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Abstract  

57Fe Mössbauer measurements were performed on FeSO3 being in frozen solution and in crystalline states. The obtained typical Mössbauer parameters for crystalline FeSO3.3H2O are IS=1.23±0.05 mm s–1 and QS=2.50±0.01 mm s–1, while for the fozen solution: IS=1.32±0.01 mm s–1, QS=3.24±0.01 mm s–1. It show that FeII is hexaaquacoordinated in the solution.

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Abstract  

Integral electron Mössbauer spectroscopy (ICEMS) and additionally some electrochemical methods were used to characterize the passivation process of iron (low carbon steel) in sulfate, sulfate+sulfite (a possible model solution of acid rain) solutions and in phospate buffer. The phase compositions and thicknesses of the passive layers formed due to the electrochemical polarizations were analyzed in dependence on the duration of the anodic passivations and on the pH of the used electrolytes. The passive layer, as determined from the Mössbauer spectra, consists mainly of -FeOOH, however in sulfite containing sulfate aqueous solution at pH 3.5 Fe3C and despite ex-situ circumstances FeSO4·H2O was detected after the shortest polarization time. The film thickness, which was found to grow nearly linearly with polarization time in pure sulfate solution and in phospate buffer, reached a maximum of 60–160 nm (depending on pH) in sulfate+sulfite solution after a passivation time of about 4 hours. It has been proved, that HSO3 -ion, which is contained by acid rain, initiate pit formation under acid conditions and so enforces the corrosion of iron. The experimental results furthermore suggest, that not the whole oxidic layer is responsible for the passivity but only a very thin intermediate layer formed between an inner oxide layer of a cubic structure and the rhombic oxide (-FeOOH) cover.

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Abstract  

Positron lifetime measurements were carried out on pyrophyllite-1 Tc before and after heat treatment, chlorination and HF treatment. The lifetime spectra gave information about the changes of the defect structure of pyrophyllite due to the different treatments.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: K. Süvegh, Cs. Szeles, A. Vértes, M. White, and H. Leidheiser

Abstract  

The implantation of positrons from a22Na source has been studied in two polymer coatings. Transmitted intensities, effective mass absorption coefficients and implantation profiles have been determined.

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Abstract  

Conversion electron Mössbauer spectroscopy (CEMS) and XPS has been used for the surface analysis of an X10CrNiTi 18/9 (DIN 1.7440)-type stainless steel in order to determine the supposed structural and/or chemical changes in the surface layer caused by polishing. Both, CEMS and XPS results can be associated with the appearance of Fe nitride in the outer layer of steel samples after polishing, while no sign of nitrogen was detected in the bulk material.

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Abstract  

A special Mössbauer technique, MMS has been used for the study of corrosion on the surface of57Fe layers, under two types of organic coatings. The corrosion processes were followed by the Mössbauer spectra.

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Abstract  

A stacking Mössbauer technique, MMS has been applied for studying thin surface layers. The surface layers formed on the57Fe film in aqueous solutions of corrosion inhibitors, such as zinc phosphate and barium metaborate, and in distilled water was studied by this method. It has been found that the corrosion is much slower in the presence of zinc phosphate and barium metaborate. XPS analysis suggests the formation of a mixed iron zinc phosphate on the surface of the57Fe film after corrosion in a zinc phosphate solution.

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Abstract  

Samples of TiN hard coatings prepared by physical vapour deposition (PVD) were investigated by means of depth-sensitive positron annihilation spectroscopy. The results indicate that the samples are at the limits of the applicability of this method presumably due to the high defect concentration. Our findings also show that, though the samples are thoroughly characterized by other independent methods, they might not be sufficient to explain all aspects of positron-solid interactions in these cases.

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Abstract  

We studied the long-term (190 hours) behaviour of [Zn(propyltetrazole)6](BF4)2 single crystal under high-vacuum (HV) conditions (10–8 torr) with a depth-sensitive technique of positron annihilation spectroscopy (PAS). The obtained data indicate the slow formation of a new near-surface structure which is formed by the decomposition of the [Zn(propyltetrazole)6]2+ ions. The assumption of such a decomposition process was confirmed by additional mass spectroscopic measurements.

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Abstract  

Mössbauer spectroscopy was used to study phlogopites from ultramafic xenoliths derived from alkali mafic rocks of the Transdanubian Midmountains. On the basis of evaluation of the Mössbauer spectra the following iron sites were identified /using the nomenclature published by Dyar1/ in the samples:

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$Fe_{M1}^{2 + } , Fe_{M2}^{2 + } , Fe_{M3}^{3 + } and Fe_{tet}^{3 + } .$$ \end{document}
Quantitative analysis of all of the iron sites was performed. The Fe2+/Fe3+ ratio was found to be 3.33 for the sample for phlogopite xenolith and 2.05 for the sample from clinopyroxene-phlogopitite xenolith. There are evidences, that Fe3+ can occupy tetrahedral positions in upper mantle phlogopite, even if Si+Al>8. Our data suggest MARID+ glimmerite origin of micas.

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