CNTs Content Research Articles

Effect of CNTs content on the microstructures and properties of CNTs/Cu composite by microwave sintering

Cu matrix composites reinforced with 0-3 wt% CNTs are fabricated via molecular-level mixing, microwave sintering and rolling technology. A homogeneous distribution of CNTs is exhibited in copper matrix. Clean CNTs/Cu interfaces perform high bonding strength. Electrical conductivity and relative density of microwave sintered CNTs/Cu composites decrease with increase in CNTs content. There exists maximum for hardness of CNTs/Cu composites which rise and then fall with the rise of CNTs content. When CNT contents are less than 1 wt%, it provides a good control over microstructures with low porosity and small pore size. Subsequent rolling process enables better microstructure and performance of sintered composites which shows tensile strength of 218 MPa, the elongation of 37.75%, and the electrical conductivity of >98% IACS compared to pure copper. Our studies provide a robust approach to high-performance CNTs/Cu composites by microwave sintering.

One step synthesis of FeCO3 nanorods interwind with carbon nanotubes as anode materials for lithium-ion batteries

FeCO3 nanomaterials have been intensely investigated as anode materials for LIBs due to their high capacity, low cost and natural abundance. Nevertheless, the slow diffusion of lithium ions and its low electronic conductivity in the bulk materials limit the power performance of FeCO3. Developing an efficient strategy to promote the durability of FeCO3 is important. Here, an effective method is reported to significantly enhance the capacity and durability of the FeCO3 as anode materials. The FeCO3/carbon nanotubes composites (FeCO3/CNTs) are prepared via a facile, economical and effective single step in situ crystallization route, using carbon nanotubes, ferrous sulfate and urea as raw materials. The effects of CNTs content on the morphology, electrochemical performances and cyclic stability are fully investigated for these FeCO3/CNT electrodes. The addition of moderate CNTs can remarkably improve the electrochemical performances of FeCO3. FeCO3/CNT-15 delivers an initial discharge capacity of 1436 mAh·g−1 at the current density of 200 mA·g−1 and maintains a capacity of 694 mAh·g−1 after 140 cycles. With the merits of high-performance, low cost and facile synthesis route, FeCO3 nanorods interwind with CNTs should be an attractive candidate as anode material for high-performance lithium-ion batteries.

Acquiring well balanced strength and ductility of Cu/CNTs composites with uniform dispersion of CNTs and strong interfacial bonding

Acquiring metal matrix composites with high strength and large ductility simultaneously is a critical issue, which determines their potential applications in industrial field. In this study, we reported that the well balanced high strength and ductility of Cu/CNTs composites can be achieved by combined effects of full densification, uniform dispersion of CNTs, strong interfacial bonding and suitable Cu matrix features. The interfacial bonding in Cu/CNTs composites is highly dependent on the sintering temperature and CNTs content. The related strengthening and toughening mechanisms were discussed according to the microstructure and related model. This study provides a new insight in fabricating CNTs-reinforced metal matrix composites with high strength and large ductility.

Enhanced electromagnetic properties of carbon nanotubes and SiO2-coated carbonyl iron microwave absorber

The carbon nanotubes/SiO2-coated carbonyl iron (CNTs/CI@SiO2) composites were fabricated as microwave absorption materials (MAMs) by a simple mechanical mixing method for the purpose of the MAMs with lightweight, thin thickness, broad bandwidth and high oxidation resistance. The effects of different concentration of CNTs on the electromagnetic properties of the CNTs/CI@SiO2 composites were investigated. The results indicate that the complex permeability does not change obviously with the increasing concentration of CNTs because of the constant concentration of CI@SiO2 in the composites. While the complex permittivity and attenuation constant increase with the increasing concentration of CNTs, and the impedance matching ratio decreases with the increasing concentration of CNTs. The reflection loss (RL) calculation results show that 2 wt% CNTs mixed with 65 wt% CI@SiO2 has the optimum microwave absorption properties. The minimum RL is −51.54 dB at 15.44 GHz with a matching thickness of 1.41 mm. The bandwidth corresponding to the RL below −10 dB is more than 6.08 GHz with a thickness of 1.5 mm. The enhanced microwave attenuation ability, improved impedance matching in air-absorber interface and the quarter-wavelength cancellation are believed to contribute the excellent microwave absorption properties of the CNTs/CI@SiO2 composites.

