Physical powder deposition of solid lubricant nanoparticles by electrostatic spray coating (ESC)

Nanoparticles are essential building blocks for the bottom-up manufacturing of nanostructured porous and dense coatings, which have unique properties such as ultrahigh hardness, strength, and wear resistance. However, they are prone to cluster and tend to stick to the surfaces in physical contact in the deposition with nanoparticles as raw material(s). These tendencies impose major challenges to the delivery and coating of nanoparticles via traditional techniques. In this paper, a successful physical powder deposition technique, namely electrostatic spray coating (ESC, corona charging), is demonstrated for coating sub-micron and nanosized solid lubricant particles of MoS2 and ZnO on flat sample geometries. The paper further discusses the coating mechanism through the response of nanoparticles to the static electric field and carrier gas flow.