Ternary Melts Research Articles

EFFECT OF FAR-FIELD FLOW ON THE GROWTH OF COLUMNAR CRYSTAL IN TERNARY UNDERCOOLED MELT

The asymptotic method has been used to investigate the columnar crystals growth subjected to far-field flow in ternary undercooled melt under non-isothermal conditions, and approximate analytical expression of radius and interface growth rate of columnar crystals growth have been given. It is found that the flow causes columnar crystal to grow faster in the upstream direction and slower in the downstream direction, and the growth of columnar crystals in flowing ternary melt is also affected by impurity content, that is, the higher the impurity content, the faster the columnar crystal grows in the upstream direction and the slower the growth in the downstream direction. The growth problem of columnar crystals from multi-component melt under flow is more complicated than that of a pure melt because it involves both the heat transport process and mass transport in the solute. The results show that the deflection angle of columnar crystals is a result of interaction of flow and impurity content.

Kinetic study of vacuum evaporation of elements from ternary melts; case of dilute solution of P in Si-Al melts

This research is devoted to study phosphorus removal from Si-Al alloys by vacuum refining of the ternary system of dilute solutions of P in Si-20 wt%Al. The experiments were carried out in an induction furnace and after the refining process, the melt was characterized by ICP-MS technique to trace the concentration change of the volatile elements. The experimental results show that P removal from Si-Al-P melts takes place faster compared to Si-P melts and Al evaporates during the vacuum refining as well. The empirical kinetics of P and Al evaporation is discussed and the apparent activation energy for P and Al evaporation from Si-Al melts is obtained as EP=249.4kJ·mol-1and EAl=144.8kJ·mol-1 respectively. Results show that the composition of the melt changes continuously during the refining process due to rapid Al evaporation. In order to investigate the evaporation kinetics of the melt constituents, we developed a numerical approach by applying the Hertz-Knudsen-Langmuir equation for evaporation. This approach can be applied to model the evaporation of the melt constituents in a ternary system whose composition changes during the vacuum refining process. The model is validated with performed experimental results and it can be applied to discuss the effect of temperature, pressure, initial melt composition on the time of vacuum refining.

Chemical effect on the structural and dynamical properties in Zr-Ni-Al liquids

We develop an embedded-atom method (EAM) model to perform classical molecular-dynamics computer simulations of a model of Zr-Ni-Al ternary melts, based on the existing binary ones. The EAM potential is validated against a broad range of experimental data for the liquid melt, including both static-structure factors and dynamical data on the mass-transport coefficients. We use our simulation model to address the structural and dynamical changes induced by a systematic replacement of Zr by Al in ${\mathrm{Zr}}_{75\ensuremath{-}x}{\mathrm{Ni}}_{25}{\mathrm{Al}}_{x}\phantom{\rule{4pt}{0ex}}(x=0--30)$ ternary alloys. We find strong chemical-ordering effects exhibited as the locally preferred structure when the Al-concentration ${c}_{\text{Al}}$ is increased. Along with the chemical effects, effective-power-law relations are found between the self-diffusion coefficients in the melts, with an exponent that monotonically decreases with increasing Al concentration. The associated Stokes-Einstein relation between diffusivity and viscosity breaks down at higher temperature upon Al addition. We also address the influence of Al admixture on the vibrational spectrum of the melt. With increasing ${c}_{\text{Al}}$, sound waves move faster, and an optical vibrational mode is found.

Structure of liquid Al-Ge-Ni melts in a wide composition range

X-ray diffraction study of the Al-Ge-Ni melts along different sections of the ternary phase diagram has been discussed. The measurements were taken at 1000 °C or at temperatures on 50° above liquidus for compositions with high melting point. It has been shown that AlNi interactions play the most important role in the formation of the local atomic structure in the Al-Ge-Ni melts. The most significant decreasing of the nearest interatomic distance (R1) takes places with addition of Ni to binary AlGe alloys. There is a competition between Al and Ge atoms in the formation of local atomic structure around Ni atoms. For ternary melts with high Ge content the influence of GeGe pairs increases resulting in the formation of the clusters with structure similar to the liquid germanium. The ribbons of the Al79Ge15Ni6, Al61Ge29Ni10 and Al61Ge15Ni24 alloys have been obtained by rapid solidification from the liquid state. The phase analysis of the as-quenched and annealed ribbons has been discussed.

