Preparation and Microstructure of High-Strength Green Bodies with a Low Drying Shrinkage by Hydrothermal Treatment of Hydraulic Alumina

摘要

Hydraulic alumina (HA) paste was subjected to hydrothermal treatment to obtain green bodies displaying a high strength and low drying shrinkage, suitable for the production of porous alumina ceramics. Under optimum hydrothermal treatment conditions (150 °C for 4-8 h), HA hydrates with a skeleton structure were successfully formed in the green bodies. A dense framework composed of submicron-sized pseudo-boehmite grains with large voids was observed. Consequently, the green bodies containing large amounts of water had a high compressive strength and very low drying shrinkage. These gave sintered samples with a high open porosity of over 70% after heating at 1400 °C for 2 h. Hydrothermal treatment of HA paste is useful for preparing alumina ceramics with a high open porosity without the use of organic substances such as binders or fugitive materials.