Mechanical Properties Of Single-walled Carbon Nanotubes Research Articles

Beam Theory of Thermal-Electro-Mechanical Coupling for Single-Wall Carbon Nanotubes.

The potential application field of single-walled carbon nanotubes (SWCNTs) is immense, due to their remarkable mechanical and electrical properties. However, their mechanical properties under combined physical fields have not attracted researchers’ attention. For the first time, the present paper proposes beam theory to model SWCNTs’ mechanical properties under combined temperature and electrostatic fields. Unlike the classical Bernoulli–Euler beam model, this new model has independent extensional stiffness and bending stiffness. Static bending, buckling, and nonlinear vibrations are investigated through the classical beam model and the new model. The results show that the classical beam model significantly underestimates the influence of temperature and electrostatic fields on the mechanical properties of SWCNTs because the model overestimates the bending stiffness. The results also suggest that it may be necessary to re-examine the accuracy of the classical beam model of SWCNTs.

Compound influence of topological defects and heteroatomic inclusions on the mechanical properties of SWCNTs

The utility of carbon nanotubes as the reinforcement agents in polymer and metal matrix composites has opened up a new avenue in the development of novel composite materials with exceptional strength and stiffness to weight ratios. Such exploitation of superior mechanical properties of carbon nanotubes depends on their inherent irregularities and structural integration. The nanotubular structures of carbon are prone to topological defects and heteroatom dopants due to the inevitable complexities in nano-synthesis. The objective of this article is to quantify the compound influence of such inherent structural irregularities (such as single vacancy defects and nanopores) and foreign atom inclusions (such as nitrogen and boron atoms) on the mechanical characteristics (like constitutive relation, fracture strength, failure strain and Young’s moduli) of single-walled carbon nanotubes (SWCNT) under various multi-physical influences (such as temperature, strain rate, diameter and chirality) based on molecular dynamics (MD) simulations. The current investigation also includes a detailed analysis on the variation in mechanical characteristics of CNTs under different spatial distributions of defects and doping.

Bernoulli-Euler beam theory of single-walled carbon nanotubes based on nonlinear stress-strain relationship

Recent experiments and density functional tight-binding (DFTB) calculations indicated the nonlinear elastic properties of graphene. However, this nonlinear stress-strain relationship has not been applied to the carbon nanotubes (CNTs) that can be viewed as graphene sheets that have been rolled tubes. In this paper, using the nonlinear stress-strain relationship of graphene, a new Bernoulli-Euler beam model of single-walled carbon nanotubes (SWCNTs) is presented for the first time. The static bending and the first-order mode forced vibrations of SWCNTs are investigated according to the new model. The results indicate that the nonlinear stress-strain relationship has a significant influence on the mechanical properties of SWCNTs.

Studying The Influence of Various Geometrical Parameters of Single-Walled Carbon Nano-Tubes of ‎Armchair Chirality Type on Its Mechanical Behavior

In the present work, the profound information on the mechanical properties of carbon nano-tubes (CNTs) were presented as an application of nano-technology in nano-materials are being most powerful in the current world. This would focuses/emphasis for designing and optimizing the CNTs based materials. Computational modeling technique was applied and developed to examine the mechanical characteristics for single-walled carbon nano-tube (SWCNT) of armchair chirality type. The atomistic based finite element method (FEM) was used to investigate the influence of various geometrical properties (diameter, wall thickness, and height-to-diameter ratio) of SWCNT armchair of chirality type on Poisson’s ratio and Young’s modulus values. Atomistic based finite element modeling was successfully developed and explored the mechanical behaviour of SWCNT exactly. The results were shown that the investigated geometrical parameters had much influenced on the mechanical properties of SWCNTs.

