Equilibrium Diagram Research Articles

Cyanide-free environment-friendly alternative to copper electroplating for zinc die-cast alloys.

In this paper, a cyanide-free electroplating bath containing glutamate as a complexing agent is investigated as an environment-friendly alternative for copper plating on zinc die-cast alloys. Glutamate reacts with copper in an aqueous solution that exhibits similar copper cyanide properties by forming complexes. The electroplating bath pH is chosen from equilibrium diagrams to avoid the formation of insoluble complexes and oxides at varying copper-to-glutamate molar ratio. The plating bath's electrochemical response on a stationary electrode confirms that a 1:3 molar ratio between copper and glutamate at pH 8 exhibits better copper deposition onto the substrate, with its morphology characterized using SEM. The results suggest that the copper glutamate electroplating bath can be suitable for copper cyanide bath replacement without additives, allowing a one-step electroplating process. Moreover, the polarization and electrochemical impedance measurements suggest inhibition of the substrate's corrosion when copper was electroplated at a 1:3 copper-to-glutamate molar ratio. With the careful control of the concentration ratio, the process can provide adequate copper deposition and anti-corrosion capability suitable for green nanocoating applications.

Role of assisting reagents on the synthesis of α-Fe2O3 by microwave-assisted hydrothermal reaction

Currently, the controlled synthesis of well-defined metal oxide nanoparticles has received intense scientific attention to modulate the properties of materials through the size and shape. This paper focuses on providing a better understanding about the growth, morphology, size, and crystal structure of α-Fe2O3 nanoparticles synthesized by a microwave-assisted hydrothermal route, considering a detailed analysis of the influence of the reaction temperature, time, and ratio of assisting reagents (sodium citrate and urea) as well as the effects of calcination temperature. According to X-Ray Diffraction analysis, the α-Fe2O3 crystalline phase was directly prepared at 200 °C for 60 min using only urea, while materials with low crystallinity were obtained using only sodium citrate as well as sodium citrate:urea (in both ratio 1:1 and 2:2.5). Upon calcination at 600 °C, the crystallization of α-Fe2O3 started in the material prepared with a sodium citrate:urea ratio of 2:2.5. Scanning and Transmission Electron Microscopies results revealed that the materials synthesized using urea, sodium citrate, and sodium citrate:urea ratio of 1:1 are formed by nanoparticles less than 100 nm without a defined morphology, whereas the materials prepared using sodium citrate:urea ratio of 2:2.5 showed well-defined nanospheres with average sizes between 150 and 250 nm constituted by self-assembled crystals smaller than 10 nm. The shape and size of the nanospheres did not undergo significant changes even at high thermal treatments, such as 800 °C. Based on equilibrium diagrams, the role of each chemical agent was disclosed, indicating that the modulated precipitation through soluble complexes is a very important factor in controlling the hierarchical organization of the particles to form the nanospheres. This study demonstrates the versatility of sodium citrate and urea as assisting reagents to prepare a variety of α-Fe2O3 nanoparticles. Besides, these results could be useful in extending new ideas for the synthesis of other nanomaterials.

Chemical stability diagrams as a powerful tool to the synthesis of Cu2SnS3 thin films by chemical bath deposition

Cu2SnS3 films are produced by chemical bath method employing low toxicity citrate precursor taking advantage of the strong complexes formed with Cu(II) and Sn(II). The deposition conditions for Cu2SnS3 thin films were obtained through a thermodynamic analysis of the effect of tin concentration on Cu(II)–Sn(II)-Citrate complexes and Cu(II)–Sn(II)-Citrate-Thiourea system using a species distribution and potential–pH (Eh-pH) analysis. Theoretical analysis of the speciation fraction of Cu(II) and Sn(II) shown that the predominant species at pH equal to 4.5 at 90 °C are [Cu2(Cit)2OH]3− and [Sn2(Cit)2]2−. For the Cu(II)–Sn(II)-Citrate-Thiourea system at 90 °C, the Eh-pH diagrams established that binary precursors, Cu2S and SnS2, would be obtained under basic pH conditions. Subsequently, Cu2SnS3 films were synthetized at 90 °C at pH equal to 8 by keeping fixed the molar relationships complexing agent-metal and sulfur-metal. The redox potentials were measured in solution and chemical equilibrium diagrams were constructed, confirming the existence of binary precursors under reductive conditions. Characterization of structural, electronic and transport properties indicated that Cu2SnS3 fabricated by chemical bath deposition have monoclinic crystal structure, a direct band gap energy of 1.70 eV and p-type conductivity.

