Orientation Of Nanotubes Research Articles

(Invited) Analytical Super-Resolution Microscopy Approaches for the Morphological Characterization of Carbon Nanotube Heterogeneity

The ability to determine the shape, size and orientation of fluorescent single-walled carbon nanotubes is critical for a plethora of applications. Yet the heterogeneity of the nanotube samples is often overlooked due to the lack of investigation approaches which may impact the obtained results. Although techniques such as atomic force microscopy (AFM) and transmission electron microscopy (TEM) could be used to this extent, they require heavy instrumentation and analysis, and do not necessarily allow the temporal and in situ characterization of the samples. On the other hand, super resolution microscopy (SRM) approaches can be used to determine the structure of fluorescent nano-objects with high precision while retaining the possibility to perform in situ studies. In particular, analytical SRM approaches are particularly interesting as they rely only on post-processing and do not require any specific optical component.In this context, we study the performances of three analytical SRM approaches for the determination of SWCNT shape, size and orientation. Using correlative microscopy between optical and AFM approaches this study provides an in-depth comparison of the performances of analytical SRM approaches for the morphological characterization of individual SWCNTs.B.P. Lambert et al., in preparation

Programmable Carbon Nanotube Networks: Controlling Optical Properties Through Orientation and Interaction.

The lattice geometry of natural materials and the structural geometry of artificial materials are crucial factors determining their physical properties. Most materials have predetermined geometries that lead to fixed physical characteristics. Here, the demonstration of a carbon nanotube network serves as an example of a system with controllable orientation achieving on-demand optical properties. Such a network allows programming their optical response depending on the orientation of the constituent carbon nanotubes and leads to the switching of its dielectric tensor from isotropic to anisotropic. Furthermore, it also allows for the achievement of wavelength-dispersion for their principal optical axes - a recently discovered phenomenon in van der Waals triclinic crystals. The results originate from two unique carbon nanotubes features: uniaxial anisotropy from the well-defined cylindrical geometry and the intersection interaction among individual carbon nanotubes. The findings demonstrate that shaping the relative orientations of carbon nanotubes or other quasi-one-dimensional materials of cylindrical symmetry within a network paves the way to a universal method for the creation of systems with desired optical properties.

Highly Conductive Double‐Wall Carbon Nanotube Fibers Produced by Dry‐Jet Wet Spinning

AbstractCarbon nanotube fibers (CNTFs) are considered an ideal candidate as next‐generation conducting wires due to their high conductivity and low density. However, the orientation and compaction of the nanotubes in a CNTF need to be further improved to achieve even higher conductivity and ampacity. Here the fabrication of double‐wall CNTFs (DWCNTFs) is reported by a dry‐jet wet spinning method, which significantly improves the orientation and compaction of the carbon nanotubes (CNTs). As a result, the obtained DWCNTFs have a record high electrical conductivity of 1.1 × 107 S m−1 and ampacity of 8.0 × 108 A m−2. The fibers also have a high tensile strength of 1.65 GPa and a toughness of 130.9 MJ m−3, among the highest for wet‐spun CNTFs. The DWCNTFs preserve their integrity and conductivity after more than 5000 bending cycles. Theoretical calculations indicate that in a dry‐jet wet‐spinning process, gravity promotes the orientation of the CNTs along the axial direction of the fiber.

Performance of Particle Swarm Optimization in Predicting the Orientation of π-Conjugated Molecules Inside Carbon Nanotubes Compared with Density Functional Theory Calculations.

Particle swarm optimization (PSO) was employed to obtain the global minimum of host-guest structures consisting of a triiodobenzene molecule (BzI3) inside an armchair (m,m) nanotube (BzI3@(m,m)), whose host-guest interactions are approximated by Lennard-Jones (LJ) potentials. The host-guest structures obtained using the PSO-LJ method were then compared with those obtained through dispersion-corrected density functional theory (DFT) calculations to evaluate the performance of the PSO-LJ approach in predicting the guest orientation inside a tube. When the inner space of the host tube is limited for guest encapsulation, the PSO-LJ method can reproduce the DFT results of BzI3@(m,m) in terms of the guest orientation. Conversely, in nanotubes with a sufficiently large space to allow a guest to freely move, corresponding to weak tube confinement, the PSO-LJ method yields guest orientations that are different from those obtained through DFT calculations; however, both methods obtain energetically close guest orientations. Accordingly, PSO-LJ method-assisted DFT calculations can quickly provide energetically stable guest orientations in BzI3@(m,m) in weak tube confinement, which can be ignored in DFT calculations, where a single initial geometry is typically used.

