Alumina-silica composite coatings on graphite by CVD at 550°C |
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Authors: | Zhaofeng Chen Min Li Yikai Shi |
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Affiliation: | (1) College of Material Science and Technology, Nanjing University of Aeronautics & Astronautics, 210016 Nanjing, P.R. China;(2) College of Mechanical and Electrical, Northwestem Polytechnical University, 710072 Xi’an, P.R. China |
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Abstract: | Alumina-silica composite coatings were prepared on the surface of graphite paper by chemical vapor deposition using AlCl3/SiCl4/H2/CO2 as precursor in the temperature range of 300 to 550°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were
used to examine the phase composition and the microstructure of the coating, respectively. The results indicated that a dense,
uniform, and adherent alumina-silica composite coating can be prepared on graphite paper substrate by chemical vapor deposition
at 550°C. Alumina-silica composite coating is composed of particles or nodules of varying size. Each particle is often composed
of a number of finer particles. The phases of the 550°C composite coating include γ-alumina and amorphous silica. The elemental
chlorine content in the composite coating decreases with increasing deposition temperature. The surfaces of the alumina-silica
composite coatings are affected by deposition temperature. There are some obvious micro-cracks in the 300°C composite coating,
which are attributed to a mismatch of the coefficient of thermal expansion between composite coating and graphite paper. The
550°C alumina-silica composite coating can be completely turned into mullite after heat-treatment at 1350°C for 0.5 hr in
argon atmosphere. |
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Keywords: | Alumina-silica composite coatings graphite paper chemical vapor deposition mullitization |
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