Critical Composition Research Articles

Non-conventional superconductivity in magnetic In and Sn nanoparticles

We report on experimental evidence of non-conversional pairing in In and Sn nanoparticle assemblies. Spontaneous magnetizations are observed, through extremely weak-field magnetization and neutron-diffraction measurements, to develop when the nanoparticles enter the superconducting state. The superconducting transition temperature TC shifts to a noticeably higher temperature when an external magnetic field or magnetic Ni nanoparticles are introduced into the vicinity of the superconducting In or Sn nanoparticles. There is a critical magnetic field and a critical Ni composition that must be reached before the magnetic environment will suppress the superconductivity. The observations may be understood when assuming development of spin-parallel superconducting pairs on the surfaces and spin-antiparallel superconducting pairs in the core of the nanoparticles.

Enhanced ferroelectric and piezoelectric properties of BCT-BZT at the morphotropic phase boundary driven by the coexistence of phases with different symmetries

The discovery of lead-free piezoelectric materials is crucial for future information and energy storage applications. Enhanced piezoelectric and other physical properties are commonly observed near the morphotropic phase boundary (MPB) composition of ferroelectric solid solutions. The $(1\ensuremath{-}x)\mathrm{Ba}({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}){\mathrm{O}}_{3}\text{\ensuremath{-}}x({\mathrm{Ba}}_{0.7}{\mathrm{Ca}}_{0.3}){\mathrm{TiO}}_{3}$ $(\mathrm{BZT}\text{\ensuremath{-}}x\mathrm{BCT})$ system exhibits a large electromechanical response around its MPB region at $x=0.5$. We report experimental and theoretical results of $\mathrm{BZT}\text{\ensuremath{-}}x\mathrm{BCT}$ over a wide composition range $(0.3\ensuremath{\le}x\ensuremath{\le}1.0)$. X-ray diffraction and Raman spectroscopy studies indicate a composition-induced structural phase transition from a rhombohedral $(R3m)$ phase at $x\ensuremath{\le}0.4$ to a tetragonal $(P4mm)$ phase at $x\ensuremath{\ge}0.6$ through a multiphase coexistence region at 0.45 \ensuremath{\le} $x\ensuremath{\le}0.55$ involving orthorhombic + tetragonal (Amm2 + $P4mm$) phases. First-principles calculations elucidate the phase competition in the coexistence region. The critical composition $(x=0.5)$ displays enhanced dielectric, ferroelectric, and piezoelectric properties, where notably ${d}_{33}\ensuremath{\sim}320$ pC/N. This paper provides clear evidence of Amm2 + $P4mm$ crystallographic phases in the MPB region, which is responsible for the improved functional properties.

Highly Efficient and Accurate Gas-Alkane Binary Mixture Interfacial Tension Equations for a Broad Range of Temperatures, Pressures, and Compositions

Summary Gas-alkane interfacial tension (IFT) is an important parameter in the enhanced oil recovery (EOR) process. Thus, it is imperative to obtain an accurate gas-alkane mixture IFT for both chemical and petroleum engineering applications. Various empirical correlations have been developed in the past several decades. Although these models are often easy to implement, their accuracy is inconsistent over a wide range of temperatures, pressures, and compositions. Although statistical mechanics-based models and molecular simulations can accurately predict gas-alkane IFT, they usually come with an extensive computational cost. The Shardt-Elliott (SE) model is a highly accurate IFT model that for subcritical fluids is analytic in terms of temperature T and composition x. In applications, it is desirable to obtain IFT in terms of temperature T and pressure P, which requires time-consuming flash calculations, and for mixtures that contain a gas component greater than its pure species critical point, additional critical composition calculations are required. In this work, the SE model is combined with a machine learning (ML) approach to obtain highly efficient and highly accurate gas-alkane binary mixture IFT equations directly in terms of temperature, pressure, and alkane molar weights. The SE model is used to build an IFT database (more than 36,000 points) for ML training to obtain IFT equations. The ML-based IFT equations are evaluated in comparison with the available experimental data (888 points) and with the SE model, as well as with the less accurate parachor model. Overall, the ML-based IFT equations show excellent agreement with experimental data for gas-alkane binary mixtures over a wide range of T and P, and they outperform the widely used parachor model. The developed highly efficient and highly accurate IFT functions can serve as a basis for modeling gas-alkane binary mixtures for a broad range of T, P, and x.

