N. A. Eissa

Mössbauer and ESR investigation of the behaviour of iron in vanadium borophosphate glasses

Mössbauer and ESR measurements were performed on vanadium borophosphate glasses containing iron. The glass composition was 78 mole% V2O5, 15 mole% P2O5, 7 mole% B2O3 and different amounts of Fe2O3 (0.5–50 mole%) were added. The relative percentage of iron in different states and site positions could be determined for each glass composition. Correlation between the behaviour of iron and its variation in structural units and other physical properties are proposed. A maximum amount of 33 mole% Fe2O3 could be incorporated in the glass network, higher concentrations lead to the precipitation of α-Fe2O3.

APPLICATION OF MOSSBAUER SPECTROSCOPY FOR: (1) CHARACTERIZATION OF EGYPTIAN MAGHARA COAL; (2) EVALUATING THE EFFICIENCY OF DIFFERENT METHODS FOR COAL DESULPHURIZATION

Coal has been recently discovered in Maghara mine at Northern Sinai, Egypt. Coal samples have been collected from different depths and were measured by XRD, XRF, and MS, in order to characterize this type of coal. It has been found that the iron bearing minerals are mainly pyrite and different sulphates depending on the depth of the sample. The second part contains the application of desulphurization techniques to Egyptian coal which are: floatation (one step and two steps) chemical [(HCl+HNO3), and Fe2(SO4)3] and bacterial methods (Chromatium and Chlorobium species). The efficiency of each technique was calculated. A comparative discussion is given of each desulphurization method, from which the bacterial method has proved to be the most efficient one.

Mössbauer, X-ray and derivatographic studies on Egyptian Nile clay

The constituents of the clay minerals in eighteen Nile clay and two Desert (calcareous) samples, were investigated. The physicochemical transformations induced in the iron containing phases were followed by heat treatment. A conclusion was reached about the behaviour of the ferrous and ferric ions at various temperatures. This behabviour is applied to characterize the archaeological Ancient Egyptian pottery.

Study of the high iron concentrations in cement clinker by Mössbauer spectroscopy

Determination par spectrometrie Mossbauer de la teneur en fer de clinkers obtenus a partir de melanges de matieres premieres contenant differentes teneurs en cendres de pyrite

Mossbauer effect study of the effect of gamma irradiation on the behaviour of iron in sodium silicate glasses

Abstract The effect of gamma irradiation on the behaviour of iron in a sodium silicate glass system [40 mol% SiO2, 60 mol% Na2O and 1–6 mol% Fe2O3] was investigated by Mossbauer effect (ME) and electron spin resonance (ESR) techniques. The changes in the quadrupole splitting (QS), line width of the ME spectra and the intensity of the g = 4.2 absorption line of the ESR spectra, showed that the distribution of the charges around the Fe nucleus became more symmetrical and less distorted than before irradiation. The change in the Fe-O interatomic distance due to gamma irradiation was determined using the overlap contribution to isomer shift (IS) for the Fe3+ ion in both tetrahedral and octahedral sites. The aging effect on the relaxation time of the electric field gradient (EFG) at the iron nucleus in irradiated glass showed that the relaxation time is increased and after certain period recombination of the defects occurred.

Mössbauer effect study of the effect of gamma irradiation and heat treatment on montmorillonite

Mössbauer spectroscopy was used to study the effect of gamma irradiation and heat treatment on montmorillonite. Samples were irradiated to gamma-ray doses ranging from 10 Gy up to 30 MGy. Other samples were heated to different temperatures from 400 ‡C up to 1350 ‡C. The lattice distortion caused by gamma irradiation could be followed. The phase transformations which occurred through and above the dehydroxilation temperature range could be traced and identified. The Mössbauer results were confirmed by X-ray diffraction results.

Study of magnetic properties and lattice dynamics of the Cd x Co1−x ferrite system by Mössbauer effect

The magnetic properties and lattice dynamics of the spinel ferrite system CdxCox−1Fe2O4 (x=0.0, 0.1,…, and 1) were studied in the temperature range between 78 K to 800 K. The results showed that the samples withx=0.0 up to 0.5 are antiferromagnetic at room temperature, and a magnetic disorder transformation started to appear atx=0.6. The Neel temperature was found to decrease with increasing cadmium concentration. The reduced hyperfine magnetic fields for A and B sites were found to follow the Brillouin function and One-Third-Power Law. The results showed that the introduction of the Cs2+ ions decreased thef-value and Debye temperature. The anisotropic energy, for 0.1≤x≤0.9 was found to be of the order of 2×10−21 J.

Mössbauer effect study of ancient Egyptian pottery

An exploratory survey of sherds of Egyptian pottery was performed with Mössbauer spectroscopy. The data show the presence of α-Fe2O3, ferrous and ferric components in different concentrations for sherds from different archeological times.

Effect of alkali ions on the strength development of cement paste by Mössbauer spectrometry

Two clinker raw mixtures (83 wt% limestone +12 wt% clay +5 wt% α-Fe2O3) were fired at 1150°C for three hours in open furnace, each with 100 wt%-in addition-of an alkali carbonate (Na2CO3 and K2CO3) respectively. Each produced cliker was mixed with 5 wt% natural gypsum to produce portland cement, then with 25 wt% tap water. Compressive strength, ultrasonic pulse test, X-ray diffraction and Mossbauer effect measurements were carried out each at different times of hydration (21, 28 and 45 days). The effect of alkali ions on the strength development of cement pastes is discussed, the accuracy of Mössbauer, spectrometer in determining the cement strength is demonstrated.

Application of Mössbauer spectroscopy in investigating Egyptian archaeology

This article summarizes the results of applications of the Mössbauer spectroscopy to investigate Ancient Egyptian pottery from the periods: Ancient Egyptian (3200–525 B.C.) Greek-Roman (320 B.C.–640 A.C.) and Early Islamic (800–1000 A.C.). Many objective informations deduced about: provinance, manufacturing techniques for different domestic purposes, civilization transfer between the Arab countries, methods of colouration and applying decorating glazes, and finally dating of ancient pottery.