Types Of Carbon Nanotubes Research Articles

Structure-Mechanical Property Relationships in Carbon Nanotube Yarns

Carbon nanotube (CNT) is an innovative material with significant potential for a wide range of applications, including but not limited to the development of lightweight composite materials or superconductors. A single CNT demonstrates an exceptional degree of tensile strength. CNTs are commonly employed in a structure of yarn, wherein several CNT strands are arranged and aligned together. CNT yarns, on the other hand, have a lower tensile strength than individual CNTs due to the different parameters of the yarn. This study aimed to investigate the effect of different structural parameters on the mechanical properties of CNT yarn. Sixty CNT yarn models with different structures were simulated with the molecular dynamic (MD) simulation. The varied parameters are the chirality of the CNTs, CNTs’ inner diameter, number of walls, crosslink density, and yarn twist angle. Tensile strength results from the simulations were compared concerning the varied parameters, and their influence on the nominal tensile strength of the CNT yarn was studied. It was found that the parameters for the CNT yarn that yields a higher tensile strength are the armchair type CNT with a small diameter, a large number of walls, crosslink density higher than approximately 1%, and a low twist angle.

Volatile-char interactions during biomass pyrolysis: Effects of functionalized graphitized carbon nanotubes on volatile distribution of cellulose and its model compounds

Volatile-char interactions are prevalent in biomass pyrolysis processes. To gain deeper insights into their impact on biomass pyrolysis volatile distribution, interactions between volatile compounds and char during flash pyrolysis of glucose, cellobiose, and cellulose were investigated using a pyrolysis–gas chromatography/mass spectrometry detection technique, by modifying both the chain lengths of the raw materials and the functional groups of graphitized multi-walled carbon nanotubes (CNTs). The results reveal that volatile-char interactions markedly influence the distribution of the final pyrolysis products derived from glucose-based compounds. In the presence of any type of CNTs, dehydrated saccharides in the primary products, particularly levoglucosan (LG), exhibit the highest sensitivity to the interactions. Consequently, primary products such as LG and 5-hydroxymethylfurfural (HMF) undergo secondary pyrolysis, yielding compounds such as levoglucosenone (LGO) and 5-methyl-2-furancarboxaldehyde (FCM). Additionally, CNTs without functional groups are advantageous for the production of expensive LGO (The relative abundance reached 9.65%), whereas the relative abundance of FCM increases significantly with hydroxyl-, carboxyl-, and amino-modified carbon nanotubes. Particularly, the relative abundance of FCM is highest in the presence of amino-modified carbon nanotubes, regardless of whether the feedstock is glucose, cellobiose, or cellulose, with values of 25.14%, 23.32%, and 4.23%, respectively. Furthermore, consistent changes in product distribution trends among different glucose-based compounds under identical CNT conditions suggest that glycosidic bonds have minimal impact on volatile-char interactions.

Interfacial bonding characteristics of multi-walled carbon nanotube/ultralight foamed concrete

Abstract In the development of carbon nanotube (CNT)-reinforced cement-based matrices, one of the fundamental issues that investigators are confronting is CNT/cement-based matrix interfacial bonding, which determines the load transfer capability from the matrix to the CNT. In the present work, the stress transfer properties of multi-walled carbon nanotubes (MWCNTs) and ultralight foamed concrete matrices were studied using microscopic Raman spectrometry analysis. Two types of CNTs, such as MWCNT and MWCNT-COOH, were considered, wherein MWCNT-COOH was covered with fundamental COOH groups. The results show that the compressive and flexural strengths were 75 and 236% better for ultralight foamed concrete with a dry density of 200 kg/m3 with 0.4 wt% MWCNT-COOH addition, respectively. This indicates that the fundamental COOH groups of the MWCNT play an important role in determining the interfacial bonding characteristics between the MWCNT and the ultralight foamed concrete matrix. Therefore, the attachment of COOH groups with a reasonable concentration to the MWCNT surface may be an effective way to significantly improve the load transfer between the MWCNT and the ultralight foamed concrete matrix, leading to increased compressive and flexural strength values of composites.

