Abstract
The extrusion behavior of hydraulic alumina (HA) pastes prepared by hydration of the HA was studied in order to fabricate the porous alumina ceramics by an extrusion technique. While all the HA paste samples cured for over 8 h were hardened by hydration, different extrusion behaviors were observed. In the early stage of hydration (<24 h), water separation from the hardened HA paste was remarkable and the paste was not extruded clearly. On the other hand, even without the addition of an organic plasticizer, the hardened HA pastes cured for a long period (>48 h) showed good extrusion behavior. Furthermore, the water acted as a fugitive material in the extruded green bodies. Consequently, the open porosity of the sintered (at 1400°C for 2 h) alumina ceramics could be controlled over a range of 66.9-71.7% by the addition of water (ratio of water to HA powder: 0.8 to 1.4 by weight) without the use of organic fugitive materials.
