Thermal synthesis of the CeO<Subscript>2</Subscript>-PrO<Subscript>2</Subscript>-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>pigments

Summary The synthesis of new compounds based on the CeO₂-PrO₂-Nd₂O₃system, which can be used as pigments for colouring of ceramic glazes, is investigated in our laboratory. The optimum conditions for the syntheses of these compounds have been estimated. The methods of thermal analysis provided first information about the temperature region of the formation of the pigments investigated. The synthesis of these compounds was followed by thermal analysis using STA 449/C Jupiter (Netzsch, Germany).     

The influence of structural factors on the gas-sensitive properties of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-SnO<Subscript>2</Subscript>

The influence of the dispersity and structural and phase state of oxide materials based on Fe₂O₃ and SnO₂ on the gas-sensitive properties of these materials used as sensitive layers in chemical sensors was considered. It was found that high-dispersity Fe₂O₃-SnO₂ (Fe: Sn = 9: 1) ceramic layers possessed high sensitivity to ethanol vapor in both dry and humid atmosphere and low sensitivity to CO and CH₄. The maximum response to ethanol vapor in humid atmosphere was characteristic of layers with structures of substitution-interstitial solid solutions of Sn⁴⁺ in α-Fe₂O₃.     

Permeation studies on transparent multiple hybrid SiO<Subscript>2</Subscript>-PMMA coatings-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> barriers on PEN substrates

In this work we report the performance of permeation barriers based on organic/inorganic multilayer stacks. We have used PMMA-SiO₂ (poly methyl methacrylate-silica) hybrid films synthesized through a sol–gel route as organic–inorganic components, whereas Al₂O₃ thin films were used as the inorganic component. The hybrid layers were deposited by dip coating and the Al₂O₃ by atomic layer deposition (ALD), films were prepared on polyethylene naphthalene (PEN) substrates. The permeability of the films and stacks is evaluated using helium as the diffusion gas in a custom made ultra-high vacuum system. The results show that permeability for PEN is reduced from 5 × 10⁻³ g/m²-day to about 9 × 10⁻⁵ g/m²-day for the best multiple barrier evaluated. Increased barrier properties are due to the increasing in the path and hence the lag-time of the permeating gas. In particular, we report the surface roughness of the different layers and its impact on the barrier performance. The hybrid layers reduced notably the roughness of the bare PEN substrate improving the quality of the Al₂O₃ layer in the barrier. The optical transmittance of the barriers in the visible region is higher than 80% in all the studied cases.     

Preparation and Characterisation of Nano-Structured WO<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> Layers for Photoelectrochromic Devices

Nano-structured WO₃-TiO₂ layers were prepared by the sol-gel route. To obtain transparent, porous and crack free layers up to 0.8 μ m with a single dipping cycle a templating strategy was used. As a template three-dimensionally network based on organically modified silane was introduced to the WO₃ and TiO₂ sols. The WO₃ layers were dip-coated onto the conductive glass substrate (TCO) and the TiO₂ layers on the top of the WO₃ layer. The morphology and the structure of the layers were determined by Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Energy Dispersive X-Ray Spectroscopy (EDXS), Auger and Infrared spectroscopy. SEM image of the WO₃-TiO₂ layer confirmed the nano-porosity of the layers and give the size of the particles of about 10 nm for TiO₂ and 30 nm for WO₃ layer. Further analysis indicated that the titanium sol penetrates the WO₃ layer. Particles in the WO₃ layer consist of a crystalline monoclinic WO₃ core surrounded by a 5–10 nm amorphous phase consisting of WO₃, TiO₂ and SiO₂. The WO₃-TiO₂ layers were used to assemble all solid state photoelectrochromic (PE) devices. Under 1 sun irradiation (1000 W/m²) the visible transmittance of the PE device changes from 62% to 1.6%. The colouring and bleaching processes last about 10 minutes.     

Study of cationic substitution in Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> and derived structures in the framework of the modular approach

The possibilities of substitution of lead, alkaline and rare earth, antimony, and tellurium cations for bismuth ions in the structure of the Bi₂WO₆ ferroelectric and compounds with more complicated derived structures have been studied. The trends in the formation of solid solutions are well described in the framework of the modular approach in which layers are treated as building units of crystal structures. The underlying existence criteria (electroneutrality, geometric and chemical compatibility of layers) formulated for simple (two-layer) structures can be easily extended to more complicated (multilayer) structures. On the basis of the results obtained, the existence of new series of layered bismuth oxohalides was predicted.     

Mechanism and kinetics of formation of La<Subscript>2</Subscript>SrFe<Subscript>2</Subscript>O<Subscript>7</Subscript> and Nb<Subscript>2</Subscript>SrFe<Subscript>2</Subscript>O<Subscript>7</Subscript>

Phase formation processes in the systems Ln₂O₃-SrO-Fe₂O₃ (Ln = La, Nd) in air in the temperature range 1200–1500°C were studied. The synthesis of the complex ferrites La₂SrFe₂O₇ and Nb₂SrFe₂O₇ involves the formation of the intermediate compounds LnFeO₃ and LnSrFeO₄ and occurs by the same mechanism as the synthesis of the corresponding aluminates, but much faster.     

