Commercial Carbon Nanotubes Research Articles

Physical properties of industrially produced carbon nanotube yarns for use in structural nanocomposites

Industrially-produced carbon nanotube (CNT) networks are a promising base for high-performance, continuous CNT nanocomposites, motivating widespread use in research and application development. Floating catalyst chemical vapor deposition (FCCVD) is a scalable, widely-adopted approach for synthesis of CNT networks; however, FCCVD can yield networks with organic impurities which complicate their characterization and processing. Herein, we analyze two varieties of FCCVD-synthesized commercial CNT yarn to explore the effects of densification and purification as they relate to forming infiltrated polymer composites. First, the fluid permeabilities and porosities of neat roving and chemically-stretched CNT yarns (CSYs) are estimated and compared to gas adsorption studies, which suggest high-tenacity CSYs are largely impermeable, leading to dry-core composites when polymer infiltration is attempted. Next, the presence and effects of oxygen-rich amorphous carbon impurities in the CSYs are identified and found to exist at the scale of CNT bundles, wherein the amorphous carbon behaves like a hygroscopic polymer matrix in a composite. Removal of the amorphous carbon phase in a 130%-increase in specific surface area, as quantified by BET analysis, and a statistically significant reduction in tensile properties. We discuss challenges in estimating yarn alignment and crystallinity resulting from these factors, and place our results in context of past studies analyzing intrinsic organic coatings in FCCVD-synthesized CNT networks.

Introduction of bimetallic oxide-modified carbon nanotubes for boosting the energy storage performance of NiCo-LDH based in-plane micro-supercapacitors on paper

In-plane micro-supercapacitors (IMSCs) have greater promise for use in flexible wearable electronics than traditional stacked configurations due to their ease of integration and conformability. Nickel-cobalt layered double hydroxide (NiCo-LDH) has garnered significant interest as a stellar material for supercapacitors because of its affordable price, regular morphology, and high theoretical capacity. Unfortunately, the intrinsic poor conductivity of LDH materials prevents supercapacitors from achieving long-term stable cycling and the desired energy density. This research successfully applies the self-templated approach to prepare carbon nanotubes (CNTs) with heterogeneous architectures and numerous phase interfaces, thereby mitigating this disadvantage. Carbon nanosheets adorned with WO2 and MoO2 nanoparticles assemble the CNT with a typical three-dimensional structure. When combined with LDH in a suitable ratio, the composite electrode’s conductivity significantly improves, providing increased capacity and cycling stability. Compared to commercial CNTs, the larger size of the prepared WO2/MoO2@P, N-CNTs serves a superior supporting and connecting role, thereby preventing the NiCo-LDH from aggregating. Under the best conditions, the composite electrode demonstrates a capacity of 1237 C/g at 1 A g−1 and an optimal capacity retention of more than 92%. For the IMSC devices, the composite materials as the positive electrode achieve an energy density of 0.0590 mWh cm−2, and no capacity degradation is observed after 10,000 cycles. In addition, bending tests have demonstrated the mechanical stability of the IMSCs. Therefore, this strategy of mixing highly conductive WO2/MoO2@P, N-CNTs can effectively improve the conductivity of the composite material and the mechanical properties of the overall device. Furthermore, this concept can be further extended to the preparation and application of other wearable devices.

Mechanical, wear, thermal conductivity and hydrophobicity behavior of Kevlar fiber-epoxy structural composites reinforced with onion peel carbon quantum dot and commercial carbon nanotubes: a comparative study

Mechanical, wear, thermal conductivity and hydrophobicity behavior of Kevlar fiber-epoxy structural composites reinforced with onion peel carbon quantum dot and commercial carbon nanotubes: a comparative study

Chemically doped, purified bulk multi-walled carbon nanotube conductors with enhanced AC conductivity to 40 GHz