Formation of short-range order in Al–Ge–Fe melts: influence of composition

ABSTRACTThe short-range order in Al–Ge–Fe melts has been studied by X-ray diffraction and reverse Monte Carlo simulations in wide concentration range. Influence of the replacement of one component by another while the content of third component is constant on the formation of a local structure of ternary melts has been discussed. It has been shown that at Ge content less than 30 аt. % Ge atoms are uniformly distributed in the volume of the Al–Ge–Fe melts and atomic clusters with structure similar to the liquid germanium are formed at content more than 30 аt. % Ge. The addition of the third component (Ge or Al) to the binary Al–Fe or Fe–Ge melts, correspondingly, results in competition between Al and Ge atoms in formation of the local structure around Fe atoms. The obtained concentration dependences of the nearest neighbour distances point out that the ternary interactions take place in the Al–Fe–Ge melts.

Ternary melt blend based on poly (lactic acid)/chitosan and cloisite 30B: A study of microstructural, thermo-mechanical and barrier properties

Abstract In this study, blends were developed based on poly (lactic acid) (PLA) containing chitosan (CHS) extracted in our laboratory and an organically modified montmorillonite (cloisite 30B) at different amounts from 1 to 4 (in wt.-%). Tensile samples were prepared using twin-screw extrusion followed by injection molding, and films were obtained by press compression. The morphological and mechanical results showed a phase segregation and poor adhesion between the polymers. Indeed, the elongation at break and thermal stability had undergone a major decrease when adding chitosan to the PLA matrix. Glass transition temperature (Tg), melt temperature (Tm) and recrystallization temperature (Tc) decreased with the addition of chitosan, whereby an increase in crystallinity indicated a nucleation effect showing the same results as with the addition of cloisite 30B. An interesting effect of cloisite 30B was found when it was incorporated into the PLA/CHS blend especially with respect to a 4 wt.-% of cloisite 30B amount. The loss of elongation at the break was partially compensated and the thermal stability and crystallinity were improved. The water vapor permeability (WVP) and water vapor transmission rate (WVTR) of PLA/chitosan blends were higher than those for the neat PLA. By incorporating the C30B into the PLA/CHS blends, very interesting and good barrier properties were recorded as compared to neat PLA and PLA/CHS composites.

Electrochemical behaviors and electrolytic separation of Th(IV) and Ce(III) in ThF4-CeF3-LiCl-KCl quaternary melt

Abstract The extraction and recycle of thorium is an essential step in the thorium-uranium closed fuel cycle designed for Thorium-based Molten Salt Reactor system (TMSR), and the separation of thorium from FPs especially lanthanides is a key issue in the thorium recovery. In this paper, the electrochemical behaviors of Th(IV) and Ce(III) on Mo electrode were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) techniques at 773 K in ThF4(3 wt%)/CeF3(0.3 wt%)-LiCl-KCl ternary melt and CeF3(0.3 wt%)-ThF4(3 wt%)-LiCl-KCl quaternary melt, respectively. The reduction peaks of Th(IV)/Th(0) and Ce(III)/Ce(0) were at −1.83 V and −2.21 V (vs. Ag/AgCl) in the respective ternary melt, respectively, which were same with the values in the quaternary melt; however, the oxidation peaks in the CeF3-ThF4-LiCl-KCl melt shifted negatively about 0.1 V. Pulsed potential electrolysis of quaternary melt revealed that 98.9% of Th(IV) can be electrochemical separated from the melt with almost all cerium remaining in the melt, based on the inductively coupled plasma atomic emission spectrometer (ICP-AES) results.

Solubility of TiO2 in NaF-CaF2-BaF2 Melts

The solubility of TiO2 in NaF-CaF2-BaF2 ternary eutectic melts was investigated at the temperature range of 1025–1150 °C. The least-squares equation was obtained from the relationship between the reciprocal temperature and the natural logarithm of the titanium concentration in the melts saturated with TiO2. The corresponding partial molar enthalpy of dissolution of TiO2 was found to be 188 kJ/mol. The titanium saturation concentration was 3.73 wt% at 1100 °C. From the titanium concentration change with the added amount of TiO2 at different holding time after a final stirring, it was found that not only complete dissolution of TiO2 but also enough sedimentation of excessive TiO2 should be guaranteed to obtain more reliable solubility data. The holding time of 10 h was found to be enough for the excessive TiO2 particles to settle down in our experimental conditions. It is noteworthy that in case of adding TiO2 in excess of its solubility, the Ba1.12(Ti8O16) phase was observed at the lower and bottom of the solidified salt ingots.

