Atomic layer deposited titanium dioxide coatings on KD-II silicon carbide fibers and their characterization

Graphical abstract: - Highlights: • Atomic layer deposition (ALD) is suitable to prepare TiO₂ coatings on SiC fibers. • The ALD TiO₂ coatings are uniform, smooth, dense, and conformal. • The ALD TiO₂ coatings are amorphous regardless of the coating thickness. • The ALD TiO₂ coatings exhibit good oxidation resistance for protecting the substrate fibers. - Abstract: To provide oxidation protection and/or to act as an interfacial coating, titanium oxide (TiO₂) coatings were deposited on KD-II SiC fibers by employing atomic layer deposition (ALD) technique with tetrakis(dimethylamido)titanium (TDMAT) and water (H₂O) as precursors. The average deposition rate was about 0.08 nm per cycle, and the prepared coatings were smooth, uniform and conformal, shielding the fibers entirely. The as-deposited coatings were amorphous regardless of the coating thickness, and changed to anatase and rutile crystal phase after annealing at 600 °C and 1000 °C, respectively. The oxidation measurement suggests that the TiO₂ coating enhanced the oxidation resistance of SiC fibers obviously. SiC fibers coated with a 70-nm-thick TiO₂ layer retained a relatively high tensile strength of 1.66 GPa even after exposition to air at 1400 °C for 1 h, and thick silica layer was not observed. In contrast, uncoated SiC fibers were oxidized dramatically through the same oxidation treatment, covered with a macro-cracked thick silica film, and the tensile strength was not measurable due to interfilament adhesion. The above results indicate that TiO₂ films deposited by ALD are a promising oxidation resistance coating for SiC fibers.