Strength Of Carbon Nanotubes Research Articles

Electrochemical hydrogen storage in EPD made porous Ni-CNT electrode

The hydrogen storage capacity of multi-wall carbon nanotubes (MWCNTs), purified and doped with nano-Nickel particles, is investigated using chronopotentiometry. Several factors such as current magnitude, effect of the number of charge and discharge cycles as well as annealing effect are studied. The X-ray Diffraction (XRD) results indicate that pickling method removes most of the catalysts. Carbon nanotubes (CNTs) are put on nickel foam of nano scale porosities by Electrophoretic deposition (EPD) method. Scanning Electron Microscopy (SEM) technique shows the surface of nickel foam plate. Deposition of nickel particles on CNTs is conducted by electroplating. In order to measure the hydrogen storage capacity, electrodes of CNT and Ni-CNT are used as working electrodes in the three-electrode system. Different results of charge and discharge for various currents in different electrodes show that Ni-CNTs have a maximum discharge capacity (3520 mAh/gr) compared to other electrodes in the optimum current of 2 mA. By increasing the number of cycles in constant current, the capacity is increased to reach a constant amount. Annealing operation leads to more strength of CNTs on the surface.

Toxicity of SWCNT Synthesized from Fermented Tapioca on SH-SY5Y Cells

The unique physical properties and strength of carbon nanotube (CNT) lend to its wide application in many fields as diverse engineering, physics and biomedicine. Biomedicine, the toxicity of CNTs was cause for concern on the application as a delivery tool for therapeutic proteins, peptides and genes in the treatment of cancer and neurodegeneration. CNTs were reported to exert adverse effects on normal neuronal function, probably due accumulation in the brain, leading to brain damage. Thus, toxicity tests of CNTs on cells would be relevant in determining potential side effects and dosage. This study was set out to evaluate the toxicity of SWCNTs derived from fermented tapioca on SH-SY5Y cells. Fermented tapioca, was a well known Malaysian local food, and was an excellent precursor for SWCNT synthesis. The raw synthesized SWCNTs were directly used to study the effect on SH-SY5Y cells. Cytotoxicity and neurotoxicity test were performed. The neurotoxicity test results showed higher cell viability compared to the cytotoxicity test. Cell viability for neurotoxicity test was above 50 % for CNT concentration ranges of 250 μg/ml and below. However cell viability decreased markedly at 500 μg/ml. The percentage of cell viability was high at 50 μg/ml and below for the first 24 h of treatment but longer treatment duration resulted in significant decrease in cell viability for all concentrations above 10 μg/ml. These findings demonstrated that CNTs were safe when used at concentration less than 10 μg/ml.

Effects of different functionalization schemes on the interfacial strength of carbon nanotube polyethylene composite

The mechanical performance of carbon nanotube (CNT) reinforced polymer composites is primarily controlled by the dispersive capacity and interfacial shear strength of CNTs in polymer matrices. CNT functionalizations will improve dispersion and strengthen interfacial bonding of CNTs in matrices. To understand the effects of different functionalization schemes on the interfacial strength of CNT-polymer composites, pullout of the covalent, noncovalent, and mixed functionalized single-walled carbon nanotube (SWCNT) from polyethylene (PE) matrix was simulated by using molecular dynamics, respectively. The results show that the SWCNT-PE interfacial shear strength is significantly improved by SWCNT functionalizations, particularly by mixed functionalization.

