Structure Of Carbon Nanotubes Research Articles

Radiation generation from an array of magnetized anharmonic carbon nanotubes

An investigation into second-harmonic generation from magnetized anharmonic carbon nanotubes (CNTs) mounted on a silica substrate is conducted using a Gaussian laser pulse with modulated amplitude. An intense amplitude-modulated laser pulse incident on the array of CNTs displaces their electrons generating a restoration force. This restoration force is the nonlinear function of displacement of electrons, which ensures the anharmonic behavior of CNTs. Using the paraxial ray approximation, the nonlinear interaction of the incident pulse with CNTs is expressed in terms of a wave equation derived using the perturbative technique. The nonlinear current at second-harmonic frequency arises due to the perturbation of the electron density of CNTs by the ponderomotive force exerted on them by an incident pulse. Numerical outcomes validate the enhanced efficiency of the generated harmonic when considering the phenomenon of self-focusing. With the substantial optical nonlinearities of an anharmonic CNT structure, the plasmon resonance is broadened and high efficiency in generating harmonics is attained. It is seen that the augmenting of the amplitude-modulated parameter of the pulse and the external magnetic field strength enhances system nonlinearity, resulting in increased amplitude of generated second harmonics. Additionally, the effect of the heating rate of CNTs on the efficiency of the generated harmonic is also discussed.

High-Performance Photodetectors Based on Suspended Ultralong Carbon Nanotubes.

Photodetectors are in huge demand in multiple fields, such as remote sensing, chemical detection, security, and medical imaging. Carbon nanotubes (CNTs) are promising candidates for high-performance photodetectors due to their extraordinary optical and electrical properties. However, the performance of previously reported CNT-based photodetectors is far from the intrinsic photoelectrical properties of CNTs because of the noncontinuous lengths, structural defects, and unsatisfactory structural design of the previously used short CNTs. The key to improving the performance of CNT-based photodetectors is to increase the length and structural quality of the CNTs. Herein, high-performance photodetectors were fabricated by using high-density suspended ultralong CNTs (SUCNTs). The suspended structures of ultralong CNTs not only reduced the electron-phonon interactions generated by substrates but also largely avoided bolometric effects through efficient heat dissipation. Moreover, the characteristics of high areal density and defect-free structures of SUCNTs could increase the effective absorption areas and improve their carrier mobility, resulting in enhanced photoconductive responses. Consequently, compared with the nonsuspended short CNTs, the SUCNT-based photodetectors achieved significantly improved photodetection performance, such as high responsivity (0.181 A W-1), detectivity (1.20 × 109 cm Hz1/2 W-1), ultrafast response (0.13 ms), and broad detection range (405-850 nm).

Designing a Microstructure of NiCo-LDH@CNTs@Carbon Foam for Efficient Electromagnetic Wave Absorption and Excellent Environmental Tolerance.

The constantly evolving environment imposes increasingly stringent demands on the mechanical qualities of materials employed for absorbing electromagnetic waves (EMWs). Therefore, there is an urgent need for advanced materials capable of efficiently absorbing EMWs and withstanding harsh electromagnetic conditions. In this study, the electrodeposition method was effectively used to synthesize nickel-cobalt layered double hydroxides (NiCo-LDHs) in a controlled manner on a composite structure of carbon nanotubes and carbon foam, creating an exquisite construction. The manipulation of the electrodeposition time facilitated the regulation of the density of the layered structure within the composite material, thereby significantly enhancing its polarization relaxation performance. Increased defect sites and interface polarization enhance impedance matching and the attenuation constant, resulting in greatly improved absorption performance. The optimized sample demonstrated exceptional wave-absorbing performance in comparative experimental analysis, attaining a maximum reflection loss of -58.18 dB. It also has an effective absorption bandwidth of 5.36 GHz at a wavelength of 2.28 mm. The exceptional isolation effect of LDH, coupled with the outstanding insulation ability of the porous carbon skeleton, confers remarkable corrosion resistance and thermal insulation performance on the composite material. Hence, this discovery offers novel insights into designing environmentally tolerant absorbent materials.

Synthesis of Ultrahigh-Purity (6,5) Carbon Nanotubes Using a Trimetallic Catalyst.

