Preparation and characterization of alumina/calcium-hexaluminate ceramic composites from ferrotitanium slag.

• Low-cost Al 2 O 3 -CaAl 12 O 19 can be prepared from ferrotitanium slag. • Ferrotitanium slag can significantly promote the sintering of alumina. • The dominant sintering mechanism is solid solution mechanism. • The sintering densification can improve the thermophysical properties. • The composites have the potential to be applied to thermal storage. Low-cost alumina/calcium-hexaluminate (Al 2 O 3 -CaAl 12 O 19) ceramic composites were prepared using ferrotitanium slag in this paper. By making use of the TiO 2 and MgO originally existing in ferrotitanium slag, the sintering densification of Al 2 O 3 -CaAl 12 O 19 composites was promoted. The results show that the optimum sintering temperature of the composites is 1500 ℃. The dominant sintering mechanism is the solid solution mechanism, i.e., Ti4+ and Mg2+ are dissolved in the CA 6 and Al 2 O 3 lattices and generate numerous defects, which ultimately enhance the lattice diffusion coefficient and matter transport. Sintering densification improves the specific heat capacity, thermal conductivity, and thermal shock resistance of Al 2 O 3 -CaAl 12 O 19 composites. Thermophysical properties analysis indicates that the composites can be potentially used for thermal storage and the slag-utilized ratio is about 60 wt.%. However, the layered cleavage of CA 6 limits further improvement of thermal shock resistance. [ABSTRACT FROM AUTHOR]