Investigating the Suppression Mechanisms of Nucleate Boiling through Superhydrophobic Surface Coating

Nucleate boiling at high temperatures can lead to mechanical erosion and unstable heat transfer. Superhydrophobic coatings have been widely studied for controlling boiling behavior by regulating the Leidenfrost point, but the underlying mechanisms are still under discussion. In this work, thin and thick superhydrophobic coatings with thicknesses of 6.928 and 28.438 μm were fabricated on silicon substrates to study the effect of surface morphology on the Leidenfrost point. The thick coating exhibits a lower Leidenfrost point of 240 °C compared with 260 °C for the thin coating, corresponding to a reduction of 20 °C. This behavior is associated with increased surface roughness with Sa = 10.4 μm and the formation of creelure structures that promote vapor escape and weaken the stability of the vapor film. The suppression of nucleate boiling is attributed to three factors, including microcavities with sizes of 50 to 200 nm that are smaller than the theoretical nucleation threshold of 1.75 μm, high contact angles between 150 and 156° that reduce liquid-solid adhesion, and the combined effect of coating thickness and roughness that enhances pore connectivity and vapor dissipation. Overall, the study provides a controlled thickness-morphology comparison under identical surface chemistry and offers mechanism-oriented evidence to inform micro/nanoscale surface design for high-heat-flux thermal management.