Electronical Properties Of Low-dimensional Nanostructured Systems And Stress Effects

Nanostructured materials, especially low dimensional nanostructured materials, have been making a great revolution in the last decade due to the development of synthesis procedure and technique. Using a variety of synthesis methods, it is possible to produce nanostructured materials in the following forms: clusters, fibres, thin films, coatings, powders and as a bulk material. These materials are modulated in zero to three dimensions on length scales less than 100 nm. The atomic structure of these nanostructured materials is unlike that seen in glasses or crystals because of the large volume fraction (5~50%) of grain boundaries or interfaces. This may result into some new physical and mechanical effects such as quantum size effects, surface and interface effects,and piezoelectricity. As a result, the physical and mechanical properties of the nanostructured materials show remarkable improvement or deviation from the properties exhibited by the glasses or crystals. It is now realized that the properties of materials can be engineered by controlling the sizes of their building blocks (nano grains) and their assembly. A new subject, Nanomaterial Science, has been formed, which intersects with physical mechanics, nano mechanics, condensed matter physics, nanophysics, surface physics, physical chemistry and mathematics. As a result, there appear a series of problems of Mechanical Fundament. However, it is a challenge to understand the mechanism and physics of the singular properties of the imperfect nanostructured systems. The main difficulties lie in that the classical mechanics, lattice dynamics, molecule dynamics and other traditionally theoretical and numerical methods have not been well suitable to study such systems with a broken symmetry. So it is necessary to explore some new way to study theoretically the physical and mechanical properties of nanostructured materials.As a typical representation of low dimensional nanostructured systems, carbon nanotubes are very strong - one of the strongest materials, as a matter of fact. They are so strong that they can be bent back and forth several times with no serious...