Phase equilibria in the quaternary systems Li‖F,Cl,Br,CrO4 and Li‖F,Cl,Br,WO4

Phase equilibria in the quaternary systems Li‖F,Cl,Br,CrO₄ and Li‖F,Cl,Br,WO₄ were studied by differential thermal analysis. In these systems, the stability of continuous series of solid solutions based on lithium chloride and bromide is preserved. The number and compositions of crystallizing phases in the systems Li‖F,Cl,Br,CrO₄ and Li‖F,Cl,Br,WO₄ were confirmed by X-ray powder diffraction analysis.     

Investigation of phase diagrams by DTA and X-ray methods: The systems AX/CoX2 (A = Na-Cs,TI;X = Cl,Br, I)

A combination of differential thermal analysis and X-ray structure analysis is advantageously used to investigate the formation of double halides in complicated systems betweeen alkali halides, AX, and divalent halides, MX₂. Among the systems of CoX₂ (X = Cl, Br.I) this is particularly valid for the systems TICI/CoCl₂ and TlBr/CoBr₂.     

Dependence of the Physicochemical and Catalytic Properties of Ce<Subscript>0.5</Subscript>Zr<Subscript>0.5</Subscript>O<Subscript>2</Subscript> Oxide on the Means of Synthesis

The effect the means of synthesis have on the texture, phase composition, redox properties, and catalytic activity of binary oxide systems with the composition Ce_0.5Zr_0.5O₂ are studied. The obtained samples are characterized via BET, SEM, DTA, XRD, and Raman spectroscopy. A comparative analysis is performed of the physicochemical properties of biomorphic systems Ce_0.5Zr_0.5O₂ obtained using wood sawdust and cellulose as templates and the properties of binary oxides of the same composition obtained by template-free means. The catalytic properties of the obtained oxide systems Ce_0.5Zr_0.5O₂ are studied in the reaction of carbon black oxidation. It is shown that the texture of the oxide depends on the means of synthesis. When biotemplates are used, fragile porous systems form from thin binary oxide plates containing micro-, meso-, and macropores. Oxide obtained via coprecipitation consists of dense agglomerates with pores around 30 Å in size. In supercritical water, nanoparticles of metal oxide form that are loosely agglomerated. The intermediate spaces between them act as pores more than 100 Å in size. A system of single-phase pseudocubic modification is obtained using a cellulose template. The crystal lattices of all the obtained systems contain a great many defects. It is shown that the system prepared via synthesis in supercritical water has the best oxygen-exchange properties. A comparative analysis is performed of the effect the physicochemical properties of the samples have on their activity in the catalytic oxidation of carbon black.     

Influence of nickel content on catalytic activity and stability of the systems, based on intermetallic Ni3Al in the conversion of natural gas using carbon dioxide

In CO₂ reforming of methane catalytic systems based on Ni₃Al with various nickel and aluminum content were investigated. Catalysts were obtained using the self-propagating high-temperature synthesis. The XRD technique was used to investigate the phase content of the studied systems. It was demonstrated that the catalytic activity of the samples grows upon an increase in the nickel content of the system. By means of scanning electron microscopy, elemental analysis, and differential thermal analysis, it was demonstrated that these catalytic systems undergo structural changes and carbonize negligibly with remaining catalytic activity in time.     

Methodology for determining hidden partitioning elements in mutual multicomponent systems and physicochemical interactions in the LiF-K2WO4-CaF2-BaF2 system

A methodology for determining hidden partitioning elements while differentiating complexing multicomponent systems was developed using exchange reactions in ternary mutual systems and tested on ten quaternary mutual systems. For the first time, using a combination of such physicochemical analysis methods as differential thermal, X-ray powder diffraction, and projection-thermographic analyses, the LiF-K₂WO₄-CaF₂-BaF₂ quaternary system was studied, which involves the hidden partitioning element K₂WO₄-LiBaF₃ and is a stable partitioning complex of the Li,K,Ca,Ba∥F,WO₄ quinary mutual system. The coordinates of nonvariant points of the quaternary system were found.     