Investigation of wear behavior of as-plated and plasma-nitrided Ni-B-CNT electroless having different CNTs concentration

In the present study, the wear behavior of as-plated and plasma-nitrided Ni-B-CNT coatings was taken into investigation. Ni-B-CNT composite was deposited on AISI 4140 steel using different concentration of CNTs ranging from 0.2 to 1 g·L−1, in an electroless bath. After the plating process, all samples were plasma nitrided in an atmosphere comprising of 25%N2-75% H2, at 400 °C, for 4 h. The friction and wear behavior of the composite coatings were evaluated using a pin on disk method at an applied load of 10 N. The samples were then characterized by means of XRD, FESEM, microhardness and surface roughness measurements. Worn surfaces were further analyzed by FESEM and EDS spectroscopy. Microhardness results revealed that the maximum hardness of 1550HV was obtained for Ni-B 0.6 g·L−1 CNT plasma-nitrided sample. According to the results, increasing the CNTs concentration caused the as-plated Ni-B amorphous structure to change to semi-crystalline. Furthermore, the crevices formed during the hydrogen evolution reaction were observed to be filled up. Presence of CNTs not only decreased the grain size in the plasma-nitrided samples but also prevented excessive heat generation during the wear test, and thus the friction coefficient was declined during the test. Moreover, image of the worn surface of Ni-B 0.6 g·L−1 CNT plasma-nitrided sample indicated the smoothest wear trace with no apparent cracks and the highest wear resistance among all the samples was achieved. While, in Ni-B-1 g·L−1 CNT sample, agglomeration created asperities as well as large particles weakly bonded to the Ni matrix which ultimately led to an increase in the specific wear rate.

Effects of ionic liquids and thermal annealing on the rheological behavior and electrical properties of poly(methyl methacrylate)/carbon nanotubes composites

Poly (methyl methacrylate)/carbon nanotubes (PMMA/CNTs) composites with varying CNTs concentration were prepared, in which the CNTs were physically modified by two kinds of ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF6]), named B-CNTs and H-CNTs, respectively. The effects of ILs on the dispersion of CNTs and the rheological and electrical properties of PMMA/CNTs composites were investigated. It is demonstrated that the addition of ILs could significantly improve the CNTs dispersion in PMMA matrix, which as a result leads to the decrease of rheological percolation threshold and enhancement of the electrical conductivity of the composites. Compared with PMMA/B-CNTs, more homogeneous dispersion of CNTs, smaller rheological percolation threshold but higher threshold of electrical conductivity percolation could be found in PMMA/H-CNTs composites. The discrepancy between rheological and electrical conductivity percolation threshold could be ascribed to the stronger interaction between [HMIM][PF6] and CNTs than that of [BMIM][PF6] as evidenced by Fourier Transform Infrared (FTIR) results. Thermal annealing could apparently facilitate the electrical conductivity of both PMMA/CNTs and PMMA/B-CNTs but it has no obvious effect on that of PMMA/H-CNTs composites.

