化学还原法制备片状纳米银粉

通过化学还原法制备了尺寸约30nm的片状纳米银粉。研究表明,十六烷基三甲基溴化铵(CTAB)的位阻效应防止了粉片的团聚,但是过多的CTAB则阻碍粉片的生长,不利于片状的形成,当CTAB加入量与硝酸银质量比为0.8(wCTAB:AgNO3=0.8)时,可获得片状纳米银粉;反应温度为20°C时,CTAB没有完全溶解,不能有效阻止粉片的团聚,同时反应过程缓慢导致粉片明显长大且分布不均匀,升高温度至40°C时,提高了CTAB的溶解度并促进了反应的进行,但当温度达到60°C时,反应速度过快,形核率增加,最终获得细小的粉片。pH值的升高有利于促进反应的进行,保证Ag+反应完全,但是过高的pH值破坏片状银粉周围的双电层结构,导致粉片的团聚,当pH值为6(弱酸性)时,可获得稳定分散的片状纳米银粉。

Preparation of Nano-Silver Flake by Chemical Reduction Method

The nano-silver flake with about 30 nm, was prepared by a chemical reduction method. Cetyltrimethyl ammonium bromide (CTAB) was used to prevent agglomeration of the nanoparticles by its steric hindrance. However, an excessive amount of CTAB will impede the growth of silver nanoparticles, and thus it is not beneficial to the formation of the desired morphology. When the mass ratio of CTAB to silver nitrate is 0.8, the nano-silver with flaky structure can be obtained. At temperature of 20 oC, the solubility of CTAB is low, and it is difficult to retard the agglomeration effectively. At the same time, the low reaction rate will lead to large and nonuniform nanoparticles. When the temperature is 40 oC, the increased solubility of CTAB promotes the forming of nanoparticle. Nevertheless, when the temperature reaches 60 oC, the reaction is so fast that the nucleation rate increases and thus tiny particles are formed eventually. High pH value will lead to promote the reaction and ensure the complete consumption of Ag+, but too high pH may cause damage to the double-layer electronic structure of silver particles, resulting in collapse and agglomeration of the formed particles. When the pH value is around 6, stable nano-silver flakes can be obtained in a uniform dispersed form.