Conductivity Of Carbon Nanotubes Research Articles

Chirality and length-dependent electron transmission of fullerene-capped chiral carbon nanotubes sandwiched in gold electrodes.

In order to develop high-performance CNT-based electronic and optoelectronic devices, it is crucial to establish the relationship between the electron transport properties of carbon nanotubes (CNTs) and their structures. In this work, we have investigated the transport properties of chiral (8, m) and (10, m) CNTs sandwiched between two gold electrodes by employing nonequilibrium Green's function (NEGF) combined with density functional theory (DFT). We demonstrate that with the change of chirality the transport property changes, as predicted by the (n - m) rule. The change of length is also considered. Our results show that the electrical conductance of (10, m) CNTs is larger than that of the (8, m) CNTs, due to larger diameter. Furthermore, we found that the (8, 1) chiral CNT does not follow the (n - m) rule in shorter length and it shows metallic behavior. The cohesive energy, wavefunctions of electronic states, and coupling energy calculation indicate that the devices considered in this study are stable. The transmission spectra, current vs. voltage curves, and transmission eigenchannels provide strong evidence for our findings. Among the (10, m) series, (10, 3) CNT would be the optimal choice for a semiconducting molecular junction device with a significant conductance of 20 μA at 0.8 bias voltage.

MoS2 quantum dot-decorated CNT networks as a sulfur host for enhanced electrochemical kinetics in advanced lithium-sulfur batteries.

The slow redox kinetics and shuttle effect of polysulfides severely obstruct the further development of lithium-sulfur (Li-S) batteries. Constructing sulfur host materials with high conductivity and catalytic capability is well acknowledged as an effective strategy for promoting polysulfide conversion. Herein, a well-designed MoS2 QDs-CNTs/S@Ni(OH)2 (labeled as MoS2 QDs-CNTs/S@NH) cathode was synthesized via a hydrothermal process, in which conductive polar MoS2 quantum dot-decorated carbon nanotube (CNT) networks coated with an ultrathin Ni(OH)2 layer acted as an efficient electrocatalyst. MoS2 QD nanoparticles with a high conductivity and catalytic nature can enhance the kinetics of polysulfide conversion, expedite Li2S nucleation, and decrease the reaction energy barrier. The thin outer Ni(OH)2 layer physically confines active sulfur and meanwhile provides abundant sites for adsorption and conversion of polysulfides. Benefiting from these merits, a battery using MoS2 QDs-CNTs/S@NH as the sulfur host cathode exhibits excellent electrochemical performances with rate capabilities of 953.7 mA h g-1 at 0.1C and 606.6 mA h g-1 at 2.0C. A prominent cycling stability of a 0.052% decay rate per cycle after 800 cycles is achieved even at 2C.

Conductive single-walled carbon nanotubes synthesized using a Fe–Mo/MgO catalyst for LiNi0.5Co0.2Mn0.3O2 lithium-ion batteries

Single-walled carbon nanotubes were developed by chemical vapor deposition as conductive additives suitable for cathode materials, and it was found that their addition led to a significant increase in the conductivity of the active material.

НОВЫЕ МАТЕРИАЛЫ ДЛЯ ГИБКОЙ ЭЛЕКТРОНИКИ: ИССЛЕДОВАНИЕ СВОЙСТВ И ОБЛАСТЕЙ ПРИМЕНЕНИЯ

This paper reviews the latest materials for flexible electronics applications, including their electrical, mechanical, optical, and chemical properties. It analyzes the potential for using these materials in various fields, such as flexible displays, wearable devices, medical implants, and energy systems. Particular attention is paid to recent advances in the development of conductive polymers, car-bon nanotubes, and hybrid nanocomposites. Current challenges associated with integrating new materi-als into commercial devices and prospects for further research in this rapidly developing field are dis-cussed.

Crafting "brick-mud" segregated nanocomposites: a novel approach to superior electromagnetic interference shielding, electrical insulation, and thermal conductivity in biopolymers.

