Characterization and properties of cordierite – mullite refractories from raw materials and Narathiwat clay (in Thailand)

In the present study, the relationship between characterization and properties of mullite-cordierite refractory were investigated. Talc, alumina oxide and kaolin (Narathiwat clay, Thailand: NRT) were mixed by varying the ratio of MgO+Al2O3+SiO2 as NRT1 (31:66:3), NRT2 (45:54:1), NRT3 (13:86:1) and NRT4 (50:49:1). The mixture was pressed into rectangular shape by a hydraulic press under a pressure of 150 kg/cm2 and sintered at 1300 °C with a heating rate of 5 °C/min for 1 hour of soaking time and cooled down to room temperature in a furnace chamber. Sample dimensions, density, water absorption, porosity, shrinkage, and mechanical properties were measured as a function of firing temperature. The chemical composition and loss on ignition (LOI) of the raw materials were performed using X-ray fluorescence spectrometer (XRF). Effects on the phases formation and morphology that capable to improve mullite and cordierite in samples were performed using X-ray diffractometer (XRD). The results revealed that mullite was the major phase in sintered samples and cordierite was also found which formed during expense of the other phases with talc. SEM pictures exhibited the role of talc in the grain growth of mullite and also showed the formation of pseudohexagonal cordierite which was observed by Scanning electron microscope (SEM).