CNT Content Research Articles

Плазмонная активация и тушение люминесценции растворов полифениленвинилена (MEH-PPV) одно- и двустенными углеродными нанотрубками

Spectral-luminescent properties of benzene and toluene solutions of poly[2-methoxy, 5-(2’- ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) with additives of single - and double-walled carbon nanotubes (CNTS) were studied in order to detect manifestations of plasmon properties of CNTS in the luminescence of MEH-PPV solutions. It was found that the dependence of the luminescence intensity of the polymer solution on the CNT concentration is non-monotonic: with an increase in the number of dissolved nanotubes, this intensity initially increases, and then decreases. At the same time, the deformation of the light spectrum itself practically does not take place. The effect was observed as when using a single-walled CNT (swcnt) and double wall (DWNT). The depth of modulation of the glow intensity in the case of DPT was higher than in the case of ount. To explain the observed dependencies, various variants of the electro-dynamic model of activation-quenching of MEH-PPV luminescence by carbon nanotubes are proposed. Direct modeling of near and far field characteristics is performed based on Maxwell's equations, for numerical solution of which the finite difference method in the time domain (FDTD) is used. Computational experiments have shown that CNTS with a MEH-PPV layer have directional antenna properties, acting as a kind of waveguides. Thus, the energy of radiation that reached the far zone in the direction of the nanotube axis was an order of magnitude higher than in the case of a solution without CNT. Fan-type electromagnetic waves emanating from both ends of the nanotube were detected, as well as the stage of plasmon waves beating, which characterizes the nanotube as a waveguide. Molecular dynamic modeling of the configurations of the adsorbed MEH-PPV chain in various solvents, both on a single CNT and on two parallel CNTS with a variation in the distance between them, was performed. It was found that as the distance between CNTS increases, the conformational structure of MEH-PPV becomes more loose: there is an increase in the number of large loops of the macrocycle in the bulk phase of the solution

Monitoring CNT-Based Composite Laminates under Monotonic and Cyclic Flexural Loading

The application of composite components in the load-carrying structure boosts the booming of health monitoring techniques so that the crucial damages information inside the composite can be perceived to ensure the secure state of the whole composite. This paper presents a promising self-sensing nanocomposite equipped with carbon nanotube buckypaper sensor to realize the health monitoring function. The CNT-based composite laminates with different contents were compared under monotonic and cyclic flexural loading. The sensor with lesser content of CNT proved to be more qualified for strain monitoring and damage prediction with high sensitivity, stability, and durability.

Microstructure and mechanical properties of MWCNT/Ti6Al4V composites consolidated by vacuum sintering

Ti6Al4V alloys with low weight, high corrosion resistance, high melting point, high biocompatibility and unique mechanical properties have been receiving great attention for wide applicability in many industry fields such as automobiles, aerospace and biomedical. However, Ti6Al4V tends to be easily oxidized at high temperature, exhibit low thermal conductivity, low hardness and low yield strength and thus have led to the limitation of applicability in many industries. In this study, we have fabricated Ti6Al4V matrix composites reinforced with multi-walled carbon nanotubes (MWCNT) to enhance the hardness and yield strength. Vacuum sintering technique has been used to prepare MWCNT/Ti6Al4V composites. Microstructural and phase studies indicated that the composite structure consists of two main phases including ?-Ti and ?-Ti and MWCNTs were uniformly dispersed in Ti6Al4V matrix. The relative density of composite decreases as the CNT content increases as resulted from the porous structure of the CNT, which limits the aggregation process of the composite. When the CNT content increased, the hardness and yield strength of the composite increased, reaching maximum values of 378 HV and 356 MPa with 2 vol.% MWCNTs, which are nearly 16 and 38% higher than those of Ti6Al4V alloy. The enhancement in hardness and compressive strength is attributed to the good mechanical properties of MWCNTs and load transfer effect from Ti6Al4V alloy matrix to reinforcement material.

Thermoelectric properties of PEDOT: PSS and acid-treated SWCNT composite films

We investigated the thermoelectric properties of composite films that consist of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and single-walled carbon nanotubes (SWCNTs). Thin films with 5−10 μm thickness of PEDOT:PSS/SWCNT and PEDOT:PSS/acid-treated SWCNT (AC-SWCNT) were prepared by varying the CNT content to determine their power factor. Both PEDOT:PSS/SWCNT and PEDOT:PSS/AC-SWCNT films showed an increase in their power factors with CNT content. The power factor values of PEDOT:PSS/AC-SWCNT films were higher than those of PEDOT:PSS/SWCNT films over the entire experimental range, which was mainly attributed to the significantly increased electrical conductivity. Thus, a series of PEDOT:PSS/AC-SWCNT freestanding films with 100−250 μm thickness were synthesized, and the same sample was used to measure electrical conductivity, Seebeck coefficient, and thermal conductivity to calculate the in-plane figure-of-merit ZT values. The composite films exhibited lower ZT values than those of PEDOT:PSS and AC-SWCNT films because of the high in-plane thermal conductivity caused by the dimensional anisotropy of AC-SWCNTs.

