Adsorption metal surfaces, SIMS studies

Before this study was done, it was known that the presence of oxygen inhibited the reaction between water and uranium. However, it was incorrectly assumed (and mathematically inferred) from weight gain studies that the mechanism for the inhibition was the formation of a monolayer of adsorbed or chemisorbed oxygen atoms on the oxide surface that served to block the adsorption of water molecules [144]. The SIMS profiles in Fig. 4.44b made after the final exposure to 18OH2 clearly show that the lsO migrating species has traveled to the metal surface without inhibition, and additional reaction with the metal has not occurred to... 

The first task in any experimental study of low temperature corrosion is to prepare a metal surface free of oxide and adsorbed species. For this the sample must be placed in an ultra- high vacuum (UHV) chamber. One then eliminates the natural oxide layer and adsorbed impurities by ion sputtering. Because ion bombardment disturbs the uppermost atomic layers of the metal (Chapter 3), a thermal treatment is sometimes applied in order to reestablish the original surface structure. Once a clean metal surface is available one introduces a known amount of oxygen into the UHV chamber by setting its partial pressure, and one follows the evolution of the reaction using a suitable method. Surface sensitive methods for the study of adsorption and thin film growth include surface analysis by AES, XPS, SIMS, optical methods, in particular ellipsometry, or mass sensitive methods such as the quartz microbalance. 

The interfacial properties of IL/electrode interfaces are different from other media (i.e., aqueous or traditional nonaqueous media) because of the unique properties of ILs, especially the electrochanical properties. To understand the electrode/electrolyte interface chanistry for sensor research, the mechanisms of the electrochemical reactions, and the essential performance-limiting factors, both in the bulk and at the surface of the electrode materials need to be investigated, preferably in situ. In situ analysis is much desired due to the fact that ex situ measurements are usually not able to follow the fast kinetics at electrode interfaces. The past decades have been characterized by a spectacular development of in sim techniques for studying interfacial processes at metal electrodes. Radioactive tracer [31, 32], pulse potentiody-namic [33, 34], and galvanostatic methods [35] have been applied quantitatively to study the adsorption of organic compounds at solid metals. In the study of complex... 

Pb UPD on polycrystalline An electrode in 0.1 M perchloric acid solution has been studied by Henderson et al. [484]. In this study, CV, electrochemical quartz crystal microbalance (EQCM), and probe beam deflection methods have been used. It has been found that Pb UPD proceeds in three steps. The first step comprised water ejection from the gold surface. This step was followed by metal UPD accompanied by the removal of the adsorbed OH. Also, Zeng and Bruckenstein have studied UPD and adsorption of Pb on pc-Au electrodes, applying XPS and TOF-SIMS method in case of 0.1 M NaCl electrolyte [485], and EQCM in case of 0.1 M NaCl04 and 0.1 M NaCl electrolytes [486]. In the presence of chloride anions, the adsorption of Pb—Cl complex has been found. 

The thin-film approach has been shown to be very informative when dilute solutions of commercial polymer formulations are applied to metallic substrates, as the segregation of minor components can be observed readily [42,80]. The adsorption of amine molecules, as analogs of an epoxy adhesive, has been studied by XPS and SIMS [125-128] and the complementary nature of the two techniques demonstrated once again. The existence of a strong donor-acceptor interaction with anodized aluminum was postulated in the later work, and the integrity of the adsorption process appeared to be related to the existence and density of BrOnsted sites on the AI2O3 surface [127]. 

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