Hydrophobic silica films derived from methyltriethoxysilane (MTES): Effect of pH and calcination temperature

In this study, hydrophobic silica layers were synthesized through the sol–gel method derived from the silica precursor, methyltriethoxysilane (MTES), at various pH and calcination temperatures. Coating silica on ceramic plates significantly increases the surface hydrophobicity of the ceramic plates. The increment in hydrophobicity comes from the surface roughness and the hydrophobic group –CH3 derived from MTES. Increasing pH causes the hydrophobicity of the silica film to escalate. In the MTES silica film calcined at 350 °C, a change in pH from 1.97 to 9.66 enhanced the water contact angle from 92° to 120°, while increasing the calcination temperature decreased surface hydrophobicity. MTES silica film can maintain hydrophobic properties up to 420 °C. Mid pH (approx. 4.66) yields the silica material with the highest thermal stability. Gas sorption analysis shows that the resulting material has low porosity, surface area, and pore volume.