Calculation of phase diagrams of heterophase two- and three-component liquid mixtures ‘α-pinene-water’ and ‘α-pinene-water-ethanol’

Phase behaviors of two- and three-component mixtures ‘α-pinene-water’ and ‘α-pinene-ethanol-water’ were studied over a wide range of their composition, temperature, and pressure. Conditions were found that provide heteroazeotropic states of binary mixture ‘α-pinene-water’ and ternary mixture ‘α-pinene-ethanol-water’ depending on the ratio of ‘water/(α-pinene+ethanol)’ fractions at the ‘α-pinene+ethanol’ ratio of 1:1. Critical curves were calculated to demonstrate an anomalous dependence of these curves on the mixture composition, with the temperature minimum points typical of the mixtures that form heteroazeotropes.     

Effect of Field Strength and Electronegativity of CaO and MgO on Structural and Optical Properties of SiO<Subscript>2</Subscript>–K<Subscript>2</Subscript>O-CaO-MgO Glasses

The glass composition 55 SiO₂-10 K₂O-(35-x) CaO-(x) MgO (0 ≤ x ≤ 30) is prepared by the melt quenched technique. The as prepared samples are characterized by X-ray diffraction, Fourier Transform-Infrared Spectroscopy (FT-IR) and UV-Visible reflectance spectroscopy. The MgO containing glasses show better polymerization (cross-linking) and have a compact glass network as compared to CaO containing glass. Interestingly, some weak bonds are observed around 1393, 1461 and 1530 cm^-1 in FT-IR spectra related to Ca/Mg-O-H. The optical band gap of the series varies from 3.42 eV to 3.72 eV, indicating wide-band gap materials that could be used in non-linear optical applications.     

Identification of Δ<Superscript>7</Superscript> phytosterols and phytosteryl glucosides in the wood and bark of several <Emphasis Type="Italic">Acacia</Emphasis> speciesphytosterols and phytosteryl glucosides in the wood and bark of several <Emphasis Type="Italic">Acacia</Emphasis> species

The wood and bark of four Acacia species growing in Portugal, namely, A. longifolia, A. dealbata, A. melanoxylon, and A. retinodes, were investigated for their sterol content. The lipids fractions of the different wood and bark samples were isolated, and the sterols were identified and quantified by GC-MS. Two Δ⁷ sterols, specifically, spinasterol and dihydrospinasterol, were the main sterols found in considerable amounts, particularly in wood tissues (more than 0.5 g/kg of dry wood in the case of A. melanoxylon and A. retinodes). The corresponding unusual steryl glucosides were also identified in significant amounts in the wood and bark extracts.     

Synthesis and study of mesoporous xerogels and nanopowders of a metastable solid solution 97ZrO<Subscript>2</Subscript>–3Y<Subscript>2</Subscript>O<Subscript>3</Subscript> for the fabrication of catalyst substrates

The—technology of the liquid-phase synthesis of metastable phases in the ZrO₂–Y₂O₃ system has been developed. Mesoporous xerogels with the specific surface area of ~350 m²/g and monophase nanopowders (5–10 nm) of the tetragonal solid solution (ZrO₂)_0.97(Y₂O₃)_0.03 have been obtained and their structural peculiarities have been revealed. The efficiency of the suggested technology and good prospects of the synthesized ZrO₂-based precursors in creating catalysts’ substrates have been demonstrated.     

Effect of Zr/Si molar ratio and sulfation on structural and catalytic properties of ZrO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> mixed oxides

ZrO₂–SiO₂ mixed xerogel and aerogel samples with varied molar ratios were prepared by sol–gel method followed by oven drying and supercritical drying using n-propanol as a solvent, respectively. Sulfation was carried out to further enhance the acidic properties of the mixed oxides. Effect of drying, Zr/Si molar ratio and sulfation have been studied and correlated with the structural, textural and catalytic properties of ZrO₂–SiO₂ mixed oxides. Both xerogel and aerogel mixed oxides have different structural and textural features, however, the total number of acid sites per unit surface area (0.0021–0.0029 mmol NH₃ m⁻²) and thus the catalytic activity for cyclohexanol conversion (31–41%) was found in the similar range. Sulfated mixed oxide aerogel and xerogel samples showed significant enhancement of cyclohexanol conversion (91–99%).     

