Groups Of Carbon Nanotubes Research Articles

Determination of aristolochic acid using a piezoelectric immunosensor based on magnetic carbon nanocomposites

A technique for the determination of aristolochic acid (AA) in food products using a piezoelectric immunosensor is presented. Magnetic carbon nanocomposites (MCNC) were used as the recognition layer of the sensor, on the surface of which protein conjugates of AA were immobilized. Abstract-Methods for the synthesis of Fe3O4 magnetic nuclei and their attachment to the surface of multi-walled carbon nanotubes (CNTs) have been studied. Using IR spectrometry, it was found that the formation of the recognition layer of the sensor occurs due to the formation of covalent bonds between the amino groups of AA conjugates and carboxyl groups of CNTs. The concentrations of protein conjugates based on ovalbumin (OVA) and bovine serum albumin (BSA) (0.3 and 0.2 mg/ml) and the degree of antibody dilution (0.25) were determined, which provide optimal characteristics of the piezoelectric immunosensor. The metrological characteristics of the method for determining AA have been established. The range of determined concentrations of AA and the limit of detection when using a piezoelectric immunosensor with a recognition layer based on MUNA/AA-OVA and MUNA/AA-BSA are (ng/ml): 50 – 400 and 10; 100 – 300 and 50, respectively. The sensor has been tested in the determination of AA in samples of Chinese herbal tea and dietary supplements for weight loss. No acid was found in tea, and in dietary supplements, the acid content is 3.2 μg/g.

Fabrication of high-performance moisture-electric generators via synergistic effect between CNTs and TiO2 on porous PU structure

A “root-like” dendritic colloid was used to attach carbon nanotubes (CNTs) and titanium dioxide (TiO2) onto polyurethane (PU) foam to prepare high-performance moisture-electric generators (MEGs). The hybrid filler coated polyvinylidene difluoride (PVDF) dendritic colloids illustrates a “filler-wrapped” structure, which enables the filler to be in direct contact with water and enhances the interaction with water. Grabbing the hybrid filler with PVDF dendritic colloids can significantly increase the content of hybrid filler in PU foam based MEG. To address the problems of few active functional groups of CNTs and high internal resistance of TiO2, a synergistic network is constructed by hybridization. Due to the synergistic effect between hydrophilic TiO2 and CNTs, excellent performance of the MEG is illustrated, including high open-circuit voltage (0.51 V), short-circuit current (47.3 μA). The power density and energy density can reach 32.21 μW∙cm−3 and 15.97 μWh∙cm−3, respectively. This work provides a new strategy for the moisture-electric generators.

Rheological behaviors and viscosity prediction model of cementitious composites with various carbon nanotubes

This study aims to understand the effects and mechanisms of length, diameter, and functional group of carbon nanotubes (CNTs) on rheological behaviors of cementitious composites. The experimental results show that the addition of CNTs decreases the flow index and increases the critical shear rate of cementitious composites. CNTs with a sub-micrometer length and small diameter endow cementitious composites with high yield stresses and minimum viscosities. Influenced by the high water absorption of hydroxylic groups, the minimum viscosity of cementitious composites with hydroxyl functionalized CNTs is larger than that of composites with pristine carbon nanotubes (p-CNTs). By contrast, the yield stress and minimum viscosity of cementitious composites with carboxyl functionalized CNTs are smaller than that of cementitious composites with p-CNTs at most contents due to the high dispersion induced by carboxyl groups. The effect mechanisms of CNTs on rheological behaviors can be attributed to adsorption effect and entanglement effect, which are closely related to length, diameter and functionalization groups of CNTs. The established minimum viscosity prediction model considering the influence of CNT physicochemical features can provide guidance for regulating the workability and hardened performance of CNTs modified cementitious composites.

