Formation mechanism of calcium hexaluminate

• Published in: International journal of minerals, metallurgy and materials Vol. 23; no. 10; pp. 1225 - 1230
• Main Authors: Chen, Jun-hong, Chen, Hai-yang, Yan, Ming-wei, Cao, Zheng, Mi, Wen-jun
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 01.10.2016; Springer Nature B.V; School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
• Subjects: Aluminum oxide; Calcium; Calcium ions; Calcium oxide; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Corrosion and Coatings; evolution;first; First principles; Glass; hexaluminate;microstructural; High temperature; Lattice energy; Materials Science; mechanisms; Metallic Materials; Natural Materials; Phase composition; principle;formation; Raw materials; Surfaces and Interfaces; Thin Films; Tribology; formation mechanisms; calcium hexaluminate; microstructural evolution; first principle
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-016-1342-9

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.