Thermal decomposition of natural siderite and goethite has been studied using Mössbauer spectroscopy and X-ray diffraction. Hematite and magnetite were the principal compounds formed during high temperature treatment of siderite. Natural goethite transformed to hematite at high temperatures. The crystal structures, stoichiometry and the nuclear magnetic properties of Fe-oxides formed are discussed.
Thermal decomposition of iron(II) acetate, Fe(CH3COO)2, and iron(III) acetate hydroxide, FeOH(CH3COO)2, has been studied using57Fe Mössbauer spectroscopy and X-ray diffraction. Samples were thermally treated in air atmosphere between 150°C and 1000°C. The formation of maghemite '-Fe2O3, and hematite, -Fe2O3, is discussed. Hematite appears as the final decomposition product.
The denitration of several chemical compositions of simulated HRLW (highly radioactive liquid waste) was performed using formic acid as reducing agent. Precipitates formed during the denitration of simulated HRLW were analyzed using X-ray diffraction and57Fe Mössbauer spectroscopy. Goethite and amorphous fraction were the principal phases in these precipitates. It was found that the chemical composition of simulated HRLW and the experimental conditions of denitration have more influence on the crystallinity and the particle size than on the phase composition of the precipitates. Thermal treatment of denitrated precipitates caused the solid state transformation of goethite+amorphous fraction into hematite. The values of hyperfine magnetic field (HMF) of hematite were decreased, thus indicating the substitution of Fe3+ ions with other metal cations.
The effects of iron on the structural properties of Zn-borosilicate glasses have been studied using X-ray diffraction, IR spectroscopy and57Fe Mössbauer spectroscopy. Zn-borosilicate glasses were doped with –Fe2O3. In the systems Na2O–ZnO–B2O3–SiO2–Fe2O3 the presence of only one crystalline phase, ZnFe2O4, was detected. X-ray diffraction showed that crystallization is more pronounced in the systems ZnO–B2O3–SiO2–Fe2O3. In these systems the presence of different crystalline phases, such as ZnO, –Fe2O3, Fe3O4, ZnFe2O4 and Fe3BO5, was detected. The crystallization of –Zn2SiO4 in the system ZnO–B2O3–SiO2 was confirmed by X-ray diffraction and IR spectroscopy. The valence state and coordination of iron in Zn-borosilicate glasses were determined by57Fe Mössbauer spectroscopy.
Thermal decomposition of natural pyrite (cubic, FeS2) has been investigated using X-ray diffraction and57Fe Mössbauer spectroscopy. X-ray diffraction analysis of pyrite ore from different sources showed the presence of associated minerals, such as quartz, szomolnokite, stilbite or stellerite, micas and hematite. Hematite, maghemite and pyrrhotite were detected as thermal decomposition products of natural pyrite. The phase composition of the thermal decomposition products depends on the temperature, time of heating and starting size of pyrite crystals. Hematite is the end product of the thermal decomposition of natural pyrite.
Authors:S Popovic, S Popovic, S Popovic, N Arsenijevic, N Arsenijevic, N Arsenijevic, D Baskic, D Baskic, and D Baskic
assays for the quantification of apoptotic cells uptake by phagocytes have
several methodological problems. Our assay overcomes some of these problems.
As a source of apoptotic cells we used peripheral blood lymphocytes obtained
from the patients with chronic lymphoblast leukaemia. Apoptosis was induced
by incubating cells with cycloheximide for up to 24 h. The assay was
performed in suspension of peripheral blood mononuclear cells. For the visualisation of the phagocytes and
phagocyted cells and discrimination of phagocyted from bound apoptotic cells
we used Acridine orange/Ethidium bromide double staining. Here we offer a
simple test which enables reliable measurement and it can show the difference
of phagocytic potential between different individuals
A new method for the analysis of thermal desorption spectra is presented, based on the experimental peak maximum functions
for temperatureTm(β) and pressurePm(β) and a rigorous mathematical treatment. The resonant heating rate βr is determined, satisfyingTm(βr)=Tr, whereTr is the resonant temperature defined byA exp(−Ed/(RTr))=1. Desorption energyEd and frequency factorA can be determined simultaneously with relatively high robustness towards statistical experimental errors as demonstrated
by computer-simulated thermal desorption spectra.
Authors:M. Ellid, Y. Murayed, M. Zoto, S. Musić, and S. Popović
Chemical reduction of hematite with starch in air at elevated temperature was investigated using X-ray powder diffraction, FT-IR and 57Fe Mössbauer spectroscopies. On heating the starting mixture for 0.5 and 2 hours at 300 °C, magnetite and a small fraction of hematite were identified by XRD. With the heating time prolonged up to 24 hours, magnetite reoxidized and hematite was obtained again. The formation of magnetite was observed even at 580 °C. However, the magnetite formed at this temperature was substoichiometric, as shown by XRD and Mössbauer spectroscopy. Characteristic IR bands of oxide phases were monitored by FT-IR spectroscopy. Chemical reduction of hematite with starch into a Fe0 state was not observed in any sample.
Authors:S. Musić, M. Gotić, S. Popović, and B. Gržeta
The effects of iron on the structural properties of Zn-borosilicate glass and Pb-metaphosphate glass were studied using X-ray diffraction,57Fe Mössbauer spectroscopy and IR spectroscopy. Zn-borosilicate glass was prepared with varying amounts of Fe2O3 (up to 30% wt.). It was found that the chemical form of added iron (-FeOOH, -Fe2O3 or Fe3O4) affects the Fe3+/Fe2+ ratio, as well as the distribution of iron ions at different coordination sites. At high concentration of iron the crystallization of zinc ferrite in the glass matrix takes place. X-ray diffraction and57Fe Mössbauer spectroscopy showed that the amount of zinc ferrite in Zn-borosilicate glass decreases with the following order of addition: -FeOOH
Fe3O4. In Pb-metaphosphate glass doped with high concentration of -Fe2O3, the crystallization of Fe3(PO4)2 is pronounced. The assignments of IR band positions and the corresponding interpretation are given. The importance of this study for the technology of vitrification of high-level radioactive wastes is emphasized.
Authors:J. G. Popovic, L. Katsikas, and J. S. Velickovic
The non-oxidative thermal degradation kinetics of poly(di-n-alkyl itaconates), ranging from the methyl to then-octyl derivatives, were studied by non-isothermal and isothermal TG. The thermal degradation activation energy and characteristic mass loss temperatures were found to decrease with increasing substituent size. The shapes of the DTG curves were dependent on the size of the alkyl substituent. The different DTG maxima were ascribed to various modes of initiation of depolymerisation. The thermal stability of poly(di-n-hexyl itaconate) was found to be independent of the initial molar mass of the sample in the range ofMw from 104 to 107 g/mol.