SURFACE MODIFICATION OF SILICA-GELS WITH AMINOORGANOSILANES

The surface modification reaction of silica gel with aminoorganosilane s proceeds in two steps. For both the reaction step and the curing ste p, the chemical and physical interactions of the silane molecules with the silica surface have been modelled. From ethanol leaching tests, t he reaction phase interaction, in dry conditions, may be characterized as 22% proton transfer, 10% hydrogen bonding and 68% siloxane bonding . The deposition of the aminosilane molecules is governed by the speci fic surface area and surface hydration. For the bifunctional beta-amin oethyl-gamma-aminopropyltrimethoxysilane, a two-step deposition is obs erved. The rate of siloxane bonding in the curing phase is limited by the number of alkoxy groups, and results in a turnover of the aminosil ane molecules. A new application of aminosilane-modified silica gel is developed in converting the aminosilane layer to SiC. Thus, the liqui d phase path of the chemical surface coating process, for the controll ed synthesis of advanced ceramics, is set up.