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.     

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.     

Regime of superhigh reactivity of the YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6 + δ</Subscript> superconductor toward the components of air

Physicochemical features of the YBa₂Cu₃O_{6 + δ} superconductor synthesized via ceramic route and subjected to a kind of modification by long-term exposure to an atmosphere with low pH₂O have been studied by X-ray diffraction, thermal analysis, and magnetometry. The resulting material had a high degree of saturation with air components at room temperature and 30% humidity, up to 1.5 wt % in 30 days, which is not inherent in YBa₂Cu₃O_{6 + δ}.     

Thermodynamic analysis of the structure of aqueous solutions of C<Subscript>12</Subscript>–C<Subscript>18</Subscript> hydrocarbons

Thermodynamic cycles including the increments \(\Delta G_{CH_2 }^0 , \Delta H_{CH_2 }^0 \), and \(T\Delta S_{CH_2 }^0 \) were constructed for dissolution, evaporation, hydrophobic hydration of C₅–C₉ hydrocarbons, and transfer from vapor (\(\Delta G_{CH_2 }^0 \) = ?0.7 kJ·mol^?1, \(\Delta H_{CH_2 }^0 \) = 2.9 kJ·mol^?1, \(T\Delta S_{CH_2 }^0 \) = 3.6 kJ·mol^?1) and water (\(\Delta G_{CH_2 }^0 \) = ?1.4 kJ·mol^?1, \(\Delta H_{CH_2 }^0 \) = 5.8 kJ·mol^?1, \(T\Delta S_{CH_2 }^0 \) = 7.2 kJ·mol^?1) to micelles of C₁₂–C₁₈ hydrocarbons. The formation of bistable hydrated micelles of C₁₂–C₁₈ is explained by a transition between the order-disorder states in an assembly of small (nano) systems of water. The extensive parameters of small systems and critical phenomena predicted by fluctuation theory are discussed.     

Crystal structure of α-Ag<Subscript>8</Subscript>S<Subscript>3</Subscript>SO<Subscript>4</Subscript>

The crystal structure of silver sulfide-sulfate α-Ag₈S₃SO₄ was determined by X-ray powder diffraction data. The substance crystallizes in the tetragonal system and the space group P-4 with the unit cell parameters of α = 7.2032(4) Å, c = 5.1043(5) Å, Z = 1, R _f = 5.55%, χ² = 3.45. The layers in the structure of the compound formed by trigonal prisms of Ag₆S connected to each other through the vertices are connected by the additional atoms of sulfur into a three-dimensional framework. Distorted tetrahedral anions of SO ₄ ^2? are located in the cavities of the framework, the symmetry (D _2d ) of which was confirmed by the data of IR spectroscopy.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Impedance Study of the Conductivity of Solid Oxide Electrolyte Films SrZr<Subscript>0.95</Subscript>Y<Subscript>0.05</Subscript>O<Subscript>3–δ</Subscript> and CaZr<Subscript>0.9</Subscript>Y<Subscript>0.1</Subscript>O<Subscript>3–δ</Subscript>

Information on the across-plane conductivity of films of solid-oxide electrolytes SrZr_0.95Y_0.05O_3–δ and CaZr_0.9Y_0.1O_3–δ deposited on ion-conducting supports is acquired by the impedance method. It is shown that the support/film interface and the intergrain boundaries considerably affect the across-plane charge transfer in the film. The effect of the crystallographic orientation of the YSZ support on the microstructure and conductivity of the CaZr_0.9Y_0.1O_3–δ electrolyte film is demonstrated.     

Modification of mixed conducting Ba<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>Co<Subscript>0.8</Subscript>Fe<Subscript>0.2</Subscript>O<Subscript>3–δ</Subscript> by partial substitution of cobalt with tungsten

The Ba_0.5Sr_0.5Co_0.8–xW_xFe_0.2O_3–δ (х = 0–0.1) materials prepaMIECred by partial substitution of cobalt in BSCF with tungsten were studied. The tungsten solubility limit in the structure of cubic perovskite BSCF was shown to be ~2%. The doping with the highly charged W⁶⁺ (2%) cation improved the functional properties of BSCF: it increased the oxygen permeability and membrane stability in the CO₂-containing atmosphere and suppressed the cubic–hexagonal perovskite polymorphic transition. This stabilizes high oxygen fluxes during long-term stability tests.     

