4 research outputs found
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Behavior of CuP and OFHC Cu anodes under electrodeposition conditions
Films formed on CuP (with 0.05 wt % P) and OFHC Cu anodes in electroplating solutions were studied by X-ray Photoelectron Spectroscopy, X-ray Absorption Spectroscopy, electrochemical methods, and a newly developed gravimetric technique. The black film formed on CuP in Cl-containing solutions was found to resemble a porous sponge composed of CuCl but laden/with concentrated CuSO{sub 4} solution. The difference between the buoyancy-corrected measured mass change and the charge-equivalent mass change was found to have two components: a reversible part that comes and goes as the current is turned on and off, and an irreversible part that remains on the surface and increase in mass with time. The irreversible part results from the anodic film, which increases linearly with charge density but independent of current density. The reversible part of the mass change arises from the weight of the diffusion layer. In contrast to CuP, OFHC Cu releases much more Cu{sup +1} during anodic polarization and forms a poorly-adherent anodic film that is considerably heavier than the black film for a given charge density
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In situ XANES study of the valence state of chromium during electrochemical polarization of AlCr alloys
The chemistry of chromium in the passive film on pure chromium and sputtered AlCr thin films has been studied in situ in an electrochemical cell under potential control using XANES. Depending on the rate of potential increase, the 6-valent chromium can dissolve from the alloy or be trapped in the passive film where it is electroactive i.e. the valence state can be reversibly switched between the 3- and 6-valent states by switching the applied potential. The kinetics of these processes were investigated
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X-ray characterization of oxidized tantalum nitride
Sputter deposited non-stoichiometric tantalum nitride films are oxidized in air between 200 and 500{degrees}C to form a passive film. The oxidized films have been studied with x-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption near edge spectroscopy (EXAFS). Films exposed to KOH formed a non-protective surface layer identified in low angle XANES and EXAFS as KTaO{sub 3}. Auger electron and x-ray photoelectron spectroscopies were also used to characterize these films
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In situ XANES studies of the passive film on Fe and Fe-26Cr
In situ x-ray absorption near edge structure (XANES) has been used to study the passive film on iron and Fe-26Cr thin films under potential control in borate buffer. The technique enables information on both valence state and the amount of material lost through dissolution to be determined. The passive films on both Fe and Fe-Cr are formed with negligible dissolution. On reduction, iron is lost from both films due to reductive dissolution. In the case of Fe, it has been determined that some of the iron in the film is reduced back to-the-metallic state. Concurrent monitoring of the Fe and Cr edges has shown that in the case of Fe-Cr, loss of iron leads to enrichment of Cr in the film