가압-진공 하이브리드 주입성형에 의한 알루미나의 균질 성형

Abstract

Conventional methods for preparing ceramic bodies, such as cold isostatic pressing, gypsum-mold slip casting, and filter pressing are not completely suitable for fabricating large and thick ceramic plates owing to disadvantages of these processes, such as the high cost of the equipment, the formation of density gradients, and differential shrinkage during drying. These problems can be avoided by employing a pressure-vacuum hybrid slip casting approach that considers not only by the compression of the aqueous slip in the casting room (pressure slip casting) but also the vacuum sucking of the dispersion medium (water) around the mold (vacuum slip casting). We prepared the alumina formed bodies by means of pressure-vacuum hybrid slip casting with stepwise pressure loading up to 0.5 MPa using a slip consisting of 40 vol% solid, 0.6 wt% APC, 1 wt% PEG, and 1 wt% PVA. After drying the green body at 30oC and 80% RH, the green density of the alumina bodies was about 56% RD. The sintered density of an alumina plate created by means of sintering at 1650oC for 4 h exceeded 99.8%.This method enabled us to fabricate a 110 × 110 × 20 mm alumina plate without cracks and with a homogeneous density, thus demonstrating the possibility of extending the method to the fabrication of other ceramic products.