Thermal synthesis of the (Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1–x</Subscript>(Er<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>x</Subscript> pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new environmentally friendly inorganic pigments. Chemical compounds of the (Bi₂O₃)_1–x(Er₂O₃)_x type were synthetized. The host lattice of these pigments is Bi2O3 that is doped by Er³⁺ ions. The incorporation of doped ions provides interesting colours and contributes to an increase in the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments.     

Phase ratios in the M<Subscript>2</Subscript>O-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-SO<Subscript>3</Subscript> (M = Rb,Cs) systems and the properties of the compounds formed in these systems

Powder X-ray diffraction and microscopy have been used to study phase ratios of the M₂O-V₂O₅-SO₃ (M = Rb, Cs) systems, which model the active component of rubidium-vanadium and cesium-vanadium catalysts for sulfuric acid production at high sulfur dioxide conversions. We have stated that each system forms four compounds: M₃VO₂(SO₄)₂, MVO₂SO₄, M₄V₂O₃(SO₄)₄, and MVO(SO₄)₂. The thermal properties of these compounds and their interaction with water vapor saturated at room temperature have been studied. The unit cell parameters have been determined for the compounds MVO₂SO₄ (M = K, Rb), MVO(SO₄)₂, and M[VO₂(SO₄)(H₂O)₂] · H₂O (M = Rb, Tl). The reciprocal transformations of the components and phases of the M₂O-V₂O₅-SO₃ systems match the Lux-Flood ideas of the acid-base properties of oxide compounds.     

Cationic networks in the structures of borates,tungstates, and borotungstates forming in the Ln<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-WO<Subscript>3</Subscript> systems

The influence of the structures of binary compounds on the formation of ternary mixed-anion compounds—borotungstates—in ternary Ln₂O₃-B₂O₃-WO₃ systems was studied. The structures of borotungstates either inherit the predominant type of cationic network from the structures of the binary compounds (anisotropic cationic networks in Ln (BO₂)(WO₄)) or represent a sum of equivalent anisotropic and isotropic cationic networks, forming combined cationic networks (in Ln₃BWO₉). In the lanthanide series, the ranges of existence of borotungstates coincide with the ranges of existence of the structure types most abundant in the binary compounds.     

Phases in the system Tb<Subscript>2</Subscript>O<Subscript>3</Subscript>-SeO<Subscript>2</Subscript>-H<Subscript>2</Subscript>O at 100°C and their physicochemical study

Summary The solubility isotherm of the system Tb₂O₃-SeO₂-H₂O at 100° was studied. The compounds of the three-component system were identified by the Schreinemakers’ method as well as by chemical and X-ray phase analyses. Simultaneous TG and DTA analyses of all compounds of the system were made. The mechanism of thermal decomposition was described.     

Sb<Subscript>2</Subscript>S<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> nanocomposite layers synthesized using the layer-by-layer technique

Possibility of layer-by-layer synthesis by colloidal layering of Sb₂S₃-SiO₂ nanocomposite layers from colloid solutions of {[H _x Sb₂S₅] ^m ?}mNa⁺ and SiO₂ was studied. The composition of the layers synthesized was examined by Raman spectroscopy, transmission spectroscopy in the UV and visible spectral ranges, energy-dispersion micro analysis, and scanning electron microscopy.     

Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> phase diagram

Phase relations in the Y₂O₃-Ga₂O₃ system were studied by the anneal-and-quench technique in air within 1000–2300°C, and a phase diagram was plotted. Three compounds were found to form: Y₃GaO₆, Y₄Ga₂O₉, and Y₃Ga₅O₁₂; the temperature and concentration bounds of stability were determined for these compounds. Indexing results for Y₃GaO₆ are given.     

Trends in the cation distribution in the structures of the compounds forming in the Ln<Subscript>2</Subscript>O<Subscript>3</Subscript>-GeO<Subscript>2</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> systems

The cationic networks in the structures of the initial oxides and all binary and ternary compounds forming in the Ln₂O₃-GeO₂-P₂O₅ systems have been studied. In the phase diagrams of the Nd₂O₃-GeO₂-P₂O₅ and Er2O₃-GeO₂-P₂O₅ systems, the regions of the structural influence of individual compounds with topologically identical cationic networks—anisotropic (A), combined (C), and isotropic (I)—are united into common areas. The A: C: I area ratio is 1: 1: 1 in the neodymium system and 1.7: 1: 3.4 in the erbium system.     

