Isothermal investigation of decomposition of FeSO4·H2O-BaO2 mixtures

Isothermal studies were conducted on mixtures of Fe₂SO₄·H₂O in BaO₂ in molar ratios ofn=4, 2 and 1 at temperatures of 573 and 1073 K, in a closed crucible, in air as gas medium. The solid products of decomposition were investigated by means of X-ray analysis, Mössbauer spectroscopy and electron spectroscopy.The experiments revealed that the mechanism of the process is connected with the formation of different quantities of barium ferrites (BaFeO₃, BaFe₂O₄ and BaFe₁₂O₁₉), as well as BaSO₄ and Fe₂O₃, depending on the quantity of BaO₂ in the initial mixture, the partial pressure of the gas components and temperature. Differences were found in the mechanism of the process for the same mixtures under dynamic temperature conditions.     

The six-point families of exceptional representations of the conformal group

Six-point families of topological reducible (indecomposable) representations of the conformal group of space-time M ₄ are studies. The structure of invariant subspaces is analysed and the full set of equivalence relations among the suprepresentations is derived.     

On the decomposition of FeSO4 in the presence of FeS2 and BaO2

FeSO₄ is a waste obtained in the production of TiO₂ and also in steel etching in block metallurgy. The thermochemical decomposition of different FeSO₄-FeS₂-BaO₂ mixtures was studied by means of a derivatograph, X-ray diffraction, Mössbauer spectroscopy, EMF and other methods in order to understand the chemical transformations, new solid phases and kinetic limitations in the temperature range 292 – 1292 K. It was shown that there is a multistep process in which BaSO₄, FeS, BaFeC₃ and BaFe₂O₄ can be formed as intermediates. Depending on the initial ratio of the components, the atmosphere and the temperature range, different phase compositions of the final solid product can be obtained. At the present stage of the investigations, the possibility of obtaining pure barium ferrite as a product is not confirmed.

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Zusammenfassung FeSO₄ ist ein Abfallprodukt aus der Herstellung von TiO₂ und aus dem StahlÄtzen in der Blockmetallurgie. Mittels Derivatographie, Röntgendiffraktion, Mössbauerspektroskopie, EMF und anderen Methoden wurde die thermochemische Zersetzung verschiedener FeSO₄-FeS2-BaO₂-Gemische untersucht, um chemische Umformungen, neue Festphasen und kinetische Grenzen im Temperaturbereich 292–1292 K zu verstehen. Es wird die Existenz eines mehrstufigen Prozesses gezeigt, in dem BaSO₄, FeS, BaFeC₃ und BaFe₂O₄ als Zwischenprodukte geformt werden können. In AbhÄngigkeit von dem AusgangsverhÄltnis der Komponenten, der Zusammensetzung der AtmosphÄre und des Temperaturbereiches können für das feste Endprodukt verschiedene Phasenzusammensetzungen erhalten werden. Im gegenwÄrtigen Stadium der Untersuchungen konnte die Möglichkeit von reinem Bariumferrit als Produkt nicht bestÄtigt werden.

     

A new semilocal convergence theorem for the Weierstrass method for finding zeros of a polynomial simultaneously

In this paper we study the convergence of the famous Weierstrass method for simultaneous approximation of polynomial zeros over a complete normed field. We present a new semilocal convergence theorem for the Weierstrass method under a new type of initial conditions. Our result is obtained by combining ideas of Weierstrass (1891) and Proinov (2010). A priori and a posteriori error estimates are also provided under the new initial conditions.     

Thermochemical characterization of chicken litter and peat as a source for energy recovery

The shortage of raw materials and the environmental problems due to pollution require development of new green technologies utilizing some wastes and transforming them to secondary raw materials. The aim of this work is to study the properties of poultry waste to propose possibilities to minimizing the released emissions and avoiding the risk for human health and the environment. At the same time, two types of low grade peats with different origin are studied as components for the production of soil conditioners. During the studies, we applied the inductively coupled plasma (ICP) and chemical analysis, powder X-ray diffraction, thermal analysis, IR spectroscopy, and scanning electron microscopy for determining the composition, crystal phase, the shape and size of particles, and thermal stability of the investigated samples. The chemical and the phase compositions of the studied samples confirmed that the content of nutrient compounds and of the carbon substances is suitable as an effective secondary raw material for soil conditioners. It is found that the poultry wastes and peat samples have a similar phase and chemical composition and contain an organic mass in the form of carbon components with amorphous, fibrous, and skeleton-like structure, suitable to be combined with other nutrient-containing compounds. During the thermal treatment, the carbon compounds are oxidized releasing heat. Based on that the materials under study are considered as environmentally friendly fuels, releasing relatively low emissions.     

Preparation and optical properties of samarium doped sol-gel materials

Transparent crack-free glassy monoliths containing up to 0.2 Sm/Si are prepared at room temperature by sol-gel technique. The sol-gel preparation conditions are: acid catalyzed hydrolysis followed by basic catalyzed gelation and controlled drying. The prepared xerogels are characterized by X-ray diffraction, thermogravimetry with Fourier transforming infrared spectroscopy, scanning electron microscopy and optical spectroscopy. The values of the phenomenological Ω-intensity parameters of Sm(III) ions in the gels are (in 10⁻²⁰ cm²) Ω₂ = 76 ± 16.71, Ω₄ = 3.01 ± 0.21, Ω₆ = 2.99 ± 0.41. The oscillator strengths of the Sm(III) ions in the gels are calculated. The results show a linear concentration dependence of Sm(III) in UV/Vis absorption spectra and formation of a Sm(NO₃)₃ · 6H₂O complex at high samarium concentrations.     

Group-Theoretical Approach to Extended Conformal Supersymmetry: Function Space Realizations and Invariant Differential Operators

We give function space realizations of all representations of the conformal superalgebra su(2,2/N) and of the supergroup SU(2, 2 /N) induced from irreducible finite-dimensional Lorentz and SU(N) representations realized without spin and isospin indices. We use the lowest weight module structure of our su(2,2/N) representations to present a general procedure (adapted from the semisimple Lie algebra case) for the canonical construction of invariant differential operators closely related to the reducible (indecomposable) representations. All conformal supercovariant derivatives are obtained in this way. Examples of higher order invariant differential operators are given.