Characteristics and Diffusion of Electrical Explosion Plasma of Aluminum Wire in Argon Gas

Electrical explosion of aluminum wire is a very promising method for aluminum nanoparticle production. The exploding wire plasma has significant influence on the formation of the nanoparticles. In this paper, the electron temperatures and the electron densities in the plasma are estimated through Boltzmann plot and Stark broadening effect. The aluminum particle densities, charge state distributions, and the energy relaxation in the plasma are estimated accordingly. The diffusion of the plasma into protective argon gas is studied through its spatial distribution. The electron temperatures of the electrical explosion of wire (EEW) plasma with an aluminum wire in argon gas are 1~2 eV, and the electron densities are of the order of magnitude ~1019/cm3, which decrease rapidly over time after the EEW occurs. The diffusion of the EEW plasma of aluminum wire into ambient argon gas can be divided into two main phases, namely, the previous fast diffusion phase and the subsequent slow diffusion phase. The plasma is with quite different diffusion features due to the differences of the corresponding relative number density of the plasma to argon gas. For plasma with relative density much higher than 1, the diffusion velocity in the fast diffusion phase is significantly higher than that with relative density near 1, and in the slow diffusion phase, the distribution radius of the plasma can continue to increase significantly due to the considerable energy coupled from the circuit to the aluminum particles. Dependence of the plasma radii on the deposited energies are derived from the experimental data. For plasma with relative density near 1, due to the much longer relaxation time during the slow diffusion phase, very little energy can be transferred from the circuit to the aluminum particles and the plasma radii only increase slightly during this phase after the aluminum particles spent most of their kinetic energy in the previous fast diffusion phase.