The new nano-enabled phase map of ZrO-AlO.

Rapid development of nanotechnology often requires verification of existing phase diagrams, which were suitable for bulk materials. This work presents a new phase map (phase diagram) for AlO-ZrO crystalline powders including the role of the nanoscale particles. AlO-ZrO composites are relevant for industry for applications demanding high hardness. The nanopowders were manufactured via co-precipitation process followed by microwave hydrothermal synthesis (MHS) at 270 °C, drying at room temperature and annealing in the temperature range 300-1500 °C. The phase composition was investigated using X-ray diffraction (XRD) and Rietveld refinement analysis. The grain size and size distribution were calculated using Rietveld refinement analysis and using transmission electron microscopy (TEM). A particular feature of the composites was the nanoisolation, separation of different phases on a nanoscale. This feature limited grain growth during annealing and permitted the phase diagram for a nano-enabled system to be determined, which turned out to be different from that of conventional composites. In particular, considerable solubility of Al in ZrO was found for temperatures less than 1000 °C.