Synthesis of nonstoichiometric zirconium carbide whiskers by chemical vapor deposition |
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Authors: | Keiji Naito Naoki Kamegashira Noboru Fujiwara |
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Institution: | Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan |
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Abstract: | Nonstoichiometric zirconium carbide crystals with various compositions were prepared by chemical vapor deposition. Two gaseous mixtures, zirconium tetrachloride and argon, toluene and hydrogen, were introduced to the reaction zone where a graphite substrate was heated between 1200 and 1400°C. The deposition rate was proportional to the partial pressure of toluene. The compositional ratio of nC/nZr in the gaseous mixture from 2.0 to 6.0 was found to be optimum for producing needle-like crystals. Needle-like crystal with smaller size were formed when the ratio of nC/nZr was smaller than 2.0, and less needle-like crystals accompanied with more carbon were also produced when the ratio of nC/nZr was larger than 6.0. The temperature of the substrate suitable for the growth of needle crystals was in the range from 1250 to 1300°C. The lattice constants of the products varied as a function of the ratio of nC/nZr in the gaseous mixtures. |
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