Structure Of Carbon Nanotubes Research Articles

Molecular-scale mechanics of a crystalline polyethylene interface formed by projection of carbon nanotube structures

The semicrystalline nature of polymer chains induced by the intrusion of carbon nanotubes (CNTs) is a decisive factor in understanding the properties of interfacial regions. Herein, the structural and mechanical behavior of polyethylene (PE) formed around CNT surfaces were determined using a combination of classical molecular dynamics simulations and subcontinuum-scale analysis. The results suggest that inserting CNTs into the polymer domain forces the PE chains to align along the longitudinal axis of the CNTs. The interface functions as a nucleating agent, and the area occupied by the crystalline phase propagates radially as PE chains are stacked over long distances. The crystalline PE, grown with CNT as the central axis, exhibits extreme mechanical anisotropy, particularly for normal and shear deformations in the transverse direction. Therefore, this study provides an important theoretical guideline for understanding polymeric semi-crystals around CNTs.

Wear behavior and corrosion resistance of laser-clad Ni60-1 % carbon nanotubes coating

Carbon nanotubes (CNTs) can improve the performance of composite coatings as reinforcing powders due to their three-dimensional (3D) tubular structure and good self-lubricating properties. Unfortunately, CNTs are difficult to mix uniformly with other powders due to their extremely light mass and fragile microstructure. Therefore, in this study, the alcohol-stirring mixing method was used for powder mixing. The results showed that Ni60 powder and 1 wt% CNTs were mixed homogeneously by this method, and large-area CNTs deposition was achieved on the surface of Ni60 powder. The properties of the Ni60/CNTs coatings fabricated by laser cladding (LC) were examined. The microstructure of the Ni60/CNTs coating was refined, and M23C6 carbides were generated. Compared with the Ni60 coating, the microhardness of the Ni60/CNTs coating increased by 41.6 %, and the wear rate decreased by 76.76 %. The improvement is mainly due to the excellent self-lubricating properties of CNTs and their tubular structure, which improves the friction behavior of the coating. In addition, the refinement of microstructure and the generation of C23C6 carbides also play an enhanced role. The bridging of the tubular structure of CNTs and the filling effect of carbides resulted in improved corrosion resistance of the Ni60/CNTs coatings.

Enhancing the cycling stability of commercial silicon nanoparticles by carbon coating and thin layered single-walled carbon nanotube webbing

Silicon-based anode materials are considered as the most attractive alternatives to traditional graphite anodes, thereby advancing the evolution of new-generation lithium-ion battery technology. However, the inadequate electrical conduction of silicon-based materials, along with severe volume expansion during charging and discharging processes, limits their further technological applications. Herein, a dual-layer carbon shell configuration is designed to efficiently alleviate the substantial volumetric expansion of silicon during cycles, while simultaneously improving the efficiency of both electron and lithium ions. The effectiveness of this layered buffering approach is credited to the networked structure of outer single-walled carbon nanotubes (SWCNTs) layer, which is firmly attached to the inner carbon shell's surface. The modified structure not only elevates the level of electrical conduction, but also significantly reduces the internal stress due to silicon's expansion. The developed Si@C@SWCNT electrode materials exhibit high capacity of 1267.3 mA h g−1 after 500 cycles at 1 A g−1, and sustains an elevated rate capacity of 863 mA h g−1 at 8 A g−1. This study highlights the enormous potential of Si@C@SWCNT composites for use in lithium-ion batteries and provides new perspectives for further exploration and utilization of silicon-carbon anodes.

In-Situ Flame-Synthesized Carbon Nanomaterials via an Impinging Swirl Flow with an N-Butanol Pool

