed. CNTs incorporated in CFRP-epoxy composites demonstrated upto 50% increase in interfacial adhesion whereas supplying additional energy for their immediate curing with elevated temperatures, upto 130% increase in interfacial adhesion was observed. TGA and DSC results supported the mechanical observations and show a need for immediate curing when CNTs are used in epoxy matrices.

CNT thin films based on epoxy mixtures: fabrication, electrical characteristics

The simple scaling of silicon transistors no longer ensures the advantages of high energy efficiency, driving research into nanotechnologies beyond silicon. Specifically, digital circuits based on carbon nanotube (CNT) field-effect transistors promise significant advantages in energy efficiency. However, the inability to perfectly control internal nanoscale defects and the variability of carbon nanotubes hinder the realization of very large-scale integrated systems. In this study, we investigated a novel method for fabricating transistors based on carbon nanotubes (CNTs) using epoxy mixtures, obtained the electrical properties of the transistors, and compared their microstructure and composition via the scanning electron microscopy. The carrier mobility on epoxy-based transistors was 28.87 cm²/V∙s, and the transistor switching frequency was 2.2 MHz. The samples exhibited electrical and physical stability over an extended period of time. The use of carbon nanotubes in epoxy resin as a conducting layer for transistors opens significant prospects in the field of electronics. The CNT-epoxy mixture technology allows for more flexible and rapid fabrication of thin-film transistors compared to classical methods. However, it is not appropriate to speak of a complete replacement; in this study, we present an alternative method for producing thin-film transistors, which may be of interest for specific purposes.

Fabrication of carbon nanotube epoxy prepreg towards lightweight structural composites

Despite improvements in carbon nanotube fiber tenacities, their shear strength continues to limit their performance in composite applications. Shear strength can be improved through resin penetration into the nanotube fiber hierarchical microstructure to enhance internal interfaces. In this work, a manufacturing process uses an ionic liquid and epoxy to simultaneously stretch and infiltrate nanotube roving resulting in a nanotube-epoxy-ionic liquid prepreg. The ionic liquid also serves as a latent curing agent/hardener for the prepreg. After curing, the resulting composite fiber has comparable tenacity and specific modulus to fibers made without epoxy but with improved shear properties. The dry core shear failure mode typically observed in CNT fibers was eliminated and the apparent interfacial shear strength was improved by over an order of magnitude.

Synthesis of nanosized spinel ferrites MnFe2O4 on the surface of carbon nanotubes for the creation of polymer composites with enhanced microwave absorption capacity

Currently, the creation of new protective materials able to absorb the electromagnetic (EM) radiation is an important direction strongly linked to the use of high-tech electronics which leads to EM pollution in a wide range of high frequencies. The wide-band absorption and large bandwidth are two important factors affected the absorbing performance of materials. In this research, the development of polymer nanocomposites based on the multi-walled carbon nanotubes (CNTs) as a conductive component modified by manganese ferrite (MnFe2O4) nanoparticles as a magnetic component made it possible to increase the efficiency of absorption of EM waves in the frequency range 1–41 GHz as a result of good impedance matching characteristics in comparison with pure manganese ferrite. Finally, the absorption coefficient of EM waves in the frequency range of 5–20 GHz for MnFe2O4/0.065 vol.%CNT nanocomposites about 2.5–3 times higher than for MnFe2O4. The present work shows, that the introduction of MnFe2O4/CNT composites into the both amorphous (epoxy resin) and crystalline (polychlorotrifluoroethylene) polymer matrices makes it possible to manage microwave absorbing properties as well as a shift of the region of frequencies of maximum peak values of the absorption coefficient and reflection loss. The obtained relations prove that by the change of the amount of the modifying component (MnFe2O4) on the surface of carbon nanotubes, the content of the MnFe2O4/CNT nanocomposite in the polymer matrixes, and the thickness of the polymer composites it is possible to control the absorption coefficient and reflection loss of EM waves in the high frequency range. The MnFe2O4/0.044CNT–PCTFE and MnFe2O4/0.065CNT–epoxy resin composites exhibit higher bandwidth in relation to other reported composites or structures at the same thickness.