Chirality-controlled synthesis of carbon nanotubes (CNTs) is one of the ultimate goals in the field of nanotube synthesis. At present, direct synthesis achieving a purity of over 90%, which can be called single-chirality synthesis, has been achieved for only two types of chiralities: (14,4) and (12,6) CNTs. Here, we realized an ultrahigh-purity (∼95.8%) synthesis of (6,5) CNTs with a trimetallic catalyst NiSnFe. Partial formation of Ni3Sn crystals was found within the NiSnFe nanoparticles. The activation energy for the selective growth of (6,5) CNTs decreased owing to the formation of Ni3Sn crystals, resulting in the high-purity synthesis of (6,5) CNTs. Transmission electron microscopy (TEM) reveals that one-dimensional (1D) crystals of periodic strip lines with 8.8 Å spacing are formed within the as-grown ultrahigh-purity (6,5) CNTs, which are well-matched with the simulated TEM image of closely packed 37 (6,5) CNTs with 2.8 Å intertube distance, indicating the direct formation of chirality-pure (6,5)-CNT bundle structures. The photoluminescence (PL) lifetime increases more than 20 times by the formation of chirality-pure bundle structures of (6,5) CNTs compared to that of isolated (6,5) CNTs. This can be explained by exciton delocalization or intertube excitons within bundle structures of chirality-pure (6,5) CNTs.

Self-Supporting Hierarchical Carbon Network Loaded with NiW Nanoparticles for Efficient Hydrogen Evolution.

Water splitting technology can convert renewable energies such as solar and wind into hydrogen energy, which is key to achieving a low-carbon hydrogen economy cycle. However, Pt-based catalysts for hydrogen evolution reaction (HER) are too expensive, thus it needs to develop efficient non-noble metal catalysts as alternatives. Herein, Ni-BDC-loaded carbon cloth (CC) is co-pyrolyzed with urea to obtain a composite structure of carbon nanotubes (CNT) and porous carbon (PC) embedded with W-doped Ni nanoparticles on CC, resulting in NiW-CNT/PC/CC. Benefiting from the synergistic effect between Ni and W, the high conductivity of CNT, and the high mass transfer rate of PC, NiW-CNT/PC/CC exhibits excellent HER activity in KOH, which only requires a low overpotential of 45mV to drive a current density of 10mAcm-2 with stability exceeding 40 h. Simulation calculations confirm that the W doping in metal Ni can optimize its electronic structure by lowering the d-band center and weakening hydrogen adsorption, thus reducing its HER barrier.

Preparation and Assembly of Carbon Nanotube/Silica Core-Shell Nanowires to Realize High-Density and Well-Aligned Nanotube Arrays with Uniform and Tunable Pitch

This study introduces a novel method to fabricate high-density, well-aligned arrays of carbon nanotubes (CNTs) with tunable pitch, utilizing a core-shell nanowire structure of CNTs and silica. The approach involves a modified Stober process to achieve controlled deposition of silicon dioxide around individual CNTs, forming robust core-shell nanowires. By optimizing the Stober process, the shell size can be precisely controlled down to sub 10nm scale while maintaining the individualized nature of the CNTs. Densely packed and precisely aligned CNT arrays are created using Langmuir-Schaefer process. After assembly, the silica shell, acting as a physical spacer, can be easily removed by HF etching, exposing the CNTs while maintaining their alignment. The developed high-density, well-aligned CNT arrays with tunable pitch show significant promise for applications in nanoelectronics, sensors, and other emerging technologies. This methodology offers a robust and scalable approach for CNT array fabrication, opening avenues for tailoring array properties to meet specific application requirements.

Water structures in tip-charged carbon nanotubes.

Carbon nanotubes (CNTs) have potential applications in separation membranes and nanofluidic devices. It is well known that the behavior of water molecules confined in CNTs is affected by surface functional groups and external electric fields, leading to structural changes. The understanding of these structural changes of water within various CNTs is crucial, particularly in the context of material separation. While there have been many investigations into the effects of individual specific functional groups, a comprehensive understanding of the effect of these functional groups and the electric fields they generate on water molecules remains elusive. In this study, we investigate the properties of water molecules in tip-charged CNTs of (8,8), (10,10), and (12,12) chiral vectors with positive charges at one tip and negative charges at the other tip. Abstraction of ionized functional groups as tip charges enables a comprehensive understanding that is independent of individual functional groups. The symmetrically arranged tip-charges spontaneously generate a strong and symmetric electric field in the CNTs. However, the strength and directionality of the electric field are non-uniform and complex. In the interiors of (8,8) and (10,10) tip-charged CNTs, helical and square structures, which have disturbances caused by the non-uniformity of the electric field, are observed. The properties of the water molecules differed significantly in the center of the CNTs and near positive and negative charges, despite the electric field symmetry. In (12,12) tip-charged CNTs with 12 charges, a local ring structure is observed in the vicinity of negative charges but not in the vicinity of positive charges. It is concluded that the water structures in tip-charged CNTs have different characteristics from those in plain CNTs under a uniform electric field.

