Carbon Nanotube Arrays Research Articles

Изменение теплопроводности многослойного массива углеродных нанотрубок при его поперечном сжатии

Numerical simulation of thermal conductivity across a multilayer array of single-walled carbon nanotubes is carried out. The effect of transverse compression of the array on thermal conductivity has been studied. It is shown that the compression of the array can occur uniformly when all the nanotubes of the array are compressed equally, and it can occur inhomogeneously when a part of the nanotubes is strongly compressed, and the other part is weakly compressed. With homogeneous compression, the thermal conductivity of the array increases, but with inhomogeneous compression, it does not change and may even decrease in case of a large number of layers. This effect is especially pronounced for arrays of nanotubes of small diameter (D < 2 nm)

Tensile properties and fracture behavior of carbon nanotube-sheets/carbon fibers epoxy-impregnated bundle composites

An interesting technique for modifying carbon fiber-reinforced polymer matrix composites is through hybridization with carbon nanotubes (CNTs). Carbon nanotubes sheets/carbon fibers offer potential benefits of nanoscale reinforcement to the well-established fibrous composites by creating multiscale hybrid micro-nano composites. In this study, the tensile properties of high tensile strength polyacrylonitrile (PAN)- and high modulus pitch-based carbon fiber-reinforced polymer matrix composites incorporating CNT sheets (CNT-sh/CFs/Ep-H: CNT sheets/carbon fibers/epoxy hybrid composites) were investigated. To fabricate CNT sheets, CNT was vertically grown on a quartz glass plate by chemical vapor deposition. A solid-state drawing and winding technique was applied to transform the vertically aligned CNT array into horizontally aligned CNT sheets. The tensile modulus of the CNT-sh/CFs/Ep-H was higher than that of the composite in the as-received state (CFs/Ep: carbon fibers/epoxy bundle composite). The tensile strength of the CNT-sh/PAN-based CF/Ep-H was lower than that of the PAN-based CF/Ep, whereas the tensile strength of the CNT-sh/pitch-based CF/Ep-H was higher than that of the pitch-based CF/Ep.

Metal-encapsulated carbon nanotube arrays for enhancing electrocatalytic nitrate reduction in wastewater: importance of lying-down to standing-up structure transition

The structure transition from lying-down to standing-up greatly improves the performance of metal-encapsulated and nitrogen-doped carbon-based catalysts towards electrocatalytic nitrate reduction.

Carbon dioxide-boosted growth of high-density and vertically aligned carbon nanotube arrays on a stainless steel mesh.

Vertically aligned carbon nanotubes (VACNTs), a unique group of highly aligned CNTs normal to a substrate, have been extensively studied during the past decades. However, it is a long-standing challenge to improve the height of VACNTs due to the incidental deactivation of catalysts during growth. Herein, we demonstrate a facile strategy toward synthesizing high-density and well-aligned CNT arrays from in situ formed Fe-based catalysts on a stainless steel (SS) mesh. These catalysts were generated by direct oxidation-reduction treatment to the SS, which had excellent adhesion on the mesh substrate, and thus suppressed catalyst aggregation and promoted CNT growth under the flow of C2H2. In particular, by feeding additional CO2 at an optimal rate, the height of CNT arrays could be boosted from ca. 15 μm to ca. 80.0 μm, one of the highest heights observed for VACNTs on SS-based substrates so far. This is attributed to the prolonged activity of the catalysts by CO2 induced removal of extra carbon. Our study might provide an insight into the development of efficient strategies for VACNT growth on conductive substrates.

Capillary-force-driven self-assembly of carbon nanotubes: from ab initio calculations to modeling of self-assembly.

In elasto-capillary driven self-assembly of arrays of carbon nanotubes (CNTs) different factors play a role, from the mechanical properties of CNTs to the array geometry. In this work, we provide a multi-scale investigation where we first use density functional theory (DFT) to predict fully ab initio relevant mechanical properties such as Young's modulus, Poisson's ratio, and surface energy. To the best of our knowledge, we are the first to report DFT calculations of the surface energy of CNTs. Then, we feed the computed DFT parameters into a model for capillary-force-driven self-assembly of CNTs. By doing so, we are able to derive and predict cross-correlation between material parameters and array architecture.

Синтез и оценка распределения диаметров углеродных нанотрубок в вертикально ориентированном массиве

Vertically aligned carbon nanotubes arrays were synthesized via catalytic chemical vapor deposition technique. An opportunity to decreasing of acetylene as a carbon precursor contain down to 0.2% was demonstrated. An iron acetate as an alternative catalyst was proposed. Diameters of carbon nanotubes were estimated by them Raman spectra. Considering resonant behavior of radial breathing modes and them significant environment influencing, an approach based on а profile analyzing of G-band was offered to revel of nanotubes diameter distribution features.

