Flat State Research Articles

Self-healing and mechanical properties of a designed Zn2 + ionic clusters rubber engineered cementitious composites with tight bonding

In this study, a hydrophilic Carboxylated styrene butadiene rubber/ Zinc dimethacrylate (XSBR/ZDMA) rubber with a surface rich in ionic clusters was developed and introduced into engineered cementitious composites (ECC), focusing on the effect of the interfacial bonding between aggregate-matrix on the mechanical properties of ECC. As part of this study, the hydrophilicity of rubber was evaluated by scanning electron microscopy (SEM) and DSA100E tests. And the effects of matrix-aggregate bonding on the mechanical properties of ECC were assessed by uniaxial tensile tests, compared to normal rubber-ECC with the same 40 % replacement of silica sand, XSBR/ZDMA-ECC has 32.73 % higher tensile strength and 27.11 % higher ductility. In addition, electrochemical impedance spectroscopy (EIS) tests were conducted on the self-healing properties of ECC at different pre-loading levels. The test results indicate a high consistency between the electrochemical impedance spectroscopy (EIS) and the conclusions drawn from the second tensile experiment following self-healing, along with the digital microscope measurement of crack number and width. The results showed that the XSBR/ZDMA rubber established more chemical bonding connections with the cement matrix, resulting in finer cracks in the ECC, with a 20 % increase in the number of crack bars and a 36.8 % decrease in crack width compared to the same level of normal rubber-ECC. Moreover, under the conditions of dry and wet cycles, the fine cracks in the ECC exhibit a more effective self-healing effect. At 2 % preload, XSBR/ZDMA-ECC maintains strain hardening and high strength, exceeding normal rubber-ECC's ultimate load by 67.7 %. Characterization of ECC self-healing using electrochemical impedance spectroscopy showed a 66 % increase in real impedance values for XSBR/ZDMA-ECC and a 93.2 % increase in real impedance values for normal rubber-ECC over a 28-day self-healing age period at a 2 % preloading level, and the real impedance of XSBR/ZDMA-ECC was 56 % lower than that of normal rubber-ECC at 0 days of self-healing curing age, and the impedance value reached a flat state earlier. It is recognized in the field of ECC that aggregate-matrix interfaces are a gap in the literature, and the results of this study can contribute in some way to exploring this direction.

Research on roll profile thermal-force driving characteristics and joint control strategy in the multi-zone roll profile electromagnetic control technology

Roll profile electromagnetic control technology (RPECT) is a new roll gap shape control technology that can flexibly control the roll profile to meet the flatness control requirements of cold rolling mill. As basic control elements, electromagnetic sticks (ES) can drive the local zone bulging of electromagnetic control roll (ECR) to generate thermal-force contribution roll profiles. Due to the high order profile defects in the thin-gauge strip rolling process, the requirement of roll gap shape control in cold rolling mills is usually characterized by multi-zone and micro-scale. Therefore, a multi-zone roll profile electromagnetic control technology is proposed in this paper, which includes a multi-zone joint control strategy and a parameter preset method for basic control elements targeting roll profile. To conduct the parameterized impact analysis of stick distance and multi-stick control modes, a multi-zone joint control simulation model is established. Through the simulation analysis, the results show that it is feasible to use multiple basic control elements to adjust the multi-zone roll profile in the mechanism of action, and the total roll profile curve can be equivalent to the superposition of the individual bulging curve of different basic control elements with different space-time parameters. Meanwhile, the reasonable distance setting can effectively avoid the instability of thermal contribution roll profile control caused by too small distance between sticks and too strong thermal bulging driving. For the double-stick control mode or the three-stick control mode, using different temperature control method can assist ECR to realize the roll profile control goal that the low-order roll profile of the basic control element is superimposed to construct the high-order roll profile curve. According to strip flatness electromagnetic control experiment, the multi-zone joint control of RPECT can adjust the flatness defects above 100 IU to flat state, and can flexibly regulate local shape problems and control local buckling.

