Search results for "Conversion electron mössbauer spectroscopy"
showing 9 items of 19 documents
Observation of substitutional Fe in CEMS measurements on synthetic CVD diamond
2004
Conversion electron Mossbauer spectroscopy measurements have been made on a diamond sample synthesized by chemical vapour deposition. The sample was implanted with 70 keV 57Fe to a dose of 5 × 1014 cm−2 and Mossbauer measurements were made on the as-implanted sample and after annealing at temperatures of 600 K, 950 K and 1470 K. The spectra at the lower temperatures were characterized by broad doublets, but the annealing at 1470 K resulted in dramatic decrease in the intensity of the doublet components, and the appearance of a strong single line with an isomer shift of δ = −0.90(5) mm/s and areal intensity of 30%, and a weaker line (5%) with δ = +0.07(4). Arguments are presented to attribut…
Optimization of a conversion electron Mössbauer spectroscopy gas flow He/CH4 proportional counter
1992
A new detector for CEMS has been built and optimized with respect to the statistical quality of spectra obtained. The optimization has been performed by measuring Mosbauer and pulse height spectra at in- and off-resonance. Single channel analyzer settings were calculated by a new optimization routine. A comparison of different detector designs has been performed using the statistical utility rate of spectra obtained from a stainless steel foil. A procedure for determining optimal operating parameters for ICEMS gas flow proportional counters is proposed.
Corrosion processes and their inhibition as studied by Mössbauer conversion and other electron spectroscopies
1989
To study corrosion processes of iron and steel and measures of their inhibition, a detailed knowledge of the phase composition and of phase transformations in very thin layers close to the attacked surface of the material is necessary. The information depths of integral (ICEMS) and depth selective (DCEMS) conversion electron Mossbauer spectroscopy are well suited for such investigations, but some effort is necessary if technical samples, i.e. nonenriched in57Fe, are to be studied. In many cases of practical importance, full information on the corroded surfaces cannot be got from Mossbauer spectra only, and a combination with Auger and photoelectron spectroscopies, in-including scanning and …
Icems and dcems study of Fe layers evaporated onto Al and Si
1990
Thin layers of57Fe (2.5 nm, 10 nm and 70 nm thickness), vacuum evaporated onto Al and Si plates, have been investigated by conversion electron Mossbauer spectroscopy (CEMS). The measurements were performed employing both a proportional counter and a channeltron for conventional and ultrahigh-vacuum integral CEMS (UHV-ICEMS) studies, respectively, and a channeltron for depth-selective CEMS (DCEMS). The phase analysis of the layers on base of experimental results has indicated the presence of metallic iron and one or two iron compounds, ascribed to iron reaction products formed with the residual gas during evaporation. These products are most likely rather stable iron nitrides, are more or le…
Conversion-electron M�ssbauer spectroscopy using 121Sb and a study of powdered ?-Sb2O3
1994
It is shown that 121Sb Conversion-Electron Mossbauer Spectroscopy (CEMS) is possible even at room temperature. The parameters and peculiarities of 121Sb CEMS are summarized. An application to powdered Sb(III) oxide shows that the material on the surface of the grains is not oxidized to Sb(V) but has changed its crystal symmetry, while the bulk of the grains still exhibits the initial cubic-crystal phase.
Problems of electron detection in Depth-Selective Conversion Electron Mössbauer Spectroscopy
1992
Applications of Depth-Selective Conversion Electron Mossbauer Spectroscopy (DCEMS) are limited by the long measuring times needed for collecting sufficient data statistics. To shorten the recording time, the background should be reduced and the detection efficiency for conversion electrons should be improved. For57Co/57Fe DCEMS, systematic studies were performed to investigate the origin, shape, and structure of the background components in DCEMS data distributions for various samples using channeltrons and low-noise scintillation counters as electron detectors.
Surface versus bulk composition of a phosphate glass
1994
Transmission and conversion electron Mossbauer spectroscopy as well as photoelectron spectroscopy were applied to study alterations of the surface layer of an iron containing industrial phosphate glass as compared with its bulk. In the surface layer, after polishing and exposure to ambient atmosphere, Fe 2+ is partially oxidized to Fe 3+ . This oxidation, however, does not increase the O/P ratio in this layer, because it goes along with a strong leaching of network modifiers. This leaching leads to a net decrease of the O/P ratio because it overcompensates the relative oxygen increase by Fe 2+ oxidation and by uptake of water
Formation, phase composition, and transformations of Langmuir-Blodgett multi- and monolayers containing Fe
1992
Mono- and multilayers of ferric stearate were formed by the Langmuir-Blodgett technique. Thermodesorption of the hydrocarbon chains results in well defined thin oxidic films. Their reduction to Fe2+ and α-Fe was followed by conversion electron Mossbauer spectroscopy. Resonance lines can be observed even if the Fe coverage is less than one monolayer.
A Mössbauer study of the crystalline structure of the passive film formed on iron in aqueous sulfate solution containing sulfite in low concentration
1993
Electrochemically induced passivation of evaporated, enriched 57Fe in 0.5 mol dm−3 Na2SO4 + 0.001 mol dm−3 NaHSO3 aqueous solution (pH 6.5) was followed by conversion electron Mossbauer spectroscopy. The transformation of amorphous iron oxide or hydroxide into crystalline γ-FeOOH could be observed with the increase of the polarization time. The comparison of the original quantity of evaporated, enriched 57Fe layer on the surface of the samples with the dissolved iron, measured in the solutions after the polarization, proved the existence of pitting corrosion at this pH.