Formation mechanism of calcium hexaluminate

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• 作者：Jun-hong Chen ; Hai-yang Chen ; Ming-wei Yan…
• 关键词：calcium hexaluminate ; microstructural evolution ; first principle ; formation mechanisms
• 刊名：International Journal of Minerals, Metallurgy, and Materials
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：23
• 期：10
• 页码：1225-1230
• 全文大小：783 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Materials Science
  Metallic Materials
  Mineral Resources
  
• 出版者：Journal Publishing Center of University of Science and Technology Beijing, in co-publication with Sp
• ISSN：1869-103X
• 卷排序：23

文摘

To investigate the formation mechanism of calcium hexaluminate (CaAl₁₂O₁₉, CA₆), the analytically pure alumina and calcia used as raw materials were mixed in CaO/Al₂O₃ ratio of 12.57:137.43 by mass. The raw materials were ball-milled and shaped into green specimens, and fired at 1300–1600°C. Then, the phase composition and microstructure evolution of the fired specimen were studied, and a first principle calculation was performed. The results show that in the reaction system of CaO and Al₂O₃, a small amount of CA₆ forms at 1300°C, and greater amounts are formed at 1400°C and higher temperatures. The reaction is as follows: CaO·2Al₂O₃ (CA₂) + 4Al₂O₃ → CA₆. The diffusions of Ca2+ in CA₂ towards Al₂O₃ and Al3+ in Al₂O₃ towards CA₂ change the structures in different degrees of difficulty. Compared with the difficulty of structural change and the corresponding lattice energy change, it is deduced that the main formation mechanism is the diffusion of Ca2+ in CA₂ towards Al₂O₃.