SYNTHESIS OF A POLYSILAZANE LAYER ON SILICA-GEL BY CHEMICAL SURFACE COATING

Thermally pretreated silica gel has been modified with SiCl4 and NH3. Repeating this treatment gives rise to a polysilazane layer, chemicall y bonded to the silica gel surface. Using FTIR, N and Cl determination s and gravimetric analysis, a total characterization of the polysilaza ne layer was obtained, together with quantification of the different r eactions occurring. The parameters of the reaction cycles have been op timized in such a way, that a high density of silazanes (=Si-NH-Si=) i s reached at the silica surface. The influence of the modification pro cess upon the porosity of the silica gel was also studied.