Structure of Chemical Vapor Deposition Titania/Silica Gel

• Published in: Journal of colloid and interface science Vol. 218; no. 1; pp. 23 - 39
• Main Authors: Leboda, R, Gun'ko, V.M, Marciniak, M, Malygin, A.A, Malkin, A.A, Grzegorczyk, W, Trznadel, B.J, Pakhlov, E.M, Voronin, E.F
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-10-1999
• Subjects: CHEMICAL VAPOR DEPOSITION; chemical vapor deposition titania; COMPOSITE MATERIALS; fractal dimensions; globular model; infrared; MATERIALS SCIENCE; MICROSTRUCTURE; MOLECULAR MODELS; nonuniform coverage; POROSITY; porosity parameters; SILICA GEL; theoretical modeling; TITANIUM OXIDES; theoretical modeling; globular model; infrared; silica gel; chemical vapor deposition titania; nonuniform coverage; porosity parameters; fractal dimensions
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1999.6411

The structure of porous silica gel/titania synthesized using chemical vapor deposition (CVD) of titania via repeated reactions of TiCl4 with the surface and subsequent hydrolysis of residual Ti–Cl bonds at different temperatures was investigated by means of low-temperature nitrogen adsorption–desorption, X-ray diffraction (XRD), IR spectroscopy, and theoretical methods. A globular model of porous solids with corpuscular structure was applied to estimate the porosity parameters of titania/silica gel adsorbents. The utilization of this model is useful, for example, to predict conditions for synthesis of titania/silica with a specified structure. Analysis of pore parameters and fractal dimension suggests that the porosity and fractality of samples decrease with increasing amount of TiO2 covering the silica gel surface in a nonuniform layer, which represents small particles embedded in pores and larger particles formed at the outer surface of silica globules. Theoretical simulation shows that the Si–O–Ti linkages between the cover and the substrate can be easily hydrolyzed, which is in agreement with the IR data corresponding to the absence of a band at 950 cm−1 (characteristic of Si–O–Ti bridges) independent of the concentration of CVD-titania.