A low cost and facile preparation of hydrophobic silica films and powders by a solution-based process

Abstract

Super-hydrophobic surfaces with water contact angle (WCA) higher than 150° generated a lot of interests both in academic and in industry because of their self-cleaning functionality. Emphasis was given to the effect of pH value on the hydrophobic behavior of the obtained films or powders. At first, SiO₂ sols were prepared by diluted ammonia. We found that following the increase of pH value of sol from 8 to 9, WCAs of the obtained films increased from 121.8° to 131.8°. Following the continued increase of the pH value of sol, precipitates began to appear and smooth film could not be obtained. The WCAs of the obtained powders could reach 121.7°, and through modifying by TMCS could further increase to as high as 165° and the water sliding angle (WSA) was 2°. The results of SEM indicate that the hydrophobic properties of the powders without modifying by TMCS should be originated from the formation of nano/micron binary structure, i e, a micron-scale diameter and a nano-scale surface roughness. In this work we provide a better solution to fabricate super-hydrophobic silica coating surface with a simple method at low cost.

Keywords

sol-gel process / TMCS / super-hydrophobic / powders / nano/micron / agglomerates

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