Preparation And Application Of Nanometer Silver Particle

The silver nano-powders have the unique characteristics due to their effectsof quantum size, small size, surface properties et al. The powders are betterthan the common materials in properties of electronics, magnetics, catalyst,biomedieine, biocompatibility, optical. Nano-silver powder has excellentantibacterial properties, and many products containing nano-silver havegradually penetrated into our daily lives. A nano-silver slurry prepared with thenano-silver particles have excellent properties in electronic chemical,metallurgical, which were used in high-tech value-added products. The mostprominent characteristic is the antibacterial property of silver nano-powders.Many methods have been applied to prepare silver nano-powder, such asphysical methods, chemical methods, a reduction of plant, and a reduction ofenzymes in microorganism. Currently the chemical reduction is more used andmore feasible. But the method often needs to add in a variety of dispersants orstabilizers, easyly cause pollutions to the environment and in the same time,increase production costs. In this study, any dispersants were added into thereaction system during the preparation of nano-silver powder. The usedpreparation method was so called a hydrolysis-thermal-discompose method.Urea was used to control pH value of the reaction solution and released gasfrom the reaction system were used as the dispersion agents. And a nano-silverdispersion slurry was prepared.With the rapid development of electronic andinformation technology, and the microminiaturization and flexibility ofelectronic components, some shortcomings of the micron silver paste isgradually appeared, so nano-silver paste gradually become the focus ofresearches. Now the used nano-silver paste was mostly produced by Europeanand other developed countries, in order to reduce costs and improvecompetitiveness, it is very important to synthesized nano-silver dispersed slurry.In this paper the uniform dispersion silver nano-powders were prepared bya evenly precipitation combining with a thermal decomposition procession. The formation mechanism of silver nano-powder was investigated. Effects of theinitial concentration of silver nitrate (AgNO3), pH value, the temperature andtime of calcinations on the size and morphology of the nanometer silver powerwere studied. The structure, composition, size, morphology and antibacterialproperties of silver nano-power were characterized by X-ray Diffraction(XRD),Scanning Electron Microscope(SEM), Minimal Inhibitory Concentrationmethods and Minimal Bactericidal Concentration methods.The nano-silver slurry was also prepared by dispersing nano-silver powdersin an organic solvent. Effects of the dispersion medium, dispersant, pH value,shear rate and shearing time were studied. The properties of the prepared slurrywere characterized by Determing Solid Powder Content, Zeta and ScanningElectron Microscope(SEM) performance analysis of the dispersion slurry.Results show that it is feasible using a evenly precipitation combining witha thermal decomposition procession to prepare the silver nano-powders. Theconditions for synthesise of the silver nano-powders with crystalline propertiesand belonged to cubic crystal are followings: the initial concentration of AgNO3was0.05mol/L, and the pH value of the precipitation was7. The mixdecapitated materials were calcined at300℃for2h. The obtained dispersivesilver powders has an average size of50nm and takes spherical shape uniform insize. When the silver nano-powders content was9μg/ml, E. coli andStaphylococcus aureus were completely killed in the test of inhibition ofnano-silver powder. The relatively stable nano-silver paste was prepared whenEthyl acetate was used as a dispersing medium,3#chemical was used as adispersing agent,at pH6,stirred for24h with the shear speed of6000r/min.The uniform dispersion silver nano-powders were prepared by a evenlyprecipitation combining with a thermal decomposition procession, has manyadvantages: the raw material is easy to get and cheaper, the side-products in theproduction is recoverable with water. Therefore the processes can meet to therequirements for clean-production of silver nano-powders.Nano-silver dispersedslurry has been tested and meet the production targets.