Ternary Systems LiBr–LiVO3–Li2CrO4 and KBr–KVO3–K2CrO4

The binary system KVO3–K2CrO4 and two ternary systems, LiBr–LiVO3–Li2CrO4 and KBr–KVO3–K2CrO4, were studied. In the ternary systems, the compositions and melting points of eutectic alloys were determined by differential thermal analysis: (49.0 mol % LiBr, 5.0 mol % LiVO3, 46.0 mol % Li2CrO4, 400°C) and (17.0 mol % KBr, 78.0 mol % KVO3, 5.0 mol % K2CrO4, 458°C), respectively.

Mixing effects in a ternary Hf-Zr-Ni metallic melt

We study the effect of the substitution of Zr by Hf on the dynamical behavior in the Zr36Ni64 melt. A reduced measured self-diffusion coefficient and a higher measured melt viscosity for an increased amount of Hf were observed. The ternary Hf10Zr25Ni65 melt, which exhibits a pronounced deviation from Arrhenius behavior over a studied temperature range of 550 K, can be accurately described by the scaling law of mode-coupling theory (MCT) with almost equal parameters for the self-diffusion and the viscosity. Although we only substitute alloy components with a nearly equal atomic size and the measured overall packing fraction remains almost unchanged, the dynamics in Hf10Zr25Ni65 are slower compared to Zr36Ni64. This corresponds also to a higher critical temperature Tc and might be induced by different chemical interactions in the melts. The increased Tc results in a significantly smaller difference between liquidus and critical temperature ΔTLC=TL−Tc for the ternary melt in comparison with Zr36Ni64, which may favor the glass formation in the Hf10Zr25Ni65 melt.

Phase-field simulation and analytical modelling of CaSiO3 growth in CaO-Al2O3-SiO2 melts

Isothermal crystallization of a hexagonal crystal (Wollastonite) in ternary melts (CaO-Al2O3-SiO2) was simulated by quantitative phase-field simulation and analytical modelling. The dependence of initial composition, undercooling, interfacial energy and anisotropy strength on the growth behavior of Wollastonite was comprehensively investigated. According to simulation results, a transition from flat to dendritic growth of CaSiO3 occurs; the formation of dendritic Wollastonite is favorable at a lower Al2O3 content, a lower temperature and a higher anisotropy. When temperature increases, the transition prefers taking place at lower interface energy. Simulations also show that the tip velocity firstly increases until it reaches a maximum value and then decreases slowly with further decreasing the temperature, while the velocity only increases at a lower interfacial energy level. For anisotropy strength, its increase causes a higher tip velocity. Furthermore, validation of these parameter effects was performed by comparing the simulation results with an analytical model, showing quantitatively good agreement, when solute interaction was taken into account in the analytical model.

Electrochemically exfoliated high-yield graphene in ambient temperature molten salts and its application for flexible solid-state supercapacitors

Electrochemical exfoliation of graphite has emerged as a potentially scalable approach to prepare graphene. However, most of exfoliated graphite particles are inhomogeneous and multilayer stacked structures including tens of layers thick graphite exist inevitably, thus the yield of few-layer graphene remains limited. In this study, we here propose a high-yield, scalable electrochemical exfoliation method in a ternary deep eutectic melts containing acetamide, urea and ammonium nitrate, where high viscosity, higher anionic intercalation potential and low migration speed can bring anions with solvents could co-intercalated into graphite uniformly, expand the interlayer of graphite gallery and then form steady graphite intercalation compounds, affording to complete sufficient intercalation. Finally decomposition of the intercalant facilitates expanded graphite to be exfoliated into graphene. Consequently, the yield is improved to 76% and the product primarily consists of 1–5 layer graphene, which exhibits a specific surface area (878 m2 g−1) close to the theoretical value of three-layer graphene. Furthermore, all-solid-state flexible supercapacitors based on the graphene deliver a high area capacitance of 120 mF cm−2, excellent mechanical flexibility and cycling stability (97.2% retention after 10000 cycles). This approach offers the potential for cost-effective, environmentally friendly and large-scale production of graphene and numerous advanced applications.

