| Summary: | A developing energy-saving approach of cold sintering in a pure aqueous medium was applied to the preparation of α-Al<sub>2</sub>O<sub>3</sub> ceramics and performed on spark plasma sintering equipment. The initial γ-Al(OH)<sub>3</sub> and γ-AlOOH powders and the cold-sintered ceramics were studied by X-ray diffraction analysis, infrared spectroscopy, thermal analysis, and scanning electron microscopy to reveal the chemical and structural transformations they experienced during the cold sintering. At 450 °C and 70 MPa, initially γ-AlOOH transformed into a fragile α-Al<sub>2</sub>O<sub>3</sub> material. Porous α-Al<sub>2</sub>O<sub>3</sub> ceramics with about 60% porosity were obtained after cold sintering of γ-Al(OH)<sub>3</sub> in the same conditions combined with subsequent annealing at 1250 °C for 3 h. The role of water molecules in the studied processes was considered as the enhancement of structural mobility in the cold-sintered material due to its reversible hydroxylation similar to earlier investigated supercritical water actions on the precursors during α-Al<sub>2</sub>O<sub>3</sub> formation. Further improvement of the cold sintering setup and regimens would open prospects in α-Al<sub>2</sub>O<sub>3</sub> ceramics manufacturing by an ecologically benign route.
|
|---|