| Sol-gel processing is used to prepare materials as diverse as catalyst supports, adsorbents, films, fibers, ceramics, and glasses. The advantage of the sol-gel processing is its ability to produce highly pure and homogeneous products at low temperatures. The microstructure of titania gels and surface fractality as well as chemistry of titania aerogels have been systematically investigated in this dissertation.; In Part I, various synthetic procedures were described and employed to synthesize polymeric and particulate titania gels. Titania aerogels were prepared via freeze and CO{dollar}sb2{dollar} supercritical drying.; Part II concerns the development of a novel sample preparation technique for studying titania gel microstructure prior to drying via conventional transmission electron microscopy. This new technique was employed to investigate the microstructure of several titania gels.; In Part III, the surface fractality of polymeric and particulate titania aerogels was studied by means of adsorption techniques. Three distinctly different methods, e.g., Avnir and Pfeifer's method, Frenkel-Halsey-Hill method, and the thermodynamic method, were employed to determine the surface fractality. The performances of these three methods were compared. It was found that the fractal surfaces of particulate aerogels are slightly more irregular than those of polymeric aerogels. In addition, the effects of solvent replacement in polymeric titania gels on the surfaces of resultant aerogels were investigated. Solvent replacement resulted in smoothing the surfaces of aerogels obtained from subsequent freeze drying.; In Part IV, the effects of catalyst, drying method, and solvent replacement on the chemistry of titania aerogels were analyzed qualitatively via photoacoustic infrared spectroscopy. The utility of photoacoustic technique for obtaining such information was clearly demonstrated.; Finally, the conclusions reached and recommendations for future work are presented in Part V. |
