Influence of acid-treated talc and Na2CO3 flux on mineralogical phase composition and porosity in steatite ceramics

Abstract

The work aimed with the effect of preceramic mixtures containing natural talc (Tc) or acid-treated talc (Tc-ac) supplemented by montmorillonite (Mt) or kaolinite (Ka), and the flux Na2CO3 on the mineral phase composition, porosity and pore size distribution in the steatite ceramics prepared using solid state sintering at 1300 degrees C. The samples were analyzed using X-ray diffraction and porometry techniques and scanning electron microscopy. Application of Mt or Ka in preceramic mixtures with provided comparable results. The acidification of talc using hydrochloric acid resulted in partial release of Mg2+ from the structure. The ratio of SiO2:MgO in Tc was 35:65 (wt%) and 70:30 (wt%) in Tc-ac. Tc, clay minerals, and flux Na2CO3 in the MgO-Al2O3-SiO2-Na2O glass system resulted to the separation of forsterite and protoenstatite, while Tc-ac provided crystallization of protoenstatite at the expense of clinoenstatite in highly porous ceramics. The preceramic mixtures were precursors of bimodal pore size distribution at prepared steatite ceramics.