Study Of Controllable Preparation And Scale-up Experiments Of Micro-nano Silver Powder

Micro-nano silver powder is an important industrial raw material. However, the source of micro-nano silver powder still mainly relies on import, so it is highly desired for domestic researchers to explore a simple, high yield, low cost and controllable preparation method for different silver powder.In this thesis, we prepared spherical and dendritic silver powders in aqueous phase system and prepared single crystal silver powder in alcohol-phase system. We investigated the effect of the preparation parameters of the three types of silver powder, including reductant species, type of dispersant, control agents, stabilizers, complexing species, the reaction temperature and time, p H value, and etc., on the average particle diameter size distribution, degree of sphere, the tap density, and yield of the silver powder. And then the preparation process is optimized.In this thesis, the average particle size of spherical silver powder continuously decreased from 3.53 μm to 0.96 μm by increasing the content of gum arabic dispersant from 6% to 15%. The average particle size of spherical silver powder continuously increased from 1.86 μm to 4.75 μm by decreasing p H value from 4 to 1.5. The optimized preparation parameter of dendritic silver is 1% sodium chloride as nucleation control agent, gum arabic as dispersing agent, ascorbic acid and stabilizer o-phenylenediamine mixed system as reduction system, and the reaction temperature being controlled at 20 oC. Main branches were about 6 μm to 7 μm and lateral branches were about 1 μm to 3 μm. We could control the shape and size of the tree structure by controlling the addition amount of the stabilizer o-phenylenediamine. The length of the main branches was about 5 μm to 8 μm and that of the lateral branches was about 0.8 μm to 1 μm. In the preparation of single crystal silver powder, we used a mass ratio of 0.0125 for dispersant PVP 1,300,000. We controlled the mass ratio of copper chloride agent from 0.0003 to 0.003, pretreatment temperature of 110 oC, and reaction temperature of 140 oC for 2 hours, and the average particle size of the prepared single crystal silver was 0.8-1.4 μm. The particle size of single crystal silver powder decreased with increasing the preparation time.In this thesis, the scale-up experiments of spherical, dendritic, and crystal silver were carried out. Spherical morphology of the silver powder could maintain when the feeding of silver nitrate increased to 1700 g, but the sphericity and monodisperse deteriorated to some extent with further magnification. Experimental amplification for fabricating dendritic silver powder could not achieve the slimiliar result to the standard test, and only part of the product exhibitied dendritic morphology. The scale-up experiments of crystal silver powder had a good reproducibility and stability when the feeding of silver nitrate increased to 3400 g. Almost no obvious change of crystal morphology, tap density and yield were observed, so it is of high potential in industrial production of this type of silver powder.