Effect of functionalization of carbon nanotubes on vibration and damping characteristics of epoxy nanocomposites

The vibration and damping characteristics of epoxy composites reinforced by pristine and functionalized multi-walled carbon nanotubes (MWCNTs) were investigated experimentally for potential use as integral passive damping elements in structural composite applications. The MWCNTs were introduced into the acetone solvent and then mixed with epoxy resin through a sonication process and mechanical stirring. The solvent was evaporated from the mixture by means of magnetic hot plate and the hardener was added once it was cooled down to room temperature. The MWCMTs/epoxy mixture was then injected into a mold to form the nanocomposite specimens. Nanocomposite specimens were fabricated for six different MWCNT loadings (0.02, 0.041, 0.061, 0.123, 0.25 and 0.37 wt%). Microstructural analysis, tensile and bending tests were carried out to examine the effect of pristine multi-walled carbon nanotubes (p-MWCNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs). The frequency response functions (FRFs), coherence and phase diagrams of nanocomposites were measured using a forced vibration technique. A periodic up-chirp signal was generated by a shaker to excite the cantilever nanocomposite specimen at the base. The damped natural frequencies and damping ratios were obtained for different loadings of MWCNTs. The experimental results indicated that the damped natural frequencies of p-MWCNTs/epoxy and f-MWCNTs/epoxy composites increased by adding MWCNTs up to 0.12 wt.%, and decreased at higher MWCNTs content. Addition of p-MWCNTs were improved the damping ratio of nanocomposites. While the damping ratios from f-MWCNTs at loadings of 0.02–0.06 wt.% were higher than those from p-MWCNTs, they did not increase at higher CNTs contents for the first mode of vibration.

Plasma-assisted catalytic conversion of NO over Cu-Fe catalysts supported on ZSM-5 and carbon nanotubes at low temperature

A series of Cu-Fe catalysts with fixed metal content and variable ratios of ZSM-5 and CNTs were used to investigate NO removal in a plasma-catalyst system at low temperature. The catalysts were characterized by BET, XRD, TGA, XPS, H2-TPR and NH3-TPD. The results showed that the catalyst promoted the NO conversion rate from only plasma system, and 1Z3C catalyst exhibited the best NO conversion rate of 86.1% at 191.5 J/L. Composite support promoted the catalytic activity at low temperature, and greatly improved the Cu2+ and Fe3+ concentration on the 1Z3C catalyst, both Cu2+ and Fe3+ contributed greatly to catalytic reaction of NO conversion. Chemisorbed oxygen also acted as activated sites for NO conversion. When the input energy was 75 J/L, the NO conversion rate decreased from 70% to 41% with adding 500 ppm SO2, which decreased with increasing SO2 concentration, while generation rate of SO3 was less than 0.2% in the combination system. In the presence of SO2, copper sulfate species, ferric sulfate species and ammonium sulfates generated on the surface of catalyst, which consumed Lewis acid sites and blocked the active sites, decreasing NO conversion rate.

Evaluación del efecto genotóxico y mutagénico en linfocitos humanos expuestos a nanotubos de carbono modificados

Objetivo: evaluar efecto genotóxico y mutagénico en linfocitos humanos expuestos a nanotubos de carbono (NTC) prístinos y dopados con Nitrógeno. Métodos: linfocitos humanos fueron expuestos a NTC dopados y prístinos (0.08, 0.09, 0.1mg/mL), se evaluó alteraciones cromosómicas e intercambio de cromátidas hermanas (ICH). Resultados: se presentaron rupturas cromatídicas y cromosómicas en linfocitos expuestos a 0.1mg/mL y 0.08mg/mL de NTC prístinos. NTC dopados, indujeron cromosomas dicéntricos y anillos cromosómicos. Se presentó diferencia significativa en el porcentaje de ICH de células tratadas con NTC dopados versus control negativo y NTC prístinos (p<0.0001). Conclusión: la concentración más alta de NTC prístinos indujo daños cromatídicos y cromosómicos; aunque el porcentaje de la población con daño fue inferior al 10%, se consideran perjudiciales para las células. Linfocitos tratados con NTC dopados presentaron menores porcentajes de AC y altos valores en ICH, lo que muestra mayor reparación de material genético con estos compuestos.

