Complex Phase Research Articles

Interlayer substitution enables air-stable and long-life O3-type cathode for sodium-ion batteries

The O3-type oxides (NaNi0.4Fe0.2Mn0.4O2 (NFM)) have been considered as the most commercially cathode material for high-energy-density sodium-ion batteries owing to their low price, good safety performance, and high energy density. However, their further development is seriously limited due to the complex phase transition, sluggish kinetics of Na+, and intrinsic air instability. Herein, an interlayer substituted NFM (IS-NFM) is constructed by a simple solid-state method with the introduction of alkaline-earth metal. The interlayer substitution will lead to the increase of oxygen content in the internal lattice, which will effectively suppress the irreversible phase transition during cycling and exposure to the air. In addition, the interlayer substitution effectively activated the charge compensation, leading to the mobilized cationic redox process and boosted de-/sodiated kinetic. Consequently, IS-NFM exhibits excellent capacity retention of 83.44 % at 1 C after 200 cycles and remarkable stability even at high voltage. After 15 days of exposure to the air, IS-NFM also delivers superior capacity retention (86.53 %, compared with 0.1 C) and cycling performance (82.70 % at 1 C after 200 cycles). Undoubtedly, the interlayer substitution strategy will expand a novel avenue for constructing air-stable and long-life O3-type oxides for commercial application.

Two syenitic phases in the Early Paleogene Silhouette Island volcano-plutonic complex, Seychelles

The Silhouette alkaline volcano-plutonic complex is the largest exposed Early Paleogene (62–64 Ma) igneous complex of the Seychelles microcontinent. The rocks of this study were collected from Baie Cipailles, Pte Vareur and Pte Ramasse Tout and include syenite (SiO 2 = 60–63 wt%), microgranite (SiO 2 = 70–74 wt%), tuffaceous trachyte (SiO 2 = 64–65 wt%) and a basaltic xenolith (SiO 2 = 44 wt%; MgO = 6.4 wt%; Mg# = 47.6). The silicic rocks of this study are ferroan, metaluminous to weakly peralkaline and classify as A1-type granitoids. The whole-rock Sr–Nd ( 87 Sr/ 86 Sr i = 0.703894–0.706534; ε Nd ( t ) = +0.5–+1.8) isotopes of the silicic rocks are similar to those of the basalt xenolith ( 87 Sr/ 86 Sr i = 0.703576; ε Nd ( t ) = +1.9). There is limited to no geochemical evidence for crustal contamination in any of the rocks. The syenitic rocks were probably derived by fractional crystallization of an alkaline basaltic parental magma in the upper crust and under reducing conditions ( Δ FMQ = −1). The Sr–Nd isotopes and zircon Hf ( ε Hf ( t ) = +3.3–+9.1) isotopes of the silicic rocks are indicative of a moderately depleted source. We found distinct textural, mineralogical and compositional differences between the syenitic rocks, suggesting that the Silhouette complex is composed of at least two syenitic magma pulses.

Morphological Characteristics of W/Cu Composite Nanoparticles with Complex Phase Structure Synthesized via Reactive Radio Frequency (RF) Thermal Plasma

The W/Cu binary system is characterized by its mutual insolubility and excellent wettability, making W/Cu composite materials ideal for managing thermal and electrical properties in electronic components. To optimize material properties, control over the microstructure is crucial, and nanocomposites with uniform dispersion offer significant advantages. In this study, W/Cu composite nanoparticles were synthesized by feeding a blended feedstock of tungsten trioxide (WO3) micro-powder and cupric oxide (CuO) micro-powder into a reactive radio frequency (RF) argon–hydrogen thermal plasma system. Cu-coated W nanocomposite particles were obtained through the vaporization, reduction, and condensation processes. The resulting nanocomposite particles were composed of body-centered cubic (BCC) α-W, A15 β-W, and face-centered cubic (FCC) Cu phases, with a chemical composition closely matching theoretical calculations. The phase evolution and morphological changes of the synthesized particles were analyzed as a function of heat treatment temperatures up to 1000 °C in a reducing atmosphere. Up to 600 °C, the phase composition and morphology remained stable. At 800 °C, localized diffusion and coalescence of Cu led to the formation of particulate Cu, and a significant phase transformation from metastable β-W to α-W was observed. Additionally, extensive Cu segregation due to long-range diffusion resulted in distinct Cu-rich and Cu-depleted regions. In these regions, notable sintering of W particles and the complete disappearance of β-W occurred. The results showed that the temperature-dependent redistribution of Cu plays a crucial role in the phase transformation of W and the morphology of W/Cu composite particles.

