3-Hydroxybenzoic acid as AISI 316L stainless steel corrosion inhibitor in a H<Subscript>2</Subscript>SO<Subscript>4</Subscript>–HF–H<Subscript>2</Subscript>O<Subscript>2</Subscript> pickling solution

3-Hydroxybenzoic acid (3-HBA) was studied for possible use as a AISI 316L stainless steel (SS) corrosion inhibitor in an environmental-friendly aqueous pickling solution of 75 g l^–1 sulphuric acid (H₂SO₄), 25 g l^–1 hydrofluoric acid (HF) and 30 g l^–1 hydrogen peroxide (H₂O₂). 3-HBA was tested in concentrations from 5 × 10^–5 to 5 × 10^–1 M at 298 and 313 K temperature. Inhibition efficiency increased with the 3-HBA concentration. The inhibitor mechanism is discussed in terms of the properties of the isotherm equations of Frumkin, Hill-de Boer and Kastening–Holleck mainly. The shape, the trend of the slopes along the curve and the existence of inflection points, were analysed as the characteristics that differentiate one adsorption equation from another. The best fit was obtained using the Frumkin isotherm model. The projected molecular area of 3-HBA was calculated as a structural parameter to elucidate its optimal inhibition mechanism.     

Physicochemical Properties of Nanosized Powders of the LaPO<Subscript>4</Subscript>–DyPO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O System

Nanosized La_1–xDy_xPO₄ · nH₂O powders are synthesized by the sol-gel method using direct and reverse precipitation. The formation of a continuous series of hexagonal solid solutions based on LaPO₄ · nH₂O is confirmed by the XRD and DSC/TG methods. A continuous series of monoclinic solid solutions based on LaPO4 is formed at temperatures higher than 600°C. A reflex corresponding to a tetragonal form of DyPO₄ is formed during the calcination of DyPO₄ powder at 850°C. Two types of solid solutions are observed at temperatures of 1000–1200°C, namely, monoclinic solutions based on LaPO₄ (to x ≈ 0.7) and tetragonal solutions based on DyPO₄ (0.90 ≤ x ≤ 1.0). The results are compared depending on the methods of nanopowder synthesis.     

Synthesis and physicochemical properties of a solid oxide nanocomposite based on a ZrO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>–MgO system

A highly dispersive powder with a (ZrO₂)_0.92(Y₂O₃)_0.03(Gd₂O₃)_0.03(MgO)_0.02 composition and specific surface area of 150 m²/g has been synthesized via a method of coprecipitation of hydroxides with the subsequent cryochemical treatment of the gel. Nanoceramics based on the cubic modification of zirconium dioxide with the grain size of ~40–45 nm have been obtained. The temperature dependence of the specific electrical conductance of the nanoceramics within a temperature range of 350–870°C in air has been studied, and the ratio of the ionic and electronic parts of the conductance has been determined. Recommendations for the use of the obtained oxide nanocomposite as an electrolyte for a high-temperature fuel cell have been given.     

Structural heterogeneity of SiO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>O–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> glass

It is shown that the phase heterogeneity of SiO₂–Na₂O–Al₂O₃ glass has a liquation and crystallization nature, the balance between which is determined by the conditions of their synthesis. An increase in the aluminum oxide content decreases the number of liquation and crystallization sites, and also the linear sizes of the crystalline formations without eliminating the phase separation due to the liquation. The area of metastable immiscibility in the SiO₂–Na₂O–Al₂O₃ system, which is determined by scanning electron microscopy, is probably wider than the area detected by the optical methods.     

Synthesis of low-melting eutectic of the CaO–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> system in a solid phase

Results are provided for a physicochemical study of processes that occur during synthesis of eutectic composition of the CaO–B₂O₃–SiO₂ system in a solid phase, and the possibility of their activation by using starting calcium-containing components with different chemical and thermal prehistory. It is established that independent of the form of starting components, in all cases there is formation of a crystalline eutectic phase, and the sequence of physicochemical processes that occur is determined by the reaction capacity of the calcium compound introduced.     

Vitreous region and properties of glasses of the Ga<Subscript>2</Subscript>S<Subscript>3</Subscript>–GeS<Subscript>2</Subscript>–PbF<Subscript>2</Subscript> system

Vitrification in the Ga₂S₃–GeS₂–PbF₂ system is considered. The physicochemical properties of glasses, such as density, microhardness, electroconductivity, refraction index, and transmission percentage of specimens in visible and IR ranges of spectrum are studied; differential thermal analysis is carried out; and Raman and electron paramagnetic resonance spectra are investigated.     

Structural analyses of RuO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti and IrO<Subscript>2</Subscript>–RuO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti anodes used in industrial chlor-alkali membrane processes

The morphology and composition of RuO₂–TiO₂/Ti and IrO₂–RuO₂–TiO₂/Ti anodes, which have been used for the production of chlorine for more than 10 years, were analyzed by various methods; such as high-resolution scanning electron microscopy, high-resolution Auger electron spectroscopy, electron probe X-ray emission microanalysis and X-ray diffraction analysis. Drastic changes in the surface morphology, including partial exfoliation of a small amount of the oxide layer and a reduction in the content of ruthenium species through dissolution, were observed for the RuO₂–TiO₂/Ti anode. For the IrO₂–RuO₂–TiO₂/Ti anode, on the other hand, there were moderate changes in the surface morphology and moderate dissolution of iridium and ruthenium species.     

