Surface analysis dispersive

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. 

Table 8 shows results obtained from the application of various bulk and surface analysis methods to lithium metal at rest or after cyclization experiments, as well as at inert and carbon electrodes after cathodic polarization. The analytical methods include elemental analysis, X-ray photoelectron spectroscopy (XPS or ESCA), energy-dispersive analysis of X-rays (X-ray mi-... 

The analysis demonstrates the elegant use of a very specific type of column packing. As a result, there is no sample preparation, so after the serum has been filtered or centrifuged, which is a precautionary measure to protect the apparatus, 10 p.1 of serum is injected directly on to the column. The separation obtained is shown in figure 13. The stationary phase, as described by Supelco, was a silica based material with a polymeric surface containing dispersive areas surrounded by a polar network. Small molecules can penetrate the polar network and interact with the dispersive areas and be retained, whereas the larger molecules, such as proteins, cannot reach the interactive surface and are thus rapidly eluted from the column. The chemical nature of the material is not clear, but it can be assumed that the dispersive surface where interaction with the small molecules can take place probably contains hydrocarbon chains like a reversed phase. 

Hammer, G.E. and Drzal, L.T. (1980). Graphite fiber surface analysis by X-ray photoelectron spectroscopy and polar/dispersive free energy analysis. Application of Surf. Sci.. 4, 340-355. 

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]. 

Figure 14. Tunneling spectra of a sample with finely dispersed Rh particles on alumina, exposed to a saturation coverage of CO, and heated to various temperatures in a high pressure atmosphere of Ht. The CO is hydrogenated on the surface. Analysis of the resultant spectra using isotopic substitution indicates that an intermediate species, ethylidene di-rhodium, is formed (1).

The golden-yellow nitrided surfaces were characterized by energy-dispersive x-ray and electron diffraction techniques. The results show that the nitrided surfaces contain mononitride phases. Depth-profile measurements were performed by argon-ion etching and surface analysis by means of x-ray photoelectron spectroscopy. 

It is evident from the above discussion that catalyst characterization is an activity important for scientific understanding, design, and troubleshooting of catalyzed processes. There is no universal recipe as to which characterization methods are more expedient than others. In the opinion of the writer, we will see continued good use of diffraction methods and electron microscopy, surface analysis, IR spectroscopy, and chemisorption methods, increased use of combined EM and ESCA analyses for determining the dopant dispersion, increased use of MAS-NMR and Raman spectroscopies for understanding of solid state chemistry of catalysts, and perhaps an increased use of methods that probe into the electronic structure of catalysts, including theory. 

Elemental and surface analysis measurements had shown that the cokes contained significant amounts of well-dispersed iron chlorides and other contaminants. XPS measurements had shown the importance of the chemical nature of the cokes and their interactions with the catalyst components (and not simply the degree of carbon coverage of the catalyst). IINS focused on the hydrogen-containing part of the coke provided a quite different view of finely divided, highly contaminated, bulk samples of cokes from commercial processes. 

The size distribution of particles containing Cs-137 is not known and here only mono-disperse particles with a radius of 0.5 pm and a density of 1.88 g cm were considered. The model area corresponded to the G45 domain (Fig. 5.1). The start time was at 25 April 1986 at 18 UTC and the model was mn 2 days ahead and then reinitialized and restarted until 7 May at 18 00 UTC. Surface analysis and 3DVAR upper air analysis was used as initial conditions for the meteorology at the beginning of each cycle and 6 hourly boundaries were post-processed from the IFS model. 

For the majority of industrial catalysts, the sizes of supported metal particles arc less than the mean free path of the electrons analysed. All the metal in the particles is effectively analysed. For highly dispersed systems, XPS surface analysis and bulk X-ray nuorcsccncc analysis therefore give similar results. Comparing information from these two techniques can be used to show a change in the distribution of metals on the surface due, for example, to sintering or to the inclusion of one of the metals into the carrier structure. 

Various Dispersive Raman applications for surface analysis Table 13.6... 

The transmission electron microscopy was done with a 100-kV accelerating potential (Hitachi 600). Powder samples were dispersed onto a carbon film on a Cu grid for TEM examination. The surface analysis techniques used, XPS and SIMS, were described earlier (7). X-ray photoelectron spectroscopy was done with a Du Pont 650 instrument and Mg K radiation (10 kV and 30 mA). The samples were held in a cup for XPS analysis. Secondary ion mass spectrometry and depth profiling was done with a modified 3M instrument that was equipped with an Extranuclear quadrupole mass spectrometer and used 2-kV Ne ions at a current density of 0.5 /zA/cm2. A low-energy electron flood gun was employed for charge compensation on these insulating samples. The secondary ions were detected at 90° from the primary ion direction. The powder was pressed into In foil for the SIMS work. 

Surface analysis investigations (XPS) were performed on a Leybold equipment already described in [16]. The fresh catalyst samples were stored imder argon prior to the catalytic tests and the surface analysis. The aged catalyst samples were also handled under argon. The precious metal dispersion was determined for some of the catalysts by a pulsed CO chemisorption technique [16]. 

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