Metals used in radio frequency (RF) communications technologies degrade in alternating current (AC) conductivity with frequency due to the skin effect. Bulk carbon nanotube (CNT) materials have demonstrated favorable trends such as constant or increasing AC conductivity, and are emerging as potential alternative conductors. However, the resistive inter-CNT junctions present in these bulk assemblies limit overall conductivity. In this work, a waveguide-based transmission technique is used to measure the AC conductivity from 10 to 40 GHz of a commercial multi-walled CNT (MWCNT) material modified by purification to remove carbon and iron impurities, and by chemical doping with potassium tetrabromoaurate (KAuBr4). Iron impurity removal yields a frequency-independent real AC conductivity. Laser thinning and solvent plying are employed to change transmission by altering the MWCNT sheet thickness, thus enabling accurate measurement of the KAuBr4-doped MWCNT samples. Doping of the purified MWCNTs yields enhanced real AC conductivity of ∼160 kS/m, which remains constant with frequency to 40 GHz and represents a 5–6 × improvement over the as-received material at 40 GHz. KAuBr4 doping is hypothesized to enhance AC conductivity by increasing carrier density, supported by the elevated plasma frequency determined from fitting of a generalized Drude conduction model to the AC conductivity data.

Constructing the charge channel with CFx using a well-dispersed carbon nanotube arrays to boost high-rate primary battery

Pursuing ultra-high specific energy density for lithium fluorinated carbon (Li/CFx) battery requires a high fluorine to carbon ratio, resulting in low-conductivity and surface-polarization issues, which restricts battery of high-rate performance. Herein, the rich charge transport channels among CFx were constructed using a well-dispersed and highly-oriented carbon nanotube arrays (CNTA) to enhance high-rate performance in Li/CFx battery. The advantage of high-orientation lies in maintaining the appropriate van der Waals forces of this CNTA prepared by catalytic chemical vapor deposition (CCVD), which helps to avoid carbon nanotubes (CNT) entanglement and achieves good dispersion. Compared with conductive additives of commercial carbon nanotubes (CCNT) and super-P (CSP), CNTA effectively releases CFx surface-polarization favouring to Li+ diffusion. Therefore, battery performance was enhanced with reduced voltage delay and low impedance. At a discharge rate of 5 C, the Li/CFx battery using CNTA had a specific capacity of 697.32 mAh/g, while these batteries using CCNT and CSP lost discharge-performance. This highly-oriented CNTA enriches the conductive additives system of lithium primary batteries and provides a novel pathway for suppressing CFx polarization.

Synthesis of CNT/Ru/Cobalt oxide composites as oxygen evolution reaction electrocatalysts via ball milling approach

Ruthenium (Ru) and Cobalt oxides (CoO) nanoparticles are uniformly decorated on surfaces of carbon nanotubes (CNTs), via ball milling of mixtures consisting of commercial CNTs, triphenylphosphine ruthenium chlorides and Cobalt nitrates. Due to collective contributions of Ru and CoO, the obtained CNT/Ru/CoO composites exhibit excellent electrocatalytic activities and durability for oxygen evolution reaction (OER), both of which outperform those of the state-of-the-art iridium oxide catalysts.

Exploring the morphological surface resistance and optical absorption of thin black carbon nanotube films for electronic and optoelectronic devices

This study investigates the optical and electrical properties of thin black films of carbon nanotubes (CNTs) fabricated under various conditions to explore their potential integration as either a perfect broadband absorber or enhanced counter electrode. The study involves SEM measurements, surface resistance measurements, and UV–Vis. spectrometer analysis. The results show that the CNT thin films exhibit high electrical conductivity and strong light absorption across various wavelengths. Optically, we investigated the impact of varying the growth temperature and catalyst temperature on the absorption profile of the thin films. The fabricated and deposited CNTs showed broadband absorption spectra, reaching 92.8% of the commercial reference sample, covering both visible and near-infrared spectra. Alternatively, the morphological surface resistance for the CNT thin films recorded agonist commercial CNT samples and FTO-coated glass. An average surface resistance of 20.5 Ω/Sq.