Weldability Evaluation of Alloy 718 Investment Castings with Different Si Contents and Thermal Stories and Hot Cracking Mechanism in Their Laser Beam Welds

In this work, weldability and hot cracking susceptibility of five alloy 718 investment castings in laser beam welding (LBW) were investigated. Influence of chemical composition, with varying Si contents from 0.05 to 0.17 wt %, solidification rate, and pre-weld heat treatment were studied by carrying out three different weldability tests, i.e., hot ductility, Varestraint, and bead-on-plate tests, after hot isostatic pressing (HIP) and solution annealing treatment. Onset of hot ductility drop was directly related to the presence of residual Laves phase, whereas the hot ductility recovery behaviour was connected to the Si content and γ grain size. LBW Varestraint tests gave rise to enhanced fusion zone (FZ) cracking with much more reduced heat-affected zone (HAZ) cracking that was mostly independent of Si content and residual Laves phase. Microstructural characterisation of bead-on-plate welding samples showed that HAZ cracking susceptibility was closely related to welding morphology. Multiple HAZ cracks were detected in nail or mushroom welding shapes, typical in keyhole mode LBW, irrespective of the chemical composition and thermal story of castings. In all LBW welds, Laves phase with a composition similar to the eutectic of the pseudo-binary equilibrium diagram of alloy 718 was formed in the FZ. The composition of this regenerated Laves phase matched with the continuous Laves phase film observed along HAZ cracks. This was strong evidence of backfilling mechanism, which is described as wetting and infiltration of terminal liquid along γ grain boundaries of parent material. The current results suggest that this cracking mechanism was activated in three-point intersections resulting from perpendicular crossing of columnar grain boundaries with fusion line and was enhanced by nail or mushroom weld shapes and narrow and columnar γ grain characteristics of castings. Neither Varestraint nor hot ductility weldability tests can reproduce this particular cracking mechanism.

Extraction of Free Fatty Acid Mixtures from Rice Bran Oil by Aqueous Renewable Alcohols: Liquid-liquid Equilibrium Diagram and Number of Equilibrium Stages

This work is aimed to measure the liquid-liquid equilibria of rice bran oil-fatty acid-aqueous alcohols using fatty acid mixtures derived from rice bran oil as solutes and to calculate the number of equilibrium stages required for the extraction process. Renewable alcohols, ethanol and isopropanol in aqueous form were used as solvents. The liquid-liquid equilibrium data were measured at 25 °C and presented as ternary diagrams. It was found that ethanol gave a lower distribution coefficient than isopropanol. For the same solvent, increasing the water content resulted in a lower distribution coefficient. For the free fatty acid contents of 30% in the feed and of 10% to 2.5% in the raffinate, the minimum solvent-to-feed ratio was found to be in the range of 1 to 5. Using solvent-to-feed ratios from 2 to 4, the number of extraction stages required was in the range of 1 to 8. Based on the minimum solvent-to-feed ratio and number of equilibrium stages, isopropanol was found to be better than ethanol.

The versatility of petrological modeling: Thermobarometry of high‐pressure metabasites from the Renge and Sanbagawa belts and phase evolution during warm subduction at Nankai