분산제의 종류 및 사용량에 따른 CNT 보강 시멘트 복합체의 강도변화

Sung-Jin Ha Su-Tae Kang Jong-Han LeeAbstractThis study was aimed to investigate the difference in strength of Carbon Nanotube (CNT) reinforced cement mortars with different types of surfactants and doses. In the experimental program, CTAB, SDBS and TX10 which were common surfactants adopted to improve CNTs dispersion in fabricating CNT composites in many industrial fields were included and superplasticizer which was revealed to be effective to disperse CNTs especially in CNT reinforced cementitious composites were added as well.Superplasticizer presented less strength reduction in cement mortar and more strength gain by adding CNTs among four types of surfactants. Higher dosage of superplasticizer caused lower strength of cement mortar. Adding CNTs of 0.4 wt.% or less to cementdidn’t show strength enhancement by adding CNTs but 0.8 wt.% of CNTs resulted in strengthening effect after all. Finally, a combination of 0.1 wt.% of CNTs, superplasticizer and sonication treatment could lead to strength improvement by adding CNTsin cement mortar.Keywords : Carbon Nanotube surfactant, Superplasticizer, Dispersion, Strength

Quantitative nanomechanical characterization of the van der Waals interfaces between carbon nanotubes and epoxy

Interfacial interactions between carbon nanotubes (CNTs) and polymer matrices play a critical role in the bulk mechanical performance of CNT-reinforced polymer nanocomposites, but their mechanisms remain elusive after over a decade of research. Here we present an in situ electron microscopy nanomechanical study of the non-covalent van der Waals interfaces between individual CNTs and epoxy resins in conjunction with atomistic simulations. By pulling out individual double-walled CNTs from Epon 828 films inside a high resolution electron microscope, the nanomechanical measurements capture the shear lag effect on CNT–epoxy interfaces. The maximum pull-out load of CNT–epoxy interfaces is found to be about 44% higher than the recently reported value for CNT–poly(methyl methacrylate) (PMMA) interfaces that were characterized using the same experimental technique and the same batch of dispersed CNTs. The higher interfacial strength of CNT–epoxy interfaces is partially attributed to the forced molecular deformations of aromatic rings in epoxy chains in the vicinity of the binding interface, which is supported by molecular dynamics simulations of the CNT–polymer interfacial interactions. The research findings contribute to a better understanding of the local load transfer on the tube–polymer interface and the tube’s reinforcing mechanism, and ultimately the optimal design and performance of nanotube-reinforced polymer nanocomposites.

Mechanical Properties of Hydrogenated Carbon Nanotubes (C4HNTs): A Theoretical Study

C4H nanotube (C4HNT) which is a novel kind of hydrogenated carbon nanotubes (CNTs) has gradually attracted much attention due to its unique structure and potential applications. In this work, we systematically studied the mechanical properties of C4HNT using classical molecular dynamics and molecular mechanics simulations. It is found that C4HNT can bear much greater radial pressure than CNT. For example, the collapse pressure of (10, 0) C4HNT can reach 25 GPa, which is more than 4 times that of (10, 0) CNT (6 GPa). However, hydrogenation weakens the value of Young’s modulus of CNT, and leads to the descent of axial strength of CNT. Besides, it is demonstrated that the collapse pressure of C4HNT decreases with increasing tube diameter while the Young’s modulus of C4HNT is independent of tube diameter. And the tube number, chirality, length have no effect on the axial and radial mechanical properties of C4HNT. The results show that C4HNT has much better radial mechanical properties than CNT so that C4HNT may be an ideal filler to enhance the local mechanical support of nanocomposites.

Processing, structure and flexural strength of CNT and carbon fibre reinforced, epoxy-matrix hybrid composite

Advanced materials such as continuous fibre-reinforced polymer matrix composites offer significant enhancements in variety of properties, as compared to their bulk, monolithic counterparts. These properties include primarily the tensile stress, flexural stress and fracture parameters. However, till date, there are hardly any scientific studies reported on carbon fibre (Cf) and carbon nanotube (CNT) reinforced hybrid epoxy matrix composites (unidirectional). The present work is an attempt to bring out the flexural strength properties along with a detailed investigation in the synthesis of reinforced hybrid composite. In this present study, the importance of alignment of fibre is comprehensively evaluated and reported. The results obtained are discussed in terms of material characteristics, microstructure and mode of failure under flexural (3-point bend) loading. The study reveals the material exhibiting exceptionally high strength values and declaring itself as a material with high strength to weight ratio when compared to other competing polymer matrix composites (PMCs); as a novel structural material for aeronautical and aerospace applications.

