Calorimetric studies on 2TeO<Subscript>2</Subscript>–V<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Glasses of the composition 2TeO₂–V₂O₅ were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The glass transition and crystallization parameters were evaluated under non-isothermal conditions using DSC. X-ray diffraction studies confirmed the presence of partially oriented crystallites in the heat-treated glasses. Kauzmann temperature (lower bound for the kinetically observed glass transition) was deduced from the heating rate dependent glass transition and crystallization temperatures.     

Calorimetric study on Ge<Subscript>23</Subscript>Se<Subscript>67</Subscript>Sb<Subscript>10</Subscript>–0.5CsCl glass

The mechanical behavior of Ge₂₃Se₆₇Sb₁₀ glass can be improved by adding CsCl facilitating the nano-crystaline formation. Understanding the crystallization mechanism of chalcogenide glass can help in directing the subsequent annealing processing and tuning the microstructure and physical properties. In this work, 99.5Ge₂₃Se₆₇Sb₁₀–0.5CsCl glass was prepared and its transformation kinetics was investigated under non-isothermal conditions with heating rate up to 400 K min^?1. Using Vogel–Fulcher–Tammann equation, the ideal glass transition temperature was determined as T _0g = 434.1 K. Using the classical JMA theory, the average activation energy and average growth exponent were determined as 135.0 and 2.4 kJ mol^?1, while using the model considering impingements (MCI), the two parameters were determined as 120.9 and 3.2 kJ mol^?1, respectively. Compared to JMA theory, the MCI model can fit the transition curves better, and it shows that the growth mode of the present glass is between two-dimension and three-dimension. By comparing with the result of Ge₂₃Se₆₇Sb₁₀ glass, it is found that addition of CsCl can reduce the growth dimension and activation energy during crystallization.     

Solvent effect on distribution of phenyl groups for C<Subscript>6</Subscript>H<Subscript>5</Subscript>SiO<Subscript>3/2</Subscript>–SiO<Subscript>2</Subscript> coatings prepared on polycarbonate substrate

Phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) coatings [xPhTES·(100 − x)TEOS (mol%)] (x = 0–80) were prepared using methanol (Film A) or 1-propanol (Film B) as a solvent on polycarbonate (PC) substrate, and the effect of alcohol solvents on both the adhesion and distribution of phenyl groups were studied. The alcohol evaporation rates for Films A and B were monitored by using quartz crystal microbalance (QCM). QCM measurements revealed that the migration of phenyl group to the PC substrate side was strongly related with the alcohol solvent. Transmission fourier transform infrared measurements for these films suggest that a phase-separation between SiO₂ and PhSiO_3/2 networks occur during the alcohol evaporation.     

Effects of acid treatment on electrochemical properties of Li<Subscript>2</Subscript>MnO<Subscript>3</Subscript>·LiNi<Subscript>0.5</Subscript>Co<Subscript>0.45</Subscript>Fe<Subscript>0.05</Subscript>O<Subscript>2</Subscript> cathode materials

A new composite, Li₂MnO₃·LiNi_0.5Co_0.45Fe_0.05O₂, can be synthesized by a solid-state method and preconditioned with 5 wt% HCl, H₂SO₄, or H₃PO₄ solution to achieve H⁺/Li⁺ exchange. The effects of acid treatment on the structure, morphology, and electrochemical properties of Li₂MnO₃·LiNi_0.5Co_0.45Fe_0.05O₂ cathode materials are analyzed. The X-ray powder diffraction patterns imply that the hexagonal α-NaFeO₂ structure (space group R\(\bar{3}\)m) of the materials is not changed by the acid treatment. The scanning electron microscope images show that particles become spherical with smooth surfaces after acid treatment, and the Brunauer–Emmett–Teller analysis reveals that the specific surface area increases. The charge–discharge test demonstrates that acid-treated Li₂MnO₃·LiNi_0.5Co_0.45Fe_0.05O₂ cathode materials deliver higher initial coulombic efficiencies than untreated material, owing to the improvement of the catalytic reduction activity of oxygen released during the initial charge process. Furthermore, Li₂MnO₃·LiNi_0.5Co_0.45Fe_0.05O₂ treated with HCl displays the best electrochemical performance, with the acid treatment improving the initial coulombic efficiency from 66.0 to 82.2%. Thus, acid treatment can effectively improve the electrochemical performance of electrode materials in Li-ion batteries.     

