Organochromiumoxane yttriumoxane alumoxane oligomers: synthesis, properties, pyrolysis
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 8, pp. 1492—1502, August, 2020
Organochromiumoxane yttriumoxane alumoxane oligomers: synthesis, properties, pyrolysis* G. I. Shcherbakova, N. B. Kutinova, M. S. Varfolomeev, A. I. Drachev, M. G. Kuznetsova, and P. A. Storozhenko State Research Institute for Chemistry and Technology of Organoelement Compounds, 38 prosp. Entuziastov, 105118 Moscow, Russian Federation. Fax: +7 (495) 673 4909. E-mail: [email protected], [email protected] Ceramic-forming organochromiumoxane yttriumoxane alumoxane oligomers with a given molar ratio of Al : Cr and Al : Y, hydrolytically stable in air, have been synthesized. The materials demonstrate fiber-forming properties. It is established that thermal treatment of the obtained oligomers leads to the formation of high purity, heat-resistant multicomponent ceramics based on aluminum, yttrium and chromium oxides, in particular, alumina and garnet fibers modified with chromium oxides. Key words: ceramic-forming organochromiumoxane yttriumoxane alumoxane oligomers, oxide ceramics, polymer and oxide fibers.
Ceramic-forming organoelementoxane aluminoxane oligomers having a given chemical composition and molecular structure are the most promising precursors for the components (fibers, binders, coatings, powders, etc.) required for the preparation of oxide-based ceramic composites.1,2 Multiphase oxide/oxide ceramic composites with increased resistance to oxidation and creep are in demand for work in extreme conditions.1—3 In this case, the oxide components used must be chemically compatible and should have sufficient heat resistance to prevent mechanical destruction. It is known4 that Y3Al5O12(YAG)— Al2O3 system is very promising for high-temperature applications. These two components are compatible because they have the same thermal expansion coefficients and close melting points (1940 and 2045 C for YAG and Al2O3, respectively). In addition, YAG maintains high creep resistance and bending strength up to 1400 C. Small additives of Cr2O3 reduce creep and increase the strength of this system due to the formation of Y3(Al1–xCrx)5О12.4 Ceramics of this composition are promising for use in solid-state lasers, as well as for the manufacture of inorganic luminescent materials and ceramic pigments.5—11 Results and Discussion We synthesized for the first time hydrolytically stable and soluble in organic solvents organochromiumoxane
* Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
yttriumoxane alumoxane oligomers.12 Thermal treatment of these oligomers leads to the formation of high purity high-temperature resistant multicomponent ceramics based on aluminum, yttrium, and chromium oxides. At a certain molar ratio of Al : Cr and Al : Y the oligomers also exhibit fiber-forming properties. Without a doubt, they are promising precursors for components of high-temperature, oxidation-resistant ceramic composites (fibers, binders, coatings, powders, etc.). Therefore, th
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