Phase Evolution Research Articles

A Versatile Metal‐Organic‐Framework Pillared Interlayer Design for High‐Capacity and Long‐Life Lithium‐Sulfur Batteries

Developing high‐performance lithium‐sulfur batteries is a promising way to attain higher energy density at lower cost beyond the state‐of‐the‐art lithium‐ion battery technology. However, the major issues blocking their practical application are the sluggish kinetics and parasitic shuttling reactions for sulfur and polysulfides. Here, pillaring multilayer graphene with the metal‐organic framework (MOF) demonstrates the substantial impact of a versatile interlayer design in tackling those issues. Unlike regular composite separators reported so far, the participation of tri‐metallic Ni‐Co‐Mn MOF (NCM‐MOF) as pillars supports the construction of an ion‐channel interconnected interlayer structure, unexpectedly balancing the interfacial concentration polarization, spatially confining the soluble polysulfides and vastly affording lithiophilic sites for highly efficient polysulfide sieving/conversion. As a demonstration, we show that the MOF‐pillared interlayer structure enables outstanding capacity (1634 mAh g‐1 at 0.1C) and longevity (average capacity decay of 0.034% per cycle in 2000 cycles) of lithium‐sulfur batteries. Besides, the multilayer separator can be readily integrated into the high‐nickel cathode (LiNi0.91Mn0.03Co0.06O2)‐based lithium‐ion batteries, which efficiently suppresses the undesired phase evolution upon cycling. These findings suggest the potential of “gap‐filling” materials in fabricating multi‐functional separators, bring forward the pillared interlayer structure for energy‐storage applications.

Hierarchy and mobility of Latin America and Caribbean container ports

Research on port hierarchies within a maritime region is crucial for comprehending the dynamics of seaborne trade and the broader trends within the maritime sector and related supply chains. This study investigates the evolution of the Latin America and the Caribbean (LAC) container ports and regional sub-systems from 2000 to 2022, analyzing traffic dynamics, shifts in port throughput rankings, and market concentration trends in and among the different coastal regions. Conceptually, this analysis benefits from the notion of evolutionary phases, revealing the stages of a port system's development. Methodologically, 49 LAC ports of international interest are categorized into different coastal regions and tiers based on throughput sizes. Various metrics, including the Gini coefficient, Lorenz curve, Herfindahl-Hirschman Index (HHI), and Kendall Tau (τ), assess port hierarchy and related mobility since 2000. The observed shifts in the hierarchy and market structures, coupled with the fluctuating positions of critical ports, underscore the transition that LAC container ports dynamics experienced in the 21st century. Following a particularly dynamic and volatile evolution observed in the 2000s, the financial crisis of 2008/09 was a critical juncture leading to the transition of the LAC port dynamics from the ‘emerging’ to the ‘maturity’ phase. On the contrary, the pandemic (2019) has not affected the pre-existing hierarchy or the moderate market concentration that was already in progress. The LAC region comprises port sub-systems (coastal ranges) subjected to different tendencies towards (de)concentration, yet mobility in port rankings within each sub-system decreases. The study also reveals the coexistence of this transition with a structural transformation of port governance structures, i.e., granting of concessions of operations to third parties. In 20 of these ports and the above-average mobility of ports are operated by Global Terminal Operators (GTOs), and calls for further research on the (non) causality of these phenomena.

Constraining [formula omitted] gravity by dynamical system analysis

In this paper, we have studied the different phases of the evolution of the Universe through the dynamical system analysis. Here we explored the f(T,B,TG,BG) gravity, where T, B, TG, and BG respectively represent torsion, boundary term, teleparallel Gauss–Bonnet term, and Gauss–Bonnet boundary term. The transformation f(T,B,TG,BG)=−T+F(T,B,TG,BG) has been incorporated to get the deviation from the Teleparallel Equivalent of General Relativity. Two well motivated cosmological models (i) F(T,B,TG,BG)=f0TmBnTGk and (ii) F(T,B,TG,BG)=b0B+g0TGk have been studied. The critical points representing different phases of evolution have been studied in details. Further with the help of the eigenvalues and phase space diagrams, the stability and attractor nature of the accelerating solutions have been explored. The evolution plots have been analysed for the corresponding cosmology. The compatibility of the evolution plots has been checked with standard density parameters at present time.

