CNTs Content Research Articles

Influence of CNTs Concentration on the Microstructure and Electrochemical Properties of Ni-P-MWNTs Composite Coating

Ni-P-multi-walled carbon nanotubes (Ni-P-MWNTs) composite coating was successfully co-deposited on 45 steel substrate by electroless plating. The microscopic morphology of Ni-P-MWNTs composite coating was observed by SEM. The influences of CNTs concentration in plating bath on the microstructure and corrosion resistance of the composite coating were investigated. The results indicated that the deposited composite coating shows dispersed CNTs and continuous Ni-P matrix, and there are no pores and cracks and other defects at the interface between the substrate and composite coating, and the thickness of the composite coating is about 50 μm. The Ni-P-MWNTs composite coating with 0.3g/L CNTs in bath displayed the best corrosion resistance, the corrosion potential of the composite coating is-0.372V.

Effect of strain rate on tensile properties of polyurethane/(multiwalled carbon nanotube) nanocomposite

In this research, polyurethane (PU)/(carbon nanotube) (CNT) samples, with two different contents of multiwalled carbon nanotubes (MWCNTs; i.e., 0.5 and 1.0 wt%) were fabricated through a solution casting method. To investigate the effect of strain rate on tensile properties, tensile tests were done on standard samples at constant temperature and different strain rates (2 × 10−5 to 2 × 10−2 s−1). Eyring's model was performed to clarify the role of both strain rate and CNTs content on activation volume and activation enthalpy of PU. To elucidate the role of strain rate and CNTs content on fracture behavior of PU, fracture surfaces of some samples were also investigated by scanning electron microscopy. The results of tensile tests show the intense effect of strain rate on tensile properties of PU/MWCNTs nanocomposites. Also, it was proved that the dependency of tensile properties of PU nanocomposites on strain rate decreases as CNTs content increases. The microscopic observations of the samples also demonstrate that increasing the strain rate changes the behavior of the fracture surface to less a ductile fracture, and increasing CNTs content causes much surface roughness. Finally, by investigation of the activation enthalpies, it is confirmed that much higher enthalpy is needed to fracture the samples with increased MWCNTs content, as the activation enthalpy changes from 45 for neat PU to 131 kJ/mol for PU/(1% MWCNTs) samples. J. VINYL ADDIT. TECHNOL., 22:356–361, 2016. © 2014 Society of Plastics Engineers

Different Carbon Nanotube Content and Dispersant on the Preparation of Fe<sub>3</sub>O<sub>4</sub> / CNTs

This article mainly introduced the preparation and properties of the thermal seed composite. And multiple groups of experiments have been done, which controlled by different content of carbon nanotubes, different surfactants. The results showed that: Fe3O4/CNTs can be made through chemical co-precipitation. Using the same surfactant and under the same experimental conditions, the carbon nanotubes’ surface coating is best and most homogeneous, when the content of the carbon nanotubes is 12.5%. When the content of carbon nanotubes is 12.5% and the experimental conditions are same, choosing CTAB as the surfactant, rather than SDS, finally get the better performance of sample. So the optimal parameters for the experiment are that the content of CNTs is 12.5%, and the choice of surfactant is CTAB. At this time, the surface of carbon nanotubes coats uniformly and the magnetic properties meet the requirements of tumor hyperthermia. In addition, as the carbon nanotubes contain varying degrees of nanocarbon particles, graphite fragments, amorphous carbon and other impurities, Therefore, in this paper, the carbon nanotubes are carbon nanotubes which have been purified with concentrated nitric acid.

Carbon nanotube modified Zn0.83Cd0.17S nanocomposite photocatalyst and its hydrogen production under visible-light

Visible light photocatalytic H2 production from water splitting has received much attention for its potential application in converting solar energy into chemical energy. In this paper, carbon nanotube modified Zn0.83Cd0.17S nanocomposite was prepared by a solvothermal method. CNTS can efficiently suppress the growth of chalcogenide nanoparticles and improve the dispersity of the nanocomposite. The absorption edges of Zn0.83Cd0.17S/CNTs nanocomposites red-shift and the response of the visible-light region (500–800 nm) is strengthened with the increase of CNTs contents in the samples. The prepared Zn0.83Cd0.17S/CNTs nanocomposites exhibit an enhanced photocatalytic H2-production activity and an optimum amount of CNT is determined to be ca. 0.25 wt%, at which the Zn0.83Cd0.17S/CNTs displays the highest photocatalytic activity under the irradiation of Xe lamp, with an H2 production rate of 5.41 mmol h−1 g−1. Furthermore, the prepared Zn0.83Cd0.17S/CNTs nanocomposite is photostable and no photocorrosion was observed after photocatalytic recycling, compared with pure Zn0.83Cd0.17S photocatalyst.