Monoclinic distortion and magnetic transitions in FeO under pressure and temperature

Fe1-xO, although chemically simple, possesses a complex structural and magnetic phase diagram. The crystal structures of Fe1-xO and its magnetic properties at extreme conditions are still a matter of debate. Here, we performed a systematic investigation on Fe0.94O up to 94 GPa and 1700 K using synchrotron X-ray diffraction and synchrotron Mössbauer source spectroscopy. We observe a transition of Fe0.94O to the monoclinic phases above 40 GPa and at high temperatures and use the group theory analysis of the observed phases to discuss their properties and their relation to the ambient pressure phases. The Mössbauer spectra of the rhombohedral and the room temperature monoclinic phase contain a component attributed to Fe2.5+, caused by the electron exchange between the Fe3+ defect and neighboring Fe2+ atoms. Our results present a structural and magnetic transitional pressure-temperature diagram of Fe1-xO and show the complex physicochemical properties of simple Fe1-xO binary oxide under extreme conditions.

On the transition of liquid dispersion states and their physical-thermodynamic nature in the development of gas-condensate reservoirs in depletion mode

While the depletion regime for gas-condensate fields may be more cost-effective, it often results in the loss of hydrocarbon condensate, which is economically more valuable than gas, and leads to the inefficient exploitation of the field in terms of condensate production. Therefore, the development of effective exploitation systems for such fields is essential. Effective exploitation of gas-condensate fields involves achieving maximum hydrocarbon condensate production in addition to maximum gas production. From this aspect, managing the condensate factor of reservoir system during the depletion regime is a critical issue. The article experimentally and theoretically investigates the phase transitions or mutual dispersion occurrences between hydrocarbon liquid and gas mixtures that occur with a decrease in pressure at reservoir temperature during the natural depletion of gas-condensate fields. During the exploitation of gas-condensate fields, it has been observed that even at pressures higher than retrograde condensation pressure, the hydrocarbon system undergoes complex phase transitions, resulting in distinct transition points due to the mutual dispersion of hydrocarbon liquid and gas. Additionally, pVT studies conducted in the laboratory have made it possible to determine the transition points of the reservoir fluid in the “liquid in gas” and vice versa dispersion states. The research has demonstrated that dependance of gas condensate factor on pressure under given isothermal natural conditions more clearly reflects the retrograde and maximum condensation, also dispersion points of the liquid components. It was found that proportionality coefficient between condensate ratio and pressure of gas-condensate system is unique for each production facility under isothermal conditions and characterizes the stability of fluid’s dispersion state. The importance of considering such transition points when designing gas-condensate field development projects has been highlighted.

Complex Phase Transitions of Fully Rigid Sphere-Rod Amphiphiles Induced by Solvent Polarity in Dilute Solutions.

We report complex macrophase and microphase transitions of rigid amphiphiles with spherical Keggin molecular clusters as the solvophilic block and rod-like rigid oligofluorene (OF) as the solvophobic block in mixed solvents of water and polar organic solvent. By properly adjusting the solvent polarity, the amphiphiles are found to respond accordingly by self-assembling into multilayered incomplete onion-like structures (10-25 vol % THF), single-layered vesicular structures (60 vol % THF), and an unexpected macrophase separation in the middle (40-50 vol % THF), which is due to the anomalous trends in Keggin solubility as a result of the nature of TBA+ counterions. The rigidity of the OF block prevents the amphiphile from assembling by following the rule of packing parameters; instead, interdigitation among different rods leads to the formation of the solvophobic domain to achieve self-assembly. The incomplete onion structures are controlled by the interdigitation of rigid rods for the number of layers and the electrostatic interaction among Keggin head groups for the interlayer distance. When the degree of interdigitation becomes lower, the self-assembly process shows a trend that can be explained by the traditional rule of packing parameter. This study demonstrates the formation of different self-assembled structures by rigid amphiphiles and their transitions induced by solvent composition. The self-assembly (microphase separation) of rigid amphiphiles in a dilute solution could indeed represent a broad area containing complicated, uncharted rules.

