ESCA Investigations

Thorsteinson etal.21 investigated mixed Mo-V-Nb catalysts containing 20 to 30 at% Vfor the oxidative dehydrogenation of ethane. Extensive reduction by ethane at 400 °C showed an increase of the intensity of the Nb peaks relative to those of Mo. Comparison of catalysts with and without V showed that this strongly facilitates the reoxidation of Mo4+ to Mo6+ at the surface. 

Roozeboom et al.35 were only able to indicate for a 7-Al203 supported vanadia catalyst that the surface phase differs from V2Os. 

Haber and J. Stoch, React. Kinet. Catal. Lett., 1978, 9, 319. 

In an investigation of a-Ala- V Oa solid solutions Pomonis and Vickerman38 showed that the surface V/Al ratio increased linearly with x, but that the surface oxygen content increased strongly beyond x = 0.01, which seems to be connected with easier charge transfer. 

Jagannathan et al.39 show that catalysts with 10% V2O5 on A1203 or M0O3 contain V4+ and that the amount of this is greater with A1203 as a support. In both cases the V4+ content increases on reaction with toluene. 

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Fig. 5. Classification of samples with respect to ESCA investigation into homogeneous, laterally inhomogeneous, vertically inhomogeneous and inhomogeneous types...

An ESCA Investigation Of The Surface Chemistry Of The Nitration And Denitration Of Cellulose Materials... 

It was shown by ESCA investigations that the oxidation of tungsten by oxygen or air starts at room temperature. The oxide formed in oxygen as well as in dry or humid air is always tungsten trioxide. The thickness of the oxide layer increases slowly with increasing temperature up to 200 °C, but increases rapidly above 200 °C. Increase in humidity also accelerates the oxidation rate. 

Water reacts with tungsten below the boiling point. In principle, water acts as an oxidizing agent. According to ESCA investigations WO2, WO3, and oxide hydrates are formed [3.3] ... 

Conformations of heterocyclic derivatives of hydroxylamine 81T849. Electron spectroscopy for chemical evaluation (ESCA) investigation of... 

An ESCA investigation of some closely related N-substituted forms of (54) with X = N, R = NMePh, NPf2 or NBu and R = Ph, using the chemical shifts of N Ij, Se ip and metal n/ ESCA lines, demonstrated pronounced a character in the M—O bond and a decrease in electron density on Se on coordination. A mass spectral study of chelates of Ni" and Cu" with the NBu 2-substituted form of the ligand, and analogues with Se substituted by O or S, demonstrated fragmentation of the M—O bonds to be easier than that of M—S or M—Se. ... 

In the ESCA investigations, 1.2-dichloroethane, which has a low relative permittivity ( =10.1), was used as the inert solvent. Solutions of antimony pentachloride in this were prepared, and the donor solvent was added in small amounts, so that one molecule of this should be bound at the sixth coordination site of the SbCls, but the relative permittivity of the system should not be increased appreciably. In this way it could be ensured that the SbCls did not dissociate even partially, and hence the change in the electron binding energies of the antimony on addition of the donor solvent could be attributed only to the coordination of this solvent (to the solvation of SbCls). 

Many valuable new results may be expected in this respect from the wider ranging application of electron paramagnetic resonance spectroscopy, NMR spectroscopy and solution X-ray examinations, and from the introduction of neutron diffraction and other diffraction methods in the chemistry of non-aqueous solutions. New possibilities in this field, which have by no means been fully exploited, are Mossbauer and ESCA investigations of rapidly frozen solutions. 

In agreement with this description a very recent ESCA investigation [91] on gold clusters [81] has shown that the gold atoms look rather equivalent, although they are not such from the geometrical point of view. Obviously a large electronic delocalisation takes place in these clusters. 

A number of commercial polychlorotrifluoroethylene products such as Fluorolube and Kel-F (oils, grease and powders) when used for machining aluminium yield explosive reactions under high shear loads. This kind of reactivity is rarely observed with pure fluorocarbons. Thus, it is assumed that the high reactivity stems from the chlorine connected to the polymer that is more easily abstracted than fluorine. In addition, thermal reaction between A1 and Kel-F oil has been observed at temperatures as low as 218 °C, whereas a fully fluorinated grease does not react until about 648°C [13]. Tribochemical-induced reaction between fluorocarbons and certain metals has been confirmed by Electron Spectroscopy for Chemical Analysis (ESCA) investigations on PTFE samples filled with both aluminium and zinc [14, 15]. 

M Osterhold, K Armbruster. Surface tension measurements and ESCA investigations on pretreated polymer samples. Farbe Lack 97 780-783, 1991. 

Photoelectron and E.S.C.A. Spectra. The diselenide structure of thiuram diselenides has been established by means of Rdntgenphotoelectron spectroscopy. The photoelectron spectra of thiocarbonyl halides have been studied and interpreted on the basis of CNDO calculations by two groups of workers. ESCA investigations have been performed on dithio-esters derived from active-methylene compounds and carbon disulphide, and on isocoumarins, thioisocoumarins, and isoquinolines containing the thiocarbonyl function." ... 

ESCA investigations were carried out on a M - Probe Surface Spectrometer SSX 100, Surface Science. HE ionically immobilised on cationised cellulose membranes was analysed quantitatively by means ofthe sulphur signal in the ESCA spectrum. Surface HE content was calculated from the peak integration of the sulphur peak. For increased ESCA sensitivity HE was labelled with pentafluorobenzyl bromide (PFB) or heptafluorobutylamine (HFB). Labelled HE was immobilised covalently to silicone and quantified by ESCA by means ofthe fluorine signal. 

Contrary to these results more than 90 % of the HE covalently attached to silicone were located at the surface as shown by comparising the ESCA and HPLC data. The amounts of HE bonded to the surface are in the same range as theoretically calculated for HE monolayers The ESCA investigations of surface modified silicone tubes were done with fluorine labelled HE derivatives to increase the ESCA sensitivity of the HE molecules. In the past fluorine containing labelling reagents have been used... 

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