The impact of chemical functionalization of carbon nanotubes on the electrochemical performance of carbon fiber/pyrocarbon/carbon nanotube composites as potential materials for electrodes for nerve cell stimulation

In this work, we propose a new carbon–carbon (C–C) composites as a potential materials for electrodes for neural stimulation in neurodegenerative disorders. The C–C composites were made via chemical vapour deposition (CVD) synthesis of pyrocarbon on carbon fibers, with subsequent thermal spray deposition of carbon nanotubes (CNT). Different CNT types were tested to evaluate their impact on electrochemical and biological performance. Materials were analyzed for microstructure, surface chemistry, and electrochemical properties, then tested using SH-SY5Y neuroblastoma cells for biological assessment. TheC–C composites coated with a hydroxy-terminated CNT demonstrated significantly enhanced electrochemical properties, inparticular increased cathodal charge capacity upto12.51mCcm−2, a wide safe potential window of −1.53 to 1.26 V, and decreased impedance, and cut-off frequency (fcut-off = 0.16 kHz). No acute negative biological responses of the materials were detected after 48 h of exposition. Such properties significantly outperform the properties of platinum, which is the basic element of platinum electrodes, demonstrating the excellent performance of the obtained composites and showing it may constitute the basic element of carbon electrodes for nerve stimulation in the future. Our work presents the method for obtaining biologically inert carbon composite micro-electrodes which can potentially be adapted to neural stimulation.

Antibacterial Interactions of Ethanol-Dispersed Multiwalled Carbon Nanotubes with Staphylococcus aureus and Pseudomonas aeruginosa.

Infectious diseases are acknowledged as one of the leading causes of death worldwide. Statistics show that the annual death toll caused by bacterial infections has reached 14 million, most of which are caused by drug-resistant strains. Bacterial antibiotic resistance is currently regarded as a compelling problem with dire consequences, which motivates the urgent identification of alternative ways of fighting bacteria. Various types of nanomaterials have been reported to date as efficient antibacterial solutions. Among these, carbon-based nanomaterials, such as carbon nanodots, carbon graphene oxide, and carbon nanotubes (CNTs), have been shown to be effective in killing a wide panel of pathogenic bacteria. With this study, we aim to provide additional insights into this topic of research by investigating the antibacterial activity of a specific type of multiwalled CNTs, with diameters from 50 to 150 nm, against two representative opportunistic pathogens, i.e., the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Pseudomonas aeruginosa, both included among the top antibiotic-resistant pathogens. We also test the synergistic effect of CNTs with different antibiotics commonly used in the treatment of infections caused by S. aureus and/or P. aeruginosa. Additionally, a novel approach for quantitatively analyzing bacterial aggregation in brightfield microscopy images was implemented. This method was utilized to assess the effectiveness of CNTs, either alone or in combination with antibiotics, in dispersing bacterial aggregates. Finally, atomic force microscopy coupled with a newly devised image analysis pipeline was used to examine any potential morphological changes in bacterial cells following exposure to CNTs and antibiotics.

Batch Fabrication of Flexible Strain Sensors with High Linearity and Low Hysteresis for Health Monitoring and Motion Detection.

In recent years, flexible strain sensors have gradually come into our lives due to their superiority in the field of biomonitoring. However, these sensors still suffer from poor durability, high hysteresis, and difficulty in calibration, resulting in great hindrance of practical application. Herein, starting with interfacial interaction regulation and structure-induced cracking, flexible strain sensors with high performance are successfully fabricated. In this strategy, dopamine treatment is used to enhance the bonding between flexible substrates and carbon nanotubes (CNT). The combination within the conductive networks is then controlled by substituting the CNT type. Braid-like fibers are employed to achieve controllable expansion of the conductive layer cracks. Finally, we obtain strain sensors that possess high linearity (R2 = 0.997) with low hysteresis (5%), high sensitivity (GF = 60) and wide sensing range (0-50%), short response time (62 ms), outstanding stability, and repeatability (>10,000 cycles). Flexible strain sensors with all performances good are rarely reported. Static and dynamic respiration and pulse signal monitoring by the fiber sensor are demonstrated. Moreover, a knee joint monitoring system is constructed for the monitoring of various walking stances, which is of great value to the diagnosis and rehabilitation of many diseases.

