| For the particular construction and excellent properties, ultra-fine powders can be used in many fields. In this article, ultra-fine silver powders and Ag-loaded photo-catalyst Ag-TiO2 were studied. The principles and applications of surface electric characteristic, the development of ultra-fine particles including Ag-loaded photo-catalyst Ag-TiO2 were reviewed. It was found that surface electric characteristic, the relation between modification and ζ potential of silver powder as well as the relation between the surface electric characteristic of Ag-loaded photo-catalyst Ag-TiO2 and its photo-catalytic activity were rarely studied, but it is necessary to have the silver powders modified ahead of putting them into use. So the surface electric characteristic of Ag and Ag-loaded photo-catalyst Ag-TiO2 and their capabilities of decomposition were researched in this paper. I . The research of preparation and surface electric characteristic of ultra-fine silver powder.In this article, ultra-fine silver powder reduced by H2O2, tannic acid and radiation etc were attained, we also had their ζ potential or iso-electric point(IEP) measured by JS94F microelectrophoresis-meter, their shapes and sizes were observed. We found that the methods of preparation of ultra-fine silver powder have much influence on their ζ potential and IEP, the higher absolute value of the particles' ζ potential, the smaller the prepared particles. II. The dispersoid stability of the ultra-fine silver powderHad the ultra-fine powder of silver reduced by ascorbic acid dispersed in water, we researched the influence of the ions intensity(concentration of NaNO3), concentration of glutin and surfactant (Brij-35) on the dispersoid stability and ζ potential. The experiment showed that the higher ions intensity in silver system, the lower its ζ potential, and the poorer dispersoid stability. Had silver powder modified by glutin, we found that increasing the concentration of glutin, its 4, potential will change into positive from negative and keep fixed value at higher concentration. When add Brij-35 into the silver dispersoid, its stability is buildup. III. The ζ potential and dispersoid stability of modified ultra-fine silver powderModified ultra-fine silver powders were also attained by radiation glutin/ Ag+ system, relative uniformity and well dispersive silver powder were gained, the influence of the concentration of glutin, Ag+ and radiation time on ζ potential and optics property etc were examined. We foundthat the kinetics of preparation of silver by radiation the system of glutin/ Ag+ accord withfirst-order equation; the ζ potential can be used in balancing the condition of modification, theIEP of silver sol reduced by radiation decrease with the concentration of silver and increase withthe concentration of glutin; the influence of radiation time on IEP rely on the destroyed degree ofglutin.IV. The electric characteristic and photo-catalytic activity of Ag-loaded photo-catalyst Ag-TiO2We also prepared Ag-loaded photo-catalyst Ag-TiO2 by ultraviolet radiation, and researched the capability of decomposing methylic orange. The influence of the content of Ag, radiation time, baking temperature and baking time on photo-catalytic activity and 4 potential were tested, and the relation between photo-catalytic activity and ζ potential were also discussed in details. The experiments indicated: the photo-catalytic activity of Ag-loaded photo-catalyst Ag-TiO2 and the use-rate of sun were enhanced. Therefore, the Ag-loaded photo-catalyst Ag-TiO2 synthesized at low baking temperature, short baking time, the content of Ag equals to 0.1% and the reducing time of Ag+ equals to 5 minutes reach the best photo-catalytic activity. The absolute value of ζ potential for Ag-loaded photo-catalyst TiO2-Ag depends on the content of Ag, reducing time of Ag+, baking temperature and baking time. The higher surface 4 potential, the better for Ag-loaded photo-catalyst TiO2-Ag to catalyze methylic orange. Ag-loaded photo-catalyst can completely de...
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