Change of the thermal behavior of 55Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> ⋅ 45B<Subscript>2</Subscript>O<Subscript>3</Subscript> glass at annealing close to the vitrification temperature

The characteristic properties of relaxation processes for 55Bi₂O₃ ? 45B₂O₃ glass were described. The pattern of changes of the vitrification temperature (T _g ) is found to be quasi-periodic; the value of the endothermic effect near T _g (ΔC’ _p ) and the difference between the softening point and the vitrification temperature (T _m –T _g ) were determined. The temperature-time parameters of the transition from quasi-periodic to the continuous change of the properties were determined and an explanation of such behavior of the system was offered.     

Preparation and Photocatalytic Activity of an Inorganic–Organic Hybrid Photocatalyst Ag<Subscript>2</Subscript>WO<Subscript>4</Subscript>/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>

Ag₂WO₄/g-C₃N₄ composites with different Ag₂WO₄ concentration and calcination temperature were synthesized via a mixing and heating approach. Various techniques were used to investigate the characters of the as-prepared samples, such as thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. The degradation of rhodamine B (20 ppm) under visible light was performed to investigate the photocatalytic activity of Ag₂WO₄/g-C₃N₄ composites. Results indicate that the Ag₂WO₄/g-C₃N₄ is actually Ag/Ag₂WO₄/g-C₃N₄ ternary system. 7.5 wt% Ag₂WO₄/g-C₃N₄ prepared at 300 °C presented the best photocatalytic performance in rhodamine B degradation. The degradation rate reaches 0.0679 min^?1, which is 3.25 times higher than the value of pure g-C₃N₄. The enhanced activity is attributed to the synergetic effect of Ag₂WO₄, g-C₃N₄ and metal Ag. Additionally, cycling experiments also proved that the Ag₂WO₄/g-C₃N₄ photocatalyst has good stability.     

Mechanical,Structural and Thermal Properties of Transparent Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO–TeO<Subscript>2</Subscript> Glass System

Oxide based optical glass materials has important potential material in many applications from fiber optic to sensor due to the high transparency and amourphous structures. The objective of this study is to synthesize the novel optical glass materials based on the bismuth and aluminum contents to be able to determine the physical, chemical and mechanical properties by considering the systematic experimental steps. In this study, Bi₂O₃–Al₂O₃ based tellurite optical glasses have been prepared by using conventional melt quenching method as a function of the both Bi₂O₃ and Al₂O₃ compositions. There is a strong interactions between the glass former and modifier ions that might effect on the structure and mechanical properties. During the experimental steps, thermal, structural and mechanical properties of the prepared glass materials have been determined considering the DTA/DSC, FT-IR spectroscopy, SEM and Vicker’s hardness techniques, respectively. Thermal parameters, like glass transition, T_g, onset, T_x, crystallization, T_p, and melting, T_m, temperatures were obtained by using DTA scan.     

Spectral Properties of Doped Glasses of the 35Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> · 40PbO · 25Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> Composition Synthesized in a Quartz Crucible

A glasslike material of the 35Bi₂O₃ · 40PbO · 25Ga₂O₃ composition is investigated. Quartz glass is used in the synthesis as the crucible material. It is shown that, compared to the platinum crucible, the high-energy transmission cutoff shifts from 650 to 500 nm, which has enabled us to study the upconversion luminescence spectra of the glass of the 35Bi₂O₃ · 40PbO · 25Ga₂O₃ composition doped by Er³⁺ ions in the range 500–700 nm. The upconversion luminescence spectra for the glass doped by Er³⁺ and codoped by Nd³⁺ and Yb³⁺ ions are obtained.     

Monte Carlo Design and Experiments on the Neutron Shielding Performances of B<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> Glass System

Neutron shielding properties of (90 – x)B₂O₃–10ZnO–xBi₂O₃ glass systems (where x = 15, 20, 25 and 30 mol %) were investigated by Monte Carlo simulations (FLUKA and GEANT4) and experiments. Neutron mass removal cross sections, number of inelastic scattering, elastic scattering, and capture interactions were estimated by simulations. ²⁴¹Am/Be neutron source was used for the neutron equivalent dose rate measurements. As a result, produced glass samples have fine neutron shielding capacity.     