AbstractPetrological modeling is a powerful technique to address different types of geological problems via phase‐equilibria predictions at different pressure–temperature‐composition conditions. Here, we show the versatility of this technique by (1) performing thermobarometrical calculations using phase equilibrium diagrams to explore the petrological evolution of high‐pressure (HP) metabasites from the Renge and Sanbagawa belts, Japan and (2) forward‐modeling the mineral–melt evolution of the subducted fresh and altered oceanic crust along the Nankai subduction zone geotherm at the Kii peninsula, Japan. In the first case, we selected three representative samples from these metamorphic belts: a glaucophane eclogite and a garnet glaucophane schist from the Renge belt (Omi area) and a quartz eclogite from the Sanbagawa belt (Besshi area). We calculated the peak metamorphic conditions at ~2.0–2.3 GPa and ~550–630 °C for the HP metabasites from the Renge belt, whereas for the quartz eclogite, the peak equilibrium conditions were calculated at 2.5–2.8 GPa and ~640–750 °C. According to our models, the quartz eclogite experienced partial melting after peak metamorphism. In terms of the petrological evolution of the subducted uppermost portion of the oceanic crust along the warm Nankai geotherm, our models show that fluid release occurs at ~20–60 km, likely promoting high pore‐fluid pressure, and thus, seismicity at these depths; dehydration is controlled by chlorite breakdown. Our petrological models predict partial melting at >60 km, mainly driven by phengite and amphibole breakdown. According to our models, the melt proportion is relatively small, suggesting that slab anatexis is not an efficient mechanism for generating voluminous magmatism at these conditions. Modeled melt compositions correspond to high‐SiO2 adakites; these are similar to compositions found in the Daisen and Sambe volcanoes, in southwest Japan, suggesting that the modeled melts may serve as an analog to explain adakite petrogenesis.

ON THE STRUCTURE OF EUTECTIC SYSTEMS MELTINGS: THEORETICAL ASPECTS OF MODEL REPRESENTATION OF THE LIQUID STRUCTURE DESCRIPTION

In the offered article theoretical researches of eutectic systems are systematized, connection of results of these researches with model representation of the description of structure of a liquid for the purpose of the further practical realization is allocated. This study is relevant because there is no generalized and systematic information on the study of the structure of melts of eutectic systems. On the one hand, this is due to certain contradictions in some studies. However, the main problem is the ambiguity and inconsistency of interpretation of the results of studies of the structure of melts. The authors note that in solving problems related to the nature of the liquid state, of particular interest is the study of the structure of two-component melts, which form in the solid state phase equilibrium diagrams of the eutectic type. The term eutectic means "most fusible" and is used to describe an isothermal reversible reaction in which a liquid decomposes into two or more solid phases during cooling. It is proposed to make judgments about the structure of metal melts of eutectic systems according to the type of liquidus line of the phase equilibrium diagram. To do this, all eutectic systems are divided into: systems with a smooth liquidus line without an inflection point in either the pre-eutectic or the supereutectic region (NI); systems with an inflection point on one branch of the liquidus line; systems with an inflection point on both branches of the liquidus line; systems with a eutectic point near the zero concentration of one of the components and an inflection point on the liquidus line (0% SI). Based on the generalized and systematized results of theoretical and experimental studies, it is proved that eutectic systems are polygenic systems that have a wide range of interactions between particles and, accordingly, have a short-range structure. This information can make it possible to unambiguously interpret the results of diffraction studies and physicochemical analysis data to create a model representation of the description of the structure of the liquid (melt).

PHASE EQUILIBRIA OF THE PbBi2Te4–"PbSb2Te4" SECTION OF THE PbTe–Bi2Te3–Sb2Te3 SYSTEM AND SOME PROPERTIES OF THE SOLID SOLUTIONS

PbTe–Bi2Te3–Sb2Te3 system has been studied by DTA and X-ray diffraction methods along the PbBi2Te4 – "PbSb2Te4" section. It was found that the compound of the composition PbSb2Te4, specified in the literature does not exist. On the basis of the latter a wide (more than 50 mol%) area of solid solution (γ) was detected. By using obtained experimental results, a fragment of the solid-phase equilibrium diagram of the PbTe–Bi2Te3–Sb2Te3 system was constructed and boundaries of the heterogeneous areas α+γ, α+β, α+β+γ (α- and β- are solid solutions based on PbTe and Sb2Te3, respectively) have been determined

Extension of the Classification of Three-Component Systems Containing Binary Biazeotropic Components and Not Containing Ternary Azeotropes

The separation strategies of mixtures are determined by knowledge of their structures of phase equilibrium diagrams. In this paper, in two independent ways, namely, by constructing K = 1 lines and on the basis of the analysis of the transformations of the phase diagrams when the external conditions change, all thermodynamically possible subtypes of the phase portraits of the trajectories of the open equilibrium evaporation of three-component systems containing binary biazeotropic components and not containing ternary azeotropes are determined. An atlas of structures of vapor–liquid equilibrium diagrams of the indicated systems is created (116 diagrams in total).

