Structure Of Carbon Nanotubes Research Articles

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.

Revealing the Mechanism Underlying 3D-AFM Imaging of Suspended Structures by Experiments and Simulations.

The invention of 3D atomic force microscopy (3D-AFM) has enabled visualizing subnanoscale 3D hydration structures. Meanwhile, its applications to imaging flexible molecular chains have started to be experimentally explored. However, the validity and principle of such imaging have yet to be clarified by comparing experiments and simulations or cross-observations with an alternative technique. Such studies are impeded by the lack of an appropriate model. Here, this difficulty is overcome by fabricating 3D carbon nanotube (CNT) structures flexible enough for 3D-AFM, large enough for scanning electron microscopy (SEM), and simple enough for simulations. SEM and 3D-AFM observations of the same model provide unambiguous evidence to support the possibility of imaging overlapped nanostructures, such as suspended CNT and underlying platinum (Pt) nanodots. Langevin dynamics simulations of such 3D-AFM imaging clarify the imaging mechanism, where the flexible CNT is laterally displaced to allow the AFM probe access to the underlying structures. These results consistently show that 3D-AFM images are affected by the friction between the CNT and AFM nanoprobe, yet it can be significantly suppressed by oscillating the cantilever. This study reinforces the theoretical basis of 3D-AFM for imaging various 3D self-organizing systems in diverse fields, from life sciences to interface sciences.

Enhancing structural integrity and adsorption performance of carbon nanotube buckypaper for water remediation through innovative densification strategy

The transformation of individual carbon nanotubes (CNTs) into buckypaper often results in random organization, leading to gaps or pores between them. These gaps act as flaws, reducing the overall properties of the bulk CNT structure. This study presents an advanced technique for densifying the structure by filling the gaps to tackle this issue. To achieve this, smaller multi-walled carbon nanotubes (MWCNTs) were employed to fill the gaps in the buckypaper composed of larger MWCNTs. This approach resulted in a significant improvement in the physical properties of the structure. The resulting hybrid buckypaper was thoroughly characterized using various techniques, including scanning electron microscopy, Raman spectroscopy, BET, XRD, and thermogravimetric analysis. The findings of this study demonstrated notable enhancements in the packing density, specific surface area, and tensile strength of the hybrid buckypaper, with improvements of 31.38 %, 63 %, and 20 %, respectively. Furthermore, the hybrid buckypaper proved to be an effective adsorbent for removing methylene blue dye from wastewater, exhibiting an impressive adsorption efficiency of 99.53 %. The absence of sludge impurities due to its high mechanical strength, combined with its superior rejuvenation capacity during multiple uses encourages cleaner and efficient water treatment system.

Analysis of Carbon Materials with Infrared Photoacoustic Spectroscopy.

Measurement of infrared spectroscopy has emerged as a significant challenge for carbon materials due to the sampling problem. To overcome this issue, in this work, we performed measurements of IR spectra for carbon materials including C60, C70, diamond powders, graphene, and carbon nanotubes (CNTs) using the photoacoustic spectroscopy (PAS) technique; for comparison, the vibrational patterns of these materials were also studied with a conventional transmission method, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, or Raman spectroscopy. We found that the IR photoacoustic spectroscopy (IR-PAS) scheme worked successfully for these carbon materials, offering advantages in sampling. Interestingly, the profiles of IR-PAS spectra for graphene and CNTs exhibit negative bands using carbon black as the reference; the negative spectral information may provide valuable knowledge about the storage energy, production, structure, defect, or impurity of graphene and CNTs. Thus, this approach may open a new avenue for analyzing carbon materials.

