Hydrothermal synthesis of novel alpha alumina nano-materials with controlled morphologies and high thermal stabilities

Abstract

Following a strong demand for novel α-Al₂O₃ nano-materials with unique properties, both pure and doped nano-sheets, nano-needles, and nanosized equiaxed particles (reference) of 100% phase-pure α-Al₂O₃, were synthesized at 430–450 °C under 10.3 MPa pressure by the hydrothermal treatment of boehmite powder (γ-AlOOH) in the presence of α-Al₂O₃ seeds and 1–10% morphology modifiers. SiO₂ and H₃BO₃ were used as morphology modifiers to produce phase pure α-Al₂O₃ nano-sheets and nano-needles, respectively, that exhibited strong crystallographic c- and a-faceting and BET surface areas up to 40 m² g⁻¹ stable above 1000 °C. A mesocrystal growth mechanism of the α-Al₂O₃ nano-particles was observed. Unprecedented flexibility to control the sizes and morphologies of α-Al₂O₃ enabled fabrication of 90% porous ceramics with unique pore geometries and pore volumes up to 1.5 cm³ g⁻¹. These novel α-Al₂O₃ nano-materials can be useful in a variety of catalytic applications, nano-filtration, chemical-mechanical planarization, composites, etc.