Mechanism Of Phase Transition Research Articles

Atomistic phase transition mechanism of zero-strain electrode material: Transmission electron microscopy investigation of Li4Ti5O12 spinel lattice upon lithiation

The lithiation mechanism of electrode materials is important for understanding the basic reactions in Li-ion batteries. In particular, zero-strain materials have garnered interest owing to their stable charge–discharge performances. In this study, we investigated the atomistic phase transition mechanism of spinel Li4Ti5O12, a well-known zero-strain material, using high-resolution transmission electron microscopy. A single-crystalline Li4Ti5O12 (100) specimen was prepared and observed in situ at a lattice resolution under electron-beam-assisted lithiation. The lattice fringes originating from the Li plane of the spinel crystal were anisotropically altered during phase transition, suggesting the asymmetrical site shifting of Li atoms during lithiation. This spontaneous symmetry-breaking mechanism for the phase transition is considered essential for the lithiation of spinel lattice.

Replica symmetry breaking in 1D Rayleigh scattering system: theory and validations

Spin glass theory, as a paradigm for describing disordered magnetic systems, constitutes a prominent subject of study within statistical physics. Replica symmetry breaking (RSB), as one of the pivotal concepts for the understanding of spin glass theory, means that under identical conditions, disordered systems can yield distinct states with nontrivial correlations. Random fiber laser (RFL) based on Rayleigh scattering (RS) is a complex disordered system, owing to the disorder and stochasticity of RS. In this work, for the first time, a precise theoretical model is elaborated for studying the photonic phase transition via the platform of RS-based RFL, in which we clearly reveal that, apart from the pump power, the photon phase variation in RFL is also an analogy to the temperature term in spin-glass phase transition, leading to a novel insight into the intrinsic mechanisms of photonic phase transition. In addition, based on this model and real-time high-fidelity detection spectral evolution, we theoretically predict and experimentally observe the mode-asymmetric characteristics of photonic phase transition in RS-based RFL. This finding contributes to a deeper understanding of the photonic RSB regime and the dynamics of RS-based RFL.

Reactive Synthesis for Porous (Mo2/3Y1/3)2AlC Ceramics through Mo, Y, Al and Graphite Powders.

Through an activation reaction sintering method, porous (Mo2/3Y1/3)2AlC ceramics were prepared by Mo, Y, Al, and graphite powders as raw materials. The phase composition, microstructure, element distribution, and pore structure characteristics were comprehensively studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Archimedes method, and bubble point method. A detailed investigation was conducted on the influence of sintering temperature on the phase composition. Possible routes of phase transition and pore formation mechanisms during the sintering process were provided. The experimental results reveal that at 650-850 °C, transition metals react with aluminum, forming aluminum-containing intermetallics and a small amount of carbides. At 850-1250 °C, transition metals collaborate with graphite, producing transition metal carbides. Then, at 1250-1450 °C, these aluminum intermetallics interact with transition metal carbides and remaining unreacted Y, Al, and C, yielding the final product (Mo2/3Y1/3) 2AlC. Simultaneously, the pore structure alters correspondingly with the solid-phase reaction at different reaction temperatures.

A search for pressure-induced phase transition in the layered perovskite-like Pr2Ti2O7

In our study, we present comprehensive findings on the structural properties of Pr2Ti2O7 across a broad pressure range of 0-30GPa. Neutron diffraction experiments, conducted under ambient conditions, offer crucial structural insights into the initial monoclinic phase with the P21 space group. As pressure increased, a significant phase transition to the monoclinic P21/m phase occurred at 13.8GPa. Structural data analysis from X-ray diffraction highlights the essence of this transition, identifying it as the tilting of Ti-O6 octahedra. High-pressure Raman spectroscopy data unequivocally confirms the phase transition, detecting anomalies in the baric dependencies of some vibration modes of Pr2Ti2O7 and the emergence of new modes in the Raman spectra within the pressure region associated with the phase transition. The analysis of these novel vibration modes points to alterations in the Ti-O6 octahedra, emphasizing the pivotal role played by Ti4+ and O2- ions in the mechanism of the pressure-driven phase transition.