Why Carbon Nanotubes Improve Aqueous Nanofluid Thermal Conductivity: A Qualitative Model Critical Review

Media thermal conductivity is important in various heat-transfer processes. Many conventional fluid conductors suffered low conductivity and environmental issues. Therefore, research was active in finding out alternative systems, mostly relying on aqueous liquids that are low-cost and ecofriendly. After the emergence of carbon nanotubes (CNTs), with their many special structural, electrical and thermal properties, they have been examined for many applications, including heat-transfer processes. Adding CNTs to water yields CNT aqueous nanofluids that have been widely investigated as heat-transfer media. The literature shows that CNT addition improves water thermal conductivity and other water properties, such as viscosity, surface tension, freezing point and boiling point. The literature also shows that nanofluid thermal conductivity improvement is affected by CNT type and concentration, in addition to other factors such as surfactant addition. All these subjects were widely described in literature, focusing on experimental, modelling and theoretical accounts. Despite the wide literature, there exist inconsistencies and discrepancies between reports that need to be justified. In addition to technical papers, many reviews were published on various aspects of the subject including experimental results and mathematical modeling. However, the very basic question here is as follows: Why does adding CNT to water affect its thermal conductivity? In spite of the wide published literature, this issue was not targeted in a simple qualitative approach. This review provides a clear understanding of how CNTs improve thermal conductivity of aqueous nanofluids. A qualitative model is presented to explain mechanisms behind improvement as presented in the literature. CNT type effects are discussed with other factors such as aspect ratio, Reynold number, dispersion quality, composition, temperature and additives. CNT functionalization is described. Relations to estimate nanofluid thermal conductivity are discussed. The model will help specialists to tailor CNT aqueous nanofluid characteristics as desired by varying types and concentrations of CNT and surfactant, and other factors.

Improving the water-repellent properties of carbon nanotube-polycarbonate composites by introducing nanoscale patterns into the injection molding process

In this study, we explore the impact of hydrophobic nanomaterials, specifically carbon nanotubes (CNTs), on the water repellency of composite materials. These composites are prepared by combining multilayered or single-layered CNTs with polycarbonate (PC). Our goal was to develop highly water-repellent materials by directly forming nanopatterns on the surface through injection molding to enhance water repellency. Irrespective of the CNT type, widening the spacing between surface patterns and increasing the CNT concentration from 0 to 30 wt% resulted in a notable increase in the water contact angle to 161°, surpassing that of Teflon (108°). Moreover, in the multilayered CNT/PC system, a reduction in the sliding angle was observed compared to that of pure polycarbonate, demonstrating a lotus effect-like trend. Conversely, in the case of single-layered CNTs, despite an increase in the contact angle, the sliding angle did not decrease as significantly as in the multilayered CNTs. This implies that the superior transferability during the injection molding process of multilayered CNT/PC compared to single-layered CNT/PC is the underlying factor. This technology holds promise not only in the realm of mobility, such as in the aviation and automotive industries, but also in the medical field, with applications in microfluidic devices.

Carbon nanotubes induce cytotoxicity and apoptosis through increasing protein levels of Bax and ROS in mouse skin fibroblasts.

Carbon nanotubes (CNTs) are a significant discovery in nanotechnology, with widespread applications in modern technology. However, there are concerns about their potential toxicity, particularly in skin cells. This study aimed to investigate the mechanisms by which CNTs induced cytotoxicity and apoptosis in mouse skin fibroblasts. The mice skin fibroblasts were isolated and exposed to two types of CNTs at various concentrations and then analyzed for changes in viability, reactive oxygen species (ROS) production, the levels of Bcl-2-associated X protein (Bax), and lactate production. The results demonstrated that CNTs reduced cell viability and increased ROS production in a dose-dependent manner. Additionally, the current study found that CNTs increased the protein levels of Bax, a pro-apoptotic protein, in mouse skin fibroblasts. Furthermore, it was observed a significant decrease in lactate production in cells exposed to CNTs. The findings concluded that CNTs have the potential to be toxic substances for skin fibroblasts, which serve as the body's first line of defense. This is evidenced by their ability to increase the production of ROS and the protein levels of Bax, as well as reduce lactic acid levels. As lactic acid has been reported to have beneficial effects on skin collagen production, further studies are needed to fully understand the impact of carbon nanotube exposure on human skin health.

