Electrochemical study of the codeposition of Mg–Li–Al alloys from LiCl–KCl–MgCl<Subscript>2</Subscript>–AlCl<Subscript>3</Subscript> melts

This work presents a novel electrochemical study on the codeposition of Mg, Li and Al on a molybdenum electrode in LiCl–KCl–MgCl₂–AlCl₃ melts at 943 K to form Mg–Li–Al alloys. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of magnesium on pre-deposited aluminum leads to the formation of a liquid Mg–Al solution, and the succeeding underpotential deposition of lithium on pre-deposited Mg–Al leads to the formation of a liquid Mg–Li–Al solution. Chronopotentiometric measurements indicated that the codeposition of Mg, Li and Al occurs at current densities lower than −0.47 A cm⁻² in LiCl–KCl–MgCl₂ (0.525 mol kg⁻¹) melts containing 0.075 mol kg⁻¹ AlCl₃. Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Al is −2.100 V, and the codeposition of Mg, Li and Al is formed when the applied potentials are more negative than −2.100 V. The diffusion coefficient of aluminum ions in the melts was determined by different electrochemical techniques. X-ray diffraction and inductively coupled plasma analysis indicated that α, α + β and β Mg–Li–Al alloys with different lithium and aluminum contents were obtained via potentiostatic and galvanostatic electrolysis.     

Study on the preparation of Mg–Li–Mn alloys by electrochemical codeposition from LiCl–KCl–MgCl<Subscript>2</Subscript>–MnCl<Subscript>2</Subscript> molten salt

This study presents a novel electrochemical study on the codeposition of Mg, Li, and Mn on a molybdenum electrode in LiCl–KCl–MgCl₂–MnCl₂ melts at 893 K to form different phases Mg–Li–Mn alloys. Transient electrochemical techniques such as cyclic voltammetry, chronopotentiometry, and chronoamperometry have been used in order to investigate the codeposition behavior of Mg, Li, and Mn ions. The results obtained show that the potential of Li metal deposition, after the addition of MgCl₂ and MnCl₂, is more positive than the one of Li metal deposition before the addition. The codeposition of Mg, Li, and Mn occurs at current densities lower than −1.43 A cm⁻² in LiCl–KCl–MgCl₂ (8 wt%) melts containing 2 wt% MnCl₂. The onset potential for the codeposition of Mg, Li, and Mn is −2.100 V. α, α + β, and β phases Mg–Li–Mn alloys with different lithium and manganese contents were obtained via galvanostatic electrolysis from LiCl–KCl melts with different concentrations of MgCl₂ and MnCl₂. The microstructures of typical α and β phases of Mg–Li–Mn alloys were characterized by X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) and EPMA area analysis showed that the elements of Mg and Mn distribute homogeneously in the Mg–Li–Mn alloys. The results of inductively coupled plasma analysis determined that the chemical compositions of Mg–Li–Mn alloys correspond with the phase structures of XRD patterns, and lithium and manganese contents of Mg–Li–Mn alloys depend on the concentrations of MgCl₂ and MnCl₂.     

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.     

Improvement of thermal stability of ZrO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> aerogels by an inorganic–organic synergetic surface modification

The thermal stability of ZrO₂–SiO₂ aerogels was significantly improved by inorganic–organic synergetic surface modifications: inorganic ions [Fe(III)] surface modification and hexamethyldisilazane gas phase modification. The replacement of Hs from surface hydroxyl groups on the aerogel by Fe(III) ions and silyl groups played a critical role in isolating the hydrous particles of ZrO₂–SiO₂ aerogels. So the particle growth caused by the condensation of hydroxyl groups upon firing was inhibited. Meanwhile, the decomposition of the silyl groups upon heat treatment produced SiO₂ particles, which could serve as pining particle to inhibit the crystallization of ZrO₂. Hence, the porous microstructure of the modified aerogels was still well preserved up to 1000 °C, with a high specific surface area of 203.5 m²/g, and a considerable pore volume of 0.721 cc/g. These characteristics of the modified aerogels suggest that it has great potential on ultrahigh-temperature applications in the fields of thermal insulation, catalysis, and catalyst support, etc.     

