SYNTHESIS AND CHARACTERIZATION OF MICROPOROUS SILICA-ALUMINA THIN FILMS
Abstract
Microporous silica-alumina thin films were prepared by a simple and robust sol-gel method. Tetraethoxysilane was mixed with an acidic alumina hydrosol. Urea was added for the preparation of the alumina hydrosol, for controlling the polycondensation of the mixed oxide network and also as porogen agent. Thin films were deposited by dip-coating on dense substrates.
IR and 27Al NMR spectroscopic analyses showed that for Si/Al molar ratios up to 6/1, a homogeneous mixed oxide is obtained with a random distribution of Al and Si atoms in the oxide lattice based on tetrahedral units. The deposited layers are crack-free as demonstrated by scanning electron microscopy (SEM) observations. Their microporosity was investigated using ellipsoporosimetry (EP) with films supported on flat substrates.
