RESUMEN
Layered quasi-triangular Ce(OH)CO3 assembled from primary nanoparticles was synthesized via a solvothermal method and converted into CeO2 abrasive particles by calcination at 800-1000 °C. With the increase of calcination temperature, the primary particle size increased and the microstructure, mechanical hardness, and chemical activity of the CeO2 particles changed, thus affecting the polishing performance. The calcined products obtained at 800, 850, and 900 °C maintained the layered edge structure of the Ce(OH)CO3 precursor and had a relatively high specific surface area and surface Ce3+ concentration. The samples calcined at 950 and 1000 °C lost the layered structure due to the large-scale melting of the primary particles, and their surface chemical activity decreased. The polishing experiments on K9 glass showed that, with the calcination temperature rising from 800 to 1000 °C, the material removal rate (MRR) first increased and then decreased sharply. The initial increase of MRR was attributed to the increase of mechanical hardness of the layered quasi-triangular CeO2, and the subsequent decrease of MRR was related to the decrease in surface chemical activity and disappearance of the layered edge structure. The product calcined at 900 °C had the highest MRR and best surface quality after polishing due to the layered edge structure and optimal match of chemical activity and mechanical hardness.
RESUMEN
Ceria octahedrons with different microstructure and surface characteristics were prepared by calcining an octahedral CeO2 precursor self-assembled from spherical primary nanocrystals of about 5 nm at 500-900 °C. Structural characterization revealed that with the calcination temperature increasing from 500 to 700 °C, the products maintained a hierarchical structure and primary nanocrystals changed from spherical to octahedral particles. Significant fusion occurred between the primary nanocrystals and the surface of the octahedrons became smooth at the calcination temperature of 800 °C. Single crystal CeO2 octahedrons were formed when the calcination temperature reached 900 °C. The change in microstructure induced by elevated calcination temperature led to increased mechanical hardness and decreased surface chemical activity (specific surface area and surface Ce3+ concentration) of the octahedrons, which had an impact on their polishing performance. The polishing experiments on K9 glass showed that the polishing rate first increased and then decreased with the increment of calcination temperature, indicating that in addition to the mechanical hardness, the surface chemical activity of the octahedrons is also important for material removal. Owing to the best matching of chemical activity and mechanical hardness, CeO2 octahedrons calcinated at 700 °C exhibited the highest polishing rate and the best surface quality for K9 glass.