As electronic devices continue to be integrated, miniaturized, and operated at higher frequencies, the demand for green, advanced polymer nanocomposites with superior electromagnetic interference (EMI) shielding, thermal conduction, and electrical insulation properties significantly increases. However, achieving such multifunctional nanocomposites is challenging due to the inherent contradiction between electrical and magnetic properties. Biopolymer nanocomposites of polycaprolactone (PCL)/boron nitride (BN)@polylactic acid (PLA)/multi-walled carbon nanotubes (CNTs) ((PCL/BN)@(PLA/CNTs)) exhibit a unique "brick-mud" segregated double-network structure. This configuration effectively separates high-melting-point PLA/CNTs conductive phase from the PCL/BN insulating matrix. PLA/CNTs particles contribute to enhanced EMI shielding by attenuating electromagnetic waves, while also improving insulation by disrupting electron transfer within the PCL/BN phase. Additionally, incorporating conductive CNTs and thermal conductive BN further boosts the thermal conductivity (TC) of the nanocomposites. The structured sample (s-8B8C), which contains 8 wt% BN and 8 wt% CNTs, achieves an EMI shielding effectiveness (SE) of 31.4 dB in the X-band, a TC of 0.6 W m-1 K-1, and a volume resistivity of 7.2 × 1011 Ω cm. In summary, the "brick-mud" segregated structure facilitates the development of advanced biopolymer nanocomposites for electronic applications, leveraging sustainable materials for broad potential use.

An anti-corrosive cellulose nanocrystal/carbon nanotube derived Zn anode interface for dendrite-free aqueous Zn-ion batteries.

Notorious zinc dendrite growth and hydrogen precipitation reactions disrupt the galvanic/stripping process at the electrolyte/electrode interface, which seriously affects the cycling stability of zinc anodes in aqueous zinc ion batteries. To improve the stability and reversibility of zinc anodes, we report an artificial SEI consisting of hydrophobic carbon nanocrystals and highly conductive carbon nanotube networks. This interfacial hydrophobicity effectively excludes free water from the surface of the zinc anode, which prevents water erosion and reduces the interfacial side reactions, resulting in a significant improvement in the cycling stability and coulombic efficiency of Zn plating/stripping. Benefiting from the reversible proton storage and fast desolvation kinetic behavior of the CNC/CNT interlayer, the stable cycling time of Zn/Zn symmetric batteries exceeds 700 h even at a high current density of 5 mA cm-2. The assembled CNC/CNT@Zn‖V2O5 full cell maintains a high capacity of 101.1 mA h g-1 after 5000 cycles (1.0 mA g-1). This study opens up a new area for expanding the use of organic compounds in zinc anode protection and offers a promising strategy for accelerating the development of aqueous zinc-ion batteries.

Additive manufacturing of highly conductive carbon nanotube architectures towards carbon-based flexible thermoelectric generators

SWCNT/epoxy-based p-type 3D-printed TE material with power factor 102 μW mK−2. SWCNT/epoxy-based n-type 3D-printed TE material with power factor 75 μW mK−2. Open circuit voltage of 3D-CTEG: VOC = 13.6 mV. Power output of 3D-CTEG: Pmax = 4.1 μW.

Mountain-protection-mesh-inspired pSi@pPAN/CNTs composites as stable anode materials for lithium-ion batteries

Silicon (Si) is the most promising candidate for next-generation anode material of lithium-ion batteries. However, its commercial application is impeded by the poor cycling stability caused by the pulverization. Herein, we draw inspiration from mountain protection mesh and design a micrometer-scale porous core–shell structure via the phase inversion. The porous Si core's cavity can accommodate the volume expansion during lithiation, while the external mesh-like coating, composed of porous polyacrylonitrile (PAN) and conductive carbon nanotubes (CNTs), effectively restrains the outward expansion of Si. The synergistic effect of these components effectively enhances cycling stability, resulting in a capacity of 907.56 mAh/g at 1.0 A/g after 500 cycles. This study offers a scalable and cost-effective approach for the practical application of Si.