Enhancing interfacial shear strength with tailored carbon nanotube orientations: A micromechanical hierarchical model of single fiber fragmentation tests

This study explores the effects of carbon nanotube (CNT) orientation on stress transfer in carbon fiber (CF) composites using the Single Fiber Fragmentation Test (SFFT). A micromechanical hierarchical model, utilizing the Finite Element Method (FEM), is developed to analyze a CF composite with a CNT-reinforced interfacial region, encapsulated within an epoxy resin matrix. The Mori-Tanaka method is utilized to calculate the effective properties of the CNT-reinforced interfacial region of the CF, taking into account different CNT orientations and volume fractions. Scenarios involving radial, longitudinal, and random CNT orientations are considered. Moreover, the study also incorporates the nonlinear plastic behavior of the epoxy matrix. A novel analytical framework that leverages FEM to compute variables such as critical length, interfacial shear strength (IFSS), and average normal stress is proposed to accomplish it. Numerical results are compared to existing experimental data for validation. For the validation of the proposed methodology, experimental data available in the literature were used. The model predictions show that specific orientations and volume fractions of CNTs have the potential to enhance IFSS. However, the enhancement in the elastic stiffness of the interfacial region, attributed to the inclusion of CNTs, does not entirely explain the improvements in IFSS observed in the experimental studies from the literature.

Halloysite nanotubes as nano-support matrix for programming the photo/H2O dual triggered reversible gel actuator

Gel actuators are a kind of soft intelligent material that can convert external stimuli into deformations to generate mechanical responses. The development of gel actuators with advanced structures to integrate multiple responsiveness, programmability, and fast deformation ability is urgently needed. Here, we explored a poly(7-(2-methacryloyloxyethoxy)-4-methylcoumarin-co-acrylic acid-co-glycol) ternary gel network as an actuator with reprogrammable photo/H2O dual responsibilities. In such a design, [2 + 2] photodimerization and photocleavage reactions of coumarin moieties can be realized under 365 and 254 nm light irradiation, respectively, affording reversible photodriven behaviour of the gels. The abundant carboxylic acid in the backbone has the capacity to form additional crosslinks to assist and accelerate the photodriven behaviour. The incorporation and orientation of halloysite nanotubes (HNTs) in gel matrices support an axial direction force and result in a more controllable and programmable actuating behaviour. The synergistic response enables fast grasping-releasing of 5-times the weight of the object in water within 10 min by fabricating HNT-incorporated gels as a four-arm gripper.

Coaxially oriented PVDF/MWCNT nanofibers as a high‐performance piezoelectric actuator

AbstractControlling the orientation of the carbon nanotubes inside a polymer matrix essentially improves their reinforcement effect even at small loading levels, which is attractive from the processing point of view. We inform the utilization of electrospinning to produce highly aligned small‐diameter polyvinylidene fluoride (PVDF) nanofibers where the multiwalled carbon nanotube (MWCNT) are coaxially aligned inside the PVDF nanofibers. The coaxially aligned MWCNTs arrange large numbers of contact sites with the polymer chains, thereby providing enhanced interfacial interactions, resulting in the superior effect of the MWCNTs on the crystalline structure and actuator response of the PVDF at low loading levels (0.06 wt.%). An effective α‐ to β‐phase conversion occurred through the synergistic effects of the electrospinning and MWCNTs, the β‐phase content reached 94%. Also, the degree of crystallinity increased up to 50% respecting the pure nanofibers. The bending actuation of the nanofibers was analyzed as the active layer of soft piezoelectric actuators in a unimorph configuration. The well‐aligned nanofibers showed better actuator deflection than the randomly oriented nanofibers. Comparing the PVDF nanofiber‐based actuators in the literature, our actuators exhibited excellent piezoelectric performance with high potential for practical applications.Highlights Highly aligned small‐diameter PVDF/CNT nanofibers produced by electrospinning. Axially aligned CNTs induce a great piezoelectric effect at low‐loading levels. The F(β) was 94%, and the crystallinity increased by 50% at only 0.06 wt% CNTs. Well‐aligned nanofibers showed better actuator response than the random ones. The soft actuators showed a higher performance than those in the literature.

