The role of Ce ions in electrochemical corrosion of 304 SS in Ce(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>.6H<Subscript>2</Subscript>O

Effects of temperature and potential on the electrochemical corrosion behavior of alloy AISI 304 (UNS S30400) Stainless steel were investigated in 3 wt.% cerium nitrate (Ce[NO₃]₃.6H₂O) solution. With an increase in electrolyte temperature from ambient temperature to 90°C, the corrosion potential of the alloy shifted towards the noble direction, and the resistance to polarization increased due to the formation of Ce-oxide on the electrode surface. The oxide films formed at the open circuit potential (OCP) and a passive potential of 0.4 V_SCE were examined by x-ray photoelectron spectroscopy (XPS). The oxide film formed at 50°C and a passive potentialof 0.4 V_SCE consists of mixed oxides of Ce and Cr, whereas that at OCP consists of only Cr oxide. The formation of Cr oxides on the electrode surface was primarily due to the nitrate (NO₃ ⁻) ions in Ce(NO₃)₃.6H₂O electrolyte.     

Investigation on the Phase Diagram of LiCl-KCl-NdCl<Subscript>3</Subscript> Pseudo-Ternary System

The ternary phase diagram of LiCl-KCl-NdCl₃ system has been investigated by differential thermal analysis (DTA), followed by characterization of the coexisting phases in the solid state by x-ray diffraction, in order to understand the interactions in the NdCl₃-LiCl-KCl ternary system. The results of these experiments showed that LiCl and K₂NdCl₅ form a non binary join section. This divides the LiCl-KCl-NdCl₃ system into two quasi-ternary sections, namely (1) LiCl-KCl-K₂NdCl₅ and (2) LiCl-K₂NdCl₅-NdCl₃ systems. Both are simple eutectic ternary phase diagrams. The ternary eutectic temperatures and eutectic compositions are determined to be 316?±?3 °C and 53.9 mol.% LiCl-38.7 mol.% KCl-7.4 mol.% K₂NdCl₅ in the LiCl-KCl-K₂NdCl₅ quasi-ternary section, while the other eutectic temperature and composition are determined to be 376?±?9 °C and 46.2 mol.% LiCl-32.5 mol.% K₂NdCl₅-21.3 mol.% NdCl₃ in the LiCl-K₂NdCl₅-NdCl₃ quasi-ternary section. A quasi-ternary peritectic reaction is observed at 37.7 mol.% LiCl-36.2 mol.% KCl-26.1 mol.% K₂NdCl₅ at 445?±?1°C. The primary and secondary crystallization temperatures for the samples are deduced from the heating runs of DTA traces, and the phases responsible for the various thermal events are ascertained. Isothermal sections at chosen temperatures and polythermal liquidus projection with isothermal contours are drawn over the ternary phase field.     

Phase Equilibria in the System FeO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

Liquidus data are presented for mixtures in the ternary system FeO-Fe₂O₃-SiO₂ in equilibrium with a gas phase with O₂ pressures ranging from 10^?10.9 to 1 atm. Data obtained are combined with previously published data to construct lines of equal O₂ pressures and lines of equal CO₂/H₂ mixing ratios along the liquidus surface. Courses of crystallization of selected mixtures under conditions of constant total composition, constant O₂ pressures, and constant CO₂/H₂ mixing ratios are discussed.     

Phase Formation of the Yttrium Aluminates in the Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiC System

Phase formation sequence of the yttrium aluminates in the Y₂O₃-Al₂O₃-SiC ternary system as temperature increases were investigated via x-ray diffraction (XRD). Results showed that YAM (monoclinic), YAP (perovskite) and YAG (garnet) were the yttrium aluminates presented in the solid-state reacted samples at a fixed Al₂O₃:SiC ratio of 1:1. Formation of the yttrium aluminates depended on the temperature. The YAM, YAP and YAG started to form below 1150 °C, at 1300 °C, and at 1450 °C, respectively. Accordingly, two behavior phase diagrams of the Y₂O₃-Al₂O₃-SiC ternary system were recognized, one is in the temperature range of 1150-1300 °C and the other is in 1300-1450 °C, respectively. Thereafter, the phase equilibrium was reached in the temperature range of 1450-1700 °C. Effects of SiC on the phase formation processes in the ternary system were discussed.     

