National Research Tomsk State University, Tomsk, Russia:

E. S. Lyutova, Associate Professor at the Department of Inorganic Chemistry, Faculty of Chemistry, Candidate of Technical Sciences, e-mail: lyutova.tsu@mail.ru
L. P. Borilo, Professor at the Department of Inorganic Chemistry, Faculty of Chemistry, Doctor of Technical Sciences

This paper examines bioactive thin-film composites synthesized on the basis of the SiO₂ – P₂O₅ – СаO – TiO₂ system from alcohol solutions by sol-gel method. The film was produced at the sol stage by pulling from the film-forming solution on the oxide surface of titanium (BT1-0 grade of commercially pure titanium with oxide coating). Uniform films on titanium with oxide coating can be obtained on day 5 after an alcohol solution has been prepared on the basis of orthophosphoric acid, tetrabutoxytitanium, tetraethoxysilane, calcium nitrate. A comprehensive study has been conducted that looks at the effect of film coating on the properties of bioactive thin-film SiO₂ – P₂O₅ – СаO – TiO₂-base composites produced with oxide-coated titanium used as a substrate. The following stages have been identified of how the composites get formed. Stage 1: up to 400 ^oC — water is removed; Stage 2: from 400 to 600 ^oC – alcohol burns off, nitrates decompose and the products of the thermal oxidative breakdown of ethoxy groups burn off; Stage 3: from 600 to 1,000 ^oC – the sample crystallizes. The samples were found to remain amorphous at 600 ^oC and a temperature increase up to 800 ^oC was needed. The samples that were annealed at 800 ^oC had a crystalline structure. The following phases were produced: CaSiO₃, TiO₂ anatase, TiO₂, Ca₃(PO₄)₂, Ca₅(PO₄)_2.85(SiO₄)_0.15O. The following heat treatment conditions have been identified that would be applicable to the samples: drying at 60 ^oC, annealing at 800 ^oC for 1 hour. Lewis basic centers (Ti/Si – O) dominate the surface of the synthesized composites. Production of a film on the oxide-coated titanium results in a more distinguished topography and an increase of the critical load up to 2.28 N. The studied composites are capable of forming an apatite-like surface layer. The formation rate is higher on oxide-coated titanium with a film than on oxide-coated titanium without one. The synthesized composites can be recommended for further study of biological properties.
Support for this research was provided under the Tomsk State University Development Programme Priority-2030.

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