Reactive Hot-Pressing of Clays and Alumina

The temperature, pressure, and time dependence of bulk density and the compressive strength of clay and boehmite compacts subjected to reactive hot-pressing were determined. The strength and the bulk density are linearly related to the extent of the dehydroxylation reaction which occurs during reactive hot-pressing. In decomposition reactions the reactivity (for interparticle bond formation) and mobility (for densification) may result from the broken bonds and resultant unsatisfied valence links produced by the reaction. On the basis of this postulation, the following empirical relation, correlating the functional relation between strength or density and temperature and pressure was obtained: Application of this equation to the data obtained experimentally produced energy values, for both densification and interparticle bonding, which are much less than that of the activation energy or the enthalpy of the reaction involved. The different energy values for interparticle bonding and densification are believed to indicate different controlling modes for these processes.