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Deposition of Hexagonal Boron Nitride from N-Trimethylborazine (TMB) for Continuous CVD Coating of SiBNC Fibers

Authors

  • Yaping Ye,

    1. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München (Germany)
    2. Fraunhofer Institut für Silicatforschung Neunerplatz 2, 97082 Würzburg (Germany)
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  • Uta Graupner,

    1. Police Hamburg LKA 33, Hamburg (Germany)
    2. Fraunhofer Institut für Silicatforschung Neunerplatz 2, 97082 Würzburg (Germany)
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  • Reinhard Krüger

    Corresponding author
    1. Department of Functional Materials in Medicine and Dentistry, Universitätsklinikum Würzburg Pleicherwall 2, D-97070 Würzburg (Germany)
    2. Fraunhofer Institut für Silicatforschung Neunerplatz 2, 97082 Würzburg (Germany)
    • Department of Functional Materials in Medicine and Dentistry, Universitätsklinikum Würzburg Pleicherwall 2, D-97070 Würzburg (Germany).
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  • This work was funded by the Federal Ministry of Education and Research under grant number 03 × 3514 B. Authors are indebted to the TEM work by Chun Wang. Further thank Anna Hilbig (Chair Chemische Technologie der Materialsynthese, Universität Würzburg) for her contribution regarding the CVD reactor setup and Sabine Stöckel (Physical Chemistry Technische Universität Chemnitz) for helpful discussions in a previous project.

Abstract

Bonding strength between fibers and matrices of ceramic matrix composites (CMCs) is of great importance for the fracture behavior and can be adjusted by appropriate fiber coatings. In this study, the continuous coating of SiBNC fibers with hexagonal boron nitride (h-BN) by CVD from TMB in an atmospheric pressure reactor is presented. Prior to fiber coating, the effects of deposition parameters, e.g., deposition temperature, concentration of the precursor and ammonia addition, and gas-flow rate are investigated on flat Si substrates, and the results are utilized for the fiber coating. Ammonia concentration has no influence on the deposition rate. A maximum deposition rate of 0.044 kg m−2 h−1 for static conditions and 0.040 kg m−2 h−1 for continuous conditions can be achieved, which is comparable to the literature. The depositions are characterized for their composition and structure. Smooth homogeneous coatings with a thickness of 180–250 nm are found on the fibers. High-resolution transmission electron microscopy (HRTEM) of the coated SiBNC fibers reveals that the hexagonal BN with 5 nm basal planes is mainly randomly oriented.

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