Electrical analysis and molecular dynamics of anion in ferroelastic [(CH3)4P]2CoBr4 crystal near high-temperature phase transitions

The recent technological advances require an aligned innovation in the materials used for the construction of electronic devices. Hybrid materials play a important role in the optoelectronic applications because they combine both the organic and inorganic components. To this end, the [(CH3)4P]2CoBr4 compound was successfully synthesized using the slow evaporation solution growth approach at room temperature. In-depth research has been conducted on the structural, morphological, vibrationnal and electrical characteristics. The [(CH3)4P]2CoBr4 compound crystallises in the monclinic system with P121/C1 space group. The examination of SEM images reveals that the majority of grains have an average size of around 4 μm with irregularly shaped and non-spherical particles. The measured Raman spectra demonstrate the coexistence of two transition phases located at 373 K and 428 K. In fact, these observations suggest that the anionic components play a significant role in influencing the phase transitions mechanism. Analysis of the complex impedance spectra reveals that the electrical characteristics of the material is strongly dependent on both frequency and temperature. That indicates the existence of a relaxation phenomenon and of a semiconductor-type behavior. One single semicircle is detectable in the Nyquist plots of the complex impedance spectra, which can be satisfactorily fitted with a combination of R//C//CPE elements assigned to the bulk response. Therefore, we can conclude from this behavior that the sample is electrically homogeneous. The dependency of s(T) on temperature also shows that the correlated barrier hopping and the non-overlapping small polar on tunneling model are the responsible mechanisms for the AC conduction in [(CH3)4P]2CoBr4.

High pressure melt line of nickel using a generalized embedded atomic method potential

As the second most abundant metal in the Earth's core, nickel plays an important role in determining the structure and temperature of the Earth's core. Yet, the melt line of Ni at pressures corresponding to the Earth's core has not been explored in the literature. Many previous experimental and simulation efforts have reported the melting point of Ni at pressures below 100 GPa, but there exist large discrepancies, most of which have persisted due to various experimental and simulation bottlenecks in handling extreme pressure and temperature conditions. We adopted the generalized embedded atom method, which overcomes the limitations of existing interatomic potentials, to probe phase stability and phase boundaries of Ni at pressures between 50 and 500 GPa. The potential was validated by comparing the cold curves, phonon dispersion curves, and enthalpies of fusion with ab initio density functional theory calculations. Our analysis shows that face centered cubic (FCC) is stable, and the hexagonal close packed (HCP) and body centered cubic (BCC) phases are metastable close to the melt line. Melting temperatures at different pressures were obtained from two-phase co-existence simulations and take the following functional form: Tm=1969.23+19.15P−0.012P2. In contrast to iron, differences between the melting points of the stable and metastable phases of Ni are less than 250 K at 300 GPa, and the difference in melting points of the metastable BCC and HCP phases changes sign at 500 GPa, which implies that the phase transition mechanisms during solidification can be very complex.

Molecular orbital breaking in photo-mediated organosilicon Schiff base ferroelectric crystals

Ferroelectric materials, whose electrical polarization can be switched under external stimuli, have been widely used in sensors, data storage, and energy conversion. Molecular orbital breaking can result in switchable structural and physical bistability in ferroelectric materials as traditional spatial symmetry breaking does. Differently, molecular orbital breaking interprets the phase transition mechanism from the perspective of electronics and sheds new light on manipulating the physical properties of ferroelectrics. Here, we synthesize a pair of organosilicon Schiff base ferroelectric crystals, (R)- and (S)-N-(3,5-di-tert-butylbenzylidene)-1-((triphenylsilyl)oxy)ethanamine, which show optically controlled phase transition accompanying the molecular orbital breaking. The molecular orbital breaking is manifested as the breaking and reformation of covalent bonds during the phase transition process, that is, the conversion between C = N and C–O in the enol form and C–N and C = O in the keto form. This process brings about photo-mediated bistability with multiple physical channels such as dielectric, second-harmonic generation, and ferroelectric polarization. This work further explores this newly developed mechanism of ferroelectric phase transition and highlights the significance of photo-mediated ferroelectric materials for photo-controlled smart devices and bio-sensors.