Tuning magnetic antiskyrmion stability in tetragonal inverse Heusler alloys

The identification of materials supporting complex, tunable magnetic order at ambient temperatures is foundational to the development of new magnetic device architectures. We report the design of $\mathrm{Mn}{}_{2}XY$ tetragonal inverse Heusler alloys that are capable of hosting magnetic antiskyrmions whose stability is sensitive to elastic strain. We first construct a universal magnetic Hamiltonian capturing the short- and long-range magnetic order which can be expected in these materials. This model reveals critical combinations of magnetic interactions that are necessary to approach a magnetic phase boundary, where the magnetic structure is highly susceptible to small perturbations such as elastic strain. We then computationally search for quaternary $\mathrm{Mn}{}_{2}({X}_{1},{X}_{2})Y$ alloys where these critical interactions may be realized and which are likely to be synthesizable in the inverse Heusler structure. We identify the $\mathrm{Mn}{}_{2}\mathrm{Pt}{}_{1\ensuremath{-}z}{X}_{z}\mathrm{Ga}$ family of materials with $X=$ Au, Ir, Ni as an ideal system for accessing all possible magnetic phases, with several critical compositions where magnetic phase transitions may be actuated mechanically.

The integration of urban streetscapes provides the possibility to fully quantify the ecological landscape of urban green spaces: A case study of Xi’an city

Urban green space is the critical composition of urban ecosystem, which provides numerous ecosystem services for urban residents, and has great value. The optimization of urban green landscape aesthetics can improve the health level of the city and enhance the enjoyment of the people. In this research, we calculated two kinds of ecological indices based on deep learning semantic recognition and multispectral remote sensing, and proposed a set of integrated multi-dimensional urban green ecological indicators, which can be used to evaluate the value of urban green ecological landscape aesthetics. These two kinds of ecological indices represent the landscape characteristics of urban green space from the perspective of overlooking and the perspective of looking around respectively. And then the regionalization method based on dynamic constraint aggregation cluster and partition (RECDAP) is used to identify the ecological homogeneous area of urban block. The results indicated that first, there are spatial differences in pedestrian perception of urban vegetation, and high-perception areas are mainly distributed in schools, parks and internal roads in large communities. Second, the green cover based on overlooking view is also mainly distributed in schools, parks, large communities and other places. Finally, the integration of indicators proves that human perception of urban green space landscape aesthetics cannot be ignored. The homogeneous areas provide a new reference for urban managers and designers to create and maintain urban green space. The addition of streetscape provides a possibility for a more objective and comprehensive evaluation of the aesthetic value of urban green space landscape, so that people can better understand the dynamic role of green space in the urbanization and human health. Public managers and urban green designers can use the ecological indices system to optimize and maintain urban vegetation by taking ecologically homogeneous areas as units.

Preponderant influence of disordered P4bm phase on the piezoelectricity of critical compositions of Na0.5Bi0.5TiO3 -based ferroelectrics

We investigated the phase boundaries of three ${\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{0.5}{\mathrm{TiO}}_{3}$-(NBT) based piezoelectric systems NBT-${\mathrm{BaTiO}}_{3}$ (NBT-BT), NBT-${\mathrm{K}}_{0.5}{\mathrm{Bi}}_{0.5}{\mathrm{TiO}}_{3}$ (NBT-KBT) and NBT-${\mathrm{SrTiO}}_{3}$ (NBT-ST), all exhibiting similar piezoelectric responses (${d}_{33}\ensuremath{\sim}180\phantom{\rule{0.16em}{0ex}}pC/N$). We found that, apart from a qualitative difference (NBT-KBT/NBT-BT exhibits R3c-P4mm interferroelectric instability and NBT-ST does not), the critical compositions of all the three systems exhibit onset of a disordered P4bm phase. Our study suggests that the preponderant effect of this distortion overrides the interferroelectric instability, limiting the piezoelectric response of NBT-BT/NBT-KBT like that in NBT-ST.