Electrochemically Oxidized Aligned Carbon Nanotube Arrays Embedding Foam Substrates for Water Splitting

Electrochemically Oxidized Aligned Carbon Nanotube Arrays Embedding Foam Substrates for Water Splitting

Highly Oriented Fluorinated Carbon Nanotube Arrays for High Specific Capacity Lithium Primary Battery

Highly Oriented Fluorinated Carbon Nanotube Arrays for High Specific Capacity Lithium Primary Battery

Double Synergetic Feco-Nanoparticles and Single Atoms Embedded in N-Doped Carbon Nanotube Arrays as Efficient Bifunctional Catalyst for High-Performance Zinc-Air Batteries

Double Synergetic Feco-Nanoparticles and Single Atoms Embedded in N-Doped Carbon Nanotube Arrays as Efficient Bifunctional Catalyst for High-Performance Zinc-Air Batteries

Synthesis and diameter distribution approach of vertically aligned carbon nanotubes array

Vertically aligned carbon nanotubes arrays were synthesized via catalytic chemical vapor deposition technique. An opportunity to decreasing of acetylene as a carbon precursor contain down to 0.2% was demonstrated. An iron acetate as an alternative catalyst was proposed. Diameters of carbon nanotubes were estimated by them Raman spectra. Considering resonant behavior of radial breathing modes and them significant environment influencing, an approach based on a profile analyzing of G-band was offered to revel of nanotubes diameter distribution features. Keywords: carbon nanotubes, chemical vapor deposition, Raman spectroscopy, radial breathing modes, G-band.

Symmetrical growth of carbon nanotube arrays on FeSiAl micro-flake for enhancement of lithium-ion battery capacity

The efficient and economic growth of high-purity carbon nanotube (CNT) arrays remains a great challenge due to the synthetic complexity and difficulty of high-precision control. Herein, a high-yield production method for direct symmetrical growth of CNT arrays using FeSiAl micro-flake catalyst was developed. The FeSiAl micro-flakes combined the role of the substrate, buffer layer, and catalyst, which led to ultra-high catalytic efficiency of 297% during catalytic chemical vapor deposition (CCVD). After carefully considering the reaction temperature and time, the growth kinetics and corresponding mechanism were investigated. As conductive additives, CNT arrays have excellent application potential in high energy density ternary cathode materials. The average specific discharge capacity was ∼160 mAh g−1 at 5 C, which represents a great improvement relative to commercially available conductive additive super p (SP). This FeSiAl micro-flake catalyst provides a novel methodology for the efficient and fast growth of CNT arrays on a large scale with potential applications in the energy storage and micro-nano device fields.

Flame-Assisted Synthesis of O-Coordinated Single-Atom Catalysts for Efficient Electrocatalytic Oxygen Reduction and Hydrogen Evolution Reaction.

Single-atom catalysts (SACs) exhibit intriguing performance in electrocatalysis owing to their maximized atom utilizations and unique electronic structures, but effective anchoring metal atoms with defined coordination structure on hierarchical integrated electrode remain a challenge. Herein, a fast and facial flame-assisted strategy is developed to construct oxygen-coordinated SACs on integrated carbon nanotube (CNT) arrays with promising applications in electrocatalysis. Density functional theory calculations show that oxygen in carbon substrate imparts homogeneous sites for the efficient anchoring of metal atoms, thereby enabling SACs to disperse uniformly and firmly and thus bringing optimized activities. Moreover, the integrated CNT array with abundant oxygen-containing groups is constructed and has been used as an efficient matrix for anchoring metal atoms (CNT-O@M) via a flame-assisted method. The as-prepared CNT-O@M (M = Co and Pt as typical examples) shows excellent activities in electrocatalytic oxygen reduction reaction and hydrogen evolution reaction with utilization of active site as high as 75.7%, which is superior to the reported SACs. Particularly, the performance of CNT-O@M can maintain stably under various harsh conditions, showing a promising prospect in the long-time applications. The methodology and concept proposed in this work could be extended to the synthesis of a variety of integrated SACs for efficient electrocatalysis.

Piezoelectric response of aligned carbon nanotubes depending on sublayer material

The results of experimental studies of the effect of the sublayer material on the piezoelectric response and sensitivity to mechanical deformations of aligned carbon nanotubes (CNTs) are presented. It is shown that the highest piezoelectric response (136 nA at a pressing force of 4 μN) and best sensitivity are demonstrated by CNTs grown on a Mo sublayer. This dependence is probably due to the geometric parameters of CNTs and the structure of the CNT array as a whole. The results obtained can be used to develop energy-efficient nanogenerators based on CNT arrays.

A Compact Physical Drain Current Model of Multitube Carbon Nanotube Field Effect Transistor Including Diameter Dispersion Effects

Carbon nanotube field-effect transistor (CNTFET) shows great potential for digital and analog applications due to the unique 1-D ballistic carrier transport in carbon nanotubes (CNTs). A new compact physical model for CNT Schottky-barrier transistors is proposed in this article. The Schottky barrier between the contact metal and CNTs is described by using an effective barrier height, and more importantly, the influence of using CNT arrays or networks rather than a single CNT as the device channel is considered in this model. Moreover, the trapping effect is investigated and modeled by adding <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> delay element to the equivalent circuit. The model is proposed in a concise form to avoid complex operations such as integration and is compatible with circuit simulation. The simulation results of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}-{V}$ </tex-math></inline-formula> characteristics are verified to be in agreement with experimental data.

