Influence of starch type on characteristics of porous 3Y-ZrO2 prepared from a direct consolidation casting method

Abstract

Starch consolidation casting has been successfully used to produce porous ceramics with complex shapes at a relatively low producing cost. In this work, porous 3Y-ZrO2 ceramics were produced using two types of starch (corn and potato). Concentrated (50-52 vol. (%)) aqueous suspensions of the different 3Y-ZrO2-starch mixtures (i.e. starch to zirconia weight ratios between 0.20 and 0.52) were thermally consolidated and the effect of the type and amount of added starch on properties of resultant dried product was examined. After starch granules burnout, the effect of sintering temperature varying between 1000 and 1500 ºC on the porosity evolution, interconnection and morphology of pores and microstructure of final ceramic was followed by water absorption measurements, Hg porosimetry and scanning electron microscopy SEM. Typical microstructure of the ceramic sintered at 1500 ºC consisted of large nearly spherical pores (created by starch) uniformly distributed in a dense ZrO2 matrix. As the content of starch in the dried product (expressed as volume fraction) Xst is increased from 0.23 to 0.65, porosity of the ceramic sintered at 1500 ºC increased from 38 to 52 vol. (%) for corn starch, while it achieved 50 to 54 vol. (%) for potato starch; thus, lower Xst of potato starch developed a porous zirconia with higher porosity. In this case, the pore structure contained pores having sizes above 50 µm and resulted completely interconnected while for those prepared using corn starch the pore interconnection occurred for Xst above 0.50.