Electron-Beam Synthesis of Complex Titanates

Ceramic synthesis is the most important stage of ceramic production. Reducing its energy consumption and time costs is the goal of many studies. As an alternative to traditional solid-phase synthesis, synthesis in a powerful beam of fast electrons is considered. Mixtures of Al2O3 + TiO2 oxides with and without the addition of ZrO2 were heated in air by electrons with an energy of 1.4–2.5 MeV at a power density of up to 25 kW/cm2 and higher at a movement speed of the cuvette with the powder mixture of oxides in the irradiation plane from 0.25 to 1 cm/s. The mixture melted during irradiation and the synthesis of complex titanates in the form of ceramic drops with a porous structure took place. It was found that porosity is regulated by irradiation parameters and cuvette movement speed. The synthesized ceramics have an oxygen deficiency and a characteristic gray-blue color. Annealing in air is accompanied by oxidation of the ceramics and transformation of this color into white. This occurs due to a change in the valence of a small part of Ti included in the ceramics from Ti3+ to Ti4+ as a result of oxidation. The thermal expansion curve shows hysteresis, indicating phase transformations due to oxidation. After thermal annealing in the atmosphere, the hysteresis disappears. Electron beam processing of the Al2O3 + TiO2 mixture with the addition of ZrO2 led to the synthesis of glass ceramics of a complex composition containing zirconolite. Zirconolite is currently the most promising material for the immobilization of radioactive materials. The main reason for the complication of the glass ceramics composition was the presence of uncontrolled impurities in the original mixture, in particular Ca. The hardness of the ceramics, depending on the porosity and synthesis conditions, can vary from 1.5 to 10.5 GPa.