In this study, artificial neural network was used to predict the microhardness of Al2024-multiwall carbon nanotube(MWCNT) composite prepared by mechanical alloying. Accordingly, the operational condition, i.e., the amount of reinforcement, ball to powder weight ratio, compaction pressure, milling time, time and temperature of sintering, as well as vial speed were selected as independent input and the mean micro-hardness of composites was selected as model output. To train the model, a Multilayer perceptron neural network structure and feed-forward back propagation algorithm has been employed. After testing many different ANN architectures, an optimal structure of the model i.e. 7-25-1 was obtained. The predicted results, with a correlation relation between 0.982 and 0.9952 and 3.26% mean absolute error, show a very good agreement with the experimental values. Furthermore, the ANN model was subjected to a sensitivity analysis and the significant inputs affecting hardness of the samples were determined.
One-dimensional nanostructured metals play important roles as interconnects and nanoscale electronic devices. Silver nanowire is especially attractive due to its extre- mely high electric and thermal conductivities . Tem- plate-directed synthesis and the solution-phase based approach have been widely used to produce Ag nano- wires [2-4]. However, pure silver nanowires are limited for metallic interconnection applications as its resistivity increase largely with the dimension decreasing due to its increased electron scattering. On the other hand, carbon nanotubes [CNTs] are known for having long mean free path (order of several microns), extremely high current densities (> 10 9 A/cm 2 at 25°C), and high aspect ratio. The bulk composites made of metal matrix with CNTs as the reinforcement component for augmenting the metal conductivity have been extensively investigated [5-7]. However, how to fabricate and to characterize a single one-dimensional nano-composite with embedding a single CNT within the silver matrix are difficult [8,9], and electroless silver plating process has been used to deposit silver onto multiwalled carbon nanotube [MWCNT] . In this paper, one-dimensional Ag/ MWCNT nano-composite was prepared by coating the MWCNT with relatively uniform nano-crystalline silver layer using the electroless silver plating process. The
The main purpose of the present work is to investigate the free vibration of functionally graded carbon nanotube- reinforced composite (FG-CNTRC) cylindrical panels. The element-free kp-Ritz method based on the first-order shear deformation shell theory is employed to derive the discretized governing equations. The effective material properties of FG-CNTRC cylindrical panels are estimated through a micromechanical model based on the Eshelby- Mori-Tanaka approach. Convergence and comparison studies are provided to verify the stability and accuracy of the proposed method for free vibration analysis of FG- CNTRC cylindrical panels. The effects of boundary condition, CNT volume fraction and temperature change on characteristics of the frequency are also examined in detail.
Abstract— New technologies are required to improve desalination efficiency and increase water treatment capacities. One promising low energy technique to produce potable water from either sea or sewage water is Membrane Distillation (MD). However, to be competitive with other desalination processes, membranes need to be designed specifically for the MD process requirements. Here we report on the design of Carbon Nanotube (CNT) based composite material membranes for Direct Contact Membrane Distillation (DCMD). The membranes have been thoroughly characterized and also tested in a DCMD setup under different feed temperatures and test conditions. We demonstrate that Bucky-paper membranes can be used for purification of synthetic seawater via the DCMD process and, most importantly, that the composite Bucky-paper (BP) structures show improved lifetime and performance compared to their self-supporting BP counterparts.
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Abstract. A direct process for manufacturing polymer carbon nanotube (CNT) based composite yarns is reported. The new approach is based on a modified dry spinning method of CNT yarn and gives a high alignment of the CNT bundle structure in yarns. The aligned CNT structure was combined with a polymer resin and, after being stressed through the spinning process, the resin was cured and polymerized, with the CNT structure acting as reinforcement in the composite. Thus the present method obviates the need of special and complex treatments to align and disperse CNTs in a polymer matrix. The new process allows of producing the polymer/CNT composite with properties that may satisfy various engineering specifications. The structure of the yarn was investigated using scanning electron microscopy coupled with a focused ion beam system. The tensile behavior was characterized using a dynamic mechanical analyzer. Fourier transform infrared spectrometry was also used to chemically analyze the presence of polymer on the composites. The process allows development of polymer/CNT based composite with different mechanical properties suitable for a range of applications by using various resins.