Concurrent topology optimization design for CNT orientation and CNTRC layout

In this study, the topology optimization (TO) design of carbon nanotube (CNT) orientation and material layout for carbon nanotube-reinforced composites (CNTRCs) is performed for the first time. The equivalent performance of CNTRCs is calculated by the extended easy-to-implement rule of mixtures. Then, by considering two independent angle variables, a 3-dimensional (3D) concurrent optimization model for CNT orientation and material layout is constructed. To decrease the possibility of falling into local optimal solutions, a discrete interval method is proposed to divide the search space into specific subintervals, and thus the original optimization problem is changed into material selection and subinterval angle optimization problems. In addition, different from conventional fiber-reinforced composites, CNTRCs employ nanoscale filler as reinforcement, which makes it more beneficial to achieve local material strengthening. Therefore, to decrease the possibility of local optimal solutions and achieve local structural strengthening, a concurrent TO model involving CNTRCs and isotropic materials under the volume constraint is proposed to achieve the optimal balance between structural stiffness and economy. Subsequently, the sensitivities of structural compliance with respect to design, selection, and angle variables are derived. Also, the effectiveness of the proposed method is verified by 2D and 3D examples.

Electrical Conductivity and In Situ SAXS Probing of Block Copolymer Nanocomposites Under Mechanical Stretching.

Elastomers based on block copolymers can self-organize into ordered nanoscale structures, making them attractive for use as flexible conductive nanocomposites. Understanding how ordered structures impact electrical properties is essential for practical applications. This study investigated the morphological evolution of flexible conductive elastomers based on polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) block copolymers with aligned single- or multi-wall carbon nanotubes (SWCNTs or MWCNTs) and their electrical conductivity under large deformations. Oriented nanocomposites were obtained through injection molding and characterized using two different setups: tensile testing monitored by in situ small-angle X-ray scattering (SAXS) and tensile testing with simultaneous electrical conductivity measurements. Our findings demonstrate that structural orientation significantly influences electrical conductivity, with higher conductivity in the longitudinal direction due to the preferred orientation of carbon nanotubes. Tensile testing demonstrated that carbon nanotubes accelerate the process of realignment of the ordered structure. As a consequence, higher deformations reduced the conductivity of samples with longitudinal alignment due to the disruption of percolation contacts between nanotubes, while in samples with a transverse alignment the process promoted the formation of a new conductive network, increasing electrical conductivity.

Numerical and analytical modelling of effective thermal conductivity of multi-walled carbon nanotubes polymer nanocomposites including the effect of nanotube orientation and interfacial thermal resistance

Multi-walled carbon Nanotube (MWCNT) fillers are extensively used to improve the thermomechanical properties of polymers. In this study, five different weight fractions (0%, 0.25%, 0.50%, 0.75%, and 1%) of MWCNT-polymer nanocomposites were prepared by the solution mixing technique. The thermal conductivity of MWCNT-polymer nanocomposites was investigated using the laser flash method. The closed-form solution of the modified Mori-Tanaka homogenization method was developed for the accurate estimation of the thermal conductivity of nanocomposite materials after considering the influence of interfacial thermal resistance (ITR). The finite element simulation of RVE modelling was utilized to predict the thermal conductivity of nanocomposites with and without consideration of the interfacial thermal resistance effect. A perfect bond was assumed between MWCNT and polymer for both numerical and analytical studies. The thermal conductivity results obtained from the closed-form solution of the modified Mori-Tanaka method were in good agreement with both the finite element simulation (FEM) and experimental results.

Anisotropy of epoxy acrylate with magnetic field-induced Ni-MWNTs

Abstract In this paper, epoxy acrylate/nickel-plated carbon nanotubes composites with different structural orientations (X, Z) were prepared by digital light procession 3D, and the orientation of nickel-plated carbon nanotubes in the magnetic field and its effect on the mechanical properties of the composites were systematically studied. The scanning electron microscope shows the orientation of the fiber in the magnetic field. The experimental results show that the mechanical properties and friction coefficient of the material show obvious anisotropy, but the anisotropy of wear rate is not obvious. The tensile strength of the X sample is about 18% higher than that of the Z sample when the content of nickel-plated carbon nanotubes was 0.15 wt%. The impact strength of the X sample is about 15% higher than that of the Z sample when the content of Ni-MWNTs was 0.1 wt%. The friction coefficient on the plane (X, Y) is about 20% lower than that on the plane (Y, Z) when the content of carbon nanotubes is 0.05 wt%.