ABSTRACT This study aims to investigate the impact of flow rotation and oxygen concentration on the synthesis of carbon nanomaterials using n-butanol diffusion flames in a rotating stagnation flow with a liquid pool and a catalytic Ni substrate. With increasing angular velocity (ω), the diffusion flame shifts slightly toward the upper oxidizer nozzle, experiences a lower strain rate, and becomes stronger with a higher maximum flame temperature at a fixed oxygen concentration (ΩO). Meanwhile, the soot layer thickens and gradually turns yellowish. Field Emission Scanning Electron Microscopy (FESEM) analyses confirm that carbon nanotubes (CNTs) can only be fabricated at ω = 2 or 3 rps when ΩO = 21%, highlighting the critical role of flow rotation. Interestingly, the optimal positions for CNT synthesis consistently occur at the same sampling position (1.5 mm below the upper edge of the blue flame) for all values of oxygen concentration (ΩO). The corresponding temperature ranges for ΩO = 19%, 18%, and 17% are approximately 950°C, 820–920°C, and 800–850°C, respectively, which align with existing literature. High-resolution transmission electron microscopy (HRTEM) images reveal both typical straight tubular and bamboo-like CNT structures. Raman spectra indicate superior graphitization at high angular velocities (ω). Notably, at ω = 0 rps, the intensity ratio of the D- and G-bands is greater than 1 (ID/IG >1); however, as ω increases, the opposite holds (ID/IG <1), with its value gradually decreasing. This suggests that the swirl effect enhances graphite layer crystallization. Importantly, the strain rate controlled by flow rotation significantly influences CNT fabrication, considering both residence time and carbon source. The key finding of this study is that swirl flow enhances both the quality and quantity of CNTs synthesized via n-butanol diffusion flames.

NO2 gas response and recovery properties of ambipolar CNT-FETs with various CNT/CNT junctions

Gas sensors based on ambipolar carbon nanotube (CNT) field-effect transistors with various amounts of CNTs were fabricated by dielectrophoretic assembly. The nitrogen dioxide (NO2) gas response and recovery properties of the transistors were measured to investigate the effect of CNT amount on gas response. For the device with a small amount of CNTs, responses from the CNT bulk and CNT/electrode contacts were observed. For devices with a large amount of CNTs, in which a network-like structure of CNTs was observed near the electrodes, an increased current in both electron and hole conduction regions was observed compared with that for the device with a small amount of CNTs. The increased current in the electron conduction region rapidly decreased during recovery. This response is consistent with that of CNT/CNT X-type contacts, which have a high resistance before NO2 adsorption. Equivalent circuits of CNT channels with CNT/CNT contacts were developed, allowing the transistor behavior to be qualitatively discussed. Evaluation of time constants revealed that CNT/electrode contacts and CNT/CNT X-type contacts exhibited high NO2 adsorption and desorption rates, respectively.

Bamboo-shaped N-doped carbon nanotubes encapsulated with Co nanoparticles for improved microwave absorption properties

High reflection loss and wide absorption bandwidth materials are in great demand to prevent electromagnetic pollution and military applications. The composites prepared by combining different components with good dielectric and magnetic losses are expected to achieve ideal absorbing performance. In this study, a composite of cobalt nanoparticles enveloped in nitrogen-doped bamboo-like carbon nanotubes (Co@N-CNTs) was prepared by one-step annealing the mixture of melamine and cobalt nitrate at 800 °C in a mixed atmosphere of hydrogen and argon. Co nanoparticles derived from the reaction between H2 and cobalt nitrate during the sintering process were used as catalysts to prompt the carbonization of melamine and the formation of the bamboo-shaped N-doped carbon nanotubes, thus forming the composite structure of bamboo-shaped N-doped carbon nanotubes encapsulated with Co nanoparticles. This Co@N-CNTs composite not only had an excellent dielectric loss and magnetic loss but also greatly improved its impedance matching, thus having good electromagnetic wave absorption performance. The coating made from the Co@N-CNTs composite had a maximum reflection loss (RL) of −35.89 dB at only 1.8 mm thickness at 14.1 GHz and possessed an effective absorption bandwidth of up to 4.91 GHz (12.35–17.26 GHz), suggesting it a high-performance and wide-absorption bandwidth composite material.

Performance analysis of carbon nanotube and graphene nanoribbon based biochemical sensors at atomic scale

