Study On The Preparation Processing Of Highly Dispersed Ultrafine Silver Powder By Liquid-phase Reduction Method

With the rapid development of photovoltaics,electronics and other industries,the demand for high-conductive pastes with silver powder as the main functional phase is increasing,and the market demand for silver powder is increasing.The characteristic parameters such as the morphology,particle size,and dispersibility of silver powder have a significant influence on the process performance and use performance of conductive paste.At present,our country has a large gap with foreign countries in the preparation of high-performance silver powder technology.Research on the preparation technology of performance silver powder is of great significance.In this paper,ultrafine silver powder was prepared by liquid-phase reduction method.The effects of process parameters such as concentration of reactant,type and amount of dispersant,p H value and reaction temperature on morphology,particle size and dispersity of silver powder was systematically studied,and the silver powder was analyzed and characterized by means of scanni ng electron microscope(SEM),X-ray diffractometer(XRD),laser particle size analyzer,specific surface area tester,infrared spectrometer,etc.The results are as follows:Using ascorbic acid as a reductant,the effects of factors such as concentration of Ag NO₃,type and amount of dispersing agent,reaction temperature,p H value of reducing mixed liquid on the morphology,particle size and dispersi ty of silver powder were studied using orthogonal experiments.The optimized process conditions are as follows:silver nitrate concentration is 0.3mol/L,reaction temperature is 25?Tween-80 is dispersant,dispersant/silver nitrate(mass ratio)is 20%,and p H of the reducing mixture is 5.The morphology of the silver powder prepared under this process is quasi-spherical,and has good dispersibility.The d₅₀ size of the silver powder is 3.33?m.The optimized process was magnified 10 times and the d₅₀ size of the silver powder is 4.33?m,the bulk density is 1.74 g/cm³,the tap density is2.85g/cm³ and the specific surface area is 0.519m²/g.Using benzotriazole(BTA)as the dispersant,single factor variable experiments were used to study the influence of the addition methods(dispersant addition method and reaction solution addition method),BTA dosage,silver nitrate concentration,reaction temperature,reducing agent p H value on the morphology,particle size and dispersibility of the silver powders,and it can be controlled by the process control to reduce the average particle size of silver powder from 2.40?m to 0.83?m.On this basis,orthogonal experiments were used to study the influence of silver nitrate concentration,amount of BTA,reaction temperature,and the p H value of reducing agent on the morphology and particle size of silver powder.The optimal process obtained through experiment optimization is:the conc entration of Ag NO₃ is 0.2mol/L,the amount of dispersant benzotriazole added BTA/Ag NO ₃(mass ratio)is 0.10,the reaction temperature is 25?,the p H value of the reducing agent solution is 5,the morphology of the silver powder prepared under this process is spherical,the silver powder particles are uniform and have good dispersibility,the particle size distribution is 0.58-1.94?m,and the average particle size is 1.29?m.Infrared spectroscopy was used to study the dispersion mechanism of the silver powders using benzotriazole as a dispersant.The results showed that benzotriazole can form Ag_(surf)-N with Ag through its structural N atoms and adsorb to silver particles,the surface of the surface can generate steric hindrance to prevent the agglomeration of silver particles.