Conversion of 4-Methylanisole Catalyzed by Pt/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and by Pt/SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: Reaction Networks and Evidence of Oxygen Removal

Abstract  

The conversion of 4-methylanisole, a prototypical bio-oil compound, was catalyzed by Pt/Al₂O₃, Pt/SiO₂-Al₂O₃, or HY zeolite at 573 K and atmospheric pressure. More than a dozen products were formed with each catalyst, the most abundant being 4-methylphenol, 2,4-dimethylphenol, and 2,4,6-trimethylphenol; toluene was also a major product when the catalyst was supported platinum with H₂ as a co-reactant. 4-Methylphenol was the only methylphenol isomer formed in significant yields, which indicates that migration of the methyl group on the aromatic ring is not significant under the selected reaction conditions. The data determine approximate reaction networks including reactions forming 4-methylphenol, 2,4-dimethylphenol, and toluene as primary products. The kinetically significant reaction classes were transalkylation, observed with all three catalysts, and hydrogenolysis (including hydrodeoxygenation) and hydrogenation, observed only with the platinum-containing catalysts operating in the presence of H₂. Data such as those reported here provide a starting point for predicting the conversion of whole bio-oils for removal of oxygen and upgrading of fuel properties.     

Enhancement of the Activities of γ-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for Methane-SCR of NO by Treatment with NH<Subscript>3</Subscript>

Abstract  

The precursor particles for γ-Ga₂O₃–Al₂O₃ solid solutions were prepared by the coprecipitation method from aqueous solutions of Ga(NO₃)₃ and Al(NO₃)₃ with (NH₄)₂CO₃ as a precipitant. The γ-Ga₂O₃–Al₂O₃ solid solutions were obtained by calcination of the precursor at 700 °C. In this paper, the performance of the catalysts treated with NH₃ was investigated for the selective catalytic reduction (SCR) of NO with methane as a reducing agent, and it was found that γ-Ga₂O₃–Al₂O₃ catalysts treated with NH₃ and subsequently annealed in air showed higher activities than the γ-Ga₂O₃–Al₂O₃ catalysts without NH₃ treatment. NH₃ treatment of the catalyst caused partial rearrangement of Ga³⁺ and Al³⁺ ions and increased the population of tetrahedral Ga³⁺ ions in the defective spinel structure.     

Hydroisomerization of Benzene-Containing Gasoline Fraction on Pt/B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pt/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

The effect of the hydroisomerization conditions of the benzene-containing fraction of catalytic reforming gasoline on the yield and composition of products is studied on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts. These catalysts allow benzene to be completely removed from the raw material. At the same time, the greatest yields of liquid products are obtained with minimal losses of the octane number at 2 MPa, a mass feedstock hourly space velocity (MFHSV) of 2 h^?1, and 325°C: 96.3 and 95.4 wt % on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts, respectively. The activity of the catalysts is maintained for 100 h during their operation.     

Role of CeO<Subscript>2</Subscript> in Rh/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for CO<Subscript>2</Subscript> Reforming of Methane

Abstract  

The Rh/α-Al₂O₃ catalyst was modified by CeO₂ in order to improve the thermal stability and the carbon deposition resistance during the CO₂ reforming of methane The carbon formation was determined by TPO, TEM and Raman spectroscopy. Characterization results showed that the incorporation of Ce in the support inhibits the carbon deposition, increasing the useful life and the stability of the Rh base catalysts.     

Porous ceramics based on the ZrO<Subscript>2</Subscript>(Y<Subscript>2</Subscript>O<Subscript>3</Subscript>)–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system for filtration membranes

The results of the studies of the process of fabricating ceramic filtration membranes in the system ZrO₂(Y₂O₃)–Al₂O₃ are presented. The phase compositions of the precursor powders and sintered ceramics have been investigated and their porous structures have been determined. Two stages of the implementation of the technology were demonstrated: fabrication of substrates with an open porosity ranging from 20 to 47% and pore sizes in the 100–300 nm range, as well as the deposition of nanocrystalline aluminum oxide layers on them. It has been established that the pore size distribution in the membrane layer of α-Al₂O₃ is unimodal (from 30 to 100 nm).     