The Symmetric and Topological Code of the Cluster Self-Assembly of the Crystal Structure of ε-Mg<Subscript>23</Subscript>Al<Subscript>30</Subscript> of K63 Nanoclusters

The geometrical and topological analysis of the crystal structure of intermetallide ε-Mg₂₃Al₃₀ (ToposPro program) with V = 3098.0 ų and space group R-3 is carried out. The symmetric and topological codes of the cluster self-assembly of the crystal structure are determined: primary chain S ₃ ¹ → microlayer S ₃ ² → microframework S ₃ ³ . A new type of nanocluster-precursor of the crystal structure, which is formed on the internal 13-atomic cluster, which represents a template and consists of two bound ridged rings Mg–Al–Mg–Al–Mg–Al with the central Mg atom, is discovered. A quasi-spherical deltahedron shell made from 50 atoms is formed on the template. The center of a K63 cluster occupies the position with the point symmetry 3? in the unit cell. There are six neighboring K63 clusters in the local environment of the K63 cluster in the layer. The basic 3D network, which characterizes the location of the gravity centers of the K63 clusters, corresponds to a hexagonal closely packed network (HCP, Mg type) with CN = 12. The localization of two Mg atoms in the pores of the framework is determined.     

Combustion chemistry of ternary blends of hydrogen and C<Subscript>1</Subscript>–C<Subscript>4</Subscript> hydrocarbons at atmospheric pressure

Interest in the combustion chemistry of multifuel blends is motivated by the need to study the combustion of natural gas, which is known to be a mixture of alkanes. The present study performed using molecular beam mass spectrometry and numerical modeling has shown that the width of the zones of hydrogen and methane consumption in the H₂/CH₄/C₃H₈/O₂/Ar flame and the width of the zones of methane and propane consumption in the CH₄/C₃H₈/C₄H₁₀/O₂/Ar flame differ significantly from each other. The causes of this phenomenon were determined by analyzing the modeling results. It has been found that in the presence of heavier compounds, lighter fuels, such as H₂ and CH₄, are formed, which reduces the total rate of their consumption and, hence expands the zone of their consumption in the flame. The influence of the presence of hydrogen in the fuel mixture on the concentration of C₂ hydrocarbons has also been studied. It has been established that the addition of hydrogen reduces the maximum concentration of ethane, ethylene, and acetylene in the flame, and the fraction of unsaturated C₂ hydrocarbons with respect to saturated ones also decreases.     

Synthesis and research of nanopowders composed of 0.97ZrO<Subscript>2</Subscript> · 0.03La<Subscript>2</Subscript>O<Subscript>3</Subscript>

This work is devoted to the preparation of zirconium oxide nanopowders stabilized by lanthanum oxide using the method of codeposition in the presence of hydrogen peroxide. Nanopowders composed of 0.97ZrO₂ · 0.03La₂O₃ with particles of 10–20 nm are obtained. It is found that in the temperature interval of 500–1100°C the tetragonal and monoclinic points of the zirconium oxide phase crystallize at the same time.     

Analysis of the Parameters of the Mössbauer Spectra and the Spectra of Nuclear Quadrupole Resonance of the Superconducting Ceramic YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7</Subscript>

The parameters of the Mössbauer spectra on ⁶⁷Cu(⁶⁷Zn), ⁶⁷Ga(⁶⁷Zn) isotopes, and the data of nuclear quadrupole resonance on an ¹⁷O isotope are anlayzed, and the lattice gradient of the electric field for the crystal lattice YBa₂Cu₃O₇ is calculated. It is shown that these parameters correspond to the model when the hole is predominantly in the sublattice of the oxygen chain.     

Micro- and nanocomposite particles of the Cu–TiO<Subscript>2</Subscript> system

The micro- and nanocomposite particles of the Cu–TiO₂ system are synthesized using the laser scanning of a heliumlike film. A model of nanostructure formation on a dielectric surface is proposed.     

Electrodeposition and tribocorrosion behaviour of ZrO<Subscript>2</Subscript>–Ni composite coatings

With the objective of producing new functional surfaces with enhanced tribo-corrosion properties we have investigated the electrochemical codeposition of composites in which an electrodeposited metal (nickel) is the matrix and a transition metal oxide (ZrO₂) is the dispersed phase. This paper describes the effect of ZrO₂ dispersed particle codeposition on nickel electrocrystallisation steps as well as the tribocorrosion behaviour of the composite coatings obtained. This system was selected because nickel is an industrially important coating material on steel and other support materials. The cathodic polarization curves have been plotted both in the presence and absence of the insoluble dispersed phase. Electrochemical impedance spectroscopy was used to obtain additional information on the early steps of nickel and nickel matrix composite electrodeposition. Impedance data were acquired with a Solartron type electrochemical interface and frequency response analyzer. A schematic codeposition mechanism is proposed. The influence of zirconium oxide on the nickel electrodeposition steps is discussed. The tribocorrosion properties of ZrO₂–Ni composite coatings (100 μm thickness) have been studied in 0.5 M K₂SO₄ solution on a pin on disc tribo-corrosimeter connected to an electrochemical cell. The normal force applied was 10 N at a rotation speed of 120 rpm. The counterbody (pin) was a corrundum cylinder (7 mm in diameter), mounted vertically on a rotating head, above the specimen. The lower spherical end (radius = 100 mm) of the pin was then applied against the composite surface (disc).     

