Small Amount Of Carbon Nanotubes Research Articles

Carbon nanotube-induced chirality in an achiral liquid crystal

A small quantity of carbon nanotubes was dispersed in an achiral liquid crystal (LC), and the mixture was found to exhibit a weak degree of chirality. The induced chirality in the LC was probed by means of the electroclinic effect in the LC’s smectic-A phase, which showed significant pretransitional behavior on approaching the smectic-A–smectic-C transition temperature from above. The results suggest that there is a net chirality associated with the carbon nanotubes, which is transmitted into the LC.

Multi‐scale hybrid composites‐based carbon nanotubes

AbstractSince the carbon nanotubes (CNTs) have been discovered, there has been a marked increase in the scientific literature dealing with multi‐scale composites. The multi‐scale hybrid composites with CNTs could endow the composites with some superior mechanical properties, such as improving the tensile performance, modest increasing compressive and flexural properties, and significantly enhancing interlaminar, interfacial and fracture strength. In addition, composites with CNTs can also develop the functional properties. A small quantity of CNTs can significantly increase the electrical properties of composites and lower the coefficient of thermal expansion of composites. The purpose of this work is to review the available literature in mechanical and functional properties of multi‐scale hybrid composites manufactured using CNTs. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers

Sinter and hot isostatic pressing (HIP) of multi-wall carbon nanotubes (MWCNTs) reinforced ZTA nanocomposite: Microstructure and fracture toughness

Abstract This work describes the microstructure and fracture toughness of zirconia toughened alumina (ZTA) nanocomposite in which multi-wall carbon nanotubes (MWCNTs) and nanosized ZrO 2 particles were used as reinforcement. The ZTA nanocomposites with additions of 0, 0.005, and 0.01 wt.% MWCNTs and 2 wt.% nanosized ZrO 2 particles were pressureless sintered in an anti-oxidant sagger with graphite powder bed at 1520 °C during 1 h in air and then HIPed at 1475 °C in argon atmosphere 1 h at a pressure of 150 MPa. Relative densities ranging 94–98% were reached. In HIPed composites the hardness and fracture toughness values were increased up to ∼17% and ∼37%, respectively, compared to the “as sintered” composites free of carbon nanotubes. A combined fracture mode, crack deflection, pull-outs of a small amount of carbon nanotubes, and bridging effect were the mechanisms leading to the improvement in fracture toughness.

Preparation, properties and application of polyamide/carbon nanotube nanocomposites

The discovery of carbon nanotubes (CNTs) has opened up exciting opportunities for the development of novel materials with desirable properties. The superior mechanical properties and excellent electrical conductivity make CNTs a good filler material for composite reinforcement. However, the dispersal of CNTs in a polymer solution or melt is difficult due to their tendency to agglomerate. Many attempts have been made to fully utilize CNTs for the reinforcement of polymeric media. Therefore, different types of polymer/CNTs nanocomposites have been synthesized and investigated. This paper reviews the current progress in the preparation, properties and application of polyamide/CNTs (nylon/CNTs) nanocomposites. The effectiveness of different processing methods has increased the dispersive properties of CNTs and the amelioration of their poor interfacial bonding. Moreover, the mechanical properties are significantly enhanced even with a small amount of CNTs. This paper also discusses how reinforcement with CNTs improves the electrical thermal and optical properties of nylon/CNTs nanocomposites.

Magnetic Investigation of Carbon Coated Co-, Ni- and Fe-Nanoparticles

Carbon coated cobalt-, nickeland iron-nanoparticles were prepared by chemical method and their structural and magnetic properties were investigated. The samples were synthesized by carburization of the nanocrystalline form of the appropriate metal in CH4, followed up by the reduction of the obtained carbon deposits. The X-ray diffraction and transmission electron microscopy study revealed carbon coated Co-, Niand Fe-nanocapsules of the mean size ca. 50 nm, and a small amount of carbon nanotubes. The measurements of magnetization and AC susceptibility were carried out for samples with different carbon content. A special attention was paid to the low temperature magnetic behavior. Decrease in the saturation moment at T = 4.2 K due to the nanosize of the particles was stronger for the samples with higher carbon content, while the coercivity field (610 Oe, 330 Oe and 390 Oe, for Co-, Ni-, and Fe-particles, respectively) was independent of carbon content. From the temperature dependence of AC and DC susceptibility a wide size distribution of the particles and blocking temperature above room temperature could be expected.