Synthesis,structural, spectral,thermal and comparative biological activity studies of [V<Subscript>2</Subscript>O<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The hydrothermal reaction of a mixture of V₂O₅, VCl₃, 2,5-pyridinedicarboxylic acid and diluted H₂SO₄ for 68 h at 180°C gives a blue colored solution which yields prismatic blue crystals of IV ₂ ^IV O₂(SO₄)₂(H₂O)₆] (1) in 32% yield (based on V). Complex 1 was investigated by means of elemental analysis (C, H and S), TGA, FT-IR, manganometric titration, Single Crystal X-ray Diffraction Methods and also comparative antimicrobial activities. Crystal data for the compound: monoclinic space group P2₁/c and unit cell parameters are a = 7.3850(12) Å, b = 7.3990(7) Å, c = 12.229(2) Å, β = 108.976(12)° and Z = 2. Although structure of 1 as a natural mineral has been previously determined, this work covers new preparation method and full characterization of 1 along with comparison of antibacterial activity between 1 and the commercial vanadium(IV) oxide sulfate hydrate compounds, VOSO₄ · xH₂O (Riedel-de Haën and Alfa Aesar brand names). 1 was evaluated for the antimicrobial activity against gram-positive, gram-negative bacteria, yeasts and mould compared with the commercial VOSO₄ · xH₂O compounds. 1 showed weak activity against bacteria Bacillus cereus, Nocardia asteroides and yeast Candida albicans. A good antimicrobial activity was recorded against Cirtobacter freundii (15 mm). There are only a few reproducible well-defined vanadium(IV) starting materials to use for exploring the synthesis of new materials. VCl₄, VO(acac)₂, VOSO₄ · xH₂O and [V(IV)OSO₄(H₂O)₄] · SO₄ · [H₂N(C₂H₄)₂NH₂] are common starting materials for such applications. In addition to these compounds, 1 can be used as an oxovanadium precursor.     

High-temperature heat capacity of stannates Er<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript> and Tm<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript>

Erbium stannate Er₂Sn₂O₇ and thulium stannate Tm₂Sn₂O₇ with a pyrochlore-type structure were produced by solid-phase synthesis by calcining stoichiometric mixtures of the respective oxides in air at 1473 K for 240 and 200 h. The high-temperature heat capacity of Er2Sn2O7 and Tm₂Sn₂O₇ was studied by differential thermal calorimetry at 353–1000 K. From the experimental dependences C _P = f(T), the thermodynamic functions (enthalpy change, entropy change, and reduced Gibbs free energy) of oxide compounds were calculated.     

Cyclomagnesiation of nitrogen-containing 1,2-dienes with grignard compounds catalyzed by Cp<Subscript>2</Subscript>TiCl<Subscript>2</Subscript>

Cyclomagnesiation of nitrogen-containing 1,2-dienes with Grignard compounds in the presence of activated magnesium and Cp₂TiCl₂ as catalyst afforded 2,5-bis(aminoalkylidene)magnesacyclopentanes in high yield.     

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.     

Rational design of double-confined Mn<Subscript>2</Subscript>O<Subscript>3</Subscript>/S@Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocube cathodes for lithium-sulfur batteries

Due to the high specific capacities and environmental benignity, lithium-sulfur (Li-S) batteries have shown fascinating potential to replace the currently dominant Li-ion batteries to power portable electronics and electric vehicles. However, the shuttling effect caused by the dissolution of polysulfides seriously degrades their electrochemical performance. In this paper, Mn₂O₃ microcubes are fabricated to serve as the sulfur host, on top of which Al₂O₃ layers of 2 nm in thickness are deposited via atomic layer deposition (ALD) to form Mn₂O₃/S (MOS) @Al₂O₃ composite electrodes. The MOS@Al₂O₃ electrode delivers an excellent initial capacity of 1012.1 mAh g^?1 and a capacity retention of 78.6% after 200 cycles at 0.5 C, and its coulombic efficiency reaches nearly 99%, giving rise to much better performance than the neat MOS electrode. These findings demonstrate the double confinement effect of the composite electrode in that both the porous Mn₂O₃ structure and the atomic Al₂O₃ layer serve as the spacious host and the protection layer of sulfur active materials, respectively, for significantly improved electrochemical performance of the Li-S battery.     

Thermal analysis of doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>

New environmentally inorganic pigments based on Bi₂O₃ doped by metal ions, such as Zr⁴⁺ and Dy³⁺ have been developed and characterized using the methods thermal analysis, X-ray powder diffraction, and spectral reflectance data. The compounds having formula Bi_2−x Dy _x/2Zr_3x/8O₃ (x = 0.2, 0.6, 1.0, and 1.2) were prepared by the solid state reaction. Methods of thermal analysis were used for determination of the temperature region of the pigment formation and thermal stability of compounds. The incorporation of doped ions in Bi₂O₃ changes the color from yellow to orange and also contributes to a growth of their thermal stability. This property gives a direction for coloring ceramic glazes.     

Joint cycloalumination of ethylene and other unsaturated compounds with EtAlCl<Subscript>2</Subscript> in the presence of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>. Synthesis of aluminacarbocycles

A procedure has been developed for the selective synthesis of five-membered aluminum-containing heterocycles, 2,3-dialkyl-1-ethylaluminacyclopent-2-enes, 3-alkyl-1-ethylaluminacyclopentanes, 2-alkylidene-1-ethylaluminacyclopentanes, and 3-alkyl-1-ethyl-2-methylidenealuminacyclopentanes, via joint cycloalumination of ethylene and other unsaturated compounds (acetylenes, olefins, and allenes) with EtAlCl₂ in the presence of Cp₂ZrCl₂ as catalyst.