Ultralow voltage operation of biologically assembled all carbon nanotube nanomesh transistors with ion-gel gate dielectrics

The demonstration of field-effect transistors (FETs) based entirely on single-walled carbon nanotubes (SWNTs) would enable the fabrication of high-on-current, flexible, transparent and stretchable devices owing to the excellent electrical, optical, and mechanical properties of SWNTs. Fabricating all-SWNT-based FETs via simple solution process, at room temperature and without using lithography and vacuum process could further broaden the applicability of all-SWNT-FETs. In this work, we report on biologically assembled all SWNT-based transistors and demonstrate that ion-gel-gated network structures of unsorted SWNTs assembled using a biological template material enabled operation of SWNT-based transistors at a very low voltage. The compatibility of the biologically assembled SWNT networks with ion gel dielectrics and the large capacitance of both the three-dimensional channel networks and the ion gel allowed an ultralow operation voltage. The all-SWNT-based FETs showed an Ion/Ioff value of >102, an on-current density per channel width of 2.16 × 10−4 A/mm at VDS = 0.4 V, and a field-effect hole mobility of 1.12 cm2/V · s in addition to the low operation voltage of <−0.5 V. We envision that our work suggests a solution-based simple and low-cost approach to realizing all-carbon-based FETs for low voltage operation and flexible applications.

Angle dependence of the shear behaviour of asymmetric carbon nanotubes

Asymmetric configurations of single-walled carbon nanotubes consist of a huge number of varieties compared to symmetric structures. A comprehensive characterization of all possible chiralities has been conducted in this research for the first time. In order to characterize asymmetric single-walled carbon nanotubes (SWCNTs), several finite element models have been employed to reach a logical relation between the geometry of the symmetric and asymmetric configurations and their shear modulus. Two groups of asymmetric structures have been selected to characterize asymmetric configurations. The chiral angle (θ) has been applied in this research to account for the shear behaviour of chiral configurations. The chiral angle perception has been used for a new insight of balancing between physical resemblances and shear behaviour of symmetric and asymmetric configurations. In the last section, the trend of the shear behaviour and chiral angle for asymmetric groups resulted in a general equation for predicting an asymmetric configuration by symmetric structures with high accuracy as the main novelty of the current study. This kind of characterization can be developed, not only for other mechanical properties of SWCNTs, but is also applicable for the characterization and the design of other composite nanotubes such as BN, BC3 and BC2N nanotubes.

The mechanical property of single-walled carbon nanotube under combined electromechanical loading

ABSTRACTThe mechanical properties and failure process of single-walled carbon nanotube (SWCNT) under combined electric field and tensile loading are investigated using the semi-empirical quantum mechanical method. The local and global structural deformation and variation of mechanical properties of SWCNT under different directions and intensity of external electric field are discussed systematically. It is shown that the electric field induced deformation in the radial and axial directions of the SWCNT are strongly dependent on the direction of electric field. The analysis of mechanical properties shows that the structure stiffness, tensile strength and failure strain of the SWCNT all decrease with the increase of the field intensity, which is particularly evident under the longitudinal electric field. The Young's modulus of SWCNTs vary with the tube diameter and are affected by the electric field. The increase of the length of the tubes intensifies the charge concentration at the tube ends under the electric field and lead to the decrease of mechanical properties of SWCNTs. The failure process of SWCNTs under the coupling effect of electric field and tensile loading is found to be controlled by the field strength and also affected by the electric charge accumulation.

Tensile Characterization of Single-Walled Carbon Nanotubes with Helical Structural Defects.

Recently, evidence was presented that certain single-walled carbon nanotubes (SWNTs) possess helical defective traces, exhibiting distinct cleaved lines, yet their mechanical characterization remains a challenge. On the basis of the spiral growth model of SWNTs, here we present atomic details of helical defects and investigate how the tensile behaviors of SWNTs change with their presence using molecular dynamics simulations. SWNTs have exhibited substantially lower tensile strength and strain than theoretical results obtained from a seamless tubular structure, whose physical origin cannot be explained either by any known SWNT defects so far. We find that this long-lasting puzzle could be explained by assuming helical defects in SWNTs, exhibiting excellent agreement with experimental observation. The mechanism of this tensile process is elucidated by analyzing atomic stress distribution and evolution, and the effects of the chirality and diameter of SWNTs on this phenomenon are examined based on linear elastic fracture mechanics. This work contributes significantly to our understanding of the growth mechanism, defect hierarchies, and mechanical properties of SWNTs.

