Estudio preliminar de las transformaciones minerales en materiales bauxíticos durante la cocción y su relación con propiedades físicas de interés

Abstract

Aluminium-rich clays have great interest in the manufacture of refractory ceramics. To assess its usefulness as possible raw materials in the refractory industry, mineral transformations and changes in physical properties during firing have been studied in three mixtures formed by: 1) 100% of bauxite, 2) 75% of bauxite and 25% of illitic-kaolinitic clay and 3) 50% of bauxite and 50% of illitic-kaolinitc clay. Many phases of the natural samples are destabilized during firing, a vitreous phase is formed and new phases crystallize from it. From 1000 °C no clay minerals are detected in any sample, mullite and corundum are formed and hematite content increases (which subsequently decreases). In samples mixed with illitic-kaolinitic clay quartz is also detected and its content, along with corundum content decreases with temperature while that of mullite increases. The changes in color are due to the formation of hematite and its subsequent destabilization. The variations in density and linear contraction would be related to the destabilization of the phases present in the natural samples and the crystallization of new phases such as mullite and corundum.