Elaboration and characterization of mullite-anorthite-albite porous ceramics prepared from Algerian kaolin

Elaboração e caracterização de cerâmicas porosas de mulita-anortita-albita preparadas a partir de caulim argelino

Abstract

Mullite-anorthite-albite porous ceramic materials were successfully prepared by a solid-state reaction between kaolin clay and two different additives (CaCO₃ and Na₂CO₃). The starting raw material was characterized by X-ray fluorescence, X-ray diffraction (XRD) and dynamic light scattering techniques. The effect of CaCO₃ and Na₂CO₃ concentration (10 to 70 wt%) on structure, morphology and thermal properties of the obtained ceramics was investigated by XRD, scanning electron microscopy and differential scanning calorimetry (DSC) techniques. The XRD patterns showed that mullite (3Al₂O₃.2SiO₂), anorthite (CaO.Al₂O₃.2SiO₂) and albite (Na₂O.Al₂O₃.6SiO₂) were the main crystalline phases present in the materials. The morphology investigation revealed the porous texture of obtained ceramics characterized by the presence of sponge-like structure mainly due to the additive decomposition at high temperatures. The DSC results confirm the presence of four temperature regions related to the kaolin thermal transformations and the formation of minerals. The temperature and enthalpy of mineral formation are additive concentration dependent. As a result, the optimal content of additives which allowed the coexistence of the three phases, a sponge-like morphology, and high porosity without cracks corresponded to 15 wt% CaCO₃, 15 wt% Na₂CO₃, and 70 wt% kaolin.

Keywords:
clay materials; kaolin; porous ceramics; structure; morphology; thermal analysis