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Abstract The anticorrosive and mechanical properties of carbon nanotubes (CNTs) in epoxy resin (EP) coatings have been improved by the integration of molybdenum disulfide (Mo[S.sub.2]) and 3-aminopropyltrimethoxysilane (APTMS) for surface [...]

In the present work, by considering the aggregation effect of single-walled carbon nanotubes (SWCNT), the nonlinear vibration of functionally graded (FG) nanocomposite sandwich Timoshenko beams resting on Pasternak foundation are presented. The material properties of the FG nanocomposite sandwich beam are estimated using the Eshelby-Mori-Tanaka approach and differential quadrature method (DQM) is used to obtain natural frequency. The nonlinear governing equations and boundary conditions are derived using the Hamilton principle and von Karman geometric nonlinearity. The higher order nonlinear governing equations and boundary conditions are calculated using the Hamilton principle. A direct iterative method is employed to determine the nonlinear frequencies and mode shapes of the beams. It is shown that the mechanical properties and therefore vibration of functionally graded carbon nanotube reinforced (FG-CNTR) sandwich beams are severely affected by CNTs aggregation. A detailed parametric study is carried out to investigate the influences of Winkler foundation modulus, shear elastic foundation modulus, length to span ratio, thicknesses of face sheets on the nonlinear vibration of the structure., INTRODUCTION Over the past few years, there has been an ever-increasing interest in the synthesis, characterization, functionalization, molecular modeling, and design of nanocomposite materials. The outstanding and exceptional mechanical, electrical, [...]

In this work, the [beta]-nucleated isotactic polypropylene (iPP)/ ethylene-octene copolymer (POE) blends demonstrated greatly enhanced impact toughness by adding traces of carbon nanotubes (CNTs) (only 0.05 wt%). When the POE content was 30 wt%, the impact strength of [beta]-nucleated iPP/POE blends with CNTs was as high as 51.7 kJ/[m.sup.2], about 5.6 kJ/[m.sup.2] higher than [beta]-nucleated iPP/POE blends, 15.2 kJ/[m.sup.2] higher than CNTs-filled iPP/POE blends, and almost 19 times of pure iPP sample. This significantly improved impact toughness was considered to be attributed to the shear yielding and multiple-crazing, originating from the presence of abundant [beta]-crystals in the iPP matrix, the enhanced mobility of the molecular chains in the confined amorphous region of iPP lamellae and the homogenous distribution of POE dispersed phase with a small size, indicating the synergistic effect of CNTs, [beta]-nucleating agent and POE on the toughness of iPP., INTRODUCTION As a general plastic, isotactic polypropylene (iPP) is widely used in our daily life from common packaging and textile products to components in cutting-edge automobiles and aircraft, due to [...]

In this study, carbon nanotubes reinforced polyoxymethylene with different filler loadings was joined by using linear vibration welding technique. The tensile properties of vibration welded polyoxymethylene nanocomposites with different carbon nanotube contents were studied as functions of filler loading and weld pressure. The results showed that the addition of carbon nanotubes into polyoxymethylene slightly improved the matrix tensile strength and pronounced decreased the ductility of pure polyoxymethylene. Interestingly, the weld strength of the nanocomposites was also higher than the polymer matrix strength even at high weld pressure of 2 MPa. Possible reasons for this high weld strength are discussed based on the morphological investigations., INTRODUCTION Due to their outstanding mechanical properties with low density and high thermal as well as electrical conductivity, carbon nanotubes are used as functional fillers in polymer-based composites for a [...]

Multi-walled carbon nanotubes (MWCNTs), surfacetreated via chemical functionalization, i.e., oxidation and amidation, were used to reinforce diglycidylether of bisphenol F (DGEBF) epoxy resin. The effects of the functionalization on the dispersion stability, rheological properties, and fracture toughness of DGEBF/MWCNT composites were investigated. The dispersion homogeneity of the MWCNTs in the epoxy matrix improved after functionalization. In addition, isothermal rheology measurements revealed that the DGEBF/dodecyl aminefunctionalized MWCNT (D-MWCNT) composite had a longer gel time and higher activation energy of cross-linking than the DGEBF/acid-treated MWCNT (A-MWCNT) composite. The fracture toughness of the former was also significantly higher than that of the latter; this resulted from the relatively high dispersion stability of the D-MWCNTs in the epoxy matrix, owing to the presence of alkyl groups on the D-MWCNT surface. POLYM. ENG. SCI., 55:2676-2682, 2015. [C] 2015 Society of Plastics Engineers, INTRODUCTION Owing to their extraordinary mechanical, thermal, and electrical properties, carbon nanotubes (CNTs) have been used extensively in polymer composites since their discovery by Iijima in 1991. These outstanding electrical [...]

