Effect of Aluminium Sec-butoxide on Wetting Properties of Silica-Based Coatings on Glass

Many surface properties are more or less strongly controlled by the surface pattern, i.e., the micro or nanoscale morphologies. Silica-alumina mixed oxide coatings were prepared by simple sol-gel method using methyl trimethoxysilane (MTMS) and aluminium sec-butoxide (ASB) as precursors. To obtain good quality coatings the volume ratio of MeOH:MTMS:HNO3:H2O:NH4OH was optimized at 10:2.5:0.3:1:4 and the ASB:MTMS ratio (M) was varied from 0.25 to 1. The effect of M on surface roughness and thus on wetting behavior of the coatings was studied. For M = 0.25 and 1, the water contact angle was 95° and 104° while the same for M = 0.5 was 116°. The variation in water contact angle is supported by surface morphology and surface roughness. The presence of aluminium and silica cross linkage was detected by FT-IR and XRD patterns as well.