Low temperature reliability of carbon nanotube/silicone superhydrophobic coatings

Abstract

Superhydrophobic coatings have been studied for various applications. Among those, icerepllent coating is one of the important fields in the studies. Superhyphobic surface is known to reduce accumulation of snow, ice, or frost. Antiice coating is important. When it spread over a surface, even a thin layer is enough to bring down power lines, burst pipes, make road impassible, and cause dangerous loss of lift force by aircraft wings. Accumulated ice is so sturdy that large-scale breaking is difficult. A rubber coat (called pneumatic boot) on plane surfaces designed to crack ice by inflating is no match for severe ice. Superhydrophobic materials were first tested by Saito et al. [1] and more recently by several other groups, and demonstrated promising antiicing performance. [2-8] Reduced ice adhesion was reported and the effect of wetting hysteresis on ice adhesion strength was stressed. Tourkine et al. [2] reported delayed water freezing on rough superhydrophobic surfaces, which is believed to be favorable for reduced ice accumulation, whereas Cao et al. [3] and Wang et al. [4] reported low ice accumulation on superhydrophobic surfaces exposed to natural outdoor “freezing rain” conditions. However, in many conditions, superhydrophobic coatings undergo thermal cycling from frozen condition to normal condition over 0 C. However, reliability of superhydrophobic coating has not been studied in the cycling conditions. Carbon nanotube based composite materials have been investigated for various applications to improve electrical, mechanical and thermal properties and superhydrophobic coating is one of them. In this study, we introduce CNT/silicone composite materials as a superhydrophobic coating. The CNT content in the composite was varied to investigate correlation between the microstructure of the composite and the characteristics of the superhydrophobic coatings and their reliabilities at low temperature. This study shows nano-porous structure of superhydrophobic coating is of great importance not only for superhydrophobic characteristics but also for mechanical reliability to relax the thermal stresses imposed on the interface of the coating/substrate.