Preparation of carbon nanotubes composite sheet using electrophoretic deposition process

Abstract

Since the discovery by Ijima [1] in 1991, carbon nanotubes have attracted tremendous attention. Interest in such a material arise from the fact that the mechanical, chemical, electrical, optical, magnetic, and electroand magneto-optical properties of these nanotubes are different from their bulk properties, attributed largely to the quantum confinement effects [2–11]. For instance, theoretical predictions have suggested that the Young’s modulus of carbon nanotubes could be as high as 1– 5 TPa [12, 13] and the theoretical tensile strength as high as 200 GPa [14]. Various experimental techniques [15–19] conducted on the mechanical properties of carbon nanotubes also showed very promising results, albeit still much smaller than theoretical prediction. Furthermore, it is widely accepted that the issue of heat dissipation in miniature devices becomes increasingly important as the size of the device reduces. Therefore, carbon nanotubes may play an important role in improving the performance and stability of nanosized devices because of their high thermal conductivity. In spite of the vast potential of nanoscale materials, some inherent problems have hindered significantly, in some case prohibitively, further progress. First, it is extremely difficult to manipulate the sample for any tests due to its sheer size. To conduct a measurement on an individual nanotube, researchers have to select a suitable tube, which is extremely difficult and may result in the situation that the selected tube is very likely not a typical one, and this may be one of the reasons why similar researches usually lead to different results. Next, although many theoretical predictions have indicated unique properties of the nano materials, the traditional test methods and equipment are not designed for them so that it is extremely difficult to say the least to get direct experimental evidence and reliable data to validate the predictions. As a result, we are still largely in a primary stage to probe and investigate the properties, and have proceeded even more slowly for practical applications. Obviously, by assembling the nanotubes into a macroscale object, we can then conduct all the conventional tests at samples of manageable dimensions to examine the material properties, which in turn will lay a solid foundation of experimental evidence to facilitate further studies of all related issues. More importantly, a new bulk material made of nanotubes may offer many attractive applications of its own at the conventional