Structure of Chemical Vapor Deposition Titania/Silica Gel

✍ Scribed by R Leboda; V.M Gun'ko; M Marciniak; A.A Malygin; A.A Malkin; W Grzegorczyk; B.J Trznadel; E.M Pakhlov; E.F Voronin

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 570 KB
• Volume: 218
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1999.6411

✦ Synopsis

The structure of porous silica gel/titania synthesized using chemical vapor deposition (CVD) of titania via repeated reactions of TiCl 4 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 TiO 2 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.