Construction of porous graphene and network carbon nanotubes to develop high-performance and multifunctional carbon fiber composites

Structurally and functionally integrated carbon fiber reinforced polymer composites (CP) are indispensable in electronic devices, where the combination of brilliant mechanical properties, electromagnetic shielding properties and thermal management capabilities are required. Designing and optimizing the interface structure is an effective solution to the above problems. In this work, porous graphene and network carbon nanotubes were successfully integrated into CP. Graphene and carbon nanotubes form a crosslinked structure in which graphene improve the fiber/matrix interfacial bonding and carbon nanotubes enhance the matrix cohesion. Due to their synergistic enhancement, the tensile strength (183.00 ± 5.66 MPa) of graphene and carbon nanotubes reinforced CP (CG-CP) is increased by 65.85 % and the wear rate (1.19 × 10–13 ± 0.05 × 10−13 m3(N·m)−1) is reduced by 74.52 %. Further, the crosslinked structure of graphene and carbon nanotubes creates a high-conductivity and heat-conductive transmission channel, enabling CG-CP to achieve an electromagnetic interference shielding efficiency of up to 48.94 dB in the X-band and 52.62 dB in the Ku-band at a thickness of 0.3 mm, and a 20.98 % improvement of thermal conductivity (0.767 ± 0.002 W(m·K)−1), which simultaneously achieves excellent electromagnetic shielding performance and thermal management capability. The high-performance and multifunctional CG-CP offers a broad prospect regarding the application of advanced electronic devices.

Investigating Metric Dimension and Edge Metric Dimension of Hexagonal Boron Nitride and Carbon Nanotubes

When there is a difference in the distance between two vertices in a simple linked graph, then a vertex $x$ resolves both $u$ and $v$. If at least one vertex in $S$ distinguishes each pair of distinct vertices in $G$, then a set $S$ of vertices in $G$ is referred to as a resolving set. $G$'s metric dimension is the minimum number of vertices required in a resolving set. A subset $S$ of vertices in a simple connected graph is called an edge metric generator if each vertex can tell any two distinct edges $e_1$ and $e_2$ apart by their respective distances from each other. The edge metric dimension (EMD), denoted as $\mathrm{dim}_e(G)$, is the smallest cardinality of such a subset $S$ that serves as an edge metric generator for $G$. The primary objective of this study is to investigate the edge metric dimension (EMD) of hexagonal boron nitride and carbon nanotube structures.

Enhancement mechanisms of mechanical, electrical and thermal properties of carbon nanotube-copper composites: A review

Carbon nanotubes (CNTs), as potent reinforcements in composites, have demonstrated excellent strengthening effects when combined with copper in numerous recent studies. Challenges remain in the application of these composites and in fully leveraging the reinforcing capabilities of CNTs to achieve comprehensive performance enhancement. The performance of CNTs/Cu composites can be flexibly regulated owing to the unique structure and properties of CNTs. To achieve the fabrication of high-performance and diverse CNTs/Cu composites, a profound understanding of the reinforcement mechanisms of CNTs in the composites is essential, along with the consideration of key influencing factors on performance. This article provides a comprehensive overview of the reinforcement mechanisms of CNTs on the mechanical, electrical, and thermal properties of CNTs/Cu composites. Factors influencing the effectiveness of CNT reinforcement in composites are discussed, including the attributes and dispersion of CNTs, the architectures of composites, and the interface between CNTs and Cu. Furthermore, this study explores the role of CNTs in addressing the trade-off between high strength and high conductivity as well as between high strength and high ductility in the copper matrix.