Origin of the Rate Acceleration in the C−C Reductive Elimination from Pt(IV)-complex in a [Ga4L6]12− Supramolecular Metallocage

The reductive elimination on [(Me₃P)₂Pt(MeOH)(CH₃)₃]⁺, 2P , complex performed in MeOH solution and inside a [Ga₄L₆]¹²⁻ metallocage are computationally analysed by mean of QM and MD simulations and compared with the mechanism of gold parent systems previously reported [Et₃PAu(MeOH)(CH₃)₂]⁺, 2Au . The comparative analysis between the encapsulated Au(III) and Pt(IV)-counterparts shows that there are no additional solvent MeOH molecules inside the cavity of the metallocage for both systems. The Gibbs energy barriers for the 2P reductive elimination calculated at DFT level are in good agreement with the experimental values for both environments. The effect of microsolvation and encapsulation on the rate acceleration are evaluated and shows that the latter is far more relevant, conversely to 2Au . Energy decomposition analysis indicates that the encapsulation is the main responsible for most of the energy barrier reduction. Microsolvation and encapsulation effects are not equally contributing for both metal systems and consequently, the reasons of the rate acceleration are not the same for both metallic systems despite the similarity between them.     

Dehydrogenation activities of highly dispersed transition metal oxides on NaY zeolite

Highly dispersed α-Fe_2O_3/NaY,NiO/NaY,and CuO/NaY catalyst systems were pre-pared by impregnation method.Dispersion thresholds of the transition metal oxides on NaY" zeolitewere determined by XRD phase analysis.The dispersion capacities of the transition metal oxides on NaYzeolite are much lower than that estimated on the basis of a closed packed monolayer in the micropores.The catalytic activity and selectivity of the highly dispersed oxide catalyst systems for ethylben-zene and cyclohexane dehydrogenation reactions were reported.     

Structural studies of nanosized porous membrane catalytic systems highly active in dry reforming of biomass conversion products

The structures of porous ceramic membrane catalytic systems exhibiting high activity in dry reforming of biomass conversion products (methane, hydrocarbons C₂?CC₄, and alcohols) to a hydrogen-containing gas were studied. The membrane catalytic systems represent porous inorganic membranes (supports) prepared by self-propagating high-temperature synthesis and modified by nanosized metallocompex components, which are uniformly distributed in the internal pore volume. Structural studies were carried out using scanning electron microscopy with energy dispersive analysis, transmission electron microscopy, temperature-programmed reduction with hydrogen, and X-ray diffraction analysis.     

Separation of systems based on uranium hexafluoride and some of halogen fluorides

The purpose of this paper is to present the results of the comprehensive study of the phase equilibriums liquid-solid and liquid-vapour in binary and ternary systems, formed by uranium hexafluoride, bromine trifluoride and iodine pentafluoride.Investigation of the phase equilibriums in condensed systems is done by methods of differential thermoanalysis and visual polythermal analysis. All systems belong to simple eutectics; formation of the compounds is not detected. For all systems under investigation diagrams of the phase equilibrium liquid-solid are plotted.Phase equilibriums liquid-vapour in studied systems were studied by statistical method. All systems are non-aseotropic. The article presents diagrams of the phase equilibrium liquid-vapour in binary systems, pressure of the saturated vapour dependences on liquid composition, surface of the boiling liquid and lines of the constant content of uranium hexafluoride and iodine pentafluoride in vapour phase of the ternary system UF₆-BrF₃-IF₅.     

O<Subscript>2</Subscript>-probe EPR as a method for characterization of surface oxygen vacancies in ceria-based catalysts

Catalytic activity of ceria-based systems is essentially related to the oxygen storage/release characteristics of the surface and, therefore, to the properties of the oxygen vacancies generated upon reduction of CeO₂. EPR analysis of the superoxide species formed upon low temperature oxygen chemisorption on this type of systems is shown to be a very powerful method to characterize such defects. The present work revises results mainly obtained in the authors’ laboratory on this topic and shows the main physicochemical properties of such superoxide species. Situations of practical interest in the field of heterogeneous catalysis are analysed. These include the analysis of defects formed on pure CeO₂, as well as their chemical modification by NO chemisorption or in the presence of chlorine impurities, typically present in supported metal catalysts. Additionally, the characterization of two-dimensional ceria structures in alumina-supported ceria systems with high practical interest is shown to be uniquely provided by this EPR-based method.     