Facile Synthesis of Ag–γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Superior Nanocomposite for Catalytic Reduction of Nitroaromatic Compounds and Catalytic Degradation of Methyl Orange

A facile synthetic route for preparing silver-doped maghemite (Ag–γ-Fe₂O₃) nanocomposite via a modified co-precipitation method was developed. The prepared magnetic nanocomposite was characterized by means of thermal analysis, transmission electron microscope, X-Ray diffraction, vibrating sample magnetometer and Fourier transform infrared techniques. The characterization results showed that the prepared Ag–γ-Fe₂O₃ nanocomposite is nanocrystalline and 6–8 nm in size with superparamagnetic behavior. The synthesized Ag–γ-Fe₂O₃ nanocomposite showed exceptional catalytic activities towards reduction of nitroaromatic compounds with specific activities parameters of 1441.7 and 904.2 s^??1 g_Ag^?1 for both 4-nitrophenol and 2-nitroaniline, respectively. Besides, it shows a superior activity for catalytic degradation of methyl orange. All the three catalytic reactions were carried out in aqueous medium at room temperature and in the presence of reducing agent NaBH₄. The magnetic behavior of the synthesized Ag–γ-Fe₂O₃ enables the ease of separation of the nanocomposite from the reaction medium for further reuse.

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Synthesis,structural, thermal,optical and dielectric properties of chitosan biopolymer; influence of PVP and <Emphasis Type="Italic">α</Emphasis>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanorods

The present work reports the influence of Polyvinylpyrrolidone (PVP) and hematite (α-Fe₂O₃) nanorods (NRs) on the physicochemical properties of chitosan (Cs), as an approach to broaden its medical and technological applications. Hematite NRs of 11.4 nm diameter and 87.9 nm crystallite size were prepared by a free-template chemical method. Cs, PVP/Cs and blend loaded with hematite NRs were prepared by solution casting. Significant changes in the films’ surface were clarified using the scanning electron microscope (SEM). Fourier transformation infrared spectroscopy (FT-IR) confirmed the interaction between the NRs and the NH₂ and OH functional groups of Cs. DSC measurements showed one endothermic peak assigned to the water elimination, and an exothermic one, in the range 268–287 °C, attributed to the decomposition of saccharine structure in Cs. The swelling properties of the films were sensitive to the pH of the solution. PVP/Cs film showed ~ 85% transmittance in the visible region and its optical band gap narrowed from 5.4 eV to 4.05 eV after loading with 2.0 wt.% hematite. The influence of NRs content on the optical constants of the films is discussed. The dielectric properties depend on the film’ structure. The large Polaron tunneling (LPT) model is the best suitable mechanism for the electric conduction. Due to their high thermal stability and decomposition temperature, transmittance and high conductivity, the prepared films are a candidate for the packaging industry, for use in some medical applications such as treating some chronic wounds, and optical windows and fibers.     

Corrosion- and wear-resistant properties of Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite coatings containing various forms of alumina

This article describes the effect of the addition of different phases of alumina particles on the properties of electrodeposited Ni–Al₂O₃ composite coatings. The corrosion- and wear-resistant properties of Ni–Al₂O₃ composite coatings electrodeposited from a nickel sulfamate bath containing (i) alpha-alumina particles (Ni–Al₂O₃-1), (ii) gamma-alumina particles (Ni–Al₂O₃-2), and (iii) mixture of alpha, gamma, and delta alumina particles (Ni–Al₂O₃-3) have been studied. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed superior corrosion resistance of Ni–Al₂O₃-2 composite coatings compared with other two coatings. The SEM images and EDAX spectra also corroborated well with the observed corrosion results. The pin-on-disk wear studies showed improved wear resistance of Ni–Al₂O₃-1 composite coating containing alpha alumina compared with other two coatings. The transfer of material from the pin onto the disk was evident from the optical microscopy images of the wear tracks and Raman spectra of the wear track. This study shows that the addition of pure gamma-alumina particles enhances the corrosion resistance, and that pure alpha-alumina particles enhance the wear resistance of Ni composite coatings to a greater extent.     

Synthesis and Physicochemical Properties of Nanopowders and Ceramics in a CeO<Subscript>2</Subscript>–Gd<Subscript>2</Subscript>O<Subscript>3</Subscript> System

Nanopowders with a composition of (СeO₂)_1–x(Gd₂O₃)_x (x = 0.03, 0.05, 0.07, and 0.10) are synthesized by the coprecipitation method using cryotechnologies. The coherent scattering region (CSR) of the powders is 10–14 nm and the specific surface area is 70–81 m²/g. Based on the powders, ceramic nanosized materials with CRS of 64–71 nm are obtained. The dependence of the phase composition, microstructure, and electrical transport properties of the obtained samples on the Gd₂O₃ content is established. In a CeO₂–Gd₂O₃ system, a solid solution with the composition of (CeO₂)_0.90(Gd₂O₃)_0.10 has the highest ionic conductivity with the transfer number of ions of t_i = 0.74 at a temperature of 700°C. It is shown that ceramics of this composition can be used as a solid electrolyte of intermediate-temperature fuel cells due to their physicochemical characteristics.     

