Time-resolved Studies of Alumina Ceramics Processing with Neutron and Synchrotron Radiation Data

The paper reviews progress for a program of research on alumina ceramics processing, with particular reference to diffraction results achieved using tube x-rays, neutrons and synchrotron radiation. Outcomes from three related studies are examined. l Calcination of alumina hydrates to o-alumina via intermediate aluminas, including some new results indicating the co-existence of cubic and tetragonal y-alumina polymorphs following boehmite decomposition. l Post-sintering heat treatment of debased alumina ceramics to develop/control crystallisation of glassy phase material. l Controlling particle size in zircon/alumina reaction-sintered products using magnesia additions. Introduction The Materials Research Group, Curtin University of Technology is conducting a program of research on the processing of alumina-matrix ceramic materials for wearresistant applications. The research aims to make use of alumina powders being produced in Western Australia by the Bayer process. Ceramic processing trials are mainly evaluated by scanning electron microscopy (SEM) and Bragg-Brentano laboratory x-ray diffraction (XRD) after the sintered material has cooled to roomtemperature. Neutron diffraction (ND) has proved to be of considerable value for timeresolved studies of selected processing protocols following extensive processing trials which have been evaluated by SEM and XRD. Some use has also been made of roomtemperature synchrotron radiation diffaction (SRD) patterns to obtain high resolution diffraction data in selected processing trials. It is envisaged that high-temperature SRD measurements will be conducted in the future to complement the high-temperature ND results in order to characterize the near-surface and bulk character, respectively, of the transformation and sintering mechanisms involved in the processing of alumina-matrix ceramic materials. The phase transformations occurring in the calcination of the hydrated alumina phase, gibbsite [AI(OH to a-alumina [Al2031 is of fundamental importance in Copyright (C) JCPDS International Centre for Diffraction Data 1999