Effects of the CNT Content and Plating Solution pH After Purification on the Performance of Ni–P/CNT Composite Coating

After CNTs were purified, Ni–P/CNT composite coating was prepared at different CNT contents and plating solution pH values by univariate experimental method. Besides, the surface appearance, hardness, corrosion resistance and wear resisting property of the coating were tested and analyzed by X-ray diffractometer, scanning electronic microscope, microhardness tester, electrochemical workstation, tribometer and other means. The results suggest that fibers on the surface of purified CNTs are clear and well dispersed. During dummy plating, purified CNTs were more likely to deposit on Ni–P coating. A proper amount of CNTs could reasonably improve the structure of Ni–P/CNT composite coating; different pH values would lead to different specific gravities of alloying elements and CNT deposition, and a reasonable pH value would help the coating reach the optimal hardness, wearability and corrosion resistance. In general, Ni–P/CNT composite coating has the best comprehensive performance when the CNT content is 40 mg/L and pH value is 6.

Multifunctional cement-based materials modified with electrostatic self-assembled CNT/TiO2 composite filler

Owing to its good conductive property, dispersion, and low water absorption property, the electrostatic self-assembled CNT/TiO2 composite filler is an excellent candidate for developing multifunctional cement-based materials. Therefore, this study fabricated multifunctional cement-based materials with a CNT/TiO2 composite filler and explored their electrical properties, thermal-resistance effect, electromagnetic shielding and absorption properties. CNT/TiO2 modified cement-based materials showed percolation characteristics through direct current (DC), alternating current (AC) resistivity methods and percolation theory, with percolation threshold zone ranging from 0.15 vol% to 0.45 vol%. The AC impedance spectrum of the CNT/TiO2 modified cement-based materials can be accurately described by equivalent circuits, which change in the percolation threshold zone. The resistivity of the CNT/TiO2 modified cement-based materials decreased with increasing temperature, which has potential application in smart infrastructures. With increasing CNT/TiO2, the rate of decrease of the electrical resistivity of the composites changed sharply during the percolation threshold zone for increasing temperature from −30 °C to 60 °C. The electromagnetic shielding effectiveness of CNT/TiO2 modified cement-based materials was up to 1.30 times greater than that of the control cement-based materials. When the CNT content was 1.16 vol%, the reflectivity of the cement-based composite reached −32.01 dB at a frequency of 16.88 GHz.

Electrical, thermal, and mechanical properties of polypropylene/multiwalled carbon nanotube micromoldings

AbstractIn this paper, properties of microparts molded from polypropylene/multiwalled carbon nanotubes (PP/CNT) composites were studied in detail. Results indicated that the percolation threshold of PP/CNT microparts shifted to higher filler concentrations when compared with their compression molded counterparts. Morphology observations revealed that the distribution of CNT is not uniform along the flow direction, which can significantly affect the properties of microparts. The thermal properties of PP and PP/CNT composites as well as corresponding microparts were investigated using differential scanning calorimetry and thermogravimetric analysis, respectively. Moreover, the mechanical properties of microparts were evaluated by nanoindentation analysis. Multicycling measurements indicated that the mechanical properties of microparts are both depth and location dependent. Both the hardness and elastic modulus increased with corresponding filler loading concentration of CNT below 3 and 7 wt%, respectively. Above those concentrations, both properties decreased with an increase of CNT concentration. This could be related to the state of filler distribution within the microparts.

