Microstructures and crystalline phases of hydrous alumina during calcination induced by microwave heating

Full text: The processing of materials ceramic based on heating by microwave energy has gained increasing importance in diversify of ceramic processing, because of the advantages offered as the reduction of energy, shorter processing times and improved microstructural homogeneity of ceramic bodies. This work aims to calcinate hydrous alumina powder in the conventional furnace and domestic microwave oven. The microwave oven was modified focusing mainly the fine temperature control, to investigate the kinetic of the adsorbed and hydrated water lost. The samples composed by powders with fixed mass were treated by conventional and microwave heating at different temperatures and times. The powders were characterized by X-ray diffraction and SEM. The kinetic curves showed the decrease of the temperature and time for the water desorption and dehydration, and crystalline phase transformation for the powder treated in microwave heating. The powder SEM analyses indicated that the microwave heating promoted a smaller particle agglomeration. (author)