Structure and Properties of Fe–Ga Alloys as Promising Materials for Electronics

This review article is devoted to studies of the structure and properties of Fe–Ga alloys that serve as functional materials with high magnetostriction. Particular attention is paid to diffraction methods that allow one both to monitor phase transformations in real time and identify phase structures and microheterogeneities in their structure. Based on the studies published in recent decades, the existing equilibrium diagrams and mechanisms of formation of elastic and anelastic properties, including magnetostriction and internal friction, are critically analyzed.

Investigation of Phase Transformation of Fe65Ni35 Alloy by the Modified Pulse Method.

This paper presents the possibility of using a modified-pulse method (MPM) determining the temperature characteristics of thermal diffusivity in order to identify phase transformations in metals. The experiment and attempt of phase identification were conducted for the Fe65Ni35 alloy in the 20–500 °C temperature range during both sample heating and cooling. The estimated error of discrete thermal diffusivity measurements was less than 3%. The method allows us to narrow down the averaging of the interval of this value, as a function of temperature, in the range below 1 K. Recently published analysis of the phase diagrams of Fe–Ni alloys, and the results of the authors’ own research into the Fe65Ni35 alloy, showed very good correlation between changes occurring when heating the alloy and the equilibrium diagram provided by Cacciamani G., Dinsdale A., Palumbo M., and Pasturel A. (Intermetallics 18, 2010, 1148–1162) showing the position of phases with a crystal-lattice structure based on the face-centered cubic (FCC) cell.

Influence of the Formation Temperature of the Morphology of por-Si Formed by Pd-Assisted Chemical Etching

The process of the Pd-assisted etching of silicon in a solution containing HF and H2O2 is investigated. It is shown that the morphology of the forming layers is affected by such factors as the etching duration and solution temperature. It is shown that Pd nanoparticles remain on the walls and bottom of the pores in the course of Pd-assisted etching. Such a structure, as is shown in earlier works, possesses the electrooxidation property of ethanol, which gives grounds to affirm that the forming structures are Schottky-type structures. A model of Pd-assisted etching is determined with the help of the electrochemical equilibrium diagram in the Si–HF(aq.) system. It is shown that the polishing dissolution of Si occurs without the formation of intermediate products (SiO2).

Strategies for Scalable Gas-Phase Preparation of Free-Standing Graphene

The preparation of graphene with high quality serves as a prerequisite for its usage. Traditional methods of graphene production, represented by liquid-phase exfoliation and chemical vapor depositi...

Defect chemistry and oxygen non-stoichiometry in SrFe0.2Co0.4Mo0.4O3-δ ceramic oxide for solid oxide fuel cells

SrFe0.2Co0.4Mo0.4O3-δ (SFCM) is a ceramic oxide that has the potential to replace conventional Ni-based cermet anodes and is appropriate for use in solid oxide fuel cells operating at low temperatures (below 650 °C). SFCM was shown to be phase stable with n-type conductivity above 43 S/cm under reducing conditions and reversibly creates secondary phases under oxidizing conditions with p-type conductivity around 4 S/cm at 600 °C. SFCM begins desorbing oxygen and creating vacancies under nitrogen at 350 °C and continues to do so above 800°C. Under oxidizing conditions, SFCM remains near stoichiometric, with oxygen non-stoichiometry changes below δ = 0.003. Once exposed to reducing conditions, SFCM can obtain a non-stoichiometry up to δ = 0.176 due to the reduction of the three multivalent B-site cations resulting in a low enthalpy of formation for oxygen vacancies at 109 kJ mol − 1. This data is used to propose a low pO2 defect equilibrium model and diagram to explain the oxygen vacancy generation behavior under reducing conditions across temperatures.