Analysis of carbon nanotube levels in organic matter: an inter-laboratory comparison to determine best practice

Carbon nanotubes (CNTs) are increasingly being used in industrial applications, but their toxicological data in animals and humans are still sparse. To assess the toxicological dose-response of CNTs and to evaluate their pulmonary biopersistence, their quantification in tissues, especially lungs, is crucial. There are currently no reference methods or reference materials for low levels of CNTs in organic matter. Among existing analytical methods, few have been fully and properly validated. To remedy this, we undertook an inter-laboratory comparison on samples of freeze-dried pig lung, ground and doped with CNTs. Eight laboratories were enrolled to analyze 3 types of CNTs at 2 concentration levels each in this organic matrix. Associated with the different analysis techniques used (specific to each laboratory), sample preparation may or may not have involved prior digestion of the matrix, depending on the analysis technique and the material being analyzed. Overall, even challenging, laboratories’ ability to quantify CNT levels in organic matter is demonstrated. However, CNT quantification is often overestimated. Trueness analysis identified effective methods, but systematic errors persisted for some. Choosing the assigned value proved complex. Indirect analysis methods, despite added steps, outperform direct methods. The study emphasizes the need for reference materials, enhanced precision, and organized comparisons.

A Systematic Investigation on the Effect of Carbon Nanotubes and Carbon Black on the Mechanical and Flame Retardancy Properties of Polyolefin Blends.

Due to high filler loading, clean, commercial, thermoplastic, flame-retardant materials are mechanically unstable when insulating wires and cables. In this study, composite formulations of linear low-density polyethylene (LLDPE)/ethylene-vinyl acetate (EVA) containing a flame retardant, such as magnesium hydroxide (MH; formula: Mg(OH)2) and huntite hydromagnesite (HH; formula: Mg3Ca(CO3)4, Mg5(CO3)4(OH)2·3H2O), were prepared. The influence of carbon nanotubes (CNTs) and carbon black (CB) on the mechanical properties and flame retardancy of LLDPE/EVA was studied. Three types of CNTs were examined for their compatibility with other materials in clean thermoplastic flame-retardant compositions. The CNTs had the following diameters: 10-15 nm, 40-60 nm, and 60-80 nm. Optimum mechanical flame retardancy and electrical properties were achieved by adding CNTs with an outer diameter of 40-60 nm and a length of fewer than 20 nm. Large-sized CNTs result in poor mechanical characteristics, while smaller-sized CNTs improve the mechanical properties of the composites. CB enhances flame retardancy but deteriorates mechanical properties, particularly elongation at break, in clean, black, thermoplastic, flame-retardant compositions. Obtaining satisfactory compositions that meet both properties, especially formulations passing the V-0 of the UL 94 test with a minimum tensile strength of 9.5 MPa and an elongation at break of 125%, is challenging. When LLDPE was partially substituted with EVA, the limiting oxygen index (LOI) increased. The amount of filler in the formulations determined how it affected flammability. This study also included a reliable method for producing clean, black, thermoplastic, flame-retardant insulating material for wire and cable without sacrificing mechanical properties.