Synergistic optimization of multifunctional properties in carbon fiber/phenolic composites by designing array carbon nanotubes structures on the surface of carbon fibers

Carbon fiber/phenolic resin composites have great potential application in the field of electronic information, where excellent structural-functional integration is required. In this work, the establishment of interfacial structures consisting of carbon nanotubes with different morphologies at the fiber/matrix interface is conducive to the further modulation of the mechanical, tribological, electromagnetic interference (EMI) shielding and thermal conductivity properties of carbon fiber/phenolic resin composites. Specially, array carbon nanotubes can deep into the resin matrix, effectively hindering crack extension, and constructing an electrically and thermally conductive network. Compared with the carbon fiber/phenolic composites, the tensile strength and modulus of elasticity (163.86 ± 9.60 MPa, 5.06 ± 0.25 GPa) of the array carbon nanotubes reinforced carbon fiber/phenolic composites were enhanced by 57.09 % and 22.22 %. The average friction coefficient and wear rate (0.20 ± 0.02, 1.11 × 10−13 ± 0.13 × 10−13 m3N−1m−1) were reduced by 39.39 % and 74.31 %. EMI shielding effectiveness up to 40 dB in the X-band at 0.4 mm sample thickness, diffusion coefficient (0.39 ± 0.003 mm2/s) and thermal conductivity (0.54 ± 0.004 W/(m K)) were enhanced by up to 14.37 % and 50.42 %. This study reveals the beneficial effects of morphological changes of carbon nanotubes on the design of interfacial structure, proposes the reinforcement mechanism of array carbon nanotubes, and opens up the prospect of carbon fiber/phenolic composites for electronic applications.

Biomass lignin as dispersion to substantially enhance carbon nanotubes thermoelectric converter for energy harvesting

Carbon nanotubes (CNTs) have attracted much attention as promising thermoelectric materials to harvest waste energy, however the agglomeration between nanotubes greatly limits their application. Despite various dispersants that have been devised to enhance the dispersion of CNTs, biomass lignin has been rarely employed to facilitate the dispersion of CNT for enhancing its TE properties. Herein, green lignin was incorporated with CNTs to synergistically improve the dispersion and TE properties of CNTs, in which π-π interactions between the aromatic ring structure of lignin and CNTs, as well as electrostatic charge brought by ionized groups of lignin promote the exfoliation of nanotubes and reduces CNTs entanglement. The well-dispersed structure of CNTs facilitates efficient charge transfer, and thereby enhances the thermoelectric properties. CNTs/lignin composite could reach a maximum power factor of 198.0 μW m−1K−2 at a lignin content of 11.8 wt%, which was then raised to 223.1 μW m−1K−2 with subsequent partial removal of lignin by alkali immersion treatment, higher than 98.6 μW m−1K−2 of pristine CNTs film. Furthermore, the flexible TE device with five pairs of CNTs/lignin and nickel wires generates a high power of 288 nW at ΔT = 30 K, demonstrating potential applications of lignin for sustainable energy harvesting.

Electronic properties of armchair & zigzag single-walled carbon nanotubes

This paper investigates the role of chirality and its impact on the electronic band structure in armchair and zigzag single-walled carbon nanotubes (SWCNTs). Simulating electronic band gaps for single-walled carbon nanotubes (SWCNTs) with various chiral indices has been done by using the tight-binding model. The increase in chirality results in an increase in the total number of bands in the electronic band structure. A study was conducted on the band gap at Fermi energy (E=0) and it was found that the electronic band structure in armchair and zigzag (SWCNTs) can be either metallic or semiconductor depending on chirality. The diameter of the tube and the band gap value are also provided. The effect of variations in the CNT channel length and oxide thickness on the gate capacitance and drain current of a single CNT have been analyzed. The results suggest that the simulated values are consistent with the theoretical values thus validating the results.

