Chromium oxide, interface with oxygen

The aforementioned requirements on surface stability are typical for all exposed areas of the metallic interconnect, as well as other metallic components in a SOFC stack (e.g., some designs use metallic frames to support the ceramic cell). In addition, the protection layer for the interconnect, or in particular the active areas that interface with electrodes and are in the path of electric current, must be electrically conductive. This conductivity requirement differentiates the interconnect protection layer from many traditional surface modifications as well as nonactive areas of interconnects and other components in SOFC stacks, where only surface stability is emphasized. While the electrical conductivity is usually dominated by their electronic conductivity, conductive oxides for protection layer applications often demonstrate a nonnegligible oxygen ion conductivity as well, which leads to scale growth beneath the protection layer. With this in mind, a high electrical conductivity is always desirable for the protection layers, along with low chromium cation and oxygen anion diffusivity. 

For (1), it Is desired that the implanted oxygen come to rest at the Cr/Aip., Interface, so that the possibility of reaction to form Cr O., exists. The chromium layers deposited for system (1) were analyzed before implantation using Rutherford Backscattering Spectroscopy (RBS). From the analysis, It is known that the Cr layer already contains a small amount of oxide which may affect the implantation. After implantation with 80 keV oxygen at a fluonce of 1 x 10 ions/cm RBS analysis showed no mixing effects. The Cr film will now be etched from this sample, and both the implanted and unimplanted areas will be reanalyzed using RBS to determine which area contains more chromium. Transmission Electron Microscopy (TEM) analysis will also be performed. 

Various etchants have been recommended for the remaining metals of engineering practice, but it is doubtful if sufficient work has been reported to differentiate between them or to assess their effect on the durability of the bonds formed with different adhesives. Strong, durable bonds are uncertain with copper because of the ease with which a weak, friable oxide is formed. Even when coated with an adhesive, oxygen can diffuse to the interface and eventually cause failure. Brass has an oxide film almost entirely of zinc oxide and, as with zinc galvanized iron, it can hydrate or form salts with the tackifiers added to some contact adhesives. Cadmium is met with as a plating if a strong, durable adhesive bond is essential, it should be replaced by chromium, the surface of which can be treated as stainless steel. 

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