Synthesis and characterization of Restricted Access Magnetic Nanotubes (M-RACNTs) for the extraction of secondary metabolites from Lasiodiplodia sp. fermentation broth

This work proposed the synthesis and the characterization of Restricted Access Magnetic Nanotubes (M-RACNTs) to be used as sorbent in the magnetic dispersive solid-phase extraction (MDSPE) of organic compounds from the fermentation broth of the endophyte Lasiodiplodia sp. Synthesis was performed by functionalizing commercial multiple-walled carbon nanotubes with magnetic nanoparticles (M-CNTs) and by coating the M-CNTs with a layer of bovine serum albumin. The materials were characterized by infrared spectroscopy with Fourier Transform, thermogravimetry, zeta potential, and scanning electron microscopy. Different crude extracts were obtained, depending on the sample pH and the elution solvent tested. Chloroform and ethyl acetate extracts showed activity against a Gram-positive pathogen (Staphylococcus aureus). The crude extract's constitution was investigated. By GC/MS analysis were found hydrocarbons, aldehydes, alcohols, among others, while by LC-MS/MS analysis were found flavonoids, macrocyclic lactones, oleic acids, jasmonic acid derivatives and amino acids. A multivariate optimization, through fractional factorial planning, for four independent variables, was performed for a hydrocarbon (hexadecane) and one possible jasmonic acid derivative, both with antimicrobial activity related in the literature. The results showed that it was possible to obtain crude extracts with high concentrations of these analytes in a single extraction procedure. The increase in the analytical signal was 3.7 times for hexadecane and 1.4 times for the possible jasmonic acid derivative. The M-RACNTs also demonstrated their ability to prevent the adsorption of macromolecules, such as lysozyme, which was confirmed through SDS-PAGE analysis.

Highly homogeneous and stable single-walled carbon nanotubes dispersion modified by polyvinylpyrrolidone and alkanolamine in water.

A novel noncovalent surface modification of commercial single-walled carbon nanotubes (SWCNTs) was successfully carried out by using ball grinding technology between SWCNTs and mixed dispersants (polyvinylpyrrolidone (PVP) and alkanolamine), affording a highly homogeneous and stable PA-SWCNTs dispersion in water. The homogeneous dispersibility and long storage stability were systematically investigated by transmittance spectroscopy, absorption spectroscopy, zeta potential analyzer, sedimentation photo and transmittance electron microscopy. Under the optimized conditions, the PA-SWCNTs dispersion modified with 0.7 wt% PVP and 0.25 wt% alkanolamine under the condition of total 6 h ball grinding time using paint shaker can be easily well-dispersed in water and has good storage stability, and no sedimentation is observed more than one month. From an industrial perspective, this method is green and easy to operate in industry.

Transformation of CO2 to Carbon Nanotubes by Catalytic Chemical Vapor Deposition using a Metal-Supported Hierarchical Zeolite Template.

The conversion of CO2 into valuable substances is a topic of great interest in current research. Carbon nanotubes (CNT) have emerged as highly promising materials for CO2 conversion. In this study, we successfully developed a catalyst by loading active transition metals (Fe or Ni) onto hierarchical zeolite for CNT synthesis. Our catalyst demonstrated excellent performance under synthetic conditions. The most favorable CNT was obtained using the 25 wt.% FeHieFAU catalyst, which exhibited a diameter size of 23.1 nm, a CNT yield of 15.4 %, and an ID /IG ratio of 0.56, indicating high quality. Additionally, we investigated the beneficial effects of the synthesized CNT by testing their current response. Notably, the current response of the synthesized CNT surpassed that of commercial CNT when using a 0.5 M H2 SO4 supporting electrolyte and cyclic voltammetry (V vs. Ag/AgCl). These findings highlight the significant contributions of the small diameter and superior quality of our synthesized pure CNT, which offer potential improvements in current response compared to commercial CNT. This research opens new avenues for utilizing CNT in CO2 conversion and electrochemical applications.