Crystallization Behavior of Lithium–Iron-Phosphate Glasses with Additions of ZrO<Subscript>2</Subscript>

Lithium–iron-phosphate (LIP) glasses with different amounts of zirconia were prepared by conventional melting and annealing process. The influence of the nucleation agent, zirconia, on the crystallization behavior of LIP glasses has been studied using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electronic microscopy (SEM) techniques. The results show that addition of 2 wt% of zirconia results in increases in the glass transition and crystallization temperatures and a decrease in the activation energy of crystallization. However, both temperatures decrease with increased addition of zirconia while the activation energy increases. The zirconia-free LIP glass only shows surface crystallization with crystals of LiFeP₂O₇. The glass containing 2 wt% of zirconia also has surface crystallization; however, mixed ZrP₂O₇ and LiFeP₂O₇ are crystallized. The addition of 5 and 8 wt% of zirconia leads to bulk crystallization and increasing formation of ZrP₂O₇ crystals besides the LiFeP₂O₇ phase.     

Characteristics of a tungsten film electrodeposited in a KF–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–WO<Subscript>3</Subscript> melt and preparation of W–Cu–W three-layered films for heat sink application

A tungsten film of 13 μm in thickness was obtained on a copper substrate by galvanostatic electrolysis at 30 mA cm⁻² for 40 min in a KF–B₂O₃–WO₃ (67:26:7 mol%) melt at 850 °C. By cross-sectional scanning electron microscopy observation and energy dispersive X-ray analysis, the tungsten layer was found to be compact and free from cracks, voids and melt inclusion. The X-ray diffractometry analysis revealed that the phase was α-tungsten, and that (222) plane was significantly oriented parallel to the substrate. By nanoindentation, its hardness was found to be 8.4 GPa, which was larger than that of single crystal tungsten. Its Young’s modulus was measured to be 410 GPa, which was similar with the reported value of single crystal tungsten. Its coefficient of linear thermal expansion and thermal conductivity were 4.5 × 10⁻⁶ K⁻¹ and 178 W m⁻¹ K⁻¹, respectively, which were similar values for the tungsten produced by a conventional powder metallurgy method. Finally, W–Cu–W three-layered films were prepared for a heat sink application. It was confirmed that a three-layered film having a desired coefficient of linear thermal expansion can be prepared easily by this new molten salt method.     

Physical–chemical properties and conductivity of Na<Subscript>2</Subscript>O–SnO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> glass systems

The effect of tin(IV) oxide on the conductivity and chemical stability of sodium–silicate glass has been studied for five different glass compositions. Dilatometry and DSC were used to investigate the thermal behavior of the glass. The research into transport characteristics of the glass has shown that its conductivity is in the range of 2 × 10^–8–5 × 10^–7 S/cm at 25°C and 10^–3 S/cm at 300°C.     

Kinetics of Hydrolytic Polycondensation of Silicon Dioxide in the SrO–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> Systems

The kinetics of polycondensation in solutions during the liquid-phase synthesis of ceramic material precursors based on a SrO–B₂O₃–SiO₂ system are studied by spectrophotometry. The ratio between the quantitative content of tetraethoxysilane and the reaction rate of the formation of polymer forms is proved.     

Crystallization of CaO–MgO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass prepared by float process

CaO–MgO–Al₂O₃–SiO₂ (CMAS) glass was prepared by float process. The effects of TiO₂ and heat-treatment on properties and crystallization behaviors of float glasses were investigated by atomic force microscope, differential scanning calorimeter, X-ray diffraction, electron probe microanalyzer, field emission scanning electron microscope and viscosity test. The results showed that CMAS parent glasses produced by float process had a high surface flatness (Ra is less than 80.1 ± 0.1 nm) and low tin penetration (14 μm). When the concentration of TiO₂ increased from 3.51 to 5.01 wt %, the glass transition temperature was decreased, and the crystallization temperature was shifted from 913 to 887°C using differential scanning calorimeter. Field emission scanning electron microscope images showed that phase separation was discovered in CMAS parent glass (containing 3.51 wt % TiO₂) treated at 670°C. Diopside as a major crystalline phase was precipitated in CMAS glass-ceramics nucleated at 700°C for 30 min and followed by crystallization at 910°C for 30 min.     

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.     

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.     

