Synthesis of Al₂O₃ containing mullite from algerian kaolin and boehmite

In this work, mullite, an advanced structural, optical, and functional ceramic material, was synthesized from Algerian kaolin and boehmite. The appropriate amount of the two raw powders was ball milled for 5 hours and sintered between 1300 and 1600°C. A scanning electron microscope was used to characterize the raw powders and the microstructure of sintered samples. A dilatometer and x-ray diffractometer were used to analyze the formation and transformation of phases. The density and microhardness of sintered samples were measured using a densimeter and a microhardness tester, respectively. It was found that; mullite was the major phase present in the sintered samples besides small fraction of Al₂O₃. The increase of sintering temperature and sintering time increased the densification of samples; a highest relative density of 96 % was achieved at a sintering temperature of 1600°C and a sintering time of 1 hour. Also, the increase of sintering temperature increased mullite fraction and reduced the amount of Al₂O ₃. The microhardness of samples increased with the increase of boehmite content.