Processing dynamics of carbon nanotube-epoxy nanocomposites during 3D printing

Processing dynamics of carbon nanotube-epoxy nanocomposites during 3D printing

Quantitative evaluation of released nanomaterials from carbon nanotube epoxy nanocomposites during environmental exposure and mechanical treatment

Carbon nanotubes (CNTs) are promising nanomaterials exhibiting high thermal and electrical conductivities, significant stiffness, and high tensile strength. As a result, CNTs have been utilized as additives to enhance properties of various polymeric materials in a broad range of fields. In this study, we investigated the release of CNTs from CNT epoxy nanocomposites exposed to environmental weathering and mechanical stresses. The presence and amount of CNTs released from degraded polymer nanocomposites is important because CNTs can impact physiological systems in humans and environmental organisms. The weathering experiments in this study included nanocomposite exposure to both UV and a water spray, to simulate sunlight and rain exposure, whereas mechanical stresses were induced by shaking and ultrasonication. CNT release from epoxy nanocomposites was quantified by a 14C-labeling method that enabled measurement of the CNT release rates after different weathering and mechanical treatments. In this study, a sample oxidizer was used prior to liquid scintillation counting, because it was shown to reduce interferences from the presence of polymeric materials and achieve a high recovery (95%). Polymer nanocomposite degradation was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and light microscopy. A continuous release of 14C-labeled nanomaterials was observed after each UV and simulated rain exposure period, with 0.23% (mass/mass) of the total embedded mass of CNTs being released from the CNT nanocomposite during the full weathering process, suggesting that the water spray induced sufficient mechanical stress to eliminate the protective effect of the surface agglomerated CNT network. Importantly, additional mechanical stresses imposed on the weathered nanocomposites by shaking and ultrasonication resulted in further release of approximately 0.27% (mass /mass).

Phase and orientation effects in X-ray attenuation of carbonaceous epoxy composites

Composites made of carbon nanotubes (CNTs) reinforced in an epoxy matrix have already been successfully used as electromagnetic interference shielding materials. Different weight fractions of randomly distributed and vertically aligned multiwall carbon nanotubes (MWCNTs), graphite, and carbon fiber reinforced in the epoxy matrix were used to make these composites. The comparisons of percentage attenuation of different composite materials were studied under both diagnostic or hard (narrow beam geometry) and soft X-rays (monochromatic X-rays beam). It was found that the concentration of CNTs and graphite in epoxy composites affects attenuation. The results also demonstrate that the percentage attenuation for CNTs (as made) epoxy composite is always higher than graphite epoxy and treated CNTs epoxy composite at any concentration at the same thickness and tube voltage. This study also confirmed that the metal catalyst particles present in CNTs contribute to a considerable attenuation of X-rays along with CNTs and also demonstrated that the increase in metal content inside CNTs increases the attenuation. For hard X-rays, the orientation of CNTs in composites affects attenuation, and this effect gradually weakens at higher tube voltages. Vertically aligned carbon nanotubes (VACNT) array epoxy, and the thin composites are not suitable to attenuate diagnostic X-rays coming from high tube potential. For thin samples, VACNT array epoxy composites always perform better on attenuation of soft X-rays than randomly oriented CNTs in composites with any other composition lower than 15 wt %. This study also showed that there is a difference in the attenuation of soft X-rays amongst CNTs, graphite, and carbon fiber epoxy composites, which confirms that the attenuation depends on the geometry of the carbon structures. There is a clear effect of the orientation of CNTs in VACNTs epoxy composite on soft X-ray attenuation, and it shows that the radial direction of CNTs attenuates more X-ray radiation than the tube axis direction.

Effects of functionalized CNTs in improving the dielectric, corrosion protection, and mechanical properties of epoxy nanocomposites for automotive/aircraft components

ABSTRACT Excellent mechanical, thermal, electrical, electrochemical, and optical properties can be found in carbon nanotubes (CNTs). The anticorrosive and mechanical properties of CNTs in epoxy resin (EP) coatings have been improved by the integration of zirconium disulfide (ZrS2) and 2-amino−5-(4-methoxyphenyl)−1, 3, 4-thiadiazole (AMPT) for surface modification based on CNTs. The structural, morphological, and dielectric behaviors of the films were characterized for the different formulations of coatings such as EP, EP/CNTs, EP-AMPT/CNTs, EP-CNTs/ZrS2, and EP-AMPT/CNTs-ZrS2 by means of SEM/EDX, TEM, TGA/XRD, XPS, XRD, and contact angle (CA) measurement. As a result, with the addition of only 0.3% AMPT/CNTs-ZrS2, the dielectric constant of EP was increased by 87-fold at 1 Hz. The electrochemical techniques and mechanical testing confirmed that AMPT/CNTs-ZrS2 composite exhibit enhanced anticorrosive and mechanical performance of the EP coating. Superior hydrophobic property of EP-AMPT/CNTs-ZrS2 is confirmed by its WCA of 161º. Furthermore, the resistance of the EP-AMPT/CNTs-ZrS2 was found to be much higher (20.870 MΩ.cm2)] than that of the pure EP (0.112 MΩ.cm2) and the microhardness and tensile strength of EP-AMPT/CNTs-ZrS2 were increased sharply. Therefore, the newly developed EP-AMPT/CNTs-ZrS2 nanocomposite could act as the vital material for coating AA8014 aluminum alloy used in aerospace applications.