Kinetics insights into size effects of carbon nanotubes’ growth and their supported platinum catalysts for 4,6-dinitroresorcinol hydrogenation

Size effects are a well-documented phenomenon in heterogeneous catalysis, typically attributed to alterations in geometric and electronic properties. In this study, we investigate the influence of catalyst size in the preparation of carbon nanotube (CNT) and the hydrogenation of 4,6-dinitroresorcinol (DNR) using Fe2O3 and Pt catalysts, respectively. Various Fe2O3/Al2O3 catalysts were synthesized for CNT growth through catalytic chemical vapor deposition. Our findings reveal a significant influence of Fe2O3 nanoparticle size on the structure and yield of CNT. Specifically, CNT produced with Fe2O3/Al2O3 containing 28% (mass) Fe loading exhibits abundant surface defects, an increased area for metal-particle immobilization, and a high carbon yield. This makes it a promising candidate for DNR hydrogenation. Utilizing this catalyst support, we further investigate the size effects of Pt nanoparticles on DNR hydrogenation. Larger Pt catalysts demonstrate a preference for 4,6-diaminoresorcinol generation at (1 0 0) sites, whereas smaller Pt catalysts are more susceptible to electronic properties. The kinetics insights obtained from this study have the potential to pave the way for the development of more efficient catalysts for both CNT synthesis and DNR hydrogenation.

Robust and Versatile Heterostructured Carbon Nanocomposites with Diverse Adaptability to Harsh Environments

AbstractIn carbon allotropes, interfacial engineering of various sp2 nanocarbon building blocks has shown great promise in designing and fabricating creative nanocarbon assemblies with novel structural and functional properties. Here, a robust, flexible, metal‐like heterostructured carbon nanotube (CNT) film formed of amorphous graphene nanosheets (AGNs) on CNT networked film is demonstrated, presenting a sp3‐sp2 dominated interfacial heterostructure. Extensive characterization reveals that AGN exhibits a complete absence of long‐range periodicity with twisty six‐member rings. Such 2D graphene mailed 1D CNT structure endows the heterostructured carbon nanocomposite film with a combination of unique properties, including surface nano‐flattening (flatness fourfold of the raw CNT film), excellent anti‐wear performance, greatly enhanced modulus (enhanced by 400%), hardness (enhanced by 300 times), and conductivity (enhanced by 270%). Unlike conventional carbon‐based materials, such flexible films show distinct substantial deformability and rapid resilience over wide temperatures (−196–≈1300 °C), which facilitate the design of new‐concept lightweight high‐temperature resistant and shape‐transformable materials for advanced aerospace applications under extreme conditions.

Electro- and Thermophysical Properties of Organosilicon Elastomers Modified with Carbon Nanotubes and Microscale Metallic Structures

Electro- and Thermophysical Properties of Organosilicon Elastomers Modified with Carbon Nanotubes and Microscale Metallic Structures

Effect of Crystallinity on the Field Emission Characteristics of Carbon Nanotube Grown on W-Co Bimetallic Catalyst.

Carbon nanotube (CNT) is an excellent field emission material. However, uniformity and stability are the key issues hampering its device application. In this work, a bimetallic W-Co alloy was adopted as the catalyst of CNT in chemical vapor deposition process. The high melting point and stable crystal structure of W-Co helps to increase the grown CNT diameter uniformity and homogeneous crystal structure. High-crystallinity CNTs were grown on the W-Co bimetallic catalyst. Its field emission characteristics demonstrated a low turn-on field, high current density, stable current stability, and uniform emission distribution. The Fowler-Nordheim (FN) and Seppen-Katamuki (SK) analyses revealed that the CNT grown on the W-Co catalyst has a relatively low work function and high field enhancement factor. The high crystallinity and homogeneous crystal structure of CNT also reduce the body resistance and increase the emission current stability and maximum current. The result provides a way to synthesis a high-quality CNT field emitter, which will accelerate the development of cold cathode vacuum electronic device application.