Impurity flat band states in the diamond chain

Flat band (FB) systems, featuring dispersionless energy bands, have garnered significant interest due to their compact localized states (CLSs). However, a detailed account on how local impurities affect the physical properties of overlapping CLSs is still missing. Here we study a diamond chain with a finite magnetic flux per plaquette that exhibits a gapped midspectrum FB with non-orthogonal CLSs, and develop a framework for projecting operators onto such non-orthogonal bases. This framework is applied to the case of an open diamond chain with small local impurities in the midchain plaquette, and analytical expressions are derived for FB states influenced by these impurities. For equal impurities in top and bottom sites under diagonal disorder, we show how the impurity states experience an averaged disorder dependent on their spatial extension, leading to enhanced robustness against disorder. For a single impurity, an exotic topological phase with a half-integer winding number is discovered, which is linked to a single in-gap edge state under open boundary conditions. Numerical simulations validate the analytical predictions.

Phase transition behavior and electrical properties of C/Sb2Te3 multilayer films on flexible polyimide substrates

Phase change memory has become one of the ideal choices for flexible electronic memory due to its advantages of fast operation speed, high durability and low power consumption. This paper is dedicated to the preparation of C/Sb2Te3 multilayer films on polyimide (PI) substrates for high-performance flexible phase change memory (FPCM). The findings indicate that C/Sb2Te3 multilayer films on PI substrates exhibit superior thermal stability (higher than that of Silicon substrates) and excellent mechanical bending properties (up to 1 × 104 bending cycles). The variations in optical properties, crystal structure, resistance drift and morphology were systematically investigated for the flat state, 5 × 103 bending cycles and 1×104 bending cycles. FPCM devices based on [C (2 nm)/Sb2Te3 (10 nm)]5 multilayer films have been fabricated, which are capable of reversible SET/RESET operation in the flat, bending state and 1 × 103 bending cycles. An electrothermal model of the FPCM device cell based on C/Sb2Te3 was constructed, and the simulation results confirmed its good thermal confinement capability (∼1278 K). This study demonstrates the potential of C/Sb2Te3 multilayer films based on PI substrates in FPCM.

Strain-Induced Tunable and Field-Free Spintronic THz Emitters Based on Flexible Substrate Heterostructures.

Spintronic THz emitters have been widely studied due to their advantages of broadband frequency, high efficiency, and easy fabrication. The spintronic THz signal is proportional to the magnetization of the ferromagnetic (FM) layer and requires an external magnetic field to maximize the THz signal intensity. Recently, a field-free emitter was designed based on a CoFeB/IrMn3 heterostructure via the exchange bias between two films. However, field-free spintronic THz emitters based on a common FM/nonmagnetic metal structure are rare. Here, we fabricate a tunable and field-free THz emitter with giant THz emission modulation ability based on a polyimide/CoFeB/Pt heterostructure. The THz emission can be modulated by changing the curvature radius of the polyimide substrate. After the emitter is forward bent, the THz radiation without an external magnetic field is stronger than in the flat state with a field, which we attribute to in-plane magnetic anisotropy on the FM layer induced by the tensile strain. When we curve the emitter backward, the THz intensity decreases sharply. Moreover, the modulation (ΔS/Smax) of the THz wave from the forward-curved and backward-curved emitter is over 95%, and the device shows good cyclic repeatability. We provide a novel way to design field-free spintronic THz sources, and flexible devices are promising for application in THz devices.

Density functional theory investigation of hypervalent iodine KICl2 passivation at PbI2 vacancy sites on the MAPbI3 surface

