Chemical-physical and mineralogical characterization of ceramic raw materials from Moroccan northern regions: Intriguing resources for industrial applications

Five natural ceramic raw materials from three north-west Moroccan regions (Berrechid, Tiflet and Kemmiset), which are used in the ceramic industry, have been studied with the aim to devise other possible uses or optimize the mixture and thermal conditions for manufacturers. Chemical-physical and mineralogical characterization techniques (XRD, ESEM, FTIR, CEC, TGA, BET, etc.) have been applied either to compare the bulk, grinded (the fraction used in ceramic industry) and sieved materials or to understand their changes upon heating, at temperatures comparable with those applied in ceramic industry. The data indicate that the bulk and sieved materials do not show relevant differences. All the samples are composed for at least 20% wt of quartz, accompanied by a different amount of phyllosilicates. The Tiflet material has a higher content in calcite and dolomite, together with amount of feldspar, which makes this material of particular interest for ceramic industry. Feldspar is used in ceramic industry as fluxing agent inducing early vitrification, increasing the firing shrinkage and decreasing the firing temperatures. The 29Si and 27Al solid state nuclear magnetic resonance spectra recorded before and after heating evidenced the presence of new phases formed by the dehydroxylation and decarboxylation processes. The mineral transformations upon heating were studied also for the clays fraction by in-situ XRD technique.