Phase relations in the CaO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system in the subsolidus region

Phase relations in the CaO-Bi₂O₃-B₂O₃ system have been investigated by X-ray powder diffraction and differential thermal analyses, and the isothermal section at 600°C has been constructed. The formation of ternary compounds at the component ratios 1CaO: 1Bi₂O₃: 1B₂O₃ (CaBi₂B₂O₇) and 1CaO: 1Bi₂O₃: 2B₂O₃ (CaBi₂B₄O₁₀) has been established X-ray diffraction characteristics of these phases are presented.     

Phase relations in the MgO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Phase relations in the MgO-Bi₂O₃-B₂O₃ system have been investigated by X-ray powder diffraction analysis and DTA. No ternary compounds have been found in the system. Quasi-binary sections have been the 600°C determined and isothermal section of the system has been constructed.     

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.     

Chemical durability of MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> and K<Subscript>2</Subscript>O-MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Thermal and chemical durability studies of the phosphate glasses belonging to the binary MoO₃-P₂O₅ and the ternary K₂O-MoO₃-P₂O₅ systems are reported. The chemical resistant attack tests carried out on the free alkaline MoO₃-P₂O₅ glasses show that the glass associated with the P/Mo ratio 2 has the high chemical durability. It shows also a high glass transition temperature value. The above findings are interpreted in terms of the cross-link density of the glasses and the strength of the M-O bonds (M=P, Mo). The influence of K₂O addition on the properties (density, T _g, durability) of this binary high water resistant glass is studied. It is found that the chemical durability along with the other physical properties are reduced by the incroporation of K₂O in the glass matrix. The results were explained by assuming the formation of non-bridging oxygens and weak bonds. The mechanism of the dissolution of these glasses is proposed.     

Preparation and radioluminescent characteristics of Li<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript>-CaF<Subscript>2</Subscript> glasses doped with Ce(III) and Gd(III)

A method has been developed for the preparation of homogeneous moisture-resistant glasses with the composition Li₂O-B₂O₃-P₂O₅-CaF₂ : Ce³⁺-Gd³⁺. Energy transfer from Gd³⁺ to Ce³⁺ was noted in a study of the radioluminescence spectra of these samples using ²⁴¹Am as the excitation source (60 keV). The decay time of the Ce³⁺ radioluminescence in the glasses obtained was 20-25 ns.     

Viscosity and shrinkage of porous and quartzoid glasses of the Na<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

Shrinkage of porous glasses on heating from 20 to 800°C was studied and temperature dependences of the viscosity in the range of 10¹¹–10¹³ P were determined for quartzoid (sintered) glasses based on five glasses with different compositions in the Na₂O-B₂O₃-SiO₂ system. The shrinkage of porous glasses and the viscosity of quartzoid glasses were analyzed in relation to their composition and temperature of preliminary thermal treatment.     

Thermal behaviour and fragility of Sb<Subscript>2</Subscript>O<Subscript>3</Subscript>-containing zinc borophosphate glasses

Thermal behaviour of the glass series (100-x)[50ZnO-10B₂O₃-40P₂O₅]·xSb₂O₃ (x=0-42 mol%) and (100-y)[60ZnO-10B₂O₃-30P₂O₅]·ySb₂O₃ (y=0-28 mol%) was investigated by DSC and TMA. The addition of Sb₂O₃ results in a decrease of the glass transition temperature and crystallization temperature in both compositional series. All glasses crystallize on heating in the temperature range of 522–632°C. Thermal expansion coefficient of the glasses monotonously increases with increasing Sb₂O₃ content in both series and varies within the range of 6.6–11.7 ppm °C⁻¹. From changes of thermal capacity within the glass transition region it was concluded that with increasing Sb₂O₃ content the ‘fragility’ of the studied glasses increases.     

