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Abstract. Partially polycondensed y-aminopropylsilanetriol (APSTOL) was prepared by hydrolyzing y-aminopropyltriethoxysilane at a hydrolysis ratio 8.0. APSTOL contains up to 52% SiO2 and can be easily dissolved in water, forming clear solutions remaining stable practically at any pH value. The thermal evolution of APSTOL when heating up to 1000~ was examined using TGA and FTIR techniques; the probable mechanism of the oxidative decomposition of organic groups, with the formation of imino-and carboxyl-containing intermediates, has been discussed. Two magnesium silicates of the enstatite and forsterite compositions and two calcium silicates of the wollastonite and rankinite compositions have been prepared, using corresponding acetates and APSTOL as MUo and SiO2 precursors. The crystallization processes in these systems were studied by TGA and XRD techniques, after heat treatments up to 1000~ In all the systems, except rankinite, the parent silicates were found as the main crystalline phases.

Partially polycondensed y -aminopropylsilanetriol (APSTOL) was used as the silica precursor to prepare magnesium orthosilicate in the form of crystalline forsterite. Aqueous solutions of APSTOL and magnesium acetate were mixed and dried forming a water-soluble product that was converted into forsterite by heating to 1,OOO"C. The thermal evolution of the system was studied using TGA, FTIR, W -I / I S spectrophotomety, and XRD techniques, especially for the acetate decompsition and transformation of CSi03 -tetrahedra into the orthosilicate anions, The combustion of organics and the crystallization of forsterite proceed at temperatures 350 and S70°C, respectiuely. At intermediate temperatures, the system contains amorphous silicates with oligomeric and polymeric anions, which gradually depolymerize as temperature increases. The resulting crystalline product contains less impurities bericlase and enstatitel than samples prepared using other wet-chemistry techniques.

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