Three calcium aluminate (CA) powders were synthesized and added into Al2O3 for the preparation of ceramic-based composites by the processes, either dry-pressing (D), colloidal dispersion/filtration (SH), and hydration-gelation (H). The heat evolution, gelation and related hydration processes of the aluminates and the admixtures were investigated. Besides, the green and the sintering properties of the CaO*Al2O3(CA)-Al2O3 admixtures were measured and are reported. The effects of acetic acid and alcohol (retarding agents) on the hydration reaction of the hydrates were studied, and used for the control of the gelation process. The sintering results of the admixtures with CA indicated the formation of CA6 phase greatly influenced the densification rate and final porosity.

Keywords: calcium aluminate, composite, hydration, gelation, densification