The aggregation structure and rheological properties of catanionic surfactant mixtures and potential applications in fracturing fluids

Clean fracturing fluids are widely used in reservoir stimulation and increasing production due to their characteristics of simple preparation, no residue, easy flowback, and low damage. At present, clean fracturing fluids are mainly prepared by cationic surfactants as main agent and inorganic or organic salts as additives, which can lead to unavoidable losses of cationic surfactants due to their adsorption in the formation. Anionic-cationic surfactants composite system can not only compensate for the shortcomings of a single surfactant system, but also improve the reservoir adaptability of the surfactant system. In this paper, a clean fracturing fluid was prepared with long-chain anionic surfactant, Sodium erucate (NaOEr), as main agent and a series of cationic surfactants with different as additive. Then, the aggregation behavior of mixed system was determined by visual appearance, rheology experiments, differential scanning calorimetry and cryogenic transmission electron microscopy. The phase transition mechanism induced by temperature was proposed, and the performance of the mixed system as a fracturing fluid was evaluated. The results showed the mixed systems could self-assemble into wormlike micelles when the length of hydrophobic carbon chains of cationic surfactant was 6 and 8. Increasing the length of the hydrophobic carbon chain could enhance the electrostatic effect, leading to precipitation in the mixed system. When the ratio of cationic surfactant was between 0.5 and 0.6 and the concentration was between 68 and 175 mmol∙L-1, the mixed systems tended to form three-dimensional structures by entangling and stacking wormlike micelles, showing high viscoelasticity and viscosity. The aggregation structure of the mixed system transformed from vesicles to wormlike micelles at 46.8 °C, which is attributed to the transition of carbon chains of NaOEr from non-flexible to flexible. Finally, the mixed system as a fracturing fluid has good shear resistance and temperature resistance. The viscosity of NaOEr/HTAB can reach above 50 mPa⋅s after sheared for 60 min at the conditions of 170 s−1 and 80 °C. This study provides an anionic clean fracturing fluid and broaden the application of viscoelastic surfactants in oilfield development.

High-Voltage Spinel Cathode Materials: Navigating the Structural Evolution for Lithium-Ion Batteries.

High-voltage LiNi0.5Mn1.5O4 (LNMO) spinel oxides are highly promising cobalt-free cathode materials to cater to the surging demand for lithium-ion batteries (LIBs). However, commercial application of LNMOs is still challenging despite decades of research. To address the challenge, the understanding of their crystallography and structural evolutions during synthesis and electrochemical operation is critical. This review aims to illustrate and to update the fundamentals of crystallography, phase transition mechanisms, and electrochemical behaviors of LNMOs. First, the research history of LNMO and its development into a LIB cathode material is outlined. Then the structural basics of LNMOs including the classic and updated views of the crystal polymorphism, interconversion between the polymorphs, and structure-composition relationship is reviewed. Afterward, the phase transition mechanisms of LNMOs that connect structural and electrochemical properties are comprehensively discussed from fundamental thermodynamics to operando dynamics at intra- and inter-particle levels. In addition, phase evolutions during overlithiation as well as thermal-/electrochemical-driven phase transformations of LNMOs are also discussed. Finally, recommendations are offered for the further development of LNMOs as well as other complex materials to unlock their full potential for future sustainable and powerful batteries.

Order–disorder phase transitions in front of the exit during human crowd evacuations

Human crowds often exhibit collective behaviors through self-organization, such as orderly queueing and disordered congestion at exits. Understanding the dynamic mechanisms behind these behaviors is crucial for pedestrian traffic management and the handling of mass crowds. Although current models and experiments have provided profound insights into ordered and disordered pedestrian groups separately, the transition mechanism from order to disorder within pedestrian crowds in front of exits remains unclear. In this study, a pedestrian queueing evacuation experiment was presented to demonstrate the phase transition process of pedestrian movement states as urgency levels in the environment change. We discovered the migration pattern of the phase transition point under evacuation control and identified different propagation modes of pedestrian velocity waves. Furthermore, a pedestrian motion model based on experimental data and observed phenomena was established. This model not only replicates the observed phenomena and regularities from the experiments but also reveals the quantitative phase transition mechanism of pedestrian movement under the influence of a single factor (i.e., urgency level or queueing ratio). Our findings hold significant implications for various domains, including pedestrian management, traffic control, and pedestrian dynamics.