Electro-optic hybrid aligned nematic device utilizing carbon nanotube arrays and two-dimensional hexagonal boron nitride nanosheet as alignment substrates.

Hybrid-aligned nematic (HAN) liquid crystal (LC) devices have both fundamental and technological importance for their applications in LC adaptive lenses, low voltage LC displays, smart windows, and many more. We report the fabrication and characterization of a nanostructure-based HAN device employing vertically aligned carbon nanotube (VA-CNT) arrays as the homeotropic alignment agent on one side and two-dimensional (2D) hexagonal boron nitride (h-BN) as the planar alignment agent on the other side of the LC cell. The LC achieves the HAN configuration in the cell, i.e., homeotropic alignment at the VA-CNT side due to the π-π stacking interaction between the LC and CNTs, and planar alignment at the h-BN side due to the π-π stacking interaction between the LC and h-BN. When an applied electric field is ramped up across this VA-CNT/h-BN HAN cell, the LC (positive anisotropic) obtains a homeotropic state, requiring no threshold voltage to start the reorientation process; this effect is similar to that of a traditional polyimide (PI)-based HAN device. This VA-CNT/h-BN HAN cell successfully demonstrates the optical, electro-optical operations and the electric field-induced dynamic response. This study reveals that two inorganic nanostructured surfaces, VA-CNT arrays and 2D h-BN, can efficiently replace the organic PI alignment agents when needed and retain the HAN device's necessary electro-optical performances. These results substantially expand the fundamental understanding and the scope of utilizing various nanostructured surfaces for LC alignment mechanisms.

Functionalized semiconducting carbon nanotube arrays for gas phase explosives detection

Single molecule detection systems are of considerable practical interest in sensing applications, such as disease detection or transient kinetics monitoring, where ultra-sensitive measurements are needed. Trace detection of explosives is an application where the mere presence, not necessarily the concentration, of an analyte is cause for concern. As in many other sensing applications, carbon nanotube (CNT) based devices are under study for single molecule detection systems, motivated by interest in reducing the size, cost, and power requirements of current sensing systems. Although CNT sensors have been shown to be highly sensitive to some analytes, a longstanding obstacle to the development of ultra-sensitve CNT sensors has been their lack of selectivity. Ab initio modeling of functionalized semiconducting CNT arrays suggests that they offer sensitive and selective explosives detection, capable of distinguishing explosives from common background gases, distinguishing nitroaromatic from nitramine explosives, and discriminating among distinct nitramine explosives with very similar structures.

Lithography-free synthesis of periodic, vertically-aligned, multi-walled carbon nanotube arrays

Until now, the growth of periodic vertically aligned multi-walled carbon nanotube (VA-MWCNT) arrays was dependent on at least one lithography step during fabrication. Here, we demonstrate a lithography-free fabrication method to grow hexagonal arrays of self-standing VA-MWCNTs with tunable pitch and MWCNT size. The MWCNTs are synthesized by plasma enhanced chemical vapor deposition (PECVD) from Ni catalyst particles. Template guided dewetting of a thin Ni film on a hexagonally close-packed silica particle monolayer provides periodically distributed Ni catalyst particles as seeds for the growth of the periodic MWCNT arrays. The diameter of the silica particles directly controls the pitch of the periodic VA-MWCNT arrays from 600 nm to as small as 160 nm. The diameter and length of the individual MWCNTs can also be readily adjusted and are a function of the Ni particle size and PECVD time. This unique method of lithography-free growth of periodic VA-MWCNT arrays can be utilized for the fabrication of large-scale biomimetic materials.

A review of aligned carbon nanotube arrays and carbon/carbon composites: Fabrication, thermal conduction properties and applications in thermal management

A review of aligned carbon nanotube arrays and carbon/carbon composites: Fabrication, thermal conduction properties and applications in thermal management

Tunable Low Crystallinity Carbon Nanotubes/Silicon Schottky Junction Arrays and Their Potential Application for Gas Sensing.

Highly ordered nanostructure arrays have attracted wide attention due to their wide range of applicability, particularly in fabricating devices containing scalable and controllable junctions. In this work, highly ordered carbon nanotube (CNT) arrays grown directly on Si substrates were fabricated, and their electronic transport properties as a function of wall thickness were explored. The CNTs were synthesized by chemical vapor deposition inside porous alumina membranes, previously fabricated on n-type Si substrates. The morphology of the CNTs, controlled by the synthesis parameters, was characterized by electron microscopies and Raman spectroscopy, revealing that CNTs exhibit low crystallinity (LC). A study of conductance as a function of temperature indicated that the dominant electric transport mechanism is the 3D variable range hopping. The electrical transport explored by I–V curves was approached by an equivalent circuit based on a Schottky diode and resistances related to the morphology of the nanotubes. These junction arrays can be applied in several fields, particularly in this work we explored their performance in gas sensing mode and found a fast and reliable resistive response at room temperature in devices containing LC-CNTs with wall thickness between 0.4 nm and 1.1 nm.

Terahertz transistors based on aligned carbon nanotube arrays

Terahertz transistors based on aligned carbon nanotube arrays