Thermoelectric power and electrochemical studies on CdI<Subscript>2</Subscript>–Ag<Subscript>2</Subscript>O–V<Subscript>2</Subscript>O<Subscript>5</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

A quaternary super-ion-conducting system, 20CdI₂ − 80[xAg₂O − y(0.7V₂O₅ − 0.3B₂O₃)] where 1 ≤ x/y ≤ 3, has been prepared by melt quenching technique. The electrical conductivity measured was the order of 10⁻⁴  S/cm at room temperature. The values of silver-ion transport number obtained by electromotive force technique are nearly unity. The thermoelectric power and electrochemical studies were done on the CdI₂–Ag₂O–V₂O₅–B₂O₃ system. The discharge and polarization characteristics were examined for different cathodes to evaluate the utility of these cells as power sources for low energy applications.     

Effect of the Copper Oxide Sintering Additive on the Electrical and Electrochemical Properties of Anode Materials Based on Sr<Subscript>2</Subscript>Fe<Subscript>1.5</Subscript>Mo<Subscript>0.5</Subscript>O<Subscript>6–δ</Subscript>

The effect of introducing 1–3 wt % copper oxide sintering additive on the electrical and electrochemical characteristics of promising anode materials for solid oxide fuel cells based on Sr₂Fe_1.5Mo_0.5O_6–δ was studied. The total conductivity increases with increasing amount of copper oxide. The maximum conductivity in humid hydrogen at 800°C, 45 S cm^–1, was reached on introducing 3 wt % CuO. The sintering additive enhances the electrochemical activity of Sr₂Fe_1.5Mo_0.5O_6–δ and Sr₂Fe_1.5Mo_0.5O_6–δCe_0.8Sm_0.2O_1.9 anodes. A decrease in the sintering temperature of the anodes containing CuO with the electrolyte based on lanthanum gallate directly correlates with the electrochemical activity of the anodes. The minimum value of the polarization resistivity, 0.15 Ω cm² at 800°С in a humid hydrogen atmosphere, was obtained for the composite anode with 3 wt % CuO sintered at a temperature of 1050°С.     

Hydrodeoxygenation of Vegetable Oil on NiMoS/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

Tungstate-containing aluminum oxide is suitable as a catalyst support for hydrodeoxygenation of sunflower oil, ensuring 81–83 wt % yield of liquid products at 380°С, 4.0 MPa, and feed space velocity of 1 h^–1. The catalyst acidity increases with increasing tungsten oxide content, leading to an increase in the content of decarboxylation/decarbonylation products and isoparaffins in the product mixture.     

Influence of A-site deficiencies in the system La<Subscript>0.9</Subscript>Sr<Subscript>0.1</Subscript>Ga<Subscript>0.8</Subscript>Mg<Subscript>0.2</Subscript>O<Subscript>3−δ</Subscript> on structure and electrical conductivity

In this study, the A-site-deficient ABO₃ perovskites La_0.9–x Sr_0.1Ga_0.8Mg_0.2O_3– with x=0.025, 0.05, 0.075, 0.1, and 0.2 were prepared by conventional solid state reactions. X-ray investigations were carried out in order to determine the influence of the A-site deficiencies on the structure. The electrical conductivities were measured as a function of both temperature and oxygen partial pressure in ranges 500–1000 °C and 0.2–10^–6 atm, respectively. Only for small x values were single phases obtained. All compositions with A-site deficiencies exhibit a lower conductivity compared to the stoichiometric compound. It is shown by SEM micrographs that the sample morphology is changed by an A-site-deficient preparation as well. For A-site-deficient compositions, a reduction of the grain size is observed, most likely due to impurity inclusions in the grain boundaries.     