Thermal behaviour and properties of Na<Subscript>2</Subscript>O-TiO<Subscript>2</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to study the thermal behaviour of (50-x)Na₂O-xTiO₂-50P₂O₅ and 45Na₂O-yTiO₂-(55-y)P₂O₅ glasses. The addition of TiO₂ to the starting glasses (x=0 and y=5 mol% TiO₂) resulted in a nonlinear increase of glass transition temperature and dilatation softening temperature, whereas the thermal expansion coefficient decreased. All prepared glasses crystallize under heating within the temperature range of 300–610°C. The contribution of the surface crystallization mechanism over the internal one increases with increasing TiO₂ content. With increasing TiO₂ content the temperature of maximum nucleation rate is also gradually shifted from a value close to the glass transition temperature towards the crystallization temperature. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were NaPO₃, TiP₂O₇ and NaTi₂(PO₄)₃. The chemical durability of the glasses without titanium oxide is very poor, but with the replacement of Na₂O or P₂O₅ by TiO₂, it increases sharply.     

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.     

Effect of nucleating agents on the crystallization of Li<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system glass

The processes of nucleation of Li₂O-Al₂O₃-SiO₂ glasses with TiO₂ and TiO₂+ZrO₂ as nucleating agents were discussed. The DTA peak temperature and DTA peak height shown a strong dependence on the nucleation temperature in the glass with TiO₂, while in the glass with TiO₂+ZrO₂ this tendency was small. The optimum nucleation temperatures were 745 and 760°C for two glasses. It suggested that with TiO₂+ZrO₂ as nucleating agents, the crystallization had lower sensitivity for nucleation temperature, and the glass had higher nucleation efficiency than with TiO₂.     

Influence of B<Subscript>2</Subscript>O<Subscript>3</Subscript> on the structure and crystallization of soil active glasses

Glasses of the SiO₂–P₂O₅–K₂O–MgO–CaO–B₂O₃ system acting as nutrients carriers in the soil environment were synthesised by the melt-quenching technique. Thermal properties were studied using DTA/DSC methods and the influence of B₂O₃ and P₂O₅ content on thermal stability and crystallization process of these glasses was examined. The structure of the glass network was characterized by FTIR, ³¹P, and ¹¹B MAS NMR. The chemical activity of the glasses in the 2 mass% citric acid solution was measured by the ICP-AES method. The analysis indicated that the formation of P–O–B units with chemically stable tetrahedral borate groups decreases the glass solubility in conditions simulating the soil environment.     

Thermodynamic properties of silicate glasses and melts: VII. System MgO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

Processes of evaporation and thermodynamic properties of glasses and melts of the system MgO-B₂O₃-SiO₂ in the range of 1550–1800 K were studied for the first time by high-temperature mass-spectrometry. The resulting activities and Gibbs energies of components and also corresponding excess values point to negative deviations from ideal behavior and to the absence of immiscibility fields in glasses and melts of the system under study in the studied temperatures and concentration intervals.     

Eu<Superscript>3+</Superscript>-fluorescence properties in nano-crystallized SnO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> glass-ceramics

Fluorescence and spectral hole burning properties of Eu³⁺ ions were studied in nanocrystals-precipitated SnO₂-SiO₂ glasses. The glasses were prepared to contain various amount of Eu₂O₃ using the sol-gel method, in which SnO₂ nanocrystals were precipitated by heating in air. In the glasses containing Eu₂O₃ less than 1%, the Eu³⁺ ions were preferentially doped in the SnO₂ nanocrystals and their fluorescence intensities were enhanced by the energy transfer due to the recombination of electrons and holes excited in SnO₂ crystals. The SnO₂ nanocrystals-precipitated glasses exhibited the persistent spectral holes with the depth of ∼25% of the total fluorescence intensities of the Eu³⁺ ions. With the increasing Eu₂O₃ concentration, the amount of SnO₂ nanocrystals decreased and the Sn⁴⁺ ions formed the random glass structure together with the silica network. This structure change induced the fluorescence intensities and the hole depth to decrease.     

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.     