Fabrication of CNTFET Simulation Using Cadence Virtuoso

In this paper, the fabrication of CNTFET with the help of simulation using cadence virtuoso is presented. The process of fabricating Carbon Nanotube Field-Effect Transistors (CNTFETs) is a sophisticated task that demands great attention to detail. To aid in the design and optimization of CNTFET fabrication processes, simulation tools are often utilized. CNTFET fabrication simulations generally involve modeling the physical and chemical processes of creating the carbon nanotube channel, as well as the device's metal contacts and other components. Simulation tools such as COMSOL Multiphysics or Lumerical are used to model the mechanical, thermal, and electrical properties of the materials involved, and to predict how they will behave during fabrication. An essential challenge in CNTFET fabrication is obtaining precise control over the nanotube placement and orientation, which can be addressed through modeling the nanotube growth and optimizing the growth parameters to achieve the desired properties. Furthermore, simulations can assist in optimizing the process parameters for depositing metal contacts on the nanotubes, which is critical for achieving good device performance. Overall, simulation tools play a vital role in the CNTFET fabrication process, enabling researchers to optimize the device design and fabrication parameters for improved performance and yield. The work done & presented in this paper is the result of the mini-project work that has been done by the first sem engineering students of the college and as such there is little novelty in it and the references are being taken from various sources from the internet, the paper is being written by the students to test their writing skills in the starting of their engineering career and also to test the presentation skills during their mini-project presentation. The work done & presented in this paper is the report of the assignment / alternate assessment tool as a part and parcel of the academic assignment of the first year subject on nanotechnology & IoT.

Excluded Volume Effect on the Extensional Rheology of Carbon Nanotubes: A Mesoscopic Theory

We present a mesoscopic theory of the extensional rheology of liquid crystalline carbon nanotubes (CNTs). We implement the mesoscopic Leslie–Ericksen theory, considering the repulsive excluded volume potential acting in the direction opposite to the Frank elastic potential. Given the volume fraction, diameter, and length of the CNTs, our model predicts the extensional viscosity. The liquid crystalline phase of the CNTs exhibited extensional thinning behavior. In our theory, the rotational relaxation time is proportional to the reciprocal excluded volume, particularly for long CNTs with waviness. Our model also predicts the minimum draw ratio, below which the nanotube orientation cannot reach the target orientation. The existence of a minimum draw ratio is due to the large excluded volume potential of the long CNTs.

Facile alignment estimation in carbon nanotube films using image processing

Whether a macroscopic assembly of carbon nanotubes can exhibit the one-dimensional properties expected from individual nanotubes critically depends on how well the nanotubes are aligned inside the assembly. Therefore, a simple and accurate method for assessing the degree of alignment is desired for the rapid characterization of carbon nanotube films and fibers. Here, we present an end-to-end solution for determining the global and local spatial orientation of carbon nanotubes in films within a short amount of time using a fast, precise, and economical approach based on an image processing method applied to scanning electron microscopy images. We first use Laplacian edge enhancement filtering for improving the appearance of edge regions, which is followed by image partitioning into multiple blocks to capture the nanoscale orientation characteristics and total variation-based image decomposition of these image blocks. We then perform a 2D-fast Fourier transform on the image decomposed textural components of these edge-enhanced image blocks to determine the orientation distribution, which is utilized to estimate the 2D nematic order parameter. To show the effectiveness of our method, we corroborated our results against results obtained with other state-of-the-art image processing and experimental techniques.

