Modification of Nano/Micromaterials

Although nano/micromaterials have attracted considerable attention due to their excellent physical properties and geometrical merits, these should be modified for specific purposes or be assembled in systems for many fields of application. The cutting and welding of materials must be the principle operation for this purpose. The welding and cutting technology utilizing Joule heat is first described together with some experiments and applications. First, heat transfer problem in thin wires are treated. And then, two Pt wires with diameters of about 800 nm are shown to successfully be welded by Joule heating. Melting and solidification at the point contact of thin wires occurred continuously under a constant current supply and the welding of wires is completed within several seconds in self-completed manner. Moreover, the welding technology for low-dimensional materials have been found to be effective for manipulating materials and for generating functional elements, e.g., electromagnetic rings and thermoelectric elements. A unique technique for creating nanocoils from straight nanowires is described.