(Digital Presentation) Preparation and Characterization of PMMA-SWCNT Nanocomposites

Carbon nanotubes (CNTs) exhibit unique properties such as high tensile strength, excellent electrical conductivity, and resistance to corrosion. Unfortunately, macroscopic objects from these nanostructures do not perform equally well because the individual nanotubes do not transfer electrical charge, phonons, or stress between them sufficiently well. One possible solution to improve the properties of macroscopic ensembles from nanocarbon is to manufacture the composites with other materials like polymers, ceramics, or metals. This connection is usually beneficial. However, the properties depend strongly on the integration degree of the two compounds. For example, nanocomposites with polymers have improved mechanical (Poly(methyl methacrylate), PMMA) or electrical (in the cause of conductive polymers) properties. Many ways lead to PMMA-CNTs, but the most popular are coating (dip-coating, spin-coating, spray-coating) and dispersion methods.One of the potential applications of these composites is as a membrane for the purification of wastewater from organic residues. Unfortunately, industrial growth in the last century has caused a reduction in the availability of pure water, so the abovementioned application of CNTs would be beneficial. However, the main problem with pristine carbon nanotube films is their structural integrity. The addition of polymer molecules could overcome this problem and lead to a new effective method of removing impurities.The commercial single-walled carbon nanotubes (TuballTM) were used to create nanocomposites with PMMA using either dip-coating or dispersion method. Scanning Electron Microscopy (SEM), Raman spectroscopy, Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy, and mechanical testing were used to analyze composites. The nanocomposites were used to remove aromatic organic compounds dissolved in water. For model substances methyl orange, methylene blue, and fluorescein were chosen. UV-VIS spectroscopy was used to gauge the concentration of organic compounds before/after the filtration of the aqueous solution dissolved therein. The best results were for SWCNTs and PMMA-SWCNTs membranes as they removed more than 99% of chosen water impurities.

Synergistic Defect Engineering and Interface Stability of Activated Carbon Nanotubes Enabling Ultralong Lifespan All-Solid-State Lithium-Sulfur Batteries.

Due to the high energy density, high safety, and low cost of sulfur, all-solid-state lithium-sulfur batteries (ASSLSBs) are considered one of the most promising next-generation energy storage devices. Nevertheless, the insufficient interfacial contact between solid electrolytes (SEs) and the active material of sulfur leads to inadequate electronic and ionic conduction, which increases interfacial resistance and capacity decay. In this paper, commercial carbon nanotubes (CNTs) are activated to form porous-CNTs (P-CNTs), which are used as sulfur-bearing matrix, forming S@P-CNTs-based composite cathodes for ASSLSBs. Compared with CNTs, P-CNTs possess a larger specific surface area and more oxygen-containing groups, providing enhanced interfacial contact and stability between S@P-CNTs and Li6PS5Cl SE, which are confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. Moreover, P-CNTs can form a 3D conductive network in the composite cathodes, facilitating the migration of electrons and the diffusion of ions, as well as improving the utilization of sulfur. As a result, the S@P-CNTs-based ASSLSBs display excellent electrochemical performances, especially rarely reported ultralong lifespan, which deliver a capacity of 1099.2 mA h g-1 at a current density of 1.34 mA cm-2, and remarkably maintain 70.4% of the initial capacity over 1400 cycles.

Utilization of deep learning to classify resistance training exercises by the fabricated resistive stretch sensor

In this study, the authors proposed a method to fabricate a resistive stretch textile sensor from polyester spandex (PET/SP) fabric and commercial single-walled carbon nanotube (SWCNT). In addition, we designed and trained a one-dimension convolutional neural network to classify four resistance workouts, which employed data acquired from the proposed sensor as the input. To figure out the most appropriate PET/SP sample for the deep learning application, we investigated morphologies and characterization of three samples in distinct conditions of the coating process. Data acquired from the proposed sensor illustrated the significant difference between activated and non-activated muscle groups in each specific exercise. With the PET/SP sample which met the requirements of the application, after 100 epochs, the deep learning model achieved 97.2% training accuracy and 90% test accuracy. This study demonstrates that the SWCNT-coated PET/SP stretch textile sensor can be utilized effectively to track the activity of forearm muscles during resistance training. Other than that, the proposed 1D-CNN, with the advantage of training time and computational cost, is able to classify time series data with high performance and thus can be applied widely in various deep learning applications, especially in the healthcare and sports industries.

