Preparation And Properties Of Silver Micro-nano Materials

Silver micro-nano materials have a broad application prospect since their excellent electrical conductivity,thermal conductivity,antibacterial and catalytic activity.With the continuous expansion of the photovoltaic market,the demand for high quality silver powder is increasing.However,there is still a big gap between the preparation technology of anode silver powder for solar cells in China and that of foreign countries,and the silver powder market is monopolized by foreign countries.It is imperative to explore the industrialization preparation of high quality positive electrode silver powder.Moreover,there is also serious water environment pollution with the industrial development and progress,in which exist in the industrial waste water of 4-nitro phenol?4-NP?is a common and toxic organic pollutant.Silver micro-nano materials have excellent catalytic activity in catalytic reduction of 4-nitro phenol,but the single silver micro nanoparticle are prone to agglomeration.Transition metal oxides have excellent physical and chemical stability,but their electrical conductivity limits their catalytic activity.Therefore,it is of great significance to combine of silver micro-nano materials and transition metal oxides for the preparation of high performance catalysts.In this article,the superfine silver powder was prepared by liquid phase reduction method,and the effects of different dispersants,adding method,temperature,p H value,dosage of dispersant on the morphology and particle size of silver powder were studied.The results showed that the silver powder with uniform particle size and smooth surface could be obtained by adding oxidant and reducing agent to the base solution which was made by mixing part of ascorbic acid solution and quantitative dispersant with gum Arabic as dispersant.With the increase of p H value,silver particle size decreases gradually.The morphology and particle size of silver powder are affected by the temperature and the amount of dispersant.When the optimal reaction conditions were selected for the amplification experiment,it was found that the morphology and particle size of silver powder gradually deteriorated with the magnification of the experimental multiple.Under the condition of 20-fold amplification,the reaction parameters were optimized to obtain ultrafine silver powder with average particle size of 1.71 um,vibrational density of 5.68 g/cm³,uniform particle size distribution and regular morphology,and the photoelectric conversion efficiency of the positive electrode silver paste was up to 18.438%.In addition,a flowery silver microspheres?Ag MPs?composed of silver nanoparticles can be obtained by regulating the reaction parameters.Using it as a carrier,sheet-shaped nickel oxide?Ni O?was loaded on the surface by a uniform precipitation method to obtain an Ag@Ni O composite material.The catalytic performance of the Ag@Ni O composite was studied,and it was found that it had an electronic synergy effect in the process of catalytic reduction of 4-NP.Compared with the unloaded Ni O flower-shaped silver microspheres,the catalytic performance was improved by nearly40 times and much higher than Ni O.At the same time,the effect of different Ni O loadings on the catalytic performance of Ag@Ni O was studied.The results showed that the Ag@Ni O composite catalyst prepared by 0.55 g nickel source had the highest catalytic performance,and its reaction kinetic constant?k?was 25.82×10^-3 s^-1,the turnover frequency value?TOF?was 113.03×10^-5 mol g^-1 s^-1and after five cycles,it still has a 90%conversion rate.