Reduction of thermal conductivity in carbon nanotubes by fullerene encapsulation from machine-learning molecular dynamics simulations

The carbon nano-peapod is a representative structure with interlayer van der Waals (vdW) interactions, in which encapsulated fullerene molecules play a critical role in modulating the transport properties of the carbon nanotubes (CNTs). In particular, their influence on the thermal transport characteristics has been the focal point of considerable attention. In this study, we trained an accurate machine learning potential for fullerene-encapsulated CNTs based on the efficient NEP model to investigate their thermal properties. Using equilibrium molecular dynamics simulation along with the spectral decomposition method for thermal conductivity, we find that the thermal conductivity of fullerene-encapsulated CNTs is roughly 55% lower than that of empty CNTs, aligning with experimental observations for CNT bundles with fullerene encapsulation [Kodama et al., Nat. Mater. 16, 892 (2017)]. The research suggests that weak vdW interactions between both the fullerene and CNTs, as well as between fullerene molecules themselves, hinder phonon propagation. The encapsulated fullerene contributes to an increase in phonon scattering within the CNTs, ultimately leading to a reduction in thermal conductivity. We utilized machine learning potential to investigate the structure of fullerene-encapsulated CNTs and their heat transport property. This approach provides valuable insights for performance research of complex systems featuring interlayer vdW interactions.

A comprehensive study of spray coating technique parameters and chemical postdeposition treatments for transparent conducting SWCNT thin films

The demands for transparent conducting films (TCFs) are continuously increasing and the future of this industry is going toward large scale, cheap and mechanically stable electronics. This study shows a simple way to fabricate low-cost transparent conductive single-walled carbon nanotube (SWCNT) thin films by spray coating. The work employed here demonstrates that it is possible to fabricate highly efficient SWCNT TCFs without the use of expensive ultrasonic spray coating equipment. Highly conductive TCFs were prepared by dispersing SWCNTs in an N-Methyl-2-pyrrolidone (NMP) solution. The spray coated TCF properties were studied by the effect of spray gun carrier gas pressure, concentration, and volume sprayed onto the substrates. The prepared thin films were subjected to post treatments with nitric acid (HNO3) using different treatment methods and times in order to improve the electrical conductivity. To further investigate the effect of p-doping in SWCNT thin films, HNO3 treatments were combined with thionyl chloride (SOCl2). The experimental results indicated that spray coating is an effective method to obtain highly conductive films without any chemical treatment, resulting in 273 Ω/sq sheet resistance, at 84% in the visible range. Additionally, the optimized films treated with both HNO3 and HNO3/SOCl2 showed great improvements at 83%–85% in the visible range and in sheet resistances followed by 98 and 103 Ω/sq with very good FOM values (1.6 × 10−3 and 2 × 10−3, respectively).

A Safe Separator with Heat‐Dispersing Channels for High‐Rate Lithium‐Ion Batteries

AbstractSeparators are becoming increasingly important in both academic research and industrial production as a means of enhancing the performance of lithium‐ion batteries (LIBs), particularly at a high rate. However, fast charge–discharge processes will produce local heat accumulation, which accelerates the local reaction rate of Li+ to form lithium dendrites. Commercial polyolefin separators fail to tackle the above issue due to inferior thermal stability. Herein, a core–shell structure is proposed to reinforce the polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) matrix through encircling carbon nanotube (CNT) by adherent polydopamine (PDA). The core–shell 3D structure with PDA avoids the short circuits caused by the electrically conductive CNT, and meantime, the CNT serves as an effective radiator for dispersing local heat sources verified through finite element analysis. The composite separator allows LIBs to achieve high Li+ conductivity (0.49 × 10−3 S cm−1) and Li+ transfer number (0.74), resulting in a high capacity retention of 87.35% after 800 cycles at 5C. In particular, the safety is confirmed that the composite separator avoids violent growth of lithium dendrites caused by local heat accumulation through phase‐field simulations. This work suggests a promising approach for the fabrication of core–shell nanotube composite separators for high‐rate and safe LIBs.

