Papers by Author: Qun Fang Xiao

Abstract: Nanocrystalline Ag doped silica inverse opals were prepared by a sol-gel chemistry method via templating of polystyrene colloidal crystals. The ordered structures of colloidal crystal templates and inverse opals are characterized by scanning electron microscopy. Ag nanocrystals size is estimated as 20~30nm by Scherrer Formula from X-ray diffraction. The color and the stop band of the inverse opals are characterized by transmission spectrum. And five emission peaks of the nanocrystalline silver clusters are observed from fluorescence spectrum.

Abstract: Stir-froth-polymerization is a novel technique for producing highly porous ceramics, in which bubbles are formed by a mechanical frothing in aqueous slurry of ceramic powders. Many work had be done about the porosity, the permeability and the mechanical strength of the porous ceramics derived from this method, but there are still a lot of things remain unclear. This paper focuses on the mechanism of frothing, and the influence of parameters in the mechanical frothing. It was found that the stir time, the stir speed and the viscosity of the slurry have influence on the average cell-size and the distribution of them respectively. The average cell-size can be controlled in the range from 60 to 160 μm by adjusting the parameters.

Abstract: Foaming and gelation of slurry is a recently invented processing route for fabricating porous ceramic. According to the method, a mechanical stir process was introduced to the ceramic slurry added with surfactant, then initiator was added to induce fast gelation between organic monomers and ceramic powder, the green body was obtained after a subsequently drying process. At last, porous ceramic was fabricated after sintering the green body at high temperature. Effects of surfactant volume content and several stirring factors on porosity are studied in this paper. It results that there is a proportional relationship between porosity and Reynolds number which only changes when stir time varies, different slurry or surfactant volume content results in similar relationship between porosity and Reynolds number.