Highly enhanced discharged energy density and superior cyclic stability of Bi0.5Na0.5TiO3-based ceramics by introducing Sr0.7Ca0.3TiO3 component

The composition-induced phase transition from ferroelectric to relaxor and cycling stability is critical for energy storage application of Bi0.5Na0.5TiO3 (BNT) ceramics. The paraelectric Sr0.7Ca0.3TiO3 (SCT) component is selected to modify the ferroelectric phases of BNT ceramics and improve its energy storage properties. A tiny amount of manganese is used to reduce leakage current. High breakdown field of 210 kV/cm, large recoverable energy density of 2.64 J/cm3, and high power density of 61.89 MW/cm3 are achieved simultaneously in the SCT modified BNT ceramics. Meanwhile, an improved discharged energy density for practical application is obtained within the temperature range of 20–120 °C. By deviating from the critical composition with giant strain, the discharged energy density of 1.11 J/cm3 with excellent stability of cycling performance after 7100 cycles can be achieved. Therefore, the as-proposed solution can solve the ceramic cracking originating from high electric field-induced giant strain, and promote the practical capacitor application.

Coupled electronic and magnetic relaxation in Fe1+y Te: direct evidence for the interaction between itinerant carriers and local moments

Iron chalcogenides are of particular interests among iron-based superconductors due to their distinct properties such as high-T c on FeSe monolayer and competing magnetic correlations in Fe1+y Te. Here we report unusual transport properties observed near the critical composition of Fe1+y Te (y ∼ 0.09) where competing magnetic correlations exist. The resistivity exhibits surprising temperature-dependent relaxation behavior below T N, resulting in the increase of resistivity with time for 35 K < T < T N, but the decrease of resistivity with time for 10 K < T < 35 K. Such resistivity relaxation is intimately coupled to the magnetization relaxation and can be attributed to the glassy magnetic states induced by the competing magnetic orders. These findings demonstrate strong coupling between itinerant carriers and local ordered moments in Fe1+y Te.

Electrochemistry of High Temperature Corrosion in Molten Chloride Salt

Technological interest for the use of molten chloride salts as heat transfer and storage media in advanced nuclear reactors [1] and in concentrated solar power plants is increasing. However, alloy corrosion is the critical materials-compatibility issue for structural materials exposed to these media. Driving forces for corrosion in molten salts are impurities, temperature gradients, and activity gradients [2]. Impurities in molten salts are H2O, OH-, O2, metal oxides, and polyvalent metal ions [3].We have studied the corrosion behavior of Fe-Cr-Ni model alloys in LiCl-KCl-MgCl2 salts; the eutectic has a compromise between raw material cost, performance, and melting point for use as a coolant in a molten salt reactor. Water is soluble in high temperature molten salt; it reacts with the F- and Cl- to produce HF and HCl, which are highly corrosive – so a residual amount of water enhances corrosion rates dramatically.Water and oxygen contents of salts were removed via step-wise heat treatment under Ar gas to avoid hydrolysis. We achieved the removal of residual H2O and HCl by convecting the melt through Mg ribbons with a very high surface area. We developed a Mg|Mg2+ reference electrode for this system, provided that MgCl2 is part of the eutectic and the water concentration is low enough. It is found to be nearly perfect, as seen from electrochemical measurements.The residual water content and corrosion products such as Ni2+, Fe2+, Cr2+ in molten salts are measured electrochemically by cathodic polarization of Pt. Whilst the main focus of this study was alloying effects on corrosion, interesting data were obtained on the anodic behaviour of deposited Mg, suggesting a new level of complexity in the Mg dissolution mechanism. We will also talk about the open circuit potentials of various metals (e.g., Ni, Fe, Cr, ...) vs Mg|Mg2+, and the extent to which thermodynamics can be useful in the interpretation of the resulting data.Dealloying is the selective electrolytic dissolution of less-noble element(s) from a homogenous metallic solid solution [4]. We have studied the fundamentals of alloying effects, specifically critical alloy compositions for dealloying in model Fe-(Cr)-Ni alloys.We found that up to a specific temperature, classical dealloying happens in molten salts. Fe and Cr preferentially oxidize, and a bicontinuous microporous Ni layer forms. We discovered that the parting limit for dealloying, 55-60 at.% of the less-noble element(s) (Fe and Cr), dropped by several percentages compared with aqueous solutions because chloride salts increase surface diffusivity of the more-noble component, Ni, at the surface.We have also found that under some electrochemical conditions, superficial dealloying occurs at 62 at.% of Ni and even at 68 at.% Ni. The latter case, similar to the case with brass [5], will be explained by equilibrium of Ni from the alloy surface with Ni ion in molten salts, which deliberately was added to the salt; the exchange current increases mobility of Ni. This leaves exposed Fe or Cr sites on the surface, that can dissolve.The operating mass transport process for this type of dealloying in molten salts is "percolation dealloying”. We will also talk about the transition to a mechanism controlled by lattice vacancy diffusion which will happen at very high temperatures. References MacPherson, H.G., The molten salt reactor adventure. Nuclear Science and engineering, 1985. 90(4): p. 374-380.Sridharan, K. and T.R. Allen, Corrosion in molten salts, in Molten Salts Chemistry. 2013, Elsevier p. 241-267.Delpech, S., et al., Molten fluorides for nuclear applications. Materials Today, 2010. 13(12): p. 34-41.Newman, R.C., Dealloying, in Shreir's corrosion (4th ed.). 2010, Elsevier. p. 801-809.Newman, R.C., T. Shahrabi, and K. Sieradzki, Direct electrochemical measurement of dezincification including the effect of alloyed arsenic. Corrosion science, 1988. 28(9): p. 873-886.