High-pressure behavior of high-entropy A2B2O7 pyrochlore

A single high-entropy pyrochlore-type compound (A2B2O7) was successfully synthesized, incorporating 8 different rare-earth cations at the A site and 2 different metal cations at the B site in equiatomic amounts [(8A1/8)2(2B1/2)2O7]. Powders with a nominal composition of (La1/8Sm1/8Nd1/8Pr1/8Y1/8Gd1/8Dy1/8Yb1/8)2(Hf1/2Zr1/2)2O7 were fabricated by glycine nitrate procedure (GNP). The GNP process yielded powders with low crystallinity and after subsequent calcination, a well crystalline ceramic powders were formed. The phase evolution was initially analyzed using X-ray diffraction (XRD). In situ high-pressure X-ray diffraction was employed to investigate the structural stability and high-pressure behavior of the A2B2O7 pyrochlore up to 25.8 GPa. Theoretical investigations of the high-entropy pyrochlore systems were performed and showed good agreement with the experimentally obtained results.

Effect of processing parameters and carbon to metal ratio on microstructure and mechanical properties of (MoTaTiVW)Cx high entropy carbide produced by reactive spark plasma sintering

(MoTaTiVW)Cx high entropy ceramics with varying carbon to metal ratio in the range of 0.75-0.97 were synthesized by by reactive spark plasma sintering. The effect of ball milling time on particle size, phase evolution and carbon pick-up due to toluene decomposition were studied. Formation of single-phase high entropy carbide having face-centered cubic (FCC) crystal structure was confirmed by X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and Selected area diffraction pattern (SAED) analysis of the sintered compacts. Transmission Kikuchi Diffraction images revealed presence of equiaxed nature of the grains. Transmission electron microscopy images revealed the presence of an intergranular phase at grain boundaries and triple junctions. 3D-Atom Probe Tomography studies showed uniform distribution of elements within the grains with some segregation of impurity elements Fe and Co to the grain boundaries indicating minor contribution of liquid phase sintering to densification. The grain size of single-phase sintered compacts ranged between 1.69 ± 0.60 μm to 4.6 ± 1.0 μm. A low sintering temperature and higher milling time resulted in finer grain size The microhardness was found to increase with milling time and C/M ratio. The microhardness, Young’s modulus and indentation fracture toughness lied between 2221 HV0.1 to 2732 HV0.1, 370 GPa to 473 GPa, 3.6 MPa.m1/2 to 4.4 MPa.m1/2, respectively. The highest microhardness and indentation fracture toughness was found to be 2732 ± 80 HV0.1 and 4.4 MPa.m1/2 on par with reported literature for other high entropy carbides.

Flash sintering glass–ceramic treatment of Sr-contaminated soil waste

Effective disposal of radioactive waste is crucial for safe development of nuclear energy. In this study, flash sintering technology is used for the first time to quickly solidify simulated Sr-contaminated soil waste. The waste can be converted into a glass–ceramic phase by heating the waste at 1100 °C for 1 min during flash sintering. The phase evolution during flash sintering as a function of density and amorphous fraction was systematically investigated. Additionally, the microstructural evolution of the matrices and the leaching behavior of simulated waste elements (e.g., Sr) were evaluated. This study explores the feasibility of using flash sintering for treating radioactive contamination waste.

Cu-Al-Ni Nanocrystalline Compacts Obtained by Spark Plasma Sintering of Mechanically Alloyed Powders.

The aim of this work is to obtain Cu-13.5Al-4Ni alloy for use as shape memory alloy by Spark Plasma Sintering (SPS) of mechanically alloyed powder. The study investigates the structural and microstructural changes in terms of crystal parameters, crystallite sizes, and phases evolution during mechanical alloying and spark plasma sintering of Cu-13.5Al-4Ni powders. We obtained alloyed powders with a structure composed of α(Cu), AlNi intermetallic compound and small amounts of elemental Al through the mechanical alloying technique. After spark plasma sintering at 900 °C, the microstructure consists of an AlNi compound distributed at the edge of α(Cu) grains. The crystallite sizes of both, α(Cu) and AlNi are in nanoscale order after 16 h of milling (9 and 6.5 nm respectively). After sintering at 900 °C (in Ar atmosphere, without holding time), the crystallite sizes increase to 46 nm for α(Cu) and to 40 nm for AlNi compound. Also, the Cu-13.5Al-4Ni compacts achieve a final density after sintering at 900 °C of around 80% from the theoretical density.

