Conductivity Of Carbon Nanotube Composites Research Articles

Modern Fiber Art Creation Based on Traditional Hakka Hand Tie-Dyeing Process Based on Carbon Nanotube Nanomaterials

With the change of the times, modern fiber art has greatly changed and developed in the traditional technology. This artistic expression brings people richness in form and artistic language and is a kind of performance art between art and decoration. Modern fiber art is a part of life. With the change of living environment, people's things will also change, so if we want to adapt, we have to change appropriately. Molecular dynamics and calculation of resistance values are used to study the relationship between the length, cross section, and temperature of materials in carbon nanotube composites. Modern fibers are mainly made of composite materials such as carbon nanotubes. This paper mainly uses the repeated expansion of polymer carbon nanotube materials, uses the interaction between electrons and phonons as well as the interaction between phonons and phonons to test the thermal conductivity value and the curing regime of different composite materials at different stages, and in order to study the thermal conductivity of carbon nanotube composites, the relevant data in the model are set to a unified packing density system and melting point, uses the temperature of 280 K and 320 K to normalize the composite materials, and explores the change law of the heat flow correlation function and the thermal conductivity. It can be seen from the experimental data that the heat flow correlation function changes with time and gradually becomes stable and finally fluctuates around 0, which means that the model is in a stable state and the scheme is feasible. With the development of the times, fiber art has various forms of expression, and this art is expected to shine in all walks of life.

Effect of High-Gradient Magnetic Field on Electrical Property of Carbon Nanotube-Polypyrrole Composite; Nanotube Separation Mechanism

High- and low-gradient magnetic fields are produced by resistor-inductor-capacitor (RLC) discharge apparatuses. The maximum magnetic field is 12.5 Tesla with 1-ms pulse duration. Multiwall carbon nanotube–polypyrrole composite is prepared. The samples are exposed to high- and low-gradient magnetic fields. To understand the behavior of carbon nanotubes (CNTs) in high-gradient magnetic fields (HGMFs), we theoretically calculated the equivalent magnetic susceptibility of a CNT in the gradient magnetic field. We found that the gradient force which is exerted on a CNT could be repellent or absorbent depending on the parallel and perpendicular susceptibilities of the CNT, as well as on the initial orientation of the CNT with respect to magnetic field direction. Four-probe studies show that the electrical conductivity of CNT composites decreases after exposure to a high-gradient magnetic field. Microscopic observation of the electrical current profile of composites reveals rearrangement of CNTs under HGMF.

Polymer Composite Containing Carbon Nanotubes and their Applications.

Carbon nanotubes (CNTs) are attractive nanostructures in this regard, primarily due to their high aspect ratio coupled with high thermal and electrical conductivities. Consequently, CNT polymer composites have been extensively investigated for various applications, owing to their light weight and processibility. However, there have been several issues affecting the utilization of CNTs, such as aggregation (bundling) which leads to a non-uniform dispersion and poor interfacial bonding of the CNTs with the polymer, resulting in variation in composite performance, along with the additional issue of high cost of CNTs. In this article, recent research and patents for polymer composites containing carbon nanomaterial are presented and summarized. In addition, a rationale for optimally designed carbon nanotube polymer composites and their applications are suggested. Above the electrical percolation threshold, a transition from insulator to conductor occurs. The percolation threshold values of CNT composite are dependent on filler shape, intrinsic properties of filler, type of polymer, CNT dispersion condition and so on. Different values of percolation threshold CNT polymer composites have been summarized. The difference in percolation threshold and conductivity of CNT composites could be explained by the degree of effective interactions between nanotubes and polymer matrix. The reaction between surface functional groups of CNTs and polymer could contribute to better dispersion of CNTs in polymer matrix. Consequently, it increased the number of electrical networks of CNTs in polymer, resulting in an enhancement of composite conductivity. In addition, to exfoliate nanotubes from heavy bundles, ultrasonication with proper solvent and three roll milling processes were used. Potential reactions of covalent bonding between functionalized CNTs and polymer were suggested based on the above rationale. Through the use of CNT functionalization, high aspect ratio CNTs, and proper fabrication, uniform dispersion of nanotubes in polymer can be achieved leading to considerable improvement in electrical conductivity and electromagnetic interference (EMI) shielding properties.