Continuous Improvement in the Development of Cold Agglomeration Process to Add Value to Manganese-rich Waste Streams

World-Class Organisations strive to move away from linear economy to circular economy, where fundamental objectives are to eliminate waste and continual utilisation of resources. Circular economy and sustainability is also critical to the mining industry. Manganese mining operations and the smelting industry inherently generate Manganese rich by-products that are not saleable due to their small particle size. The bulk source of fine-sized by-products being evaluated are bag-house dust collected during smelting (below 100 microns), and ultra-fines (slimes) generated during beneficiation of the ore (below 300 microns). Other sources of fines are, among others: bag-house dust collected from conveyor systems and metal crushing and screening (below 100 microns), fines generated upon metal crushing (-3mm)) and fines from Metal Recovery Plant (-3mm). These waste streams are traditionally accumulated in lined tailings storage facilities that require continuous management to reduce environmental risk. In 1998, Assmang Manganese took an informed decision to investigate different ways on how to re-use such by-products. This paper firstly summarizes Assmang Cato Ridge experience in developing and identifying the most efficient, effective and flexible cold agglomeration process that can add value to Manganese rich waste streams. Such development aims to increase the utilization of waste streams, through agglomeration of current arising and historical furnace dust and other by-products generated during smelting operation, as well as the manganese ultra-fine ore generated at Assmang Manganese Mines. The paper examines four different cold agglomeration processes (Block or Brick-Making, Roll Press, Extrusion and High Compression-Vibration) that have been trialled by Assmang over the years. A High Compression Vibration cold-agglomeration technology, currently in use by Cato Ridge, has demonstrated unique capabilities to achieve competent agglomerates that meet critical metallurgical requirements. The use of agglomerates has become a significant part of the burden charge in the production of HCFeMn in Submerged Arc Furnaces (SAF) at Cato Ridge. The physical characteristic of agglomerates that Cato Ridge targets to feed its SAF charging bins are: maximum 10% fines below 6.0mm, minimum Shatter Index of 93% and minimum Compressive Strength of 5.0 MPa. The critical chemical composition required is Manganese content of 37% and Manganese to Iron ratio of 5.5.