Interaction of Components in Cu–Fe Glass-Forming Melts with Titanium, Zirconium, and Hafnium. II. Temperature–Concentration Dependence of Thermodynamic Mixing Functions

The formalism of the associated solution model for ternary melts with both strongly interacting components and components exhibiting repulsion is described. A set of model parameters that adequately describe the thermodynamic properties of melts of three-component Cu–Fe–(Ti, Zr, Hf) systems and boundary two-component systems is established. The thermodynamic mixing functions of ternary melts are calculated in the entire range of compositions and over a wide range of temperatures. In most of the concentration triangle, the thermodynamic properties of melts are characterized by negative deviations from ideal behavior. The thermodynamic properties of melts adjacent to the copper–iron side of the concentration triangle are characterized by positive deviations from the Raoult law. The range of values and topology of the excess thermodynamic mixing functions of Cu–Fe–(Ti, Zr, Hf) melts are determined by pair interactions of the components.

The dynamics of nucleation and growth of a particle in the ternary alloy melt with anisotropic surface tension.

The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.

Conductivity of molten LiCl–KF–ZrF4 mixtures

Specific conductivity of molten LiCl–KF–ZrF4 mixtures was measured for the first time by the reference capillary method using an ac bridge. In the ternary salt systems, the study was performed at a molarfraction ratio between the alkali metal halides of 1: 3, 1: 1, and 3: 1. The temperature dependences of specific conductivity were determined for all melt compositions. The calculated molar conductivities λ of studied LiCl–KF–ZrF4 ternary melts and their relative deviations from the ideal values enable us to infer the processes that proceed during mixing of the melt components.

On the theory of ternary melt crystallization with a non-linear phase diagram

The present study is concerned with a theoretical analysis of unidirectional solidification process of ternary melts in the presence of a phase transition (mushy) layer. A new analytical solution of heat and mass transfer equations describing the steady-state crystallization scenario is found with allowance for a non-linear liquidus equation. The model under consideration takes into account the presence of two phase transition layers, namely, the primary and cotectic mushy regions. We demonstrate that the phase diagram nonlinearity leads to substantial changes of analytical solutions.

Phosphate: a neglected argument in studies of ancient glass technology

The phosphate content of ancient alkali-glass has been tested as an indicator for biogenic ash, used in glass production. The living tissue of plants and vertebrates accumulates phosphate that remains in native ash as a main component (1 to over 10 wt%) forming together with biologically essential element oxides a complex chemical fingerprint that characterises any glass made with it. If, instead of native plant ash its alkali extract is used, soluble oxides are concentrated in the extract whilst insoluble oxides get depleted, leading to a different elemental fingerprint of the glass. Geogenic raw-materials for glass production like quartz-rich sand, evaporitic natron, or limestone are virtually phosphate free (below detection limit up to ≈0.15 wt%). Several collections of ancient glass stemming from different archaeological excavations, regions and times have been analysed by instrumental methods (WD-XFA, ED-XFA, thermal techniques), i.e. flat- and hollow K–Ca glass dated 1699/1714 N = 340, Na–Ca glass 13th/14th cy N = 94, Na–Ca glass 7th/9th cy N = 110, and alkali-Ca glass La Tene N = 395. Although the phosphate content of native alkali plant ash gets diluted with quartz sand by a factor of roughly two in glass production, it remains a main component of the product glass. Wood-ash glass contains 1–3 wt% phosphate, whilst glass manufactured from halophyte ash contains around 0.2–1 wt%. When processed wood-ash is used, the phosphate content in glass sinks below 1 wt%, the depletion factor amounting to roughly 8–15. Glass made from evaporitic soda displays phosphate contents below 0.2 wt% in the cases examined. The phosphate content of ancient alkali glass thus indicates whether virtually phosphate-free evaporitic soda has been used as a flux, or native ash of halophile plants. Ternary melting diagrams reveal at least three groups of alkali glass: Naturally coloured forest glass displays a broad distributional pattern with minimum melting temperatures ranging from 1200 to ≥1450 °C, colourless potash-extract glass from 900 to ≈1200 °C, and the typical, tight cluster of Roman sodium-calcium glass ranges from 800 to ≈900 °C. The wide-spread sodium-lime glass made with native halophytic ash, contains besides Na2O as the chemical main component always some K2O, and melting temperatures range from 800 to ≈1000 °C.

