Study On Preparation Of Foamed Silver By The Electrodeposition Methods And Its Property

Silver is a conventional industry catalyst. The existing silver catalyst has a lot of defects such as low porosity, little effective reaction surface area , poor fire-resisting property and so on, so it is necessary to find a new kind of silver catalyst that is resistance to high temperature with high specific area, uniform structure and good currency. Foamed silver catalyst is a kind of perfect material instead of existing silver catalyst due to its high porosity, large specific area, light mass, good currency and low heat conductivity.The process that foamed silver catalyst was prepared by electrodeposition methods of pretreatment, chemical plating, elcetordeposition, burning and reduction sinter in the base of polyurethane foam.The experiment of pretreatment shows that polyurethane foam can be washed clearly in both organic and chemical unoil, good effects of coarsening can be gained only if polyure foam can be squeened repeatly and uniform mass loss between 2.0 and 3.0mg·cm^-3. The result of activation is perfect even if the cheaper silver nitrate instead of expensive palladium bichloride is used as active agent in the experiment.The influence on quality of chemical plating, conductivity, depositon rate by the kinds of reduction, silver contents, PH and stabilizing agent was studied. The results of shows that ideal result of chemical silver plating in the polyurethane foam can be achieved only if the glucose is chosen as reductant in chemical silver plating and its concentration of silver ion is between 5 and 6g·L^-1,concentration of glucose between 10 and 12g·L^-1,content of thiourea 0.5mg·L^-1and PH between 12 and 13.The influencing factor such as PH, temperature, time of electrodeposion and cathode current density so on in electrodeposition silver was studied. Cladding silver with tiny crystal grain and bright surface can be gained in the condition of plating solution with about 25℃,PH9.0, cathode current density between 0.3 and 0.4A·dm-2 .Uniform foamed silver can be made by burning in the temperature of 600℃and reduction sinter in the temperature of between 800 and 850℃in electrodeposited polyurethane.The skeleton structure of foamed silver and its surface were studied by analytical equipment such as scanning electronic microscope. The result shows the made-up foamed silver in the experiment is a space stretched out, pentagon and polyhedral structure. The skeleton of foamed silver is hollow, open-tubular"thoroughfare"and its entire skeleton is made up by"thoroughfare". There are a lot of dispersal granular tiny bulges on the surface of the skeleton of foamed silver.The foamed silver made in the experiment is a pure crystal silver and its specific area of foamed silver is 0.5994 m²Â·g^-1 measured by BET, the tensile strength 0.73MPa, porosity over 98% and the times of non-breakdown by repletion bend in room-temperature are over 6.