Reinforcement of epoxy resin/carbon fiber composites by carboxylated carbon nanotubes: a dynamic mechanical study

The composites of epoxy resins reinforced with unidirectional carbon fibers were prepared via hot pressing of carbon fiber prepregs. Multiwall carbon nanotubes (MWCNT) derivatives [parent CNTs, low carboxylated CNTs (LCCNTs) and higher carboxylated CNTs (HCCNTs)] were incorporated into the epoxy resin/carbon fiber (E/C) composite. Interestingly, remarkable modifications as consequences of homogeneous dispersion of CNTs in E/C matrix and prevention of void formation within the composite wereachieved by using carboxylated CNTs. The dynamic mechanical analysis (DMA) showe dimproved glass transition temperature (Tg) and storage modulus of the resulting E/C/HCCNT composite. The master curves of storage modulus were constructed for the samples using the Vogel-Fulcher-Tammann (VFT) and Williams-Landel-Ferry (WLF) equations as well as the time-temperature superposition principle (TTS). The apparent activation energies of molecular rearrangements were calculated at different temperatures based on the numerical derivatives and WLF equations. The experimental results indicate that COOH content of CNTs can have a remarkable effect on the ultimate properties and performance of the E/C/CNTs nanocomposites. Based on possessing light weight and good modulus (of 31 GPa and 20.6 GPa at -90 °C and 80 °C, respectively), E/C/HCCNT can be consideredas an interesting composite for structural applications by polymer engineers.

Resistance of Chlorides-Induced Corrosion of Steel Bar Embedded in CNTs-OH Modified Concrete

Aim of this paper is to evaluate the influence of hydroxyl carbon nanotubes (CNTs-OH) content (by 0.1-0.5% of cement weight) on the resistance of chlorides-induced corrosion of steel bar embedded in concrete. The corrosion process of concrete was monitored by using half-cell potential method (Ecorr, mv CSE). Test results show that the addition of CNTs-OH considerably increased the resistance of rebar chlorides induced corrosion of concrete, and the optimum content of CNTs was about 0.3% by mass of cement. Simultaneously, results also indicate that the measuring position impacted the corrosion potential value, in which the point on the water/air interface had the highest corrosion probability. In addition, the water absorption and SEM of concrete containing CNTs-OH were also investigated, and the pore-filling effect of CNTs-OH was observed to improve the properties of concrete.

Synergistic effect of non-covalent interaction in colloidal nematic liquid crystal doped with magnetic functionalized single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs), CNT@Fe3O4, and Fe3O4 nanocomposites were doped to eutectic uniaxial nematic liquid crystal (NLC's) (E5CN7) to improve physiochemical properties such as phase transition temperature, activation energy (Ea), dielectric anisotropy, and electro-optical properties. The thermal study of nematic phase shows a decrease in the nematic to isotropic phase transition temperature as CNT is doped. However, higher doping concentration of CNTs leads to the further increase in transition temperature. The anchoring effect or π-π interaction plays a key role in N-I phase transition. The functionalization of SWCNTs with Fe3O4 diminishes the CNT aggregation while the magnetic susceptibility is increased. The functionalized CNT doping to NLC's decrease significantly the phase transition temperature compared to doping of non-functionalized CNTs. Attractive interaction between guest and host molecules by magnetic and geometry effect increased the enthalpy and entropy of phase transition in the SWCNT@Fe3O4 sample compared to non-functionalized CNT doped system. Also, the Ea values are decreased as SWCNT@Fe3O4 is doped to pure E5CN7. The difference of N-I phase transition temperature was observed in Fe3O4 and CNT@Fe3O4 compared to SWCNT doped systems. Finally, dielectric anisotropy was increased in the doped system compared to pure NLC.

