Elastic properties of porous oxide ceramics prepared using starch as a pore-forming agent

摘要

The elastic properties, in particular the tensile modulus (Young's modulus) and Poisson ratio, of porous alumina, zirconia, and alumina-zirconia composite ceramics are studied using the resonance frequency method and the results compared with theoretical predictions. Starch is used as a pore-forming agent, so that the resulting microstructure is essentially of the matrix-inclusion type (with large bulk pores, connected by small throats when a percolation threshold is exceeded). It is found that for this type of microstructure the porosity dependence of the Young's modulus is significantly below the upper Hashin-Shtrikman bound and the power-law prediction; it corresponds well, however, to a recently proposed exponential relation and to an empirical volume-weighted average of the upper and lower Hashin-Shtrikman bounds. Results for all three types of ceramics indicate that - in the porosity range considered, i.e. up to approximately 50 percent - the Poisson ratio depends only slightly on porosity.