Powerful UAV manipulation via bioinspired self-adaptive soft self-contained gripper.

Existing grippers for unmanned aerial vehicle (UAV) manipulation have persistent challenges, highlighting a need for grippers that are soft, self-adaptive, self-contained, easy to control, and lightweight. Inspired by tendril plants, we propose a class of soft grippers that are voltage driven and based on winding deformation for self-adaptive grasping. We design two types of U-shaped soft eccentric circular tube actuators (UCTAs) and propose using the liquid-gas phase-transition mechanism to actuate UCTAs. Two types of UCTAs are separately cross-arranged to construct two types of soft grippers, forming self-contained systems that can be directly driven by voltage. One gripper inspired by tendril climbers can be used for delicate grasping, and the other gripper inspired by hook climbers can be used for strong grasping. These grippers are ideal for deployment in UAVs because of their self-adaptability, ease of control, and light weight, paving the way for UAVs to achieve powerful manipulation with low positioning accuracy, no complex grasping planning, self-adaptability, and multiple environments.

Mammalian IRE1α dynamically and functionally coalesces with stress granules.

Upon endoplasmic reticulum (ER) stress, activation of the ER-resident transmembrane protein kinase/endoribonuclease inositol-requiring enzyme 1 (IRE1) initiates a key branch of the unfolded protein response (UPR) through unconventional splicing generation of the transcription factor X-box-binding protein 1 (XBP1s). Activated IRE1 can form large clusters/foci, whose exact dynamic architectures and functional properties remain largely elusive. Here we report that, in mammalian cells, formation of IRE1α clusters is an ER membrane-bound phase separation event that is coupled to the assembly of stress granules (SGs). In response to different stressors, IRE1α clusters are dynamically tethered to SGs at the ER. The cytosolic linker portion of IRE1α possesses intrinsically disordered regions and is essential for its condensation with SGs. Furthermore, disruption of SG assembly abolishes IRE1α clustering and compromises XBP1 mRNA splicing, and such IRE1α-SG coalescence engenders enrichment of the biochemical components of the pro-survival IRE1α-XBP1 pathway during ER stress. Our findings unravel a phase transition mechanism for the spatiotemporal assembly of IRE1α-SG condensates to establish a more efficient IRE1α machinery, thus enabling higher stress-handling capacity.

Recent advances of phase transition and ferroelectric device in two-dimensional In2Se3

The coupling of ferroelectric, photoelectric, semiconducting, and phase transition properties make two-dimensional (2D) In2Se3 a material platform with great application potential in the phase change memory, intelligent sensing, and in-memory computing devices. However, at present, there are unclear phase transition mechanisms and ferroelectric dynamics in 2D In2Se3, which seriously hinder the development of device applications. In this review, we mainly highlight the phase transition mechanisms and ferroelectric devices of In2Se3 beginning with the history of bulk In2Se3 and of 2D In2Se3. The phase transition relations of the four In2Se3 phases, including α-, β-, β′-, and γ-phases, under various driving forces, are summarized. The different driving forces, including temperature, laser, electric-field, vacancy, doping, and strain, are introduced and discussed. Moreover, the phase-control growth of 2D In2Se3 films and their novel ferroelectric device applications are demonstrated. Finally, a perspective on future research directions of 2D In2Se3 is provided.