Transition and stability of copolymer adsorption morphologies on the surface of carbon nanotubes and implications on their dispersion.

In this study, the adsorption morphologies as well as stability and transitions of a commercial dispersant copolymer (BYK 9076) on the surface of multiwalled carbon nanotubes (MWCNTs) were studied using Fourier transform infrared and UV-vis spectroscopy, dynamic light scattering, and electron microscopy techniques. The results show that the dispersion of carbon nanotubes in ethanol does not increase continuously with increasing copolymer/CNT ratio, which is correlated with the adsorption morphologies of the copolymer on the CNT surface. At a ratio of copolymer/CNT below 0.5, the morphology is random, shifting to a hemimicelle structure at a ratio from 0.5 to 1.0 while at ratios above 1.0, a cylindrical pattern is seen. The hemimicelle morphology is able to prevent the agglomeration of CNTs when the CNT concentration increases to 8.7 mg/mL, while cylindrical morphology is more efficient and stable to provide dispersion of CNTs at higher concentrations of CNTs.

Discriminative Detection of Neurotoxins by a Layer-by-Layer Based Carbon Nanotube/bi-enzyme Biosensor

Multi-enzyme systems have attracted considerable interests due to the versatility for multiplexed detection of different analytes. In this study, a novel layer-by-layer (LbL) assembled multi-enzyme biosensor incorporating acetylcholinesterase (AChE) and organophosphate hydrolase (OPH) was proposed for discriminative detection between organophosphorus (OP) and non-organophosphorus (non-OP) neurotoxins. This was achieved through LbL assembly of electrostatically interacted enzyme armored carbon nanotubes (CNT-OPH and CNT-AChE) with a set of cushioning bilayers consisting of CNT-polyethyleneimine (PEI) and CNT-DNA on glassy carbon electrode with electrochemical detection. OPH catalyzes the hydrolysis of OPs (e.g. paraoxon) and AChE can be used for detection of both OPs and non-OPs (e.g. carbamate) through inhibition assays, and thus makes it possible for detection of OP neurotoxins from multi-analytes samples, and determination of the non-OP neurotoxins to their true concentration with AChE inhibition. Optimization of the LbL architecture was initially conducted with penetration analyses including position of active layer, number of total layers and impedance analyses with respect to different concentration of CNTs. Surface morphology and chemical analyses were characterized with Scanning Electron Microscopy and Raman spectroscopy to have a better understanding of the layered structure. The simple and inexpensive LbL approach can be further extended to a wide variety of enzymes in a multi-detection biosensing system, wherein each analyte could be “fingerprinted” with respect to its catalytic response to different enzymes.

Effects of carbon nanotubes on mechanical and 2D-3D microstructure properties of cement mortar

To study the influence of multi-wall carbon nanotubes (MWCNTs) on the mechanical and microstructural properties of cementitious composites, 0.00, 0.02, 0.08, 0.10, and 0.20 wt% of multi-wall carbon nanotubes were added into cement mortar, in which the cement-sand ratio was 1:1.5. The flexural and compressive strengths of cement mortar at the age of 3, 7, 28 and 90 d and the fracture performance at the age of 28 d were determined, its 2D micrograph was tested by means of SEM, and the 3D defects distribution was firstly determined with or without CNTs by means of XCT (X-ray computerized tomography). The results showed that 0.08 wt% of CNTs improved the compressive strength and flexural strength by 18% and 19%, respectively, and a significant improvement of its fracture property was observed. Moreover lower addition of carbon nanotubes to cement mortars can improve its microstructure and decrease the defects significantly compared to the cement mortar without CNTs. With the increase of the content of CNTs, the mechanical properties of cement mortars presented to be declined largely due to the agglomeration of CNTs.

Synthesis of polyaniline-coated carbon nanotubes and study on their pH-sensitive conductivity.