Facile Doping of 2,2,2-Trifluoroethanol to Single-Walled Carbon Nanotubes Electrodes for Durable Perovskite Solar Cells

Perovskite solar cells with an indium tin oxide (ITO)/SnO2/CH3NH3PbI3/Spiro-OMeTAD/2,2,2-trifluoroethanol (TFE) doped single-walled carbon nanotube (SWCNT) structure were developed by dropping TFE onto SWCNTs, which replaced the metal back electrode, and a conversion efficiency of 14.1% was achieved. Traditionally, acidic doping of the back electrode, SWCNT, has been challenging due to the potential damage it may cause to the perovskite layer. However, TFE has facilitated easy doping of SWCNT as the back electrode. The sheet resistance of the SWCNTs decreased and their ionization potential shifted to deeper levels, resulting in improved hole transport properties with a lower barrier to carrier transport. Furthermore, the Seebeck coefficient (S) increased from 34.5 μV/K to 73.1 μV/K when TFE was dropped instead of EtOH, indicating an enhancement in the behavior of p-type charge carriers. It was observed that hydrophilic substances adhered less to the SWCNT surface, and the formation of PbI2 was suppressed. These effects resulted in higher conversion efficiency and improved solar cell performance. Furthermore, the decrease in conversion efficiency after 260 days was suppressed, showing improved durability. The study suggests that combining SWCNTs and TFEs improves solar cell performance and stability.

Multifunctional basalt fiber reinforced polymer composites with in-situ damage self-sensing and temperature-sensitive behavior

In this work, a multifunctional basalt fiber reinforced polymer composite (BFRP) with damage self-sensing and temperature-sensitive behavior was developed. Firstly, carbon nanotubes (CNTs) were deposited on basalt fibers (BF) by electrostatic self-assembly. Then, strong shear forces were applied during melt mixing with polyarylene ether nitrile (PEN) to construct a structure of CNTs surrounding the BF (CSB). This CSB structure endowed the composite with a low percolation threshold (0.82 wt% CNTs), a high conductivity (1.53 × 10−2 S/m at 1.12 wt% CNTs) and enhanced mechanical properties. The combination of resistance and acoustic emission real-time measurements confirmed that the composite achieved an excellent damage self-sensing capability with a maximum gauge factor (GF) of 7.68. Moreover, the composite exhibited a temperature-sensitive behavior with a temperature coefficient of resistance (TCR) of 0.542 %/°C. This study provides a significant guidance for the development of multifunctional BFRP with damage self-sensing and temperature sensitive behavior.

Efficiency enhancement of novel ITO/ZnSe/CNTs thin film solar cell

This study presents a novel photovoltaic cell design utilizing a layered structure of Indium Tin Oxide (ITO), Zinc Selenide (ZnSe), and Carbon Nanotubes (CNTs) for enhanced solar energy conversion. We employed the Solar Cell Capacity Simulator (SCAPS-1D) to model and optimize the device under AM 1.5 spectrum conditions. Our simulations systematically investigated the influence of key parameters including layer thicknesses, doping concentrations, temperature, back contact work function, and parasitic resistances on cell performance. The optimized structure demonstrated a theoretical power conversion efficiency of 29.91%, with an open-circuit voltage (Voc) of 799 mV, a short-circuit current density (Jsc) of 43.49 mA/cm², and a fill factor (FF) of 86.02%. These promising results are attributed to the synergistic combination of CNTs' broad spectral absorption, ZnSe's effective charge separation, and optimized layer properties. We found that the CNT absorber layer's doping concentration significantly impacted cell performance, with an optimal value of 10¹⁷ cm⁻³. The ZnSe buffer layer thickness showed minimal effect on efficiency within the studied range. Temperature increases from 300 K to 400 K led to a significant efficiency drop from 33.97% to 24.65%, primarily due to Voc reduction. While these results represent idealized conditions and upper theoretical limits, they provide valuable insights for the potential of CNT-based solar cells. This study offers a roadmap for future experimental work in high-efficiency thin-film photovoltaics, highlighting the promise of novel material combinations and the importance of device architecture optimization.

Deep‐Learning‐Assisted Piezoresistive Intelligent Glove for Pressure Monitoring and Object Identification

AbstractThe array of tactile information processing capabilities is an important index for modern intelligent devices advancing toward a humanoid form, and it greatly improves the recognition of different objects in human‐computer interactions. Herein, a deep‐learning‐assisted intelligent grasping recognition system based on a piezoresistive sensing glove, hardware conditioning, and acquisition circuits, and a multibranch deep‐capsule network is reported. Owing to the multiscale 3D structure of carbon nanotube (CNTs)/carbon fiber (CFs) embedded in polydimethylsiloxane (PDMS), the piezoresistive sensing glove is highly sensitive to the pressure exerted by external objects. The acquired signals are reflected on a hand‐like background map, and a combination of multiple subgraphs is used to build the dataset. A multibranch deep‐capsule network is constructed to encode spatial information while realizing object recognition with an accuracy of 99.4%. Therefore, the proposed intelligent grasping recognition system possesses good human‐robot interaction capabilities, providing a new approach for the development of intelligent robots in the field of perceptual recognition applications.

