Study On The Preparation Of Ultrafine Silver Powder

The electronic paste with silver powder as conductive phase has a wide range of applications in the photovoltaic,microelectronics and internet of things industries.The performance of silver powder depends on its particle size,morphology,dispersion,particle size distribution,and tap density.Therefore,it is of great significance to study the preparation of submicron silver powder.the liquid-phase chemical reduction method was used to prepare the ultral silver,silver nitrate and ascorbic acid was used as the silver source and the reducing agent respectively,various additives were added,the reaction conditions were adjusted,and the main influencing factors in the preparation process were explored to prepare the morphology and High-quality silver powder with controllable particle size,and study the role of different dispersants in silver nitrate solution.The process of preparing silver powder was investigated by Rapid addition and slow dropwise addition with gum arabic?GA?and polyethylene glycol-4000?PEG-4000?as dispesant respectively.The silver powder prepared by the fast feeding process with PEG-4000 as dispersant is more suitable for preparing the conductive paste.spherical silver powder and flake silver powder can be prepared by controlling the addition amount of sodium citrate as an additive,the effects of temperature,pH,the molar ratio of reducing agent and silver nitrate,the concentration of silver nitrate on the properties of the prepared ultrafine silver powder were studied.For spherical silver powder,when the pH is less than 2.5,the dispersion of silver powder is good,and the temperature is not less than 65?,the small crystal grains that make up the silver powder will become larger,and when the concentration of sodium citrate is not less than 0.0034mol/L,the silver powder is spherical.For flake silver powder,the smaller the pH value,the better the dispersion of silver powder.The thickness of flake silver powder increases with the increase of temperature.When T?50?,the silver powder turns into a snow-like shape,only when n?ascorbic acid/nitric acid?is 0.6,the flake silver powder is structured.When the concentration of sodium citrate is not less than 0.0009 mol/L,the thickness of silver powder is small and little change occurs.Orthogonal experiments were used to study the interaction between various factors,and the effect of these factors on silver powder morphology,dispersion and particle size were studied.The key factor affecting the average particle size of silver powder is pH.The key factors affecting the silver powder dispersant are the temperature and the amount of dispersant.Different silver powders prepared under different pH conditions with different morphologies.The mechanism of action of different dispersants was studied.It was found that the coordination ability of PEG-4000 and AgNO₃ decreased with the increased concentration of AgNO₃,and the coordination ability of the other four dispersants and AgNO₃ increased with the increased concentration of AgNO₃;When the amount of PEG-4000 increases,its coordinating ability with AgNO₃ was weakened in 0.01 mol/L AgNO₃ solution and enhanced in 0.1 mol/L AgNO₃ solution.