Preparation and characterization of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>Co<Subscript>0.2</Subscript>Fe<Subscript>0.8</Subscript>O<Subscript>3-δ</Subscript> thin-film membrane on porous support by dip-coating method

Perovskite-type La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) thin-film membrane prepared by modified Pechini sol–gel process, was successfully deposited on porous support of similar composition using dip-coating method. Fine grain and crack-free film with perovskite structure was obtained at sintering temperature of 800 °C and dwelling time of 60 min. The cross-sectional image indicated that LSCF6428 thin-film membrane coated on the porous support showed excellent adhesion to the support with uniform thickness. The minimum dense layer thickness obtained by dip-coating method was around 0.5 μm. It was found that the oxygen permeability of the supported thin film was lower than that of the perovskite support, which indicated that the pores of the support were reduced by thin-film deposition on the support surface. The reduction in the pore size led to the more selective permeation mechanism contributes to the overall permeation. Successful deposition of LSCF6428 thin-film membrane on porous support can be considered as a promising technique for the preparation of oxygen separation membrane.     

Effects of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> on the crystallization and structure of CaO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass ceramics

Radiation-induced degradation of the weakly and strongly 4-vinylpyridine basic ion exchange resins by gamma radiolysis was investigated in the presence of air and liquid water. This study is focused on evaluating the radiolytic gases (H₂, CO, CO₂ and CH₄) and liquid products (water-solute TOC and NH₄ ⁺). The weakly basic resin yielded lower amounts of H₂ and CO and higher amounts of CO₂ than those of the strongly basic resin. Moreover, the strong basic resin tended to yield greater amounts of NH₄ ⁺. Resins were characterized by the FTIR spectroscopy technique and the results showed that the resins structures are relatively stable.     

Adsorption of chlorobenzene vapor on V<Subscript>2</Subscript>O<Subscript>5</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst under dynamic conditions

Adsorption dynamics of chlorobenzene vapors on a 5% V₂O₅/Al₂O₃ catalyst has been investigated using the frontal chromatography technique. The uptakes of chlorobenzene have been measured as a function of vapor concentration and adsorption equilibrium has been found to follow formally the Langmuir isotherm. The breakthrough time proved to be a linear function of the column length as expected. Breakthrough profiles have been reported for different experimental conditions and quantitatively fitted by a reduced lumped diffusion model. This model provides an analytical solution that facilitates engineering calculations. Model parameters show complex behavior as functions of stream characteristics and depend on column length. When empirical expressions relating model mass transfer coefficients with influencing variables are found the model demonstrates good accuracy in predicting column performance.     

Effect of ZrO<Subscript>2</Subscript> on Catalyst Structure and Catalytic Sulfur-Resistant Methanation Performance of MoO<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

A series of MoO₃/ZrO₂–Al₂O₃ catalysts was prepared and investigated in the sulfur-resistant methanation aimed at production of synthetic natural gas. Different methods including impregnation, deposition precipitation, and co-precipitation were used for preparing ZrO₂–Al₂O₃ composite supports. These composite supports and their corresponding Mo-based catalysts were investigated in the sulfur-resistant methanation, and characterized by N₂ adsorption–desorption, XRD and H₂-TPR. The results indicated that adding ZrO₂ promoted MoO3dispersion and decreased the interaction between Mo species and support in the MoO₃/ZrO₂–Al₂O₃ catalysts. The co-precipitation method was favorable for obtaining smaller ZrO₂ particle size and improving textural properties of support, such as better MoO₃ dispersion and increased concentration of Mo⁶⁺ species in octahedral coordination to oxygen. It was found that the MoO₃/ZrO₂–Al₂O₃ catalyst with ZrO₂Al₂O₃ composite support prepared by co-precipitation method exhibited the best catalytic activity. The ZrO₂ content in the ZrO₂Al₂O₃ composite support was further optimized. The MoO₃/ZrO₂–Al₂O₃ with 15 wt % ZrO₂ loading exhibited the highest sulfur-resistant CO methanation activity, and excess ZrO₂ reduced the specific surface area and enhanced the interaction between Mo species and support. The N₂ adsorption-desorption results indicated that the presence of ZrO₂ in excessive amounts decreased the specific surface area since some amounts of ZrO₂ form aggregates on the surface of the support. The XRD and H₂-TPR results showed that with the increasing ZrO₂ content, ZrO₂ particle size increased. These led to the formation of coordinated tetrahedrally Mo⁶⁺(T) species and crystalline MoO₃, and this development was unfavorable for improving the sulfur-resistant methanation performance of MoO₃/ZrO₂–Al₂O₃ catalyst.     

