Fabrication of Strong, Hard Submillimeter Zirconia Ceramic Microspheres via an Isobam‐Based Gelcasting System

ABSTRACT This work is the first to report the successful preparation of high‐performance submillimeter‐sized zirconia (ZrO 2 ) ceramic microspheres using the isobutylene‐maleic anhydride copolymer (Isobam) system through physical gelation. This study systematically addressed the inherent problems of single‐component toxicity, oxygen inhibition, and high content of organic additives in traditional chemical crosslinking gel systems (such as acrylamide systems), and overcame the key bottleneck of the Isobam system in preparing high‐solid‐content slurries, where the gelation rate and dispersion were difficult to balance. Through precise pH control and the introduction of ammonium citrate as a co‐dispersant, the rheological properties of the slurry were significantly optimized, and a slurry with a solid content of up to 70 vol% and good stability was successfully prepared. Further, by controlling the oil bath temperature and solid content, rapid and controllable thermal‐induced gelation was achieved in silicone oil, resulting in green bodies with excellent sphericity. After sintering at 1500°C, the obtained ZrO 2 microspheres exhibited excellent comprehensive performance: a density of 6.038 g/cm 3 , a relative density of 99.24%, a compressive strength of up to 312 N, and a Vickers hardness of 1367 HV. Mechanistic studies revealed that in the low‐concentration range (0.2–0.4 wt%), Isobam molecular chains form a three‐dimensional network through hydrogen bonds, and gelation dominates; when the concentration increases, strong electrostatic repulsion and spatial steric hindrance effects dominate the dispersion, thereby inhibiting the formation of the gel network. The elucidation of this mechanism provides a key theoretical basis for precisely controlling the slurry process and the final product performance. This study not only established a reliable technical route for environmentally friendly, economically efficient, and easily producible high‐performance ZrO 2 microspheres but also revealed the gelation‐dispersal competition mechanism, which has universal guiding significance for understanding and designing advanced ceramic material systems based on physical gelation.