Areas of energy advantage for flowsheets of separation modes for mixtures containing components with similar volatilities

Objectives. The conditions for the effective application of the sharp distillation technique (without a component distributed between the distillate and bottom flows) for the separation of quaternary zeotropic mixtures containing components with similar volatilities were determined. The area of energy advantage for the flowsheet based on the preliminary fractionation of the mixture, compared with the flowsheet, the first distillation column of which works based on the indirect separation mode, was identified for an ethyl acetate–benzene–toluene–butyl acetate system. Energy savings of up to 20% were achieved. The direct and indirect distillation modes can become competitive when the point of the original composition is located near single K-surfaces or in a region with a different ratio of distribution coefficients. Sharp distillation is not suitable for the separation of a mixture containing a pair of components exhibiting relative unity volatility with medium boiling points.Methods. The mathematical modeling in the Aspen Plus V.10.0 software package was chosen as the research method. The simulation was based on the Wilson local composition equation. The relative errors in the description of the phase equilibrium did not exceed 3%.Results. The structure of the vapor–liquid equilibrium diagram and diagram of surfaces of the unit component distribution coefficients were studied for the ethyl acetate–benzene–toluenebutyl acetate and acetone–toluene–butyl acetate–o-xylene systems. Flowsheets based on the sharp, indirect (both systems), or direct (second system) distillation modes were proposed. The distillation process was simulated, and the parameters of the column work were determined (the quality of the substances meets the State Standard requirements of the Russian Federation for minimal energy consumption).Conclusions. Recommendations regarding the use of sharp distillation for the separation of quaternary mixtures containing components with similar volatilities were devised.

Hercynian subduction‐related processes within the metamorphic continental crust in Calabria (southern Italy)

AbstractLinking the deformation history of mylonitized continental rocks to the progress of devolatilization reactions that trigger reaction softening is critical for the understanding of crustal scale processes. We have analysed the field geometries and microstructures of deformed rocks within the southern Hercynian belt in Calabria, as well as modelled the pressure–temperature–deformation (P–T–d) trajectory of a main ductile shear zone that tectonically coupled the deeper crustal Mammola Paragneiss Unit with the upper crustal Stilo–Pazzano Phyllite Unit. P–T modelling of the mylonitic Mammola Paragneiss Unit was performed through calculation of phase equilibrium diagrams with the software thermocalc in the MnNCKFMASHTO model system. The prograde P–T–d trajectory is based on the zoning profiles of garnet porphyroblasts and their mineral inclusions, primarily barroisite and epidote. P–T modelling shows that peak metamorphic conditions of ~0.9 GPa and 585°C were reached during a Dn‐1 under‐thrusting event. The following exhumation during the Dn mylonitic event, and contact metamorphism during Dn+1 and Dn+2 folding events, have also been modelled because they are essential to restore the previous tectono‐metamorphic history. The exhumation trajectory was modelled down to 0.3 GPa with temperatures of 440–460°C, under fluid‐deficient conditions, as well as the final late Carboniferous contact metamorphism up to Tmax of 680–720°C. The prograde path shows clear evidence for thermal buffering during garnet growth at the expense of chlorite, with a heating‐dominated stage after chlorite breakdown. Subsequently, a rheological change associated with epidote breakdown (i.e. reaction softening) occurred, highlighted by a net steepening of the P/T trajectory towards the pressure peak. On the basis of the barroisite inclusions within garnet porphyroblasts as well as the ‘hairpin’ shape of the reconstructed P–T–d path (before contact metamorphism), we infer that the unusual low T/P gradient for the Hercynian crust exposed in the Mammola Paragneiss Unit records its involvement in the Palaeotethys–Gondwana subduction beneath Laurussia during Dn‐1 under‐thrusting. We present a new palaeotectonic interpretation along the southern Hercynian belt in Calabria during the Upper Mississippian–Lower Pennsylvanian, that is consistent with previous geochronology studies.