Polyacrylonitrile (PAN) and PAN/carbon nanotube (PAN/ CNT) fibers were manufactured through dry-jet wet spinning and gel spinning. Fiber coagulation occurred in a solvent-free or solvent/nonsolvent coagulation bath mixture with temperatures ranging from -50 to 25°C. The effect of fiber processing conditions was studied to understand their effect on the as-spun fiber cross-sectional shape, as well as the as-spun fiber morphology. Increased coagulation bath temperature and a higher concentration of solvent in the coagulation bath medium resulted in more circular fibers and smoother fiber surface. as-spun fibers were then drawn to investigate the relationship between as-spun fiber processing conditions and the drawn precursor fiber structure and mechanical properties. PAN precursor fiber tows were then stabilized and carbonized in a continuous process for the manufacture of PAN based carbon fibers. Carbon fibers with tensile strengths as high as 5.8 GPa and tensile modulus as high as 375 GPa were produced. The highest strength PAN based carbon fibers were manufactured from as-spun fibers with an irregular cross-sectional shape produced using a -50 C methanol coagulation bath, and exhibited a 61% increase in carbon fiber tensile strength as compared to the carbon fibers manufactured with a circular cross-section. POLYM. ENG. SCI., 55:2603-2614, 2015., INTRODUCTION Gel spinning has been used for the production of polyethylene [1], poly(vinyl alcohol) [2], and PAN [3] fibers, as well as their nanocomposite counterparts [4-8]. Advantages associated with gel [...]

In a systematic manner, the roles of MWNTs as filler and styrene acrylonitrile copolymer-graft-maleic anhydride (SAN-MA) as compatibilizer, individually and together, on dynamic-mechanical behavior of polycarbonate (PC)-rich/ acrylonitrile butadiene styrene terpolymer (ABS) blend were studied. The investigations were performed using small-scale mixing in a one-step procedure with a fixed MWNTs content of 0.75 wt% and a blend composition of PC/ABS = 70/30 w/w. PC/SAN blends and nanocomposites as simpler model system for PC/ABS were also studied to reveal the role of the rubbery polybutadiene (PB) fraction. It is found that the tendency of MWNTs to localize within the PC component in compatibilized PC/ABS was lower than in compatibilized PC/SAN blends. Dynamic mechanical analysis (DMA) revealed the dual role of SAN-MA as blend compatibilizer and also promoter of MWNTs migration towards PC, where SAN-MA to MWNTs weight ratio varied between 1 and 4. At the compatibilizer/MWNTs weight ratio of 1, MWNTs localized in PC component of the blends whereas increasing the compatibilizer/MWNTs ratio to 4 led to migration of MWNTs toward SAN or ABS component. In DMA studies, loss modulus normalization of the nanocomposites revealed the coexistence of mobilized and immobilized regions within the nanocomposite structure, as a result of MWNTs and compatibilizer loading., INTRODUCTION Fillers play an essential role to adjust the polymers' advantageous characteristics to reach the property balance needed for certain applications. It is expected that high aspect ratio as well [...]

The effect of montmorillonite and shear stress on the orientation of single walled carbon nanotubes and properties of SWCNT/MMT/polypropylene composite was investigated. The effect of functionalization of SWCNT on the orientation was also investigated. Polarized Raman spectroscopy was used to analyze the orientation of the SWCNTs. Orientation of SWCNTs was dependent on the experienced shear stress and functionalization of SWCNTs. The addition of MMT also improved the orientation of functionalized SWCNTs, while its effect was not significant for pristine SWCNTs. The existence of critical shear stress was observed for the orientation of the SWCNTs and the orientation of SWCNTs was found to occur more efficiently above this critical shear stress. Melt viscosity and heat of fusion data also confirmed that the addition of MMT-induced improved orientation and dispersion of SWCNTs, especially for functionalized SWCNTs., INTRODUCTION Carbon nanotubes (CNTs) have garnered attention as fillers due to their superior electrical and mechanical properties. CNTs, however, tend to agglomerate due to strong van der Waals force interactions, [...]