The role of agglomeration in the conductivity of carbon nanotube composites near percolation

A detailed study of agglomeration in composite materials containing carbon nanotubes (CNT) is presented. Three dimensional samples with different degrees of agglomeration were created in three different ways, leading to a wider range of geometries available to study. Virtual charges are injected into the computer-generated samples and move through these samples according to a Monte Carlo hopping algorithm. Results show that there is an optimal level of agglomeration that is actually beneficial for charge transport at low volume concentrations, lowering the percolation threshold. It is found that near percolation, a more uniform CNT distribution (less agglomeration) leads to more conductive paths, but with a lower mobility. The optimum level of agglomeration comes from a trade off between these two properties. Beyond this optimum agglomeration state, it is observed that conductivity tends to decrease as dispersion increases at all concentrations studied here. At high concentration (percolated samples), where CNT clumps merge, conductivity seems to be less sensitive to agglomeration.

Effect of the Carbon Nanotube Distribution on the Thermal Conductivity of Composite Materials

Finite element analysis has been employed to investigate the effect of carbon nanotubes (CNTs) distribution on the thermal conductivity of composite materials. Several kinds of representative volume elements (RVEs) employed in this study are made by assuming that unidirectional CNTs are randomly distributed in a polymer matrix. It is also assumed that each set of RVEs contains a constant fiber volume fraction and aspect ratio. Results show that randomness—the way in which fibers are distributed inside the matrix—has a significant effect on the thermal conductivity of CNT composites. Results of this study were compared using the analytical Xue and Nan model and good agreement was observed.

Interaction models for effective thermal and electric conductivities of carbon nanotube composites

The present article provides supplementary information of previous works of analytic models for predicting conductivity enhancements of carbon nanotube composites. The models, though fairly simple, are able to take account of the effects of conductivity anisotropy, non-straightness, and aspect ratio of the CNT additives on the conductivity enhancement of the composite and to give predictions agreeing well with existing experimental data. The omitted detailed derivation of this model is demonstrated in the present article with a more systematical analysis, which may help with further development in this direction. Furthermore, the effects of various orientation distributions of CNTs are reported here for the first time. The information may be useful in design or fabrication technology of CNT composites for better or specified conductivities.

Dispersion and thermal conductivity of carbon nanotube composites

A mechanical method was used to shorten carbon nanotubes (CNTs) for improving dispersion without reducing their thermal conductivity. Single walled carbon nanotubes (SWCNTs) were mechanically cut to produce short and open-ended fullerene pipes. These shortened SWCNTs were then used in polymer composites. Both atomic force microscopy and scanning electron microscopy characterizations suggested that nanotube shortening significantly improved CNT dispersion. Thermal conductivity of composites containing short CNTs were found to be much better than those containing pristine CNTs.

An analytical model of effective electrical conductivity of carbon nanotube composites

Experiments on electrical properties of carbon nanotube (CNT) composites have shown that addition of CNTs may greatly enhance the electrical conductivity of the matrix. It has been a key but unresolved issue for years how to develop an analytical model of effective electrical conductivity of CNT composites that takes account of not only the CNT concentration and percolation, but also CNT conductivity anisotropy, aspect ratio, and nonstraightness. Such a model is established in this letter. The model predictions agree well with the measured data available in literatures and are also extended to account the effect of the orientation distribution of CNTs.

Effects of anisotropy, aspect ratio, and nonstraightness of carbon nanotubes on thermal conductivity of carbon nanotube composites

Simple models for the thermal conductivity enhancements in carbon nanotube (CNT) composites are presented as analytical functions of volume fraction, anisotropic thermal conductivities, aspect ratio, nonstraightness, and interfacial thermal resistance of the CNTs. The model predictions agree very well with the measured thermal conductivities of CNT composites available in the literature. It is shown that using CNTs with higher aspect and straightness ratios is an efficient means to get much better thermal conductivity enhancements for CNT composites. The models are further extended to account the effects of either the random or aligned orientation of CNTs and the interaction among CNTs on thermal conductivity of CNT composites.

