反相微乳液中纳米银粉的合成

Fabrication of Nano-silver Powder in Inverse Microemulsions

以次亚磷酸钠还原剂,采用反相微乳液法制备纳米银粉;并借助TEM、X射线衍射和粒度分析仪研究了反应温度、水和表面活性剂的摩尔比、Ag＋浓度和助表面活性剂对纳米银粉的粒径大小的影响。结果表明：随着水和表面活性剂的摩尔比的增加,纳米银粉的粒径尺寸随之变大;随着银离子浓度的增大,纳米银粉的粒径变小,当银离子浓度超过0.1 mol/L时,纳米银粒子出现团聚明显的现象,且粒径大小分布范围变大;随着助表面活性剂用量的增加,纳米银粉的粒径先降低,当正己醇的用量超过0.2 mol时,粒径大小反而缓慢增大;反应温度不太高时（20℃,40℃）,纳米银粉的粒径分布大致都在20～40 nm之内,当温度高于60℃时,纳米银粉粒径分布不均匀且形状不规则,且出现明显的团聚现象。适宜工艺为：温度为40℃,水和表面活性剂的摩尔比ω=1,Ag＋浓度为0.1 mol/L,助表面活性剂（正己醇）的用量为0.2 mol;制备的纳米银粉为面心立方晶系纯相银、分散性好、规则球形形状、粒径分布均匀、平均粒径为22 nm。

Nano-silver powder was prepared using sodium hypophosphite as the reduction agent by inverse microemulsion. The TEM, XRD and laser particle size analyzer were used to characterize the effect of reaction temperature, the water-to-surfactant molar ratio, Ag-ion concentration and cosurfactant on particle size of the nano-silver powder. The results show that as increasing the water-to-surfactant molar ratio, the particle size of nano-silver powder becomes larger. And with the raising of Ag-ion concentration, the particle size of nano-silver powder reduces until Ag-ion concentration reach 0.1 mol/L, then the particle size distribution widens together with obvious convergent phenomena. As the dosage of cosurfactant increases up to 0.2 mol, the particle size of nano-silver powder reduces gradually, afterwards the particle size grows large slow adversely. The temperature has a great effect on the particle size of nano-silver, the particle size ranges from 20 nm to 40 nm when the temperature is 20 ℃ and 40 ℃, and the nano-silver with irregular shape and visible convergent phenomena. Pure nano-silver powders with both face-centered cubic structure and better dispersibility, regular spherical shape, uniformly distributed grain（mean particle size of about 22 nm） can be obtained in the condition of the reaction temperature of 40 ℃, the water-to-surfactant molar ratio of 1, Ag＋ concentration of 0.1 mol/L and cosurfactant of 0.2 mol.