The acceleration of charged nano-particles in gas stream of supersonic de-Laval-type nozzle coupled with static electric field

This paper presents a numerical analysis of an innovative method for nano-scale particle deposition, called Electrostatic-force-assisted cold gas dynamic spray (ECGDS). The transport characteristics of nano-scale charged particles in supersonic gas stream coupled with electrostatic field are simulated. Outside the nozzle, there exists bow shock near the substrate, which causes steep pressure increase across the shock. When the gas flow penetrates the bow shock and approaches to the substrate, the carrier gas speed decreases to nearly zero. In this study, electrostatic force is used to assist the charged particle to achieve high velocity upon impact of the substrate. The effect of electrostatic field to the velocity distribution of charged particles is investigated. It is found that smaller particles have the higher impact velocities on substrate. The higher particle charge densities can lead to higher particle impact velocities; and the closer the particles approach to the substrate, the stronger the electrostatic forces act on particles. For nano-scale particles the particle density (i.e. different materials) almost has no influence on the velocity profile.