Improvement of apparent IFSS and specific modulus of CNT yarns

Due to the high strength of carbon nanotubes (CNTs) significant effort has been devoted to incorporating them into fibers and composites. To maximize their potential in these areas, there must be strong interactions between the CNT structures and the matrix of the composite. For CNT yarn, progress in this area has been limited. In this work, we present a method for modifying CNT yarn which improves the apparent interfacial shear strength (IFSS) by up to 45 %, as measured by single yarn pullout testing. An ammonium peroxide mixture (APM) treatment method is used to modify the yarn, and this is followed by treatment with commercial sizing agents. A tensioned heat treatment method is also employed to limit the effect of APM treatment on strength and modulus. This method increased the specific modulus of CNT yarns by as much as 16 %. The combined heat and chemical treatments yield increases as high as 43 % in IFSS and 6 % in specific tensile modulus while tempering the decreases in specific tensile strength. The yarn is characterized by SEM, EDS and Raman spectroscopy to show surface carbon being removed from the yarn, seemingly without damaging the CNT structures in the yarn. The main mechanism for IFSS increase appears to be removal of non-graphitic material from the yarn and slight oxidation of the yarn surface. The increase seen in IFSS has the potential to improve the performance of CNT yarn/polymer matrix composites for aerospace applications.

Analysis of Performance of Additively Manufactured Reinforced Ablatives

This study investigates reentry conditions for Mars missions, focusing on extreme anaerobic heating. This work studies poly(ether ketone ketone) (PEKK), a high-performance thermoplastics polymer, in both small-scale laboratory and simulated oxyacetylene test bed conditions to eliminate low-performing polymeric materials. Previous research demonstrated PEKK’s superior ablation performance compared to poly(ether ether ketone) (PEEK) and polyetherimide. The aerothermal performance of neat PEKK can be further enhanced with reinforcement materials. This work explores PEKK composite materials reinforced with additives such as carbon nanotubes (CNTs), carbon fibers (CFs), and glass fibers (GFs). The CNT-reinforced (10%wt) PEKK exhibited the highest char yield (69%wt) during thermogravimetric analysis (TGA) in nitrogen, superior to the short CF-reinforced PEKK. Various CF and GF loadings (10% and 20%wt) were tested for their thermophysical and aerothermal performance. Oxyacetylene tests (OTBs) under fuel-rich conditions further validated the results. Except for 10% CF PEEK, the mass loss in OTB tests correlated with TGA and thermal diffusivity measurements. The addition of CF/GF in PEKK enhanced thermal effusivity, but it also led to significant swelling due to increased conductive flux and reduced ablated heat flux. Among the tested materials, CNT-reinforced PEKK displayed the highest char yield, lowest mass loss, and minimal swelling. The unique porous structure of CNTs minimized char expansion and erosion during the OTB tests, making a promising material for reentry flights.

Synergistic enhancement of strength and toughness of fiber-reinforced composites by constructing biomimetic intermittent porous structure

Achieving a balance between strength and toughness is a vital requirement for the development of high-performance fiber-reinforced composites. Inspired by nature, this study integrates biomimetic intermittent porous carbon nanotubes (PCNT) structure into the composite for synergistically enhancing its strength and toughness. It was found that the interfacial shear strength, interfacial fracture toughness, 45FBT tensile strength, and interlaminar fracture toughness of the intermittent porous structure-coated fiber/resin composites obtained significant increases of 63.4%, 107.7%, 31.2%, and 64.3% than the baseline composites, respectively. The strengthening effect was contributed by the synergistic enhancement of the interfacial bonding areas and mechanical interlocking morphologies, as well as the significant frictional stresses induced by the morphological mismatches between adjacent gaps. The toughening mechanism was associated with the micro-crack formation, the PCNT structure rupture, and the crack deflection during the crack propagation. This work provides a promising pathway to overcome the trade-off between strength and toughness.