Investigation on nanoparticles formation in wire explosion process by fast imaging and optical emmission spectroscopy

Summary form only given. Wire explosion process has long been studied due to its ability to produce nanoparticles with high purity, high energy efficiency and feasibility to be used for mass production. In general, a high power pulsed current is passed through a thin wire to vaporize the wire by Joule heating. Plasma will be formed thereafter when the supplied energy is sufficient to sustain the plasma. The whole process is basically achieved by discharging a capacitor through the wire. Investigations have been carried out to determine the effect of various experimental parameters like ambiance pressure, ambiance gases etc. on the characteristics of produced nanoparticles. The effects of the ambient medium (Ar, N₂ and He) on the size of the nanoparticles were studied by optical emission spectroscopy (OES)¹. It was observed that the size of the nanoparticles formed in Ar ambience increases with increasing pressure, while an opposite trend was observed for the nanoparticles produced in N₂ and He ambiences. In our earlier works^2-4, we have conceptually demonstrated that the arc plasma formation time is crucial for determining the produced nanoparticle size, which is also responsible for opposite trend observed for Ar and N₂/He. It was realized that the expanding vapor of the wire material may be reheated partially or completely by arc plasma depending on the arc plasma formation time. It was also realized that fraction of the wire material may escape from the arc plasma formation region without effected by arc plasma. To understand the mechanism of arc plasma formation and reheating of the vapor, OES and time resolve imaging is carried out. In this report, details of the experiments and the results will be presented.