Advancements in fabrication technologies have led to the possibility of synthesizing atomic-scale graphene nanoribbon (GNR) and carbon nanotube (CNT) based nanodevices. The purpose of this study was to model the electronic properties and electrical characteristics of these devices by atomistic modeling using density functional theory and the non-equilibrium Green’s function and compare the effects of molecular functionalization and sensing. The potential profile of the device was computed using the three-dimensional Poisson equation for smaller applied bias within one voltage range. Simulations showed a bandgap of 1 eV for armchair GNRs (AGNRs), which were insensitive to functionalized amine molecules, resulting in fewer alterations in the density of states (DoS), transmission spectra and the device current (ΔI). The bandgap further increased to 2 eV upon rolling the GNR into a armchair CNT (ACNT), which further decreased sensitivity. However, changing the configuration of the AGNR to a zigzag GNR (ZGNR) led to remarkable changes in the DoS and transmission spectra and a significant improvement in sensitivity. This improvement increased by 1.5–2 times upon rolling the ZGNR into a zigzag CNT (ZCNT). Thus, at lower dimensions in atomic scale, we found an alteration in device current of the carbon structures that was directly proportional to sensitivity in the following order: ΔI ACNT < ΔI AGNR < ΔI ZGNR < ΔI ZCNT. However, the same was found to fall for ZGNR and ZCNT with an increase in width to length (W/L) ratio. This highlights the importance of smaller atomic structures and this work provides a guideline for effective utilization of these structures for biochemical sensing.

Investigation of Electromagnetic Wave Propagation in Triple Walled Carbon Nanotubes

This study examines the behavior of electromagnetic wave propagation in a unique and complex three-walled carbon nanotube structure. The structure is formed by nesting three distinct nanotubes, and the interactions between them are thoroughly analyzed, taking into account their varying electromagnetic, material, and nano properties. The structure is designed at a nanoscale to provide a comprehensive description of electromagnetic wave propagation, including the electromagnetic interaction between the second nanotube, located in the middle of the structure, and the other two nanotubes situated in both the inner and outer portions of the structure. This study presents novel findings that differ from existing literature on the subject, contributing to our understanding of this important area of research.

Nanocomposites Based on Thermoplastic Acrylic Resin with the Addition of Chemically Modified Multi-Walled Carbon Nanotubes.

The main goal of this work was an improvement in the mechanical and electrical properties of acrylic resin-based nanocomposites filled with chemically modified carbon nanotubes. For this purpose, the surface functionalization of multi-walled carbon nanotubes (MWCNTs) was carried out by means of aryl groups grafting via the diazotization reaction with selected aniline derivatives, and then nanocomposites based on ELIUM® resin were fabricated. FT-IR analysis confirmed the effectiveness of the carried-out chemical surface modification of MWCNTs as new bands on FT-IR spectra appeared in the measurements. TEM observations showed that carbon nanotube fragmentation did not occur during the modifications. According to the results from Raman spectroscopy, the least defective carbon nanotube structure was obtained for aniline modification. Transmission light microscopy analysis showed that the neat MWCNTs agglomerate strongly, while the proposed modifications improved their dispersion significantly. Viscosity tests confirmed, that as the nanofiller concentration increases, the viscosity of the mixture increases. The mixture with the highest dispersion of nanoparticles exhibited the most viscous behaviour. Finally, an enhancement in impact resistance and electrical conductivity was obtained for nanocomposites containing modified MWCNTs.

The Effect of He:O Plasma Treatment on the Structure of Multi-Walled Carbon Nanotubes

The Effect of He:O Plasma Treatment on the Structure of Multi-Walled Carbon Nanotubes

The effect of electrochemical treatment on the structure of single-walled carbon nanotubes: Towards better filling efficiency

Filled single-walled carbon nanotubes (f-SWCNT) are regarded as prospective materials with diverse applications, owing to the superior combination of their intrinsic properties with those of the filler material. The variety of the potential filler materials makes solution filling through open SWCNT channels under capillary forces the most flexible method for f-SWCNT production. However, the technique requires the additional step of SWCNT cap removal, and remains poorly efficient. Here, we evaluated how the structure of the SWCNTs impacts the filling efficiency depending on the conditions of electrochemical opening treatment under cyclic voltammetry protocols. We revealed the optimal upper vertex potential to be 1.1 V vs. RHE, corresponding to the trade-off between end-cap removal efficiency and yield of wall defect formation. It allowed us to achieve a filling efficiency of ∼1680 m cm−2 of gold nanowires length per unit SWCNT film area, which is ∼10 times greater than the filling efficiency of the untreated material.