Non-isothermal kinetics of thermal decomposition of NH<Subscript>4</Subscript>ZrH(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·H<Subscript>2</Subscript>O

Nanocrystalline NH₄ZrH(PO₄)₂·H₂O was synthesized by solid-state reaction at low heat using ZrOCl₂·8H₂O and (NH₄)₂HPO₄ as raw materials. X-ray powder diffraction analysis showed that NH₄ZrH(PO₄)₂·H₂O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH₄ZrH(PO₄)₂·H₂O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP₂O₇. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH₄ZrH(PO₄)₂·H₂O and crystallization of ZrP₂O₇ were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH₄ZrH(PO₄)₂·H₂O thermal decomposition and crystallization of ZrP₂O₇ were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol⁻¹, respectively. Dehydration of the crystal water of NH₄ZrH(PO₄)₂·H₂O could be due to multi-step reaction mechanisms: deamination of NH₄ZrH(PO₄)₂ and intramolecular dehydration of the protonated phosphate groups from Zr(HPO₄)₂ are simple reaction mechanisms.     

Kinetics and thermodynamics of thermal decomposition of NH<Subscript>4</Subscript>NiPO<Subscript>4</Subscript>·6H<Subscript>2</Subscript>O

The single phase NH₄NiPO₄·6H₂O was synthesized by solid-state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. XRD analysis showed that NH₄NiPO₄·6H₂O was a compound with orthorhombic structure. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involves the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. In the DTA curve, the two endothermic peaks and an exothermic peak, respectively, corresponding to the first two steps’ mass loss of NH₄NiPO₄·6H₂O and crystallization of Ni₂P₂O₇. Based on Flynn–Wall–Ozawa equation, and Kissinger equation, the average values of the activation energies associated with the thermal decomposition of NH₄NiPO₄·6H₂O, and crystallization of Ni₂P₂O₇ were determined to be 47.81, 90.18, and 640.09 kJ mol⁻¹, respectively. Dehydration of the five crystal water molecules of NH₄NiPO₄·6H₂O, and deamination, dehydration of the crystal water of NH₄NiPO₄·H₂O, intramolecular dehydration of the protonated phosphate group from NiHPO₄ together could be multi-step reaction mechanisms. Besides, the thermodynamic parameters (ΔH ^≠, ΔG ^≠, and ΔS ^≠) of the decomposition reaction of NH₄NiPO₄·6H₂O were determined.     

Photoresist Modification of Sol–Gel Solutions for Texturing of Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> and Bi<Subscript>3</Subscript>TiNbO<Subscript>9</Subscript> Thin Films

Bismuth titanate (Bi₄Ti₃O₁₂) and bismuth titanium niobate (Bi₃TiNbO₉) c-axis textured thin films were fabricated using the sol–gel processing technique. Chemical modification of precursor solutions was performed using a proprietary photosensitive chemical (photoresist). Increases in crystallinity and texture of resulting films were seen over films that were made from unmodified solutions. Analysis by X-ray diffraction (XRD) revealed c-axis orientation factors for Bi₄Ti₃O₁₂ near 88% and Bi₃TiNbO₉ near 63% in “modified” films. Atomic force microscopy images of films show microstructural improvement between “modified” and “unmodified” films. Images generally show smaller randomly oriented grains in “unmodified” films, and larger oriented platelet structures related to growth due to crystal habit in “modified” films. Light scattering experiments show the addition of photoresist to the precursor solution initiates accelerated particle growth. AFM imaging of soft-baked films also suggests an enhancement of texture.     

Study of dielectric characteristics of graded Ba<Subscript>1−x</Subscript>Ca<Subscript>x</Subscript>Zr<Subscript>0.05</Subscript>Ti<Subscript>0.95</Subscript>O<Subscript>3</Subscript> thin films grown by a sol-gel process

The compositionally graded Ba_1−xCa_xZr_0.05Ti_0.95O₃ (x = 0, 0.05, 0.10) (BCZT) thin films with compositional gradient from BaZr_0.05Ti_0.95O₃ to Ba_0.90Ca_0.10Zr_0.05Ti_0.95O₃ were deposited on Pt/Ti/SiO₂/Si substrates by sol-gel processing. The crystal structure of the thin films was determined by X-ray diffraction. Field emission scanning electron microscopy (FESEM) was used to examine crystallite size and morphology of compositionally graded thin films. The dielectric properties of compositionally graded thin films were characterized by measuring the dielectric constant and dielectric loss as a function of temperature, applied electric field and frequency. As a result, compositionally graded thin films with weak temperature dependence were realized. Dielectric constant peaks, common to a ferroelectric transition, were not observed in the temperature range from 298 to 413 K. The compositionally graded BCZT thin films with weak temperature dependence of tunability could be attractive materials for frequency and phase agile tunable microwave components such as tunable filters, tunable oscillators, and phase shifters for application in phased array antennas.     

