A molybdenum containing austenitic steel was exposed in hydrochloric acid at various potentials in the active and passive ranges of the alloys. The surface compositions were analyzed by the ESCA technique. The influence of pretreatment by ion bombardment and mechanical polishing on the passivation behavior was investigated. The passive film formed on the surface consists mainly of a mixed Fe‐Cr‐Mo oxide. The average content of Cr3+ in the oxide is about 70%. The inner layers of the oxide product consist mainly of Cr oxide. The Ni content in the oxide is low. The concentration and the chemical state of Mo is potential dependent. At low potentials in the passive range, the four‐valency state is predominant, while at high potentials Mo exists mainly in its six‐valency state. On the surface of the oxide, a layer of hydroxide is present. Chloride ions are incorporated into the passive film. The thickness of the passive film increases with the potential in the passive range from 10 to 15Å. The composition of the metal phase changes during active dissolution. Thus, the alloying elements are enriched on the surface and thereby control the dissolution rate, control overpotentials, and provoke passivation of the alloy.

produced by annealing of sputtered thin films. The in situ XPS study focuses on both the core level peaks and Auger peaks. The peak positions, shapes, satellites as well as Auger parameters are compared for different silicides. The factors that influence the Ni core level peak shifts are discussed. The Ni 2p 3/2 peak shape and satellites are correlated with the valence band structure. The effect of argon ion etching on surface composition and chemical states is also investigated.

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The present study deals with mechanisms of the reaction process of fabricated thin film Ni/SiC contacts by means of XRD, XPS and Raman spectroscopy. After annealing SiC samples sputter coated with Ni at 800 and 950uC in vacuum for 20 min, the dominant silicide is textured Ni 2 Si. Its formation consists of two stages: initial reaction rate and subsequent diffusion controlled stage. For ultra thin initial Ni layer (y3-6 nm), islands formation of Ni 2 Si is observed after heat treatment. Increasing the Ni film thickness prevents this phenomenon. The C released owing to the Ni 2 Si formation reaction forms a thin graphite layer on the top of the surface and also tends to form cluster inside the reaction layer. The overall degree of graphitisation is higher at 950uC than that at 800uC.