Exploration of the photothermal role of curcumin-loaded targeted carbon nanotubes as a potential therapy for melanoma cancer

In this research, the hydrophilic structure of multi-walled carbon nanotubes (MWCNTs) was modified by synthesizing polycitric acid (PCA) and attaching folic acid (FA) to create MWCNT–PCA–FA. This modified nanocomplex was utilized as a carrier for the lipophilic compound curcumin (Cur). Characterization techniques including TGA, TEM, and UV–visible spectrophotometry were used to analyze the nanocomplex. The mechanism of cancer cell death induced by MWCNT–PCA–FA was studied extensively using the MTT assay, colony formation analysis, cell cycle assessment via flow cytometry, and apoptosis studies. Furthermore, we assessed the antitumor efficacy of these targeted nanocomplexes following exposure to laser radiation. The results showed that the nanocomposites and free Cur had significant toxicity on melanoma cancer cells (B16F10 cells) while having minimal impact on normal cells (NHDF cells). This selectivity for cancerous cells demonstrates the potential of these compounds as therapeutic agents. Furthermore, MWCNT–PCA–FA/Cur showed superior cytotoxicity compared to free Cur alone. Colony formation studies confirmed these results. The researchers found that MWCNT–FA–PCA/Cur effectively induced programmed cell death. In photothermal analysis, MWCNT–PCA–FA/Cur combined with laser treatment achieved the highest mortality rate. These promising results suggest that this multifunctional therapeutic nanoplatform holds the potential for combination cancer therapies that utilize various established therapeutic methods.

Highly Sensitive Weaving Sensor of Hybrid Graphene Nanoribbons and Carbon Nanotubes for Enhanced Pressure Sensing Function.

Carbon nanotubes (CNTs) hold great promise in next-generation sensors because of their remarkable physical properties. Yet, maintaining precise stacking configurations of CNTs to make full use of their remarkable properties is challenging because of their susceptibility to spontaneous reconstruction. Inspired by the weaving technology, we propose a CNT-graphene nanoribbon hybrid woven model that can maintain the specific structure of CNTs to achieve their elaborately designed function. In this study, comprehensive molecular dynamics simulations are carried out to investigate the thermal stability of the CNT-graphene hybrid woven model, as well as their potential for pressure sensing applications by utilizing the unique response of thermal transport to mechanical deformation at heterojunctions. The thermal stability is sensitive to the size of the graphene nanoribbon, and the woven structure remains stable from 200-500 K when its width is greater than 2.0 nm. Moreover, it is exciting that the sensors are effective at predicting the shapes of externally loaded objects through the analysis of the thermal conductivity distribution, which can be derived from the relationship between the thermal conduction and the pressure. Our findings shed light on the bottom-up functional design of nanomaterials and expand wider applications of high-performance nanosensors in other related fields.

Microstructural evolution effects on the density of carbon nanotube fibers

In this study, we investigate structural change in wet-spun carbon nanotube (CNT) fibers and explore the resulting changes in density and tensile strength. Given the presence of chlorosulfonic acid (CSA) inside the fiber and the evolution of tubular shape, the difference between the experimental density of CNT fibers and the theoretical density of individual CNTs can be reasonably approximated. During the heat treatment of pristine CNT fibers at 1400 °C, the capillary force induced by removal of CSA between or inside CNTs leads to the polygonization of the circumference of individual nanotubes. This morphological transformation results in the improved tensile strength and increased density by enlarging the contact area between CNTs and reducing the occupied volume. The demonstration of correlation between CNT structure and density can offer insights into the manufacturing and applications of high-performance CNT fibers.

Trisodium phosphate-loaded magnesium‑aluminum layered double hydroxides/oxidized-multiwalled carbon nanotubes self-assembled 2D-nanohybrid for designing a multifunctional smart epoxy nanocomposite

