Anisotropic Phase Research Articles

A novel photovoltaic-thermoelectric hybrid system with an anisotropic shape-stale phase change composites

Photovoltaic (PV) power generation technology is currently one of the most effective ways in solar energy utilization, while current PV panels are facing a serious issue of electrical efficiency reduction and potential structural damage caused by the accumulated heat during operation. To solve this issue, we proposed a novel hybrid system containing PV cell, thermoelectric generation (TEG) module, and phase change composite (PCC), which can achieve a power enhancement of 29.8 % compared with individual PV cell. The fabricated chitosan-based PCC has a high anisotropy degree of 4.10 and melting enthalpy of 133.2 kJ·kg−1, which promote the effective heat transport and storage between PV cell and TEG module, and the excellent mechanical strength and thermal stability ensures its long-term endurance. Owing to excellent thermal properties of the PCC, not only the power of PV cell is increased by 55.9 mW, but the TEG module also continuously outputs 4.1 mW of power. Besides, the hybrid system can produce 5.185 kW·h·m−2 electricity per day in the actual environment. Looking ahead, the integration of advanced materials and hybrid systems like the PV + PCC + TEG approach holds great promise for further enhancing solar energy efficiency and sustainability in real-world applications.

Entanglement Smectic and Stripe Order

Spontaneous symmetry breaking and more recently entanglement are two cornerstones of quantum matter. We introduce the notion of anisotropic entanglement ordered phases, where the spatial profile of spin-pseudospin entanglement spontaneously lowers the fourfold rotational symmetry of the underlying crystal to a twofold one, while the charge density retains the full symmetry. The resulting phases, which we term and , exhibit a rich Goldstone mode spectrum and a set of phase transitions as a function of underlying anisotropies. We discuss experimental consequences of such anisotropic entanglement phases distinguishing them from more conventional charge or spin stripes. Our discussion of this interplay between entanglement and spontaneous symmetry breaking focuses on multicomponent quantum Hall systems realizing textured Wigner crystals, as may occur in graphene or possibly also in moiré systems, highlighting the rich landscape and properties of possible entanglement ordered phases. Published by the American Physical Society 2024

Revisiting Rare Earth Permanent Magnetic Alloys of Nd-Fe-C

Nd-Fe-C alloys have been reported as hard magnetic materials with a potential higher coercivity than Nd-Fe-B alloys. However, it has been seldom studied since its intrinsic properties were investigated in the last century. Here, we revisited the structure, phase precipitation and magnetic properties of rapidly quenched ternary Nd-Fe-C alloys for further understanding their composition-microstructure-property relationships. The Nd10+xFe84−xC6 (x = −2, 0, 2, 3, 4, 5) alloys with various compositions were prepared by melt spinning. The results show that the hard magnetic Nd2Fe14C phase can be hardly formed in the as-spun alloys. Instead, the alloys are composed of soft magnetic α-Fe phase and planar anisotropic Nd2Fe17Cx phase. After annealing above 650 °C, the Nd2Fe14C phase is precipitated by the peritectoid reaction. All optimally annealed alloys contain Nd2Fe14C and Nd2Fe17Cx phases, while the presence and content of α-Fe phase are determined by the alloy composition. The crystallization degree of the as-spun alloys has an effect on their magnetic properties after annealing. After the annealing treatment, partly crystallized as-spun alloys exhibit better magnetic properties than the amorphous alloys. The intrinsic coercivity Hcj = 847 kA/m, remanence Jr = 0.69 T, and maximum energy product (BH)max = 64.3 kJ/m3 were obtained in the Nd14Fe80C6 alloy annealed at 725 °C. The formation of the Nd2Fe14C and Nd2Fe17Cx phases with the Nd2O3 phase precipitated at the triangular grain boundaries is responsible for its relatively good properties. Although the magnetic properties of Nd-Fe-C alloys obtained in this work are inferior to those of Nd-Fe-B, the present results help us to further understand the magnetic behavior of Nd-Fe-C alloys.

