Abstract:
Organic hydrophobic layers targeting sustained dropwise condensation are highly desirable but suffer from poor
chemical and mechanical stability, combined with low thermal conductivity. The requirement of such layers to remain ultrathin to
minimize their inherent thermal resistance competes against durability considerations. Here, we investigate the long-term durability
and enhanced heat-transfer performance of perfluorodecanethiol (PFDT) coatings compared to alternative organic coatings, namely,
perfluorodecyltriethoxysilane (PFDTS) and perfluorodecyl acrylate (PFDA), the latter fabricated with initiated chemical vapor
deposition (iCVD), in condensation heat transfer and under the challenging operating conditions of intense flow (up to 9 m s
−1
) of
superheated steam (111 °C) at high pressures (1.42 bar). We find that the thiol coating clearly outperforms the silane coating in
terms of both heat transfer and durability. In addition, despite being only a monolayer, it clearly also outperforms the iCVDfabricated PFDA coating in terms of durability. Remarkably, the thiol layer exhibited dropwise condensation for at least 63 h (>2×
times more than the PFDA coating, which survived for 30 h), without any visible deterioration, showcasing its hydrolytic stability.
The cost of thiol functionalization per area was also the lowest as compared to all of the other surface hydrophobic treatments used
in this study, thus making it the most efficient option for practical applications on copper substrates.
