J. Phys. IV France 11 (2001) Pr3-877-Pr3-884
Fiber-coatings for fiber-reinforced mullite/mullite compositesK. Nubian1, G. Wahl1, B. Saruhan2 and H. Schneider2
1 Institut für Oberflächentechnik und Plasmatechnische Werkstoffentwicklung, Technische Universität Braunschweig, Bienroder Weg 53, 38108 Braunschweig, Germany
2 DLR, Deutsches Zentrum für Luft- und Raumfahrt e.v., 51147 Köln, Germany
Mullite-based fiber-reinforced composites are favorite candidates for the application in combustion chambers of gas turbines. The application requires damage tolerance, temperature and oxidation-resistance at high temperatures (> 1200°C) over long terms. In order to realize crack deflection and fiber pull-out, an interphase coating of the mullite fibers (NextelTM 720) is necessary to obtain a weak bonding between fibers and matrix. Two systems of interphases produced by CVD were described. The fist system is a carbon/metal-oxide double layer (C/ZrO2, C/Al2O3). Properties of the resulting composites after heat-treatment (1300 °C , 1000 h) under cyclic and continuous heating conditions were described.
The second system is the codeposition of La2O3 and Al2O3 on the fibers. After heat-treatment at 1300 °C lanthanum hexaluminate (LaAl11O18) with a magneto plumbite structure containing sliding planes should be formed.
© EDP Sciences 2001