Oxidation protection of graphite materials by single-phase ultra-high temperature boride modified monolayer Si-SiC coating |
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Authors: | Yan Jiang Quanxing Ren Hongqiang Ru Zhiliang Mao Haibin Xu |
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Affiliation: | 1. Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, Liaoning 110819, China;2. Institute of Ceramics and Powder Metallurgy, School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning 110819, China |
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Abstract: | To improve the oxidation resistance of Si-SiC coating, single-phase ultra-high temperature boride (ZrB2 or TaB2) modified Si-SiC coating was designed and established on graphite substrates by combination of dipping and reactive infiltration process. ZrB2 or TaB2 phase was introduced in Si-SiC coating by directly mixing raw materials and phenol formaldehyde resin in the slurry, and then the ZrB2-SiC-Si and TaB2-SiC-Si coatings were fabricated on the graphite samples by dipping-curing, pyrolysis, and siliconizing. The crystalline phases and microstructure of the as-obtained multiphase coatings were investigated by X-ray diffraction analysis and scanning electron microscopy. The interrupted oxidation tests from room-temperature to 1500?°C were conducted to assess the anti-oxidation property of the prepared coatings. After 1200?h of oxidation at 1500?°C in air (30 times thermal cycles), the mass losses of the graphite substrates coated with ZrB2-SiC-Si and TaB2-SiC-Si coatings were 0.086% and 0.537%, respectively, and the high-temperature stability of the modified coatings was greatly improved compared to the Si-SiC coating. The excellent anti-oxidation performances of the compound coatings were attributed to the compact structure of the coatings and the formation of compound oxide layers covering on the surfaces. The compound Zr-Si-O and Ta-Si-O films possessed low oxygen diffusion rate and appropriate viscosity, which can provide appreciable oxidation protection for the internal coatings, thus obtaining the excellent oxidation and spallation resistance property. |
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Keywords: | Interrupted oxidation Oxidation resistance Spallation resistance Compound oxide layer |
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