Increased Tensile Strength of Carbon Nanotube Yarns and Sheets through Chemical Modification and Electron Beam Irradiation

The inherent strength of individual carbon nanotubes (CNTs) offers considerable opportunity for the development of advanced, lightweight composite structures. Recent work in the fabrication and application of CNT forms such as yarns and sheets has addressed early nanocomposite limitations with respect to nanotube dispersion and loading and has pushed the technology toward structural composite applications. However, the high tensile strength of an individual CNT has not directly translated into that of sheets and yarns, where the bulk material strength is limited by intertube electrostatic attractions and slippage. The focus of this work was to assess postprocessing of CNT sheets and yarns to improve the macro-scale strength of these material forms. Both small-molecule functionalization and electron-beam irradiation were evaluated as means to enhance the tensile strength and Young's modulus of the bulk CNT materials. Mechanical testing revealed a 57% increase in tensile strength of CNT sheets upon functionalization compared with unfunctionalized sheets, while an additional 48% increase in tensile strength was observed when functionalized sheets were irradiated. Similarly, small-molecule functionalization increased tensile strength of yarn by up to 25%, whereas irradiation of the functionalized yarns pushed the tensile strength to 88% beyond that of the baseline yarn.

カーボンナノチューブ/炭素繊維高分子系ハイブリッド材料

The tensile properties of carbon fiber (CF) reinforced polymer matrix composites incorporating carbon nanotubes (CNT) sheet (CNT sheet/CF epoxy hybrid composites) and CNT-grafted CF (CNT-grafted CF polyimide hybrid composites) were investigated. For the CNT sheet/CF epoxy hybrid composites, the tensile modulus of hybrid composites was higher than that in the as-received state. The tensile strength of CNT sheet/polyacrylonitrile (PAN)-based CF hybrid composite was lower than that in the as-received state and the tensile strength of CNT sheet/pitch-based CF hybrid composite was higher than that in the as-received state. On the other hand, for the CNT-grafted CF polyimide hybrid composites, the tensile modulus of hybrid composites was higher than that in the as-received state and tensile strength of hybrid composites was almost similar to that in as-received state.

Compressive characteristics of single walled carbon nanotube with water interactions investigated by using molecular dynamics simulation

Abstract The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.

Estimation of mechanical properties of nanomaterials using artificial intelligence methods

Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

Nanoscopic observations for evaluating the failure process of aligned multi-walled carbon nanotube/epoxy composites

Abstract This study examined the nanoscopic damage progression of aligned multi-walled carbon nanotubes (CNT)/epoxy composites under tensile loading using transmission electron microscopy (TEM). Aligned CNT/epoxy composite films (30 μm thickness) were processed using a forest-drawn aligned CNT sheet and hot-melt prepreg method. Four film specimens, respectively subjected to tensile stress of 0 MPa, 45 MPa, 95 MPa and 110 MPa, were prepared. After tensile loading, each specimen was machined until the thickness became about 100 nm using a focused ion beam milling machine (FIB) for TEM observations. Damage of three kinds, i.e. CNT break derived from the disordered CNT structures around metallic catalyst, sword-in-sheath type CNT break, and several patterns of interfacial debonding, was observed clearly. The broken CNTs and interfacial debonding per unit area were counted from TEM photographs. Results show that broken CNTs and interface debonding increased considerably at 95–110 MPa, which suggests multiple fracture of CNT under tensile loading. The CNT length at the failure stress (110 MPa) was approximately 45 μm. Estimated values from the strength of CNTs resemble those from macroscopic stress–strain behavior.

