Synthesis, Microstructure And Properties Of Several Low-dimensional Materials

The properties of materials electronic, mechanical, optical, magnetic and chemical will change curiously when at least one of three dimensions of bulk materials decreases down to nano-scale. The investigations of synthesis, microstructures and properties of low-dimensional materials have been frontier fields and hot research topics in materials science, condensed physics and materials chemistry. In this dissertation, carbon, as a multi-functional material, was employed to investigate the synthesis, microstructure and their properties of zero-dimensional pyrolytic carbon spheres, one-dimensional carbon nanotubes and new carbon structures. For two-dimentional materials, thin copper films with high conductivity and low electromigration and Ni-P amorphous thin films used in computer harddisks were selected. The mechanical properties of the thin films subjected to monotonic and cyclic loading were investigated to elucidate the size effects.Solid carbon spheres with a smooth surface, almost perfect round shape and monodispersity were synthesized by pyrolysis of tetrahydrofuran without using any catalysts. The aromatic compounds and those with some characteristics intermediate between aromatic and aliphatic were selected to be carbon source, and the synthesis methods of pyrolytic carbon spheres were investigated as well. The carbon spheres with diameters of 100 nm to 1 μm were synthesized by using different carrier gases, controlling the flow rates and the proportions of the carrier gas. The microstructures of the carbon spheres were systematically investigated by scanning electron microscope, high-resolution transmission electron microscope (HRTEM), X-ray diffraction and Raman spectroscopy, etc. The results indicate that the spheres consist of an underdeveloped spiral-shell core and a surface with discrete fragments of concentrically arranged graphene layers. The underdeveloped spiral-shell structure changes into a well developed spiral-shell structure after heat treatment at 2100 ℃. The appearance of the shoulder peak at 26.42° in the pattern of X-ray diffraction confirms the presence of a special crystal structure in the core part of the spheres. Thermogravimetric analysis and the HRTEM observations of carbon sphere surfaces demonstrate the presence of the spiral-shell structure. It is found that the spiral-shell core transforms into continuous...