Erbium oxide sol-gel coating as potential tritium permeation barrier and MHD insulator

For the concepts of Pb-Li/Steel and Flibe/Steel fusion blanket, one of issues is the permeation of tritium, which is produced under neutron irradiation. The promising solution is to make coating as tritium permeation barrier (TPB) on the wall of metallic duct. For the concept of LiN blanket, one of issues is a large magneto-hydrodynamic (MHD) pressure drop while liquid Li flows under magnetic field. The promising solution is to make an insulating coating on the inner wall of metallic ducts. Er2O3 ceramic was thought as one of the candidate materials for both of TPB and insulating coating, which has quite low tritium permeability and quite high resistivity comparing with metal. To form Er2O3 coating on metallic substrate, the sol-gel is one of candidate Methods, which has advantages of high homogeneity and single composition for coating, controllable procedure and simple device for process. Especially the sol-gel method has possibility to produce coating on the wall of component with complex shape. In this study, Er2O3 coating was formed on stainless steel by sol-gel method. The microstructure, elemental content and phase of coating were examined by SEM, EDS, XPS and XRD. For Er2O3 coated steel, the deuterium/hydrogen permeability was measured by gas-phase method to show the ability of coating as a TPB, and the resistivity by two-pole method to show the ability as an insulator. The study demonstrates that sol-gel is a viable deposition method, to form Er2O3 coating as both potential TPB and insulator on the structural material of blanket. (authors)