Effect of temperature on the growth of boron nitride interfacial coatings on SiC fibers by chemical vapor infiltration |
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| Affiliation: | 1. Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi''an, 710072, PR China;2. Key Laboratory for Advanced Corrosion and Protection of Aviation Materials, AECC Beijing Institute of Aeronautical Materials, Beijing, 100095, PR China;1. School of Aeronautics and Astronautics, Central South University, Changsha, Hunan, 410083, China;2. Hunan Key Laboratory of Advanced Fibers and Composites, Central South University, Changsha, Hunan, 410083, China;3. School of Materials Science and Engineering, Central South University, Changsha, Hunan, 410083, China;4. Key Laborartory of Advanced Materials Technologies, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan, 610031, China;1. Shenzhen Key Laboratory for Advanced Materials and Department of Material Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, University Town, Shenzhen, Guangdong 518055, China;2. Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, National University of Defense Technology, Changsha, Hunan 410073, China |
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| Abstract: | In order to improve bonding property between SiC fibers and matrix of SiCf/SiC composites, boron nitride (BN) interfacial coatings were synthesized by chemical vapor infiltration. BN coatings were fabricated from BCl3–NH3 gaseous mixtures at four different temperatures (843 °C, 900 °C, 950 °C and 1050 °C) with different deposition times. Growth kinetics, nucleation and growth processes, microstructure and chemical composition of boron nitride coatings were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectrometry. Results showed that deposition rate increased as the temperature increased from 843 °C to 950 °C. However, deposition rate decreased slightly from 23.10 ± 0.85 nm/min (950 °C) to 21.39 ± 0.67 nm/min when the temperature was increased further to 1050 °C. It could be due to the nucleation occurring in the gas and the consumption of a large amount of BCl3 and NH3. When deposition temperature was 843 °C, BN grains deposited on top layer of the coating could not completely cross Ehrlich-Schwoebel barrier and grew in island growth mode. On the other hand, the deposition pattern followed a layer-by-layer growth mode when deposition temperature was 1050 °C. Deposition temperature significantly affected the microstructure of as-deposited BN coatings. At 843 °C, 950 °C and 1050 °C, the coatings presented amorphous, polycrystalline and hexagonal structures, respectively. |
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| Keywords: | Hexagonal boron nitride SiC fibers Chemical vapor infiltration Growth kinetics Growth mode |
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