Influence of total pressure on the microstructures and growth mechanism of ZrC coatings prepared by chemical vapor deposition from the Zr-Br₂-C₃H₆-H₂-Ar system

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• 作者：Xin Ma^a ; ^b ; ^{ustmaxin@163.com} ; Si&rsquo ; an Chen^b ; Min Mei^c ; Yong Li^b ; Haifeng Hu^b ; ^{hfhu_nudt@nudt.edu.cn} ; Xinbo He^a ; Guangde Li^d ; Xuanhui Qu^a
• 关键词：ZrC coating ; Ultra-high temperature ceramic ; Total pressure ; Chemical vapor deposition ; Microstructure ; Growth mechanism
• 刊名：Ceramics International
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：43
• 期：4
• 页码：3501-3509
• 全文大小：3014 K
• 卷排序：43

文摘

Zirconium carbide (ZrC) coatings were deposited on graphite substrates by chemical vapor deposition from the Zr-Br2-C3H6-H2-Ar system. The influence of total pressure on the growth of ZrC was investigated in the range of 5&ndash;60 kPa. As the total pressure increased, the deposition rate increased evidently, and the preferential orientation of ZrC coatings changed from the (200) plane to the (220) plane. The growth mechanism changed from a mass transport reaction to a surface reaction at the total pressure of 20&ndash;40 kPa. At the total pressure below 20 kPa, the deposition was dominated by crystal growth, so the coatings were composed of well-faceted pyramidal-shaped crystals growing along the <001> direction. At the total pressure above 60 kPa, the growth of ZrC coatings was controlled by the nucleation mechanism, so the coatings were cluster-like crystals rapidly growing along the <110> direction. In addition, low pressure was conducive to the formation of near-stoichiometric ZrC without free carbon. These variations of ZrC coatings can mainly be attributed to gas supersaturation and remarkably changed transport diffusion coefficients with increasing total pressure.