Synthesis and characterization of yttrium and ytterbium silicates from their oxides and an oligosilazane by the PDC route for coating applications to protect Si3N4 in hot gas environments. Issue 16 (December 2017)

• Record Type: Journal Article
• Authors: Lenz Leite, Mateus; Barroso, Gilvan; Parchovianský, Milan; Galusek, Dušan; Ionescu, Emanuel; Krenkel, Walter; Motz, Günter
• Is Part Of: Journal of the European Ceramic Society. Volume 37:Issue 16(2017)
• Page Start: 5177
• Page End: 5191
• Publication Date: 2017-12
• Subjects: Silazane -- Rare-earth silicates -- Polymer-derived ceramic -- Environmental barrier coating -- Hot gas corrosion; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2017.04.034
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: Environmental barrier coatings are required to protect Si3 N4 against hot gas corrosion and enable its application in gas turbines, among which yttrium and ytterbium silicate-coatings stand out. Thus, the polymer-derived ceramic route was used to synthesize these silicates for basic investigations regarding their intrinsic properties from a mixture of Y2 O3 or Yb2 O3 powders and the oligosilazane Durazane 1800. After pyrolysis above 1200 °C in air, the silicates are predominant phases. The corrosion behaviour of the resulting composites was tested at 1400 °C for 80 h in moist environments. The material containing x2 -Yb2 SiO5 and Yb2 Si2 O7 undergoes the lowest corrosion rate (−1.8 μg cm −2 h −1 ). Finally, the processing of Y2 O3 /Durazane 1800 as well-adherent, crack-free and thick (40 μm) coatings for Si3 N4 was achieved after pyrolysis at 1400 °C in air. The coating consisted of an Y2 O3 /Y2 SiO5 top-layer and an Y2 O3 /Y2 Si2 O7 interlayer due to the interaction of the coating system with the substrate.