A Revision of the Al-rich Region of the Sm-Al Phase Diagram: The Sm<Subscript>3</Subscript>Al<Subscript>11</Subscript> Phase

Phase equilibria in the Al-rich region of the Sm-Al binary system has been revised and updated: it has been confirmed that Sm₃Al₁₁ is a congruently melting phase which, on cooling, undergoes catatectic decomposition Sm₃Al₁₁ ↔ liquid + SmAl₃.     

Phase Diagram and Thermodynamic and Transport Properties of the DyBr<Subscript>3</Subscript>-LiBr Binary System

The phase diagram of the DyBr₃-LiBr binary system was derived from DSC measurements. It exhibits two eutectics and has two stoichiometric compounds. The first compound, Li₃DyBr₆, melts congruently at 803 K. The second one, Li₆DyBr₉ decomposes in the solid state at 656 K. The composition of the two eutectic mixtures, x(DyBr₃) = 0.156 and 0.321, respectively, was determined by the Tamman method. The respective eutectic temperatures are 787 and 791 K. The electrical conductivity of Li₃DyBr₆ compound was measured in the liquid and solid phase. It was found to be a solid electrolyte with a high electrical conductivity at around room temperature. Some additional electrical conductivity measurements performed on solid samples confirmed the existence of Li₆DyBr₉.     

Experimental determination of NH<Subscript>4</Subscript>NO<Subscript>3</Subscript>-KNO<Subscript>3</Subscript> binary phase diagram

The solid-state phase transitions in ammonium nitrate (AN)-potassium nitrate (KN) system, and the equilibrium AN-KN phase diagram have been determined by using differential scanning calorimetry and high-temperature in situ x-ray diffractometry. Sample preparation was performed in a special “dry room” with very low humidity. A single phase region (AN III) with no phase transitions to 373 K was observed in the composition range 5 to 20% KN; this is critical for use in air bag gas generators. The high-temperature KN phase (KN I) has a wide range of stability from 20 to 100 wt.% KN. There are one eutectic, two eutectoid, three peritectoid, and one congruent transformations in this phase diagram. Two new nonstoichiometric phases were found at lower temperatures in the mid-composition range between the AN and KN terminal solid solutions. Details of the phase equilibria are presented.     

Phase Relations in the ZrO<Subscript>2</Subscript>-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> System: Experimental Study and Advanced Thermodynamic Modeling

Phase equilibria in the ZrO₂-Nd₂O₃-Y₂O₃ system at 1523-1873 K have been investigated by x-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive x-ray spectroscopy (SEM/EDX). Temperatures of phase transformations were determined by differential thermal analysis. Temperatures of invariant reactions in the ZrO₂-Nd₂O₃ system F = A + Pyr and H = F + A were determined as 1763 and 2118 K respectively and thermodynamic parameters of phases were re-assessed. Phase transformations in ternary systems were determined at 1732 K for composition ZrO₂-48.46Nd₂O₃-5.38Y₂O₃ (mol%) and at 1744 and 1881 K for composition ZrO₂-79.09Nd₂O₃-2.75Y₂O₃ (mol%). They were interpreted using XRD investigation before and after DTA as Pyr + B → F, Pyr → F and A → B, respectively. The solubility of the Y₂O₃ in pyrochlore phase was found to exceed 10 mol%. The thermodynamic parameters of the ZrO₂-Nd₂O₃-Y₂O₃ system were reassessed taking into account solubility of Y₂O₃ in the Nd₂Zr₂O₇ pyrochlore phase (Pyr). It is assumed that Y³⁺ substitutes Nd³⁺ and Zr⁴⁺ in their preferentially occupied sublattices. Ternary parameter was introduced into fluorite phase (F) for better reproducing of phase equilibria. Mixing parameters were reassessed for phase A (Nd₂O₃ based solution), monoclinic phase B and cubic phase C (Y₂O₃ based solution). The isothermal sections calculated for the ZrO₂-Nd₂O₃-Y₂O₃ system are in the reasonable agreement with experimental results.     

