Influence of uniformly dispersed mineralizers on firing and mechanical resistance of clay ceramics

Abstract

AbstractSome parameters of the firing of kaolin around 900°C are examined: (1) firing shrinkage; (2) densification, hardening and textural evolution of kaolin ceramics. Experimental results are accounted for by an empirical formula describing the isotherm firing shrinkage of kaolin ceramics.Depending on the precursor salt added, the spreading and dispersion of the mineralizer is more or less homogeneous. If, during thermal decomposition, the salt induces much porosity, this effect can counterbalance the shrinkage caused by the mineralizer. The kinetics of shrinkage, and the final density after firing depend both on the latter effects and on the mineralizer cation. A very good correlation is observed between shrinkage, final density (residual pore volume) and the strength of the fired clay product. The introduction of uniformly dispersed mineralizers causes an increase in mechanical resistance (for identical temperatures and firing times) by a factor greater than 3, occasionally 5) and, for equal firing times and mechanical strengths, lowers the firing temperature by 100-200°C.