Surface modification of silica gels with aminoorganosilanes

The surface modification reaction of silica gel with aminoorganosilanes proceeds in two steps. For both the reaction step and the curing step, the chemical and physical interactions of the silane molecules with the silica surface have been modelled. From ethanol leaching tests, the 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 specific surface area and surface hydration. For the bifunctional N-beta-aminoethyl-gamma-aminopropyltrimethoxysilane, a two-step deposition is observed. The rate of siloxane bonding in the curing phase is limited by the number of alkoxy groups, and results in a turnover of the aminosilane molecules. A new application of aminosilane-modified silica gel is developed in converting the aminosilane layer to SiC. Thus, the liquid phase path of the chemical surface coating process, for the controlled synthesis of advanced ceramics, is set up