Fracture modeling in composite structures containing orthotropic materials by incorporating strain orthogonal decompositions into phase-field method of interfacial damage

PurposeThe phase-field method of interfacial damage is used to simulate the damage in composite structures containing the brittle orthotropic materials and their interface.Design/methodology/approachIn the brittle fracture modeling, the strain tensor is decomposed into positive and negative parts characterizing tension and compression behaviors. By requiring an elastic energy preserving transformation involving the elastic stiffness tensor, these two strain parts must satisfy the orthogonality condition in the sense that the elastic stiffness tensor responds as a metric. However, most of the recent phase-field methods for brittle fracture do not verify this orthogonality condition. Additionally, to describe the damage in structures with anisotropic phases, recent studies have used multiple phase-field variables, with each preferential orientation represented by a phase-field variable to describe the bulk damage of component materials. This approach increases the complexity of simulation procedure. These disadvantages motivate the present study aimed at enhancing the simulation method.FindingsThe present study improves the phase-field method of interfacial damage by (1) incorporating the strain orthogonality condition into the phase-field method; (2) using only one phase-field variable instead of multiple phase-field variables to simulate damage in component orthotropic phases; and (3) investigating the interaction between interfacial damage and bulk damage as well as the effect of orientation tensor of preferential orientation in each orthotropic phase and the interfacial parameters on crack branching in composite structures.Originality/valueThrough several simulation examples, the present simulation method is proven to be accurate, effective, and helps the simulation process simpler than previous relevant methods.

Resistive anisotropy in the charge density wave phase of Kagome superconductor CsV3Sb5 thin films

Resistive anisotropy in the charge density wave phase of Kagome superconductor CsV3Sb5 thin films

Holographic description of an anisotropic Dirac semimetal

Holographic quantum matter exploits the AdS/CFT correspondence to study systems in condensed matter physics. An example of these systems are strongly correlated semimetals, which feature a rich phase diagram structure. In this work, we present a holographic model for a Dirac semimetal in 2 + 1 dimensions that features a topological phase transition. Our construction relies on deforming a relativistic UV fixed point with some relevant operators that explicitly break rotations and some internal symmetries. The phase diagram for different values of the relevant coupling constants is obtained. The different phases are characterized by distinct dispersion relations for probe fermionic modes in the AdS geometry. We find semi-metallic phases characterized by the presence of Dirac cones and an insulating phase featuring a mass gap with a mild anisotropy. Remarkably, we find as well an anisotropic semi-Dirac phase characterized by a massless a fermionic excitation dispersing linearly in one direction while quadratically in the other.

Structural and physical properties of the MAX phases RE2SX (RE = La ∼ Lu; X=B, C, N) via first-principles calculations

MAX phase layered compounds have high temperature stability, excellent mechanical properties, good thermal conductivity and electronic properties. In order to provide a certain theoretical basis for further experimental exploration of the MAX phase with rare-earth (RE) element, a detailed study of the RE2SX (RE = La∼Lu, X = B, C, N) MAX phase has been performed by using first-principles calculations. The study comprehensively examines the mechanical properties, elastic anisotropy, dynamical stability and thermal properties of the RE2SX phase, and the results demonstrate that 37 RE2SX phases satisfied the thermodynamical, mechanical and dynamical stabilities among the 45 compounds. The mechanical properties of the 37 stable phases were systematically analyzed, including bulk modulus, shear modulus, Young's modulus and hardness. Among these phases, La2SN, Ce2SB/N, Pr2SB/N, Nd2SB/N, Pm2SB, Sm2SB, Eu2SB, and Gd2SB were identified as exhibiting promising ductility potential. In the RE2SX carbides, the occupied states on the Fermi level of the RE2SC phase are very small, with the conduction band is mainly occupied by the valence electrons of the RE and S atoms, suggesting that these carbides exhibit notable electronic characteristics. These results can enhance our understanding of RE2SX phases and provide valuable guidance for future experimental research.

Refining Alnico 8 magnets with composition optimization of matrix phase, directional solidification and magnetic field annealing

Optimized shape anisotropy of the Fe-Co rich ferromagnetic (α1) phase and the effective separation of the α1 and α2 phases with maximum magnetization difference—where α2 represents a paramagnetic magnetic phase—are the key parameters for maximizing the magnetic properties of Alnico magnets. In this manuscript, efforts have been undertaken to optimize the shape anisotropy of the α1 phase and increase the difference in magnetization and separation between α1 and α2 phases by fine tuning Al and Ni contents, directional solidification and magnetic field annealing methods. At first, Alnico magnets were fabricated by adjusting the content of α2 phase followed by homogenization, magnetic field annealing at high temperature, and low-temperature tempering. Intrinsic coercivity (Hcj) of ⁓146.0 kA/m, remanence (Br) of ⁓0.90 T and maximum energy density ((BH)max) of 46.02 kJ/m3 are achieved in the magnet with 8.2 wt% Al and 12.8 wt% Ni treated in field of 1.5 T for 10 minutes. At the second stage, the magnet with optimal magnetic properties is directionally solidified to develop columnar grains, and then the α1 phase is grown in the direction of the columnar grains by magnetic field annealing to enhance the (BH)max to 79.8 kJ/m3. The axial ratio of the α1 phase increased significantly with the increase of the grain size, particularly in the directionally solidified magnets. The Curie temperature of the α1 phase is noted near 1150 K, while the Curie temperature of the α2 phase is below 400 K. The magnets demonstrated excellent temperature stability, with magnetic properties decreasing by only 10–12 % at 800 K. These results may pave the way for further development of Alnico magnets specifically for high temperature applications.