Effect of hybrid ratio on friction and wear behavior of AZ91D matrix nanocomposites under oil lubricated conditions

Abstract Friction and wear behavior of AZ91D and its nanocomposites reinforced by different contents of hybrid multi-walled CNTs and nano-SiC particulates under oil lubrication was investigated using a MRS-10P four-ball tribometer. Friction coefficients and wear rates were measured within a load range of 200–1000 N at a spindle rotary speed of 380 r/min. Worn surface morphologies, phase and element compositions were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The mechanism of synergistic effect of CNTs and SiC nanoparticles was discussed. The results indicate that the AZ91D nanocomposites show better wear resistance properties and different wear mechanisms compared with AZ91D. The AZ91D nanocomposites reinforced with 0.5% CNTs and 0.5% nano-SiC have the best tribological capacity. The wear mechanisms for the Mg-based hybrid nanocomposites appear to be a mix-up of micro-ploughing, micro-cutting, slight adhesive wear and delamination.

Effect of Carboxylic CNTs Filling on Mechanical Behaviors of Basalt Fiber/Epoxy Composites

In order to improve the mechanical properties of basalt fiber/epoxy composites, carboxylic CNTs were filled into the epoxy matrix of basalt fiber/epoxy composites. Firstly, the carboxylic CNTs filled epoxy composites with different carboxylic CNTs content were studied. Quasi-static and dynamic compression results show that when the content of carboxylic CNTs increased from 0wt% to 1wt%, both ultimate quasi-static and dynamic compressive strength of CNTs filled epoxy composites showed increasing tendencies. However when the content of carboxylic CNTs increased from 1 wt% to 1.5 wt% both ultimate quasi-static and dynamic compressive had decreasing tendencies. Base on above results, carboxylic CNTs (1wt%) filled basalt fiber/epoxy composites were fabricated by mould pressing method. Quasi-static and dynamic compression results showed that both ultimate quasi-static and ultimate dynamic compressive strength of carboxylic CNTs filled basalt fiber/epoxy composite were enhanced compared with those of basalt fiber/epoxy composites without CNTs. However, the critical failure strain were all lower than those of basalt fiber/epoxy composites without CNTs. Failure mechanism analysis showed that the carboxylic CNTs was beneficial for forming good interfacial bonding between epoxy matrix and basalt fibers, and the advantage of high axial tensile strength of basalt fibers could be fully utilized, which is responsible for the enhanced ultimate compressive strength of carboxylic CNTs filled basalt fiber/epoxy composites.

The effect of sintering temperature on Cu-CNTs nano composites properties produced by PM method

In this research work, copper and CNTs have been processed using high energy milling in different milling times (5, 10 and 15 hours). FESEM and XRD have been used to characterize the milled powders. The FESEM micrographs of the milled powders indicated that the morphology of powders changed from spherical shape to flake as milling time increased. The effect of sintering temperature as well as CNTs content on the properties of Cu-CNTs nanocomposite has been investigated. The optimum sintering temperature to produce Cu-CNTs nanocomposites is determined to be 900 oC. The microstructure and phase analysis of Cu-CNTs nanocomposites were studied by field emission scanning electron microscopy and X-ray diffraction. Mechanical properties of nanocomposite samples at various sintering temperatures were investigated. Cu-CNTs nanocomposite with 4 vol.% CNTs fabricated by powder metallurgy method indicated the highest value of the micro-hardness and bending strength as compared to pure copper.

Preparation and characterisation of nano enhanced phase change material by adding carbon nano tubes to butyl stearate

A nano enhanced phase change material, NEPCM, was prepared by the addition of carbon nanotubes, CNTs, to butyl stearate. This study utilised single walled nano tube, multi-walled nanotube and modified multi-walled nanotube. Several kinds of surfactants were used to stabilise nano-particles in butyl stearate. Tetramethyl ethylene diamine (TEMED) was the best surfactant for enhancing the stability time of nano-fluid. The effect of CNTs concentration on the thermal properties of base fluid was studied and it was found that for all kinds of CNTs, the highest thermal conductivity of NEPCM was observed in weight fraction of 0.03. The modified-MWCNTs have the most enhancements in the butyl stearate thermal conductivity. It was found from differential scanning calorimetry tests, that modified-MWCNTs with 2 wt.% contents have the most effect on the latent heat of fusion of the base fluid. It was also observed that the SWCNT has a considerable effect on the melting point of PCM.