Novel synthesis of PbS nanorods using amide-based ternary eutectic melt as solvent

Lead sulphide (PbS) nanorods were successfully prepared via elemental-direct-reaction method in the amide-based ternary eutectic melt (acetamide–urea–ammonium nitrate) at 60 °C for 12 h. The effect of reaction temperature on morphology of products has been investigated. The products were characterised by X-ray diffraction, scanning electron microscopy and transmission electron microscopy to derive crystallinity, size and morphology of the products. UV–vis and photoluminescence spectral analysis were carried out to determine the optical properties of the PbS materials.

Pre-formulation of biofuels: Kinematic viscosities, low-temperature phase behaviour and nanostructuring of ethanol/“ethanolotrope”/rapeseed oil mixtures

As ethanol and rapeseed oil are not miscible, tributyl citrate, 2,5-dimethylfuran (DMF), 2-methylfuran (2-MF), 2-methyltetrahydrofuran (2-MTHF), methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), rapeseed oil FAME-biodiesel (FAME), 1-heptanol (HepOH) and 2-ethylhexyl nitrate (EHN) are used as green mixing agents or “ethanolotropes”. The area of existence of clear and monophasic mixtures as well as biphasic liquid/liquid solutions, determined in a previous work, are reported at 25°C using ternary phase diagrams. In the present work, some of these ternary diagrams are completed by investigating their critical points (CPs). Further, the kinematic viscosity (kV) of different binary and ternary, clear and monophasic mixtures is measured at 25 and 40°C and their phase behaviour is studied at 0, −15 and −20°C. Dynamic light scattering (DLS) experiments are performed on various samples at 25°C and the results are discussed with respect to previous measurements including DLS, static light scattering (SLS), small and wide angle X-ray scattering (SWAXS) and conductivity. Close to the CP of the investigated systems, the highest scattering intensities (SIs) can be observed as well as a distinct increase of the slope of the kV versus the rapeseed oil concentration. Evaluating these results, the high viscosities can be associated with the formation of a rapeseed oil continuum. Further, the monophasic domain close to the CP can be considered as bicontinuous-like. For every used “ethanolotrope”, the mixtures meet the required ASTM D6751 standard for the kV of biodiesel. Thus, rules for possible adjustments to reach this standard by varying the nature and the quantities of the “ethanolotropes” are proposed. Ternary and binary melts with high amounts of rapeseed oil can meet the kV standard and are clear and monophasic below 0°C or even below −15°C. Binary mixtures of DMF or 2-MF with high amounts of rapeseed oil (70wt%) show no phase transitions during several hours at −20°C and form reversible, monophasic and clear gels. As the kV of these two binary mixtures is slightly above 6mm2/s at 40°C, they nearly meet the kV standard. Replacing ethanol by “ethanolotropes” like 2-MTHF or HepOH can lead to an increase of the monophasic region of these ternary mixtures at low temperatures. Moreover, this temperature dependence could be associated with the nanostructuring, since mixtures located in the bicontinuous-like regions seem to be more sensitive regarding their phase behaviour.

Structure of the Al–Ge–Fe alloys in the liquid and solid state

X-ray diffraction study of liquid and solid Al–Ge–Fe alloys along the sections Al-Fe33.3Ge66.7, Fe-Al65Ge35 и Ge-Al78Fe22 has been discussed. It has been shown that addition of third component to the corresponding binary melt leads to the atomic clusters with structure similar to liquid germanium due to energy inequality of interactions in Al–Fe and Fe–Ge pairs and competition between Al and Ge atoms in formation of local structure around Fe atoms in the ternary melts. The Al88Ge8Fe4, Al68Ge21Fe11, Al64Ge18Fe18, Al55Ge30Fe15 melts have been quenched by melt spinning technique. The fully amorphous state was obtained only for the Al55Ge30Fe15 ribbon, the one with composition Al68Ge21Fe11 is amorphous-crystalline and Al88Ge8Fe4 и Al64Ge18Fe18 ribbons are microcrystalline. A new hexagonal τ1 phase (a=9.75(1)Å, c=8.80(1)Å) in the ingot Al55Ge30Fe15 and Al41Ge39Fe20 alloys and a new tetragonal phase τ2 (a=5.11(3)Å, c=4.60(2)Å) in the ingot Al20Ge53Fe27 alloy have been found. The annealed at 623K ribbons with composition Al88Ge8Fe4 and Al68Ge21Fe11 contain a new hexagonal phase τ3 (a=6.709(5)Å, c=9.07(1)Å), which is missing in the ingot.