Feedstock formulations for direct consolidation of porcelains with polysaccharides

Direct-consolidation methods are becoming well-established forming techniqu es for advanced ceramics, because of their advantages in terms of shape cap ability. These advantages could also be exploited to consolidate traditiona l ceramics, such as stoneware or porcelain pottery requiring handles, which could be potentially manufactured in a single step. The most limiting fact or in the transfer of these technologies from advanced to traditional ceram ics is related to the moderate solids loading usually achievable with clay- based suspensions. In this work, new porcelain feedstocks are proposed that use either milled rejected pieces (MRP) of porcelain or a kaolinitic stoic hiometric mixture of SiO2 and Al2O3, i.e., pseudokaolin (PK), The replaceme nt of the clay component by MRP or PK makes it possible to obtain 60 vol% a queous porcelain suspensions, which can be directly consolidated using a re latively low amount (1 wt%, based on liquid volume fraction) of a mixture o f polysaccharides. Steady shear viscosity measurements show that these high ly concentrated suspensions are fluid enough for pouring operations. The gr een and presintered bodies show similar values of shrinkage and relative de nsity, because of the low amount of organic additives used. The total repla cement of the clay component in the starting composition enables a decrease in the firing temperature. Otherwise, for a given firing schedule, the enh ancement of quartz dissolution in the glass phase and the decrease of the a spect ratio of mullite needles lead to an increase of the pyroplastic defor mation index.