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Human embryonic stem cells [hESCs] are able to differentiate into specific lineages corresponding to regulated spatial and temporal signals. This unique attribute holds great promise for regenerative medicine and cell-based therapy for many human diseases such as spinal cord injury [SCI] and multiple sclerosis [MS]. Carbon nanotubes [CNTs] have been successfully used to promote neuronal differentiation, and silk has been widely applied in tissue engineering. This study aims to build silk-CNT composite scaffolds for improved neuron differentiation efficiency from hESCs.
Nanoscopic particles of carbon nanotubes are tubular structures formed by carbon atoms. Diameter size between 1 and 50 nm for the normal duration of one micrometre up to a few centimetres. Therefore, the ratio of CNTs can be very large. Advantages of CNTs are available in commercial form multiwall or in the laboratory as a wall. Since their discovery, the physical characteristics unique has led to enormous interest. With a very large elastic modulus, carbon nanotubes known as a reinforcing agent effectively. Depending on their molecular structure, carbon nanotubes with small diameter show either semi-conducting or metallic behaviour.
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In order to see its usefulness of porosimetry-based method for CNT agglomerates, we utilized (1) various types of CNT, (2) different forms of CNT agglomerates, (3) CNT dispersions made in different solvents, and (4) different kinds of dispersion methods. These parameters are important to control pore sizes of CNT agglomerates. Firstly, various CNTs (Super Growth single-walled carbon nanotube (SG SWNT), HiPco SWNT, CoMoCAT SWNT, Bayern multi-walled carbon nanotube (MWNT), vapor grown carbon fiber (VGCF)) were dispersed in solvent by a high-pressure jet mill homogenizer. The resulting sus- pensions were filtered to obtain Buckypapers, then their pores were characterized. The pore sizes of these CNT agglomerates changed depending on the type of CNT (diameter, number of walls), by which we can classify diverse CNTs. Next, we investigated sparsely to densely packed forms of CNT agglomerates and found out that they are distinguishable by the different pore sizes. Furthermore, the correlation between CNT dispersibility in various solvents and pore sizes of CNT agglomerates was demonstrated. When dispersed in N , N -dimethylfor- mamide (DMF) known to disperse CNTs efficiently, the pore sizes of CNT agglomerates became smaller than those from the poor solvents.
In aviation, automobile and other structural applications, the demand for materials possessing superior properties like higher strength to weight ratio, high modulus and high temperature stability along with good damping ability is continuously increases. However, it is difficult to achieve all these properties in a single material. This is one of the driving force for the development of composite materials .
Theoretical and experimental density measurements were studied using the rule of mixture and using Archimedes principle . Fig 2 shows the density of the composites with varying weight percentage of reinforcements of 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5 wt % MWCNTs, decreases with increase in MWCNTs addition. This fact may be due to the displacement of atoms by the light weight carbon atom which usually occupies interstitial position of the aluminium crystal structure . Secondly, porosity which predominantly occurs in most of the sintered metallic compositions decreases the density even though dislocations take place, shown in Fig. 2. Initially, the density of sintered-heat treated samples increases by 4.48% and sintered-extruded samples by 5.23% compared to sintered composites. As the percentage addition of MWCNT increases, the density individually decreases by 2.3%, 3.8% and 4.04% in sintered, sintered-heat treated and sintered-extruded AA2024+0.5% MWCNT composites respectively.
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where f DS ′ = k DS ′ s ∞ and f DA ′ = k DA ′ a ∞ represent the diffusive fluxes of substrate and oxidized mediator in the solution adjacent to the nanotube film. We note from eqn.14 that the effects of concentration polarization will be important when the net reaction flux f S becomes close to the limit imposed by the diffusive transport of substrate through the solution given by f DS ′ = k DS ′ s ∞ . Under these circumstances the substrate concentration within the layer at x = L will differ appreciably from the value in the bulk solution and the enzyme will be less saturated than one would expect from the value of the bulk concentration. A similar consideration pertains for the oxidized mediator species concentration a L at
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MWCNT-G composite was prepared according to following procedure. Typically, 10 mg surface acidified MWCNT was firstly dispersed into 24 mL water using 2 h sonication. After a homogenous black solution was formed, 2 mg graphene powder was added into MWCNT dispersion followed with further 5 h intense sonication. Due to the π-π supramolecular interactions, MWCNT-G composite dispersion was formed [24, 31]. The morphology of as-synthesized composite was observed using a ZEISS, SUPRA 55 field emission scanning electron microscopy (FESEM) and a transmission electron microscopy (TEM, JEOL JEM-100CX). A Fourier transform infrared spectrometer (FT-IR, Thermo-Nicolet Nexus 670) was used to characterize the MWCNT-G composite.