In this study, a hybrid nanomaterial based on layered double hydroxides (LDH) and multi-walled carbon nanotubes (MWCN) was fabricated using a co-precipitation method. Trisodium phosphate (TP) was loaded into the designed nanocarrier to enhance the corrosion resistance of mild steel in 3.5 wt% NaCl media. Fourier transform infrared (FT-IR) spectroscopy, Raman, and X-ray diffraction (XRD) analyses were carried out to investigate the magnesium‑aluminum layered double hydroxides/oxidized-multiwalled carbon nanotubes (Mg-AL-LDH/O-MWCN) structure and morphology before and after loading of trisodium phosphate. Furthermore, the nanocarrier inhibition capability was evaluated through electrochemical impedance spectroscopy (EIS), polarization, and field emission-scanning electron microscopy (FE-SEM) techniques. Electrochemical impedance spectroscopy (EIS) was also employed to estimate the anticorrosion properties of the epoxy coating loaded with TP-LDH/O-MWCN. The EIS evaluation of the intact coating revealed the impedance at the lowest frequency (|Z|0.01 Hz) of about 109 Ω.cm2 after 42 days of immersion for the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes@epoxy (TP-LDH/O-MWCN@EP) sample and the lowest value of breakpoint frequency was obtained for this sample (fb = 0.063 Hz). These findings prove the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes (TP-LDH/O-MWCN) particles' effectiveness in the epoxy coating water/ion barrier function enhancement. EIS results indicated the enhancement of the charge transfer resistance (Rct) of the scratched coatings, from 65.97 kΩ.cm2 for the pure epoxy (EP) sample to 94.87 kΩ.cm2 for the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes@epoxy (TP-LDH/O-MWCN@EP) sample, revealing the self-repairing behavior of the designed coating. In addition, the adhesion properties of the samples coated with LDH/O-MWCN@EP and TP-LDH/O-MWCN@EP were studied by pull-off and cathodic disbonding tests, leading to a 33% reduction in adhesion loss and a 52.23% reduction in the diameter of cathodic delamination. The tensile test conducted on the samples indicated an increase in the ultimate tensile strength (σUTS), elongation break (Ɛb), and toughness values by 188%, 223%, and 800%, respectively, in comparison with the pure epoxy (EP) sample.

Generalized strategy to construct multifunctional inorganic nanomaterials/silicone rubber composite aerogels: Taking CNTs as an example for smart sensing

The structure and characteristics of carbon nanotubes (CNTs) aerogel (CNTA) make it capable of only compression, lacking the necessary toughness, flexural, and tensile properties. These limitations restrict its application. To overcome these obstacles, this study employed an interface modification and the Pickering emulsion strategy, using water-soluble CNTs as the continuous phase while silicone rubber (SR) as the dispersed phase, to successfully achieve the organic–inorganic combination and prepare the SR-CNTs composite aerogel (SRC). Benefiting from the synergistic effect of the “soft-hard” phase combination of SR (soft) and CNTs (hard), SRC exhibited good conductivity (1.23 S/m) and superior multi-axial mechanical properties such as compression (90 %), bending (360°), twisting (360°), and stretching (110 %), making it broad prospects in the field of flexible sensing. Importantly, the strategy employed in this study offers an innovative approach for a transition from low-dimensional nanomaterials to three-dimensional macroscopic overall structures. This approach effectively addresses common issues in traditional aerogel materials, such as mechanical brittleness and structural instability, which also allows for functionalization and customization, opening up new possibilities for the research and application of high-performance aerogels.

Multi-electron transfer mechanism and band structures of CNTs in MOF-derived CNTs/Co hybrids for enhanced electromagnetic wave absorption property

Metal-organic framework (MOF)-derived magnetic metal/carbon nanocomposites have received widespread attention for electromagnetic wave (EMW) absorption. The present study introduces a novel approach to MOF composite material design by constructing composites modified with carbon nanotubes (CNTs) and magnetic Co nanoparticles. The carbon confinement effect in CNT/Co not only regulates the electronic structure of Co-C bonds, but also maintains the redox cycle of Co0/2→Co3+→Co0/2+, improving electronic activity and exhibiting synergistic integration characteristics of efficient electromagnetic wave absorption. Particularly, the maximum reflection loss (RLmin) of CNTs/Co-900 reached −52.7 dB at 4.67 GHz in the case of an absorber thickness of 1.6 mm. The excellent microwave absorption performance may be attributed to the interwoven structure formed by novel ZIF-67, CNTs, and Co metal nanoparticles and the double loss of magnetic Co and dielectric CNTs. In addition, the band gap of CNTs was calculated to be Eg = 0.27 eV by the semi-empirical tight-binding method with DFTB+. It is confirmed that CNTs have high electron migration ability, which is beneficial to conductive loss. It is confirmed that CNTs have high electron migration ability, which is beneficial to conductive loss. This study provides a novel strategy for the development of metal-organic framework-based magnetic particles/carbon nanocomposites for electromagnetic wave absorption.