Phase equilibria in the ternary systems NaCl–NaI–Na<Subscript>2</Subscript>CrO<Subscript>4</Subscript> and KCl–KI–K<Subscript>2</Subscript>CrO<Subscript>4</Subscript>

The ternary systems NaCl–NaI–Na₂CrO₄ and KCl–KI–K₂CrO₄ were studied by differential thermal analysis. In the systems, the melting points and compositions of alloys at ternary eutectic points were determined. The compositions of crystallizing phases in the eutectics were confirmed by X-ray powder diffraction analysis.     

Analyte-receptor binding kinetics for biosensor applications

The diffusion-limited binding kinetics of antigen (analyte), in solution with antibody (receptor) immobilized on a biosensor surface, is analyzed within a fractal framework. Most of the data presented is adequately described by a single-fractal analysis. This was indicated by the regression analysis provided by Sigmaplot. A single example of a dual-fractal analysis is also presented. It is of interest to note that the binding-rate coefficient (k) and the fractal dimension (D_f) both exhibit changes in the same and in the reverse direction for the antigen-antibody systems analyzed. Binding-rate coefficient expressions, as a function of the D_f developed for the antigen-antibody binding systems, indicate the high sensitivity of thek on the D_f when both a single- and a dual-fractal analysis are used. For example, for a single-fractal analysis, and for the binding of antibody Mab 0.5β in solution to gpl20 peptide immobilized on a BIAcore biosensor, the order of dependence on the D_f was 4.0926. For a dual-fractal analysis, and for the binding of 25-100 ng/mL TRITC-LPS (lipopolysaccharide) in solution with polymyxin B immobilized on a fiberoptic biosensor, the order of dependence of the binding-rate coefficients, k₁ and k₂ on the fractal dimensions, D_f1 and D_f2, were 7.6335 and-11.55, respectively. The fractional order of dependence of thek(s) on the D_f(s) further reinforces the fractal nature of the system. Thek(s) expressions developed as a function of the D_f(s) are of particular value, since they provide a means to better control biosensor performance, by linking it to the heterogeneity on the surface, and further emphasize, in a quantitative sense, the importance of the nature of the surface in biosensor performance.     

Effect of excess electron on structure,bonding, and spectral properties of sulfur/selenium based dichalcogen systems

First principle based quantum chemical methods are employed to characterize structure, bonding, and spectral properties of sulfur and selenium based dichalcogen systems in presence of an excess electron. Inter molecular two-center three-electron (2c-3e) bonding between two chalcogen (X) atoms is described in the systems of the type (R-X)₂^•- (R = Ph, PhCH₂ X = S, Se). In addition, effect of electron withdrawing (-NO₂) and electron donating (-CH₃) groups in phenyl ring on the stability of these 2c-3e bonded systems is also studied in water medium applying a macroscopic hydration model. Molecular parameters and binding energy of the neutral, (R-X)₂ and reduced, (R-X)₂^•- dichalcogen systems are compared. Search for minimum energy structures of these open shell doublet systems are carried out applying various density functionals with dispersion corrections and MP2 method considering 6-311++G (d,p) set of basis functions for all atoms. Effect of water medium is introduced through a macroscopic solvation model based on density (SMD). Frontier molecular orbitals based analysis is carried out for showing the definite presence of 2c-3e bond between two chalcogen atoms in these radical anions of sulfur and selenium based aromatic dichalcogen systems. Excited state calculations are performed on all these systems using Time Dependent Density Functional Theory (TDDFT). UV-Vis spectra are simulated and effect of solvent water on the absorption maximum of these radical anions is discussed. This study illustrates that the combination of electronic effect and geometrical flexibility decides the strength of two-center three-electron bond in these systems.     

