Thin hydrophobic polymer films produced by radio frequency (rf) plasma decomposition of hexamethyldisiloxane (HMDSO) have becn produced on flat metal (titanium, stainless steel, and copperhickel) and silicon substrates. By using a statistical design methodology, the deposition conditions have been assessed for their control of the deposition rate, refractive index, water droplet contact angle, and longevity of dropwise condensation of steam. The films showing the best performance were those deposited at the slower rates, using low rf power density and high monomer flow rates, and having the lower refractive indices. There is some dependence on substrate material, with CuNi behaving worst, and titanium providing the best results of the three metals studied. This may be connected with the stability of an interfacial oxide layer. The steam immersion tests have already exceeded 7500 hours of continuous condensation, and many of the films arc still producing excellent dropwise condensation. The reasons for these effects of preparation conditions and substrate material on performance are discussed with reference to the plasma chemical process.

No abstract

Thin-films have been deposited onto silicon and metal substrates by plasma polymerization of vinyltrimethylsilane (VTMS), to provide hydrophobic coatings for dropwise condensation of steam. The deposition conditions have been sampled by a set of statistically designed experiments, and the films' thicknesses, water droplet contact angles, elemental compositions (by XPS), and ±CH x contents have been measured. There is a strong correlation between these film properties and their deposition conditions. The films that continue to provide successful long-term dropwise condensation had been deposited at a low rate onto heated substrates, such that they have high water contact angle and high ±CH x content. This required a plasma that provided a low electron energy input per precursor species collision.

Thin-films have been deposited onto silicon and metal substrates by plasma polymerization of vinyltrimethylsilane (VTMS), to provide hydrophobic coatings for dropwise condensation of steam. The deposition conditions have been sampled by a set of statistically designed experiments, and the films' thicknesses, water droplet contact angles, elemental compositions (by XPS), and ±CH x contents have been measured. There is a strong correlation between these film properties and their deposition conditions. The films that continue to provide successful long-term dropwise condensation had been deposited at a low rate onto heated substrates, such that they have high water contact angle and high ±CH x content. This required a plasma that provided a low electron energy input per precursor species collision.

No abstract