Molecular dynamics simulations of defective carbon nanotubes on the aging and friction properties of nitrile butadiene rubber composites

AbstractThe thermal‐oxidative aging (TOA) and tribological properties of rubber had attracted attention in the petrochemical field. In this study, the mechanical and tribological properties of defect‐free, Stone–Wales (SW), and single adatom (SA) defective carbon nanotubes (CNTs)/nitrile butadiene rubber (NBR) composites were investigated using molecular dynamics simulations. Poly (1,2‐dihydro‐2,2,4‐trimethyl‐quinoline) (antioxidant RD) was added to the composites to analyze their TOA mechanisms. Antioxidant RD provided the best protective effect in SW‐CNTs/RD/NBR composites, and their TOA properties were enhanced. In addition, the Young's modulus, bulk modulus, and shear modulus, friction coefficient, and wear rate of the SW‐CNTs/RD/NBR composites were improved. The effects of SW‐CNTs on the RD/NBR composites were elucidated from a molecular perspective. The surface structures of three groups of CNTs were analyzed, and the SW‐CNTs exhibited a stronger adsorption ability and binding effect. It was determined that the antioxidant RD and NBR could be more stably dispersed between the molecular chains in the SW‐CNTs/RD/NBR composites.

Flexible actuator by electric bending of saline solution-filled carbon nanotubes

As a two-phase hybrid material, liquid-filled carbon nanotubes (CNTs) provide a great opportunity to design dexterous flexible nano-manipulator actuated by electric field. Here, we report a group of saline solution-filled CNTs with the end constraint can realize 360° all-round bending in a suitable electric field. The molecular dynamics (MD) simulation results show that saline solution-filled CNTs can be bent under the axial-lateral compound electric field, whereas the bending deflection increases with the increase of salinity, CNTs length and electric intensity. The deformation mechanism of saline solution-filled CNTs under the electric field is clarified by exploring the movement and distribution of salt ions in CNTs under the axial electric field. Moreover, based on the bending deformation characteristics of saline solution-filled CNTs, the MD simulations for the two-finger and four-finger nano grippers grasping diamond balls are carried out to demonstrate the micromanipulation functions of saline solution-filled CNTs. The findings will provide an important theoretical basis for the design and application of micromanipulation devices based on low dimensional carbon materials.

Influence of crystallinity and chain interactions on the electrical properties of polyamides/carbon nanotubes nanocomposites

AbstractThis work evaluates the effects of the crystallinity degree and π–π interactions between nanoparticles and a polymeric matrix on the electrical properties of polyamides and carbon nanotubes (CNT) nanocomposites. Two polymeric matrices were chosen; polyamide (PA) 6.6, a semi‐crystalline polymer, and PA 6I‐6T (here called aPA), a semi‐aromatic and amorphous polyamide. The PA 6.6 crystallinity degree did not significantly change. Both lamellar thicknesses, amorphous (La) and crystalline (Lc), were estimated through Small‐angle X‐ray scattering. La increased significantly when CNTs were added. Both nanocomposites presented almost the same percolation threshold. In aPA nanocomposites, the π–π interaction between aromatic groups of CNTs and aPA is not only responsible for a homogeneous CNT dispersion, but also creates a direct path, parallel to the electrodes, for electron conduction after the percolation limit. In the PA 6.6 nanocomposites, the CNTs preferably disperse in the amorphous regions, forming a conductive network.

Assessment of the Carcinogenicity of Carbon Nanotubes in the Respiratory System.