Thermodynamische Berechnungen zum Wolframtransport in fluorhaltigen Systemen

Thermodynamic Calculations on the Transport of Tungsten in Systems Containing Fluorine Compounds Information on the transport behaviour of tungsten in systems containing fluorine is obtained by a thermodynamic analysis of the systems W_(s)–F, W_(s)–F–O, W_(s)–F–Br, W_(s)–F–Br–O, W_(s)–Si–F, W_(s)–B–F, W_(s)–Si–F–Br, and W_(s)–B–F–Br. The results are compared with experimental findings. The influence of bromine, oxygen, silicon, and boron on the transport of tungsten is investigated. The nonblackening condition (dλ_W/dT < 0) is fulfilled in systems containing fluorine as well as bromine.     

Thermal analysis for generating phase diagrams of systems alkali metal chloride/divalent metal chloride

After a historical survey of the application of differential thermal analysis (DTA) for the generation of phase diagrams, particularly those of pseudobinary halide systems, the authors' research work on the systems ACl/MCl₂ (A = NaCs) is reported. In addition to DTA measurements the thermodynamic properties of the ternary compounds A_nMCl_n+2 are investigated by solution calorimetry and EMF measurements dependent on temperature with a newly developed galvanic cell for solid electrolytes. This method is also a useful tool for elucidating phase diagrams, especially for reactions occurring in the solid state.     

P/RS intergrowth type phases in the Ln<Subscript>2</Subscript>O<Subscript>3</Subscript>–MO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> systems

Regularities of formation of complex aluminates with structure of P/RS intergrowth type phases in the Ln₂O₃–MO–Al₂O₃ systems (Ln = rare-earth element, M = Mg, Ca, Sr, Ba) have been considered. Systematization of the data on formation of complex compounds coexisting with one-layer phases in the Ln₂O₃–MO–Al₂O₃ systems and analysis of geometry criteria of LnMAlO₄ stability is a promising approach to prediction of novel compounds with structure of Ruddlesden–Popper phase.     

Die Zustandsdiagramme von Quecksilber(II)-Jodid mit den dreiwertigen Jodiden von drei Elementen der 5. Gruppe des Periodischen Systems

The temperature/concentration diagrams of the binary systems of HgJ₂ with AsJ₃, SbJ₃, and BiJ₃ are determined by differential-thermal analysis. In addition to the temperature of the several phase transitions the peak areas of the differential curves are evaluated as a new quantity of measurement. Eutectic systems are found in each case.     

Thermal analysis of (NaF/AlF<Subscript>3</Subscript>)-FeF<Subscript>3</Subscript> and (NaF/AlF<Subscript>3</Subscript>)-FeO systems

Thermal analysis of the two systems, (NaF/AlF₃)-FeF₃ and (NaF/AlF₃)-FeO, was carried out with three different cryolite ratios. In these systems, “impurity compounds” decreased the temperature of primary crystallisation with decreasing cryolite ratios. From the slope of the dependencies, it can be assumed that the excess of AlF₃ plays a more significant role in changes in the “Fe(III)” systems than in “Fe(II)” systems.     

Structure of molten systems KF?K2TiF6 and KCL-K2TiF6

Congruently melting compounds K₃TiF₇ and K₃TiF₆Cl which are formed in the systems KF? K₂TiF₆ and KCl? K₂TiF₆, respectively, exhibit a strong influence on the structure (ionic composition) of the melts of the corresponding systems. Considering the relatively low symmetry and a high energetic state of the TiF₇^3? and TiF₆Cl^3? complex ions, a high degree of their thermal dissociation might be expected. This assumption was confirmed by two different methods based on a thermodynamic analysis of the phase equilibria and of the volume properties of the investigated systems, respectively. In connection with the former method, the values of the enthalpy of fusion of K₂TiF₆, K₃TiF₇, and K₃TiF₆Cl which were used in the calculations have also been estimated.     

Prediction of new compounds in systems of monovalent and divalent metal halides

Yet-nonsynthesized compounds of the compositions ABHal₃ and A₂BHal₄ in halide systems AHal-BHal₂ were predicted, and so was the type of their crystal structure under normal conditions. The new compounds were predicted using only data on the properties of elements and simple halides. The calculations were performed using a special program system for computer analysis of information, which is based on precedent-based pattern recognition methods.