Optimizing carbon nanotube-reinforced polysulfone ultrafiltration membranes through carboxylic acid functionalization

Multiwalled carbon nanotubes (CNTs) carboxylated to varying weight percentages were added to polysulfone membranes. The degree to which the CNTs were retained within the membrane during membrane production, operation and cleaning was examined as a function of the extent of CNT carboxylation. The effects of CNTs on polymeric membranes – increases in tensile strength, changes in surface hydrophilicity, and changes in membrane permeability – were evaluated as a function of CNT carboxylation, which was found to be coupled to CNT retention within the membrane. It was found that CNTs functionalized to a higher degree form more homogeneous polymer solutions, which lead to greater improvements in the aforementioned membrane characteristics. However, CNTs functionalized to a higher degree were also found to more-readily leave the membrane during immersion precipitation and membrane cleaning. Therefore, a balance was discovered between the benefits associated with increased dispersibility and hydrophilicity, and the disadvantages associated with decreased retention, increased leaching, and decreased strength of CNTs with greater carboxylation.

A method of mobilizing and aligning carbon nanotubes and its use in gel spinning of composite fibres

We report a method of improving the alignment of carbon nanotubes (CNTs) in a solid strand prepared from a CNT forest without dispersing and regrouping them. The use of a lubricant loosens the interconnections between the carbon nanotubes so that they can slide relative to each other and align themselves longitudinally. A highly stretchable polymer gel fibre is used as a carrier to apply the lubricant to a continuous length of the carbon nanotube strand so that the strand can be drawn uniformly and continuously by a series of drawing operations. The lubricant is then extracted to produce a highly aligned carbon nanotube reinforced polymer composite fibre that demonstrates a remarkable reinforcement effect. The CNT strength utilisation in the composite fibre is one order of magnitude greater than that in a pure carbon nanotube spun yarn.

Brittle ductile transition in carbon nanotube bundles

The superior strength and stiffness of carbon nanotubes (CNTs) make them attractive for many structural applications. Although the strength and stiffness of CNTs are extremely high, fibres of aligned CNTs have been found to date to be far weaker than the constituent CNTs. The intermolecular interactions between the CNTs in the fibres are governed by weak van der Waals forces, resulting in slippage between CNTs which occurs at tensions well below the breaking strength of the CNTs. Both theoretical and experimental studies show that by introducing chemical bonds between the CNTs increases load transfer and prevents the CNTs from slipping.

Mechanical properties of carbon nanotube reinforced Epoxy Resin composites

Overlapped have been prepared from epoxy resin material added to carbon Nanotube and percentages weight (0.1, 0.05, 0.01) % Studied the mechanical properties of the composite (bending, tensile an d hardness) has been found that the Flexural and tensile modulus of the composites were higher than the pure epoxy resin this may be due to the high mechanical strength of carbon nano tube (CNT). The hardness of the epoxy carbon Nanotube composites increased and the reason is due to increased overlap and stacking between the additives and material basis, which reduces the movement of polymer molecules leading to increased resistance to scratching material and cutting, will become more resistance to plastic deformation.

Mechanical properties of carbon nanotube reinforced Epoxy Resin composites

Overlapped have been prepared from epoxy resin material added to carbon Nanotube and percentages weight (0.1, 0.05, 0.01) % Studied the mechanical properties of the composite (bending, tensile an d hardness) has been found that the Flexural and tensile modulus of the composites were higher than the pure epoxy resin this may be due to the high mechanical strength of carbon nano tube (CNT). The hardness of the epoxy carbon Nanotube composites increased and the reason is due to increased overlap and stacking between the additives and material basis, which reduces the movement of polymer molecules leading to increased resistance to scratching material and cutting, will become more resistance to plastic deformation.