Solid Solution and Phase Relations in SiC-AlN-Pr<Subscript>2</Subscript>O<Subscript>3</Subscript> System

The phase relations in the Si-Al-Pr-O-N-C systems, involving SiC-AlN-Pr₂O₃, AlN-Pr₂O₃-Al₂O₃ and SiC-AlN-Pr₂O₃-Al₂O₃ systems were determined by XRD phase analyses of the solid-state reacted samples from powder mixtures of SiC, AlN, Pr₂O₃, as well as Al₂O₃. Pr₂Al(Si)O₃N(C) solid-solution (1:1 ss) between SiC and Pr₂AlO₃N (1:1 compound) was discovered with the limited solubility of 0.6 SiC at 1650 °C. Subsolidus phase diagram of SiC-AlN-Pr₂O₃ system was presented, SiC was compatible with AlN, Pr₂O₃ and 1:1 ss, respectively. Two-aluminates PrAlO₃ (PrAP) and PrAl₁₁O₁₈ [β(Pr), β-Al₂O₃ type] were formed when Al₂O₃ impurity was introduced in AlN powder. They establish the equilibrium relationships respectively with SiC, AlN, Pr₂O₃ and Pr₂AlO₃N. Accordingly, the phase relations in the AlN-Pr₂O₃-Al₂O₃ ternary system and SiC-AlN-Pr₂O₃-Al₂O₃ quaternary system containing four quaternary phases compatible tetrahedrons were presented.     

Microstructure and microwave dielectric properties of ZnO-B2O3 added （Ca0.254Li0.19Sm0.14）TiO3 ceramics

The effects of ZnO-B2O3 (ZB2) on the sintering behavior and microwave dielectric properties of (Ca0.254Li0.19Sm0.14)TiO3 ceramics were investigated.The densities of the specimens reached the maximum value by adding 3 wt.% ZB2 and then decreased.The sintering temperature of the specimens was lowered from 1300 to 1100°C without degradation of the microwave dielectric properties.The (Ca0.254Li0.19Sm0.14)TiO3 + 3 wt.% ZB2 sintered at 1100°C for 3 h showed good microwave dielectric properties,εr = 108.2,Qf = 6545 GHz,and τf = 6.5 ppm/°C,respectively,indicating that ZB2 was an effective sintering aid to improve the densification and microwave dielectric properties of (Ca0.254Li0.19Sm0.14)TiO3 ceramics.     

Phase equilibria in the BaS-Ln<Subscript>2</Subscript>S<Subscript>3</Subscript> systems

A survey of available data for the BaS₂-Ln₂S₃ systems shows that the very light lanthanon systems form no intermediate phases but have extensive terminal solid solubilities of BaS in γ-Ln₂S₃ extending to near 50 mol.% BaS. For Ln=Nd and for all heavier lanthanons (smaller ionic radii, r _Ln ³⁺ ), an intermediate phase with stoichiometry of BaLn₂S₄ is formed. BaLn₂S₄ decomposes peritectoidally for Ln=Nd but melts congruently for Ln=Sm and for all heavier lanthanons. A second intermediate phase of stoichiometry, Ba₃Ln₂S₆, forms for Ln=Tb and for all heavier lanthanons (smaller ionic radii). For Ln=Lu, a third phase is formed at BaLu₈S₁₃. In all cases, Ba₃Ln₂S₆ melts peritectically, but BaLu₈S₁₃ melts congruently. The present article discusses: (1) three different techniques for synthesizing the intermediate phases; (2) the systems for Ln=Pr, Tb, and Y; and (3) a computer model for interpolating through the available data for the phase relationships in the nine systems that have been investigated to predict the phase diagrams for the seven systems for which there are limited or no data.     