On comparative analysis of graph entropies of symmetrical carbon nanotube Y-junctions

Entropy is crucial in statistical mechanics, thermodynamics, and information theory as it measures a system’s level of randomness or disorder. Entropy is widely used in mathematical chemistry and computational physics to predict the behavior of a system under various conditions. Among numerous carbon nanotube structures, three-terminal carbon nanotube junctions are important structures not only for electrical but also for mechanical appliances. Recently, significant attention has been given to the understanding of carbon nanotube junctions. This research paper focuses on calculating graph entropies based on Zagreb indices for symmetrical single-walled armchair carbon nanotube Y − junctions and comparing the index-entropies of these junctions. The study aims to demonstrate the behavior of the nanotube Y − junctions by adding atoms at the end of the tubes.

A novel flexible electrochemical sensor with multi-level carbon nano-array for in-situ real-time monitoring of H2O2 secreted by cells

Developing ultra-sensitive sensors for in-situ real-time monitoring of low-level cell secretions is of paramount importance in understanding various biological processes, and it is still a challenge. Herein, for the first time, we constructed a novel flexible Au-Co@C-CNT/CC sensing electrode with nano-array structures by in-situ synthesis, catalytic pyrolysis and electrochemical deposition, and successfully realized the real-time monitoring of H2O2 released by cells. The 3D leaf-like structure of the electrode not only provided a large electroactive surface area (7.66 cm2) but also exhibited a microvilli structure of carbon nanotubes (CNT) on the surface, which further enhanced the presence of active sites. Moreover, the Co-Nx sites generated by catalytic pyrolysis can promote the adsorption and catalysis of H2O2 on the surface of sensing electrode. The introduction of Au NPs facilitated the transfer of electrons, thereby enhancing the electrical conductivity and electrocatalytic performance of Au-Co@C-CNT/CC. Benefiting from these unique superiorities, this sensing platform displayed excellent performance for H2O2 determination with a wide linear range (10–27080 μM) and low detection limit (0.13 μM). Notably, the good biocompatibility and flexibility of this sensing platform allowed direct culture of human lung cancer cells (A549 cells) on the electrodes, which can realize dynamic in-situ real-time detection of H2O2 released by cells, showing great potential in the diagnosis of related diseases.

A universal synthesis strategy for facile and scalable of magnetic biochar composite materials for PMS activation: Catalytic mechanisms

Biochar-based catalysts have shown great promise for application in AOPs due to their wide source and good performance, while its development is limited by its complicated preparation process and large variation in performance. Herein, a series of magnetic biochar composites(Fe@NC-XX) based on different biomass (duckweed, shrimp shell, peanut shell, corncob, and pomelo peel) were fabricated via one-pot pyrolysis method. The removal of sulfadiazine (SDZ) by all materials reached more than 90% within 20 min. The characterization results indicated that the special structure of Fe encapsulated in nitrogen-doped carbon nanotubes (CNTs) was the main reason why this approach is not limited to specific biomass. Acts as a catalytic center, Fe catalyzes the formation of CNTs during annealing. Meanwhile, graphene sheets and carbon nanoparticles formed by melamine and biomass decomposition migrate to the nucleus surface to form a hollow structure of CNTs. In addition, the results of quenching experiments and ESR tests elucidated that surface-bound radicals accumulated on the surface of CNTs, which can remarkably boost the efficient removal of SDZ. Consequently, the synthetic strategy of Fe nanoparticles anchored in N-doped CNTs that are not selective for biomass provides a new pathway for a universal synthesis method of biochar-based catalysts.

Insights into the Nucleation and Structure of Lignin-Based Carbon Nanotubes Synthesized Using Iron via Floating Catalyst Chemical Vapor Deposition

Insights into the Nucleation and Structure of Lignin-Based Carbon Nanotubes Synthesized Using Iron via Floating Catalyst Chemical Vapor Deposition