光诱导还原法制备片状银粉的研究

Preparation of Flake Silver Powder by Photoinduced Reducing Method

在光诱导下,以抗坏血酸（VC）和乙醇为还原体系,PVP与PVA为混合保护剂还原制备了片状银粉。研究表明,反应温度过高或过低均不利于控制银粉的粒径大小。50-60℃的反应温度既可以提高反应速率又能增加银晶核的形成;混合保护剂的使用比单独一种保护剂能使银粉具有更好的分散性能;而光源的入射波长、入射强度以及光辐照时间可以改变银粉的形貌;光照时间小于15 h制备的银粉呈球形或类球形且颗粒大小粗细不一;光照时间为15-45 h时银粉呈球形,颗粒大小均匀统一;光照时间45 h以上有利于片状银粉的形成。通过对反应温度的调整、表面保护剂的选择和光辐照时间的控制获得了制备片状银粉的较优工艺。在反应温度55℃,nNH3·H2O/nAg＋=6,nVC/nAg＋=9.5,nPVP∶nPVA∶nAg＋=0.5∶1.0∶1.0（摩尔比）,50 W高压汞灯（波长352 nm）辐照45 h,Ag NO3浓度为0.2 mol·L-1的条件下,得到粒度分布均匀,结晶度高,分散性良好的片状银粉。

Using ascorbic acid and ethanol as reducing agent, polyvinyl alcohol and polyvinyl prorrolidone as mixed protecting agent, the flake silver powder was synthesized under lighting irradiation. The experiments results showed that the reaction temperature were not conducive to control the particle size of silver powders when it was too high or too low. The temperature of 50 - 60 ℃ could improve the reaction rate and increase the silver crystal nucleus formation; the use of mixed protectant could make silver powders have better dispersion properties compared with using sole protective agent ; the intensity and the wavelength of incident light source, and light irra- diation time could change the shape of silver powders ; when the illumination time was less than 15 h, the silver powders were of spheri- cal particle shape or the like with different thicknesses and sizes. Spherical silver powders with uniform particle size were obtained when the illumination time was 15 - 45 h. Illumination time of more than 45 h were favorable for the formation of chip powders. The experiment condition to prepare flake silver powders was optimized by adjusting reaction temperature, the selection of protective agent and the control of light irradiation time. The flake silver powders with high crystallinity, uniform particle size distribution and excellent self-dispersal property were prepared under the following condition： reaction temperature of 55 ℃, nNH3.H2o/nAg ＋ = 6.0, nVC//nAg ＋ = 9.5, npvp： nevA ： nAg ＋ = 0. 5： 1.0： 1. 0 （ mole ratio） , AgNO3 concentration of 0.2 mol·L^-1 , and irradiated by high pressure mercury lamp（50 W, wavelength with 352 nm） for 45 h.