Surface concentration ratios, atomic

The atomic surface concentration ratios show that the... 

For example, if there is preferential sputtering where r > 1, the sputtering yield of A is greater than that of B, and the surface will be enriched in B. This enrichment produces an increase in the sputtering yield of B (more B atoms) and a decrease in the sputtering yield of A (fewer A atoms). As the process continues with macroscopic amounts (greater than 10 nm) of material removed, the increased concentration of B balances out the preferential sputtering of A. Therefore, at steady state the surface concentration ratio will differ from that of the bulk ratio when r 1. 

Thus, as for XP S, the average surface concentration Na can, in principle, be calculated by measurement of the Auger current, according to Eq. (2.13). Again, as in XPS, relative sensitivity factors are generally used. The Auger current for the same transition XYZ in a standard of pure A is measured under the same experimental conditions as in the analysis of A in M, whereupon the ratio of the atomic concentrations is... 

The surface atomic ratios (Cd/F, S/F and C(naflon)/F) calculated from the XPS peak areas are listed In Table 1. The results Indicate that the cublc-CdS film has a higher surface concentration of CdS than the hexagonal film. In both, the C(ls)/F(ls) ratio Is similar to Naflon Itself. 

The sorption processes for cobalt complexes can be complicated by hydrolysis reactions of the complex in solution, surface induced ligand loss processes, sorption of hydrolysis products of either amine, protonated amine, or mixed amine/aquo cobalt complexes, and oxidation/reduction processes associated with cobalt. The principal objective of the XPS studies was to evaluate, the chemical state of cobalt and amine ligands, the surface concentration of the respective elements, and the ligand to cobalt ratio as indicated by the surface nitrogen to cobalt atomic ratio. 

When the peak intensity ratio Ij/lj is measured for each of all the elements observed (carbon, oxygen, chromium and nickel), the surface atomic concentration ratio nj/nj of the elements can be given by the following equation, if surface contamination is negligible ... 

It is deduced that competitive adsorption between ZDDP and MoDTC onto the surface occurred during the run, because Mo concentration on the surface with ZDDP + MoDTC oil was lower than that obtained with the oil containing MoDTC alone. The adsorption of the additive on a surface results in formation of a film composed of the decomposition compounds or reaction compounds of the additives with the metal surface. The decline in the Zn/Mo atomic concentration ratio in the film composition with test time indicates that the decomposition products of ZDDP, which had a high coefficient of friction, were preferentially formed and subsequently, Mo compounds were formed. Similarly, an increase in the concentration of MoS2 with time was also observed. A necessary condition for the production of an effective surface film for reducing friction is the previous formation of the compounds derived from ZDDP. 

Fig. 12.2. The surface atom concentration ratio [Ce] to ([Ce] + [M]), in which M is either Al, Zn, or Fe, as a function of thickness of cerium oxide film, both determined by AES profiling, for alloys immersed in solution for the number of days indicated (from R.B.W. Hinton in Reviews on Corrosion Inhibitor Science and Technology (1993), edited by A. Raman and P. Labine, 1-10-1. Copyright by NACE International. All rights reserved by...

The formation of a rare earth metal oxide on the metal surface, impedes the cathodic reduction of oxygen and thus cathodic inhibition is achieved by the addition of a rare earth metal salt to a system. The surface atom concentration ratio, [Ce/Ce + M], where M is Fe, Al or Zn, is a function of cerium oxide film thickness determined by AES depth profiles as shown in Fig. 12.2. 

The two-dimensional order of the Pt-Co alloys was investigated by low-energy electron diffraction. The results, in terms of LEED patterns are shown in Fig. 8. First, the fact that distinct LEED spots are observed indicates that the alloy interface is well-ordered. Figure 8a shows a typical LEED pattern for alloys that contained greater than 75 atom-percent of Pt the hexagonal pattern is reminiscent of a pure Pt(lll) surface. At such high Pt surface concentrations, the outermost layer is most likely heterogeneous, populated by comparatively wide Pt(lll) domains. Fig. 8b shows that a different LEED pattern is obtained when the Pt Co atom-percent ratio is 3 1. Under these conditions, it may be post-... 

Surface concentrations of the impurities Fe, Mg, Cl, and C in silicon samples are given in Fig. 10 as atomic ratios of the respective elements related to silicon. Unlike Fe, Cl, and C, the Mg surface concentrations up to now can be given only in arbitrary units. 

Taking into account the molecular sizes of the adsorbed compounds, the extents of adsorption, calculated as molar ratios of them to surface Pd atom, seems to be too large for most of the catalysts. Therefore, it is considered that the spillover from Pd onto support takes place with both compounds. The amounts concentrated on the surface of surrounding support will influence the surface concentration on Pd, thus affecting the hydrogenation on Pd surface. These preliminary results of adsorption measurements suggest that a support which can adsorb both modifier and substrate is favorable. In other words, a support with appreciable amounts of both acidic and basic sites, such as Ti02, seems to be preferable. 

The reason of the lower activity of the sample mono 1 appears related to the nature of cobalt species present in the two samples, as detected by X-ray photoelectron spectroscopy (XPS) (see Fig. 2). While the spectrum of the mono 1 shows only the signals of Co (Co2p3/2 =780.5 eV) and is characterized by a distinct shake up satellite, the spectrum of the sample mono 2 contains lines of both Co and Co species at the binding energy of 779.0 eV and 780.3 eV, respectively, which are typical for the C03O4 mixed oxide [10]. Another important difference between the two samples is the cobalt and cerium surface concentration, being the Co/Ce atomic ratio of 0.9 for mono 1 and of 1.4 for mono 2, respectively. On this basis, the reason of the lower activity of mono 1... 

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