This study explores the impact of hypervalent KICl2 passivation on the electronic properties and stability of MAPbI3 perovskite slabs with PbI2 vacancies using density functional theory (DFT). Adsorption energy calculations reveal that KICl2 exhibits stronger binding energy (−4.73 eV) compared to O2 (−3.32 eV) and H2O (−3.28 eV), indicating higher stability on the MAPbI3 surface. However, due to the potential for KICl2 to dissociate into KCl and ICl in solution, these compounds were also evaluated as alternative passivation agents. The surface free energy of the KICl2-passivated slab is the lowest among the configurations studied, further confirming its enhanced surface stability. The projected density of states (PDOS) and band structure analyses show that KICl2 passivation introduces defect states near the conduction band minimum (CBM), reducing the bandgap from 1.89 eV (clean surface) to 1.81 eV. These defect states, contributed by Cl-3p and I-5p orbitals, enhance charge separation, potentially improving carrier collection. In contrast, the KCl-ICl passivated surface exhibits flat states near valence band edge, which could increase hole density and reduce hole mobility. Optical absorption calculations indicate that the KICl2-passivated surface shows stronger absorption in the 3–7 eV range. These findings suggest that KICl2 passivation improves both the electronic properties and surface stability of MAPbI3, offering a promising strategy for enhancing perovskite solar cell efficiency.

Phase transition behavior of (MoTe2)xSb1-x thin films based on flexible PEEK substrates

Flexible information memory played a key role in flexible electronic devices and smart wearables. This paper was focused on the effect of flexible deformation on the properties of (MoTe2)xSb1-x nano-phase-change films based on PEEK substrates. By placing the films at the finger, wrist, back of the hand and elbow and bending them, the resistance values showed periodic fluctuations with bending but the changes were not significant. After 100,000 bending cycles and 4,000 s of vibration, the films successfully achieved the transformation from a shapeless to a structured state. The stress caused by bending and vibration affects the surface roughness of the flexible film and weakens the adhesion between the film and the substrate. Flexible (MoTe2)0.07Sb0.93 film electronics were prepared, and the phase change memory devices could realize reversible transitions between SET and RESET states with 100 ns pulse widths in the flat state, after 100,000 bending cycles, and after 4,000 s of vibration. These findings indicated that (MoTe2)0.07Sb0.93 films based on flexible PEEK substrates had promising applications in the field of flexible phase change memory.

Dilational rheological properties of extended anionic surfactants at decane-water interface

The dynamic interfacial dilational properties of extended surfactants octadecyl-(polypropylene oxide)m-(polyethylene oxide)n-carboxylic sodium (C18POmEOnC) with different numbers of polypropylene oxide (PO) and polyethylene oxide (EO) groups at the decane–water interface were investigated by means of oscillating drop method. The influences of interface ageing time, dilational frequency, bulk concentration and interfacial pressure on the dilational properties were investigated. The experimental results demonstrate that, at low concentrations, the adsorption film is predominantly influenced by diffusion exchange, while intermolecular interactions at the interface play a more significant role at high concentrations. Beyond the critical micelle concentration (CMC), the primary relaxation process in the adsorption film is driven by the formation of micellar structures. Additionally, the weak hydrophobic PO groups exhibit compressibility and extensibility, facilitating the formation of spring-like helical structures at the decane–water interface. As a result, the dilational modulus increases and the phase angle decreases in low concentration with the increase of PO number. With increasing concentration, the weak hydrophilic EO chains gradually transition from a partially flat state to an upright orientation toward the aqueous phase, forming sublayer structures through polar interactions. At this stage, the increase in EO group chain length has a more pronounced impact on the elastic modulus compared to PO groups. These experimental findings suggest the existence of a mechanistic model for the extended surfactant adsorption films.

