INTERFACIAL REACTIONS IN ZIRCON-HIGH ALUMINA CEMENT COMPOSITES

A study of the interfacial reactions taking place at a zircon-calcium aluminate cement (CA-cement) interface as a function of temperature is presented. The microstructures and morphologies of the interfaces are explained considering the information supplied by the corresponding q uaternary phase diagram (ZrO2-Al2O3-SiO2-CaO). The microstructure of t he interfacial layers varies strongly with temperature. After 2 h at 1 550 degrees C a network of columnar alumina crystals of about 60 mu m in length and approximate to 8 mu m in diameter, together with approxi mate to 30 mu m length a CA6 needle-like crystals are embedded in an a northite rich matrix. Al 1600 degrees C only a glassy phase with alumi na crystals is observed at the interface. For the sample treated at 15 50 degrees C, cracks are defected at the interface due to the presence of alumina crystals, whereas at 1600 degrees C the cracks propagate t hrough the interface without any deflection.