Effects of Topological Parameters on Thermal Properties of Carbon Nanotubes via Molecular Dynamics Simulation

Due to their unique properties, carbon nanotubes (CNTs) are finding a growing number of applications across multiple industrial sectors. These properties of CNTs are subject to influence by numerous factors, including the specific chiral structure, length, type of CNTs used, diameter, and temperature. In this topic, the effects of chirality, diameter, and length of single-walled carbon nanotubes (SWNTs) on the thermal properties were studied using the reverse non-equilibrium molecular dynamics (RNEMD) method and the Tersoff interatomic potential of carbon–carbon based on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). For the shorter SWNTs, the effect of chirality on the thermal conductivity is more obvious than for longer SWNTs. Thermal conductivity increases with increasing chiral angle, and armchair SWNTs have higher thermal conductivity than that of zigzag SWNTs. As the tube length becomes longer, the thermal conductivity increases while the effect of chirality on the thermal conductivity decreases. Furthermore, for SWNTs with longer lengths, the thermal conductivity of zigzag SWNTs is higher than that of the armchair SWNTs. Thermal resistance at the nanotube–nanotube interfaces, particularly the effect of CNT overlap length on thermal resistance, was studied. The simulation results were compared with and in agreement with the experimental and simulation results from the literature. The presented approach could be applied to investigate the properties of other advanced materials.

Scalable fabrication of lightweight carbon nanotube aerogel composites for full X-band electromagnetic wave absorption

Electromagnetic waves (EMWs) from advanced electronic devices can hinder normal operation of other electronic equipment, negatively affecting their performance and cause harmful impacts on human health by breaking down DNA strands and causing cancer. In this study, we thrivingly prepared new lightweight EMW absorbing aerogel composites by first blending polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), carbon nanotube (CNT), reduced graphene oxide (rGO), and carbonyl iron (CI), followed by freeze-drying. The materials are promising for up-scale production with the current pilot-scale samples sizing 35 cm × 35 cm. The effects of CNT types, CNT, rGO, CI, and crosslinker contents on EMW absorption ability are comprehensively investigated. The obtained aerogel composites exhibit a 3D porous structure with low densities (0.088–0.210 g/cm3), high thermal stability (227 °C), and high Young's modulus (670.9 kPa) compared to past aerogels. Notably, the materials with 3.0–3.5 mm in thickness achieve the minimum reflection loss (RLmin) of up to −42 dB (99.99 % EMW energy lost) and provide coverage across the entire X-band (8.2–12.4 GHz) with RL < −10 dB, indicating a 90 % attenuation of EMW energy. Compared to commercial Ni/CNT and other existing composites, our materials boast a broader effective bandwidth of 1.2–2.2 GHz. These properties make our aerogel composites highly promising for valuable commercial use, offering lightweight, durable, and efficient EMW absorption capabilities.

Controlled synthesis, properties, and applications of ultralong carbon nanotubes.

Carbon nanotubes (CNTs) are typical one-dimensional nanomaterials which have been widely studied for more than three decades since 1991 because of their excellent mechanical, electrical, thermal, and optical properties. Among various types of CNTs, the ultralong CNTs which have lengths over centimeters and defect-free structures exhibit superior advantages for fabricating superstrong CNT fibers, CNT-based chips, transparent conductive films, and high-performance cables. The length, orientation, alignment, defects, cleanliness, and other microscopic characteristics of CNTs have significant impacts on their fundamental physical properties. Therefore, the controlled synthesis and mass production of high-quality ultralong CNTs is the key to fully exploiting their extraordinary properties. Despite significant progress made in the study of ultralong CNTs during the past three decades, the precise structural control and mass production of ultralong CNTs remain a great challenge. In this review, we systematically summarize the growth mechanism and controlled synthesis strategies of ultralong CNTs. We also introduce the progress in the applications of ultralong CNTs. Additionally, we summarize the scientific and technological challenges facing the mass production of ultralong CNTs and provide an outlook and in-depth discussion on the future development direction.