To justification of concrete strength criterion at biaxial compression

Introduction. Numerous experimental data from Russian and foreign researchers indicate that the classical plasticity hypotheses do not take into account the different resistance to uniaxial tension and compression, the influence of the spherical tensor. At the same time, experiments show that the ultimate resistance depends on the type of stress state, and hydrostatic pressure increases the strength and plasticity of solids. Aim. To establish the dependence of the influence of the second component of stresses during biaxial compression of concrete on the parameters of the complete diagrams of deformation of the material σbR and εbR it is necessary to describe these diagrams, and to construct a closed curve on the plane of the main stresses (concrete strength criterion). Materials and methods. Based on the experimental materials of foreign and domestic researchers, including the experiments of the authors of the article, methods of mechanics of deformed solids, limit curves and a closed curve on the plane of the main stresses in the form of a chain line forming the smallest area strength surface in the form of a catenoid are proposed. Results. The article provides an analysis of the known strength criteria from the point of view of their geometric interpretation in the stress space. It is shown that these studies relate mainly to metals and metal structures, and for the design of reinforced concrete and steel-concrete structures in a complex stress state, it is necessary to develop an appropriate criterion for the strength of concrete. Conclusions. As a result, the proposed limit curves and the surface (material strength criterion) on the plane of main stresses in the form of a catenoid accurately reflect the behavior of concrete under conditions of uniform and uneven flat stress state, and the equation of the surface in the form of a catenoid is a generalization of the equations of limit curves for each of the three types of flat stress state. At the same time, there is no overestimation of strength in the "compression – compression" area in this case.

Photo-annealed electrospun TiO2 nanofibers as ion-storage layer for self-rechargeable Zn-based electrochromic energy storage device

Developing a self-rechargeable transparent electrochromic energy storage device (EESD) is highly demanding for advancing electrochromic technology and energy harvesting capabilities. In this study, we introduce a room-temperature photo-annealing method to fabricate electrospun titanium oxide (TiO2) nanofibers, serving as an ion-storage layer (ISL) on the counter electrode. By monitoring the composition and morphology of the precursor before and after ultraviolet/ozone irradiation, we confirm the formation of oxide nanostructures in electrospun TiO2 nanofibers, which enhances ion transport in the fabricated EESDs. The structural and surface properties of the photo-annealed ISL are comprehensively analyzed using various characterization techniques. Enhanced electrochromic performances are evidenced through cyclic voltammetry, spectroelectrochemical measurements, and charge storage assessments. The Zn-based EESDs with ISL (ISL Zn-EESDs) display rapid electrochemical kinetics, high charge-storing capacities, and long lifespans, with open-circuit potential of 1.2 V, optical contrast of 77 %, discharge capacity of 92 mA h/g, coloration efficiency of 58.63 cm2/C, and 99.9 % efficiency retention up to 250 cycles in both flat and bent states. Furthermore, the practical viability of the ISL Zn-EESDs is demonstrated by powering an LED lamp for several minutes. This approach highlights the potential of ISL Zn-EESDs for developing flexible smart windows, opening up a range of promising applications.

Adaptive No‐Tip Distribution of Rich Charge‐Density‐Clusters Guiding Confinement Deposition with Repair Function toward Highly Reversible Zinc Anode

AbstractThe plating/stripping behavior of Zn ions on the Zn anode, driven by an electric field, is a key process in determining the performance of aqueous zinc ion batteries (AZIBs). Process‐induced unevenness of commercial Zn foils results in poor reversibility of Zn anodes. Herein, a self‐healing dynamic anode/electrolyte interface is constructed by incorporating hydroxyl‐rich alcohols with high charge density and zincophilicity into the original electrolyte. These alcohols selectively anchor on electron‐poor sites in the charging state, inducing domain‐limited deposition of Zn2+ to achieve a dense, uniform, and flat deposition state. As a result, a durable Zn anode with excellent electrochemical reversibility can be realized in practical cycling (average Coulombic efficiency of 99.5%). Even under deep plating/stripping conditions (5 mA cm−2 and 5mAh cm−2), the modified electrolyte exhibits a remarkable repair effect on corroded Zn anodes that have been cycled in base electrolyte, extending the lifespan to over 1,020 h. This represents a 15.6‐fold enhancement in lifespan compared to recycling in the base electrolyte. This strategy for electrolyte additive directly influences the design of ultra‐long‐life AZIBs and provides concrete concepts for the recovery of zinc anodes.

Chiral kagome superconductivity modulations with residual Fermi arcs.