than 0.7 dB at frequencies up to 40 GHz. We compared the insertion loss with that of an RF-MEMS switch with only Au–Au contacts, as shown in Fig. 10. As a result, we confirmed that the two devices exhibit similar inser- tion losses, although the insertion losses of the Au–Au/ CNT-composite contact RF-MEMS switch are slightly higher than that of the Au–Au contact switch. This differ- ence originates from the slightly higher resistivity of Au/ CNT-composite layer compared with that of the Au layer. Furthermore, the life cycle of the Au–Au/CNT-compos- ite contact switch was also evaluated. The life cycle test was performed by repeating the ON/OFF operations until the switch failed. The average number of cycles of the Au–Au/CNT-composite contact switch and Au–Au contact switch was ~ 9100 and ~ 3600 cycles, respectively.
Carbon nanotubes (CNTs) are a kind of two-dimensional carbon nanomaterial. They are widely used in analytical chemistry, physics and materials fields because of their excellent electrochemical properties, such as promoting electron transfer, reducing potential, and large specific surface area that especially conducive to the immobilization of organic compounds [14, 15]. Due to their excellent performance, CNTs have been used for electrochemical detection of hydrogen peroxide , hydrazine , amino acid , catechol  and other substances. Thus, it is believed the combination Ce-TiO 2 with CNTs could produce good electrocatalytic activity.
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to slower heterogeneous electron transfer for ferricyanide . In addition, there are other works demonstrating that an increase in the presence of oxygen-containing groups on MWCNTs  and graphite  actually slows the rate of heterogeneous electron transfer. It is also known that the relationship between the amount and position of the defects and oxygen-containing groups generated by the nitric acid treatment varies significantly according to the carbon nanotube structure . Though under these circumstances it is difficult to evaluate the exact reasons for such con- tradictory results, we believe that two important differences in our work might relate to the results that we obtained. Compared to other DWCNT work where electrocatalytic activity of DWCNT toward reduction of ferricyanide was examined , our work differs at two points. Besides the structure of working electrodes (composite/film), there are also some differences between oxidation procedures. We have just kept the particles at 80°C in nitric acid for 5 h, while they kept them at 80°C in nitric acid overnight. It is obvious that more damage occurs when longer period of heating procedure is applied. In addition, the contribution of GC l-particles has to be considered in our case.
Figure 4.12 illustrates application of this method. The measurements were taken for five different 5-ply yarns inside the 25-ply yarn composite. The dark areas are nanotube-epoxy yarn regions, while the bright outlines are pure epoxy resin areas which were charging in the SEM because of the lack of conductive nanotubes in them. This method was more accurate for determining the cross-sectional area of the plied yarns than the other two methods described above, because the actual shape and packing of single nanotube yarns can be easily viewed and quantified, rather than being arbitrarily assumed or determined by fitting to some geometrical model. As Figure 4.12 illustrates, single yarn cross sections in each of the 5-ply yarns are far from circular; each of them changes its shape to pack more tightly in the twisted plied yarn than cylinders would. The following cross-sectional areas were obtained from the cross section SEM pictures: 1,137 µm 2 for 5-ply yarn, 5,685 µm 2 for 25-ply yarn, and 39,212 µm 2 for 3-D braid. This technique of determining the cross section was adopted for the plied yarn and 3-D braid in the stress-strain plotting and strength evaluation.
