Composite powders with titania grafted onto modified fumed silica

A series of powder samples with partially silylated fumed silica A-380 (content of trimethylsilyl (TMS) groups CTMS = 0.09–0.79 mmol/g corresponding to the substitution degree of 9.6–84.0%) was modified by grafting of CVD-titania (titanium content CTi = 1.1–1.8 wt.%) (TiCl4 as a precursor). Pure fumed silicas A-380 and A-50 were also modified by grafted titania using Ti[OCH(CH3)2]4 (TTIP) as a precursor deposited from isopropyl alcohol, dried and then heated at 1073 K. Interaction of TTIP with A-380 was also studied in the presence of poly(vinyl pyrrolidone), PVP. Unmodified and modified silicas and titania/silicas were studied using adsorption, FTIR, NMR, AFM, TPD-MS, TG, and XRD methods. The size and the crystallinity of grafted titania particles depend on the type of matrix (A-380 and A-50), reaction conditions, presence of the TMS groups or adsorbed PVP, and subsequent treatment. In the case of A-380 with more strongly aggregated primary particles the size of titania particles is smaller and their crystallinity is much lower than that of titania deposits on A-50. Adsorption of water increases on CVD-TiO2/silylated silica in comparison with silylated silica at high CTMS values.