Search Results
You are looking at 11 - 20 of 88 items for
- Author or Editor: A Vértes x
- Refine by Access: All Content x
Abstract
57Fe transmission Mössbauer spectroscopy and X-ray diffractometry were used to study clay mineral samples originated from two different regions (Um-arrazm and Alkawasim) of Libya in order to get information about their mineralogical composition to assess their potential for use in the Libyan oil industry. In the samples originated from Um-arrazm calcite, akaganeite and nontronite while in the samples originated from Alkawasim quartz, akaganeite, montmorillonite, kaolinite, illite, mica and hematite were identified with different ratios by using diffraction method. The differences in the phase composition of iron-containing phases of samples from different localities have reflected in the complex Mössbauer spectra at both 300 K and 80 K. For the samples originated from Um-arrazm the Mössbauer parameters of subspectra were identified as nontronite and akaganeite.
Abstract
Cobalt—tin alloys electrocodeposited from a mildly alkaline sulfate bath were studied using119Sn absorption and57Co Emission Mössbauer Spectroscopy. The Results reveal that dissolved tin and cubic CoSn (not appearing in the phase diagram) are the components obtained from fresh plating solutions. Upon exhaustion, the formation of 
Co3Sn2 is favoured, with the eventual deposition of cobalt particles as a separated phase. A precipitate is formed during bath operation which is richer in Sn(II), contrasting to the mother solution which is richer in Sn(IV).
Abstract
Positron lifetime measurements have been performed on differently manufactured PEEK samples of different molecular weights. Our measurements confirmed an old assumption: the o-Ps lifetime changes linearly with the molecular weight of the polymer. We have found that both the size of the free volumes and their number increase with increasing molecular weight of the investigated polymers.
Abstract
A new terminology of Mössbauer pattern analysis is introduced. In this approach Mössbauer parameters are considered as functions of a number of externally adjusted physical parameters at which the spectrum has been recorded. Our approach can also help to systematize Mössbauer data for the identification of individual physical or chemical species from the corresponding patterns present in the spectrum.
Abstract
For the electrodeposition of119Sn, aluminium, iron, nickel, copper, silver and platinum foil substrates were used. The samples were measured before and after heat-treatments between 350–485 K. In several cases interphase formation was observed even before the first heat treatment. Diffusion data were alsc obtained.
Abstract
A new user-friendly software for analysis of Mössbauer-spectra has been developed. The program makes use of the advantages provided by the current generation of fast personal computers. An Evolution Algorithm1,2 is used for global search of Mössbauer parameters in order to enhance the reliability of the obtained results. Fitting of Lorentzians, Pseudo-Voigt line profiles, and deriving hyperfine-field distributions including correlations and combinations and Mössbauer Line Sharpening by Fourier transformation provide a wide range of applicability.
Abstract
Investigations of the possible use of Mössbauer measurements for the analysis of the corrosion products of iron are reported. The Mössbauer spectrum was measured at room and liquid nitrogen temperatures on two samples produced by different corrosion procedures. The isomeric shift, quadrupole splitting and magnetic splitting observed in the spectra yield information on the chemical composition. In this way, the chemical forms of the compounds in the samples could be established. The magnetic properties, revealed by the spectra taken at different temperatures, permitted the identification of the polymorphous modifications. The rust produced in air saturated with water vapour was found to consist of 50% (w/w) Fe2O3,∼40% γ-FeOOH, and ∼10% β-FeOOH, while the rust produced by periodical immersion in saturated calcium chloride solution is composed of about equal amounts of β-FeOOH and γ-FeOOH. These findings have been confirmed by the thermoanalytical curves of the samples. The Mössbauer effect presents a convenient method for the investigation of the corrosion products of iron.
Abstract
Phase composition of Co-promoted ammonia synthesis catalysts has been studied by means of Mössbauer spectroscopy and X-ray diffractometry. Co-promoted catalysts have maximum activity at 5–7% CoO concentration. This result is associated with the substitution of 1–2 Fe atoms by Co-atoms per unit cell of the bcc 
-Fe lattice being the active phase for catalysis.
Abstract
The crystallization kinetics of Fe83P17 amorphous alloy has been studied by Mössbauer spectroscopy and X-ray diffractometry. The samples were annealed isothermally at two different temperatures (315 °C and 325 °C). During isothermal annealing of the samples three phases were observed: crystalline Fe3P phase, crystalline 
-Fe phase and the amorphous phase. The value of the Avrami exponent was found to be about 2.0 at each annealing temperature. This suggests that the growth rate of the crystals is controlled by volume diffusion and the nucleation rate decreases during crystallization. The activation energy obtained for the overall crystallization process was 193±43 kJ mol–1.