Cross-scale deciphering thermal failure process of Ni-rich layered cathode

Ni-rich LiNixCoyMn1-x-yO2 (NCM) layered oxides are low-cost high-energy density cathode materials, but plagued by its poor thermal stability incurred safety concerns. The thermal failure process of the layered cathode is accompanied by heat generation and oxygen release, which drives the battery into thermal runaway (TR). Aiming to fully understand the TR process and the structure evolution, this work applies diverse characterization techniques onto a polycrystalline Ni-rich layered cathode (LiNi0.83Mn0.05Co0.12O2 (PCN83)) to comprehensively investigate its thermal failure process at multiple scales. From macro level, we validate that it is the cathode thermal failure that drives the battery from the heat accumulation stage into TR in adiabatic conditions. From micro level, transmission electron microscopy (TEM) verifies that the thermal failure of PCN83 starts from 150 °C, which is much lower than the TR temperature measured from macro level tests. We reveal that the PCN83 cathode experiences sequential phase transitions before the TR, where the phase transition mechanism is illustrated from the atomic scale and the pore evolution process is unraveled. In situ heating TEM further reveals that thermal failure is preferentially initiated from grain boundaries and defect regions. These findings provide an in-depth understanding of the whole thermal failure process of NMC-based layered cathode materials and sheds new lights on the rational design of Ni-rich cathode materials with improved thermal safety.

A facile DNA coacervate platform for engineering wetting, engulfment, fusion and transient behavior.

Biomolecular coacervates are emerging models to understand biological systems and important building blocks for designer applications. DNA can be used to build up programmable coacervates, but often the processes and building blocks to make those are only available to specialists. Here, we report a simple approach for the formation of dynamic, multivalency-driven coacervates using long single-stranded DNA homopolymer in combination with a series of palindromic binders to serve as a synthetic coacervate droplet. We reveal details on how the length and sequence of the multivalent binders influence coacervate formation, how to introduce switching and autonomous behavior in reaction circuits, as well as how to engineer wetting, engulfment and fusion in multi-coacervate system. Our simple-to-use model DNA coacervates enhance the understanding of coacervate dynamics, fusion, phase transition mechanisms, and wetting behavior between coacervates, forming a solid foundation for the development of innovative synthetic and programmable coacervates for fundamental studies and applications.

A variable-representation discrete artificial bee colony algorithm for a constrained hybrid flow shop

In the realm of hybrid flow shop environments, existing literature predominantly overlooks a practical scenario that jobs with different constraints often need to be simultaneously processed. This article addresses a constrained hybrid flow shop scheduling problem (CHFSP) in which certain jobs are bound by a common deadline while other jobs are not. We first propose constructive heuristics to generate initial solutions, completely based on the characteristics of the problem. Additionally, we present a variable-representation discrete artificial bee colony algorithm (VRDABC). The algorithm introduces a novel variable solution representation along with a tailored decoding method, allowing an extensive exploration of the solution space while maintaining a remarkable search speed. By leveraging the distinctive solution representation, we design an insertion operation, a multi-phase evolutionary process, and an efficient phase-transition mechanism, thereby enabling the VRDABC to successfully address this problem. Experimental validations, including algorithmic components analysis and algorithmic comparison, confirm the effectiveness and potential of our approach in producing high-quality solutions. Through the theoretical explanation and experimental analysis, the VRDABC presents an influential contribution to the constrained hybrid flow shop scheduling problem.

Thermosensitive injectable polysaccharide-based hydrogels: Gelation mechanisms, synthetic strategies, biomedical applications, and challenges

In recent years, thermosensitive polysaccharide-based injectable hydrogels have gained increasing attention in biomedical applications, including wound healing, drug delivery, and cartilage repair. These hydrogels have favorable biocompatibility, biodegradability, and tunable physical and chemical properties. Thermosensitive polysaccharide-based injectable hydrogels are a class of intelligent soft matter material. They can undergo a reversible liquid-solid transition when exposed to temperature stimuli. Therefore, their precursor solutions can be accurately inserted into target sites with irregular geometries in a minimally invasive way and then transformed into gels in situ by the organism’s temperature stimulation to deliver biologically active molecules. This review summarizes the recent developments of thermosensitive injectable polysaccharide-based hydrogels. The focus is on the mechanism of sol-gel phase transition, as well as the design and preparation of thermosensitive polysaccharides and their applications in biomedical fields. In addition, the outlook of the challenges in biomedical applications is provided at the end of the paper.