Accelerating Proton and Electron Transfer Enables Highly Active Fe─N─C Catalyst for Electrochemical CO2 Reduction

AbstractAtomically dispersed Fe─N─C catalysts display great potential for efficient CO production in the field of electrochemical CO2 reduction (ECR), but still suffer from unsatisfactory activity limited by the slow proton and electron transfer during the ECR process. Here, a superior Fe─N─C electrocatalyst is designed by anchoring the individual FeN4 sites and Fe nanoparticles onto highly conductive carbon nanotubes. The resultant catalyst displays a commendable CO partial current density of 16.01 mA cm−2 with a turnover frequency of 3519.6 h−1 at −0.65 V in an H‐type cell, and also exhibits CO selectivity > 90% under high current density over 120 mA cm−2 in a flow cell. This remarkable activity exceeds a host of previously reported Fe─N─C catalysts. The findings indicate that the carbon nanotube facilitates CO production due to its strong capability of electron transport and charge transfer. In situ spectroscopic analysis, controlled experiments, and theoretical calculations reveal that Fe nanoparticles effectively promote water dissociation and the subsequent protonation step, accelerate the formation of *COOH intermediate, and thus greatly enhance the ECR activity.

Polypyrrole@CNT@PU Conductive Sponge-Based Triboelectric Nanogenerators for Human Motion Monitoring and Self-Powered Ammonia Sensing.

Elastic sponges are ideal materials for triboelectric nanogenerators (TENGs) to harvest irregular and random mechanical energy from the environment. However, the conductive design of the elastic materials in TENGs often limits its applications. In this work, we have demonstrated that an elastic conductive sponge can be used as the triboelectric layer and electrode for TENGs. Such an elastic conductive sponge is prepared by a simple way of adsorbing multiwalled carbon nanotubes and monomers of pyrrole to grow conductive polypyrroles on the surface of an elastic polyurethane (PU) sponge. Due to the porous structure of the PU sponge and the conductive multiwalled carbon nanotubes (MWCNTs), PPy on the surface of PU could provide a large contact area to improve the output performance of TENGs, and the conductive sponge-based TENG could generate an output of open-circuit voltage of 110 V or a short-circuit current of 12 μA, respectively. The good flexibility of the conductive PU sponge makes the TENG harvest the kinetic energy of disordered motion with different amplitudes, allowing for human motion monitoring. Furthermore, the porous structure of PU and the synergistic effects of PPy and MWCNTs enable the conductive sponge to sense NH3 as a self-powered NH3 sensor. This work offers a simple way to construct a flexible TENG system for random mechanical energy harvesting, human motion monitoring, and self-powered NH3 sensing.

Piezoresistive Theory and Numerical Calculation for Carbon Nanotube Polymer Composite.

A three-dimensional theory has been established for the piezoresistivity of carbon nanotube (CNT) polymer composites. Based on the Mori-Tanaka method in meso-mechanics theory and considering quantum tunneling effect between CNTs, an approach to calculate equivalent electrical conductivity of composites was proposed. On this basis, a piezoresistive theory, which incorporates the effect of composites' geometric nonlinearity, was developed for CNT polymer composites. The theory is dependent only on some basic physical parameters of the materials. A finite element formula of the theory for the numerical calculation of piezoresistivity was presented from the analysis of both elastic and electric fields. Numerical simulations demonstrated that the results predicted by the theory were in good agreement with those of the experimental tests. Parameter sensitivity analysis revealed that when both the potential barrier height of the matrix and the initial average separation distance between CNTs increased, the piezoresistivity obviously increased. However, with the increase in aspect ratio and CNT conductivity, the piezoresistivity decreased gradually. A practical engineering application of this theory is also provided.

Tough, self‐healing, and recyclable cross‐linked polyurethane elastomers via synergistic effect of dual dynamic covalent bonds