Solid–Liquid–Liquid Equilibria of the System Water, Acetonitrile, and Ammonium Bicarbonate in Multiphase Reacting Systems

The salting out of acetonitrile from water in the presence of ammonium bicarbonate was studied at atmospheric pressure from 4 to 35 °C. The coexisting phases were analyzed independently with H1 nuclear magnetic resonance, ion chromatography, calorimetry, and titrations. The binodal region was described with semiempirical functions and with the UNIQUAC thermodynamic model. The critical composition at ambient temperature is given by 0.02 g/g of salt and 0.58 g/g of acetonitrile: at lower salt concentrations; this mixture is widely employed in liquid chromatography, thanks to the buffering properties of the bicarbonate. The separation of acetonitrile and water for extraction purposes, instead, is often obtained with other ammonium salts. These ternary equilibrium data can then be useful to develop extraction and analysis procedures at buffered, mildly alkaline pH. In addition, this mixture can be encountered during the acetonitrile synthesis proposed from bioethanol and bioethylene, so these multiphase equilibria govern the separation and purification of acetonitrile in specific reactors that allow the recovery of ammonium bicarbonate as a valuable byproduct. Furthermore, the solubility of this salt in alcohols and its decomposition were investigated to target its stability in multiphase reactors, extractors, and driers.

Temperature gradient interaction chromatography of linear polyethylene and isotactic polypropylene

Samples of linear polyethylene and isotactic polypropylene were separated according to their average molar mass using temperature gradient interaction chromatography (TGIC) with mobile phases at near critical composition. It is known that at the critical mobile phase composition, the adsorption of polymers is very sensitive to variations of the temperature. This effect was utilized here. The temperature of the column (Hypercarb™) was changed from 80 °C to 170 °C according to a programmed temperature gradient. Polymers were first adsorbed in the column at 80 °C and desorbed by the temperature increase. In effect, the polymers eluted at different temperatures. The higher the molar mass, the higher both the elution temperature and the elution volume. This suggests that TGIC has the potential to improve separations of polyolefins according to their molar mass and will allow to separate polyolefins according to their long-chain branching content.

Critical cluster composition from homogeneous nucleation data: application to water in carbon dioxide\u2013nitrogen carrier gases

Knowledge on critical cluster composition is important for improving the nucleation theory. Thus, homogeneous water nucleation experiments previously carried out in nitrogen and 0%, 5%, 15% and 25% of carbon dioxide ( Campagna et al. 2020a, 2021) are analyzed. The tests were conducted at 240 K and 0.1 MPa, 1 MPa and 2 MPa. The observed nucleation rates are strongly dependent on supersaturation, pressure, temperature and mixture composition. These experimentally found dependencies can be used to derive the composition of critical clusters by means of the nucleation theorem. In this way, a macroscopic quantity, nucleation rate, reveals properties of critical clusters consisting of a few tens of molecules. Two novel methods are presented for the detailed application of the nucleation theorem. The first method extends to mixtures of ,,,,,,,N>2,,,,,, components the approach used in literature for two components. The second method not only applies to N>2 mixtures in a more straightforward manner, but it can also be used for unary as well as for binary and multi-component nucleation cases. To the best of our knowledge, for the first time the critical cluster composition is computed for high pressure nucleation data of a vapor (here water) in mixtures of two carrier gases (here carbon dioxide–nitrogen). After a proper parameterization of the nucleation rate data, both methods consistently lead to the same critical nuclei compositions within the experimental uncertainty. Increasing pressure and carbon dioxide molar fraction at fixed supersaturation leads to a decrease in the water content of the critical cluster, while the adsorbed number of nitrogen and carbon dioxide molecules increases. As a consequence, the surface tension decreases. This outcome explains the observed increase in the nucleation rate with increasing pressure and carbon dioxide molar fraction at constant supersaturation.Graphic abstract

Experimental studies on critical compositions for fabricating single-phase high entropy carbides based on the calculated phase diagram of (VNbTaMoW)0.5Cx (0 < x < 0.6)

In this paper, the phase diagram of (VNbTaMoW)0.5Cx (0 < x < 0.6) was first calculated. We establish the complete phase diagram in two spatial dimensions from analysis the statistics of order phase parameters. To obtain high-entropy carbides and validate the calculated results, a series of (VNbTaMoW)C were sintered at different temperature. The single-phase carbide of (VNbTaMoW)C were synthesized at 1800 °C, which is higher than the theoretically calculated temperature in phase diagram. The reason is that the estimated temperature was calculated by mixing entropy for experimentally reported ideal solid solution models that simplified the temperature dependent parameters. Phase composition of (VNbTaMoW)C sintered at/below 1800 °C agrees well with the calculation results in phase diagram. Furthermore, we have systematically investigated the single-phase formation ability of four-metal and three-metal composition based on five elements (V, Nb, Ta, Mo, W). A total of 5 types of four-metal compositions and 10 types of three-metal compositions can be generated. However, for each composition, only 4 kinds four-metal and 6 kinds three-metal compositions can form single phase carbides. Those as-prepared single-phase carbides exhibit enhanced mechanical properties compared to the calculated values according to the rule of mixtures from constituent monocarbides.

