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  • Author: Jacek Szczerba x
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Abstract

Magnesium oxide (MgO) is one of the most important raw materials in many branches of industry. Magnesium oxide is a popular refractory raw material because of its high refractoriness and high resistance to basic slags and environment. In many cases, use of MgO is limited by its properties, especially the presence of secondary phases like iron oxides. The amount and distribution of iron oxides can strongly influence the technological properties of MgO and depend on the manufacturing method, particularly the heat-treatment process. The aim of the study was to evaluate the influence of the heat-treatment process on amount and distribution of iron ions in a magnesium oxide lattice. The 57Fe Mössbauer effect measurements of fused and sintered magnesium oxide samples doped by the iron oxide were conducted. Investigation reveals in both cases the presence of Fe2+ as well as Fe3+ ions. Fe2+ ions occupy Mg2+ octahedral sites in the MgO lattice, whereas the Fe3+ ions are located in highly distorted octahedral coordination. The amount of Fe2+ varies from around 66% for fused samples to 30% for sintered samples.

Abstract

The aim of the study was to characterize the 0.8CaZrO3-0.2CaFe2O4 composite structure with particular emphasis on the role and position of iron in the function of sintering temperature. The paper presents the results of 57Fe Mössbauer effect at room temperature. It was found that the increase of sintering temperature causes an increase in the amount of incorporated iron ions in the CaZrO3-crystal structure. Based on Mössbauer spectroscopy analysis, it was found that three different environments of Fe3+ ions were observed in the obtained materials. Two of them corresponded to CaFe2O4 phase and one was associated with the substitution of Zr4+ by Fe3+ in the CaZrO3 structure.

Abstract

In this work spinel series with the general formula Fe1-xMnxAl2O4 (where x = 0, 0.3, 0.5 and 0.7) were synthesized and characterized with respect to their structure and microstructure. X-ray diffractometry (XRD) was used to identify the phase composition that revealed a single phase spinel material. Rietveld refinements of the XRD patterns were carried out in order to determine the lattice and oxygen positional parameters of the spinel compounds. Mössbauer effect measurements were performed at room temperature to determine the local chemical environment of the Fe ions, their valences, and degrees of spinels inversion. It was shown that an increase in the Mn content led to a decrease in the ratio of Fe2+ to Fe3+. The results obtained from Mössbauer spectroscopy (MS) were used to establish the chemical formulas of the synthesized spinels. Finally, the microstructure that was observed using scanning electron microscopy (SEM) showed a compact microstructure with an octahedral crystal habit.

Abstract

In this work the synthesis of hercynite from Fe2O3 and Al2O3 powders was carried out by arc-melting method under the protective argon atmosphere. The obtained material was characterized with the use of powder X-ray diffractometry (XRD) and Mössbauer spectroscopy (MS). A Mössbauer effect in hercynite obtained by the arc-melting method indicated the cations distribution in the spinel structure among the tetrahedral and octahedral interstices. The presence of Fe2+ ions was detected in both tetrahedral and octahedral sites while Fe3+ ions occupied only the octahedral interstices. The approximate formula of the obtained iron-aluminate spinel was as follows (Fe2+ 0.77Al3+ 0.23) (Fe3+ 0.07Fe2+ 0.05Al0.88)2O4.