Microstructure evolution and high-temperature oxidation behavior of low-carbon MgO-C refractories with TiB2 addition

Combining the advantages of both containing-B compounds and containing-Ti compounds, a new TiB2 addition is proposed in MgO-C refractories. In this paper, the high-temperature oxidation behavior of low-carbon MgO-C refractories with TiB2 addition was investigated, especially the effect of microstructure and phase evolution on the high-temperature oxidation behavior was discussed. The results show that in the materials, TiB2 preferentially reacts with oxygen, forming TiCxN1-x, Mg3(BO3)2 and Mg2TiO4 ceramic phases, and catalyzing the decomposition of phenolic resin to form bamboo-like nanotubes and carbon nanospheres to bond aggregates and fill pores. Meanwhile, TiB2 also promotes the formation of regenerated MgO compact zone, hindering the diffusion of oxygen into the materials to improve the oxidation resistance. Compared with the blank control specimen and the specimen with B4C addition, the oxidation resistance increased by 243.4 % and 79.2 %, respectively.

Variable Stars in M31 Stellar Clusters from the Panchromatic Hubble Andromeda Treasury

Variable stars in stellar clusters can offer key constraints on stellar evolution and pulsation models, utilizing estimates of host cluster properties to constrain stellar physical parameters. We present a catalog of 86 luminous (F814W < 19) variable stars in M31 clusters identified by mining the archival Panchromatic Hubble Andromeda Treasury (PHAT) survey using a combination of statistical analysis of sparse PHAT light curves and difference imaging. We determine the evolutionary phases and initial masses of these variable stars by matching them with theoretical isochrones generated using host cluster properties from the literature. We calculate the probability of PHAT photometry being blended due to the highly crowded nature of cluster environments for each cluster-variable star, using these probabilities to inform our level of confidence in the derived properties of each star. Our 86 cluster-variable stars have initial masses between 0.8 and 67 M ⊙. Their evolutionary phases span the main sequence, more evolved hydrogen- and helium-burning phases, and the post–asymptotic giant branch. We identify numerous candidate variable star types: RV Tauri variables, red supergiants, and slowly pulsating B-type supergiants, along with Wolf–Rayet stars, α Cygni and Mira variables, a classical Cepheid, and a possible superasymptotic giant. We characterize 12 cluster-variable stars at higher confidence based on their difference image quality and lower blending probability. Ours is the first systematic study of variable stars in extragalactic stellar clusters leveraging the superior resolution of the Hubble Space Telescope and demonstrating the unique power of stellar clusters in constraining the fundamental properties of variable stars.

(Re)mind the gap: A hiatus in star formation history unveiled by APOGEE DR17

Context. Analysis of several spectroscopic surveys indicates the presence of a bimodality between the disc stars in the abundance ratio space of [α/Fe] versus [Fe/H]. The two stellar groups are commonly referred to as the high-α and low-α sequences. Some models capable of reproducing such a bimodality invoke the presence of a hiatus in the star formation history in our Galaxy, whereas other models explain the two sequences by means of stellar migration. Aims. Our aim is to show that the existence of the gap in the star formation rate between high-α and low-α is evident in the stars of APOGEE DR17, if one plots [Fe/α] versus [α/H], confirming previous suggestions. We then try to interpret the data by means of detailed chemical models. Methods. We compare the APOGEE DR17 red giant stars with the predictions of a detailed chemical evolution model based on the two-infall paradigm, taking into account also the possible accretion of dwarf satellites. Results. The APOGEE DR17 abundance ratios [Fe/α] versus [α/H] exhibit a sharp increase in [Fe/α] at a nearly constant [α/H] (where α elements considered are Mg, Si, O) during the transition between the two disc phases. This observation strongly supports the hypothesis that a hiatus in star formation occurred during this evolutionary phase. Notably, the most pronounced growth in the [Fe/α] versus [α/H] relation is observed for oxygen, as this element is exclusively synthesised in core-collapse supernovae. The revised version of the two-infall chemical evolution model proposed in this study reproduces the APOGEE DR17 abundance ratios better than before. Particularly noteworthy is the model’s ability to predict the hiatus in the star formation between the two infalls of gas, which form the thick and thin disc, respectively, and thus generate abundance ratios compatible with APOGEE DR17 data. Conclusions. We show that the signature of a hiatus in the star formation is imprinted in the APOGEE DR17 abundance ratios. A chemical model predicting a pause in the star formation of a duration of roughly 3.5 Gyr, and in which the high-α disc starts forming from pre-enriched gas by a previous encounter with a dwarf galaxy, could well explain the observations

Microstructural evolution and deformation mechanisms of superplastic aluminium alloys: A review

Aluminium alloy is one of the earliest and most widely used superplastic materials. The objective of this work is to review the scientific advances in superplastic Al alloys. Particularly, the emphasis is placed on the microstructural evolution and deformation mechanisms of Al alloys during superplastic deformation. The evolution of grain structure, texture, secondary phase, and cavities during superplastic flow in typical superplastic Al alloys is discussed in detail. The quantitative evaluation of different deformation mechanisms based on the focus ion beam (FIB)-assisted surface study provides new insights into the superplasticity of Al alloys. The main features, such as grain boundary sliding, intragranular dislocation slip, and diffusion creep can be observed intuitively and analyzed quantitatively. This study provides some reference for the research of superplastic deformation mechanism and the development of superplastic Al alloys.