Up-Date of a Thermodynamic Database of the ZrO<Subscript>2</Subscript>-Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> System for TBC Applications

The thermodynamic database of the ZrO₂-Gd₂O₃-Y₂O₃-Al₂O₃ system is up-dated taking into account new data on lattice stabilities of ZrO₂, Gd₂O₃ and Y₂O₃ and heat capacity measurements for the monoclinic phase Gd₄Al₂O₉ and phase with garnet structure Gd₃Al₅O₁₂. New data for the heat capacities of Gd₂Zr₂O₇ (pyrochlore) and GdAlO₃ (perovskite) as well as on the enthalpy of formation of fluorite solid solutions (Zr_1−x Gd _x )O_2−x/2 were found to be in good agreement with calculated results. In comparison with the previous assessment, taking into account new experimental data resulted in a change of the melting character of the Gd₄Al₂O₉ phase from a peritectic one to a congruent one in the Gd₂O₃-Al₂O₃ system. Correspondently, in the ternary system ZrO₂-Gd₂O₃-Al₂O₃, the melting character of the three-phase assemblage Gd₂O₃ (B), Gd₄Al₂O₉ and GdAlO₃ changed from eutectic to transition type U. The T ₀-lines for T/M and F/T diffusionless transformations and driving force of partitioning to equilibrium assemblage T + F were calculated in the ZrO₂-Gd₂O₃-Y₂O₃ system.     

Phase Equilibria in the System Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-CoO and Gibbs Energy of Formation of Ca<Subscript>3</Subscript>CoAl<Subscript>4</Subscript>O<Subscript>10</Subscript>

An isothermal section of the system Al₂O₃-CaO-CoO at 1500 K has been established by equilibrating 22 samples of different compositions at high temperature and phase identification by optical and scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy after quenching to room temperature. Only one quaternary oxide, Ca₃CoAl₄O₁₀, was identified inside the ternary triangle. Based on the phase relations, a solid-state electrochemical cell was designed to measure the Gibbs energy of formation of Ca₃CoAl₄O₁₀ in the temperature range from 1150 to 1500 K. Calcia-stabilized zirconia was used as the solid electrolyte and a mixture of Co + CoO as the reference electrode. The cell can be represented as: From the emf of the cell, the standard Gibbs energy change for the Ca₃CoAl₄O₁₀ formation reaction, CoO + 3/5CaAl₂O₄ + 1/5Ca₁₂Al₁₄O₃₃ → Ca₃CoAl₄O₁₀, is obtained as a function of temperature: /J mol⁻¹ (±50) = −2673 + 0.289 (T/K). The standard Gibbs energy of formation of Ca₃CoAl₄O₁₀ from its component binary oxides, Al₂O₃, CaO, and CoO is derived as a function of temperature. The standard entropy and enthalpy of formation of Ca₃CoAl₄O₁₀ at 298.15 K are evaluated. Chemical potential diagrams for the system Al₂O₃-CaO-CoO at 1500 K are presented based on the results of this study and auxiliary information from the literature.     

Phase Relations in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript> System in the Solid State. The Crystal Structure of AlVO<Subscript>4</Subscript>

Phase relations in the ternary oxide system Al₂O₃-V₂O₅-MoO₃ in the solid state in air have been investigated by using the x-ray diffraction (XRD) and differential thermal analysis/thermogravimetric (DTA/TG) methods. It was confirmed that in the subsolidus area of the Al₂O₃-V₂O₅-MoO₃ system, there exist seven phases, that is Al₂O₃, V₂O_5(s.s.), MoO₃, AlVO₄, Al₂(MoO₄)₃, AlVMoO₇, and V₉Mo₆O₄₀. Seven fields, in which particular phases coexist at equilibrium, were isolated. The crystal structure of AlVO₄ has been refined from x-ray powder diffraction data. Its space group is triclinic, , Z = 6, with a = 0.65323(1) nm, b = 0.77498(2) nm, c = 0.91233(3) nm, α = 96.175(2)°, β = 107.234(3)°, γ = 101.404(3)°, V = 0.42555 nm³. The crystal structure of the compound is isotypic with FeVO₄. Infrared (IR) spectra of AlVO₄ and FeVO₄ are compared.     