Simple SummaryMalignant mesothelioma is an aggressive cancer of the membranes covering the lung and chest cavity (pleura) or the abdomen (peritoneum), mainly linked to asbestos exposure. Asbestos is a proven human carcinogen but its use is far from being universally banned and the forecasts on the incidence of mesothelioma over the next several years are far from optimistic. Carbon nanotubes are a promising type of nano-materials used in the field of nanotechnology for a wide range of applications. However, the similarities between asbestos and CNTs have raised many concerns about their danger and are still the subject of intense research. Keeping in mind that the asbestos tragedy could have been prevented, the aim of this study is to review the recent scientific evidence on CNTs carcinogenicity.In 2014, the International Agency for Research on Cancer (IARC) classified the first type of carbon nanotubes (CNTs) as possibly carcinogenic to humans, while in the case of other CNTs, it was not possible to ascertain their toxicity due to lack of evidence. Moreover, the physicochemical heterogeneity of this group of substances hamper any generalization on their toxicity. Here, we review the recent relevant toxicity studies produced after the IARC meeting in 2014 on an homogeneous group of CNTs, highlighting the molecular alterations that are relevant for the onset of mesothelioma. Methods: The literature was searched on PubMed and Web of Science for the period 2015–2020, using different combinations keywords. Only data on normal cells of the respiratory system after exposure to fully characterized CNTs for their physico-chemical characteristics were included. Recent studies indicate that CNTs induce a sustained inflammatory response, oxidative stress, fibrosis and histological alterations. The development of mesothelial hyperplasia, mesothelioma, and lungs tumors have been also described in vivo. The data support a strong inflammatory potential of CNTs, similar to that of asbestos, and provide evidence that CNTs exposure led to molecular alterations known to have a key role in mesothelioma onset. These evidences call for an urgent improvement of studies on exposed human populations and adequate systems for monitoring the health of workers exposed to this putative carcinogen.

Insights into the effect of polymer functionalization of multiwalled carbon nanotubes in the design of flexible strain sensor

In the background of designing a polymer nanocomposite based flexible strain sensors, homogenized dispersion of nanofillers remain challenging due to the trade-off between upholding of inherent characteristics of nanofillers and stable dispersion of nanofillers in the polymer matrix. This study provides an approach of balancing the stable dispersion of nanofillers and maintain the inherent characteristics of nanofibers by the method of polymer functionalization. Herein, two oppositely charged polymers polystyrene sulfonate sodium salt (PSS) and poly-diallyl-dimethyl-ammonium chloride (PDDA) are used separately to functionalize the multiwalled carbon nanotubes (CNT) and it dispersed in poly (vinylidene difluoride) (PVDF) polymer matrix to get flexible nanocomposite strain sensor to investigate both electrical conductivity and the gauge factor. PSS functionalized CNT (PSS-CNT) shows better dispersion than the PDDA-CNT in PVDF matrix. Besides, the electrical conductivity of PVDF/PSS-CNT (0.44 ± 0.02 Scm−1) is about 28 times higher than the PVDF/PDDA-CNT, and the gauge factor of PVDF/PSS-CNT (9.8 ± 0.3) is 2-fold higher than the PVDF/PDDA-CNT. The stable dispersion of PSS-CNT is due to the repulsive nature existing between the individual CNTs caused by the attachment of charged polymer functional groups as same as intrinsic functional groups of the pristine CNT. This work signifies the role of synergy between the charged particles in the functional groups and charged nature of the filler influencing the performance of flexible strain sensors. The detailed investigation using various techniques reveals significance of selection of suitable polymers for functionalization by showing its influence in the context of designing the high-performance flexible strain sensor.

Construction of Aptamer‐siRNA Chimera/PEI/5‐FU/Carbon Nanotube/Collagen Membranes for the Treatment of Peritoneal Dissemination of Drug‐Resistant Gastric Cancer

Due to extensive metastasis, poor blood supply, and drug-resistant, there is still no effective clinical means to treat peritoneal dissemination of gastric cancer. Here, an aptamer-siRNA chimera (Chim)/polyethyleneimine (PEI)/5-fluorouracil (5-FU)/carbon nanotube (CNT)/collagen membrane is constructed, which could be divided into 15 layers with a thickness of 70-100µm. Sustained release experiments show that the collagen membranes can control 5-FU release for more than 2 weeks. Aptamer-siRNA chimera can specifically bind to gastric cancer cells, enabling targeted delivery of 5-FU and silencing drug-resistant gene. In vitro experiments demonstrated that Chim/PEI/5-FU/CNT nanoparticles promoted the apoptosis of 5-FU-resistant gastric cancer cells, inhibited their invasion and proliferation. Animal experiments show that Chim/PEI/5-FU/CNT/collagen membrane significantly inhibits the expression of mitogen-activated protein kinase (MAPK), and effectively treats peritoneal dissemination of 5-FU-resistant gastric cancer. Compared with siRNA/PEI/5-FU/CNT group, ki-67 proliferation index, and matrix metallopeptidase 9 (MMP9) expression are significantly decreased in the Chim/PEI/5-FU/CNT group, while the proportion of apoptotic cells is markly increased. In conclusion, a chimera/PEI/5-FU/CNT/collagen membrane is constructed, which can effectively treat peritoneal dissemination of drug-resistant gastric cancer. The study provides a new therapeutic approach for relevant clinical treatment.

