Availableonlineatwww.sciencedirect.com Science Direct E噩≈RS ELSEVIER Joumal of the European Ceramic Society 28(2008)1687-1696 www.elsevier.com/locate/jeurceramsoc Microstructural features of the zro interfacial coatings on sic fibers before and after exposition to air at high temperatures N I. Baklanova,, O I Kiselyova, A.T. Titov, T M. Zima a Institute of Solid State Chemistry and Mechanochemistry SB RAS, Kutateladze Street 18. Novosibirsk 630128. Russian Federation b Lomonosov Moscow State University, Physical Department, Moscow, Russian Federation General Institute of Geology Geophysics and Mineralogy SB RAS, Novosibirsk 630090, Russian Federation Received 30 October 2007: received in revised form 27 November 2007; accepted 30 November 2007 Available online 14 January 2008 Sols of rare earth stabilized zirconia were used as simple, readily processable and accurate controllable precursors for the tetragonal zirconia interfacial coatings on commercially available Sic-based fibers. The tetragonal zirconia interfacial coatings can be applied to different types of Sic fibers without degrading fiber strength. The morphology, composition, structure, nanorelief and oxidation resistance of coated SiC fibers were evaluated by various analytical techniques, including scanning electron microscopy/energy dispersive analysis, transmission electron microscopy, atomic force microscopy in various modes, and micro-Raman spectroscopy. It was shown that the microstructural peculiarities of the RezrO2 interfacial coatings on Sic-based fibers may explain some of the differences in the behavior of different types of fibers o 2007 Elsevier Ltd. All rights reserved. Keywords: Interfacial coatings; Microstructure; ZrO2; SiC fibers: Oxidation resistance 1. Introduction ponent of composites it remains one of the weakest links in the research of the matrix-interphase-fiber triad. Insufficient nterface is a key region determining a set of properties of comprehension of interphase functions, role and nature, is a composite materials. In fiber-reinforced composites the fibers key problem and one major bottleneck retarding the devel ensure the strength of material, while the matrix helps to keep opment of efficient CMC's for high-temperature structural the shape. The interface transfers the load from matrix to applications. To solve this problem it is necessary to study the fibers. Further, the incorporation of the reinforcing fibers thoroughly the properties of interphase and to clarify which into brittle ceramic matrix provides CMCs with a degree characteristics of the interphase and in what extent control the of pseudo-ductility, preventing catastrophic failure by several behavior of the composite. Undoubtedly, among the features echanisms, such as fiber debonding, fiber sliding and crack of the interphase zone a microstructure is one of the most bridging. In order to achieve these properties, the interphase important zone must be sufficiently weak to deflect matrix microc- In addition to above-mentioned functions (load transfer racks and allow subsequent fiber pull-out. Both functions of and crack deflection), interphase materials must be compat the interphase zone in CMCs, namely, a load transfer from ible with both matrix and fiber for long-term operation in matrix to the fibers and the matrix microcrack deflection, are oxidizing atmosphere. This is especially important for non- greatly determined by nature of the interphase zone. Despite oxide CMCs, e.g. SiC/SiC composites. The interphase can of the wide recognition of the interphase as a crucial com- be exposed to oxidizing environments when the ends of coated fibers are exposed to surrounding atmosphere or when matrix cracks are present, allowing oxidants to reach the fiber Corresponding author. Tel: +7 3832 363839: fax: +7 3832 322847 coatings. Since oxide ceramics cannot be oxidized, it is com- E-mail address: baklanova@solid nsc. ru(N 1. Baklanova) monly believed that oxide-based coatings represent the best 0955-2219/S-see front matter o 2007 Elsevier Ltd. All rights reserved. doi: 10.1016/j-jeurceramsoc20071 1.008Available online at www.sciencedirect.com Journal of the European Ceramic Society 28 (2008) 1687–1696 Microstructural features of the ZrO2 interfacial coatings on SiC fibers before and after exposition to air at high temperatures N.I. Baklanova a,∗, O.I. Kiselyova b, A.T. Titov c, T.M. Zima a a Institute of Solid State Chemistry and Mechanochemistry SB RAS, Kutateladze Street 18, Novosibirsk 630128, Russian Federation b Lomonosov Moscow State University, Physical Department, Moscow, Russian Federation c General Institute of Geology, Geophysics and Mineralogy SB RAS, Novosibirsk 630090, Russian Federation Received 30 October 2007; received in revised form 27 November 2007; accepted 30 November 2007 Available online 14 January 2008 Abstract Sols of rare earth stabilized zirconia were used as simple, readily processable and accurate controllable precursors for the tetragonal zirconia interfacial coatings on commercially available SiC-based fibers. The tetragonal zirconia interfacial coatings can be applied to different types of SiC fibers without degrading fiber strength. The morphology, composition, structure, nanorelief and oxidation resistance of coated SiC fibers were evaluated by various analytical techniques, including scanning electron microscopy/energy dispersive analysis, transmission electron microscopy, atomic force microscopy in various modes, and micro-Raman spectroscopy. It was shown that the microstructural peculiarities of the ReZrO2 interfacial coatings on SiC-based fibers may explain some of the differences in the behavior of different types of fibers. © 2007 Elsevier Ltd. All rights reserved. Keywords: Interfacial coatings; Microstructure; ZrO2; SiC fibers; Oxidation resistance 1. Introduction Interface is a key region determining a set of properties of composite materials. In fiber-reinforced composites the fibers ensure the strength of material, while the matrix helps to keep the shape. The interface transfers the load from matrix to the fibers. Further, the incorporation of the reinforcing fibers into brittle ceramic matrix provides CMC’s with a degree of pseudo-ductility, preventing catastrophic failure by several mechanisms, such as fiber debonding, fiber sliding and crack bridging.1 In order to achieve these properties, the interphase zone must be sufficiently weak to deflect matrix microc￾racks and allow subsequent fiber pull-out. Both functions of the interphase zone in CMC’s, namely, a load transfer from matrix to the fibers and the matrix microcrack deflection, are greatly determined by nature of the interphase zone. Despite of the wide recognition of the interphase as a crucial com- ∗ Corresponding author. Tel.: +7 3832 363839; fax: +7 3832 322847. E-mail address: baklanova@solid.nsc.ru (N.I. Baklanova). ponent of composites it remains one of the weakest links in the research of the matrix–interphase–fiber triad. Insufficient comprehension of interphase functions, role and nature, is a key problem and one major bottleneck retarding the devel￾opment of efficient CMC’s for high-temperature structural applications. To solve this problem it is necessary to study thoroughly the properties of interphase and to clarify which characteristics of the interphase and in what extent control the behavior of the composite. Undoubtedly, among the features of the interphase zone a microstructure is one of the most important. In addition to above-mentioned functions (load transfer and crack deflection), interphase materials must be compat￾ible with both matrix and fiber for long-term operation in oxidizing atmosphere. This is especially important for non￾oxide CMC’s, e.g. SiC/SiC composites. The interphase can be exposed to oxidizing environments when the ends of coated fibers are exposed to surrounding atmosphere or when matrix cracks are present, allowing oxidants to reach the fiber coatings. Since oxide ceramics cannot be oxidized, it is com￾monly believed that oxide-based coatings represent the best 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.11.008