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Effect of Y-α-Sialon Seeding and Holding Time on the Formation of Elongated (Ca,Dy)-α-Sialon Crystals Prepared via Carbothermal Reduction and Nitridation

Authors

  • Juntong Huang,

    1. Department of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing, China
    2. School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing, China
    3. Department of Engineering Materials, University of Sheffield, Sheffield, UK
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  • Heping Zhou,

    Corresponding author
    • Department of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing, China
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  • Zhaohui Huang,

    1. School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing, China
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  • Guanghua Liu,

    1. Department of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing, China
    2. Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China
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  • Minghao Fang,

    1. School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing, China
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  • Yan'gai Liu

    1. School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing, China
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  • This work was financially supported by the Fundamental Research Funds for the Central Universities (Grant No. 2009PY09).

Author to whom correspondence should be addressed. e-mail: zhp-dms@mail.tsinghua.edu.cn

Abstract

Single-phase (Ca,Dy)-α-Sialon with elongated crystals and high aspect ratios was prepared at 1700°C by carbothermal reduction and nitridation (CRN) with Y-α-Sialon seed crystals. Effects of Y-α-Sialon seeding and holding time on the phase assemblage and crystal morphology of CRN products were discussed. The results showed that adding seed crystals and prolonging holding time could facilitate not only phase transformation, but also crystal refinement. Moreover, they resulted in the increase of the aspect ratios of α-Sialon crystals, due to the decreasing range in the crystal width exceeding that in the length. In addition, a highly unusual phenomenon of crystal size reduction during reaction was observed in the seeded samples with the holding time extending from 2 to 4 h. Crystallization from liquid phase and growth followed by nucleation based on the surface of existing large crystals were the growth modes of elongated α-Sialon crystals.

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