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In conclusion, we have shown results on surface modification of SWNT-PVA film samples upon high power femtosecond laser ablation. The order of magnitude considerations in this paper could be refined considerably by a quantitative analysis of the electromagnetic field of laser radiation, the thermal field, and stress field configuration near high concentration and big bundles of CNT in the PVA matrix. However, because of the unordered arrangement of CNTs in the sample, such more refined calculations, although desirable, are not essential. The resulting conclusions may be drawn from our qualitative investigation: (1) The PVA-SDBS composite without SWNT does not undergo modifications at the highest available laser powers and energies. SWNTs feature high heat conductivity; therefore, the PVA-SDBS matrix hosting SWNTs shows surface alteration at quite low laser power and on a the short time scale. High concentration of CNTs and bundles of CNTs leads to local heat transfer from the laser beam to the polymer and results in slight alterations in the geometries of the formed craters. (2) The most important process of structural alteration observed is the elimination of water together with the PVA-SDBS matrix decomposition. (3) A PAH capping layer, formed by laser irradiation of the polymer host matrix, changes the composites saturable absorption properties, leading to the introduction of additional reflection and scattering on roughness and SWNT’s bundles of large diameters formed close to the surface. More importantly, it improves the overall thermal stability and helps to sustain a laser optical fluency of 2.3 mJ·cm −2 . The polymer samples with dispersed SWNTs demonstrate stabilisation of the resulted crater. We would like to stress, that the laser cavity configuration optimisation also plays a critical role in SA stability, as rapid alterations of the intracavity power and switching between mode-locking and Q-switched regimes causes irreversible damage to the sample, despite the power of the radiation.
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Abstract - The carbon nanotubes are well known for their superior material properties. They are effectively introducing in the composite to improve the material properties and therefore, it is necessary to understand the effect of carbon nanotubes on the mechanical properties of nanotube-based composite. In this paper, the effective Young’s modulus of the carbon nanotube-based composite is investigated by the finite element method for different matrix stiffness considering both long and short type carbon nanotubes. The effective Young’s modulus for different nanotube thickness in case of perfect bonding and interphase thickness for imperfect bonding is also determined. A 2-D axisymmetric model for the cylindrical representative volume element is considered in this work. For validation of the estimation considering the perfect bonding, finite element method results are compared with the analytical results. It is concluded that for both long and short type carbon nanotubes, the effective Young’s modulus of the composite material increases as the matrix stiffness, nanotube thickness, and interphase thickness increases. Keywords - Carbon nanotube, composite material, finite element method, Young’s modulus.
Besides lightweight, advantages of magnesium are good mechanical damping properties, good castability especially in die casting process and also plentiful of global supply. Despite of its advantages, magnesium when compared with aluminium, it has low strength and ductility, poor wear, creep and corrosion resistance (Tjong S. C., 2009). Thus to overcome this problem, magnesium reinforces with ceramic micro and nano particle. In general, MMC been reinforce with micro size reinforcement. Lately, there is extensive interest in the production of metal matrix nanocomposite in which nano particulates are incorporated in base matrix. When compared to composites with micron-sized reinforcements, nanocomposites exhibit comparable or better mechanical properties with the use of lesser amount of nanoparticulate reinforcements. Some nano reinforcement that's been used is nano size alumina particle and carbon nanotube (CNT). Alam M. E. et al, (2011) has found that the nanoparticulate alumina has increased the mechanical properties of magnesium alloy AZ31such as hardness, yield strength and ultimate tensile strength.
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Abstract — This project is based on the investigation of aluminium matrix reinforced with carbon nanotube particles. The investigation involves the analysis of wear resistance and the mechanical properties of the composite. The composite can be either ceramic matrix composite or metal matrix composite. This project is based on the metal matrix composite as we have decided to analyse the carbon nanotube reinforced aluminium. The aluminium 7075 alloy is selected because of its excellent resistance to fatigue, high strength and toughness. On the other hand, carbon nanotube particles offer excellent tensile strength and hardness to materials due to their nano structure and strength of the bonds between carbon atoms. The carbon nanotube particles are reinforced with aluminium 7075 by the stir casting process. The stir casting process is the most suitable way to reinforce because only then the carbon nanotube particles mix in correct proportions. Then the casted product is tested for wear resistance and the mechanical properties. The casting is done by adding appropriate proportion of carbon nanotube particles. Here, the 2wt% of carbon nanotube is used. For doing the wear test, a pin of 8mm diameter and 23 mm length of the casted portion is taken. The pin is then analysed for wear characteristics using pin-on-disc tribometer. The mechanical tests such as hardness tests, tensile tests and impact tests are performed on the casted product and the results are recorded. The traditionally used metals may not satisfy the vast engineering application. The metals cannot be used in all the applications considering the weight, strength and durability. In this regard, the composite materials can be replaced for the traditionally used metals. The composite material has good versatility properties which can be used in various applications. For each application, we can select the appropriate composite. Some of the properties of the composite materials include light weight, high strength etc. The results recorded in pin-on-disc tribometer test is used to draw graphs explaining the wear characteristics and the wear rate value for the composite is determined. The readings taken from material testing are used to find the strength of the material.