Synthesis of CaAl2O4 from powders: Particle size effect

Starting from high energetic attrition milled mixtures of either α-Al2O3 or amorphous (Al(OH)3) with CaCO3 the binary compound calcium monoaluminate (CaAl2O4) was synthesized with high purity. The processes were carried out on samples with the nominal CaAl2O4 stoichiometry. High energetic attrition milling of the reactants does not eliminate the starting carbonate, both batches showed a high degree of homogeneity and they behaved similarly on heating, forming CaAl2O4 at temperatures lower than 1300 °C. These temperatures are lower than that required for the traditional solid state reaction process. The CaAl2O4 synthesis path implies the formation of cryptocrystalline and crystalline Al2O3, CaO, Ca12Al14O33 and CaAl4O7 as transitory phases. The nucleation and growth of CaAl2O4 took place at 1300 °C and shows a porous structure and small grain size (∼1.5 μm).