The effect of washing process on the cracking of ZrO 2 microspheres by internal gelation

Abstract ZrO 2 microspheres are widely used as a simulant of UO 2 in the development of nuclear fuel. However, the cracking of ZrO 2 microspheres prepared by internal gelation is still a challenge during drying and sintering processes. To address this issue, we designed and optimized the washing process for obtaining crack‐free ZrO 2 microspheres. Through thermogravimetric, infrared, Raman, BET, and SEM analysis, it is shown that the cracking of the microspheres is mainly related to the pores in microspheres. The washing solvent with low surface tension is used to reduce the effect of capillary force on pore shrinkage. Therefore, the optimal washing process was designed as trichloroethylene (TCE)—0.5 M NH 3 .H 2 O—Propylene glycol methyl ether (PM) and gel microspheres with a high specific surface area of 315.3 m 2 /g and pore volume of 0.4125 cm 3 /g were obtained. The characterizations also further showed that when the microspheres were dried and sintered, the water vapor and the decomposition gas of organic matter were completely released from the pores in the microspheres. Our new washing process could be directly extended for preparing crack‐free ceramic microspheres by internal gelation.