Different micromechanical models which account for the presence of dispersed and agglomerated nanofillers, specifically carbon nanotubes (CNTs) and cellulose nanowhiskers (CWs), in a polymeric matrix and consider the effect of a percolation threshold on the elastic modulus of the composite are derived and compared. We demonstrate that the critical filler volume fraction where a percolating network is forming marks a 'turning point' in the reinforcement efficiency. The suitability of these models is verified by comparing simulated values with experimental data from literature. The results show that the models are able to predict mechanical properties over a wide range of testing conditions. POLYM. ENG. Sd., 53:882-887, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Nanocomposites are a class of composites in which one of the dimensions of the reinforcement phase is in the range of 1-100 nm. Because of the filler nanometer size [...]

The effects of carbon nanotube (CNT) inclusion on cyclic fatigue behavior and the residual mechanical properties of epoxy composites after different degrees of fatigue have been studied. Tension-tension cyclic fatigue tests were conducted at various load levels (25-50 MPa) to establish the relationship between stress and the number of cycles to failure (S-N curves). The residual strength and modulus were measured after loading at 30 MPa for 5000, 15,000, and 25,000 cycles. The incorporation of a small amount of CNTs increased the fatigue life of epoxy in the high-cycle, low-stress-amplitude regime by 1550%. Micrographs indicate the key mechanisms for enhancement in fatigue life such as CNT crack-bridging and pullout. POLYM. ENG. SCI., 52:1882-1887, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Because of the outstanding mechanical and physical properties and large specific surface area of carbon nanotubes (CNTs), CNT-based composites are expected to show significantly improved mechanical performance, when compared [...]

Viscoelasticity describes the ability of a material to possess both elasticity and viscosity. Viscoelastic materials, such as rubbers, possess a limited operational temperature range (for example, for silicone rubber it is -55[degrees] to 300[degrees]C), above which the material breaks down and below which the material undergoes a glass transition and hardens. We created a viscoelastic material composed from a random network of long interconnected carbon nanotubes that exhibited an operational temperature range from -196[degrees] to 1000[degrees]C. The storage and loss moduli, frequency stability, reversible deformation level, and fatigue resistance were invariant from -140[degrees] to 600[degrees]C. We interpret that the thermal stability stems from energy dissipation through the zipping and unzipping of carbon nanotubes at contacts. 10.1126/science.1194865

Based on the finite-deformation shell theory for carbon nanotubes established from the interatomic potential and the continuum model for van der Waals (vdW) interactions, we have studied the buckling of double-walled carbon nanotubes subjected to compression or torsion. Prior to buckling, the vdW interactions have essentially no effect on the deformation of the double-walled carbon nanotube. The critical buckling strain of the double-wall carbon nanotubes is always between those for the inner wall and for the outer wall which means that the vdW interaction decelerates buckling of one wall at the expenses of accelerating the buckle of the other wall. [DOI: 10.1115/1.4001286] Keywords: shell theory, carbon nanotube, interatomic potential, van der Waals interactions, buckling

In this paper, a more refined pressure distribution expression is derived to describe the van der Waals (vdW) interaction between any two tubes of a multiwalled carbon nanotube (MWCNT). Based on this new vdW force expression, a continuum cylindrical shell model is established for the buckling and post-buckling analysis of MWCNTs. The buckling and post-buckling responses are simulated for MWCNTs with various sizes to examine the consequences of ignoring the nonlinear term in the Taylor expansion of vdW force function. By comparing the results furnished by the commonly used linear vdW force model and the present nonlinear vdW force model, it is found that the buckling responses before the critical buckling strain are almost the same. Thus, the simple linear vdW force model suffices for the calculation of buckling loads. However, the post-buckling responses simulated from present nonlinear vdW force model are significantly lower than those given by the linear vdW force model. This indicates that the present nonlinear vdW force model must be used when considering the post-buckling responses. [DOI: 10.1115/1.4001859]