Effects of Neutron Irradiation on the Current–Voltage Characteristics of SiO<Subscript>2</Subscript> Nanoparticles

Current–voltage characteristics of SiO₂ nanoparticles have been studied before and after neutron irradiation within 5 V steps in the voltage range of ??100 V to +?100 V at room temperature (RT). The angle of the current–voltage curve is changed appropriately for neutron irradiation periods. Simultaneously, it is seen that the amount of the current flowing through the environment increases proportionally to the irradiation period. Moreover, the mechanism of electrical conductivity appropriate to the obtained results is given in this work.     

Dielectric and electrical characterization of (PEO–PMMA)–LiBF<Subscript>4</Subscript>–EC plasticized solid polymer electrolyte films

Plasticized solid polymer electrolytes (PSPEs) consisting of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50/50 wt%) based matrix with lithium tetrafluoroborate (LiBF₄) as dopant ionic salt (10 wt%) and varied concentrations (x = 0, 5, 10 and 15 wt%) of ethylene carbonate (EC) as plasticizer have been prepared. Classical solution-cast (SC) and the ultrasonic assisted followed by microwave irradiated (US–MW) solution-cast methods have been used for the preparation of (PEO–PMMA)–LiBF₄–x wt% EC films, and the same have been hot–pressed to get their smooth surfaces. Dielectric relaxation spectroscopy (DRS) and X–ray diffraction (XRD) techniques have been employed to characterize the dielectric and electrical dispersions and the structural properties of the PSPE films, respectively. It has been observed that the ionic conductivity of these semicrystalline ion-dipolar complexes is governed by their dielectric permittivity and polymers chain segmental dynamics. The increase in ionic conductivity values with the increase of plasticizer concentration in the PSPEs also varies with the films’ preparation methods. The US–MW method prepared PSPE film containing 15 wt% EC has a maximum ionic conductivity (1.86 × 10^?5 S cm^?1) at room temperature, whereas, the films having low concentrations of EC exhibit the conductivity of the order of 10^?6 S cm^?1.     

Effect of the Nature of the Binder on the Formation Temperature of Glass-Ceramic Coatings Based on Si–B–ZrB<Subscript>2</Subscript> for Graphite Protection

This work is devoted to fabricating and studying the properties of coatings based on the Si–B–ZrB₂ systems used in graphite protection. The kinetics of the oxidation of graphite with coatings at different temperatures in air are investigated. The optimal conditions for the thermal treatment of the material with the coating are suggested.     

Photocrosslinking of styrene–isoprene–styrene; effect of benzoin and ethylene glycol dimethacrylate on physical properties

Crosslinking reaction of polymer by ultraviolet (UV) irradiation has been important in industries. In this work, photocrosslinking of styrene–isoprene–styrene (SIS) triblock copolymer in the presence of benzoin photoinitiator and a dimethacrylate monomer as crosslinking agent was investigated. Curing of samples was initiated under UV irradiation. Benzoin was used as photoinitiator because it contains chromophore group that could absorb UV irradiation. Ethylene glycol dimethacrylate (EGDMA) was used as crosslinking agent, since it has alkene functional groups that could react with the alkene group of SIS. ATR-FTIR spectra of samples show that absorption band of double bond at 1500–1600?cm^?1 decreases after UV exposure. Increasing the concentration of benzoin (0.1–1?phr) and EGDMA (1–10?phr) leads to an increase in gel content and hardness, while swelling ratio decreases. After 5?min heating at 150?°C, about 20%wt of the unirradiated compound became insoluble, because heating of compound at 150?°C causes crosslinking reaction without any irradiation.     

Effect of the thermal treatment on the phase composition of the surface of coatings based on Si–B–ZrB<Subscript>2</Subscript> and modified with ZrO<Subscript>2</Subscript> fibers

Coatings on graphite that are stable to oxidation and based on the silicon–boron–zirconium boride composite containing from 5 to 50% of fibrous zirconium dioxide as a modifying dopant have been produced by the suspension–annealing method. A nonporous layer is formed at the zirconium dioxide content ranging from 5 to 15%, while a porous layer is formed at its 50% content. A glass-forming melt, as well as zirconium dioxide and silicate, is formed during thermal treatment as a result of the chemical reactions with the oxygen in air. The zirconium silicate content increases, along with the modifier’s concentration and temperature.     

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.