Carbon Nanotube Reinforced Poly‐p‐Phenylene Terephthalamide Fibers for Toughness Improvement: A Molecular Dynamics Study

AbstractPoly‐p‐phenylene terephthalamide (PPTA) fibers, such as DuPont's Kevlar fiber, are widely used in various fiber‐reinforced composites due to their outstanding tensile stiffness, strength, and energy absorption capacity. To further improve the strength of PPTA‐based fibers, it is necessary to investigate the molecular deformation mechanisms of these fibers while being coupled with nanoreinforcements. In this work, molecular dynamics method is used to predict the mechanical performance of carbon nanotubes (CNTs) reinforced Kevlar fibers, based on the molecular modeling of crystal interfaces in the microstructure of Kevlar fiber with the help of surface‐modified CNTs, the tensile strength of Kevlar fibers can be increased by 27.8–39.7%. Furthermore, the mechanism of binding stability of CNTs is investigated by modifying the functional groups of CNTs, in which the hydrogen bonds (H‐bonds) interaction plays an important role.

Scattering of Ultrashort X-ray Pulses by Various Nanosystems.

Currently, the study of the scattering of ultrashort X-ray pulses (USPs) by various objects is an urgent task, in connection with the creation of powerful sources of USP generation. In this paper, the theory of the scattering of attosecond pulses by polyatomic structures is developed taking into account the magnetic component of USPs. It is shown that the scattering spectra depend not only on the structure of the target, but also on other characteristics of USPs. Results are presented of the calculation of the scattering spectra on various nanosystems, such as rings, groups of rings, carbon nanotubes (CNTs), and groups of co-directed CNTs (forest CNTs). The calculation results are presented in an analytical form, which allows a general analysis of the expressions. It was found that taking the magnetic component of the momentum into the scattering spectra into account leads to the generation of the second harmonic. In this case, the spectra have characteristic features and differ from the scattering spectra at the carrier frequency, which can complement ultra-high-resolution X-ray analysis. It is shown that the scattering spectra of some structures, for example, forest CNTs, have a strictly specified radiation direction and such material in the field of such USPs is non-reflective (completely black).

Robust tuning metal/carbon heterointerfaces via ketonic oxygen enables hydrogen evolution reaction outperforming Pt/C

Large-scale synthesis of metal/carbon hybrids with tunable metal/carbon heterointerfaces is vital for practical application of such hybrids in electrocatalysis. Herein, we developed a facile route for large-scale crafting of ultrafine Ru nanoparticles (NPs) anchored on the ketonic CO groups of carbon nanotubes (CNTs) (9.6 g in one batch). From both experimental results and theoretical calculations, we demonstrate that CO (rather than C–O) groups can be exploited to engineer the heterointerface of CNTs and Ru NPs. In fact, the electronic structure of Ru becomes considerably improved because the high polarity of CO facilitates the interface electron transfer of Ru/CNTs. Consequently, the obtained Ru-O-CNTs hybrids with low Ru loading of 1.5 wt% display a small overpotential of 25 mV at 10 mA cm−2 and with fast kinetics as deduced from a small Tafel slope of 20.4 mV dec−1 for hydrogen evolution reaction (HER) in 1 M KOH. Impressively, at 70 mV overpotential, the hybrids exhibit a record mass activity of 20.4 mA μg−1Ru, which is more than 50-fold of that for commercial Pt/C. Therefore, for the first time, we identified the vital role of CO groups for engineering metal/carbon heterointerfaces towards robust and efficient electrocatalysis.