Synthesis,microstructure, and electric properties of CaZr<Subscript>0.9</Subscript>Y<Subscript>0.1</Subscript>O<Subscript>3 – δ</Subscript> films obtained on porous SrTi<Subscript>0.8</Subscript>Fe<Subscript>0.2</Subscript>O<Subscript>3 – δ</Subscript> supports

Compact CaZr_0.9Y_0.1O_3–δ (CZY) film on a porous SrTi_0.8Fe_0.2O_3–δ (STF) support is obtained using the technique of deposition from solutions of inorganic salts in ethanol. According to the data of scanning electron microscopy (SEM), the film has a nanoporous granular structure with the grain size of 0.2 to 1 μm. The thickness of the CZY film on the STF support is about 3 μm after 15-fold solution application. The results of studying the elemental composition showed that elements of the support diffuse into the film in the course of synthesis. Analysis of the data of impedance spectroscopy shows that conductivity of the CZY film is limited the grain bulk. It is assumed that the comparatively low conductivity activation energy of the film (50.3 kJ/mol) is due to diffusion of elements of the STF support that results in variation of the film composition and properties.     

Synthesis and Conductivity of CaZr<Subscript>0.9</Subscript>Y<Subscript>0.1</Subscript>O<Subscript>3–δ</Subscript> Electrolyte Films on Supporting Composite Electrodes

Conditions of the chemical solution deposition of CaZrO₃-based electrolyte films on supporting composite electrodes are studied. The films are formed on the composites of CaZrO3 with metal oxides СuO, Fe₂O₃, and NiO. The morphology and the phase and elemental composition of supports and films are studied as well as the gas permeability and conductivity of films. It is concluded that composites of calcium zirconate with nickel can be recommended as the supporting anodes for the proton-conducting CaZr_0.9Y_0.1O_3–δ film electrolyte.     

Lanthanide-Organic Frameworks Based on {Ln<Subscript>4</Subscript>(μ<Subscript>3</Subscript>-OH)<Subscript>4</Subscript>(μ<Subscript>2</Subscript>-OH)<Subscript>2</Subscript>} Cluster Units

Abstract  

Three novel lanthanide-organic frameworks: [Ln₂(pyba)₃(μ₃-OH)₂(μ₂-OH)(H₂O)] _n (Ln = Er (1), Y (2), Dy (3) Hpyba = 4-pyridin-4-yl-benzoic acid) have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Structure analysis shows that each {Ln₄(μ₃-OH)₄(μ₂-OH)₂} cluster units interconnect to form 1-D chains, which are further linked by π–π interactions to make a 3-D supramolecular network structure. Furthermore, the IR, PXRD and TGA of compounds 1–3 were also studied.     

Effect of Fe-zeolite on formation of N<Subscript>2</Subscript>O in selective reduction of NO by NH<Subscript>3</Subscript> over V<Subscript>2</Subscript>O<Subscript>5</Subscript>–WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> catalyst

An approach for significantly suppressing N₂O formation in reduction of NO by NH₃ over V₂O₅–WO₃/TiO₂ (VWT) catalyst has been studied by coating different amounts of a Fe-exchanged zeolite (FeZ) onto the catalyst. FeZ-promoted VWT samples were characterized using N₂ sorption, X-ray diffraction (XRD) analysis, and NH₃ adsorption/desorption techniques to understand the primary role of FeZ in lowering N₂O production levels. At high temperatures (≥450 °C), VWT gave N₂O production with high concentrations, while N₂O formation was noticeably reduced when using FeZ-promoted catalysts, which also showed somewhat lower NO removal activities (<5 %) at all temperatures. N₂ sorption and XRD measurements revealed no perceptible physical or chemical alterations of each constituent, even in VWT catalysts after FeZ coating following high-temperature calcination. Adsorption of NH₃ on unpromoted and FeZ-promoted catalysts and subsequent desorption yielded very complicated spectra for N₂O that might primarily come from NH₃ oxidation, and the interaction between V–NO species at temperatures >580 °C. NO on neighboring sites seems to be produced via decomposition of N₂O generated at lower temperatures. The FeZ in the promoted VWT catalysts could be responsible for N₂O decomposition and N₂O reduction with unreacted NH₃ at temperatures >400 °C, thereby significantly lowering N₂O emission levels. This promotional effect bodes well for use in many industrial deNO _x applications.     