Synthesis of the study of solid solutions based on the ZrO<Subscript>2</Subscript>–HfO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>(CeO<Subscript>2</Subscript>) system

The results of the studies of the conditions of the liquid-phase synthesis of highly dispersed xerogels with a low degree of agglomeration and precursor nanopowders (~10–12 nm) based on zirconium dioxide in the ZrO₂–HfO₂–Y₂O₃(CeO₂) system are presented. The thermal decomposition of xerogels and formation of crystalline solid solutions with the structure of fluorite are investigated. The optimal conditions for the solidification of nanodispersed powders for fabricating compact ceramics based on solid solutions of ZrO₂ and the physical–chemical properties of these ceramics are studied.     

Formation and stability of glasses with ultra-optical properties in TiO<Subscript>2</Subscript>–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–PbO system

To obtain ultra-optical property in glasses, as the basis for photonic applications, the glass forming region of TiO₂–Bi₂O₃–PbO system was investigated and determined by melting series of compositions in the system. The glass-forming boundary region was defined. The best compositions for glass formation were found to be around the eutectic and peritectic regions in the corresponding phase diagram. Generally, stability increased with the addition of TiO₂, acting as a conditional glass former, to a maximum of 15TiO₂ mol %. Replacing PbO with Bi₂O₃ in the glass worsened the stability, due to the increase of heavy cation Bi^3– in the glass structure. Finally, the refractive index and dispersion of some stable glasses were measured, which were as high as 2.435 and 10.2, respectively.     

Effects of the geometry and operating temperature on the stability of Ti/IrO<Subscript>2</Subscript>–SnO<Subscript>2</Subscript>–Sb<Subscript>2</Subscript>O<Subscript>5</Subscript> electrodes for O<Subscript>2</Subscript> evolution

Ternary IrO₂–Sb₂O₅–SnO₂ anode has shown its superiorities over IrO₂ and many other electrocatalysts for O₂ evolution, in terms of electrochemical stability, activity and cost. The performance of IrO₂–Sb₂O₅–SnO₂ anodes is affected by its electrochemical properties and operating conditions. In this paper, the electrochemical stability and activity of the Ti/IrO₂–Sb₂O₅–SnO₂ anodes prepared with three different geometries were investigated under different operating conditions. It was found that anodes with large mean curvature have high electrochemical stability. Although increasing temperature results in a decrease in the stability of Ti/IrO₂–Sb₂O₅–SnO₂, the anode with a mean curvature of 200 m⁻¹ still shows acceptable service life even at 70 °C. This tolerance of high temperature was attributed to the thermal expansion difference between the substrate and the coating layer, the redox window for Ir(V)/Ir(IV) conversion, and the redox reversibility of Sb and Sn species in the coating layer.     

Photon interaction parameters for some ZnO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Some photon interaction parameters such as mass attenuation coefficient, effective atomic number, half value layer, mean free path and electron density for 15ZnO–(17.5–x)Al₂O₃–xFe₂O₃–67.5P₂O₅ glass system (x = 0, 7.5, 12.5, 17.5) and 15ZnO–(25–x)Al₂O₃–xFe₂O₃–60P₂O₅ glass system (x = 0, 25) have been investigated in the photon energy range of 1 keV to 100 GeV. It has been observed that all the photon interaction parameters for the selected glass systems vary with the photon energy. Among the selected glass systems, the sample 15ZnO–25Fe₂O₃–60P₂O₅ glass system shows maximum values for mass attenuation coefficients, effective atomic numbers, electron densities and minimum values for mean free path and half value layer in the entire energy grid.     

Phase relationships in the Na<Subscript>2</Subscript>ZnP<Subscript>2</Subscript>O<Subscript>7</Subscript>–LiKZnP<Subscript>2</Subscript>O<Subscript>7</Subscript> system

The phase relationships in the Na₂ZnP₂O₇–LiKZnP₂O₇ system are studied. They are represented by a mixture of the starting components in the subsolidus region. The eutectic was found at a temperature of 640°C and composition of 0.5LiKZnP₂O₇. The phase formation of this system is compared with the previously studied NaKZnP₂O₇–LiKZnP₂O₇ system. It is shown that a structural factor affects the geometry of the state diagrams.