Crystal chemistry and phase equilibria of the CaO-½Ho2O3-CoOz system at 885 °C in air

The phase equilibrium diagram of the CaO-½Ho2O3-CoOz system was determined at 885 °C in air. This diagram offers compatibility relationships in the ternary oxide system that are essential for processing and for the understanding of properties of several thermoelectric phases in the system. Four three-phase regions and three solid solution tie-line regions were determined in the CaO-½Ho2O3-CoOz system. In the CaO-Ho2O3 system, while a small solid solution region was identified for (Ho1-xCax)O(3-z)/2 (0 ≤x ≤ 0.14), Ho was not present in the Ca site of CaO. Neither the reported Ho2CoO4 phase in the Ho2O-CoOz system nor the Ca-doped (Ho1+xCa1-x)CoO4-z phase was present at 885 °C. No solid solution of the distorted perovskite, (Ho1-xCax)CoO3-z, was established at this temperature. The CaO-CoOz system consists of two calcium cobaltate thermoelectric compounds. The 2D thermoelectric oxide, (Ca3-xHox)Co4O9-z (0 ≤x ≤ 0.5), has a misfit layered structure, and the 1D Ca3Co2O6 consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a stoichiometric compound. A comparison of the phase diagrams of the CaO-½R2O3-CoOz (R = La, Nd, Eu, and Ho) systems is given.

Analysis of Mutual Transformations of the Structures of the Diagrams of Ternary Systems via the Formation of Binary Boundary Tangential Azeotropes

A consideration has been made of mutual transformations of the structures of the vapor–liquid equilibrium diagrams of ternary systems without ternary azeotropes and with monoazeotropic and biazeotropic binary components through the formation of a binary boundary tangential azeotrope with varying external conditions. Specific features of the appearance of biazeotropy at the boundaries of the concentration simplex have been determined for ternary systems with different types of structures of the vapor–liquid equilibrium diagrams.

Differential temperature control in heat-integrated pressure-swing distillation for separating azeotropes to deal with operating pressure fluctuations: Basic and explanatory data.

This data article contains basic and explanatory data of “Differential temperature control in heat-integrated pressure-swing distillation for separating azeotropes to deal with operating pressure fluctuations” [1], including thermodynamic models, vapor-liquid equilibrium diagrams, steady-state flowsheets, temperature profiles of columns, description and setpoint units of the abbreviation of inventory control loops, description of control loops of control flowsheet with DTC, control flowsheets of PCTC and DTC, temperature and composition tuning constants, faceplates and flowsheet equations, dynamic performances and integral absolute errors. It also contains other important information.

Unveiling the energetic and structural properties of Pu doped zircon through electrochemical equilibrium diagram from DFT+U calculations

Zircon (ZrSiO4) mineral is a sustainable and promising material to store of radioactive waste that has received extensive attention by material, geochemical and environmental scientists. Although the incorporation of actinide elements in zircon lattices has been experimentally studied, bare fundamental work are carried out to systemically assess the structural and chemical stabilities of Pu doped zircon. The primary aim to unveil the Pu immobilization mechanism and assess the stability of PuxZr1−xSiO4 is carried out by calculating the formation energies, electron and hole affinities, and electronic levels of Pu doped zircon based on density functional theory. Our results reveal under μ = μO−poor condition PuSi4+, PuZr1+ and PuZr0 are respectively energetically favorable to form with increasing the electronic chemical potential. Besides, PuZr4+ is energetically favorable in an n-type environment under all these three conditions (i.e., μ = μO−poor, μ = μPu/Zr, μ = μPu/Si). In addition, Pu doping will induce local structural distortion. Intriguingly however, self-repairing the symmetry of [ZrO8] polyhedra is first observed via the structural distortion in PuZr4+ configuration, which in turn could enhance the structural stability of PuxZr1−xSiO4. Ab initio molecular dynamic simulations demonstrate the configurations with negative formation energies are thermal stable at 500 K. The charge density difference and charge transfer are investigated to describe the chemical bonding nature. It is demonstrated Pu(5f)-O(2p) hybridization is more profound for interstitial Pu. Moreover, the bonding character of surrounding Zr atoms along [010] direction is almost identical to the pristine one, while it is distinctly changed towards [100] and [001] directions, showing remarkable anisotropy of PuxZr1−xSiO4. Oppositely, the ionicity in Pu–O bond is mainly featured when Zr or Si sites are substituted by Pu atoms which becomes stronger with increasing the hole doping process.