AbstractBased on the irresistible inherent trade‐off between the mechanical and self‐healing performances of cross‐linked polyurethane materials, there is still an intractable challenge to design efficient self‐healing and tough elastomers, especially in flexible sensors. Herein, a tough, efficient self‐healing, and recyclable cross‐linked polyurethane elastomer (DTPU) was prepared by integrating oxime‐carbamate bonds and thiourethane bonds into the network. The extraordinary mechanical properties and self‐healing performances of DTPU elastomers were related to the synergistic effect of oxime‐carbamate bonds in the main chain and thiourethane bonds in the chemical cross‐linked sites. The existence of dynamic cross‐linked points not only optimized the mechanical properties of DTPU but also provided support for the reversible cleavage and formation of oxime carbamate bond, thus endowing DTPU with efficient self‐healing performance and recyclability. After self‐healing at mild temperatures for 6 h, the self‐healed DTPU elastomers had a tensile strength of 30.27 MPa and a self‐healing efficiency of 95.5%. After multiple hot‐pressing, the original mechanical strength of DTPU was restored to over 100%, exhibiting excellent recyclable characteristics. Additionally, strain sensors based on self‐healing flexible elastomers were fabricated by introducing conductive carbon nanotubes. The strain sensors maintained their electrical conductivity after 3 times self‐healing, demonstrating great potential in healable flexible electronics.

Tailored engineering of zinc carbide triggered by N‐enriched carbon nanotubes for prospective water splitting

AbstractFor practical H2 generation, it is currently difficult to create modules for electrochemical water splitting that are efficient and inexpensive over a broad pH range. In this study, a novel ZnC8@NCNT electrocatalyst is fabricated via simple pyrolysis of melamine with zinc chloride and carbon nanotubes (CNTs). The self‐assembled hybrid material was examined to catalyze the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline pH range, and the ZnC8@NCNT responds with a lower OER overpotential of 245 mV, and smaller Tafel slope of 50.0 mV dec−1 with the turnover frequency (TOF) of 0.67 s−1 due to its unique structure. The HER response of the generated material is quite satisfactory with an overpotential of 223 mV and a Tafel value of 107 mV dec−1. The fabricated material supported by conductive CNTs increases the catalytic reactivity due to the synergistic manner, which is superior in performance as a cutting‐edge catalyst for water electrolysis in an electrolytic cell. Furthermore, ZnC8@NCNT establishes as a cost‐effective alternative to expensive Ir, Pt, Pd, and Ru‐based catalysts.

Trifunctional catalyst of FeCo,N-doped mixed-dimensional carbon for the high-performance zinc-air flow battery

Exploring efficient and highly stable non-precious metal trifunctional catalysts is imperative for the practical application of zinc-air flow batteries (ZAFBs) and overall water splitting (OWS). Herein, the FeCo and nitrogen-rich codoped one-dimensional carbon nanotubes cross-interpenetrated with birdhouse-like carbon nanosheets in mixed-dimensional carbon structure (FeCo,N-MDC) is constructed by a facile and universal method. Benefiting from the merits of hyper-dispersed FeCo-N/Ox and FeCo alloy active sites, high density of pyridine and graphitic nitrogen, ultra-high conducting carbon nanotubes, large surface area, and massive mass transfer channels can synergistically promote multifunctional catalysis. The resulting FeCo,N-MDC exhibits superior trifunctional activities with onset potential and half-wave potential of 0.994 V and 0.861 V for oxygen reduction reaction in 0.1 M KOH, oxygen evolution reaction and hydrogen evolution reaction overpotentials of 0.341 V and 0.272 V at 10 mA·cm−2 in 1 M KOH, respectively, and have long electrochemical stability. Moreover, the FeCo,N-MDC-based ZAFB has an open-circuit voltage of 1.517 V, a specific capacity of 808 mAh·g−1, the remarkable running stability for 300 h, which surpassed that of commercial Pt/C + RuO2 hybrid-driven device. Additionally, the hydrophilic FeCo,N-MDC, as both the anode and cathode electrodes, also display a hydrolysis reaction voltage of 1.603 V to deliver a current density of 10 mA·cm−2 and outstanding durability. What is more, the continuously mass-produced FeCo,N-MDC, and the alternative CoFe, N-MDC catalysts exhibit excellent performance in the same water-solvent environment. This effort presents a facile strategy for rationally designing economical and efficient mixed-dimensional catalysts for zinc-air flow batteries and more energy devices.