Surface oxygen-doping induced atom migration of iron-nickel sulfides with tailored d-band center for enhanced oxygen evolution

The rational design of tailored surface properties by surface doping is an efficient yet challenging method for enhanced OER performance. Herein, we propose atom migration effect, induced by surface O-doping to precisely control surface compositions of FeNiS2 (FNS). The FNS undergoes a surface sulfur/oxygen exchange to form FeNiS2-xOx (FNSO) structure after surface O-doping, while the bulk phases remain unchanged. In contrast, the surface Ni/Fe ratio is significantly increased due to the accelerated atom migration of nickel during surface O-doping. At elevated temperatures, the bulk phase is prone to transition into complex phases of FeNiS and FeNiO, leading to the decreased surface Ni/Fe ratio. The optimized FNSO demonstrates superior OER performance with a low overpotential of 256 mV at 100 mA cm−2, and the assembled anion exchange membrane water electrolyzer requires only 1.83 V at 1 A cm−2 with robust durability. Theoretical calculations reveal that this surface atom migration adjusts the d-band center level, optimizes surface adsorption/desorption behaviors, and expedites the OER kinetics. This work contributes to a deeper comprehension of surface modulation with desired surface properties of sulfides and other compounds for enhanced OER performance.

Bridging Thermochemical Technology and Ecology: Research Progress on Utilization of Factsage Software for Environmental Applications

Factsage is a robust thermodynamic calculation software that enables simulation and computation of complex multi-component and multi-phase system reactions. It has a variety of application fields such as metallurgy, energy, and environmental domains. This article elucidates the key functionalities of Factsage’s diverse modules, including Equilib, Viscosity, EpH, Reaction, and Phase Diagram modules. Furthermore, it delineates the present usage and research progress of the software in the realms of air pollution, water pollution, and solid waste treatment. By predicting the thermodynamic properties of pollutants, their chemical reactions, and complex phase changes, Factsage provides a critical scientific foundation for environmental decision-making and optimization of waste treatment processes. It showed its greater contributions to environmental protection and sustainable development.

Phase diagram of strongly-coupled Rashba systems

Abstract Motivated by the recent discovery of a possible field-mediated parity switch within the superconducting state of CeRh2As2 [Khim et al., Science 373, 1012 (2021)], we thoroughly investigate the dependence of the superconducting state of a strongly-coupled Rashba mono- and bilayer on internal parameters and an applied magnetic field. The role of interlayer pairing, spin orbit coupling, doping rate and applied magnetic field and their interplay was examined numerically at low temperature within a t-J-like model, uncovering complex phase diagrams and transitions between superconducting states with different symmetry.

Effect of electric arc surfacing on the structure and properties of coatings

Surfacing, like welding, is associated with heating metals in a wide range of temperatures and subsequent cooling of heated zones at different rates. This leads to complex structural and phase changes that are crucial for operational properties of the “protected material – coating” joint. The structure and properties of the alloyage zone of these two materials depend on the degree of penetration, nature of the intermediate layers that arise, and carbon diffusion in the boundary areas. When surfacing on low-carbon steel, depending on the composition of the deposited metal, the structures with a predominant amount of martensite or austenite can be obtained in the alloyage zone, depending on carbon content. The structure and mechanical properties of the bimetallic joint between carbon steel and stainless steel were studied depending on the modes of electric arc surfacing (submerged arc surfacing in one pass, in argon for one and two passes). It was established that the structural and phase composition of the deposited metal is austenite, finely dispersed carbides and a needle component. The structure of the layer deposited in argon in one pass is more homogeneous and does not contain defects. The microhardness increases smoothly along the depth of the deposited layer. As a result of surfacing in argon in two passes, the joint has a homogeneous microstructure, but a large number of microdefects are formed in the layer, which can further lead to the formation of a crack near the alloyage boundary. In submerged surfacing, the heating rate and specific heat input are insufficient, therefore, the surfacing bath is poorly mixed, which leads to a suboptimal structure and the formation of thermal stresses at the alloyage boundary and to the formation of a coating that is heterogeneous in structure and microhardness.

A novel meshless radial basis reproducing kernel particle approach for 3D thermo-mechanical analysis of mushy zone phase-change problems

This paper presents a three-dimensional thermo-elastoplastic computational model for the analysis of phase change problems involving the mushy zone. The model utilizes a novel meshless radial basis reproducing kernel particle approach, incorporating a high-order kernel that integrates Gaussian and cosine functions. An energy balance equation for the entire domain is formulated using the effective heat capacity method, based on the enthalpy formulation. The governing equations are discretized using the Galerkin weak form to compute thermal residual stresses, with essential boundary conditions enforced through the penalty method. Plastic deformation is characterized using the von Mises criterion with isotropic hardening, and the strain term resulting from temperature-dependent material properties is incorporated into the incremental solution process. Determination of the plastic strain increment is based on the Prandtl–Reuss flow rule. The accuracy and efficiency of the proposed meshless approach were rigorously evaluated through numerical examples encompassing two- and three-dimensional problems. The computational results were compared against available analytical and validated numerical solutions. This comprehensive assessment substantiated the robustness and precision of the developed technique. The case studies presented elucidate the capacity of the novel meshless model to effectively predict temperature distributions and residual stress fields within mushy zone phase change phenomena, accommodating both regular and irregular geometries under various boundary conditions. Notably, the model demonstrated consistent stability and high accuracy across the spectrum of simulated scenarios, thus underscoring its potential as a valuable tool for investigating complex phase change processes.

