Journal
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
Volume 37, Issue 16, Pages 5177-5191Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jeurceramsoc.2017.04.034
Keywords
Silazane; Rare-earth silicates; Polymer-derived ceramic; Environmental barrier coating; Hot gas corrosion
Categories
Funding
- Alexander von Humboldt Foundation (AvH) within the Research Group Linkage Programme
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Environmental barrier coatings are required to protect Si3N4 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 Y2O3 or Yb2O3 powders and the oligosilazane Durazane 1800. After pyrolysis above 1200 degrees C in air, the silicates are predominant phases. The corrosion behaviour of the resulting composites was tested at 1400 degrees C for 80 h in moist environments. The material containing x(2)-Yb2SiO5 and Yb2Si2O7 undergoes the lowest corrosion rate (-1.8 mu g cm(-2) h(-1)). Finally, the processing of Y2O3/Durazane 1800 as well-adherent, crack-free and thick (40 mu m) coatings for Si3N4 was achieved after pyrolysis at 1400 degrees C in air. The coating consisted of an Y2O3/Y2SiO5 top-layer and an Y2O3/Y2Si2O7 interlayer due to the interaction of the coating system with the substrate. (C) 2017 Elsevier Ltd. All rights reserved.
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