Influence mechanism of functionalization of CNTs on the thermal transport property of their nanofluids

Carbon nanotube (CNT) nanofluids have promising application prospects as the working fluids in energy and power systems due to their prominent thermal properties, while the poor stability of CNT nanofluids is one of the biggest obstacles to their practical application. The addition of functional groups on CNTs is a good method to improve the dispersion of CNT nanofluids, while the influence mechanism of this strategy on the thermal transport property is not clear. In this work, the thermal conductivities of CNT, CNT-OH, and CNT-COOH nanofluids were investigated by experiments and molecular dynamics (MD) simulations to reveal the influence mechanism of functionalization on the thermal transport ability of CNT nanofluids. Both experimental measurements and MD simulations indicate the significant suppression of functionalization on the thermal transport property of CNT nanofluids. Furthermore, the influence mechanism of functional groups on the thermal conductivity of CNT nanofluids has been revealed by analyzing the effect of the thermal conductivities of CNTs, the formation of hydrogen bonds, the mean square displacement of water molecules, and the interlayer thermal resistance of CNT and water. This work is helpful to the utilization of CNT nanofluids as working fluids in energy systems.

Scalable, roll-to-roll manufacturing of multiscale nanoparticle/fiber composites using electrophoretic deposition: Novel multifunctional in situ sensing applications

Multiscale composites, where traditional fiber reinforcements are combined with nanoscale reinforcements, have emerged as multifunctional materials and have found potential for in situ strain and damage sensing, and energy harvesting/storage applications. Critical to the advancement of future applications is the development of manufacturing techniques that are industrially scalable. Electrophoretic deposition (EPD) can uniformly coat functionalized nanoparticles, such as carbon nanotubes (CNT), on conductive and non-conductive fiber substrates, producing multiscale composites with controlled microstructures and functional properties. In this research, a pilot-scale roll-to-roll EPD system is developed to continuously manufacture CNT-integrated fabrics for in situ sensing applications. Based on fundamental knowledge of CNT deposition mechanisms, key experiments are conducted to determine electrode configurations to optimize deposition yield in the roll-to-roll process. Functionalized CNTs are then deposited on 4–6 m long continuous rolls of randomly oriented non-woven glass fiber veil with different areal weights, and the CNTs form a continuous, conductive fiber-level coating. The thin and open fabric microstructure allows embedded sensors that are minimally invasive to the composite structure and allow ultraviolet (UV) light transmittance for use with UV-curable resins. The electrically conductive CNT network created on the fabric allows for the integration of sensing functionality. Short beam specimens with the CNT sensors embedded at the midplane showed no deterioration in strength. Multiple functionalities, including strain sensing and flow/UV cure monitoring during vacuum infusion are demonstrated. Sensors tested under flexural loading demonstrated sensitivity in tension and compression, and during resin infusion, the sensors could track resin flow and cure progression.

Nanoscale Dispersion of Carbon Nanotubes in a Metal Matrix to Boost Thermal and Electrical Conductivity via Facile Ball Milling Techniques.

Carbon nanotube (CNT)/metal composites have attracted much attention due to their enhanced electrical and thermal performance. How to achieve the scalable fabrication of composites with efficient dispersion of CNTs to boost their performance remains a challenge for their wide realistic applications. Herein, the nanoscale dispersion of CNTs in the Stannum (Sn) matrix to boost thermal and electrical conductivity via facile ball milling techniques was demonstrated. The results revealed that CNTs were tightly attached to metal Sn, resulting in a much lower resistivity than that of bare Sn. The resistivity of Sn with 1 wt.% and 2 wt.% CNTs was 0.087 mΩ·cm and 0.056 mΩ·cm, respectively. The theoretical calculation showed that there was an electronic state near the Fermi level, suggesting its electrical conductivity had been improved to a certain extent. In addition, the thermal conductivity of Sn with 2 wt.% CNTs was 1.255 W·m-1·K-1. Moreover, Young's modulus of the composites with CNTs mass fraction of 10 wt.% had low values (0.933 MPa) under low strain conditions, indicating the composite shows good potential for various applications with different flexible requirements. The good electrical and thermal conductive CNT networks were formed in the metal matrix via facile ball milling techniques. This strategy can provide guidance for designing high-performance metal samples and holds a broad application potential in electronic packaging and other fields.