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Silver is an expensive I belong , has a wide range of applications in the field of photosensitive , decoration , electronic industry , catalytic and antibacterial . The nano silver nanomaterials specific volume effect , surface effect , quantum size effect , so that it has many special purpose , shows ordinary silver do not have the special effects in superconductivity , chemical , optical , pharmaceutical and antibacterial is a new type of material for a broad application prospects . Preparation of nano silver powder at home and abroad range of the liquid chemical reduction method is a method widely used in laboratory and industrial . The process conditions of the method is easy to control , equipment requirements are relatively high , the obtained particle size distribution narrower nano-silver , and high yield, ease of industrial mass production . This study used a liquid-phase chemical reduction method , hypophosphite as reducing agent , PVP -protecting agent is a polymer , sodium hexametaphosphate as a dispersing agent , prepared by controlling the reaction conditions , a spherical , good dispersibility and stability of the nano silver sol . Experimental study on the reaction temperature , reducing agent , and the proportion of silver nitrate , the amount of polymer protective agent , the pH of the reaction solution , and the amount of dispersant technological factors on the average particle size of the nano- silver sol , to determine the best nano silver sol prepared process conditions : temperature 50 ° C , the AgNO 3 concentration of 1.0 mol / L , the NaH 2 PO 2 · H 2 O concentration of 0.1 mol / L, and sodium hypophosphite is 2.5 times the theoretical amount , the the PVP with nitric silver mass ratio of 1.0 to 1.2 , hexametaphosphate, sodium and silver nitrate mass ratio of 0.1 to 0.2 , the pH of the reaction solution is 1 and 2, high-speed stirring for 1h . To obtain a brownish red silver sol , the sample with the TEM analysis of the average particle diameter of the silver particles is less than 10nm. Preparation of Nano silver process of solid-liquid separation for liquid chemical reduction , this paper studied the relationship of different pH silver sol Zeta potential , as well as the pH of the solution with the silver particle size , respectively, by using ammonia , organic bases , flocculation agents, organic alkaline mixed reagent as a pH adjusting agent to study the influence of the silver sol condensation , and the purity of the solid-liquid separation after the silver powder , particle size distribution , dispersion, morphology such impact .
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