Synthesis of Complex Oxide Ceramics in a Fast Electron Beam

Abstract

Synthesis of complex oxide ceramic materials in a fast electron beam is discussed. Powder reagents, along with irradiation, are exposed to air currents, which prevent gases and particles from entering the accelerator. To keep ultrafine powder mixtures in the irradiation zone, they were granulated. Two methods for granulation of an ultrafine powder with the composition 80 wt % Al₂O₃ + 20 wt % (ZrO₂–3Y₂O₃) were used. The first method involved moistening, drying, and subsequent sifting through a coarse sieve. In the second method, the powder mixture was supplemented with a binding additive, which gave a stable volumetric shape to the sample. For the granulation methods used, the features of short-term heating of the oxide powders in air with a fast electron beam with energy of 2 MeV and the zirconia corundum synthesis under these conditions were studied. Granulation of the ultrafine powder made it possible to minimize its weight loss under irradiation. During irradiation of the powder mass, the latter was locally melted, which was accompanied by an intense gas release leading to the formation of hollow ceramic droplets. It has been shown by X-ray diffraction analysis that the oxides do not mutually dissolve in the droplet walls and the recrystallization processes are accompanied by the formation of cubic aluminum oxide microcrystallites and the transition of aluminum oxide in them from the monoclinic to corundum phase. The presence of microcrystallites of evenly distributed fine zirconia dioxide particles in the intergrain spacings indicates the synthesis of zirconia corundum under irradiation. At the same time, the phase composition of zirconium dioxide after irradiation does not change as compared with the initial powder.