EFFECT OF HYBRID CARBON BLACK/CARBON NANOTUBES FILLER ON VULCANIZATES RELAXATION BEHAVIOR

The glass transition in hybrid carbon black/carbon nano-tube (CB/CNT) filled elastomer composites has been studied through dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The storage modulus E' and loss tangent (TanD) are recorded from -100 to 100 ° C and a frequency of 10 Hz. The thermal analysis was carried out at 2° C/min temperature increment. The vulcanizates were made as per conventional technology. The CNT were introduced into rubber compounds as CB/CNT masterbatches resulting from joint ultrasound processing. The CNT content in the rubber compounds varied from 0.1 to 0.5 phr. The DMA data proved that introduction of CB/CNT hybrid particles resulted in the spread of TanD temperature peaks for all the samples towards lower temperatures and the subsequent shift of the maximum TanD position by 4.0 to 15.6 degrees. The DSC data demonstrated the existence of additional low-temperature α-relaxation transitions in the modified vulcanizates (-123…-118 °C). The observed relaxation behavior could be explained by the increase in vacant volume in the vulcanizates along with the rise in segmental mobility of some macromolecules when compared against the reference sample. The highest hybrid filler content vulcanizate demonstrated certain TanD drop in the glass-to-rubber transition zone and the TanD rise in the high-elasticity state, which fact indicated formation of additional filler-filler interactions. Thus, the CNT treatment with carbon black resulted in a synergy effect upon the rubbers' dynamic characteristics; hence, it can be applied to the task of raising the material frost resistance point.

Impact of CNT on structural, thermal, and dielectric properties of the multicomponent Cu5Se75Te10In10 chalcogenide glassy system

Multicomponent MWCNT-added glasses of the [(Cu5Se75Te10In10)100−x(CNT)x] (x = 0, 1, and 2) system have been developed by a cost-effective melt-quench method that is also known for its convenience. Structural properties have been studied using XRD and FESEM. Differential Scanning Calorimetry scan has been done at a heating rate of 10 K/min which also confirms the glassy nature of the as-prepared and MWCNT-added Cu5Se75Te10In10 composite. The effect of CNTs on transition temperatures, thermal characteristics such as thermal stability and Glass-forming stability has been discussed. The variations of dielectric relaxation of this new composite with temperature and frequency have been investigated from room temperature up to 373 K and frequency regime from 1 Hz to 1 MHz. Moreover, it is also observed that dielectric constant and dielectric loss reduces sharply at the high-frequency side but increases with increase in CNT concentration as well as temperature. The highest dielectric constant value (2000) for 2 wt% MWCNT/Cu5Se75Te10In10 at low temperatures and the low-frequency regime is approximately ten times greater than the host glassy composite Cu5Se75Te10In10 was observed.

Photo-Fenton reaction for the degradation of sulfamethoxazole using a multi-walled carbon nanotube-NiFe2O4 composite

In this study, magnetically recyclable spinel nickel ferrite (NiFe2O4) and multi-walled carbon nanotubes (MWCNTs) incorporated NiFe2O4 (NiFe-CNT) composite with different CNT contents were successfully synthesized by one-step hydrothermal treatment. The photo-Fenton efficiency of the synthesized materials was assessed by the degradation of recalcitrant sulfamethoxazole (SMX) under ultraviolet (UV)-A and visible light. The efficiency of poorly active NiFe2O4 was significantly enhanced by the incorporation of 25 wt% CNT, and complete degradation of SMX (5 mg/L) was achieved within 2 h using NiFe-CNT composite (0.025 g/L) in the presence of H2O2 under UV-A light. Higher mineralization (total organic carbon (TOC) removal = 68%) was obtained in case of NiFe-CNT composite than bare NiFe2O4 (TOC removal = 39%). The effects of catalyst dosage, SMX concentration, H2O2 concentration, and pH on the degradation of SMX were investigated in order to identify the optimized reaction conditions. No leaching or degradation of MWCNTs was observed in the reaction solution and iron leaching from the composite was also under permissible limits. Photocurrent and Electrochemical Impedance Spectroscopy studies were performed to check the effective charge separation. The improved photocatalytic activity of the NiFe-CNT composite reflects (1) the synergy effect between NiFe2O4 and MWCNTs, (2) effective charge separation that retards the recombination of photogenerated charges, and (3) the generation of more reactive oxidation species (especially OH radicals). Moreover, ease of separation due to the significant magnetic properties of the NiFe-CNT composite provides an efficient method to treat recalcitrant organic pollutant.

CNT-CuO catalyzed C–N bond formation for N-arylation of 2-phenylindoles

Carbon nanotube–copper oxide (CNT–CuO) nanocomposites were prepared by depositing CuO nanoparticles onto functionalized CNT surfaces. The structure and elemental content of CNT–CuO were characterized using transmission electron microscopy, X-ray diffraction, and Auger electron spectroscopy. The prepared CNT-CuO was subsequently employed as a catalyst for the coupling reaction of 2-phenylindole with aryl iodides to provide the desired N-aryl 2-phenylindoles in good yields.

