Numerical investigation on nanoparticle formation and influence on size distribution in wire explosion process

Abstract

Wire explosion technique has been widely studied in recent years to produce nanoparticles of different materials due to the enormous outstanding characteristics of nanomaterials as well as the advantages of wire explosion technique1. In the wire explosion process for preparation of nanoparticles, the wire firstly melts, vaporizes and then generates a mixture of metal vapor and liquid droplets. The voltage reaches a peak amplitude and the current quickly drops because only a small amount of metal vapor ionizes at this moment. Then the metal vapor gets cooled down and starts the following growing process of nanoparticles. In this paper, following simulation is carried out with wire material of aluminum. In the first stage, the generation process of vapor particles is modeled and the relationship between the explosion temperature, resistive deposited energy, the size of the vapor particles and the parameters of the explosion is derived and compared with experimental data. We find the resistive deposited energy is below the ionization one and the size of the vapor particles at the moment of explosion increases as the explosion temperature and deposited energy increases. Base on the results of the first stage, the growing process of the metal vapor to nanoparticles is simulated by adopting nodal treatment. The three main growing process, including homogeneous nucleation, surface growth and coagulation, are investigated to predict the size distribution of nanoparticles. It shows that nuclei of small size are formed during nucleation process. The decrease of number density of vapor particles demonstrates that condensation plays a more significant role than evaporation in surface growth process. The size distributions of nanoparticles at different temperatures also demonstrate that the growing process of nanoparticles tends to be inactive when temperature becomes relatively low. The final size distribution of nanoparticles is compared with experimental data as well2.