An electrodeposition approach to obtaining carbon nanotubes embedded copper powders for the synthesis of copper matrix composites

CNTs/Cu composite powders were fabricated using an electrodeposition process, and consolidated by hot pressing followed by cold rolling. The electrodeposition is a promising method to obtain homogeneously dispersed CNTs/Cu powders in terms of effective control of CNTs content and particle size of powders during the process. The effects of Cu ions concentration in electrolyte on the dispersion and content of CNTs in powders, particle size, and properties of composites were studied. The electrodeposited CNTs/Cu powders show large amount of embedded CNTs that are strongly bonded with the Cu matrix, and a CNTs network architecture formed in the Cu grains. The particle size 52.72 μm of powders is obtained at Cu ions concentration of 10 g/L in electrolyte. The tensile strength and electrical conductivity of consolidated CNTs/Cu composites are about 418 MPa and more than 90 ± 0.16% IACS, respectively. The CNTs network is beneficial to load transfer efficiency and bridge linking for improving strength, but also provides electron transport pathways for high electrical conductivity.

The negative permittivity behavior of carbon nanotubes/yttrium iron garnet composites in the radio frequency

The composites with negative permittivity have drawn intensive attentions due to their promising candidates for double negative materials (DNMs). In this work, dielectric properties of the carbon nanotubes/yttrium iron garnet (CNTs/YIG) composites with different CNTs content have been researched in radio frequency. When CNTs content exceeds percolation threshold, the CNTs interconnect with each other and form conductive networks. Then the negative permittivity is obtained and can be attributed to the motion of charge carriers along the CNTs networks in the CNTs/YIG composites. In addition, with CNTs content raising, the gradually electron densities result in effective adjustment of negative permittivity in different frequency ranges. Therefore, the CNTs/YIG composites with tunable negative permittivity have great potential to be DNMs.

Effect of single and multi-wall carbon nanotubes on the mechanical properties of Gd-123 superconducting phase

The influence of single wall carbon nanotubes SWCNTs and multi wall carbon nanotubes MWCNTs on Vickers microhardness of Gd-123 superconducting phase is studied. Samples of type (SWCNTs)x and (MWCNTs)xGdBa2Cu3O7−δ, composite where, 0.0≤x≤0.1wt.%, are prepared by solid-state reaction technique. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM). Moreover the samples are examined by measuring electrical resistivity and Vickers microhardness. The obtained results showed an enhancement in the phase formation and grains connectivity up to 0.06 and 0.08wt.% for SWCNTs and MWCNTs added samples, respectively. Likewise the superconducting transition temperature Tc was improved at a low content of CNTs but it suppressed for higher concentrations. In addition, the analysis of Vickers microhardness measurements suggests that the most suitable model that describes the behavior of our sample is proportional specimen resistance PSR model.

Mussel-Inspired Dopamine and Carbon Nanotube Leading to a Biocompatible Self-Rolling Conductive Hydrogel Film.

We report a novel self-rolling, conductive, and biocompatible multiwall carbon nanotube (MWCNT)-dopamine-polyethylene glycol (PEG) hydrogel film. The gel can self-fold into a thin tube when it is transferred from a glass slide to an aqueous environment, regardless of the concentrations of the MWCNT. The film presents a highly organized pattern, which results from the self-assembly of hydrophilic dopamine and hydrophobic carbon nanotubes. By exploring the biomedical potential, we found that MWCNT-included rolled film is nontoxic and can promote cell growth. For further functional verification by qPCR (quantitative polymerase chain reaction), bone marrow derived mesenchymal cells present higher levels of osteogenic differentiations in response to a higher concentration of CNTs. The results suggest that the self-rolling, conductive CNT-dopamine-PEG hydrogel could have multiple potentials, including biomedical usage and as a conductive biosensor.