Microstructural Study of Alumina Porous Ceramic Produced by Reaction Bonding of Aluminium Powder Mixed with Corn Starch

Abstract

Addition of corn starch to the Al powders in a reaction bonding process has resulted in alumina porous ceramics. The corn starch added was meant to create porosities during heating therefore they act as channels for oxygen to access the inner part of the samples for oxidation. The number of corn starch added to the Al powder was varied from 10%, 20%, and 30 wt. %. The green bodies of pellet samples with diameter of 20 mm and 4 mm height were heated at various temperatures of 1000C, 1200C, and 1400C with a heating rate of 1.5C/minute in air. Microstructural study was performed using scanning electron microscope (SEM) and supported by phase identification using XRD and EDAX. XRD and EDAX have identified the presence of -Al2O3, Fe, and Si which are impurities of Al powders. From SEM, it shows that the outer surface of all samples is denser than the inner part and identified as Al2O3. The thickness of this dense outer skin increases with an increase in heating temperature and the number of corn starch added. After sintering to 1400C, smaller size of pores (0.005 m) originated from the interparticles stack while the bigger pores (0.008 m and 0.0175 m) obtained from the sites left by the corn starch particles were identified by porosimeter test.