Mechanical property improvement of oil palm empty fruit bunch composites by hybridization using ramie fibers on epoxy–CNT matrices

Abstract Oil palm empty fruit bunches (OPEFBs) can be transformed into composite boards with higher selling value when their cellulose is used as a fiber. Manufacturing composites with hybridization techniques can improve their properties. This study combined OPEFBs and ramie fibers in an epoxy–carbon nanotube (CNT) matrix. The proportion of OPEFBs and ramie fibers was varied (3:7, 5:5, and 7:3), with a total fiber content of 10% by volume and a matrix of 90% by volume. Alkali treatment using NaOH solution was applied to the fiber to remove impurities from the surface. CNTs were functionalized using nitric acid followed by hydrogen peroxide to improve compatibility. Surface treatment was conducted on fibers and CNTs to increase the bonds between these components in the composite material. The hybridization of OPEFBs/ramie fibers improved the tensile strength in the 3:7TR, 5:5TR, and 7:3TR composites by 127, 37, and 12%, respectively, compared to the 10T composite. The flexural strength of the 5:5TR hybrid composite increased by 120%, and that of the 3:7TR and 7:3TR composites increased by 83% against the 10R composite. The 3:7TR hybrid composite showed the best mechanical properties.

Armadillo shell-inspired carbon nanotubes-epoxy composites developed using 3D printing for electromagnetic interference shielding

Armadillo shell-inspired carbon nanotubes-epoxy composites developed using 3D printing for electromagnetic interference shielding

Covalently interconnected carbon nanotubes network enhancing thermal conductivity of EP-based composite

The miniaturization of integrated circuits promotes the rapid rise of polymer-based carbon nanotubes (CNTs) thermal conductive composites. However, the unordered arrangement structure and interfacial thermal resistance of CNTs become important obstacles affecting their application. The directional orientation driven of CNTs by external force and the “bridge” between CNTs constructed via covalent bonding could solve these issues. Herein, the freeze-casting orientation configuration and new CNTs grew in situ by ZIF-67 constructed the hierarchical structure of CNTs in epoxy resin (EP)-based composites. The composites with directional networks of interlinked CNTs achieve an out-plane thermal conductivity value (κ⊥) of 0.98 W m−1 K−1 at filler loading of 5.8 vol%, which is 4.85 times high than that of pure EP. More importantly, non-equilibrium molecular dynamics (NEMD) simulations validated the advantage of using covalent bonding to connect CNTs. This work provides a way for the reasonable design of polymer-based CNTs thermal conductive composites.

Multiscale interfacial enhancement of surface grown carbon nanotubes carbon fiber composites

AbstractThe interface properties between surface grown carbon nanotubes carbon fiber (CNTs‐CF) and epoxy resin were investigated by different modification methods. The X‐ray photoelectron spectrometer probations show that the pristine CNTs‐CF has very low contents of both oxygen element and active carbon element. Taking the naked carbon fiber (CF) without CNTs grown as a reference, the interfacial shear strength (IFSS) of CNTs‐CF/epoxy is only 5.6% higher. After heat treatment, chemical modification and sizing treatments, the surface chemical activity of CNTs‐CF is improved considerably. In contrast with the IFSS of standard CF/epoxy, the interfacial strength of chemical‐treated CNTs‐CF‐E1/epoxy is increased to 122.8 MPa by 29.7%. The increasing content of the epoxy active groups at the modified CNTs‐CF‐E1 surface is conducive to forming covalent bonds between the epoxy resin and the CNTs‐CF‐E1 surface particularly the activated nanotube surface. The enhancement of CNT/epoxy interface is beneficial to the over whole interface property of the composites. Hence, the compressive and torsion strength of sizing CNTs‐CF‐E1 bundle combined with epoxy resin are increased by 32.4% and 14.1%, respectively. The SEM images show the failure morphologies of different modification methods, and the enhancement mechanism of multiscale interface is further clarified. Compared with chemical treatment, heat treatment can remove the inert amorphous carbon on the CNTs‐CF fiber surface and improve the interface adhesion of CNT/epoxy and CF/epoxy, and surface sizing treatment improves the CF/epoxy interface. The enhancement mechanisms of these modified CNTs‐CFs/epoxy should be ascribed to the competition and synergetic effects of the multiscale interfaces, including CNT/CF, CNT/epoxy, and CF/epoxy.