Unusual Lower Critical Solution Temperature Phase Behavior of Poly(benzyl methacrylate) in a Pyrrolidinium-Based Ionic Liquid.

Polymer/ionic liquid systems are being increasingly explored, yet those exhibiting lower critical solution temperature (LCST) phase behavior remain poorly understood. Poly(benzyl methacrylate) in certain ionic liquids constitute unusual LCST systems, in that the second virial coefficient (A2) in dilute solutions has recently been shown to be positive, indicative of good solvent behavior, even above phase separation temperatures, where A2 < 0 is expected. In this work, we describe the LCST phase behavior of poly(benzyl methacrylate) in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide for three different molecular weights (32, 63, and 76 kg/mol) in concentrated solutions (5–40% by weight). Turbidimetry measurements reveal a strong concentration dependence to the phase boundaries, yet the molecular weight is shown to have no influence. The critical compositions of these systems are not accessed, and must therefore lie above 40 wt% polymer, far from the values (ca. 10%) anticipated by Flory-Huggins theory. The proximity of the experimental cloud point to the coexistence curve (binodal) and the thermo-reversibility of the phase transitions, are also confirmed at various heating and cooling rates.

Dynamical response of localized electron hopping and dipole relaxation in Cu1 − x Zn x Fe2O4 magnetoceramics

We report a detailed study on the dynamical response of localized electron hopping and dipole relaxation in bulk polycrystals of Zn diluted Cuprospinel (Cu1 − x Zn x Fe2O4). The variations in the dielectric dispersion and ac-resistivity (ρ ac ) were analyzed over a wide temperature (77 K ≤T ≤ 823 K) and frequency (20 Hz ≤ f ≤ 20 MHz) window for a critical composition x c = 0.4. The variation of R (f, T) followed the Maxwell–Wagner type polarization mechanism in-line with the Koops phenomenological theory. Our analysis of ρ ac (T, f) provide strong evidence to the Mott’s variable range hopping of charge transport between the localized states at low temperatures, however, thermally-activated Arrhenius like behaviour was noticed at high temperatures with E A = 656 meV for x c = 0.4. Moreover, electric modulus spectroscopic studies (M *(f, T)) reveals two distinct types of relaxation phenomena: (i) the short-range oscillations of the charge carriers within the potential well of grains and (ii) the long-range movement of charge carriers across the grain boundaries. The depressed semi-circles of the Nyquist plots and lower values of non-exponential parameter extracted from M *(f, T) suggest the non-Debye type relaxation process present in the system with a widespread distribution of relaxation times. The frequency exponent (s(x, T)) study of Jonscher’s power law reveals that the ac-conductivity follows small-polaron tunnelling followed by the correlated-barrier-hopping mechanism for 0.1. However, for x ≥ x c reorientational hopping mechanism is predominant, except for 400 K, where thermally activated Arrhenius-type conduction of charge carriers is prevalent in this spinel system. Furthermore, the tetragonally (I41/amd) distorted systems (x ≤ 0.05) exhibit less activation energy (E A − VRH ) values as compared to those of cubic-spinel symmetry (Fd-3m) which saturates at 130 meV for 0.1 ≤ x ≤ 0.6. Compositional dependent tunability of the above discussed parameters may open a constructive approach to design low energy-loss and high-resistive electromagnetic elements for microwave devices which is the key significance of the present study.

