Processing of A12O3-ZrO2 Nanocomposites for Thermal Barrier Coatings

摘要

Nanocrystalline composites of Al2O3-ZrO2 have been synthesized through fourdifferent processes and evaluated in terms of their densification and ability to retain the metastable tetragonal zirconia phase. The physical stabilization of the tetragonal phase is dependent primarily on the microstructure of the material which is a strong function of the powder preparation method. Significant stabilization of the tetragonal phase after thermal treatments at 1200 deg C was achieved with the colloidal processing approach. The results show that the high degree of phase stabilization in this sample may have come from the creation of a three-phase composite with the ZrO2, Al2O3, and closed pores acting as mutually insoluble phases thereby reducing grain growth and preventing the zirconia phase transformation. Future research will address the relationships between microstructure and processing more thoroughly through electron microscopy with the goal of minimizing the requirement on Al2O3 content. In addition, methods for forming coatings from these powders with phase stabilization will be investigated.