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

Low-cost alumina/calcium-hexaluminate (Al2O3-CaAl12O19) ceramic composites were prepared using ferrotitanium slag in this paper. By making use of the TiO2 and MgO originally existing in ferrotitanium slag, the sintering densification of Al2O3-CaAl12O19 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 CA6 and Al2O3 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 Al2O3-CaAl12O19 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 CA6 limits further improvement of thermal shock resistance.