X-ray spectroscopic investigation of crystal fields in Ce2Rh1−xIrxIn8 heavy fermions

The higher dimensionality in the crystal fields of the Ce2MIn8 (M=Rh,Ir) compounds and its interplay with hybridization and disorder are key ingredients to understand the complex phase diagrams by this family, which have been explored extensively by macroscopic techniques. Here, we present an investigation of the crystal-electric field schemes of Ce2Rh1−xIrxIn8 using x-ray absorption spectroscopy. Our full multiplet calculations for the 4f1 configuration of Ce3+ to describe the temperature-dependent linear dichroism in Ce2MIn8 are consistent with a Γ71=1−α2·|∓32〉−|α|·|±52〉 ground state containing a predominant |±3/2〉 contribution that increases further with x. This enhancement is believed to favor superconductivity in Ce-based heavy fermion materials, observed in previous results in the CeMIn5 family. Our recent observations shed light on the unexpected emergence of the ambient-pressure superconducting dome in the center of the composition phase diagram and its subsequent suppression on the Ir-rich side due to the early onset of fluctuations associated with the structurally more disordered state, inferred from previous neutron magnetic diffraction experiments. Published by the American Physical Society 2024

Dynamical decoding of the competition between charge density waves in a kagome superconductor

The kagome superconductor CsV3Sb5 hosts a variety of charge density wave (CDW) phases, which play a fundamental role in the formation of other exotic electronic instabilities. However, identifying the precise structure of these CDW phases and their intricate relationships remain the subject of intense debate, due to the lack of static probes that can distinguish the CDW phases with identical spatial periodicity. Here, we unveil the out-of-equilibrium competition between two coexisting 2 × 2 × 2 CDWs in CsV3Sb5 harnessing time-resolved X-ray diffraction. By analyzing the light-induced changes in the intensity of CDW superlattice peaks, we demonstrate the presence of both phases, each displaying a significantly different amount of melting upon excitation. The anomalous light-induced sharpening of peak width further shows that the phase that is more resistant to photo-excitation exhibits an increase in domain size at the expense of the other, thereby showcasing a hallmark of phase competition. Our results not only shed light on the interplay between the multiple CDW phases in CsV3Sb5, but also establish a non-equilibrium framework for comprehending complex phase relationships that are challenging to disentangle using static techniques.

Mechanism of Rejuvenation in Aged SBS-Modified Asphalt by Density Functional Theory

As a large area of SBS-modified asphalt pavement entered the maintenance period, the aging and rejuvenation of SBS-modified asphalt have attracted attention in recent years. In order to further study the rejuvenation of aged SBS-modified asphalt, both rheological experiments and quantum mechanical simulations were used. Complex shear modulus (G*) and phase angle (δ) were used to analyze the rejuvenation effect of aged SBS-modified asphalt. Electron density, binding energy (Ebinding), and charge transfer number (Qtransfer) were used to observe the process of rejuvenation in aged SBS-modified asphalt. The results show that compared to asphalt components, SBS polymer was the least stable and most susceptible to breaking. After oxidative aging, SBS polymer with its aging products could impair the rejuvenation in aged asphalt. The interaction between aromatic components in rejuvenator and asphaltenes in aged asphalt was unstable and could be influenced by asphalt aging level. The interaction between heavy component molecules in aged asphalt with saturate component molecules in rejuvenator are closer than those with aromatic components molecules. The binding energies between saturate components in rejuvenator and asphaltenes in aged asphalt could be served as an evaluation indicator of rejuvenation.

Prilling and Coating Strategy to Synthesize High-Performance Spherical NaNi0.4Fe0.2Mn0.4O2 Cathode Materials for Sodium Ion Batteries.