Integrated super-engineering polymeric electromagnetic interference shielding films withstanding the extreme environments

The electromagnetic interference (EMI) poses a threat to electronic equipment and human health, which has spawned the development of polymer-based EMI shielding materials. However, it is challenging to combine their ease of fabrication with extreme environmental resistance. Herein, a simple and consecutive bottom-up assembly route is developed to prepare EMI shielding films based on a super-engineering polymer named polyarylene ether nitrile (PEN). Thanks to the morphological transformation of PEN films, the integration of polymeric matrix and commercial carbon nanotubes is throughout the vacuum-assisted deposition and hot-press molding, resulting in a series of sandwiched nanocomposite films. In the whole X-band, the EMI SE of the nanocomposite film is up to 30 dB with a low thickness of 0.268 mm. Besides, the absorption coefficient (A) can be significantly increased to 0.93, exhibiting an excellent adsorption-dominant shielding mechanism. Due to the super-engineering polymer as a matrix, the sandwiched nanocomposite films are endowed with excellent thermal stability (Td5 = 512 °C), superior tensile strength (69 MPa) as well as improved hydrophobicity (103°). Notably, the EMI shielding and mechanical performances manifest outstanding reliability under harsh environments, including strong acid, alkali, and high-temperature treatments. The integrated preparation towards super-engineered polymer-based nanocomposites is efficient and economical, affording EMI shielding films resisting multiple harsh environments.

Introducing of leached supercapacitor coin-devices with excellent performance based on tungsten oxide-carbon nanotubes-graphite nanocomposite

In this study, leached graphite coin decorated with tungsten oxide nanoparticles and carbon nanotubes (leached tungsten oxide/carbon nanotubes-graphite coin) with high surface area and excellent mechanical strength is introduced as a novel and low-cost electrode in the supercapacitor application. The leached tungsten oxide/carbon nanotubes-graphite coin was easily fabricated via uniform addition of commercial Zinc-metal powder into the matrix of commercial graphite powder and carbon nanotubes powder, pressing under optimized pressure followed by treatment in H2SO4 solution for leaching out of Zinc from carbon nanotubes-graphite matrix and finally electrodeposition of tungsten oxide nanoparticles onto the previously leached coin. The surface chemistry and structure features of the leached coin were investigated by FTIR, RAMAN, XRD, SEM, TEM, AFM and BET analysis. The leached tungsten oxide/carbon nanotubes-graphite coin had acceptable capacitive characteristic such as negligible ohmic drop and favorite specific capacitance of 3519 mF cm−2 at 2 mA cm−2 in aqueous 1.0 M H2SO4 media. After assembling a symmetric supercapacitor coin-device including leached tungsten oxide/carbon nanotubes-graphite coin in a PVA/H2SO4 gel, the coin-device shows a high specific capacitance of 283 mF cm−2 at the current density of 2.5 mA cm−2.

Carbon nanotubes: Structural defects as stressors inducing lung cell toxicity

Lung toxicity of carbon nanotubes (CNTs) is matter of concern since very long time. However, their mechanism of toxicity is still not yet well defined. In this work, the role of structural defects as organic stressors of CNTs able to trigger their potential toxicity is investigated. Four commercial CNTs, with different carbon purity grade, are morphologically characterized by transmission electron microscopy (TEM) and the relative amount of structural defects are estimated through Raman spectroscopy, by measuring the intensity ratio D/G (ID/IG). The oxidative potential of CNTs is evaluated with cytochrome-C assay and reactive oxygen species (ROS) detection. Data show that CNTs with larger amounts of structural defects (higher ID/IG ratio) induce an increased ROS generation and consequent cytotoxicity and cellular damage, shown by TEM images of CNTs-cells interaction. Raman analyses of cells exposed to CNTs point out that the spectra of the CNTs inside the cells show no differences with respect of the signal recorded for cell-free CNTs, evidencing their biopersistence in lung cells. Raman spectra cannot provide direct indication of the existence of metals as impurity. It follows that the intensity ratio ID/IG can be taken as a predictive marker of the toxicity of a given CNT.