Phase Equilibria in the Tl<Subscript>2</Subscript>Te-Tl<Subscript>5</Subscript>Te<Subscript>3</Subscript>-Tl<Subscript>9</Subscript>TmTe<Subscript>6</Subscript> Section of the Tl-Tm-Te System

Phase equilibria in the Tl₂Te-Tl₅Te₃-Tl₉TmTe₆ section of the Tl-Tm-Te ternary system were experimentally studied by using the powder x-ray diffraction technique, differential thermal analysis, as well as microhardness measurements applied to equilibrated alloys. Several isopleth sections and isothermal section at 680 K, as well as projections of the liquidus and solidus surfaces, were constructed. The Tl₅Te₃-Tl₉TmTe₆ section is characterized by the formation of continuous series of solid solutions (δ-phase) with Tl₅Te₃ tetragonal structure, which penetrate deep into the concentration triangle and occupy more than 90% of its area. A narrow area of solid solutions (α-phase) based on Tl₂Te was detected.     

Plasma-electrolytic oxidation of titanium in Zr(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>-containing electrolyte

It is shown that anodic oxide coatings with a thickness of several to 300 νm can be obtained on titanium by varying the charge spent on (Q). The prevailing phase in the coatings is ZrO₂ in monoclinic and tetragonal modifications. The content of zirconium in the layers is up to 20 at %. Distributions of titanium, zirconium, and oxygen in the cross sections of the coatings are obtained, and the effect of Q on the formation and elementary and phase compositions of the coatings is studied. Tentative experiments clarifying the effects of bipolar anodic-cathodic polarization and electrolyte aging on the composition of coatings are carried out. The coatings are shown to be stable at temperature variations in the range of 20–700°C and to decrease the contact corrosion current at the (titanium + coating)—St3 steel interface by a digit of 10–15 in 3% NaCl.     

Influence of CaF2 on the structure and dielectric properties of Ag（Nb0.8Ta0.2）O3 ceramics

Ag(Nb0.8Ta0.2)O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and di-electric properties of Ag(Nb0.8Ta0.2)O3 ceramics was investigated. The addition of CaF2 led the ceramics to a larger grain size and distortion of lattice. With the addition of 4.5 wt.% CaF2, the permittivity of the ceramics increased from 442 to 1028, the dielectric loss decreased sharply from 6.12 × 10-3 to 8.6 × 10-4, and the temperature coefficient of capacitance decreased from 1834 ppm/°C to-50 ppm/°C (at 1 MHz). These results indicated that the high permittivity was related with a large grain size, a low grain boundary density, and the weak Ta-O or Nb-O bond strength caused by the addition of CaF2.     

Sol-gel preparation and characterization of Li1.3Al0.3Ti1.7（PO4）3 sintered with flux of LiBO2

Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ were prepared by sol-gel method. The structural identification, surface morphology, ionic conductivity, and activation energy of the pellets were studied by X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. The results show that all the Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ have similar X-ray diffraction patterns. The sintered pellet becomes denser and the boundary and corner of the particles become illegible with the increase of LiBO₂. Among the Li_1.3Al_0.3Ti_1.7(PO₃)₄ pellets sintered with different mole fractions of LiBO₂, the one sintered with 1 mol% LiBO₂ shows the highest ionic conductivity of 3.95×10⁻⁴ S.cm⁻¹ and the lowest activation energy of 0.2469 eV.