Exploring the Influence of the Evolution of Discharge Plasma Channel on the Characteristics of Electric Explosion Products

Electrical explosion method as a powerful tool for one-step synthesizing metallic nanoparticles has raised widely interests. In this paper, experiments were performed with three metal wires, namely copper, tungsten and titanium who are the typical representation of non-refractory and refractory metals. High-speed photography along with electrophysical and optical diagnostics were applied to characterize the electrical explosion. Accordingly, SEM and TEM was used to characterize the micro-morphology of explosion products. XRD was used to detect the phase compositions. Experiment results indicated that the products morphology and particle size distribution were influenced by the dynamic behaviors of the exploding wires. Electrothermal instability (ETI) and secondary breakdown were observed in copper wire explosion, the prominent discrepancies of temperature and density among stratified vapor and plasma channel enlarged the inhomogeneity of particle size. The sufficient plasma process maintained the metal vapor at a relatively high temperature and enhance the coalescence process after nucleation in titanium explosion, and the median diameter of particles increased as a result. The core-corona structure happened in tungsten wire explosion led to special heating mechanism (heat transport and/or radiation instead of Joule heating) which may be responsible for the formation of large-size agglomerates. In order to produce high-quality nanoparticles, except suitable experimental conditions, it is necessary to achieve homogeneous explosions. The critical dynamics behaviors including ETI (stratification), breakdown mode (inner or surface), and coexistent multi-states products (melts/vapor/plasma) under low-density current which caused the inhomogeneity should be further considered and eliminated in nanoparticle production.