Structural and hydrophobic–hydrophilic properties of nanosilica/zirconia alone and with adsorbed PDMS

Two nanosilica A-300/zirconia (SZ) composites at zirconia content image and 20 wt.% were synthesized using a wet impregnation method with zirconium acetylacetonate as a precursor. The specific surface area of SZ is larger than that of A-300 because zirconia is composed of nanoparticles (crystallites of 4 nm in average size at image smaller than those of the initial silica (dav ≈ 11 nm). A-300 and SZ modified by polydimethylsiloxane (PDMS at molecular weight 1700 and 7960) in amounts of 5, 10, 15, 20 and 40 wt.% remained in the powder state with aggregates of primary particles smaller than those of A-300. SZ is more hydrophilic than silica but PDMS/SZ is more hydrophobic (maximum hydrophobic at CPDMS 15–20 or 40 wt.%) than PDMS/A-300.