Surface microanalytical techniques

Surface Microanalytical Techniques for the Chemical Characterization of Atmospheric Particulates... 

Linton, R. W., Physico-Chemical Characterization of Environmental Particles Using Surface Microanalytical Techniques , Ph.D. Thesis, University of Illinois, Urbana, Illinois, 1977. 

SIMS is one of the most powerful surface and microanalytical techniques for materials characterization. It is primarily used in the analysis of semiconductors, as well as for metallurgical, and geological materials. The advent of a growing number of standards for SIMS has gready enhanced the quantitative accuracy and reliability of the technique in these areas. Future development is expected in the area of small spot analysis, implementation of post-sputtering ionization to SIMS (see the articles on SALI and SNMS), and newer areas of application, such as ceramics, polymers, and biological and pharmaceutical materials. 

The latest innovation is the introduction of ultra-thin silica layers. These layers are only 10 xm thick (compared to 200-250 pm in conventional plates) and are not based on granular adsorbents but consist of monolithic silica. Ultra-thin layer chromatography (UTLC) plates offer a unique combination of short migration distances, fast development times and extremely low solvent consumption. The absence of silica particles allows UTLC silica gel layers to be manufactured without any sort of binders, that are normally needed to stabilise silica particles at the glass support surface. UTLC plates will significantly reduce analysis time, solvent consumption and increase sensitivity in both qualitative and quantitative applications (Table 4.35). Miniaturised planar chromatography will rival other microanalytical techniques. 

A representative collection of surface chemical data of several carbon blacks is compiled in Table 5 which was collected from extensive data [33]. The specific surface area varies by an order of magnitude for the five samples. The total content of heteroatoms (determined by classical microanalytical techniques) amounts to between about 1 and 5wt% which is a sizeable quantity for a material which is nominally pure carbon. 

Microanalytical methods are used to move further down in the characterization scale. X-ray photoelectron spectroscopy (XPS or ESCA), (see Barr) Auger electron spectroscopy (AES), and secondary ion mass spectroscopy (SIMS) as presented by Leta for imaging FCC catalysts, are surface analysis techniques providing chemical analy-... 

Besides the chemical and radiochemical composition, other properties of the collected materials are also often of interest, such as the natine of the chemical compounds present in these substances. For example, the structure of oxide compounds after isolation from the base material or from the coolant is analyzed by X-ray diffractometry or by Mdssbauer spectrometry. Other microanalytical techniques can be directly applied to oxide layers deposited on surfaces, e. g. of steam generator tube sections. Examples in this field are Auger electron spectroscopy for the determination of element concentrations in micrometer areas and X-ray induced photoelectron spectroscopy for the determination of the chemical states of the individual elements. In order to obtain depth profiles over the thickness of the oxide layer, these techniques often are combined with an argon sputtering process (e. g. Schuster et al., 1988), which removes nanometer fractions from the swface prior to the next analysis step. By y spectrometry of the specimen after each sputtering step, the profile of the radionuclides in the oxide layer can also be determined. 

Secondary Ion Mass Spectrometry (SIMS) is a microanalytical technique used to understand the composition (isotopic, elemental, and/or molecular) of any predefined microvolume from any solid or made to be solid region. This region can include a solid s surface, the interface between two or more chemically distinct solids, and/or any internal volume of the solid. Some examples of fields in which SIMS has been applied (listed in order of application), or is being introduced to, include ... 

This volume contains 50 articles describing analytical techniques for the characterization of solid materials, with emphasis on surfaces, interfaces, thin films, and microanalytical approaches. It is part of the Materials Characterization Series, copublished by Butterworth-Heinemann and Manning. This volume can serve as a stand-alone reference as well as a companion to the other volumes in the Series which deal with individual materials classes. Though authored by professional characterization experts the articles are written to be easily accessible to the materials user, the process engineer, the manager, the student—in short to all those who are not (and probably don t intend to be) experts but who need to understand the potential applications of the techniques to materials problems. Too often, technique descriptions are written for the technique specialist. 

This technique is simple in basic principle. Material is first rapidly frozen to the temperature of liquid nitrogen. It is then fractured, cryo-planed to produce a flat surface for analysis, and transferred to the cryo-stage of an SEM. It is analyzed while still frozen, and thus ion movement during tissue preparation should be minimal. A more detailed scheme of a typical procedure (45,46) is given in Subheading 3.4.2.1. This is undoubtedly the most popular microanalytical method with plant scientists at present, and as Table 1 shows it has been applied to a wide range of tissues and research topics (46-53). Recent developments include a... 

These techniques fall into two categories those considered as routine (e.g. atomic absorption and emission spectroscopy, X-ray fluorescence) and a growing number of microanalytical surface techniques (e.g. laser microprobe mass analysis [LAMMA] and sensitive high-resolution ion microprobe [SHRIMP]). Each analytical technique requires specific sample preparation prior to analysis, as summarised in Table 13.1. 

The chemistry of single flnid inclnsions can be determined with certain microanalytical chemical techniqnes. The chemistry of flnid inclusions can be used to document the types of waters at the Earth s surface in the past and to interpret what controlled the chemistry of those waters through time. To date, little attention has been given to chemical analysis of fluid inclusions in lacustrine minerals. However, given the great developments in the last ten years in chemical analysis of individual fluid inclusions, the following techniques could be applied to some lacustrine minerals. 

The second major variant of the XRF technique, which in the last decade has received a lot of attention, both with respect to the methodological developments and regarding its applications in diverse fields, is micro-XRF (p-XRF). This microanalytical variant of bulk XRF is based on the localized excitation and analysis of a microscopically (now even submicroscop-ically) small area on the surface of a larger sample, providing information on the lateral distribution of major, minor, and trace elements in the material under study. The p-XRF can be exploited with laboratory X-ray sources but found its most important areas of application when combined with a synchrotron radiation (SR) source (Janssens et al. 2000). 

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