Metal surfaces analytical techniques

L/evelopment of sophisticated surface analytical techniques over the past two decades has revived interest in the study of phenomena that occur at the electrode-solution interface. As a consequence of this renewed activity, electrochemical surface science is experiencing a rapid growth in empirical information. The symposium on which this book was based brought together established and up-and-coming researchers from the three interrelated disciplines of electrochemistry, surface science, and metal-cluster chemistry to help provide a better focus on the current status and future directions of research in electrochemistry. The symposium was part of the continuing series on Photochemical and Electrochemical Surface Science sponsored by the Division of Colloid and Surface Chemistry of the American Chemical Society. 

Castle, J.E. and Watts, J.F. (1988). The study of interfaces in composite materials by surface analytical techniques. In Interfaces in Polymer, Ceramic and Metal Matrix Composites (Proc. ICCI-II) (H. Ishida ed ), Elsevier Seienee, New York, pp. 57-71. 

In addition to the electrochemical techniques, many surface analytical techniques are constantly in use, such as ellipsome-try for the surface thin oxide thickness, multiple reflection infrared spectroscopy (MIR), and X-ray photoelectron spectroscopy (XPS) for surface layer composition, total reflection X-ray fluorescence spectroscopy (TXRFS) for the metal surface contaminants, and naturally atomic force microscopy (AFM) for the surface roughness profile. 

X-Ray Photoelectron Spectroscopy (XPS). This technique is also known as electron spectroscopy for chemical analysis (ESCA), and as this name implies, it is a surface analytical technique. At present it is probably the most versatile and generally applicable surface spectroscopic technique. It is called XPS because of the type of beam used to study the interfacial region, that is, X-rays. These X-rays consist of monochromatic radiation—radiation of a given energy—emitted by a metal target bombarded by an electron beam of several kiloelectron volts of kinetic energy... 

Passivation of active metals to hydrogen reaction has been recognized as an important problem in basic metal-hydrogen studies, especially in their technological application to various situations. Few investigations have addressed these difficulties. The advent of modern surface analytical techniques such as photoelectron spectroscopyy Auger electron spectroscopy, and ion spectrometry offer a tremendous opportunity to attack the passivation question. Each of these techniques is discussed with regard to their capabilities and application to hydride kinetics. 

Use of Surface Analytical Techniques to Examine Metal Corrosion Problems... 

It is important to realize that corrosion rates may be controlled by any of several thermodynamic or kinetic properties of the alloy-scale-environment system and not just by surface or interface reactions. The three stages of high temperature oxidation of a metal, shown schematically in Fig. 1, serve as an example (7). The first or transient stage includes initial gas adsorption, two-dimensional oxide nucleation, initial three-dimensional oxide formation and finally, formation of the dominant oxide that will control the oxidation rate in Stage II. Various portions of Stage I have been widely studied using surface analytical techniques, but its duration can be very short and it is usually assumed (not always correctly) that Stage I has little impact on ultimate corrosion properties of the material. 

The interfacial region of a metal up to the IHP has been considered as an electronic molecular capacitor, and this model has explained many experimental results with success20. Another important model is the jellium model21 (Fig. 3.13fo). From an experimental point of view, the development of in situ infrared and Raman spectroscopic techniques (Chapter 12) to observe the structure, and the calculation of the bond strength at the electrode surface can better elucidate the organization of the double layer. Other surface analytical techniques such as EXAFS are also valuable. 

The chapters in this volume present a concise overview of surface analytical techniques from the specific viewpoint of surface morphology and its modification at the polymer-metal interface. A consistent picture begins to emerge of the chemical reactions occurring on metal deposition and why this leads to metal adhesion. The coeditors hope this information will be timely and useful. 

Formic acid decomposition has been examined on a number of metal oxides using a wide assortment of surface analytical techniques to probe the decomposition pathways. One might expect the most facile adsorption to occur... 

The susceptibility of solid surfaces to contamination often results in a requirement for an ultrahigh vacuum (UHV) chamber for preparation and observation of particular samples. For many materials, including metals such as platinum and nickel, adsorption of hydrocarbons and chemisorption of oxygen are quite fast at atmospheric pressure, and the surface must be isolated in UHV to prevent rapid degradation. In addition, a sample in UHV may be subjected to surface analytical techniques such as X-ray photoelectron and Auger spectroscopy to verify or corroborate Raman results. As a result, much of the early and well-characterized surface Raman experiments were carried out in UHV chambers operating below 10 torr (12). 

A rate constant k is assigned to each surface chemical reaction. This is a schematic representation of the mechanism based upon analogous reactions of metal ion complexes in solution (see Purcell and Kotz, 1977, p, 659-669). Experimental determination of dissolved reactant and product concentrations [ArOH(aq), Mn Caq), etc.] can provide indirect information about the surface reaction [discussed in Stone (1986), Stone and Morgan (1987), and Stone (1987)]. Additional detail concerning the stoichiometry and structure of surface species will require the use of spectroscopic or other surface-analytical techniques. 

The synthesis of a typical model catalyst used in these studies is shown schematically in Fig. 2. The procedure begins with a refractory metal substrate, such as Mo, Ta, or Re, that has been cleaned by standard procedures and verified clean with surface analytical techniques. The structure of the substrate is chosen specifically to match the particular oxide film to be grown since crystal orientation and the nature of the interface or critical parameters in obtaining a high-quality film. A thin metal oxide film, typically 1-10 nm thick, is then deposited onto the metal substrate by vapor deposition of the parent metal in an O2 environment. Thin films of Si02V ° ... 

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