Preparation and characterization of an Al2O3–ZrO2 nanocomposite, Part I: Powder synthesis and transformation behavior during fracture

An alumina–zirconia composite containing 5 mol% zirconia was prepared by following a wet interaction process in aqueous medium via the sol–gel route. The formed hydrogel which was aged for proper growth and orientation at room temperature, was then dried at a low temperature to minimize agglomeration. The sol–gel derived precursor powder was properly characterized through determination of surface area, particle size and thermal analysis. The sintering behavior was studied by compacting the nano-powder through cold isostatic pressing where maximum densification of 98.4% was achieved at 1550 °C. During Vickers indentation using a 5 kg load, cracks were propagating around the grain boundaries and fractured the ZrO2 particles, which was associated with t-ZrO2 to m-ZrO2 transformation. Sintering was studied in the absence of a mineraliser.