The objective of this paper is to understand through parametric studies the effect of microstructural parameters, viz., the carbon nanotube (CNT) orientation with respect to the cutting direction, CNT loading, and level of dispersion within the matrix on the machinability of aligned CNT composites. To this end, a microstructure-based finite element machining model is used to simulate microstructures containing 1.5% and 6% by weight of CNTs. Microstructures with both uniform and nonuniform dispersions of CNTs are simulated. For each of these cases, CNTs having orientations of 0 deg, 45 deg, 90 deg, and 135 deg to the cutting direction are studied. The machining simulations were conducted using a positive rake tool Chip morphology, cutting forces, surface roughness, and surface/subsurface damages are the machinability measures used for comparison. The results of the parametric studies demonstrate that the CNT orientation, loading, and level of dispersion all play a critical role in dictating the machining response of aligned composites. The results further indicate that the surface morphology of the machined surface can be harnessed to produce the next generation of microfluidic devices. This application demonstrates the feasibility of designing the microstructure of CNT composites by taking into account both their engineering functionality and machinability. [DOI: 10.1115/1.4002495] Keywords: aligned CNT composites, micromachining, FEM models

This paper presents an investigation on the dynamic instability of cantilevered nanorods/nanotubes subjected to an end follower force. Eringen's nonlocal elasticity theory is employed to allow for the small length scale effect in the considered dynamic instability problem. The general solution for the governing differential equation is obtained and the dynamic instability characteristic equation is derived by applying the boundary conditions. Exact critical load factors are obtained. These nonlocal solutions are compared with the classical local solutions to assess the sensitivity of the small length scale effect on the critical load factors and flutter mode shapes. It is found that the small length scale effect decreases the critical load and the corresponding frequency parameters as well as reduces the severity of the double-curvature flutter mode shape. DOI: 10.1061/(ASCE)EM.1943-7889.0000135 CE Database subject headings: Dynamic stability; Nanotechnology; Rods; Elasticity; Flutter. Author keywords: Dynamic stability; Follower force; Nanorods/nanotubes; Nonlocal beam theory.

Buckling and post-buckling analysis is presented for axially compressed double-walled carbon nanotubes (CNTs) embedded in an elastic matrix in thermal environments. The double-walled carbon nanotube is modeled as a nonlocal shear deformable cylindrical shell which contains small scale effects and van der Waals interaction forces. The surrounding elastic medium is modeled as a tensionless Pasternak foundation. The post-buckling analysis is based on a higher order shear deformation shell theory with the yon Karman--Donnell-type of kinematic nonlinearity. The thermal effects are also included and the material properties are assumed to be temperature-dependent and are obtained from molecular dynamics (MD) simulations. The nonlinear prebuckling deformations of the shell and the initial local point defect, which is simulated as a dimple on the tube wall, are both taken into account. A singular perturbation technique is employed to determine the post-buckling response of the tubes and an iterative scheme is developed to obtain numerical results without using any assumption on the shape of the contact region between the tube and the elastic medium. The small scale parameter [e.sub.o]a is estimated by matching the buckling loads of CNTs observed from the MD simulation results with the numerical results obtained from the nonlocal shear deformable shell model. Numerical solutions are presented to show the post-buckling behavior of CNTs surrounded by an elastic medium of conventional and tensionless Pasternak foundations. The results show that buckling and post-buckling behavior of CNTs is very sensitive to the small scale parameter [e.sub.o]a. The results reveal that the unilateral constraint has a significant effect on the post-buckling response of CNTs when the foundation stiffness is sufficiently large. [DOI: 10.1115/1.4000910] Keywords: buckling, nanotube, nonlocal shell model, higher order shear deformable shell theory, temperature-dependent properties, initial point defects

Nanoelectromechanical resonators have potential applications in sensing, cooling, and mechanical signal processing. An important parameter in these systems is the strength of coupling the resonator motion to charge transport through the device. We investigated the mechanical oscillations of a suspended single-walled carbon nanotube that also acts as a single-electron transistor. The coupling of the mechanical and the charge degrees of freedom is strikingly strong as well as widely tunable (the associated damping rate is ~3 x [10.sup.6] Hz). In particular, the coupling is strong enough to drive the oscillations in the nonlinear regime.