The role of solvents and oxygen-containing functional groups on the adsorption of Bisphenol A on carbon nanotubes

ABSTRACT The wide application of endocrine disruptors (EDs) has recently created great public concerns because of their toxicities. Previous studies have stated that the effect of oxygen-containing functional groups of carbon nanotubes (CNTs) for Bisphenol A (BPA) sorption, but no study has been quantified the exact contribution of the oxygen-containing functional groups. Moreover, the role of solvents on the adsorption of BPA should be considered. Considering the well properties of CNTs, graphitized (MG), carboxylated (MC) and hydroxylated (MH) multi-walled CNTs were selected as model adsorbents, BPA was used as model adsorbate. Solubility and single point adsorption coefficient (logK d) of BPA were n-hexadecane > water > methanol, suggesting that hydrophobic interaction was the main mechanism for BPA sorption on CNTs. For different functional groups of CNTs, π-π interaction between MH and BPA may be stronger than that of MC, and thus the sorption of BPA on MH was higher than that of MC. Moreover, hydrogen bond resulted in the higher adsorption of BPA on MH when compared with MC. The oxygen-containing functional groups of CNTs played a key role for BPA sorption in methanol because the values of contribution were 20%–45% for -OH and were 5%–25% for -COOH. In n-hexadecane, other factors such as hydrophobic interactions should be considered because the contribution percentages of -OH were ca.15% and the values for -COOH were ca.10%. The results are expected to provide important information on the interaction of EDs and CNTs.

Surface modification of one-dimensional Carbon Nanotubes: A review for the management of heavy metals in wastewater

Abstract The quest for finding a suitable and robust material for environmental clean-up is a matter of prime concern. The application of an increasing number of Carbon Nanotubes (CNTs) based materials in environmental pollution management and their success stories are indicative of their capability to be used in wastewater treatment. Due to the tunable surface chemistry of CNTs, a lot of recent developments have taken place to enhance their performance in water remediation. Novel CNT composites have been synthesized by modification of surface groups of CNTs. Comprehensive documentation of their synthesis, as well as environmental applications, is much needed to promote their use on a larger scale. This paper is an extensive study of the recent literature on the application of novel CNT composites in the removal of heavy metals from wastewater and the effect of environmental chemistry on their performance. This paper aims at assisting readers in recognizing the loopholes in the applications of CNTs in real industries, which they might want to address.

Insights into the Electron-Transfer Regime of Peroxydisulfate Activation on Carbon Nanotubes: The Role of Oxygen Functional Groups.

Carbon-driven advanced oxidation processes are appealing in wastewater purification because of the metal-free feature of the carbocatalysts. However, the regime of the emerging nonradical pathway is ambiguous because of the intricate carbon structure. To this end, this study was dedicated to unveil the intrinsic structure-performance relationship of peroxydisulfate (PDS) activation by carbon nanotubes (CNTs) toward nonradical oxidation of organics such as phenol (PE) via electron transfer. Eighteen analogical CNTs were synthesized and functionalized with different categories and contents of oxygen species. The quenching tests and chronopotentiometry suggest that an improved reactivity of surface-regulated CNTs was attributed to the reinforced electron-transfer regime without generation of free radicals and singlet oxygen. The quantitative structure-activity relationships were established and correlated to the Tafel equation, which unveils the nature of the nonradical oxidation by CNT-activated PDS complexes (CNT-PDS*). First, a decline in the concentration of oxygen groups in CNTs will make the zeta potential of the CNT become less negative in neutral solutions, which facilitated the adsorption of PDS because of weaker electrostatic repulsion. Then, the metastable CNT-PDS* was formed, which elevated the oxidation capacity of the CNT. Finally, PE would be oxidized over CNT-PDS* via electron transfer to fulfill the redox cycle. Moreover, the nonradical oxidation rate was uncovered to be exponentially related with the potential of the complexes, suggesting that the nonradical oxidation by the CNT-PDS* undergoes a mechanism analogous to anodic oxidation.

