DEVELOPMENT OF SHAPE MEMORY ZIRCONIA PARTICLES AND POWDER COMPACTS
Shape memory Zirconia ceramics (SMCs) has many potential applications in energy storage and energy damping because of its unique shape memory and superelasticity properties - i.e. the ability to change its shape upon loading and fully recover after unloading or heating. In this work, the monodisperse Zirconia ceramic particles with excellent shape memory and superelastic properties have been synthesized by a sol-gel processing method and assembled into a 3D architecture. Iterative processing of the SMC particles and 3D SMC architectures were successfully completed by fine tuning the sol-gel processing conditions and assembly conditions respectively. The obtained sol-gel derived SMC particles were extensively characterized by XRD, FESEM and in-situ micro-compression. Our results show that the monodisperse particles with average diameters of 3 µm can be synthesized by having optimized parameter conditions where acid concentration was 0.075 M and water concentration is 0.6 M, inclusive of a 18 mol%-20 mol% Ceria (Cerium IV Oxide). Apart from having large particles, the monodispersity in the size distribution of the particles was significantly dependent on acid and water concentrations. Tetragonal phase can be stabilized at room temperatures in these micro-scale Zirconia single particles which was essential for stress-induced martensitic transformation upon applied loadings. The single particles exhibit excellent shape memory properties (Shape Memory Effect, SME) with up to 80% recoverable shear strains.
3D SMC architectures have been assembled by utilizing the optimized synthesis parameters producing as-sintered sol-gel powders and also additional spray dried powders which have an average particle size between 5 to 20 µm. Multi-cycle uniaxial compressions of the 3D SMC architectures show that higher porosity (i.e. a less-densely packed powder compact) resulted in higher energy dissipation. Finally, overall optimization of the processing protocols towards the ceramic bodies with enhanced energy damping capacity have been achieved.