Coupled carbon nanotube network and acoustic emission monitoring for sensing of damage development in composites

Material and structural reliability is crucial for the potential use of composite materials in a variety of structural applications. As a result, damage detection and health monitoring of fiber-reinforced composites are attracting progressively more attention in the field of materials research. In this work, small amounts of carbon nanotubes are added into traditional fiber composites to form electrically conductive networks throughout the polymer matrix. The electrical response of the carbon nanotube network to accumulated damage combined with the acoustic emission (AE) technique is utilized to sense damage initiation and evolution in laminated composites. The parameters which correspond to the resistance change of the specimen due to damage in quasi-static and cyclic tests are used to evaluate the damage state in the material. There exists a bi-linear relationship between the resistance change and AE signal cumulative counts which gives insight toward the damage state of the material during quasi-static and cyclic tests.

Effect of modified carbon nanotube on physical properties of thermotropic liquid crystal polyester nanocomposites

Polymer nanocomposites based on a very small quantity of carbon nanotube (CNT) and thermotropic liquid crystal polymer (TLCP) were prepared by simple melt blending using a twin-screw extruder. Morphological observations revealed that modified CNT was uniformly dispersed in the TLCP matrix and increased interfacial adhesion between the nanotubes and the polymer matrix. The enhancement of the storage and loss moduli of the TLCP nanocomposites with the introduction of CNT was more pronounced at low frequency region, and non-terminal behavior observed in the TLCP nanocomposites resulted from the nanotube–nanotube and polymer–nanotubes interactions. There is significant dependence of the mechanical, rheological, and thermal properties of the TLCP nanocomposites on the uniform dispersion of CNT and the interfacial adhesion between CNT and TLCP matrix, and their synergistic effect was more effective at low CNT content than at high CNT content. The key to improve the overall properties of the TLCP nanocomposites depends on the optimization of the unique geometry and dispersion state of CNT and the interfacial interactions in the TLCP nanocomposites during melt processing. This study demonstrate that a very small quantity of CNT substantially improved thermal stability and mechanical properties of the TLCP nanocomposites, providing a design guide of CNT-filled TLCP composites with as great potential for industrial use.

Mechanical reinforcement and crystallization behavior of poly(ethylene 2,6-naphthalate) nanocomposites induced by modified carbon nanotube

Poly(ethylene 2,6-naphthalate) (PEN) nanocomposites reinforced with a very small quantity of carbon nanotube (CNT) were prepared by melt compounding using a twin-screw extruder. Morphological observations revealed that the modified CNT was uniformly dispersed in the PEN matrix and increased interfacial adhesion between the nanotubes and the polymer matrix, as compared to the untreated CNT. Furthermore, a very small quantity of the modified CNT can improve the mechanical and thermal properties of the PEN nanocomposites. This study also demonstrates that the non-isothermal crystallization behaviors of the PEN nanocomposites are strongly dependent on the presence of the modified CNT and cooling rate. The variations of the nucleation activity and activation energy for crystallization reflected the enhancement of crystallization of the PEN nanocomposites induced by the modified CNT. Combined Avrami and Ozawa analysis was found to be effective in describing the non-isothermal crystallization of the PEN nanocomposites in the presence of the modified CNT.

Carbon Nanotube Triggered Self‐Assembly of Oligo(p‐phenylene vinylene)s to Stable Hybrid π‐Gels

Gel self-assembly: Addition of small amounts of carbon nanotubes (CNTs) to a solution of oligo(p-phenylene vinylene) OPV1 in toluene triggers their self-assembly to form a composite gel (see picture) with higher stability and better rheological properties than the OPV1 gel. Strong physical interactions between the species allow the encapsulation of CNTs into self-assembled tapes of OPV1, reinforcing the 3D gel network.

The electrical properties of polymer nanocomposites with carbon nanotube fillers

The electrical properties of polymer nanocomposites containing a small amount of carbonnanotube (CNT) are remarkably superior to those of conventional electronic composites.Based on three-dimensional (3D) statistical percolation and 3D resistor network modeling,the electrical properties of CNT nanocomposites, at and after percolation, were successfullypredicted in this work. The numerical analysis was also extended to investigate the effectsof the aspect ratio, the electrical conductivity, the aggregation and the shape of CNTs onthe electrical properties of the nanocomposites. A simple empirical model was alsoestablished based on present numerical simulations to predict the electrical conductivity inseveral electronic composites with various fillers. This investigation further highlightedthe importance of theoretical and numerical analyses in the exploration of basicphysical phenomena, such as percolation and conductivity in novel nanocomposites.