Molecular dynamics analysis on tensile properties of carbon nanotubes with different cracks

Molecular dynamics simulation is employed for the axial tension of single-walled carbon nanotubes (SWCNTs) with different cracks. The cracks of SWCNTs in this study actually are the crack-like defects. AIREBO potential is used to simulate the interactions among carbon atoms. The effects of the crack length, temperature, strain rate and tube diameter on the mechanical properties of SWCNTs are studied. It is found that the failure stress and failure strain decrease with the increase of crack length. And the results show that the failure stress and failure strain are related to the applied strain rate and affected by temperature especially by lower temperature. It is also revealed that the failure stress increases with the increase in tube diameter. The deformation behaviours of SWCNTs are also obtained.

Deformation of single-walled carbon nanotubes by interaction with graphene: a first-principles study.

The interaction between single-walled carbon nanotubes (SWNTs) and graphene were studied with first-principles calculations. Both SWNTs and single-layer graphene (SLG) or double-layer graphene (DLG) display more remarkable deformations with the increase of SWNT diameter, which implies a stronger interaction between SWNTs and graphene. Besides, in DLG, deformation of the upper-layer graphene is less than in SLG. Zigzag SWNTs show stronger interactions with SLG than armchair SWNTs, whereas the order is reversed for DLG, which can be interpreted by the mechanical properties of SWNTs and graphene. Density of states and band structures were also studied, and it was found that the interaction between a SWNT and graphene is not strong enough to bring about obvious influence on the electronic structures of SWNTs.

Single-walled carbon nanotubes and nanocrystalline graphene reduce beam-induced movements in high-resolution electron cryo-microscopy of ice-embedded biological samples

For single particle electron cryo-microscopy (cryoEM), contrast loss due to beam-induced charging and specimen movement is a serious problem, as the thin films of vitreous ice spanning the holes of a holey carbon film are particularly susceptible to beam-induced movement. We demonstrate that the problem is at least partially solved by carbon nanotechnology. Doping ice-embedded samples with single-walled carbon nanotubes (SWNT) in aqueous suspension or adding nanocrystalline graphene supports, obtained by thermal conversion of cross-linked self-assembled biphenyl precursors, significantly reduces contrast loss in high-resolution cryoEM due to the excellent electrical and mechanical properties of SWNTs and graphene.

Evaluation of Mechanical Properties of Single-Walled Carbon Nanotubes

A micromechanical finite element model incorporated with molecular mechanics is employed to determine the mechanical properties of single-walled carbon nanotubes (SWCNT). The SWCNT is modelled as a space-frame structure. The bonds between the carbon atoms are simulated as beam members to carry the loads, while the carbon atoms are the joints of the members. The modified Morse potential is adopted to characterize the non-linear behavior of C-C bonds. In this work, the mechanical properties of SWCNT such as the Young’s modulus, ultimate strength and strain are investigated. To verify the proposed FE model and evaluate its performance, the effects of diameter and chirality on the mechanical properties of SWCNT are presented. It is found that both the Young’s modulus and ultimate strength of SWCNT increase monotonically with the increase of diameter. The Young’s modulus of armchair is larger than that of zigzag SWCNTs. These results are in good agreement with the existing numerical and experimental results.

Highly Organized Two- and Three-Dimensional Single-Walled Carbon Nanotube–Polymer Hybrid Architectures

Single-walled carbon nanotube (SWCNT) network architectures combined with flexible mediums (especially polymers) are strong candidates for functional flexible devices and composite structures requiring the combination of unique electronic, optical, and/or mechanical properties of SWCNTs and polymer materials. However, to build functional flexible devices with SWCNTs, it is required to have abilities to assemble and incorporate SWCNTs in desired locations, orientations, and dimensions on/inside polymer substrates. Here, we present unique two- and three-dimensional SWCNT network-polymer hybrid architectures by combining unprecedented control over growth, assembly, and transfer processes of SWCNTs. Several SWCNT architectures have been built on polymer materials ranging from two-dimensional suspended SWCNT microlines on PDMS microchannels to three-dimensional "PDMS-vertically aligned SWCNTs-PDMS" sandwich structures. Also a combined lateral SWCNT microline and vertically aligned SWCNT flexible device was demonstrated with good electrical conductivity and low junction resistance. The results reported here open the pathway for the development of SWCNT-based functional systems in various flexible device applications.