Nonhysteretic metamagnetic phase transition in Ho2In1-xAlx (0 ≤ x ≤ 0.4) by hetero-structural alloying

By hetero-structural alloying ferromagnetic hexagonal Ho2In with antiferromagnetic orthorhombic Ho2Al, the magnetic and structural changes have been observed in Ho2In1-xAlx (0 ≤ x ≤ 0.4) alloys. At the critical composition x = 0.1, the highest maxima of magnetic entropy change of 16.3 Jkg-1K−1 and the adiabatic temperature change of 6.5 K have been obtained via an unconventional hysteresis-free metamagnetic phase transitionm, which is higher than 9 Jkg-1K−1 and 5.4 K in Ho2In benchmark alloy undergoing second-order phase transition. Such increment is associated with the intensified magnetoelastic coupling. The deeper origin is proposed to be from the delocalized 5d electrons of rare-earth atoms by external field since the magnetoresistence is also maximized at the critical composition. The hetero-structural alloying strategy is demonstrated to be effective to intensify the MCE effect without causing the undesirable hysteresis.

A high-voltage, low-temperature molten sodium battery enabled by metal halide catholyte chemistry

Despite its promise as a safe, reliable system for grid-scale electrical energy storage, traditional molten sodium (Na) battery deployment remains limited by cost-inflating high-temperature operation. Here, we describe a high-performance sodium iodide-gallium chloride (NaI-GaCl3) molten salt catholyte that enables a dramatic reduction in molten Na battery operating temperature from near 300°C to 110°C. We demonstrate stable, high-performance electrochemical cycling in a high-voltage (3.65 V) Na-NaI battery for >8 months at 110°C. Supporting this demonstration, characterization of the catholyte physical and electrochemical properties identifies critical composition, voltage, and state of charge boundaries associated with this enabling inorganic molten salt electrolyte. Symmetric and full cell testing show that the catholyte salt can support practical current densities in a low-temperature system. Collectively, these studies describe the critical catholyte properties that may lead to the realization of a new class of low-temperature molten Na batteries.

Domain Growth in the Active Model B: Critical and Off-critical Composition

ABSTRACT We study the ordering kinetics of an assembly of active Brownian particles (ABPs) on a two-dimensional substrate. We use a coarse-grained equation for the composition order parameter ,where and denote space and time, respectively. The model is similar to the Cahn-Hilliard equation orModel B (MB) for a conserved order parameter with an additional activity term of strength . This model has been introduced by Wittkowski et al., Nature Comm. 5, 4351 (2014), and is termed Active Model B (AMB). We study domain growth kinetics and dynamical scaling of the correlation function for the AMB with critical and off-critical compositions. The quantity governs the asymptotic growth kinetics for the off-critical AMB, where denotes the average order parameter. For negative ,the domain growth law is the usual Lifshitz-Slyozov growth law with . For positive ,the growth law shows a crossover to a novel growth law . Further, the correlation function shows good dynamical scaling for the off-critical AMB but the scaling function has a dependency on and . We also study the effects of both additive and multiplicative noise on the AMB.

Всаливающее–высаливающее действие солей калия на двойную жидкостную систему вода–н-бутоксиэтанол с замкнутой областью расслоения

The work is devoted to the comparative characteristics of the salting-in –salting-out effect of potassium formate, nitrate and perchlorate on the binary liquid water + n-butoxyethanol system with a closed delamination region in a temperature range of 10–150°C. The introduction of potassium formate or potassium nitrate into the mixtures of the critical composition of the binary water + n-butoxyethanol system leads to a decrease in the LCST (lower critical solution temperature) and an increase in the UCST (upper critical solution temperature) of this system, while the addition of potassium perchlorate leads to an increase in the LCST and a decrease in the UCST. For three ternary systems potassium salt + water + n-butoxyethanol, the distribution coefficients of n-butoxyethanol between the aqueous and organic phases of the monotectic state were calculated for several temperatures. It has been found that the distribution coefficient increases with temperature in each system. It has been established that potassium formate and potassium nitrate have a salting-out effect, the former having a particularly strong one. Potassium perchlorate at low concentrations and relatively low temperatures is characterized by a salting-in effect, which turns into a weak salting-out effect at higher temperatures. The results obtained can be used to develop practical recommendations for carrying out selective extraction of organic solvents and extractive crystallization of salts.