Low-cost sodium ion batteries are of great significance in large-scale energy storage applications. With its high energy density and simple synthesis process, layered transition-metal oxides have become one of the most likely sodium ion battery cathode materials to replace lithium ion batteries in the energy storage market. Here, we report a prilling and MoS2 coating strategy to prepare the spherical cathode material. The spherical micronano particles shorten the diffusion path of Na+, restrain the complexity phase transitions, and enhance the tap density of the materials. In addition, the MoS2 coating improves the electrical conductivity of the material and the structural stability of the cathode material in air. The initial specific discharge capacity is 148.4 mA h g-1 at 0.1 C, which can be maintained at 128.9 mA h g-1 after exposure to air for 10 days. This method dramatically improves the energy density and structural stability of the cathode material, which provides a new scheme for preparing high-performance sodium ion batteries.

A voltammetrically potentionmetric pH sensor based on multiply hydroxylated porphyrin

AbstractUsing voltammetry to readout potentiometrically the solution acidity requires easy pH tunability of the probe's redox properties. In this work, tri‐hydroxyphenyl porphyrin (POH3) was synthesized as the electrochemically active probe to develop a voltammetrically potentiometric sensor (VPS) with a pH‐sensitive response. By comparing POH3 with control di‐ and mono‐hydroxyphenyl porphyrins (POH2 and POH1), we found that protonation of the pyrrole macrocycle, electron communication of the para‐hydroxyl groups with the pyrrole nitrogens during structure tautomerization, and the presence of multiple ionizable hydroxyl groups are the critical factors to report reversibly the pH‐sensitive VPS response at the appropriate potential range. Common metal ions have negligible effects on the sensor performance. In comparison to the conventional potentiometric sensor (CPS), our VPS strategy benefits from the advantage that the electrode modification is not required. Thus, the complex phase boundary models necessary for CPS are unnecessarily involved in explaining the potential response.

Effect of Si content on novel medium-Mn complex phase steels

Effect of Si content on novel medium-Mn complex phase steels

An accurate and transferable machine learning interatomic potential for nickel

Nickel (Ni) is a magnetic transition metal with two allotropic phases, stable face-centered cubic (FCC) and metastable hexagonal close-packed (HCP), widely used in structural applications. Magnetism affects many mechanical and defect properties, but spin-polarized density functional theory (DFT) calculations are computationally inefficient for studying material behavior requiring large system sizes and/or long simulation times. Here we develop a “magnetism-hidden” machine-learning Deep Potential (DP) model for Ni without a descriptor for magnetic moments, using training datasets derived from spin-polarized DFT calculations. The DP-Ni model exhibits excellent transferability and representability for a wide-range of FCC and HCP properties, including (finite-temperature) lattice parameters, elastic constants, phonon spectra, and many defects. As an example of its applicability, we investigate the Ni FCC-HCP allotropic phase transition under (high-stress) uniaxial tensile loading. The high accurate DP model for magnetic Ni facilitates accurate large-scale atomistic simulations for complex phase transformation behavior and may serve as a foundation for developing interatomic potentials for Ni-based superalloys and other multi-principal component alloys.

Correlated electron physics near a site-selective pressure-induced Mott transition in α-LiFe5O8

The Mott insulator-to-metal transition (IMT) driven by electron correlations has been among the main research topics in materials science over the past decades. The complex interplay between electronic and lattice degrees of freedom leads to various transition scenarios. Of particular interest may be the case of a transition involving the formation of complex phases comprising regions that differ significantly in their physical properties within the same material. Here, we present the results that advance the understanding of the IMT phenomenon, offering the documentation of a pure site-selective mechanism that is not complicated by any structural and spin transformation. Combining XRD, resistivity, Mössbauer and Raman spectroscopy measurements, we provide evidence for a pure pressure-induced Mott transition in α-LiFe5O8, characterized by site-selective delocalization of electrons, leading to the formation, above ~65 GPa, of a site-selective Mott phase consisting of metallic and insulating sublattices. We note that the electron delocalization in the partially disordered octahedral sublattice cannot be understood purely in terms of a Mott transition, the Anderson-Mott transition picture seems more adequate.

Quantum multicast based on joint remote state preparation

Effective propagation of information among multiple users is the purpose of realizing large-scale quantum communication networks. In this paper, multicast protocols for any single, two and three qubits with real amplitude and complex phase information are presented. They were realized using a composite of Greenberger–Horne–Zeilinger states as shared channels. Joint remote state preparation was the main method for completing quantum multicast. At the same time, quantum state tomography of the schemes was carried out on the IBM Quantum platform. The obtained states were compared with the target states by fidelity. The analysis of communication efficiency and noise effects shows that our protocol has advantages in the case of complex coefficients.