Effect of Electric Field on Growth Kinetics, Morphology and Wettability of Flame-Deposited Carbon Nanoparticle Coatings

Carbon-based films are widely used in technologies requiring surfaces with controlled wettability. These films can be synthesized by depositing carbon nanoparticles (CNPs) onto substrates intermittently inserted into rich premixed flames, where thermophoresis drives particle capture. Depending on flame conditions, this method yields either hydrophilic films (from incipient sooting flames) or superhydrophobic films (from fully sooting flames). However, under incipient sooting conditions, the low concentration and small size of CNPs result in slow deposition, limiting practical applications. This study explores Electric Field-Assisted Thermophoretic Flame Synthesis (E-ThFS) as a strategy to enhance deposition. Rich ethylene/air flames are used, and the effect of an external electric field is investigated. UV–vis spectroscopy, profilometry, and contact angle measurements show that applying a −3 kV electric field accelerates deposition up to fivefold and alters surface morphology, producing more heterogeneous textures. The hydrophilic character of films from incipient sooting flames is preserved, although it may be preceded by a brief metastable superhydrophobic state whose duration decreases as voltage increases. In fully sooting flames, the electric field similarly enhances deposition and roughness while maintaining superhydrophobicity. These findings demonstrate the potential of E-ThFS as a scalable, one-step method for creating carbon coatings with tunable wettability and morphology.