The Preparation And Study Of Monodisperse Silica Microspheres And Core-shell Structure Materials

In recent years, there has been intense interest in the fabrication of core/shell materials in the field of material science. Core-shell materials, often made up of a solid core surrounded by a well-defined shell layer, are known to exhibit unique and advanced properties over single-component nanoparticles, making them attractive for use in a wide range of applications, and are therefore of extensive scientific and technological interest. The structure, size, and composition of these particles can be easily altered in a controllable way to tailor their magnetic, optical, mechanical, thermal, electrical, and catalytic properties. The core-shell particles can be used as a precursor form to produce hollow spheres or to lower the cost of precious materials by coating them on inexpensive cores. Nowadays, the most commonly used to be the nuclear is monodisperse SiO₂, such microspheres have the same chemical composition, particle size and surface properties. The improvements focused on the preparation of monodisperse, particle size is small and homogeneous SiO₂ powder, and used monodisperse SiO₂ microspheres form a class of core-shell powder, which has a potential research value and potential applications.In this article, monodispersed silica particles templates were produced by Stober method. The morphology and size of the particles were characterized by transmission electron microscopy (TEM) and particle size analyzer. We had studied the effections of different agents and reaction conditions of ethanol on the SiO₂ particle size and dispersion in the ammonia catalyst, and discussed its mechanism. Secondly, we had synthesised core-shell powder for monodisperse SiO₂ is the nuclear using the sol-gel method, including SiO₂@Y₂O₃, SiO₂@YAG:Ce³⁺, etc., and the core-shell powders were characterized by transmission electron microscopy (TEM) and X-ray powder diffraction. The results are as follows:(1) Microspheres SiO₂ were prepared by hydrolysis of tetraethoxy silane (TEOS) in alcohol-water mixed solvents using ammonia as catalyst. The results show that the monodispers of silicon dioxide will be affected by the alcohols, and with the alcohol carbon chain growth, SiO₂ microspheres increased size, size distribution broadens.The particle size of SiO₂ microspheres had changed, with the different of reaction solution, ethyl silicate concentration, water concentration, ammonia concentration and system temperature.(2) Core-shell powder SiO₂@Y₂O₃ were synthesised by sol-gel method. XRD and TEM indicated that Y₂O₃ did not reaction with SiO₂ nuclear, The diffraction peak intensity increased with the sintering temperature, but did not produce new diffraction peaks, The core-shell structured phosphor particles were smooth and uniform, maintained the morphology of monodisperse SiO₂. The thickness of the shells could be easily controlled by changing the number of deposition cycles. (3) Core-shell powder SiO₂@YAG:Ce³⁺ were synthesised by sol-gel method, XRD and TEM indicated that the YAG:Ce³⁺ did not reaction with the SiO₂ nuclear, and YAG:Ce³⁺has crystaled in the SiO₂ surface at the sintering temperature 800℃, and the core-shell structured phosphor particles were smooth and uniform, maintained the morphology of monodisperse SiO₂ (about 300 nm). The thickness of the shells could be easily controlled by changing the number of deposition cycles.