Functional Covalent Chemistry of Carbon Nanotube Surfaces

AbstractIn this Progress Report, we update covalent chemical strategies commonly used for the focused functionalization of single‐walled carbon nanotube (SWNT) surfaces. In recent years, SWNTs have been treated as legitimate nanoscale chemical reagents. Hence, herein we seek to understand, from a structural and mechanistic perspective, the breadth and types of controlled covalent reactions SWNTs can undergo in solution phase, not only at ends and defect sites but also along sidewalls. We explore advances in the formation of nanotube derivatives that essentially maintain and even enhance their performance metrics after precise chemical modification. We especially highlight molecular insights (and corresponding correlation with properties) into the binding of functional moieties onto carbon nanotube surfaces. Controllable chemical functionalization suggests that the unique optical, electronic, and mechanical properties of SWNTs can be much more readily tuned than ever before, with key implications for the generation of truly functional nanoscale working devices.

Molecular Dynamics Study of a Nanotube-Binding Amphiphilic Helical Peptide at Different Water/Hydrophobic Interfaces

Many potential applications of single-walled carbon nanotubes (SWNTs) require that they be isolated from one another. This may be accomplished through covalent or noncovalent SWNT functionalization. The noncovalent approach preserves the intrinsic electrical, optical, and mechanical properties of SWNTs and can be achieved by dispersing SWNTs in aqueous solution using surfactants, polymers, or biomacromolecules like DNA or polypeptides. The designed amphiphilic helical peptide nano-1, which contains hydrophobic valine and aromatic phenylalanine residues for interaction with SWNTs and glutamic acid and lysine residues for water solubility, has been shown to debundle and disperse SWNTs, although the details of the peptide-SWNT interactions await elucidation. Here we use fully atomistic molecular dynamics simulations to investigate the nano-1 peptide at three different water/hydrophobic interfaces: water/oil, water/graphite, and water/SWNT. The amphiphilic nature of the peptide is characterized by its secondary structure, peptide-water hydrogen bonding, and peptide-hydrophobic surface van der Waals energy. We show that nano-1 has reduced amphiphilic character at the water/oil interface because the peptide helix penetrates into the hydrophobic phase. The peptide alpha-helix cannot match its hydrophobic face to the rigid planar graphite surface without partially unfolding. In contrast, nano-1 can curve on the SWNT surface in an alpha-helical conformation to simultaneously maximize its hydrophobic contacts with the SWNT and its hydrogen bonds with water. The molecular insight into the peptide conformation at the various hydrophobic surfaces provides guidelines for future peptide design.

The effects of interfacial bonding on mechanical properties of single-walled carbonnanotube reinforced copper matrix nanocomposites

The effects of interfacial bonding on mechanical properties of single-walledcarbon nanotube reinforced copper matrix nanocomposites were investigated.The nanocomposites were fabricated by means of a powder metallurgy process,which consists of mixing carbon nanotubes with matrix powder followed byhot-pressing. The mixing process was carried out by ultrasonicating the nanotubesand copper powder in ethanol. The interfacial strength between the nanotubesand the copper matrix was improved by coating the nanotubes with nickel. Thedisplacement rate of the nanotube reinforced nanocomposites was found to increase at200 °C, whereas that of the nickel-coated nanotube reinforced nanocomposites significantlydecreased. The incorporation of carbon nanotubes and nickel-coated carbon nanotubes inthe copper matrix composites improved tribological properties compared with those of purecopper specimens.

Effect of chemical functionalization on the mechanical properties of carbon nanotubes

Carbon nanotubes (CNTs) have been proposed as ideal fibers for the manufacture of the next generation of composite materials. To ultimately increase the interaction of the CNTs with polymer matrices, researchers have attached chemical functional groups to the nanotube walls. The effects of covalent chemical attachments on the mechanical properties of single-walled CNTs are examined with classical molecular dynamics simulations. The maximum compressive (buckling) force for various functionalized and non-functionalized CNTs is calculated. It is found that covalent chemical attachments decrease the maximum buckling force by about 15% regardless of tubule helical structure or radius.