Investigation of mechanical behavior of carbon nanotube-reinforced magnesium composite

Metal matrix-based carbon nanotube (CNT) composites are being extensively explored because of their superior mechanical properties. Among metals, magnesium due to its low density and low melting point is widely used in making light weight composite material. Addition of small amount CNTs in magnesium matrix can produce high strength, light weight material. In this work, mechanical properties of CNT/Magnesium composites are being investigated. Three-dimensional representative volume element is extracted from the composite, for the analysis. Four different types of models are constructed, each made of square shape consisting of 16 CNTs. Adequate properties of single-walled CNT/Magnesium composite are examined with RVE undergoing stretch and transverse loading conditions. The results are obtained for different percentages of CNT volume fraction in magnesium matrix. For closely simulating the properties of composite material, the interphase is developed between CNT and matrix material and random orientation of carbon nanotubes in the matrix is considered. With the insertion of 2.4% of CNTs in the magnesium matrix material, 31.64% rise in Young’s modulus is observed. The results acquired from the present analysis are validated with the rule of mixture results. The present results are observed to be in line with the experimental results from the literature.

Study on preparation and field induction mechanism of organic silicon composites based on aligned carbon nanotubes

AbstractHigh thermal conductivity materials are an urgent need for high power, microelectronic components and equipment, but are limited by low thermal conductivity of the traditional silicone materials. 4‐Cyano‐4′‐n‐octyl biphenyl (8OCB) was synthesized to modify carbon nanotubes, and silicone was used as the matrix. In the curing process of the composite, an electric field was applied and the liquid crystal induced the orientation of carbon nanotubes in the direction of 8OCB liquid crystal. The morphology, structure and properties of modified carbon nanotubes and composites were characterized by Fourier transform infrared spectroscopy, polarized microscopy, transmission electron microscopy, thermal conductivity, and so on. The 8OCB liquid crystal can improve the dispersion of carbon nanotubes in silicone composites. When the mass fraction of multiwalled carbon nanotubes (MWCNTs) was 11 wt%, the thermal conductivity of 8OCB‐MWCNTs/silicone composite after electric field was 2.39 W/(m K), which is 6.4 times that of MWCNTs/silicone composite after electric field and 15.5 times that of pure silicone matrix. A method to obtain highly ordered filled thermal conductive materials by applying an electric field to induce the orientation of carbon nanotubes is demonstrated.

Computer and experimental study of field-induced conductivity modulation in liquid crystal–carbon nanotubes system

In this study, the possibility of percolation system conductivity control by the applied electric field has been researched based on computer simulation and experimental measurements of electrical characteristics of liquid crystal–carbon nanotubes nanocomposite. It was found that electrical resistance of obtained nanocomposites decreases with increasing nanotube concentration. It is shown that the applied voltage reduces the resistance of the nanocomposite, which is likely associated with the change in the spatial orientation of nanotubes. Nanocomposites with 2–4% nanotube content show the maximum field-controlled relative change in resistance. The effect of concentration and orientation of the nanotubes on the percolation processes in the carbon nanotube system has been studied by computer simulations. The change in the percolation probability was revealed when limiting nanotube orientation angles that are controlled by the electrical field.

Finite element predictions on vibrations of laminated composite plates incorporating the random orientation, agglomeration, and waviness of carbon nanotubes

Finite element predictions on vibrations of laminated composite plates incorporating the random orientation, agglomeration, and waviness of carbon nanotubes

Detecting Carbon Nanotube Orientation with Topological Analysis of Scanning Electron Micrographs.

As the aerospace industry is increasingly demanding stronger, lightweight materials, ultra-strong carbon nanotube (CNT) composites with highly aligned CNT network structures could be the answer. In this work, a novel methodology applying topological data analysis (TDA) to scanning electron microscope (SEM) images was developed to detect CNT orientation. The CNT bundle extensions in certain directions were summarized algebraically and expressed as visible barcodes. The barcodes were then calculated and converted into the total spread function, V(X, θ), from which the alignment fraction and the preferred direction could be determined. For validation purposes, the random CNT sheets were mechanically stretched at various strain ratios ranging from 0 to 40%, and quantitative TDA was conducted based on the SEM images taken at random positions. The results showed high consistency (R2 = 0.972) compared to Herman’s orientation factors derived from polarized Raman spectroscopy and wide-angle X-ray scattering analysis. Additionally, the TDA method presented great robustness with varying SEM acceleration voltages and magnifications, which might alter the scope of alignment detection. With potential applications in nanofiber systems, this study offers a rapid and simple way to quantify CNT alignment, which plays a crucial role in transferring the CNT properties into engineering products.

Synthesis of Finite Molecular Nanotubes by Connecting Axially Functionalized Macrocycles

Synthesis of Finite Molecular Nanotubes by Connecting Axially Functionalized Macrocycles