Apoptosis as a mechanism of human respiratory cell death upon exposure to carbon nanotubes

Introduction. Carbon nanotubes (CNTs) are a group of promising nanomaterials for industrial and biomedical applications. There has been shown influence of the physicochemical characteristics of CNTs on the toxic effects, including the ability to cause DNA damage and induce apoptosis. In this study, there was carried out a comparative assessment of pro-apoptotic effects under exposure to single-walled and multi-walled CNTs produced in Russia on human respiratory cells.&#x0D; Materials and methods. Human bronchial epithelial cells BEAS-2B, alveolar epithelial cells A549, and lung fibroblasts MRC5-SV40 were exposed to pristine and purified TUBALLTM SWCNTs and Taunit-M MWCNTs. In cells exposed to 4 concentrations (100, 50, 0.03, 0.0006 μg/ml) of all types of CNTs for 72 hours, the level of mRNA of the P53, BAX and BCL2 genes, as well as the level of reactive oxygen species were assessed.&#x0D; Results. All types of CNTs initiated apoptosis in human respiratory epithelial cells BEAS-2B and A549, but not in MRC5-SV40 lung fibroblasts. BEAS-2B were more sensitive to the effects of MWCNTs, while A549 were more sensitive to pristine SWCNTs. Apoptosis was initiated at low concentrations, including those corresponding to industrial exposures. The mechanism of oxidative stress could act as a factor in triggering apoptosis in lung epithelial cells.&#x0D; Limitations. Relatively short (72 hours) cell incubation time and the use of 2D cell models that do not consider real cell interactions.&#x0D; Conclusion. There were revealed differences in the mechanisms of initiation of the internal pathway of apoptosis and sensitivity to different types of CNTs depending on the type of epithelial cells. Comparative analysis of the initiation of apoptosis by different types of CNTs has shown that there are differences in potential target cells and toxic mechanisms, which should be considered in further studies.

Mechanisms related to carbon nanotubes genotoxicity in human cell lines of respiratory origin

Potential genotoxicity and carcinogenicity of carbon nanotubes (CNT), as well as the underlying mechanisms, remains a pressing topic. The study aimed to evaluate and compare the genotoxic effect and mechanisms of DNA damage under exposure to different types of CNT.Immortalized human cell lines of respiratory origin BEAS-2B, A549, MRC5-SV40 were exposed to three types of CNT: MWCNT Taunit-M, pristine and purified SWCNT TUBALL™ at concentrations in the range of 0.0006–200 μg/ml. Data on the CNT content in the workplace air were used to calculate the lower concentration limit. The genotoxic potential of CNTs was investigated at non-cytotoxic concentrations using a DNA comet assay. We explored reactive oxygen species (ROS) formation, direct genetic material damage, and expression of a profibrotic factor TGFB1 as mechanisms related to genotoxicity upon CNT exposure.An increase in the number of unstable DNA regions was observed at a subtoxic concentration of CNT (20 μg/ml), with no genotoxic effects at concentrations corresponding to industrial exposures being found.While the three test articles of CNTs exhibited comparable genotoxic potential, their mechanisms appeared to differ. MWCNTs were found to penetrate the nucleus of respiratory cells, potentially interacting directly with genetic material, as well as to enhance ROS production and TGFB1 gene expression. For A549 and MRC5-SV40, genotoxicity depended mainly on MWCNT concentration, while for BEAS-2B – on ROS production. Mechanisms of SWCNT genotoxicity were not so obvious. Oxidative stress and increased expression of profibrotic factors could not fully explain DNA damage under SWCNT exposure, and other mechanisms might be involved.

Pleural inflammatory response, mesothelin content and DNA damage in mice at one-year after intra-pleural carbon nanotube administration

Many in vitro and in vivo studies have shown that exposure to carbon nanotubes (CNTs) is associated with inflammation, oxidative stress and genotoxicity, although there is a paucity of studies on these effects in the pleural cavity. In the present study, we investigated adverse outcomes of pleural exposure to multi-walled CNTs (MWCNT-7, NM-401 and NM-403) and single-walled CNTs (NM-411). Female C57BL/6 mice were exposed to 0.2 or 5 µg of CNTs by intra-pleural injection and sacrificed one-year post-exposure. Exposure to long and straight types of MWCNTs (i.e. MWCNT-7 and NM-401) was associated with decreased number of macrophages and increased number of neutrophils and eosinophils in pleural lavage fluid. Increased protein content in the pleural lavage fluid was also observed in mice exposed to MWCNT-7 and NM-401. The concentration of mesothelin was increased in mice exposed to MWCNT-7 and NM-411. Levels of DNA strand breaks and DNA oxidation damage, measured by the comet assay, were unaltered in cells from pleural scrape. Extra-pleural effects were seen in CNT exposed mice, including enlarged and pigmented mediastinal lymph nodes (all four types of CNTs), pericardial plaques (MWCNT-7 and NM-401), macroscopic abnormalities on the liver (MWCNT-7) and ovaries/uterus (NM-411). In conclusion, the results demonstrate that intra-pleural exposure to long and straight MWCNTs is associated with adverse outcomes. Certain observations such as increased content of mesothelin in pleural lavage fluid and ovarian/uterine abnormalities in mice exposed to NM-411 suggests that exposure to SWCNTs may also be associated with some adverse outcomes.