By relating nanotechnology to soft condensed matter, understanding the mechanics and dynamics of single-walled carbon nanotubes (SWCNTs) in fluids is crucial for both fundamental and applied science. Here, we study the Brownian bending dynamics of individual chirality-assigned SWCNTs in water by fluorescence microscopy. The bending stiffness scales as the cube of the nanotube diameter and the shape relaxation times agree with the semiflexible chain model. This suggests that SWCNTs may be the archetypal semiflexible filaments, highly suited to act as nanoprobes in complex fluids or biological systems. actin | microrheology | semiflexible filaments and polymers | stochastic dynamics | nanomechanics

Free vibrations of a double-walled carbon nanotube (DWNT) are studied. The inner and outer carbon nanotubes are modeled as two individual elastic beams interacting each other by van der Waals forces. An original method is proposed to calculate the first seven order resonant frequencies and relative vibrational modes. Detailed results are demonstrated for DWNTs according to the different boundary conditions between inner and outer tubes, such as fixed-free, canthever-free, fixed-simple and fixed-fixed (reduced form) supported ends. Our results indicate that there is a special invariable frequency for a DWNT that is not affected by different combinations of boundary conditions. All vibrational modes of the DWNT must be coaxial when the resonant frequency is smaller than this frequency. Some noncoaxial vibrations will occur when their resonant frequencies exceed the frequency. Especially, the first noncoaxial resonant frequency is still invariable for. all different boundary conditions. A change of resonant frequency for various lengths of DWNTs is discussed in detail. In addition, our model predicts a new coaxialnoncoaxial vibrational mode in fixed-simple supports for inner and outer tubes of a DWNT. [DOI: 10.1115/1.2793133] Keywords: carbon nanotube, vibration, resonant frequency, vibrational mode, boundary condition

A phase diagram of water in single-walled carbon nanotubes at atmospheric pressure is proposed, which summarizes ice structures and their melting points as a function of the tube diameter up to 1.7 nm. The investigation is based on extensive molecular dynamics simulations over numerous thermodynamic states on the temperature-diameter plane. Spontaneous freezing of water in the simulations and the analysis of ice structures at 0 K suggest that there exist at least nine ice phases in the cylindrical space, including those reported by x-ray diffraction studies and those unreported by simulation or experiment. Each ice has a structure that maximizes the number of hydrogen bonds under the cylindrical confinement. The results show that the melting curve has many local maxima, each corresponding to the highest melting point for each ice form. The global maximum in the melting curve is located at [approximately or equal to] 11 [Angstrom], where water freezes in a square ice nanotube. ice | nanopore | melting point

An analytical electron density of states (DOS) is derived for zigzag and armchair single-wall carbon nanotubes (CNTs). The effective mass and equilibrium carrier densities have enabled an accurate analytical description of transport and electrostatics in nondegenerate CNT devices.

In this paper, the vibrational behavior of the multiwalled carbon nanotubes (MWCNTs) embedded in elastic media is investigated by a nonlocal shell model. The nonlocal shell model is formulated by considering the small length scales effects, the interaction of van der Waals forces between two adjacent tubes and the reaction from the surrounding media, and a set of governing equations of motion for the MWCNTs are accordingly derived. In contrast to the beam models in the literature, which would only predict the resonant frequencies of bending vibrational modes by taking the MWCNT as a whole beam, the current shell model can find the resonant frequencies of three modes being classified as radial, axial, and circumferential for each nanotube of a MWCNT. Big influences from the small length scales and the van der Waals' forces are observed. Among these, noteworthy is the reduction in the radial frequencies due to the van der Waals' force interaction between two adjacent nanotubes. The numerical results also show that when the spring constant ko of the surrounding elastic medium reaches a certain value, the lowest resonant frequency of the double walled carbon nanotube drops dramatically. [DOI: 10.1115/1.2722305] Keywords: vibration, multiwalled, carbon nanotubes, nonlocal shell, small length scale, van der Waals, resonant frequencies

The effect of doping of the single walled carbon nanotubes (SWCNT) on the phase formation, critical current density and the upper critical field of [MgB.sub.2] superconductor is studied. The doping is found to enhance these properties of the superconductors.

