Objectives, surface analysis

Chemical analysis of the metal can serve various purposes. For the determination of the metal-alloy composition, a variety of techniques has been used. In the past, wet-chemical analysis was often employed, but the significant size of the sample needed was a primary drawback. Nondestmctive, energy-dispersive x-ray fluorescence spectrometry is often used when no high precision is needed. However, this technique only allows a surface analysis, and significant surface phenomena such as preferential enrichments and depletions, which often occur in objects having a burial history, can cause serious errors. For more precise quantitative analyses samples have to be removed from below the surface to be analyzed by means of atomic absorption (82), spectrographic techniques (78,83), etc. 

Special purpose articles describe analytical methodology for specialized systems such as art objects, surfaces, or residues (see Fine ART examination AND CONSERVATION NONDESTRUCTIVE TESTING SURFACE AND INTERFACE ANALYSIS and, Trace AND RESIDUE ANALYSIS). Many of the techniques Utilized for these systems ate also discussed ia materials charactetizatioa and separations articles. The methodology and some of the techniques are unique, however, and the emphasis ia these special topics articles is oa appHcatioa to a particular system. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

A typical sample would have a surface area of the order 10 x 20 mm. The preparation of the surface for examination is the subject of an ASTM standard (ASTM E1078-97), and the objective is to ensure that the surface to be analysed has not been contaminated or altered prior to analysis. The techniques of surface analysis are sensitive to surface layers only a few atoms thick, so the degree of cleanliness required will be much greater than for other forms of analysis. Nothing must be allowed to touch the surface to be analysed. 

Brands proposed a calculation method in the case of segregation A special type of inhomogeneous, particulate objects is the surface analysis by microscopic techniques e.g. analytical electron sj troscopy, laser induced mass spectroscopy or proton-induced X-ray emission. Here the minimum sample size can be translated into the minimum number of specific sample points in the specimen under investigation. 

X-ray microanalysis techniques— in particular, electron probe x-ray microanalysis (EPXMA or EPMA) and SEM coupled with energy dispersive spectrometers (EDS, EDX) are, by far, one of the surface analysis techniques most extensively used in the field of art and art conservation, and they have actually become routine methods of analyzing art and archaeological objects and monitoring conservation treatments [34, 61, 63]. 

For electrochemists whose principal objective is analysis of constituents in solution, the path is straighter and the hill less steep. The reaction model often used is a redox reaction in which the interfacial reaction is simply electron transfer, and surface chemical reactions among radicals can be neglected. The electrode is regarded as stable during the reaction and is not intended to take any chemical part in it. The function of the surface is not electrocatalytic, it is simply to be a source and sink of electrons, the energy of which may be controlled by variation of the electrode potential. 

This paper is a synopsis of the introductory lecture at the American Chemical Society Symposium on "Industrial Applications of Surface Analysis." Following a review of the objectives of surface analysis, an outline is given of the design principles for measurements to achieve these objectives. Then common techniques for surface analysis are surveyed briefly. An example of the application of these techniques in microelectronics is indicated. The paper concludes with an assessment of the major advances in surface analysis during the past decade and an indication of the major current trends which could lead to comparable advances during the coming decade. 

The main purpose of this Introductory lecture is to set the stage for the detailed papers which follow by indicating broadly the objectives, principles and methods of modern surface analysis. A secondary objective is to provide some perspective on the major developments in modern surface analysis methods during the past decade, and on the prospects for their future development during the coming decade. 

The objectives of surface analysis, articulated nearly a decade ago ( 1, 2) and reiterated many times since 0-6), are... 

Although both the laboratory and industrial scale materials science of catalysts requires an integrated approach as already mentioned above, it is customary to classify the characterization methods by their objects and experimental tools used. I will use the object classification and direct the introductory comments to analysis, primarily elemental and molecular surface analysis, determination of geometric structure, approaches toward the determination of electronic structure, characterization by chemisorption and reaction studies, determination of pore structure, morphology, and texture, and, finally, the role of theory in interpreting the often complex characterization data as well as predicting reaction paths. 

TJ apid entrainment carbonization of powdered coal under pressure in a partial hydrogen atmosphere was investigated as a means of producing low sulfur char for use as a power plant fuel. Specific objectives of the research were to determine if an acceptable product could be made and to establish the relationship between yields and chemical properties of the char, with special emphasis on type and amount of sulfur compound in the product. The experiments were conducted with a 4-inch diameter by 18-inch high carbonizer according to a composite factorial design (1, 2). Results of the experiments are expressed by empirical mathematical models and are illustrated by the application of response surface analysis. 

Quality improvements and evaluations of surfaces demand the checking and analysis of surface characteristics. Sophisticated modeling procedures with built-in check and repair features have eliminated the extensive analyses needed after model creation procedures. However, the results of these procedures and the processing of imported models require post-creation analyses. The objective is analysis not only to reveal errors, but also to check the suitability of models and modeled objects for their application. Real time checking and analysis in advanced modeling procedures are based on the same principles as separate checking and analysis. 

See also Archaeometry and Antique Analysis Dating of Artifacts Metaiiic and Ceramic Objects Art and Conservation. Forensic Sciences Hair. Polymers Naturai Rubber Synthetic. Surface Analysis Particie-Induced X-Ray Emission Ion Scattering. 

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