Structural Integrity Assessment of Aligned and Non-aligned Single Walled Carbon Nanotubes in Epoxy Resin

Carbon nanotubes have gained popularity due its unique electrical and thermal properties and high strength, widely finding it application in medical and electrical field. In the presented study the single walled carbon nanotubes (SWCNT) are assumed to be aligned using a DC electric field, taking into account transportation phenomena like the rotation of tube and its polarization to form chain like structure. Authors have examined and compared the structural properties under tensile loading of aligned and non-aligned single walled carbon nanotubes SWCNT in epoxy matrix using finite element analysis. COMSOL Multiphysics has been used to model the specimens and investigate its properties. The result lays out trends and relation between various parameters and the strength of the epoxy based SWCNT composite. The study draws out result on how changes in parameters of epoxy based SWCNT composite changes its physical properties.

Design of a high-efficient metamaterial X-band absorber composed of a dielectric cylinder combined with a thin magnetic cylinder unit

High-efficient microwave absorbers (MAs) with excellent absorption performance and lightweight characteristics have important applications in the military and civil. Here, we propose a dielectric-magnetic hybrid microwave absorber composed of a lattice of dielectric cylinders combined with thin magnetic cylinders backed by a perfect electrical conductor ground plane. The dielectric material that is designed as the dielectric cylinder is based on multi-walled carbon nanotubes-epoxy (MWCNT-EP). The MWCNT-EP is prepared and the S-parameters are measured by the standard transmission/reflection (T/R) method. The thin magnetic cylinder is based on a commercial magnetic material with a height of only 1 mm. With the coaction of magnetic loss and dielectric loss, the proposed microwave absorber’s reflection loss is less than −20 dB under normal incident with a total height of 5 mm in the X-band. Besides, the dielectric-magnetic microwave absorber can maintain good absorption performance with different incident angles and polarizations. In this work, we provide a method to combine the properties of magnetic and dielectric material to construct the MA with high-efficient absorption performance.

Combined Atomic and Molecular Layer Deposition Surface Modification of Carbon Nanotubes for CNT–Epoxy Polymer Composites

Optimizing the interactions between the matrix and reinforcement components is key to attaining high-performance composite materials. Yet, balancing the reinforcing–matrix phase interactions for synthetic composites remains a great challenge. Here, a combined methodology using molecular and atomic layer deposition (M/ALD) is demonstrated for tailoring carbon nanotube (CNT) interfacial interactions, yielding high-performance-reinforced polymer composites. CNT mats are used as a model system to systematically study the molecular details as they do not involve powder processing and other aspects which obscure the understanding of molecular level effects. Noncovalent attachment of the M/ALD layer at the interface allows good wetting of the CNTs, provides an effective means for stress dissipation without compromising the CNTs’ Csp2–Csp2 network which remains intact, while introducing amine functionalities to facilitate the cross-linking polymer matrix (epoxy). M/ALD-modified CNT mat–epoxy composites showed an increase in the maximal tensile strength and toughness of up to 32 and 247%, respectively. These findings may pave the way to systematically develop high CNT loading composites as well as other nano-reinforced composite systems showing both high strength and toughness as well as numerous other desirable properties related to nanomaterial composites in general.

Insights in the enhancement of electrical conductivity and dielectric constant of epoxy-carbon nanotubes decorated with CaCO3-derived from waste eggshell hybrid composites

New insights in the development of epoxy hybrid composites using CNTs decorated with CaCO3 derived from waste eggshell (CaCO3-ESp) have been studied. The composite was produced by the solution stirring method. The dielectric constant, electrical conductivity, and morphology of the samples were determined. The dielectric constant and electrical conductivity were enhanced after the modification of the CNTs with CaCO3-ESp. The high electrical conductivity and dielectric constant obtained were attributed to the high electron mobility of CaCO3-ESp-CNTs, which helps to enhance the conductivity of the epoxy. It was found that used eggshells can be used to make sure that CNTs are spread out well when making conductive polymers for isotropic conductive adhesives, assemblies, and packaging for electronics.