Comparison of the Solubility of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>, Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> in High Temperature Water

As the solubility is a direct measure of stability, this study compares the solubilities of ZnFe₂O₄, Fe₃O₄ and Fe₂O₃ in high temperature water. Through literature analysis and formula derivation, it is shown that it is reasonable to assume ZnFe₂O₄ and Fe(OH)₃ coexist when ZnFe₂O₄ is dissolved in water. Results indicated that the solubility of ZnFe₂O₄ is much lower than that of Fe₂O₃ or Fe₃O₄. The low solubility of ZnFe₂O₄ indicates that it is more protectively stable as an anticorrosion phase. Moreover, the gap between the solubility of ZnFe₂O₄ and that of Fe₃O₄ or Fe₂O₃ was enlarged with an increase of temperature. This means that ZnFe₂O₄ is more protective at higher temperatures. Further analysis indicated that with the increase of temperature, the solubility of ZnFe₂O₄ changed little while those of Fe₂O₃ or Fe₃O₄ changed a lot. Little change of the solubility of ZnFe₂O₄ with increase of temperature showed that ZnFe₂O₄ is stable. The very low and constant solubility of ZnFe₂O₄ suggests that it is more protective than Fe₂O₃ and Fe₃O₄, especially in water at higher temperature.     

Mass spectrometric investigation of vaporization in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The thermodynamics of vaporization in the Bi₂O₃-Fe₂O₃ quasibinary system was studied by high-temperature mass-spectrometry. The partial pressures of the constituents of a saturated vapor over the system at 1100 K were determined. Based on the experimental data, the following parameters were calculated: the activities of the components of the Bi₂O₃-Fe₂O₃ system condensed phase, the standard enthalpies of some heterogeneous reactions, and standard enthalpies of formation and enthalpies of formation for crystalline BiFeO₃ and Bi₂Fe₄O₉ from individual oxides. An optimal temperature for the solid-phase synthesis of bismuth ferrites from simple oxides is recommended.     

Glass formation in the Li<Subscript>2</Subscript>O-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript>-TeO<Subscript>2</Subscript> system

In the Li₂O-Ta₂O₅-TeO₂ system, the boundaries of the glass region have been determined. The electrical and spectral properties of glasses and crystalline materials have been investigated.     

Synthesis of Schiff bases and benzylamino derivatives containing [1-B<Subscript>10</Subscript>H<Subscript>9</Subscript>NH<Subscript>3</Subscript>]<Superscript>−</Superscript> anion

Reactions of an amino derivative of the closo-decaborate anion [1-B₁₀H₉NH₃]^– with aromatic aldehydes afforded Schiff bases [1-B₁₀H₉NH=CHAr]^– (Ar=Ph, C₆H₄-2-OMe, or C₆H₄-4-NHCOMe). The reduction of the latter with sodium borohydride gave the corresponding benzylamino derivatives [1-B₁₀H₉NH₂CH₂Ar]^–.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2004–2007, September, 2004.     

Changes in the heat capacity of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions near the point of antiferromagnetic phase transition in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>

Al₂O₃-Cr₂O₃ solid solutions with 0, 4, 7, 10 and 20 mol% of corundum were synthesized using a high-pressure/high-temperature apparatus and characterized by X-ray powder diffraction. Calorimetric measurements were carried out using DSC-111 (Setaram). Heat capacity was measured by the enthalpy method in a temperature range of 260–340 K, near magnetic phase transition in pure Cr₂O₃ (305 K). Magnetic contribution into the heat capacity was derived and found to change irregularly with the composition.     

Investigation of macro-/mesoporous Re<Subscript>2</Subscript>O<Subscript>7</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts prepared by a particle-template method for butylene metathesis

Macro-/mesoporous Al₂O₃ supports were prepared by using monodisperse polystyrene (PS) microspheres as a template. The pore volume and BET surface area of the Al₂O₃ supports increased considerably with increasing amounts of the PS microspheres; further investigation showed that PS template only increased the volume of macro-pores but did not change the volume of meso-pores or micro-pores. Macro-/mesoporous Re₂O₇/Al₂O₃ metathesis catalysts were prepared through loading Re₂O₇ onto the as-prepared macro-/mesoporous Al₂O₃ supports, and their catalytic performance was tested in a fixed-bed tubular reactor using the metathesis of normal butylenes as a probe reaction. The results showed that the prepared macro-/mesoporous Re₂O₇/Al₂O₃ catalyst had high activity with consistent selectivity; propylene and pentene accounted for more than 90 wt% of the metathesis products, while the amount of ethylene plus hexane was less than 10 wt%, the majority of which was hexane. These Re₂O₇/Al₂O₃ catalysts had not only higher activity, but also longer working life span and higher tolerance to carbon residues than conventional Re₂O₇/Al₂O₃ catalysts.