CA6-based macroporous refractory thermal insulators containing mineralizing agents

Aiming at reducing the temperature of CaO.6Al₂O₃ (CA₆) formation, SiO₂, ZnO, and TiO₂ were evaluated as mineralizing agents in an Al₂O₃-CaCO₃ based macroporous thermal insulator. For the concentrations tested (0.6 mol% to 2.8 mol%), SiO₂ presented a small effect in the temperature of CA₆ formation. However, ZnO and TiO₂ favoured full CA₆ generation at 1400 °C, 200 °C below the reference composition. All analysed systems, besides 2.8Si, showed high porosity (> 80 %), suitable mechanical strength and expansion after firing at 1600 °C for 5 h. Softening temperature evaluation highlighted that ZnO- and TiO₂-containing compositions could be used at higher temperatures than the SiO₂ ones. Thus, compositions containing 2.8 mol% of ZnO or TiO₂ were evaluated according to their thermal conductivity (k_eff), showing lower k_eff than the reference composition. Therefore, using these mineralizing agents, which are easily available, may provide reductions in the energy input to produce CA₆-containing thermal insulators and benefits to all other required properties.