Facile growth of Cu2ZnSn(SSe)4 thin films with controlled phase and microstructure evolution from green ethanol-based molecular solutions

Facile growth of Cu2ZnSn(SSe)4 thin films with controlled phase and microstructure evolution from green ethanol-based molecular solutions

Nano and micro-structural complexity of nematic liquid crystal configurations

Of our interest are frustration-driven pattern generating mechanisms in systems which in bulk equilibrium display spatially homogeneous long-range orientational order in absence of perturbations. As testbed material, we select thermotropic nematic liquid crystals. In bulk, they exhibit weakly discontinuous order–disorder phase transformation on varying temperature where the ordered nematic phase features spatially uniform axial order along an arbitrary symmetry breaking direction. However, due to continuous symmetry breaking (CSB) the established order is extremely susceptible to various perturbations which are in real systems in general always present. We theoretically illustrate how diverse complex patterns could be excited. Particularly intriguing configurations could appear if topological defects are present that could be generated via CSB. Our analysis is based on a relatively simple Lebwohl-Lasher-type model in which we could get analytical insight into phenomena of our interest. Using it we illustrate history dependent early stage isotropic-nematic phase evolution and final patterns in presence of “impurities” (e.g., nanoparticles). We show how characteristic effective interaction characteristics predict qualitatively different emerging patterns. Our analysis is based on CSB which is ubiquitous in nature. Consequently, demonstrated mechanisms are expected to manifest also in other condensed matter systems whose ordered phase is formed via CSB. We illustrate how kinetics and impurities could impact key structural properties of the systems of our interest.

An ultra-durable ZIT glass-ceramic composite for immobilization of radioactive mixed lanthanide oxides

Zinc Titanate (ZIT) glass-ceramic composite is a potential candidate waste form for immobilizing radioactive lanthanide oxides due to its relatively high lanthanide embedding capacity and low reaction temperature. However, the composition of lanthanide oxides after electrolytic refining is very complex and the immobilization mechanism of lanthanide oxides by ZIT composite is not clear. Herein, we prepared ZIT-PrEu glass-ceramic waste forms by a solid-phase sintering method at 1200 °C for 4 h using mixed lanthanide oxides of Pr6O11 and Eu2O3 simulated as radioactive waste. The XRD and SEM results show that different mixed lanthanide oxide ratios have very little effect on the composition and microstructure of ZIT-PrEu waste forms with different waste embedding rates. With the increase of waste embedding rate, the density of the ZIT-PrEu glass-ceramic waste forms with different mixed lanthanide oxide ratios first increases and then decreases. When the embedding rate increases to 25 wt.%, the density of ZIT-PrEu waste forms with different mixed lanthanide oxide ratios reaches a maximum. The ZIT-PrEu glass-ceramic waste forms embedded with 25 wt.% waste exhibit excellent chemical durability, and the leaching rates of Pr ion and Eu ion are only 10-6 - 10-7 g·m-2·d-1 after 28 days at 90 °C. Moreover, the phase evolution of the ZIT composites immobilizing lanthanide oxides at different temperatures is revealed by XRD and FT-IR measurements. The lanthanides (Ln) are mainly present in the form of LnPO4 monazite phases.

Microwave dielectric properties and phase evolution of Zn-excess Mg0.95Zn0.05+xTiO3+x (x = 0–0.1) ceramics

Microwave dielectric properties and phase evolution of Zn-excess Mg0.95Zn0.05+xTiO3+x (x = 0–0.1) ceramics

Effect of boron on phase, nanostructure, and thermal stability of polycarbosilane-derived SiC ceramics

The current study explores the formation, evolution, and thermal stability of polymer-derived SiBC at high temperatures. It focuses on the phase evolution of SiBC ceramics derived from the doping of boron in an allyl-containing polycarbosilane preceramic polymer after 1200 °C to 1600 °C pyrolysis. Different SiBC ceramic monoliths have been obtained. Boron is incorporated into the carbon phase at lower pyrolysis temperatures but into both the carbon phase and the SiC lattice structure at high pyrolysis temperatures. B–C bonds form in SiBC and hinder the growth of graphitic carbon and SiC. Boron improves the densification and thermal stability of the SiBC ceramics. This work provides an improved understanding of boron effects in polymer-derived SiC nanostructures at high temperatures.