Facile and Scalable Synthesis of Metal- and Nitrogen-Doped Carbon Nanotubes for Efficient Electrochemical CO2 Reduction.

Metal- and nitrogen-doped carbon (M-N-C) is a promising material to catalyze electrochemical CO2 reduction reaction (CO2RR). However, most M-N-C catalysts in the literature require complicated synthesis procedures and produce small quantities per batch, limiting the commercialization potential. In this work, we developed a simple and scalable synthesis method to convert metal-impurity-containing commercial carbon nanotubes (CNTs) and nitrogen-containing organic precursors into M-N-C via one-step moderate-temperature (650 °C) pyrolysis without any other treatment nor the need to add metal precursors. Batches of catalysts in varied mass up to 10 g (150 mL in volume) per batch were synthesized, and repeatable catalytic performances were demonstrated. To the best of our knowledge, the 10 g batch is one of the largest batches of CO2RR catalysts synthesized in the literature while requiring minimal synthesis steps. The catalyst possessed single-atomic iron-nitrogen (Fe-N) sites, enabling a high performance of >95% CO product selectivity at a high current density of 400 mA/cm2 and high stability for 45 h at 100 mA/cm2 in a flow cell testing. The catalyst outperformed a benchmark noble-metal nanoparticle catalyst and achieved longer stability than many other reported M-N-C catalysts in the literature. The scalable and cost-effective synthesis developed in this work paves a pathway toward practical CO2RR applications. The direct utilization of metal impurities from raw CNTs for efficient catalyst synthesis with minimal treatment is a green and sustainable engineering approach.

Catalytic CO2 Capture via Ultrasonically Activating Dually Functionalized Carbon Nanotubes.

High energy consumption and high cost have been the obstacles for large-scale deployment of all state-of-the-art CO2 capture technologies. Finding a transformational way to improve mass transfer and reaction kinetics of the CO2 capture process is timely for reducing carbon footprints. In this work, commercial single-walled carbon nanotubes (CNTs) were activated with nitric acid and urea under ultrasonication and hydrothermal methods, respectively, to prepare N-doped CNTs with the functional group of -COOH, which possesses both basic and acid functionalities. The chemically modified CNTs with a concentration of 300 ppm universally catalyze both CO2 sorption and desorption of the CO2 capture process. The increases in the desorption rate achieved with the chemically modified CNTs can reach as high as 503% compared to that of the sorbent without the catalyst. A chemical mechanism underlying the catalytic CO2 capture is proposed based on the experimental results and further confirmed by density functional theory computations.

Urotropine-triggered multi-reactive sites in carbon nanotubes towards efficient electrochemical hydrogen peroxide synthesis

The production of hydrogen peroxide (H2O2) by electrochemical oxygen reduction is a clean and convenient route. Here, we develop a universal urotropine (hexamethylenetetramine) modified carbon-based catalyst strategy. Both experimental results and theoretical calculations proved that the introduction of urotropine not only provides the isolating O2 active sites to protect OOH* from being further split, but also excites carbon nanotube matrix to produce rich secondary O2 active sites. More importantly, the end-on type of adsorption of O2 on excited secondary reactive sites can be stabilized by the hydrogen bond effect, which greatly increases the productivity of H2O2. As a result, the urotropine (hexamethylenetetramine) modified commercial carbon nanotubes (denoted as H-CNTs) catalyst achieved 95% selectivity and 748 mmol·gcatalyst·h−1 yield of H2O2 at 0.7 V vs. RHE. Therefore, this work provides a highly potential urotropine modification strategy towards efficient electrochemical H2O2 synthesis.

Photovoltaics literature survey (no. 182)

Photovoltaics literature survey (no. 182)