Formation of Mullite from Natural Raw Materials Bauxite and Processed Kaolin

Objective: The objective of this study is to investigate the synthesis of mullite using the natural raw materials bauxite and processed kaolin, which have appreciable Al2O3 and SiO2 contents, allowing their incorporation into ceramic masses for mullite production. Theoretical Framework: Mullite 3Al2O3∙2SiO2 is one of the most extensively studied crystalline phases of the Al2O3-SiO2 binary system, and is promising in ceramics due to its excellent chemical, mechanical and electrical properties. On the other hand, its manufacture is difficult, as it requires relatively high-cost materials. Method: The methodology adopted began with the production of test specimens from uniaxial pressing at a pressure of 20 MPa and sintered at temperatures of 1250 °C, 1300 °C and 1350 °C with a heating rate of 5 °C/min and a firing rate of 2 hours. The specimens were then subjected to determination of physical-mechanical properties and characterization of crystalline phases by XRD (X-ray Diffraction). Results and Discussion: The results obtained revealed that the mullite phase was present in all formulations, therefore bauxite and kaolin have the potential to produce mullite, thus becoming an economical way to produce this phase. Research Implications: The results demonstrate the importance of synthesizing mullite using the natural raw materials bauxite and processed kaolin, since these raw materials reduce the cost of the process, making the material accessible. Originality/Value: Although a considerable number of studies have demonstrated the synthesis of mullite from different materials and processes, there is still a need to study the processes for obtaining mullite, one of the most important aluminosilicates in ceramic technology, justifying the use of bauxite and processed kaolin to deepen current knowledge on the subject.