A Study on Resolving Dynamic analysis using deep learning Framework Logical Methods

Deep learning technologies have gained a great deal of interest in recent months for demonstrating material removal capabilities in a variety of separation, categorization, as well as other machine vision activities. The majority of these deep networks are built employing convolution or completely convolution structures. Our suggested Dynamic and Static gestures System guided by a hand gesture high dimensional data methodology We use a snapshot of a human's thoracic spine to determine the person's depth and the size of the space around his or her hands. In this research, we provide a novel object-based deep-learning framework for semantic segmentation of extremely high-resolution satellite data. In specifically, we leverage object-based prior record by augmenting a fully convolutional neural network's training strategy with an anisotropic diffusion data pre-processing phase and an additional loss term. The goal of this restricted framework is to ensure that similar visual data is assigned to the same semantic class. Here, we employ intermediate steps based on traditional image processing techniques to aid in the resolution of the subsequent problem of classification, detection, or segmentation. Research shows that adding pre- and post-processing steps to a deep learning pipeline can boost model performance over using only the network. Recent advances in UQ algorithms used for deep learning are analysed, and their potential for use in relevance feedback is addressed. It also emphasizes basic research difficulties and directions linked with UQ. Quantifiably, man-made classes with more precise geometry, such as buildings, benefited the most from our strategy, particularly along object borders, indicating the developed approach's enormous potential. The purpose of this paper is to offer an overview of the approaches used inside deep learning frameworks to either appropriately prepare the input (pre-processing) or enhance the outcomes of the network output (post-processing), with an emphasis on digital pathology image analysis.

Investigation of transverse exchange-springs in electrodeposited nano-heterostructured films through first-order reversal curve analysis

The prerequisite of efficient exchange-spring nano-heterostructures, i.e., tuning both hard and soft phases at a nanometer level, has posed significant preparation challenges to ensure effective exchange-coupling. Here, we present a novel approach to fabricate transverse exchange-spring nano-heterostructures using single starting material through an “in situ” electrodeposition technique at room temperature. Utilizing modified acidic bath chemistry and controlled hydrogen evolution, we successfully prepared stress-free, shiny, fine-grained amorphous, and nanocrystalline Co-rich cobalt phosphorus films. These nano-heterostructured films exhibit a unique non-collinear anisotropy-driven transverse exchange-spring behavior, investigated systematically under ambient conditions. The comprehensive functional analyses reveal that intricate interplay between in-plane (IP) anisotropy of amorphous phase and out-of-plane (OOP) anisotropy generating from a nanocrystalline structure compete with each other, while producing characteristic stripe domain structures to novel corrugated stripe domain shapes. The angle-dependent first-order reversal curve distributions demonstrate new insights into the magnetic reversal mechanisms, further confirming the non-exchange-spring and exchange-spring nature of the films depending on the prevalent interfacial exchange coupling. Formation of anisotropy-driven metastable-state due to competition between IP and OOP anisotropy at a particular OOP orientation has led the normal exchange-spring structures to a transverse exchange-spring structure. Micromagnetic simulations, in excellent agreement with experimental data, further elucidate the formation of characteristic stripe domain patterns and the influence of anisotropy on the magnetic properties. The innovative methodology and detailed functional analysis presented here offer significant understanding to the field of exchange-spring magnetic materials, including anisotropy-driven metastable states, demonstrating the potential for scalable and cost-effective fabrication of advanced nano-heterostructures with tailored magnetic properties.

