GRAIN SIZE CONTROL AND PHASE TRANSFORMATIONS IN NANOPHASE A1_2O_3-ZrO_2

摘要

The evolution of grain size and phase distribution in ZrO_2-Al_2O_3 powders as a function of composition and heat treatment has been investigated. Colloidal dispersions of Al_2O_3 and ZrO_2 were combined to obtain mixtures of 10 percent, 20 percent, 30 percent and 50 percent vol percent Al_2O_3 in ZrO_2-^sThe powders were then calcined at 600 deg C for 17 hours in air and heat treated at 1100 deg C for 24 and 120 hours and at 1200 deg C for 2 hours. XRD and TEM were used to determine the phases present and the grain size. The samples that maintained 100 percent tetragonal ZrO_2 tended to have A1_2O_3 grains that were larger than the ZrO_2 grains, precluding a grain boundary pinning mechanism for grain size control. In several cases, evidence of excessive grain growth in Al_2O_3 was found. In order to maintain the desired ZrO_2 grain size with a smaller quantity of Al_2O_3, it will be necessary to improve the mixing of the two components and to reduce the starting size of A1_2O_3.