A Study on the Thermal Properties of CNT reinforced Semiconductive Shield Materials Used in Power Cables

Use of the carbon nanotube is superior to general powder state materials of mechanical and electrical properties. Because its ratio of diameter and length (aspect ratio) is very large, it has been known as a type of ideal nano-reinforcement material. Based on this advantage, the existing carbon black of semiconductive shield materials used in power cables can acquire excellent properties by using a small amount of carbon nanotubes. Thus, we investigated the thermal properties of the carbon nanotube, such as thermal conductivity, specific heat, and DSC (Differential Scanning Calorimetry). We found that a high thermal resistance level is demonstrated by using a small amount of carbon nanotubes. As a result, this tendency confirms high cross-linking density in a new network in which the carbon nanotube between carbon black constitute molecules shows a bond by similar constructive properties.

Mechanical Properties of Carbon Nanotubes Reinforced Ultra High Molecular Weight Polyethylene

Carbon nanotubes (CNT) have been shown to enhance the engineering properties of plastic fibers in ballistic-resistant garments enabling the garments to withstand very high impact forces while remaining to be lightweight. Previous study shows that by reinforcing ultra high molecular weight polyethylene (UHMWPE) fibers with a small amount of carbon nanotubes, the fibers are simultaneously toughened and strengthened. In this paper, we study the mechanical properties of carbon nanotube reinforced ultra high molecular weight polyethylene (UHMWPE) by using micromechanics-based Mori-Tanaka model. Results show that the addition of small amount of carbon nanotubes as reinforcement can substantially improve the mechanical properties of the UHMWPE fibers.

Mechanical properties of triple composites of polycarbonate, single-walled carbon nanotubes and carbon fibres

The present work was undertaken to study the mechanical properties of reinforced polycarbonate systems, where the filler material consists of single-walled carbon nanotubes (SWCNTs), of carbon fibres (CF) or of both. The SWCNTs were taken from different sources, laser ablation and arc discharge, and carefully characterized before their incorporation into the matrix system. The loadings of the reinforcement material were varied from 1 to 35.5 wt% in the thermoplastic polymer. All composites were produced by melt extrusion. Experimental results show that small amounts of carbon nanotubes randomly distributed in thermoplastic matrix systems do not inevitably enhance the mechanical stability. Higher mechanical improvements could be attained by adding CF to the composite system. A triple composite of polycarbonate, PC/SWCNTs/CF reveals synergy effects in mechanical and electrical aspects. The composites were investigated by stress–strain measurements, dynamical mechanical analysis and hardness probing.

Towards cost-efficient EMI shielding materials using carbon nanostructure-basednanocomposites

Using a combination of dispersing low-cost carbon nanofibers and a small quantity ofcarbon nanotubes within the polystyrene matrix, we have demonstrated the formation of anovel nanocomposite with superior microstructure and improved electromagneticinterference (EMI) shielding characteristic. This nanocomposite is very promising for use asan effective and practical EMI shielding material owing to its high shielding effectiveness,light weight, low cost, and easy processability.

Gas sensing behavior of nano-structured polypyrrole prepared by “carbon nanotubes seeding” approach

Gas-sensing behaviors to chemical vapors of both the polypyrrole and the nano-structured polypyrrole composite film prepared by adding a small amount of carbon nano-tubes (CNTs) to act as nano-fiber seeds were investigated. The experimental results showed that although the gas-sensitivity of the film to trimethylamine was decreased to a certain extent by adding CNTs to form the nano-structure, the resistance of the film to moisture was improved greatly while the rapid response was remained. Moreover, SEM and XRD indicated that the orientation degree of the polypyrrole composite film was improved significantly by the CNTs.

Properties of anionic polymerized ε‐caprolactam in the presence of carbon nanotubes

