Optimized Design and Implementation for Discharge Circuit of Micro-Electrical Discharge Machine in Preparation of Nano Silver Colloid

In this study, nano silver colloids were prepared using the Electric Spark Discharge Method (ESDM). The electrodes (metallic silver with a purity of 99.9%) on both ends were connected to a pulse power supply and the insulation of the dielectric fluid was destroyed using electric field action to produce the electric discharge phenomenon with an electric arc of up to 5000-6000 K generated between both electrodes. The temperature of the electric arc was sufficiently high to melt or vaporize the electrodes and at this moment, the molten particles of the electrodes sputtered nano silver particles, which were then suspended stably in the dielectric fluid. This study was conducted under Normal Temperature and Pressure (NTP) without the addition of surface active agents, which was a novel and rapid way of preparing nano materials. It is feasible to prepare nano silver colloids using industrial-grade electric discharge machines (EDM), however the cost is too high for huge volumes and it is not easy for maintenance; hence, this study improved the rate of discharge using an optimized discharge circuit based on the previous self-designed micro-electrical discharge machine (Micro-EDM). After optimization, the discharge success rate improved from 25% to 50% and the voltage of the gap between both electrodes (Vgap) was stable, which greatly improved the discharge efficiency. In the end, the nano silver characteristics were verified using UV-Visible Spectroscopy (UV-Vis), a Zetasizer Nano System (Zetasizer), and a Transmission Electron Microscope (TEM).