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5272 |
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Wednesday, June 07, 2017, Hall 27 11:50 AM Ceramic Coatings |
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Epitaxial growth during the rapid solidification of plasma-sprayed molten TiO2 splat |
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Chang-Jiu Li* / Xi'an Jiaotong University, P.R. China Shu-Wei Yao / Xi'an Jiaotong University, P.R. China Tao Liu/ Xi'an Jiaotong University, Guan-Jun Yang/ Xi'an Jiaotong University, Cheng-Xin Li/ Xi'an Jiaotong University, |
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Crystalline structure of plasma sprayed coatings has a significantly influence on the properties and performace of coatings. In this study, epitaxial growth during the rapid solidification of plasma-sprayed molten TiO2 splat was studied. Through characterization with the resolution transmission electron microscopy and electron back scattering diffraction, the homo-epitaxial and hetero-epitaxial TiO2 splats were found epitaxially growing on the rutile and ±-Al2O3 substrates at the deposition temperature of 500°C. The epitaxial growth of molten TiO2 splat is significantly influenced by the deposition temperature and the crystal orientation. It is easier to form an epitaxial TiO2 splat with a <001> orientation in the direction perpendicular to the substrate surface. To explain the formation of epitaxial splat, a competition mechanism between heterogeneous nucleation and epitaxial growth was proposed. It was indicated that epitaxial growth can take place only when the melt has an undercooling degree lower than a critical value. The face {001} of rutile crystal exhibits the largest growth velocity, which is conducive to form an epitaxial splat for the melt with a largest undercooling degree. In addition, the effect of deposition temperature on the epitaxial growth was simulated. The simulation results are in close agreement with the experimental observations. Thus, during plasma spraying, the formation of epitaxial TiO2 splat can be explained and controlled based on the competition between heterogeneous nucleation and epitaxial growth. |