AbstractThe results of the investigations of the relations between structure, physical and usage properties of polyamide 6 (PA6) reinforced with multiwall carbon nanotubes (MWNTs) are presented. A method of in situ anionic bulk polymerization of ε‐caprolactam in the presence of MWNTs was used for the preparation of reinforced PA6. The polymerization product was crushed, and the pellets of PA6 and PA6/MWNTs composites were injection molded to produce the standard test specimens for various measurements. The surface morphology (SEM), thermal (DSC, TGA, DMTA), and mechanical properties (tensile strength, Charpy's notched impact strength) of these materials were examined. Some differences between our specimens and those obtained by hydrolytic polymerization of ε‐caprolactam (CL) were found. It was found that a small amount of carbon nanotube decreases the crystallinity degree of PA6 matrix in the composites. The thermal stability was higher than that for neat PA6. DMTA results showed that the magnitudes of the storage modulus are higher for the PA6/MWNTs composites than for the unmodified PA6 in the temperature range between −90 and 200°C. The tensile strength and tensile modulus are higher compared with the neat PA6. The elongation at break showed no noticeable change in the range of MWNTs loading considered, while the Charpy's notched impact strength slightly decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Preparation of Biodegradable Nanocomposites by Incorporation of Functionalized Carbon Nanotubes

Polymeric carbon nanotube composites constitute one of the most promising alternatives to conventional filled polymers. The dispersion of nanometer-sized carbon nanotubes in a polymer matrix markedly improves its physical properties. This approach can also be applied to biodegradable synthetic aliphatic polyesters such as poly(L-lactic acid) (PLLA), which has been receiving an increasing amount of attention due to environmental concerns. In this study, the mechanical properties of PLLA were enhanced by the incorporation of a small amount of carbon nanotubes (0.8 wt%) in the solution state, which could make this material a good competitor for commodity materials such as general purpose plastics, while allowing it to retain its biodegradability. In order to obtain a homogeneous dispersion of the carbon nanotubes in the matrix, oxygen-containing groups were introduced on the surface of the MWNTs. The good dispersion of the nanotubes in the PLLA matrix observed by scanning electron microscopy was attributed to the fact that the PLLA was compatible with the functionalized MWNTs during the compounding process. The electrical conductivity of the composites was also investigated.

Morphological manipulation of carbon nanotube/polycarbonate/polyethylene composites by dynamic injection packing molding

Multiwalled carbon nanotubes (CNTs) filled polymer composite based on polycarbonate (PC) and polyethylene (PE) was fabricated by shear controlled orientation in injection molding (dynamic samples) and conventional injection molding (static samples). The morphological observation by scanning electronic microscope (SEM) indicated that PC phase in situ generated more and finer microfibrils in the dynamic samples than in the static ones, and the CNTs predominantly localized in the PC microfibrils without obvious migration to PE matrix and also aligned along the microfibrils. With such unique morphology, the tensile properties of the dynamic samples were simultaneously considerably increased compared to their complementary samples, especially in the presence of 0.5wt% of CNTs, which indicates both stretch alignment of CNTs and molecule orientation can bring out a significant reinforcement on PE. Furthermore, the static samples displayed double yielding points in on the stress–strain curves, and interestingly, a small quantity of CNTs in PC fibrils strengthened this phenomenon.

Preparation of Nano‐Structured Polyaniline Composite Film via “Carbon Nanotubes Seeding” Approach and its Gas‐Response Studies

AbstractSummary: Polyaniline composite film with nano‐structure was prepared through a chemical oxidation method by adding carbon nanotubes (CNTs) as nano‐fiber seeds. Spin‐coating or casting method was employed on the interdigital electrodes of carbon and the composite film was formed with an in‐situ polymerization approach. The gas‐response to trimethylamine was also examined at room temperature. It was found that the difference was not only in the morphology, but also in the value of gas‐sensitivity. Comparing with films without the CNTs, the value of gas‐sensitivity decreased dramatically, while the baseline current of the sensor increased remarkably. This method can be an effective way to adjust the gas‐sensitivity of sensors made from polyaniline composite film by adding a small amount of carbon nanotube. XRD data showed that the degree of orientation of polyaniline was increased greatly with the addition of CNTs.Morphology and reproducibility (inset) of polyaniline composite film containing carbon nanotubes.magnified imageMorphology and reproducibility (inset) of polyaniline composite film containing carbon nanotubes.

Electrooptical Responses of Carbon Nanotube-Doped Liquid Crystal Devices

The electrooptical characteristics of carbon nanotube-doped liquid crystal (LC) devices were investigated. Two complementary operation modes of the liquid crystal cells were fabricated. The measured results reveal that anisotropic carbon nanosolids modify the dielectric anisotropy and the viscosity of the liquid crystal carbon nanotube mixture, hence significantly modifying the threshold voltage and the switching behavior of a liquid crystal device. Doping a small amount of carbon nanotubes into the liquid crystal mixture is effective in improving the electrooptical characteristics of an LC device when the employed LC mixture is viscous.