Structural, mechanical and corrosion properties of CNT-304 stainless steel nanocomposites

In this work, a systematic investigation was performed on the structural, mechanical and corrosion properties of CNT incorporated 304 stainless steel. Various concentrations of CNT from 0.5 to 4 wt% were incorporated into the 304 stainless steel matrix to investigate the feasibility of fabrication and enhancement of strength and other material properties. The fabrication of CNT-steel composite was achieved through a spark plasma sintering process at a sintering temperature of 800 °C. Raman and morphological studies confirmed that the CNT structure was retained in the sintered pellets. Optimum performance was found at 0.5 wt% CNT giving a Vickers hardness of 351 Hv and compressive yield strength of 404 MPa which were 5.5 and 2.0 times, respectively, those of pristine steel. Corrosion studies with 3.5 wt% NaCl solution revealed a slight increase in the corrosion rate for CNT dispersed samples.

Skin-Inspired Humidity and Pressure Sensor with a Wrinkle-on-Sponge Structure.

Sensors with multifunctions have attracted great attention for their extensive application value, among which humidity sensing and pressure sensing are necessary to electronics undoubtedly because of the complex physical environment we live in. Inspired by the structure of skin, in this article, we design a new method to combine wrinkle structure with porous sponge structure and achieve a novel, flexible, compressible, and bifunctional sensor based on carbon nanotube-polydimethylsiloxane (CNT-PDMS) with functions of humidity sensing and pressure sensing. The performance of the humidity sensing part can be controlled by the ultraviolet and ozone (UVO) treatment time and CNT concentration, while the sensitivity of the pressure sensing part can be controlled by the CNT concentration and grinding time of sugar granules. The bifunctional sensor can easily sense approaching and touching of a hand, which shows great potential of alarming and protecting some electronics. Moreover, the bifunctional sensor can also be used in detecting human joint motions and breath conditions as a wearable and flexible health monitor.

Role of interface on damping characteristics of multi-walled carbon nanotube reinforced epoxy nanocomposites

In this report, we propose an experimental approach to determine the role of the epoxy-CNT interface on damping by designing two systems of composites which differ in the interfacial area. The composites are namely ‘dispersed’ and ‘layered’. The CNTs were uniformly distributed in the epoxy matrix of the dispersed nanocomposites. Whereas, in the layered nanocomposite, a layer of CNT was sandwiched between two epoxy sheets. Image threshold technique was adopted to characterize the CNT spread area in the epoxy matrix. The epoxy-CNT interfacial area is assumed to be less than the CNT spread area due to the agglomeration of CNTs. The CNT spread area of dispersed nanocomposites was found to be 30 times higher than that of the layered composite. In addition to this, it is observed with microstructure analysis using scanning electron microscope and transmission electron microscope that the dispersed nanocomposites were comprised of more epoxy-CNT interfaces, and the layered nanocomposites have more CNT-CNT interfaces. At a particular CNT content, at the glass transition temperature, higher dynamic loss factor was characterized with dispersed nanocomposites. The energy dissipating nature of the epoxy-CNT and CNT-CNT interfaces were studied by analyzing the microstructural mechanisms of damping related to the system of composites dealt with this study.

Carbon Nanotube Fabric-Based Composites for Development of Multifunctional Structures

ABSTRACTCarbon nanotubes (CNTs) possess impressive properties along with low density. Integration of CNTs in the form of fabrics or other preformed assemblies simplifies their handling and allows for the higher CNT content needed to better leverage their properties in multifunctional structures. Here we describe production of non-woven CNT-polyurethane fabrics made from industrial-grade CNTs via a one-step filtration method. Individual sheets were scaled to 30 cm x 30 cm size and subsequently used to fabricate thicker composites, including via lamination with itself to produce simple panels and with other materials to further tailor the nanocomposite properties and address several example applications including electrical heating, fire resistance, electromagnetic shielding, and a skin for stretchable morphing structures.

Thermal Properties of Composite Materials Based on the Powder Systems “Copper–CNTs”

The influence of the metal matrix filling with carbon nanotubes on the thermal properties of copper-based powder composite materials has been studied. It has been revealed that the powder systems ″copper–CNTs″ obtained according to the powder-metallurgy technology by electric-contact sintering possess anisotropic thermal conductivity under certain conditions. It has been found that during uniaxial molding, in the process of electric-contact sintering, CNTs are oriented in one direction, which leads to a rise in the values of the thermal-conductivity coefficient in this direction. It has been established that at a CNT concentration below the percolation threshold, experimental values of the thermal-conductivity coefficient of the composite materials are in good correlation with the values obtained with the Maxwell–Garnett theoretical model. It was noted for the first time that the Maxwell–Garnett theoretical model can be used to assess the distribution of a nanosize filler in a metal matrix.