Classical molecular dynamics simulations are used to examine the mechanical responses of several different carbon nanotube systems to applied torsional loading at various temperatures. The simulations have shown that the critical buckling moment can be modified by adjusting the system temperature and through chemical functionalization of the carbon nanotube walls.

This paper employs the atomic-scale finite element method (AFEM) to study critical strain of axial buckling for carbon nanotubes (CNTs). Brenner et al. 'second-generation' empirical potential is used to model covalent bonds among atoms. The computed energy curve and critical strain for (8, 0) single-walled CNT (SWNT) agree well with molecular dynamics simulations. Both local and global buckling are achieved, two corresponding buckling zones are obtained, and the global buckling behavior of SWNT with a larger aspect ratio approaches gradually to that of a column described by Euler's formula. For double-walled CNTs with smaller ratio of length to outer diameter, the local buckling behavior can be explained by conventional shell theory very well. AFEM is an efficient way to study buckling of CNTs. [DOI: 10.1115/1.2198548]

The elastic continuum mechanics is applied to explain the wave propagation approach of single- and double-walled carbon nanotubes conveying fluids. The influence of fluid properties and the diameter of the nanotubes on the wave propagation are studied which might provide reference for potential design and application of nanoelectronics and nanodevices.

Atomic force microscope cantilevers as force-sensing elements in the nanoscale tensile testing analysis on templated carbon nanotubes inside a scanning electron microscope in a general research of cantilever beam nonlinearity under different loading conditions with analytical and finite element analysis is done. It is observed that the cantilever nonlinearity increased with increasing cantilever deflection and/or angle of loading.

Strong single-wall carbon nanotubes (SWNTs) possess very high stiffness and strength. They have potential for use to tailor the material design to reach desired mechanical properties through SWNT nanocomposites. Layer-by-layer (LBL) assembly technique is an effective method to fabricate SWNT/polyelectrolyte nanocomposite films. To determine the relationship between the constituents of the SWNT/polymer nanocomposites made by LBL technique, a method has been developed to extend the recent work by Liu and Chen (Mech. Mater., 35, pp. 69-81, 2003) for the calculation of the effective Young's modulus. The work by Liu and Chen on the mixture model is evaluated by finite element analysis of nanocomposites with SWNT volume fraction between 0% and 5%. An equivalent length coefficient is introduced and determined from finite element analysis. A formula is presented using this coefficient to determine the effective Young's modulus. It is identified that the current work can be applied to SWNT loadings between 0% and 5%, while Liu and Chen's approach is appropriate for relatively high SWNT volume fractions, close to 5%, but is not appropriate for relatively low SWNT volume fractions. The results obtained from this method are used to determine the effective Young's modulus of SWNT/polyelectrolyte nanocomposite with 4.7% SWNT loading. The material properties are characterized using both nanoindentation and tensile tests. Nanoindentation results indicate that both the in-plane relaxation modulus and the through-thickness relaxation modulus of SWNT nanocomposites are very close to each other, despite the orientation preference of the SWNTs in the nanocomposites. The steady state in-plane Young's relaxation modulus compares well with the tensile modulus, and measurement results are compared with Young's modulus determined from the method presented. [DOI: 10.1115/1.2206196]

The mechanical properties of materials and particularly the strength are greatly affected by the presence of defects; therefore, the theoretical strength ([approximately equal to] 10% of the Young's modulus) is not generally achievable for macroscopic objects. On the contrary, nanotubes, which are almost defect-free, should achieve the theoretical strength that would be reflected in superior mechanical properties. In this study, both tensile tests and buckling experiments of individual W[S.sub.2] nanotubes were carried out in a high-resolution scanning electron microscope. Tensile tests of Mo[S.sub.2] nanotubes were simulated by means of a density-functional tight-binding-based molecular dynamics scheme as well. The combination of these studies provides a microscopic picture of the nature of the fracture process, giving insight to the strength and flexibility of the W[S.sub.2] nanotubes (tensile strength of [approximately equal to] 16 GPa). Fracture analysis with recently proposed models indicates that the strength of such nanotubes is governed by a small number of defects. A fraction of the nanotubes attained the theoretical strength indicating absence of defects. inorganic | mechanical properties

A separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic, single-walled nanotubes (SWNTs) highly concentrated to 87% in a simple way. The weakly absorbed amines are easily removable after separation and the separation method is simple and convenient, suggesting a potential industrial utilization for widespread applications of SWNTs.