Effect of preparation procedure of Iro<Subscript>2</Subscript>–Nb<Subscript>2</Subscript>o<Subscript>5</Subscript> anodes on surface and electrocatalytic properties

The influence of the electrode manufacturing procedure on surface and electrocatalytic properties for oxygen and ozone evolution at electrodes of nominal composition Ti/[IrO₂–Nb₂O₅] (45:55 mol%) was investigated. Thermal decomposition at 450 °C (1 h, air stream) was adopted as standard procedure. Metal support pretreatment, solvent mixture, method of applying the precursor mixture and calcination procedure were all investigated. X-ray diffraction, scanning electronic microscopy, voltammetric and differential capacity analysis show the use of HCl 1:1 as solvent and applying the mixture by brush led to fragile rugged/porous oxide coatings. However, for the same conditions, but controlled calcination (heating/cooling rates), the coating becomes more compact. Using isopropanol as solvent results in a more homogeneous coating, presenting the lowest morphology factor. Kinetic investigation shows the rugged/porous coating presents the lowest Tafel slopes and the highest global electrocatalytic activity for OER. The more compact the coating the lower the electrochemically active surface area and the global OER activity. Ozone efficiency depends on the electrochemically active area while support pretreatment strongly influences the lifetime of the electrode. Application of a Pt interlayer between the oxide and Ti base improves the service life.     

Crystal structure of new polymorphic modification β-Ca<Subscript>3</Subscript>B<Subscript>2</Subscript>SiO<Subscript>8</Subscript>, β-α phase transition and thermal expansion of α- and β-modifications

Single crystals of the β-Ca₃B₂SiO₈ new monoclinic modification have been obtained by cooling the melt of a stoichiometric composition. The crystal structure has been determined from the single crystal X-ray diffraction data and refined with R = 0.059 (wR = 0.069) in the monoclinic space group P2₁/m. The thermal behavior of the synthetic borosilicate has been studied. At 472 ± 5°С, a reversible phase transition of the first order occurs, leading to the formation of the orthorhombic α-Ca₃B₂SiO₈ modification. The thermal expansion of α- and β-modifications of Ca₃B₂SiO₈ is anisotropic: (α₁₁ = 15, α₂₂ = 16, α₃₃ =–1, α _V = 30 × 10^–6°С–1) and α₁₁ = 9, α₂₂ = 28, α₃₃ = 1, α _V = 38 × 10^–6°C–1, respectively.     

STudy of the physicomechanical properties of modified raw materials of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> – SIC – C composites based on HAC and ACPB

Results are given for a study of the dependence of apparent density and ultimate strength in compression on the quantity of silica and form of modifying addition (Al, Si, B and mixtures of them) for materials of the composition Al₂O₃ – SiC – C based on high-alumina cement and aluminochromium phosphate binder after low-temperature (400°C) heat treatment. It is established that the most efficient form the point of view of compaction and strengthening of raw material of corundum-graphite refractory is addition of aluminum powder.     

Synthesis and evaluation of NiO@MCM-41 core–shell nanocomposite in the CO<Subscript>2</Subscript> reforming of methane

In this paper, the synthesis of core shell structured NiO@MCM-41 nanocomposite via vesicles as soft template is reported for the first time. Its catalytic performance was investigated in the CO₂ reforming of methane (CRM) conversion. Stable vesicles first formed with CTAB/SDBS surfactant ratio of 1:2. Nickle nitrate was added to the vesicle mixture followed by addition of the aqueous solution of vesicle containing Ni cations inside to the MCM-41 gel. After high-temperature calcination, NiO@MCM-41 nanocomposite were obtained. The structural symmetry and the surface morphology were characterized by transmission electron microscope (TEM), low angle X-Ray Diffraction (XRD) and N₂ adsorption/desorption analysis. TEM image confirmed core–shell structure and the hexagonally ordered structure of shell of MCM-41 silica. The results indicated that the average diameter of synthesized core–shell NiO@MCM-41 particles is 70–80 nm and the most of them are of spherical shape. The result of small angle XRD and N₂ isotherm adsorption/desorption analyses indicated successfull formation of mesoporous shell. Hydrogen consumption by the catalyst mainly at 700 °C in TPR profile showed the strong interaction of the most of Nickel content with the support. CRM conversion on the prepared catalyst after 245 min of reaction led to H₂ conversion at 42%, CO₂ conversion at 48% with H₂/CO yield ratio of 0.8.