Effect of temperature on the synthesis of nanoparticles with different morphology in the system MgO–SiO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>–H<Subscript>2</Subscript>O under hydrothermal conditions

Nanoparticles with different morphology have been obtained by hydrothermal method in the system MgO–SiO₂–TiO₂–H₂O. It has been found that in the investigated temperature–time interval the formation of nanotubes of hydrosilicate with the structure of chrysotile with a small amount of impurity phases predominantly takes place.     

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.     

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.     

Synthesis and properties of binary spinels in a NiO–CuO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The conditions for the formation of a spinel structure from a NiO–CuO–Fe₂O₃–Cr₂O₃ oxide mixture using several technological approaches have been examined. Addition of KCl is accompanied with the formation of two spinel-like phases, whereas in the absence of KCl just one solid solution of nickel–copper ferrite–chromite with the structure of a cubic spinel is formed. At the temperature of thermal treatment of 900°C, the presence of an admixture phase of the delafossite (CuCrO₂) type was established. The conditions for the fabrication of samples containing two spinel phases (cubic and tetragonal) characterized with the most developed surface and manifesting = increased catalytic activity in the reaction of the decomposition of an organic substance by hydrogen peroxide have been formulated. The studied features of spinel synthesis can be of interest for developing materials with an active surface promising for application as adsorbents of catalysts and sensors.     

Vapor–Liquid Equilibrium of Binary Components of the BrCF<Subscript>2</Subscript>COOCH<Subscript>3</Subscript>–CF<Subscript>3</Subscript>COOH–BrCF<Subscript>2</Subscript>COOH–CF<Subscript>3</Subscript>COOCH<Subscript>3</Subscript> Quaternary System

Vapor–liquid equilibria of binary components of the BrCF₂COOCH₃–CF₃COOH–BrCF₂COOH–CF₃COOCH₃ quaternary system have been studied experimentally at constant pressure. The experiments have been carried out on a modified Sventoslavskii ebulliometer. Using the Aspen Plus software package, the appropriate models have been selected and the vapor–liquid equilibria for six binary systems have been simulated.     

Preparation,Infra-red,MAS-NMR and Structural Characterization of a New Copper Based Inorganic–Organic Hybrid Compound: [C<Subscript>5</Subscript>H<Subscript>6</Subscript>N<Subscript>2</Subscript>Cl]<Subscript>2</Subscript>CuCl<Subscript>4</Subscript>

The ionic salt [2(C₅H₆N₂Cl)⁺], [CuCl₄]^2? complex of copper(II) has been synthesized and characterized. The X-ray diffraction analysis with a single crystal of this compound showed that the title compound (4-amino-2-chloropyridinium)₂CuCl₄ [(CAP)₂CuCl₄], crystallized at room temperature in the monoclinic system, space group C_2/c (N°.15) and the following : a = 16.0064 (2) Å; b = 7.7964 (10) Å; c = 14.7240 (2) Å; β = 102.497 (10)°; V = 1793.91 (4) ų and Z = 4. The structure was solved by using 1,589 independent reflections down to R value of 0.021. The unit cell is made up of tetrachlorocuprate(II) anions and 4-amino-2-chloropyridinium cations linked together by an extensive hydrogen bond network of types N–H···Cl (N: pyridinium) and N–H···Cl (N: amine), and cation-lone pair of nitrogen element interactions. Solid state NMR spectra showed one and five isotropic resonances, ⁶³Cu and ¹³C, respectively, confirming the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for single crystal, revealed that the conduction in the material was due to a hopping process. This work aims to reveal the thermal properties of a new copper(II) based organic–inorganic hybrid and the conductivity properties that these compounds exhibit.     

A novel IrO<Subscript>2</Subscript> electrode with iridium–titanium oxide interlayers from a mixture of TiN nanoparticle and H<Subscript>2</Subscript>IrCl<Subscript>6</Subscript> solution

A novel IrO₂ anode on titanium substrate with iridium–titanium oxide interlayer (Ti/IrO _x –TiO₂/IrO₂) was prepared and investigated for oxygen evolution. IrO _x –TiO₂ interlayer was coated on titanium substrate by impregnation-thermal decomposition method from a mixture of TiN nanoparticles and H₂IrCl₆ solution at 500 °C. The results showed that the service life of Ti/IrO _x –TiO₂/IrO₂ was a factor of six times longer than that of Ti/IrO₂, which was attributed to the IrO _x –TiO₂ interlayer, it could form a metastable solid solution between IrO _x and thin titanium oxide layer on titanium substrate during calcination. The interlayer contributed to the decrease in migration rate of oxygen atom or molecule toward substrate and the increase in bonding force among IrO₂ layer, interlayer, and substrate. Therefore, besides keeping high electrocatalytic activity, the service life of Ti/IrO _x –TiO₂/IrO₂ electrode was greatly improved, and its overall electrocatalytic performance for oxygen evolution was increased as well.