In-situ synchrotron diffraction study on the anisotropic deformation and phase transformation behaviors in NiTi shape memory alloy fabricated by laser powder bed fusion

The stress-induced martensitic transformation (SIMT) and plastic deformation are the crucial factors governing the functional and mechanical properties of polycrystalline NiTi shape memory alloys. This study investigated and compared the SIMT and deformation behaviors along the building direction (BD) and horizontal direction (HD) of NiTi components fabricated by laser powder bed fusion (LPBF), using electron backscatter diffraction (EBSD) and in-situ synchrotron-based X-ray diffraction during uniaxial tension. The experimental results revealed that loading along the HD resulted in both a higher SIMT rate and increased dislocation density compared to the BD of the printed block. Additionally, both HD and BD loadings demonstrated multiple lattice correspondences from the B2-austenite to B19'-martensite phase. The BD sample, with its more complex grain boundary network, densely distributed localized stress and strain, as well as, smaller grain size, contributed to a lower SIMT rate and dislocation density. These findings underscore the impact of crystallographic orientation and microstructural characteristics on the mechanical responses and SIMTs of LPBF-fabricated NiTi alloys.

Carbon quantum dots derived from rice straw doped with N and S and its nanocomposites with hydroxypropyl cellulose nanocomposite

As biomass, rice straw (RS) is often valorized as a precursor of green products. In this respect, the RS-based carbon quantum dots (CQDs) are synthesized doped with N and S during the preparation. Synergistic doping with lipoic acid and ethylenediamine can vastly increase the yield of CQD from rice straw from 6.14 % to 62.8 %, and sulfur doping plays a more important role on the surface functional groups of the quantum dots. Further assessment is achieved toward the performance of SN-CQDs-hydroxypropyl cellulose nanocomposites. The optical behavior of synthesized SN-CQDs, and the critical concentration of its liquid crystal behaviors, at which the anisotropic phase begins to emerge, is approximately 1 %. Incorporating it into HPC, especially at 5 %, provided nanocomposite films with effective liquid crystal, tensile strength, and thermal stability. This sample's texture reveals a planar structure with colors ranging from yellow to red. The synergistic effect of incorporating SN-CQDs is shown by improving the strength to ~282.1 %, and the activation energy increased from 583.6 kJ.mol−1 to 615.1 kJ/mol. HPC-SN-CQDs can be assembled into an LED device, emitting warm light, of which CIE coordinate is (0.34,0.43).

Phase field modeling for composite material failure

AbstractA computational framework of anisotropic phase field model is used to investigate the effects of effective critical energy release rate, interface property, and hole shape on the failure of composite material in this paper. This model is implemented in ABAQUS using a user‐defined element (UEL). First of all, the model is validated through a benchmark model. Second, the effective critical energy release rate is introduced, which can improve the accuracy of the simulation result. Then, the influence of strong and weak interfaces on the failure of composite material is studied. It can be found that the interface properties can change the evolution mode of crack and the final load–displacement response. Finally, the effect of hole shapes on the failure of the composite material is also explored, which shows that the bearing capacity of model can be improved by changing the shape of the hole.

PSF-engineered snapshot full-Stokes polarizing-spectral-imaging via metasurface with reciprocally encoded anisotropic detour phase

A broadband snapshot full-Stokes polarizing-spectral-imaging (PSI) is achieved by reciprocally designing a metal–insulator-metal metasurface with anisotropic detour phase to generate polarizing-spectrally dependent dot-array-shaped point-spread-function (PSF), and the high dimensional information can be retrieved from one snapshot intensity image through the post-computation. It overcomes the restriction on the wavelength selection in principle faced by the propagating phase modulation scheme used in the previous metasurface-based PSI approaches, and brings advantages including compact configuration, fast acquisition and broadband operation. The dependence of the engineered PSF on the polarizing-spectral channel across 100 nm in the visible band is experimentally verified and analyzed, consistent well with the simulation. Reconstruction results for the high dimensional imaging are presented in simulations and experiments based on the established model.

Anisotropic and shape-stable sugarcane-based phase change composites in the application of solar thermal energy storage

The study of anisotropically thermal conductive phase change composites (PCCs) with shape-stability is of great importance to improve the intermittent issues in solar thermal utilization, while some drawbacks like the high cost, low thermal conductivity, and poor durability of current PCCs restrains their practical applications. Herein, a cheap and scalable biomass-based PCC containing carbonized sugarcane (CSC), polyethylene glycol (PEG), and graphene (GF) is proposed. The abundant vessels inside CSC result in a high PEG loading rate of 82.48 %. The naturally occurring anisotropic structure inside CSC can drive GF to be oriented along the lengthwise direction, which gives PCC a high thermal conductivity anisotropy degree of 1.45. The prominent anisotropy improves the lengthwise thermal diffusion and restrains the transverse heat leakage to the environment. Besides, the loaded GF can further enhance the light absorption of PCC to 98 %. As a result, the prepared PCC can achieve high solar-thermal energy storage efficiencies of 79.3–91.7 % with variable solar intensity from 1 to 2 suns. Meanwhile, good anti-leakage and durability performances promote the practical utilization of PCCs. The present work paves a promising road for manufacturing biomass-based anisotropic PCCs in efficient solar thermal energy storage.