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.     

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.     

Crystal structure of glycine phosphite C<Subscript>2</Subscript>H<Subscript>5</Subscript>NO<Subscript>2</Subscript>·H<Subscript>3</Subscript>PO<Subscript>3</Subscript>

Single crystal X-ray diffraction study of glycine phosphite C₂H₅NO₂·H₃PO₃ was performed (monoclinic, space group P2₁/c, a = 7.401(3) Å, b = 8.465(3) Å, c = 9.737(3) Å; β = 100.73(5)°, Z = 4). It has been found that one of hydrogen atoms is located at the centre of symmetry forming two strong hydrogen bonds to yield H₄P₂O ₆ ^?2 dimers, while another hydrogen atom is statistically disordered over two positions and organizes the dimers into an infinite corrugated chain. The ordering of this hydrogen atom position and/or displacement of the other one from the centre of symmetry will lead to the loss of symmetry centre and lowering of the point group symmetry from C_2h to piezo-active group C₂ or C _s .     

Effect of mechanical activation of reagents’ mixture on the high-temperature synthesis of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiB<Subscript>2</Subscript> composite powder

A powder mixture of Al/TiO₂/H₃BO₃ = 10/3/6 in molar ratio was used in this study to form the Al₂O₃–TiB₂ ceramic composite via thermite reactions (combustion synthesis). As no combustion synthesis occurred for an unmilled sample in a furnace, the mixture was milled in a planetary ball-mill for various milling times, and the as-milled samples were in situ synthesized in the furnace at a heating rate of 10 °C/min. The differential scanning calorimetry (DSC) measurements were performed with the same heating rate on the unmilled and the as-milled samples to evaluate the influences of the milling on the mechanisms and efficiencies of reactions. Although no combustion synthesis occurred for the unmilled sample in the furnace, two exothermic peaks were detected in its DSC curve after the melting of the Al. For the as-milled samples, significant changes revealed in the DSC curves, suggest that the milling process before the combustion synthesis changed the mechanisms and efficiencies of reactions. In addition, the intensity and the temperature of the exothermic peaks in the DSC curves changed by increasing the milling time. According to the XRD analyses, by enhancing the milling time, the purity of the final products would increase, confirming that the efficiency of the reactions increased. Finally, the microstructures of the as-milled and as-synthesized samples were examined by a SEM, and it was shown that the morphology of the reactant powders was altered by increasing the milling time.     

Oxidation of Adamantane with H<Subscript>2</Subscript>O<Subscript>2</Subscript>–CF<Subscript>3</Subscript>COCF<Subscript>3</Subscript> · 1.5 H<Subscript>2</Subscript>O in the Presence of VO(acac)<Subscript>2</Subscript>

The system hydrogen peroxide–hexafluoroacetone sesquihydrate effectively oxidizes adamantane in the presence of VO(acac)₂ to afford 64% of adamantan-1-ol in tert-butyl alcohol or 76% of adamantan-2-one in a mixture of acetic acid with pyridine.     

Interpretation of partial thermal decomposition mechanism of Dy<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>·8H<Subscript>2</Subscript>O

Partial dehydration of Dy₂(SO₄)₃·8H₂O was studied employing TG, DSC, D.C. electrical conductivity and spectroscopic techniques. The possible mechanism for the loss of water molecules (partial dehydration) was found to be random nucleation obeying Mapel equation based on TG trace. The DSC traces are supports the results of TG traces and are also utilized to understand the enthalpy changes accompanying the partial dehydration and phase transition accompanying the dehydrated samples. D.C. electrical conductivity studies are attempted to supplement these TG studies. Attempts are made to explain the structural changes accompanying dehydration on the basis of infrared spectra and X-ray diffraction and scanning electron microscopic studies.