Simple model for hydrolytic degradation of poly(lactic acid)/poly(ethylene oxide)/carbon nanotubes nanobiosensor in neutral phosphate-buffered saline solution.

In this study, the hydrolytic degradation of poly(lactic acid) (PLA)/poly(ethylene oxide) (PEO) blend and PLA/PEO/carbon nanotubes (CNTs) nanobiosensors in neutral phosphate-buffered saline (PBS) solution was investigated by experimental and theoretical approaches. A simple model was developed to estimate the degradation fraction by applying the average degradation rate (K) and time exponent. The predictions of the developed model were compared to the experimental results. Moreover, CNT concentration, CNT size, sample thickness, diffusion coefficient, and concentration of the PEO phase influenced the K value. The impacts of the parameters on the degradation rate were studied to confirm the developed equation. All samples were rapidly degraded during the first week, while the degradation slowly progressed in the following weeks. The experimental and theoretical results demonstrate that CNTs quicken the degradation of samples. The degradation fraction of a nanobiosensor depends directly on the values of K and the time exponent. Furthermore, a high concentration of PEO, small thickness of the sample, high concentration of thin CNTs, and high diffusion coefficient desirably improve the degradation rate.

Modeling of CNT-reinforced nanocomposite with complex morphologies using modified embedded finite element technique

In this article, we overcome the limitations of traditional finite element (FE) method in modeling CNT-reinforced nanocomposites with complex morphologies by developing a modified embedded finite element (mEFE) method. The composite constituents in the mEFE model are discretized independently but simulated simultaneously as a coupled system. The major advantage of this approach is discretizing the matrix as a regular grid, irrespective of the complex nature of the CNT network. The developed modeling approach allowed us to simulate realistic representative volume elements (RVEs) containing randomly dispersed CNTs of different curvatures, orientations, aspect ratios and volume fractions. An advanced Monte Carlo based algorithm was also developed to generate complex CNT networks. The proposed mEFE method requires a significantly shorter preprocessing effort and is more computationally efficient when compared to traditional FE method. It allowed us to study large scale RVEs reinforced with high CNT concentrations. The results of this idealised case showed that the elastic modulus of the nanocomposite increases with increasing the volume fraction of the CNTs; reaching 200 % improvement at 5 % volume fraction. However, the enhancement in the properties was not obvious at higher concentrations due to the poor dispersion and agglomeration of the dispersed CNTs.

Reactive sintering of TiB2-SiC-CNT ceramics

TiB2-SiC ceramics with multi-wall carbon nanotubes (MW-CNT) were reactively hot pressed at 1800 °C and 30 MPa. Carbon nanotubes survived the process and could be clearly observed in the sintered ceramics. The in-situ exothermic reactions between TiC, B4C and Si accelerated the densification and produced nonporous TiB2-SiC ultrahigh-temperature ceramics within 1 min at 1800 °C. Although the toughness of the ceramic was not significantly affected by the CNT addition, remaining around 6 MPa m1/2, the CNT presence resulted in a substantial improvement in TiB2-SiC thermal shock resistance. The Vickers hardness decreased from 27 GPa for the CNT-free matrix to 21 GPa for ceramic with maximum CNT content (7.4 wt%).

Application of carbon nanotubes prepared from CH4/CO2 over Ni/MgO catalysts in CO2 capture using a BEA–AMP bi-solvent blend

Abstract Carbon nanotubes (CNTs) were synthesized by the chemical vapour deposition of methane and carbon dioxide over a Ni/MgO catalyst. The synthesized CNTs were then mixed with K/MgO catalyst at different ratios and used as the catalyst for CO2 absorption in butylethanolamine-2-amino-2-methyl-l-propanol bi-solvent blend. The catalysts were characterized using X-ray diffraction, scanning electron microscopy, butylethanolamine, thermal gravimetric analysis and temperature-programmed desorption of carbon dioxide in order to determine the characteristics responsible for good CO2-absorption performance. The results showed that, with the addition of a catalyst into the amine solution, the amine reached equilibrium CO2 loading faster than without a catalyst. Also, the increase in the CNT content of the KMgO/CNTs catalyst made the CO2 absorption reach equilibrium much more quickly compared with just KMgO alone and without a catalyst. The KMgO/CNTs at a ratio of 1:4 yielded the fastest time to reach CO2-loading equilibrium at 240 min, which was mainly due to the increase in strong basic sites as well as the highest total basic sites with an increase in CNT content. In addition, because of the extremely large specific surface area and pore volume generated due to the CNT, the number of exposed active centres per unit mass increased tremendously, leading to a corresponding tremendous increase in CO2 absorption.