Influence of Functionalized Carbon Nanotubes on Catalytic Activity of V2O5/TiO2‐CNTs for 1, 2‐Dichlorobenzene Oxidation

Carbon nanotubes (CNTs) with or without oxygen‐containing functional groups (e.g., hydroxy radical [─OH] and carboxyl [─COOH] group) were used in combination with titanium dioxide (TiO2) to support vanadium oxide as novel catalysts (i.e., V2O5/TiO2‐CNTs‐OH [V/Ti‐CNTs‐OH], V2O5/TiO2‐CNTs‐COOH [V/Ti‐CNTs‐COOH], and V2O5/TiO2‐CNTs [V/Ti‐CNTs]). These catalysts were used to catalytically decompose gaseous 1,2‐dichlorobenzene (1,2‐DCBz) at low temperature (150 °C). The results of this study indicate that the catalytic activity of V/Ti‐CNTs evidently improved by the introduction of oxygen‐containing functional groups, and particularly the V/Ti‐CNTs‐COOH catalyst showed excellent catalytic performance at low temperature. Oxygen‐containing functional groups in CNTs increase the active chemisorbed oxygen amount, thus improve both the oxygen delivery capability and the surface lattice oxygen mobility of the catalysts. The former guarantees an efficient 1,2‐DCBz oxidation and retards the catalyst deactivation in oxygen‐free atmosphere. The latter ensures the regeneration of the deactivated catalyst when oxygen is reinjected into reaction atmosphere. Or else, the surface oxygen vacancy caused by the consumption of surface reactive oxygen would be difficult to be replenished by the oxygen from atmosphere at low temperature (150°C). These results reveal the effect of oxygen‐containing functional groups on the structure‐catalytic property of V/Ti‐CNTs catalyst, suggesting that controlling the emission of chloro‐aromatic pollutants from incineration flue gas could be achieved by modifying the surface of the catalyst containing CNTs with proper oxygen‐containing functional groups. © 2019 American Institute of Chemical Engineers Environ Prog, 38: e13221, 2019

Carbon nanotubes-incorporated MIL-88B-Fe as highly efficient Fenton-like catalyst for degradation of organic pollutants

Iron-based metal organic frameworks have been verified to be efficient heterogeneous Fenton catalysts due to their open pore channels and highly uniform distribution of metallic centers. In these catalysts, however, the iron element is mainly in the form of Fe(III), which results in a process required to reduce Fe(III) to Fe(II) to initiate Fenton reaction. To address this problem, carbon nanotubes (CNTs) with electron-rich oxygen-functional groups on the surface were incorporated into the metal organic frameworks (MIL-88B-Fe) to improve Fe(II) content for an enhanced Fenton-like performance. The prepared CNT@MIL-88B-Fe (C@M) showed much stronger catalytic ability toward H2O2 than MIL-88B-Fe. The pseudo-first-order kinetic constant for phenol degradation by C@M (0.32 min–1) was about 7 times that of MIL-88B-Fe, and even higher than or comparable to the values of reported heterogeneous Fenton-like catalysts. Moreover, the Fenton-like system could effectively degrade various kinds of refractory organic pollutants and exhibited excellent catalytic activity over a wide pH range (4–9). XPS analysis confirmed that Fe(II) content of the catalyst gradually increased with CNT loadings. Electron spin resonance analysis showed that the signal intensity (•OH) of C@M was much higher than MIL-88B-Fe, which was consistent with the degradation efficiency of pollutants. Furthermore, the Fe(II) content of the catalyst gradually increased along with the oxygen-functional group content of CNTs. The result demonstrated that oxygen-containing functional groups of CNTs have a significant impact on the enhanced catalytic performance of C@M. This study provides a new insight to enhance Fenton reaction by using nanocarbon materials.