Transition metal nitride/sulfide nanoparticles attached to nitrogen-doped carbon nanotubes synthesized by modified black powder detonation for efficient overall water splitting

To overcome the energy crisis, the rational construction of efficient electrolytic water catalysts is urgently required. Herein, an innovative proposal was presented for the preparation of self-supported electrolytic water catalysts on nickel foam (NF) substrates using modified black powder (BP) detonation method. The transient high temperature of the controlled detonation can obtain a variety of highly active catalytic components. First, carbon nanotubes (CNTs) were immobilized on NF by electroplating nickel to improve the pore utilization and electrical conductivity of NF. The unique hollow channel structure and extensive surface area of CNTs facilitated the attachment of the active catalysts. The introduction of Co metal salt not only controlled the reaction degreed effectively but also served as an effective transition metal source. With sulfur (S) source in BP and the additional nitrogen (N) source, the detonation successfully produced nano Co5.47N and Ni3S2. Nanocrystals Co5.47N and Ni3S2 along with N-doped CNTs, acquired via transient high-temperature reaction, were abound in defects. Consequently, the obtained sample exhibited excellent catalytic activities for both hydrogen evolution and oxygen evolution reactions. A remarkable overall water-splitting was achieved at a voltage of 1.52 V at 10 mA cm−2 in a two-electrode water electrolysis system.

Advance processing of cluster-free CNT reinforced 6082 Al matrix nanocomposites: influence of mechanical milling and cryomilling

ABSTRACT In the present study, lightweight high-strength carbon nanotubes (CNTs) reinforced aluminium-based composite was fabricated through powder metallurgical processing. The effect of planetary milling and cryogenic assisted milling on the structure, morphology, mechanical properties, phase composition, and thermal stability of CNTs reinforced Al6082 Al nanocomposites powders was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM)- Energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), and indentation techniques. The CNTs in the Aluminium (AL) matrix were distributed uniformly after 50 h of milling. Further, the cryomilling of 50 h milled Aluminium matrix composites (AMC) decreases agglomeration even more and was successful in cleaving the nanotubes as well as minimising entanglements. The broadening of diffraction peaks suggests a reduction in the crystallite size (from ~36 to ~20 nm) and an increase in induced strain. Milled powders were consolidated through the hot-press and spark plasma sintering technique. The mechanical properties of these AMCs were evaluated through indentation for hardness (>250 HV) and compressive testing techniques. SPSed samples reported better properties in comparison to hot-pressed samples. It is discovered that post-CM of Mechanical Milling (MM) powder aids in overcoming issues related to the agglomeration of Al/CNT composites, and the goal to fabricate tangle-free CNT reinforced composite was achieved. Moreover, it showed enhanced mechanical properties with a maximum yield strength of 210 MPa and good synergy between strength and ductility.

Application and structure of carbon nanotube and graphene-based flexible electrode materials and assembly modes of flexible lithium-ion batteries toward different functions

Application and structure of carbon nanotube and graphene-based flexible electrode materials and assembly modes of flexible lithium-ion batteries toward different functions

Toughening and strengthening of Cu-coated carbon nanotubes reinforced AZ61 magnesium matrix nanocomposites by improving interfacial bonding

Interfacial modification without damaging the structure of carbon nanotubes (CNTs) is urgently needed to improve the performance of CNTs reinforced metal matrix nanocomposites. To fabricate CNTs/AZ61 nanocomposite with strong interfacial bonding, copper-coated CNTs (0.15–2.4 vol%) and AZ61 powder were employed through the process of ball milling mixing, vacuum hot pressing and extrusion. The powder and nanocomposites were characterized by HRTEM, SEM, XRD and compressive test to study the distribution of reinforcements, microstructures, interfacial structure and compression behavior. During the high-temperature fabrication process, in-situ interfacial reactions occurred between Cu particles of CNTs and Mg, Al and Zn elements in AZ61 matrix. As a result, the formation of interfacial reaction phases, such as AlCu3, Al2Cu, Cu2Mg, CuMg2, Cu0.61Zn0.39 and MgAl2C2 phases, and their diffused and/or coherent interface significantly strengthen the interfacial bonding. With only 0.15 vol% CNTs, the work of fracture and compression strength of the composite are 40 % and 20 % higher than those of pure AZ61, respectively. The dominating toughening mechanisms are the load transfer role of scattered CNTs and fine-grain effect. The dominating strengthening mechanisms are thermal mismatch and Orowan strengthening.