A method to prepare long and well-oriented SWNTs on substrates in large scale is prepared by applying a floating catalyst chemical vapor deposition (CVD) process. It is seen that SWNTs can be cut and patterned using photolithography and water plasma etching techniques, offering a way to prepare patterned SWNTs with controllable orientation, density, and lengths for various applications.

A molecular mechanical force field method is used to calculate the physical properties of macrocylce-encapsulated single-walled carbon nanotubes (SWNTs) and C60. The calculations reveal that the macrocylce-encapsulated SWNTs and C60 are more stable than free SWNTs and C60.

The effects of structural defects like single atomic vacancies, divacancies and grain boundaries on the mechanical properties of single-crystal GaN nanotubes are investigated. The results have shown that dilute single vacancies and inversion domain grain boundaries in single-crystal GaN nanotubes do not affect the Young modulus of the tubes, but the grain boundary at which the interface is normal to the axis of a nanotube might lower the Young modulus of the single-crystal GaN nanotube.

Simulations of the solid-state structures of single-wall carbon nanotubes show that once a chiral twisting of a tube is included the interactions with the nearest tubes lock it in place. Comparison with experiments and implications for the catalytic activity of these new materials are discussed.

Several scale-dependent vibration analyses are conducted to explain the impact of initial preload on the vibration characteristics exhibited by the rotating carbon nanotubes. The bending vibration of the nanotube is shown to be highly affected by the angular velocity and the nonlocal parameter.

The coupled vibration of embedded fluid-filled multiwalled carbon nanotubes (MWNTs) subject to axial load is studied by using the multiple-Euler beam model and by considering the distinctive intertube deformation of carbon MWNTs. The studies have shown that the impact of fluid coupling effect on the natural vibrating frequencies of fluid-filled MWNTs has increased as the density of the fluid has increased.

Multiple-walled carbon nanotube (CNT)-and carbon black (CB)-polymer composites are prepared by mechanical mixing with different loadings, the polymeric matrix being identical between the two series of samples, and their physical properties are measured. The results have shown that the effective permittivity spectrum of the CNT-polymer samples and their CB-based counterparts is not very sensitive to the applied stress in the range of elongation ratios.

SchrodingerEs equation is solved by using recursive Green's function algorithm self-consistently with Poisson' s equation in order to analyze the transport physics of uniaxial and torsional strained double-walled (DW) carbon nanotube (CNT) field-effect transistors (FETs) and to study their performance. The on-state cut-off frequency of DW CNTFET has shown opposite behavior to single-walled (SW) CNTFET with strain following on-state transconductance.

The fracture toughness of [Al.sub.2][O.sub.3] ceramic matrix composites is predicted by using modified MandelbrotEs fractal approach. The modified MandelbrotEs fractal approach has considered the crack propagation along the carbon nanotube (CNT) semicircumferential surface for obtaining an improved fracture toughness estimation of [Al.sub.2][O.sub.3]-CNT composite.

Buckling of a thin single-walled carbon nanotube (SWNT) bundle is described, which is partially bound on another straight free-standing SWNT bundle. The results have shown that the bulk elastic moduli of the SWNT bundles are lower than the Young's modulus of individual SWNTs and the adhesion-driven nanotube buckling has provided a new approach to quantify the elastic modulus and the binding strength of bundled nanotubes.

Molecular dynamics (MD) simulations were utilized to study the mechanical strain energy release of a bent single wall carbon nanotube (CNT) and its mechanical collision with a circular graphene sheet that is fixed at its edges. The results provide insight into the potential application of a CNT and a graphene sheet as a nanoknife and a nanocutting board, respectively, for nanocleavage processes such as sequence-specific DNA cleaving processes.