We report the synthesis of polyaniline-coated-carbon nanotubes (PANI-c-CNTs) composites by using water-soluble CNTs with phenyl sulfonate groups as templates. A series of characterizations including transmission electron microscopy (TEM), Fourier-Transform Infrared Spectroscopy (FTIR) and UV-vis spectroscopy were conducted to investigate the formation of PANI coating on the surfaces of the CNTs. The thickness of PANI coating in the PANI-c-CNTs composites was controlled by adjusting concentrations of aniline and CNTs. The conductivities of PANI-c-CNTs composites were measured by using conductive atomic force microscopy (c-AFM). It was found that the conductivities of PANI-c-CNTs composites were remarkably affected after doping and dedoping process of PANI coating by different pH solution. Therefore, our preliminary result indicates that as-prepared PANI-c-CNTs composites may be used as gas sensor such as HCl and NH3 vapor.

Multifunctional and specific interactions of CNTs in NBR and HNBR

There are different techniques in practice to disperse multiwalled carbon nanotubes (MWCNTs) in elastomers. In the present work, commercially available MWCNTs NANOCYL NC 7000™ are used as filler. A synthetic Nitrile Butadiene Rubber (NBR) and Hydrogenated Nitrile Butadiene Rubber (HNBR) were used as polymer matrix for the composites prepared by melt blending. The filler dispersion in HNBR was studied through Transmission Electron Microscopy (TEM). The mechanical properties are investigated through strain sweep and tensile tests. Dielectric measurements are carried out to study electrical conductivity of the nanocomposites. Dynamic mechanical measurements showed an enhanced Payne effect and improvement in stiffness with increase in CNTs content into rubber matrix An improvement in electrical and mechanical properties in both NBR and HNBR system resulted by an increase in filler loading. The mechanical and electric percolation threshold of CNTs was found at very low filler volume fraction. Equilibrium swelling experiments were used to study polymer-filler interaction with the help of Kraus plot and diffusion coefficient. NBR showed higher polymer-filler interaction compared to HNBR. In NBR nanocomposites, CNTs showed higher interaction than carbon black. Good dispersion and effective interaction of the CNTs with the polymer led to significant mechanical reinforcing effects.

The Structure and Electrical Conductivity of the CNTs/PMMA Nanocomposites Foams

Carbon nanofillers/polymer nanocomposites foam with electrical conductivity was a novel functional material. In this study, the CNTs/PMMA nanocomposites were prepared by the combination of ultrasonic dispersion and anti-solvent precipitation method. Then supercritical foaming method was untilized applied to prepare the foams. The morphology and the electrical conductivity of the foams were investigated. The conductivity of the nanocomposites showed a conductor behavior which was increased t from 1×10-6S/cm to 1×10-5S/cm with the CNTs content range from 1 wt.% to 2.5 wt.%. After foaming, the cell size of the foams was below 10 μm while the cell density increased 2~3 orders of magnitude compared with PMMA foams. The produced CNTs/PMMA nanocomposites foams exhibited a wide range electricity conductivity of the nanofiller contents. Key words: structure, electrical conductivity, CNTs, nanocomposites foams

An efficient antimony doped tin oxide and carbon nanotubes hybrid support of Pd catalyst for formic acid electrooxidation

We report on a mixture of antimony doped tin oxide (ATO) and carbon nanotubes as a novel support of Pd catalyst (Pd/ATO-CNTs) with the aims to enhance electron and proton conductivity of hybrid support, and catalytic activity and stability for formic acid electrooxidation. The surface content, morphology and structure of the as-prepared Pd/ATO-CNTs catalysts with different CNTs contents have been characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and high angle annular dark field STEM (HAADF-STEM), respectively. The electrocatalytic properties of the samples for formic acid electrooxidation reaction are investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that the activity and stability of Pd/ATO-CNTs catalyst is obviously higher than that of Pd/CNTs catalyst for formic acid electrooxidation due to unique physical and chemical properties of ATO and metal-support interaction between Pd nanoparticles and ATO. Moreover, the Pd/ATO-CNTs10 (CNTs content is 10 wt.% of ATO-CNTs support mass) with smaller Pd particle size and narrower size distribution on surface of the hybrid support exhibits the best performance for formic acid electrooxidation among all the samples.

ANALYSIS OF MICROWAVE ABSORBING PROPERTIES OF EPOXY MWCNT COMPOSITES

In the ongoing search for new materials for microwave absorption applications, Carbon Nanotubes deserve a special consideration due to their outstanding properties. In this paper, microwave absorbing properties of epoxy resin based composites containing commercial Multi Walled Carbon Nanotubes used as flllers have been analyzed. The complex permittivity of the composites was measured in a wide frequency band (3{18GHz). The absorbing properties of a single-layer absorber backed by a metallic plate considering several concentration of CNTs was simulated taking into account the measured permittivity.