Finely tuned water structure and transport in functionalized carbon nanotube membranes during desalination.

Molecular dynamics simulations were performed to tune the transport of water molecules in nanostructured membrane in a desalination process. Four armchair-type (7,7), (8,8), (9,9) and (10,10) carbon nanotubes (CNTs) with pore diameters around 1 nm were chosen, their interior surfaces were modified with -OH, -CH3 and -F groups. Simulation results show that water transport in nanochannel depends on confined water structures which could be regulated by precisely controlled channel diameter and chemical functionalization. Increasing CNT diameter changes water structures from single-file-like to be square and hexagonal-like, then into a disordered pattern, resulting in a concave-shaped trend of water permeance. The -OH functional groups promote structural ordering of water molecules in (7,7) CNT, but disrupt water structures in (8,8) and (9,9) CNTs, and reduce the order degree of water molecules in (10,10) CNT, moreover, exert an attraction to enhance surface friction inside channel. The -CH3 groups induce more strictly single-file movement of water molecules in (7,7) CNT, turning water structures in (8,8) and (9,9) CNTs into two and triangular column arrangements, improving water transport, however, causing again square-like water structure in (10,10) CNT. Fluorinations of CNT make water structure more disordered in (7,7), (9,9) and (10,10) CNTs, while enhance the square water structure in (8,8) CNT with a lower water permeance. Through changing channel diameter and functionalization, the low tetrahedral order corresponds to a more single-file-like water structure, associated with rapid water diffusion and high permeability; an increase in tetrahedrality results in more ice-like water structures, lower water diffusion coefficients, and permeability. The results of this study demonstrate that water transport could be finely regulated via a functionalized CNT membrane.

Structural optimization of novel one-dimensional composites based on in situ – grown 1D CNTs with an amorphous structure and 2D MoS2 nanosheets for improved Li storage

After optimizing the content of glucose and the structure of carbon nanotubes, the composite was achieved. Carbon nanotubes were used to control the vulcanization growth of MoS2. The MoS2@C composites delivered excellent electrochemical properties.

Dependence of reinforcement degree on specific surface on carbon nanotubes (nanofibers) for polymer nanocomposites

It has been shown that the well-known parameter, namely, real specific surface of nanofiller (its aggregates) can be used for description of both surface and structure of carbon nanotubes (nanofibers) in polymer nanocomposites. The relationship between radius of nanofiller annular formations, fractal dimension of surface and specific surface was obtained. In its turn, the reinforcement degree of considered nanocomposites is defined by specific surface of nanofiller only at its fixed content, which is function of size of annular formations for this type of nanofiller. It has been shown that the greatest reinforcing effect can be given carbon nanotubes (nanofibers) having large diameter and radius of their annular formations.

Optically active defects in carbon nanotubes via chlorination: computational insights

The effect of chlorination on the electronic structure and optical spectra of (6,2) carbon nanotubes is studied computationally, revealing optically active defect-related states when chlorines are placed close to each other at a dilute concentration.

Application and Purification of Carbon Nanotubes in Dye-sensitized Solar Cells

With the global energy consumption steadily rising, seeking alternative energy sources has emerged as a shared objective among nations worldwide. The emergence and advancement of carbon nanotubes have introduced fresh perspectives to the domain of pollution-free and renewable solar cells, garnering significant attention in recent times. Currently, the application of carbon nanotubes in solar cells is not yet mature. This paper introduces the special one-dimensional structure and excellent conductivity of carbon nanotubes, which make them an ideal material for constructing photovoltaic cells. The paper explores how carbon nanotubes are utilized in dye-sensitized solar cells and analyzes three methods of carbon nanotube purification: hydrochloric acid purification, nitric acid purification, and ultrasonic filtration. Research shows that carbon nanotubes have great development prospects in the field of dye-sensitized cells. Introducing dye-sensitized solar cells can effectively improve conversion efficiency. However, the instability and difficulty in sealing of liquid electrolytes limit their application. Solid electrolytes that can avoid these shortcomings are still generally lacking in efficiency. This paper looks forward to future researchers developing more efficient and mature applications of carbon nanotubes in the direction of solid electrolytes, so that carbon nanotubes can achieve higher conversion rates and realize large-scale applications after introducing dye-sensitized solar cells, benefiting human society.