Preparation And Properties Of Ultrafine Silver Powder

Ultra-fine silver powder is a kind of functionality powder material which has some special physical and chemical properties.Therefore,it was widely used in the chemical catalysis,biomedical,clinical treatment,environment,and electronic technology and other fields.And ultra-fine silver powder attractes a large of researchers of different countries.With the rapid development of electronics industry and the photovoltaic industry,the market demand for ultra-fine silver powder is also growing.At the same time,with the development trend of the miniaturization and integration for the electronics industry,people have more and more higher expectation for the quality of the ultra-fine silver powder.This paper used AgNO3 as the the source of silver under the two conditions that in the silver nitrate solution(silver is in the form of Ag+)and in the silver-ammonia solution(silver is in the form of Ag[(NH3)2]+)to prepare ultra-fine silver powder by liquid chemical reduction method.The silver powder was characterized by scanning electron microscopy,X-ray diffractometer,laser particle size analyzer and bulk density test.The effect of the addition methods of reducing agent,the concentration of the urce of silver,the amount of dispersant,the reaction temperature on the performance of the ultra-fine silver powder was investigated.The results of the study are as following:In the Ag+ solution,ascorbic acid as the reducing agent,ammonia as the regulator of pH value,under the circumstance of the concentration of AgNO3 is 1mol/L,the reaction temperature is 20℃,the additive amount of the PVP was 1%of the mass of Ag,the ascorbic acid solution was quickly added into the AgNO3 solution,using ammonia to control the pH value between four to six in the process of reaction,we can prepare the rough surface of near-spherical micron-sized silver powder which has narrow particle size distribution,the median diameter is 7.04μm,apparent density is 2.15g/cm3.Under the circumstance of the concentration is 0.1mol/L and other conditions unchanged,we can prepare the rough surface of near-spherical ultra-fine silver powder which has narrow particle size distribution,the median diameter is 0.46μm,apparent density is 1.72g/cm3.In the Ag[(NH3)2]+ solution,hydrazine hydrate as the reducing agent,under the circumstance of the concentration of Ag[(NH3)2]+ is 0.5mol/L,the reaction temperature is 20℃,the additive amount of the PVP was 10%of the mass of Ag,the hydrazine hydrate was drop wise added into the Ag[NH3)2]+ solution,we can prepare the smooth surface of near-spherical micron-sized silver powder which has broad particle size distribution,the median diameter is2.50μm,apparent density is 1.67g/cm3.By comparing the representative of the silver powder prepared by the two different redox systems can be seen that,in the Ag+ solution system,the formation of silver powder prepared by ascorbic acid as the reducing agent is the aggregation growth of the of the silver particle,and In the Ag[(NH3)2]+ solution system,the formation of silver powder prepared by hydrazine hydrate as the reducing agent is the uniform growth of the silver particle.