Study of structural, Griffiths phase, and magneto-crystalline anisotropy in Pr0.47La0.20K0.33Mn0.91Cu0.09O3 perovskite manganite

Study of structural, Griffiths phase, and magneto-crystalline anisotropy in Pr0.47La0.20K0.33Mn0.91Cu0.09O3 perovskite manganite

Anisotropic cellulose-based phase change aerogels for acoustic-thermal energy conversion and management

Porous materials are usually used as sound-absorbing materials to alleviate noise pollution problems. However, the heat energy conversed from the acoustic energy is wasteful. Herein, anisotropic cellulose-based phase change aerogels (MXene/CNF-C/PEG aerogels) are fabricated by facile directional freeze casting method with anisotropic porous structure, efficient sound wave absorption, acoustic-thermal conversion and thermal management capability. MXene/CNF-C/PEG aerogels with shape stability are formed by hydrogen bonding forces between carboxylated cellulose nanofibers (CNF-C) and PEG without chemical crosslinking. The addition of MXene not only increases thermal conductive performance to 150 % but also enhances acoustic-thermal conversion ability effectively. Moreover, the directional porous MXene/CNF-C/PEG aerogels (DMCPs) possess high energy storage density (143.0 J/g) and acoustic-thermal conversion performance, which open up broad application prospect in the field of acoustic to heat energy conversion and storage.

Regulation of macroporous cellulose microspheres via phase separation force induced by carbon nanotubes doping for enhanced protein adsorption

The burgeoning requirement for purified biomacromolecules in biopharmaceutical industry has amplified the exigency for advanced chromatographic separation techniques. Herein, macroporous cellulose microspheres (CCMs) with micron-sized pores are produced by a facile regulation via carbon nanotubes (CNTs). In this strategy, the incorporation of CNTs breaks the homogeneous regeneration of the cellulose, thus providing anisotropic phase force to produce macropores. The CCMs have manifested a faster mass transfer rate and more available adsorption sites owing to well-defined macropores (2.69 ± 0.57 μm) and high specific surface area (147.47 m2 g−1). Further, CCMs are functionalized by quaternary ammonium salts (GTAc-CCMs) and utilized as anion adsorbents to adsorb pancreatic kininogenase (PK). The prepared GTAc-CCMs show rapid adsorption kinetics for PK at pH 6.0, reaching 90 % equilibrium within 60 min. Also, GTAc-CCMs for PK exhibit high adsorptive capacity (632.50 mg g−1), excellent recyclability (> 80 % removal amount after 10 cycles) and selectivity especially at pH 6.0. Notably, the GTAc-CCMs have been successfully applied in a fixed-bed chromatography process, indicating their potential as an effective chromatographic medium for rapid separation of biomacromolecules.

Modeling the Doppler spectrum of waves backscattered from an expanding cloud for anisotropic phase functions

Modeling the Doppler spectrum of waves backscattered from an expanding cloud for anisotropic phase functions

In Situ Lattice-Resolution Revelation of the Origins of Unexplored Anisotropic Sodiation Kinetics and Phase Transition in the Niobium Sulfide Anode.

Layered transition metal dichalcogenides (TMDs) have exhibited huge potential as anode materials for sodium-ion batteries. Most of them usually store sodium via an intercalation-conversion mechanism, but niobium sulfide (NbS2) may be an exception. Herein, through in situ transmission electron microscopy, we carefully investigated the insertion behaviors of Na ions in NbS2 and directly visualized anisotropic sodiation kinetics. Lattice-resolution imaging coupled with density functional theory calculations reveals the preferential diffusion of Na ions within layers of NbS2, accompanied by observable interlayer lattice expansion. Impressively, the Na-inserted layers can still withstand in situ mechanical testing. Further in situ observation vertical to the a/b plane of NbS2 tracked the illusive conversion reaction, which could result from interlayer gliding or wrinkling associated with stress accumulation. In situ electron diffraction measurements ruled out the possibility of such a conversion mechanism and identified a phase transition from pristine 3R-NbS2 to 2H-NaNbS2. Therefore, the NbS2 anode stores Na ions via only the intercalation mechanism, which conceptually differs from the well-known intercalation-conversion mechanism of typical TMDs. These findings not only decipher the whole sodiation process of the NbS2 anode but also provide valuable reference for unraveling the precise sodium storage mechanism in other TMDs.