Advanced Approaches for Producing Nanocrystalline and Fine-Grained ZrO2-Based Powders(Review) I. Mechanical, Physical, and Chemical Methods (Excluding ‘Wet’ Chemistry)

The first part of this review addresses mechanical, physical, and some chemical methods (thermal decomposition, dynamic method, solution combustion synthesis, and sonochemical synthesis) for producing nanocrystalline and fine-grained ZrO₂-based powders. Mechanical methods (high-energy grinding in planetary and ball mills in dry and liquid environments) are used in the synthesis of ZrO₂ powders and analysis of ZrO₂ phase transformations, in the hydrothermal synthesis of ZrO₂ powders in acidic and alkaline environments, and for the deagglomeration of powders produced by other methods. Physical methods (plasma processing, reactive magnetron sputtering, and chemical vapor deposition) are employed when the requirements for powders are prioritized over production costs. They are used in the development of catalysts, sorbents, and coatings. Chemical methods provide control over the formation of primary particles with specific morphology, size, and surface area. Thermal decomposition produces primary particles shaped as spheres, nanorods, and hollow ZrO₂ microspheres with customizable shell structures. Dynamic methods, involving the detonation of high-energy materials or explosives, are promising for the synthesis of nanosized ceramic oxide powders with narrow particle size distributions. Solution combustion synthesis is based on the propagation of self-sustaining exothermic reactions in aqueous or sol–gel environments. Sonochemical synthesis relies on acoustic cavitation. The synthesized powders are applied in the design of photocatalysts, optical materials, forensic materials for fingerprint detection, sensors, biological markers, etc. There is no universal synthesis method that would meet the diverse requirements for all ZrO₂-based materials. The selection of a method to synthesize the starting powders depends on the requirements for properties of the resulting composites.