Preparation of alumina ceramics from aqueous suspensions employing the hydrolysis of aluminum nitride

This paper summarizes the effects of selected processing parameters on the behavior of aqueous alumina suspensions during hydrolysis-assisted solidification and on the properties of the green and sintered parts prepared by this technique. Measurements of the changes in viscosity, the pH, and the impedance of aqueous suspensions with time were performed to evaluate the process. Using impedance spectroscopy, the effects of the addition of AlN, the solids content in the ceramic suspension, and the effect of the solidification temperature on the progress of solidification were followed. It was demonstrated that the solidification temperature significantly affects not only the solidification rate but also the properties of the green and sintered parts. A transmission electron microscopy analysis of dry green parts revealed that the host ceramic particles are bound by a predominantly amorphous AlOOH phase, which results in a high strength for the green parts.