Preparation And Properties Of Nano-structured Hollow Spheres

Owing to their lower density, larger specific surface area and nano-structured wall, nanometer or micrometer sized hollow spheres often exhibit different physical and chemical properties from solid particles. Hollow spheres have potential applications in many areas, such as optical, electrical, magnetic, medicine-release capsules, drug delivery, light-weight filler, selective adsorption, catalytic and so on. In this thesis, a very simple template-free hydrothermal approach was used to prepare nano-structured hollow spheres. These samples were characterized by XRD, FESEM and TEM. The thesis is composed of the following parts:1. Porous Ni(OH)₂ hollow micro-spheres were prepared via the hydrothermal reaction of Ni(CH₃COO)₂ with aqueous ammonia at 140℃for 12h. Subsequently, the similar nano-structured NiO hollow micro-spheres were obtained by calcining the above precursor at 600℃for 2 h. The formation mechanism of hollow spheres was proposed.2. TiO₂ hollow micro-spheres with highly phase transition temperature have been synthesized on a large scale by means of a simple hydrothermal method without using any templates. The as-prepared products were characterized by field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD) and transmission electron microscopy (TEM). The results showed that the samples are hollow micro-spheres with the diameters of 1～2μm. By photocatalytic degradation of Rhodamine B, indicating that the highly phase transition temperature TiO₂ has better photocatalytic property.3.Micrometer-sized RE₂O₃:Eu³⁺(RE=Y, Gd) hollow spheres were obtained by the hydrothermal reaction using rare earth nitrate-glucose as the precursor, and then calcined treatment. The as-synthesized products were characterized by XRD, FESEM, TEM and photoluminescence spectra. The results showed that the hollow micro-spheres with the diameters of 2～3μm, and the obtained hollow spheres have better luminescecence properties.