Synthesis of Preceramic Organomagnesium Oxanealumoxane Siloxanes

Abstract

Organomagnesiumoxane alumoxane siloxane oligomers with different Al:Mg and Al:Si molar ratio have been synthesized through ethylacetoacetate alkoxyhydroxyalumoxane oligomers co-condensation with magnesium acetylacetonate and oligoethoxysiloxanes in organic solvents (alcohol, toluene) at a temperature of 70-100 °С within 3-6 h with the following solvent distillation. The physicochemical properties of the synthesized oligomers were studied. It is shown that with a molar ratio of Al:Mg ≈ 2 and Al:Si ≈ 1, oligomers have fiber-forming properties. The process of thermotransformation of organomagnesiumoxane alumoxane siloxanes into ceramic phases is investigated. It is found that pyrolysis results in the formation of multicomponent ceramics based on magnesium, aluminum, and silicon oxides, in particular, ceramics with a composition close to that of cordierite 2MgO·2Al2O3·5SiO2 (Mg2Al4Si5O18) or a mixed composition: magnesium-aluminum spinel and mullite. Therefore, the synthesized organomagnesiumoxane alumoxane siloxanes are preceramic oligomers and can be used as precursors for the preparation of various components (binders, impregnating compositions, fibers, ceramic powders) of high-purity ceramic composites based on magnesium, aluminum and silicon oxides.