Search Results
You are looking at 21 - 30 of 88 items for
- Author or Editor: A Vértes x
- Refine by Access: All Content x
Abstract
The Mössbauer spectra of quenched aqueous iron(III) salt solutions containing HClO4, H2SO4, HCl, respectively, were measured. The magnetic hyperfine structure of the spectra was studied as a function of the change of acid and iron concentrations. In the solutions of FeCl3 containing 8.5N HCl we suppose the presence of octahedral [FeCl4(H2O)2]− complex.
Abstract
Positron lifetime measurements were performed to study the swelling dynamics of an amphiphilic polymer network (APN). Lifetime spectroscopy proved to be suitable to investigate APNs. Very quick structural changes were indicated by lifetime parameters at very low swelling ratios. On the basis of the results a possible mechanism is proposed for the hydration of the investigated materials.
Abstract
The donor strength of oxygen atoms in the Si−O−C and Si−O−Si groups has been studied by Mössbauer spectroscopy, using SnI4 as acceptor. At 80 K trimethylalkoxysilanes and the disiloxanes studied show characteristic isomer shifts on the basis of which the existence of pentacovalent SnI4·D and hexacovalent SnI4·D2 may be assumed. The changes in isomer shift due to the first and second oxygen atoms are −0.60 and −0.55 mm/sec, respectively. The coordination number is determined by the steric requirements of the donor relative to the coordination sphere of the acceptor, provided that the donor strength is sufficiently high. No donor-acceptor interactions have been observed with compounds of the-(OSiR2)-O-type. In the case of hexamethyldisiloxane, iodine is displaced from the coordination sphere. No quadrupole splitting has been observed in any of the cases studied. Thus the ratio of point charges assignable to the iodine and the donor oxygen atom is 6:1 for the trigonal bipyramidal arrangement; for a tetragonal pyramidal structure the angle between the xy plane and the Sn−I bond is ∼35°.
Abstract
The 57Fe Mössbauer spectrum of Kaba (Hungary) meteorite was recorded at room and at liquid nitrogen temperatures. The evaluation of the spectrum showed that the iron containing components of the Kaba meteorite are magnetite, maghemite, troilite, fayalite and pentlandite.
Abstract
Liquids and solutions containing Mössbauer active isotopes when trapped in the capillaries of porous silicate glasses show the Mössbauer effect1 also at room temperature2,3. A model is given for the explanation of this phenomenon.
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.
Abstract
Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.
Abstract
Radioactive as well as inactive cobalt precipitated from an aqueous solution onto the surface of 
-Fe2O3 was investigated by the Mössbauer spectroscopy of57Fe. The experiment performed with the57Co-doped sample showed that some of the cobalt atoms diffused into the -Fe2O3 lattice owing to 1 h of heat treatment carried out at 300 °C.
Abstract
Mössbauer spectroscopy was used in order to get information about the anomalous austenite formation1 taking place between 450–600 °C in steel containing 12%Cr and 4%Ni. Even below the equilibrium transition temperature (640 °C) of 
transformation a monotonic increase of the relative spectral area of the line belonging to austenite was observed in the Mössbauer spectra of the steel isothermally aged at 550 °C with increasing ageing time. At the same time, the Cr content of the ferrite phase decreases. Time dependence of the quantity of austenite formed during the isothermal ageing follows the Avrami-kinetics with an exponent n=0.3.
Abstract
Positron lifetime measurements were carried out in normal hexane vs. temperature in the range of 12.5–62.5°C. The evaluation of the lifetime spectra indicates the presence of four lifetime components, as published first by Jacobsen et al. An attempt is made to interprete the properties of the longest-living two components in terms of the microscopic structure of the liquid.
