Singh, S. K. D. L., K. "SiOC coatings on yttria stabilized zirconia microspheres using a fluidized bed coating process," Powder Technology Vol. 396, 2022, pp. 158-166.
Abstract: In this study, defect-free SiOC coatings were prepared on yttria stabilized zirconia (YSZ) microspheres by a fluid-ized bed coating process. Effects of the rheological properties of the coating solution on the coating process were elucidated. An impact regime diagram was constructed, which demonstrated that the coating mechanisms were collision/impact. During the fluidized bed coating, longer spouted time resulted in wider dispersion, longer residence time, and more circulatory motion of particles; the fluid distributed more uniformly throughout the column, as demonstrated in our Multiphase Flow with Interface eXchange (MFiX) simulations. Two-step pyrolysis in Ar achieved complete coating layers, which were comprised of SiOC, SiO2, SiC, and graphite. The two stage mass loss during the pyrolysis corresponded to simultaneous reactions due to depolymerization and hydrocarbon loss from 400 to 600 degrees C. Carbon cluster size in the pyrolyzed samples was calculated to be 25 +/- 2 angstrom. This work provides a new method for producing SiOC coatings on micron spheres, with nuclear TRISO fuel particles as the application.
Keywords: SiOC; Fluidized bed coating; Microsphere; Pyrolysis; Rheology; Phase; coated particle fuel; silicon oxycarbide; drop impact; ceramics; nanostructure; evolution; graphite; dynamics; carbon; Engineering