Preparation Of The High-quality Superfine Silver Powder By The Liquid Reduction

Abstract:To meet the increasing demand of the high-quality ultrafine sphere silver powder, and improve the added-value of the silver product, the production of the high-quality micro-sized and submicro-sized silver powder were conducted systematically throuth three different liquid reduction systems, using the silver nitrate as the silver resource. The feasibility of approaches was discussed and the results were as follows:(1) Without the addition of dispertant, the dispersive spherical silver powder with average diameter of1.17μm, tap density of4.2g/cm3were prepared under the optimum conditions in the acid reduction system with the ascorbic acid as the reductant. The so-obtained silver powder can be used in the front silver paste of solar cells. It was indicted that the nucleation and the growth of the silver particle was in accord with the Lamer Model by the rapid feeding mode, and the cyclic structure of the ascorbic acid molecule plays the self-dispersive role during the growth process. Due to the simple raw material, easy operation and high reaction rate, the process has broad prospect of industrialized production and popularization significance.(2) The superfine sphericla silver powder which meet the national standard of PAg-G2.0with the average diameter of0.965μm, tap density of1.69g/cm3was prepared under the optimum condition by the ascorbic acid reduction of the silver ammonia complexation solution. The product can be used in the low-temperature silver slurry in the electronic industry. The process was easy to operate, easy to control, suitable for quick and large-scale production of low and medium-grade silver powder.(3) The quasi-spherical silver powder which can meet the national standard of PAg-G7.0with the average diameter of2.75μm, tap density of4.34g/cm3was prepared in the room temperature by H2O2reduction of the silver annomia complexation solution. While the gas produced by the self-decomposition of the H2O2was dedicated to the local stirring and can effectively inhibitate the aggregation. Though the process was low-cost and easy to control, it was not suitable for large-scale production.