Control of Wettability Using Flame Generated Multicomponent Nanoparticle Coatings

Control of wettability of surfaces has been a hot research topic for years. Developing superhydrophobic and superhydrophilic surfaces are originally inspired by nature. Most common way to control the wettability of a surface is to produce functional nanocoatings on different substrates. In this work, aerosol synthesis method Liquid Flame Spray (LFS) was used for fabricating functional nanocoatings on paperboard, wood and glass substrates. Superhydrophobic and superhydrophilic nanocoatings have been previously produced by LFS method, but in this work the structure of the nanocoating was researched more closely to gain better understanding of the stability of the coating. Furthermore, minimum amount of coating for wettability modification was determined. Wettability of a surface was significantly changed even if the surface was only partly covered with nanoparticles.

Stability and wear resistance of functional nanocoatings is generally quite poor, so this was one of the research topics of this work. Stability of a coating depends on the adhesion and cohesion of the coating. Adhesion describes the interaction between a coating and a substrate and cohesion describes particle-to-particle interactions in the coating layer. This work focused on improving the cohesion of the nanocoatings by modifying the material composition of produced nanoparticles. Previously superhydrophobic TiO2 nanocoatings have been fabricated by LFS, but in this work TiO2 nanocoating was doped with SiO2, to improve the cohesion between agglomerated nanoparticles. Cohesion was successfully improved without losing the desired porosity or wetting properties.

LFS method was also combined with other coating methods. By combining LFS with other coating methods, superamphiphobic behavior was achieved, meaning that nanocoated surface repelled also other liquids than water. Nanoparticle layer formed optimal, porous layer on a surface and nanoparticle layer was afterwards modified by plasma treatment or chemical vapor deposition to obtain needed chemical composition of the coating. By combining different coating methods, excellent repellency for water, olive oil, ethylene glycol (EG), diiodomethane (DIM) and n-Hexadecane was observed. Stability of multicomponent coatings was tested with thousands of water droplets and coating remained unharmed. This indicates relatively good adhesion and cohesion of the multicomponent coatings.