Modeling the effect of statistical variations in length and diameter of randomly oriented CNTs on the properties of CNT reinforced nanocomposites

A nano-mechanical model has been developed to calculate the tensile modulus and the tensile strength of randomly oriented short carbon nanotubes (CNTs) reinforced nanocomposites, considering the statistical variations of diameter and length of the CNTs. According to this model, the entire composite is divided into several composite segments which contain CNTs of almost the same diameter and length. The tensile modulus and tensile strength of the composite are then calculated by the weighted sum of the corresponding modulus and strength of each composite segment. The existing micro-mechanical approach for modeling the short fiber composites is modified to account for the structure of the CNTs, to calculate the modulus and the strength of each segmented CNT reinforced composites. Multi-walled CNTs with and without inter-tube bridging have been considered. Statistical variations of the diameter and length of the CNTs are modeled by a normal distribution. Simulation results show that CNTs inter-tube bridging, length and diameter affect the nanocomposites modulus and strength. Simulation results have been compared with the available experimental results and the comparison concludes that the developed model can be effectively used to predict tensile modulus and tensile strength of CNTs reinforced composites.

Effect of Multiple Stone-Wales and Vacancy Defects on the Mechanical Behavior of Carbon Nanotubes Using Molecular Dynamics

Carbon nanotubes (CNT) without any defects possess high mechanical properties. However, CNTs suffer from defects which may occur because of production inabilities, purification or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this study, mechanical properties of defective single-walled carbon nanotubes (SWCNTs) are studied. Two types of defects i.e. Stone-Wales (S-W) and Vacancy with different defect densities are considered in the present investigation. Molecular dynamics (MD) simulations are implemented to study the mechanical properties like Young's modulus, stress, and strain of armchair SWCNTs with an increasing number of S-W and vacancy defects, by varying their relative position and orientation. In the present work, calculations of fundamental mechanical properties of SWCNTs are performed using the MD simulation software Material Studio Presence of one and four vacancy defects; reduces on an average the tensile strength of CNT by 22.61% and 24.42% respectively, and tensile failure strain by 34.17% and 16.74%, respectively for different diameters. However, in case of Stone-Wales defect this reduction in strength (and strain) is only 11.33% (28.88%) and 13.16% (26.70%) for one and four defects, respectively. It can be concluded that for the same defect densities, vacancy defect deteriorates the tensile strength of nanotubes much more since such type of defect creates hole or void in the nanotubes at which the failure of the nanotubes can easily start.

Dramatic enhancements in toughness of polyimide nanocomposite via long-CNT-induced long-range creep

Super tough carbon nanotube (CNT) reinforced nanocomposites require both the unique interaction and effective stress transfer between CNTs and polymer chains. When CNT reinforced nanocomposites are stretched, the crack interfaces are usually bridged by CNTs, and energy can be absorbed during deformation before fracture and bring high toughness. However, developing super-tough CNT/polymer nanocomposites which can withstand high matrix deformation yet exploit the superior strength of CNTs is still a great challenge. In this contribution, an ultra-tough CNT/polyimide (PI) nanocomposite was fabricated by a facile in situ polymerization. Super-long vertically aligned CNTs were dispersed into N,N-dimethylacetamide, which is the feedstock for in situ PI polymerization. A long-CNT-induced three-dimensional, continuous, and heterogeneous network is formed to toughen the nanocomposites. By incorporating 0.27 wt% CNTs into a PI matrix, the tensile strength and elongation at break of the nanocomposites reached 156.4 MPa and 140%, respectively, which are 90% and 250% increased compared with the values of pristine PI. Thus, the toughness of the nanocomposites improved 470% and approached 127.4 J g−1, well exceeding state-of-the-art tough materials. The reinforcement mechanism reveals that robust tapered fibrils are formed around high-aspect-ratio CNTs to facilitate energy dissipation and enhance the energy absorbing capability. The length of CNTs and the interfacial bonding are important to initiate long-range creep and form robust heterogeneous tapered fibrils to toughen the nanocomposites. The CNT/PI composite film with high toughness, much improved electrical conductivity, as well as high thermal stability, and transparency, broadened their advanced applications in aerospace, aviation, buildings, bulletproof vests, and so on.