Processing of millimeter-sized spherical ZrO₂ granules through sodium alginate cross-linking and an assessment of their resultant properties

ZrO₂–based porous and dense engineering ceramics exhibit a wide range of applications due to their remarkable features. Specifically, applications related to catalytic supports, inert matrix fuel pellets, and structural materials (milling media) require the preparation of millimeter-sized ZrO₂-based spherical granules with high sphericity. This ensures easy handling and recovery, improved mass transfer, uniform packing density, and efficient designs of processes. However, commonly applied granulation methods involve the use of toxic and corrosive reagents and severe processing conditions, which can impede safe industrial manufacturing. The present study investigates the processing of millimeter-sized spherical ZrO₂ granules based on ZrO₂ as a raw material in the form of a solid network and with sodium alginate cross-linked through ion exchange as a patterned structure. The results suggest that optimized spherical ZrO₂ granules, with high sphericity processed between 1000 and 1200 °C, exhibit characteristics preferable for catalytic supports, including good structural stability and hierarchical meso/macro porosity. Furthermore, spherical ZrO₂ granules processed between 1400 and 1500 °C displayed low residual porosity and a refined microstructure, resulting in high compressive strength, comparable to ZrO₂ granules potentially suitable for structural applications such as milling media and inert matrix fuels.