| Abstract Scope |
Defect-free SiOC coatings of 50-100 µm thickness were prepared on YSZ microspheres by a fluidized bed coating process. Effects of 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; fluid distributed more uniformly throughout the column, as demonstrated in our 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 400-6000C. Carbon cluster size in the pyrolyzed samples was calculated to be 25±2Å. This work provides a new method for producing SiOC coatings on micron spheres, with nuclear TRISO fuel particles as the application. |