Effective thermal and electrical conductivity of carbon nanotube composites

We generalize Bruggeman effective medium theory to investigate the effective electrical and thermal conductivity of carbon nanotube composites. Both the nonlinear dependence of effective thermal conductivity on the nanotube volume fraction in nanofluids and very low percolation threshold for carbon nanotube/polyimide composites are well predicted. Numerical results show that although single-walled carbon nanotubes possess a higher thermal conductivity than multi-walled nanotubes, they induce less effective conductivity due to interfacial resistance. Moreover, the non-spherical shape of carbon nanotubes helps to achieve a large enhancement of the effective conductivity, and the use of disc-shaped particles gives a larger conductivity than the use of needle-shaped particles.

Effect of interface on the thermal conductivity of carbon nanotube composites

This paper presents the effect of interface on the equivalent thermal conductivity of the carbon nanotube composites. The element free Galerkin method has been utilized as a numerical tool to evaluate the thermal conductivity of the composites. The numerical results have been obtained using continuum mechanics approach for a model composite problem, and it was found that the interface has a major effect on the thermal conductivity of the composites. The effect of interface on the effective conductivity of the composite is small for short nanotubes as compared to long nanotubes. Interface thickness also plays an important role on the effective thermal conductivity of the composite. Nanotube anisotropy has got a small effect on effective thermal conductivity of the composites. Transverse thermal conductivity of the composite has got nearly linear variation with nanotube length.

Modeling of interfacial modification effects on thermal conductivity of carbon nanotube composites

The effect of functionalization of carbon nanotubes on the thermal conductivity of nanocomposites has been studied using a multi-scale modeling approach. These results predict that grafting linear hydrocarbon chains to the surface of a single wall carbon nanotube with covalent chemical bonds should result in a significant increase in the thermal conductivity of these nanocomposites. This is due to the decrease in the interfacial thermal (Kapitza) resistance between the single wall carbon nanotube and the surrounding polymer matrix upon chemical functionalization. The nanocomposites studied here consist of single wall carbon nanotubes in a bulk poly(ethylene vinyl acetate) matrix. The nanotubes are functionalized by end-grafting linear hydrocarbon chains of varying length to the surface of the nanotube. The effect which this functionalization has on the interfacial thermal resistance is studied by molecular dynamics simulation. Interfacial thermal resistance values are calculated for a range of chemical grafting densities and with several chain lengths. These results are subsequently used in an analytical model to predict the resulting effect on the bulk thermal conductivity of the nanocomposite.

Model for the effective thermal conductivity of carbon nanotube composites

We present a novel model of the effective thermal conductivity for carbon nanotubecomposites by incorporating the interface thermal resistance with an average polarizationtheory. The dependence of the effective thermal conductivity on nanotube length, diameter,concentration, and interface thermal resistance has been taken care of simultaneously inour treatment. The model predicts that the large length of the carbon nanotubes embeddedplays a key role in the thermal conductivity enhancement, while the large interface thermalresistance across the nanotube–matrix interface causes a significant degradation.Interestingly, the model predicts that the nanotube diameter has a very smalleffect on the thermal conductivity enhancement of the nanotube composites.In addition, the model predicts that the thermal conductivity enhancement ofnanotube composites increases rapidly with decreasing the thermal conductivity ofthe matrix and increases with increasing the thermal conductivity of the carbonnanotube. Predictions from the novel model are in excellent agreement with theexperimentally observed values of the effective thermal conductivity of carbonnanotube nanofluids which the classical models have not been able to explain.

Effects of chemical modifications on the thermal conductivity of carbon nanotube composites

Interfaces and close proximity between carbon nanotubes (CNTs) and the matrix are very important for their thermal conductance of CNT composites. Chemical modifications to the CNTs are a possible approach to manage the interfacial interactions. In this study, the nanocomposites of the polydimethylsiloxanerubber with 2wt% chemical-treated CNTs loading were prepared to investigate the influence of chemical modifications and defects on the thermal conductivity of CNT composites. The CNTs treated in concentrated nitric acid showed remarkable changes which could be seen directly by their morphologies. The thermal conductivities κ of the composites were measured carefully in comparison with that by the raw CNT loading. The κ varied somewhat up and down with the treatment level. This study reveals that moderate chemical modifications are beneficial to improve the thermal conductivity of the CNT composites. However, their negative effects to the thermal conductance are more remarkable than the theoretical anticipation.