Abstract
ZnAl2O4 has recently been reported to enhance thermomechanical properties and slag corrosion resistance of refractory castables. The pore generation and deleterious expansion during in situ ZnAl2O4 formation can limit their amount in a refractory composition. A comprehensive dilatometric study is presented, identifying the optimum raw materials and processing conditions. Preformed ZnAl2O4 refractory aggregates were synthesized from industrial ZnO and reactive Al2O3 by two-stage firing at 1050 ℃ and 1700 ℃ resulting in 0% open porosity. The ZnAl2O4 powder calcined at 1050 ℃ is also a good refractory matrix material as it has better sinterability than preformed refractory-grade MgAl2O4 and calcined alumina. The thermal expansion coefficient of ZnAl2O4 aggregate in the range of 70–1600 ℃ was found to be 10.7 × 10−6 K−1, which is similar to tabular Al2O3 (10.3 × 10−6 K−1) and MgAl2O4 (10.3 × 10−6 K−1), but lower than dead burned MgO (16.4 × 10−6 K−1), creating the possibility of developing thermal shock resistant refractories by utilizing this mismatch.