Ferrite multiphase/carbon nanotube composites sintered by microwave sintering and spark plasma sintering

Ni-Carbon nanotube (CNT)-Ni0.5Zn0.5Fe2O4 multiphase composites were successfully prepared using microwave sintering (MWS) and spark plasma sintering (SPS) techniques. The obtained samples were characterized by scanning electron microscopy, electrical conductivity, and physical properties measurement system with vibrating sample magnetometer. The SPS prepared composites exhibited higher density, fine grain size, and to maintain favorable three-dimensional conductive network of CNTs compared with the microwave sintered (MWS) ones. Whether use MWS or SPS, both the density and the grain size are increasing with the CNT content increment. The increasing of density and grain size is the main contribution of the saturation magnetization increasing. In the composites of high content of CNTs (such as 5 wt %), the spinel structure of ferrite was totally destroyed, as indicated by a considerable decrease in the saturation magnetization. Interestingly, it is found that the Curie temperature increases with the increment of CNT content while the high saturation magnetization was maintained, which has implication that the multiphase ferrite composites will find application in a broad temperature range.

Sintering Behavior of CNT Reinforced Al6061 and Al2124 Nanocomposites

Ball milling and spark plasma sintering were successfully used to produce carbon nanotube reinforced Al6061 and Al2124 nanocomposites which have potential applications in the fields of aerospace, automotive, electronics, and high precision instrumentation. Al2124 and Al6061 nanocomposite powders containing 0.5 to 2 wt.% CNTs prepared through sonication and wet ball milling were spark plasma sintered at 400, 450, and 500°C for 20 minutes under a pressure of 35 MPa. CNTs were better dispersed, and less agglomerated and had good adhesion to the matrix in composites containing 1 wt.% CNTs. The increase of CNT content to 2 wt.% led to the formation of CNT clusters which resulted in less uniform and homogenous composite powders. Almost full densification of Al6061 reinforced with CNTs was achieved at 500°C. Also, CNTs reinforced Al2124 nanocomposites reached very high densities at 500°C. Composites reinforced with 1 wt.% CNTs displayed better densification compared to composites containing 2 wt.% CNTs. The increase of CNTs content from 0.5 to 1 wt.% increased the hardness of the Al6061 and Al2124 alloys to maximum values. Further increase of CNTs content to 2 wt.% decreased the hardness to values lower than that of the monolithic alloys.

Coupling {001} Facets Dominated Anatase TiO<sub>2</sub> Nanosheets with CNTs for Efficient Photocatalyst

High-reactive {001} facets dominated anatase TiO2 nanosheets were synthesized successfully by a simple hydrothermal method. CNTs were used to couple with as-prepared TiO2 nanosheets to further improve the photocatalytic activity of TiO2. Photocatalytic activities of the photocatalysts were tested by the degradation of Rhodamine B (RhB) aqueous solution under the xenon lamp irradiation. The results indicate that the introduction of CNTs will improve the photocatalytic activities of TiO2 which can be ascribed to the enhanced light absorption and separation efficiency of photogenerated holes and electrons. There was also an optimal content of CNTs to modify TiO2, and a possible mechanism for this idea was also proposed.

Novel Hybrids Derived from Poly(thiourea-amide)/Epoxy and Carbon Nanotubes

In the present work, nanocomposites of a matrix composed of poly(thiourea-amide) (an aramid)/epoxy (thermoset) and CNTs were fabricated. The hybrids were prepared by in situ polymerization using functionalized and nonfunctionalized CNTs. Amine-terminated poly(thiourea-amide)/epoxy/CNTs hybrids were cured at 120°C with different CNTs content. Chemical linking between amine terminated poly(thiourea-amide) and epoxide group of Bisphenol A diglycidyl ether (DGEBA) formed PTA/DGEBA complex. Hydrogen bonding of PTA with functionalized CNTs was expected to improve the hybrid characteristics. Tensile strength of functional hybrids ranged 57.36–60.68 MPa. 10% gravimetric loss (569–590°C) and Tg of PTA/DGEBA/functional CNTs (235–238°C) showed improvement over PTA/DGEBA/nonfunctional CNTs.

