The porosity ε and radial compression strength St of uniaxial dry-pressed powders were examined in several mixtures which are composed of alumina fine particles (AFF or AFC), coarse (ACF or ACC), talc fine (TF) and coarse (TC). It should be noted that the shape of talc particles is flaky while that of alumina is blocky. Flaky particles easily orientate at right angles to the compression direction. The relations among ε, St and compression force P were represented by Eq. 1, 2 and 3 in all the mixtures examined.
The packing efficiency was improved by mixing two components in AFF-ACC system, but deteriorated in AFC-TF, ACF-TC and TF-TC. This is because small particles can enter into the inter-spaces of large particles in the case of mixture of blocky-shape powders. On the other hand, particles with blocky shape may disturb the orientated layer structure of flaky ones in the case of mixtures containing both blocky and flaky particles. It was shown that a logarithmic mixture rule for St under the same porosity is approximately valid in AFF-ACC, AFC-TC and TF-TC.