Combined study of phase transitions in the P2-type NaXNi1/3Mn2/3O2 cathode material: experimental, ab-initio and multiphase-field results

The research of new electrode materials such as sodium intercalation compounds is key to meet the challenges of future demands of sustainable energy storage. For these batteries, the intercalation behavior on the micro-scale is governed by a complex interplay of chemical, electrical and mechanical forces strongly influencing the overall cell performance. The multiphase-field method is a suitable tool to study these multi-physics and bridge the scale from ab-initio methods to the cell level. In this work, we follow a combined approach of experiments, density functional theory (DFT) calculations and multiphase-field simulations to predict thermodynamic and kinetic properties for the P2-type NaXNi1/3Mn2/3O2 sodium-ion cathode material. Experimentally, we obtain the thermodynamic potential and diffusion coefficients at various sodium contents using electrochemical techniques and discuss limitations of the experimentally applied methods. DFT is used to identify stable phases by calculating an energy hull curve. Then, the influence of long-range dispersion interactions and the exchange-correlation functional on the voltage curve is investigated by comparison with experimental results. Finally, multiphase-field simulations are performed based on inputs from experiments and DFT. The fitting of phase-specific chemical free energies from DFT calculations and experimental data is discussed. Our results highlight the thermodynamic consistency of all three approaches close to thermodynamic equilibrium. Furthermore, the phase-field method accurately describes the kinetics of the system including multiple phase transitions, by which we unravel the mechanism of the P2-O2 phase transition in a single crystal under the influence of intercalation reaction, bulk diffusion and elastic deformation. The model is able to predict the kinetic capacity loss depending on charging rate in agreement with C-rate experiments.

Optogenetic control of mRNA condensation reveals an intimate link between condensate material properties and functions

Biomolecular condensates, often assembled through phase transition mechanisms, play key roles in organizing diverse cellular activities. The material properties of condensates, ranging from liquid droplets to solid-like glasses or gels, are key features impacting the way resident components associate with one another. However, it remains unclear whether and how different material properties would influence specific cellular functions of condensates. Here, we combine optogenetic control of phase separation with single-molecule mRNA imaging to study relations between phase behaviors and functional performance of condensates. Using light-activated condensation, we show that sequestering target mRNAs into condensates causes translation inhibition. Orthogonal mRNA imaging reveals highly transient nature of interactions between individual mRNAs and condensates. Tuning condensate composition and material property towards more solid-like states leads to stronger translational repression, concomitant with a decrease in molecular mobility. We further demonstrate that β-actin mRNA sequestration in neurons suppresses spine enlargement during chemically induced long-term potentiation. Our work highlights how the material properties of condensates can modulate functions, a mechanism that may play a role in fine-tuning the output of condensate-driven cellular activities.

Three-Step Ferroelastic Transitions from Hexagonal to Triclinic Phases in a Hybrid Perovskite: (1-Fluoromethyl-1-methylpyrrolidine)[CdCl3

Hybrid ferroelastic crystals have emerged as a hot research topic in recent years owing to their prospective applications in piezoelectric sensors, mechanical switches, and optoelectronic devices. Nevertheless, most of the documented materials exhibit one-step or two-step ferroelastic phase transition(s), and those with multistep ferroelastic transitions are extremely scarce. We present a new hexagonal molecular perovskite based on a fluoro-substituted flexible cyclic ammonium cation, (1-fluoromethyl-1-methylpyrrolidine)[CdCl3] (1), undergoing unusual three-step ferroelastic phase transitions from hexagonal paraelastic phase to orthorhombic, monoclinic, and triclinic ferroelastic phases at 388, 376, and 311 K, respectively, with Aizu notation of 6/mmmFmmm, mmmF2/m, and 2/mF-1, featuring spontaneous strain of 0.002, 0.023, and 0.110, respectively. Furthermore, variable-temperature single-crystal diffraction reveals that the phase-transition mechanism in 1 principally originates from intriguing dynamic change of organic cations and synchronous displacement of inorganic chains. This scarce instance of multistep hybrid ferroelastic provides important clues for finding advanced ferroelastic materials.