Enhanced performance of inverted organic photovoltaic cells using CNTs–TiOX nanocomposites as electron injection layer

In this study, we fabricated inverted organic photovoltaic cells with the structure ITO/carbon nanotubes (CNTs)–TiOX/P3HT:PCBM/MoO3/Al by spin casting CNTs–TiOX nanocomposite (CNTs–TiOX) as the electron injection layer onto ITO/glass substrates. The power conversion efficiency (PCE) of the 0.1 wt% single-walled nanotubes (SWNTs)–TiOX nanocomposite device was almost doubled compared with the TiOX device, but with increasing concentration of the incorporated SWNTs in the TiOX film, the performance of the devices appeared to decrease rapidly. Devices with multi-walled NTs in the TiOX film have a similar trend. This phenomenon mainly depends on the inherent physical and chemical characteristics of CNTs such as their high surface area, their electron-accepting properties and their excellent carrier mobility. However, with increasing concentration of CNTs, CNTs–TiOX current leakage pathways emerged and also a recombination of charges at the interfaces. In addition, there was a significant discovery. The incorporated CNTs were highly conducive to enhancing the degree of crystallinity and the ordered arrangement of the P3HT in the active layers, due to the intermolecular π–π stacking interactions between CNTs and P3HT.

Carbon nanotube wires for high-temperature performance

We developed carbon nanotube wires (CNWs) and monitored in situ their electrical properties at high temperature conditions for the first time. The dominant type of CNTs present in the material and packing density of thereof proved to have a dominant effect on the thermal stability of CNWs. Furthermore, we showed that kinetics of CNW oxidation plays an important role and slow heating rates or prolonged heating times are essential for the proper determination of thermal stability of CNTs. To enhance the stability at high temperatures, we applied SiC coating onto the CNWs, what allowed a 300°C improvement to the operational window, eventually reaching 700°C in the long-haul. Correlation of the change in electrical properties with thermogravimetric response showed that the loss of electrical percolation takes place at 100°C lower temperature than the last observed weight loss in CNTs content. Finally, we demonstrated feasibility of SiC-coated CNWs under high temperature conditions, by creating a heating device out of them. The presence of SiC layer gave rise to a significant improvement to the thermal stability of the CNT heaters, which now offer unprecedented range of operation reaching 700°C, as compared to 400°C when uncoated.

Mechanical properties and bioactivity of high-performance poly(etheretherketone)/carbon nanotubes/bioactive glass biomaterials

Poly(etheretherketone) (PEEK) is a rigid semicrystalline polymer that exhibits excellent mechanical properties and bone-like stiffness and is widely used in biomaterials. However, the development of PEEK-based bioinert materials has been impeded because PEEK lacks bioactivity. In this study, a series of PEEK/carbon nanotubes (CNTs)/bioactive glass (BG) ternary nanocomposites were produced using injection molding. BG was added to the composites in order to improve the bioactivity of the PEEK, and a novel method of adsorption and co-precipitation was used to add the CNTs to the composites in order to compensate for the deterioration in the mechanical properties of the PEEK caused by the addition of the BG. The microstructures of the composites were investigated using scanning electron microscopy (SEM), and the SEM images revealed that this method permits the uniform dispersion of the CNTs throughout the PEEK matrix. Further, the mechanical properties of the composites were significantly enhanced by the addition of the CNTs. The highest content of CNTs in the composites was 6 wt%. The composites containing 6 wt% CNTs and 4 wt% BG exhibited the same mechanical strength as the pure PEEK. The bioactivity of the PEEK when immersed in simulated body fluid (SBF) was improved by incorporating BG into the composites. These new ternary composite materials which exhibit satisfactory mechanical properties and a high degree of bioactivity have great potential to meet the demand for bone-substitute materials.

Zirconia-based nanocomposite toughened by functionalized multi-wall carbon nanotubes

In the present work, we have reported a novel approach to fabricate 3Y-TZP/carbon nanotube (CNTs) nanocomposites with improved fracture toughness using spark plasma sintering technology through the incorporation of functionalized multi-walled carbon nanotubes. For this approach, homogeneous distribution of CNTs in ceramic matrix has been achieved up to 4wt% CNTs content, revealed by SEM observations of both composite powders and fracture surfaces of sintered specimens. In addition, Raman spectroscopic indicates that CNTs can be retained at high sintering temperatures from 1250 to 1400°C. A clear improvement in the fracture toughness was achieved after adding CNTs, and the specimen with 4wt% CNTs sintered at 1300°C exhibited the best indentation toughness of 6.24MPam1/2, increasing 31% over monolithic ZrO2 sintered at the same temperature. Furthermore, the fracture mode transition and the activated toughening mechanisms during crack propagation were taken into account to explain the improvement in fracture toughness.