Fabrication and characterization of hyperbranched polyglycerol modified carbon nanotubes through the host-guest interactions

Carbon nanotubes (CNTs) are novel carbon composites that have received extensive research attention for biomedical applications thanks to their excellent cell membrane penetration capability and large specific surface areas. Nevertheless, the poor dispersibility in aqueous solution still perplexes the biomedical applications of CNTs. Although, there are many researched about that modify hydrophilic polymers to the surface of CNTs, facile and efficient strategies are still highly desirable to be developed. In this produce, an efficient and facile strategy for surface modification of CNTs with excellent water dispersibility was developed via supramolecular chemistry. On the one hand, we synthesize the β-CD-HPG via anionic polymerization. On the other hand, adamantane chloride was first reacted with the hydroxyl group of radiant CNTs through esterification to obtain CNT-Ad. Finally, it only need mild reaction conditions and fast reaction time (30 min) that β-CD-HPG form an exact 1:1 inclusion complex with CNT-Ad via host-guest interaction. The successful preparation of CNT-β-CD-HPG composites could be confirmed via a series of characterization techniques. Then, we further verify that CNT-β-CD-HPG composites possess the remarkable water dispersibility and enormous potential for controlled drug delivery systems. Therefore the facile strategy for the preparation of CNT-β-CD-HPG composites with excellent water dispersibility via supramolecular chemistry would possess rosy prospects in biomedical applications.

Polymer Composite Containing Carbon Nanotubes and their Applications.

Carbon nanotubes (CNTs) are attractive nanostructures in this regard, primarily due to their high aspect ratio coupled with high thermal and electrical conductivities. Consequently, CNT polymer composites have been extensively investigated for various applications, owing to their light weight and processibility. However, there have been several issues affecting the utilization of CNTs, such as aggregation (bundling) which leads to a non-uniform dispersion and poor interfacial bonding of the CNTs with the polymer, resulting in variation in composite performance, along with the additional issue of high cost of CNTs. In this article, recent research and patents for polymer composites containing carbon nanomaterial are presented and summarized. In addition, a rationale for optimally designed carbon nanotube polymer composites and their applications are suggested. Above the electrical percolation threshold, a transition from insulator to conductor occurs. The percolation threshold values of CNT composite are dependent on filler shape, intrinsic properties of filler, type of polymer, CNT dispersion condition and so on. Different values of percolation threshold CNT polymer composites have been summarized. The difference in percolation threshold and conductivity of CNT composites could be explained by the degree of effective interactions between nanotubes and polymer matrix. The reaction between surface functional groups of CNTs and polymer could contribute to better dispersion of CNTs in polymer matrix. Consequently, it increased the number of electrical networks of CNTs in polymer, resulting in an enhancement of composite conductivity. In addition, to exfoliate nanotubes from heavy bundles, ultrasonication with proper solvent and three roll milling processes were used. Potential reactions of covalent bonding between functionalized CNTs and polymer were suggested based on the above rationale. Through the use of CNT functionalization, high aspect ratio CNTs, and proper fabrication, uniform dispersion of nanotubes in polymer can be achieved leading to considerable improvement in electrical conductivity and electromagnetic interference (EMI) shielding properties.

A predictive model of the tensile strength of twisted carbon nanotube yarns

Due to the outstanding mechanical properties of individual carbon nanotubes (CNTs) at the nanoscale, CNT yarns are expected to demonstrate high strength at the macroscale. In this study, a predictable model was developed to predict the tensile strength of twisted CNT yarns. First, the failure mechanism of twisted CNT yarns was investigated using in situ tensile tests and ex situ observations. It was revealed that CNT bundles, which are groups of CNTs that are tightly bound together, formed during tensile loading, leaving some voids around the bundles. Failure of the CNT yarns occurred as the CNT bundles were pulled out of the yarns. Two stresses that determined the tensile strength of the CNT yarns were identified: interfacial shear and frictional stresses originating from van der Waals interactions, and the lateral pressure generated by the twisted yarn structure. Molecular dynamics and yarn mechanics were used to calculate these two stresses. Finally, the tensile strength of CNT yarns was predicted and compared with experimental data, showing reasonable agreement.