Fabrication of YSZ supraparticles by spray-drying: Enhanced the sphericity and particle packing through controlled dispersion stabilization and surface wettability

In this study, the effects of slurry stabilization and mechanisms on fabricating highly dense and spherical Yttria-Stabilized Zirconia (YSZ) by using the droplet template method, specifically spray drying, have been investigated. To optimize slurry stability, a surface modification technique was employed to control particle-particle and particle-solvent interactions in an aqueous system by using Propionic Acid (PA) as surface modifiers in a 48-h ball milling process. The adsorption of PA on YSZ surfaces provides a short-range steric hindrance, thus improving surface wettability and enhancing particle diffusion due to the short-salvation layers formed on YSZ surfaces. The combination effects of short-range steric hindrance and hydrophobicity have been found to effectively regulate interactions between particles and solvent, leading to improved particle diffusion and preventing premature shell (crust) formation during drying. As a result, highly spherical supraparticles with a sphericity of 99 % were able to be obtained and further transformed into high-density microbeads (99.8 % relative density) with excellent mechanical properties of Hardness ( H ) ≈ 19 ± 0.77 GPa and Elastic modulus ( E ) ≈ 157 ± 4.21 GPa after sintering at 1350 °C for four hours. In comparison, to YSZ stabilized through electrostatic repulsion by using Diammonium Citrate (DAC), the supraparticles tended to have buckled or dimpled shapes with uneven packing and lower mechanical properties. These results demonstrate that controlling stabilization mechanisms and wettability is crucial for managing shell permeability and morphology in droplet-template assembly, providing a practical and scalable method for producing YSZ supraparticles for broader applications, such as grinding media in ceramic processing.