Study on Bi—Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite prepared via mechanochemical processing

In this work Bi-Fe₃O₄ nanocomposite was synthesized by room temperature milling of Bi₂O₃ and Fe powders using a planetary ball mill in air. The synthesis reaction proceeds with increase in milling time and is finished by about 4 h. The XRD pattern of the as-milled powder shows that the main phases are Bi and Fe₃O₄ without any extra phases. The average crystallite sizes of the constituents have been determined by Scherrer’s formula and they were 22 and 18 nm for Bi and Fe₃O₄ respectively. This was also confirmed by Transmission Electron Microscopy (TEM). Magnetic hysteresis loops at room temperature were recorded using a vibrating sample magnetometer (VSM). A tow-probe method was used to measure resistivity variation of the nanocomposite as a function of magnetic filed and temperature. We have observed a room temperature magnetoresistance (ρ₀ — ρ _H )/ρ₀ as large as 17% in a magnetic field of 1 T.     

Influence of synthesis route on morphology and conduction behavior of BaCe<Subscript>0.8</Subscript>Y<Subscript>0.2</Subscript>O<Subscript>3−δ</Subscript>

In this article, the role of the preparation route and calcinations temperature on the thermal expansion and conductivity of BaCe_0.8Y_0.2O_3−δ (BCY) has been studied. In particular, the samples were synthesized by means of the solid-state reaction and by a sol–gel route. BCY has been suggested as proton conducting electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Proton conductivity strongly depends on the densification of the material as well as the crystal structure, which is generally influenced by the preparation procedure. It was found that a single phase material could be achieved at 1000 °C for the samples prepared through the sol–gel route with ~96% packing density. In case of ceramic route, single phase could be obtained at higher temperatures (1200 °C) and does not lead to good density values. The ceramic synthesis produces BCY material in cubic symmetry where as the gel–citrate complexation route leads to homogenous orthorhombic BCY. The conductivity measurements of sample synthesized by two different routes were investigated by means of impedance spectroscopy and electron microscopy. A comparative study of thermal expansion behavior of BCY synthesized by different route was carried out.     

Characterization of gold supported on Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–CuO–Mn<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts obtained by thermal decomposition of aerosols

The purpose of this work was to employ the differential thermal analysis (DTA) technique to compare variations in the collapse energy of the zeolite Y crystalline structure in a fresh catalyst and in the same catalyst impregnated with nickel and vanadium. A small exothermic signal in the DTA curve at 950–1150 °C indicated the collapse of the crystalline structure. The areas of the exothermic signals in the DTA curves of the two samples indicated a reduction in the curve of the metal impregnated catalyst. These results were compared with X-ray data, leading to the conclusion that metal impregnation affects the zeolite Y crystalline structure and that the DTA technique is a potentially useful tool for measuring the integrity of zeolite Y in catalysts.     

In-situ construction of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoarrays on La<Subscript>0.8</Subscript>Sr<Subscript>0.2</Subscript>MnO<Subscript>3-δ</Subscript> electrodes for intermediate temperature solid oxide fuel cells

Novel NiCo₂O₄ nanoarrays have been in-situ grown on a La_0.8Sr_0.2MnO_3-δ(LSM) cathode through a hydrothermal method, which presents the enhanced electrochemical performances of the LSM cathode for the intermediate temperature solid oxide fuel cells. XRD and SEM have been used to characterize phase structure and morphology of NiCo₂O₄ nanoarrays. The LSM cathode, modified by the NiCo₂O₄ nanoarrays, exhibits excellent electrochemical performances compared with the bare LSM cathode. The maximum peak power density of single cell, based on the NiCo₂O₄ nanoarrays modified the LSM cathode, reaches 957 mW cm^?2 at 800 °C, which is almost two times higher than that for the cell based on the bare LSM cathode.