Quantitative analysis of the correlation between sp3 bonds and functional groups in covalently functionalized single-walled carbon nanotubes

The potential of carbon nanotube (CNT)-based applications in diverse scientific fields has been demonstrated by achieving precise control of their surfaces through chemical functionalization. However, the formation of fatal defects like sidewall cleavage is an increasingly important concern as it significantly degrades the performance of CNTs. The presence of these structural disruptions has been ascertained by transmission electron microscopy, but a comprehensive understanding of their surface remains unclear due to its highly localized observation. Here, we demonstrate a framework for quantitative evaluation of the relationship between sp3 bonds and functional groups on CNT surface by combining μ-Raman and energy dispersive X-ray spectroscopy in scanning electron microscope imaging techniques. Nonuniform features of the degree of functionalization in strongly oxidized two types of single-walled CNTs are appropriately visualized in both measurements, allowing a systematic assessment of the surface states. Quantitative analysis reveals that the nm-scale sidewall openness during the chemical process is adequately explained by introducing a variable θ defined as the ratio of the degree of functionalization/defect density. These findings can be widely utilized as a novel evaluation technique to control the reactivity in the surface functionalization of various carbon nanomaterials.

Effect of carbon nanotube type and length on the electrical conductivity of carbon nanotube polymer nanocomposites

Carbon nanotube (CNT) type and length are two key factors that affect the electrical behavior of CNT/polymer nanocomposites. However, numerical studies that consider these two factors simultaneously are limited. This paper presented a stochastic multiscale numerical model to predict the electrical conductivity and percolation threshold of polymer nanocomposites containing single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The combined effects of CNT type and length on the electrical conductivity and percolation threshold of the polymer nanocomposites were investigated. The model predictions were validated against experimental data of commercially available CNTs. Our results showed that the effect of CNT type varied based on both the length and aspect ratio of the CNTs. Long SWCNTs exhibited the greatest enhancement of the polymer’s electrical conductivity with the lowest percolation threshold among all the CNT types studied.

Carbon nanotubes as fast-thickening agents in polyalphaolefin greases: Partial crystallinity and intertube joints toward multifunctionality

Scalable and economic manufacturing of carbon nanotube (CNT) greases addresses the current challenges of nanofluids. The key problems remain the complex and non-obvious nature of nanotube-base fluid interactions with the diversity of nanotube morphological variants as the main aspect. Here, we prove that successful formation of stable and multifunctional CNT-polyalphaolefin (PAO) greases is possible only by employing two types of multi-wall CNTs (MWCNTs) as the thickening as well as thermo- and electro-active agents, i.e., (1) thin, entangled, less crystalline nanotubes and (2) thick nanotubes connected via few-mismatched-layer graphenoid joints. Using mechanical spectroscopy, SEM, TEM, Raman spectroscopy, inverse gas chromatography (IGC), and Hansen solubility parameters, we analyze the mechanisms governing fast-thickening behavior and CNT-PAO affinities, revealing a reversible formation of a 3D CNT-network which mimics a mesh of the conventional lithium soaps. Finally, we reveal the multifunctionality of the CNT-PAO greases, expressed in as high as 58%- and 700%-enhancements of thermal and alternating current conductivity, respectively, compared to PAO base fluid.