Formation and mechanical properties of alumina ceramics based on Al2O3 micro- and nanoparticles

Alumina micro- and nanopowders with the particle size from 200 μm to 40 nm synthesized by the sol-gel method are studied. The particle size dependence of γ-Al 2 O 3 →α-Al 2 O 3 phase transformation is studied by differential thermal analysis, X-ray diffraction method, and transmission electron microscopy. X-ray diffraction data show that for alumina nanoparticles γ-Al 2 O 3 →θ-Al 2 O 3 phase transformation occurs at 900°C, and for micro-particles it occurs in the temperature range 1150–1200°C. The alumina ceramics produced of alumina nanoparticles is shown to have higher flexural strength under three-point bending than the ceramics produced of micro-particles. The obtained results demonstrate that alumina particle size reduction stabilizes the formation of α-Al 2 O 3 at lower temperatures, due to which the grain growth rate decreases and the flexural strength of monolithic oxide ceramics increases.