Interphase elastic properties of carbon nanotube-epoxy composites and their application in multiscale analysis

A multiscale framework was developed to predict the elastic properties of carbon nanotube (CNT)–epoxy composites. The interfacial vacuum layer between the CNTs and epoxy was equivalent to transversely isotropic elastomer. The elastic constants were calibrated based on the interaction energy density in the molecular dynamics simulations; the results exhibited significant differences between these constants. The out-of-plane shear modulus (46.64 MPa) is four orders of magnitude smaller than the in-plane Young’s modulus (362.68 GPa). Subsequently, representative volume elements containing transversely isotropic interphases were developed using the finite element method and analysed comparatively to models without interphases. The results indicated that their difference in the Young’s modulus enhancement ratio was sensitive to the CNT aspect ratio. The enhancement ratio of the model containing the interphase was lower when the CNT aspect ratio exceeded a certain value. This difference increased with increasing CNT aspect ratio and was significant at high CNT aspect ratios (7.35 % when the aspect ratio reached 30). In addition, shear-lag analysis indicated that the interphase increased the interfacial load transfer length. This framework provides efficient interfacial simulations, giving a more accurate prediction of bulk elastic properties and can be extended to a wider range of nanocomposites.

Multiscale analysis method and experiments for the fracture toughness optimization analysis of carbon nanotube-epoxy composites

To better understand the facture mechanics and optimize the fracture toughness of carbon nanotube (CNT)-epoxy composites, a multiscale analysis method was established in this paper. The multiscale analysis method includes three scales: (1) at the microscale, an interfacial model was established based on the Cauchy-Born rule to deduce the relationship between the interfacial stress tensor and CC bond vector; (2) at the mesoscale, the transition condition of the failure mode from the CNT pullout to CNT fracture was established based on the shear-lag theory. And the relationships between the pulling force and CNT pullout displacement were given corresponding to these two failure modes; (3) at the macroscale, the analytical solution of fracture toughness increment was given to conduct the fracture toughness optimization analysis. By validating this method by the experiment, we found that the optimal CC bonds volume density and interfacial length are reached under the transition condition of the failure mode from the CNT pullout to CNT fracture. At last, we proposed a method to approximately estimate the optimal CC bonds volume density and CNT length.

Real-Time Emission and Exposure Measurements of Multi-walled Carbon Nanotubes during Production, Power Sawing, and Testing of Epoxy-Based Nanocomposites.

ObjectivesThe use of manufactured nanomaterials is increasing globally. Although multi-walled carbon nanotubes (CNTs) are used in a wide range of applications, only limited data are available on emissions and exposures during CNT composite production. No exposure data using portable aethalometers in the personal breathing zone (PBZ) to monitor occupational exposure to CNTs have yet been published. The aim of this study was to characterize emissions of and exposures to CNTs during CNT composite production, sawing, and shear testing. We also investigated whether real-time aethalometer measurements of equivalent black carbon (eBC) could be used as a proxy filter sampling of elemental carbon (EC). The presence of CNTs as surface contamination in the production facility was monitored since this could contribute to airborne exposure.MethodsDuring CNT composite production in an industrial setting including both chemical and manufacturing laboratories, different work tasks (WTs) were studied with a combination of direct-reading instruments (aethalometer, aerodynamic particle sizer, condensation particle counter) and filter-based methods. Measurements were performed to monitor concentrations in the emission zone (EZ), PBZ, and background zone. The filter samples were analysed for EC and fibre concentration of CNTs using scanning electron microscopy (SEM). Additionally, surfaces in the facility were tape sampled for monitoring of CNT contamination, and analysed with SEM.ResultsClear eBC peaks were observed in the PBZ during several WTs, most clearly during open handling of CNT powder. Power sawing emitted the highest particle number concentration in the EZ of both nanoparticles and coarse particles, but no individual airborne CNTs, agglomerates, or aggregates were detected. Airborne CNTs were identified, for example, in a filter sample collected in the PBZ of a worker during mixing of CNT epoxy. The airborne CNT particles were large agglomerates which looked like porous balls in the SEM images. Significant EC exposures were found in the inhalable fraction while all respirable fractions of EC were below detection. The highest inhalable EC concentrations were detected during the composite production. No significant correlation was found between inhalable EC and eBC, most likely due to losses of large EC containing particles in the sampling lines and inside the eBC monitor. In total, 39 tape samples were collected. Surface contamination of CNTs was detected on eight surfaces in the chemical and manufacturing laboratories, mainly in the near-field zone. Elongated CNT-like features were detected in the sawdust after sawing of CNT composite.ConclusionsCharacterization of a workplace producing CNT composite showed that open handling of the CNT powder during weighing and mixing of CNT powder material generated the highest particle emissions and exposures. The portable direct-reading aethalometer provided time-resolved eBC exposure data with complementary information to time-integrated EC filter samples by linking peak exposures to specific WTs. Based on the results it was not possible to conclude that eBC is a good proxy of EC. Surface contamination of CNTs was detected on several surfaces in the near-field zone in the facility. This contamination could potentially be resuspended into the workplace air, and may cause secondary inhalation exposure.