Nano- and Micro- meter Sized Silver Metal Powders by Microwave-Polyol Process

Microwave-solvothermal processes have been previously found to be highly suited for the synthesis of a wide variety of ceramic and metal powders. In this paper, the effect of microwave radiation on the formation of Ag powders from AgNO₃ using ethylene glycol as a reducing agent at 100 - 200°C was investigated. Silver powders were rapidly produced by using microwave radiation. The formation yield of Ag powders from AgNO₃ reached 98.6% by treatment for 23 min at 160°C and 97.4% by treatment for 2 min at 200°C using the microwave-polyol (M-P) process. Silver powders of 0.15 to 1.0,0.15 to 1.2, and 0.35 to 1.8μm in diameter were produced at 100°C in 10,20, and 30 min, respectively via M-P reaction. The particle size increased further and then strongly aggregated at 160 and 200°C. By the addition of polyvinyl pyrrolidone (PVP) as a protective polymer to the mixture of AgNO₃ and ethylene glycol which was treated at 160°C, smaller Ag particles of 62 to 78nm in diameter were obtained.