CHARA Near-infrared Imaging of the Yellow Hypergiant Star ρ Cassiopeiae: Convection Cells and Circumstellar Envelope

Massive evolved stars such as red supergiants and hypergiants are potential progenitors of Type II supernovae, and they are known for ejecting substantial amounts of matter, up to half their initial mass, during their final evolutionary phases. The rate and mechanism of this mass loss play a crucial role in determining their ultimate fate and the likelihood of their progression to supernovae. However, the exact mechanisms driving this mass ejection have long been a subject of research. Recent observations, such as the Great Dimming of Betelgeuse, have suggested that the activity of large convective cells, combined with pulsation, could be a plausible explanation for such mass-loss events. In this context, we conducted interferometric observations of the famous yellow hypergiant, ρ Cassiopeiae using the CHARA Array in H- and K-band wavelengths. ρ Cas is well known for its recurrent eruptions, characterized by periods of visual dimming (∼1.5–2 mag) followed by recovery. From our observations, we derived the diameter of the limb-darkened disk and found that this star has a radius of 1.04 ± 0.01 mas, or 564–700 R ⊙. We performed image reconstructions with three different image reconstruction software packages, and they unveiled the presence of giant hot and cold spots on the stellar surface. We interpret these prominent hot spots as giant convection cells, suggesting a possible connection to mass ejections from the star’s envelope. Furthermore, we detected spectral CO emission lines in the K band (λ = 2.31–2.38 μm), and the image reconstructions in these spectral lines revealed an extended circumstellar envelope with a radius of 1.45 ± 0.10 mas.

Between Rejecting and Adventuring: The Spatial Analysis of the Evolutionary Phases of Egyptians’ Irregular Migration to Europe

Between Rejecting and Adventuring: The Spatial Analysis of the Evolutionary Phases of Egyptians’ Irregular Migration to Europe

Magnetic Fields in Massive Star-forming Regions (MagMaR). IV. Tracing the Magnetic Fields in the O-type Protostellar System IRAS 16547–4247

The formation of the massive stars, and in particular, the role that the magnetic fields play in their early evolutionary phase is still far from being completely understood. Here, we present the Atacama Large Millimeter/submillimeter Array 1.2 mm full polarized continuum and H13CO+(3−2), CS(5−4), and HN13C(3−2) line observations with a high angular resolution (∼0.″4 or 1100 au). In the 1.2 mm continuum emission, we reveal a dusty envelope surrounding the massive protostars, IRAS16547-E and IRAS16547-W, with dimensions of ∼10,000 au. This envelope has a biconical structure likely carved by the powerful thermal radio jet present in region. The magnetic field vectors follow very well the biconical envelope. The polarization fraction is ∼2.0% in this region. Some of these vectors seem to converge to IRAS 16547-E and IRAS 16547-W, the most massive protostars. Moreover, the velocity fields revealed from the spectral lines H13CO+(3−2) and HN13C(3−2) show velocity gradients with a good correspondence with the magnetic fields, which maybe are tracing the cavities of molecular outflows or maybe infalling in some parts. We derived a magnetic field strength in some filamentary regions that goes from 2 to 6.1 mG. We also find that the CS(5−4) molecular line emission reveals multiple outflow cavities or bow shocks with different orientations, some of which seem to follow the NW–SE radio thermal jet.

Growing evolutional deep echo state network

Deep echo state network (Deep ESN) is a powerful method for time-series prediction, but developing the optimal structure of Deep ESN remains challenging. A novel generative framework, growing evolutional Deep ESN (GE Deep ESN) is proposed, where networks are generated through alternating growth and evolution. A model compression method is implemented during the evolution phase to optimize the inner structure of the reservoirs, and to automatically determine reservoir size. A simple termination criterion of growth is introduced to determine network depth. The feasibility and superiority of GE Deep ESN were validated experimentally with two benchmark prediction tasks. For real-time trajectory prediction in photoelectric tracking systems, an iterative learning model based on GE Deep ESN is proposed, the real time prediction result showed that network evolution enhances the model’s suitability for this task, and improves prediction precision.