Superconductivity involving finite-momentum pairing1 can lead to spatial-gap and pair-density modulations, as well as Bogoliubov Fermi states within the superconducting gap. However, the experimental realization of their intertwined relations has been challenging. Here we detect chiral kagome superconductivity modulations with residual Fermi arcs in KV3Sb5 and CsV3Sb5 using normal and Josephson scanning tunnelling microscopy down to 30 millikelvin with a resolved electronic energy difference at the microelectronvolt level. We observe a U-shaped superconducting gap with flat residual in-gap states. This gap shows chiral 2a×2a spatial modulations with magnetic-field-tunable chirality, which align with the chiral 2a×2a pair-density modulations observed through Josephson tunnelling. These findings demonstrate a chiral pair density wave (PDW) that breaks time-reversal symmetry. Quasiparticle interference imaging of the in-gap zero-energy states reveals segmented arcs, with high-temperature data linking them to parts of the reconstructed vanadium d-orbital states within the charge order. The detected residual Fermi arcs can be explained by the partial suppression of these d-orbital states through an interorbital 2a×2a PDW and thus serve as candidate Bogoliubov Fermi states. In addition, we differentiate the observed PDW order from impurity-induced gap modulations. Our observations not only uncover a chiral PDW order with orbital selectivity but also show the fundamental space-momentum correspondence inherent in finite-momentum-paired superconductivity.

Scalar curvature for metric spaces: Defining curvature for quantum gravity without coordinates

Geometrical properties of spacetime are difficult to study in nonperturbative approaches to quantum gravity like causal dynamical triangulations (CDT), where one uses simplicial manifolds to define the gravitational path integral, instead of Riemannian manifolds. In particular, in CDT one only relies on two mathematical tools, a distance measure and a volume measure. In this paper, we define a notion of scalar curvature, for metric spaces endowed with a volume measure or a random walk, without assuming nor using notions of tensor calculus. Furthermore, we directly define the Ricci scalar, without the need of defining and computing the Riemann or the Ricci tensor . For this, we make use of quantities, like the surface of a geodesic sphere, or the return probability of scalar diffusion processes, that can be computed in these metric spaces, as in a Riemannian manifold, where they receive scalar curvature contributions. Our definitions recover the classical results of scalar curvature when the sets are Riemannian manifolds. We propose two methods to compute the scalar curvature in these spaces, and we compare their features in natural implementations in discrete spaces. The defined generalized scalar curvatures are easily implemented on discrete spaces, like graphs. We present the results of our definitions on random triangulations of a 2D sphere and plane. Additionally, we show the results of our generalized scalar curvatures on the quantum geometries of 2D CDT, where we find that all our definitions indicate a flat ground state of the gravitational path integral. Published by the American Physical Society 2024

Designing edge states from fractional polarization insulators

We theoretically investigated disconnected dispersive edge states in an anisotropic honeycomb lattice without chiral symmetry. When both mirror and chiral symmetries are present, this system is defined by a topological quantity known as fractional polarization (FP) term and exhibits a bulk band gap, classifying it as an FP insulator. While the FP insulator accommodates robust, flat topological edge states (TES), it also offers the potential to engineer these edge states by deliberately disrupting a critical symmetry that safeguards the underlying topology. These symmetry-breaking terms allow the edge states to become dispersive and generate differing configurations along the open boundaries. Furthermore, disconnected helical-like and chiral-like edge states analogous to TES seen in quantum spin and anomalous hall effect are achieved by the finite size effect, not possible from the symmetry-breaking terms alone. The demonstration of manipulating these edge states from a FP insulator can open up new avenues in constructing devices that utilize topological domain walls.

Atomically Thin Kagome-Structured Co9Te16 Achieved through Self-Intercalation and Its Flat Band Visualization.

Kagome materials have recently garnered substantial attention due to the intrinsic flat band feature and the stimulated magnetic and spin-related many-body physics. In contrast to their bulk counterparts, two-dimensional (2D) kagome materials feature more distinct kagome bands, beneficial for exploring novel quantum phenomena. Herein, we report the direct synthesis of an ultrathin kagome-structured Co-telluride (Co9Te16) via a molecular beam epitaxy (MBE) route and clarify its formation mechanism from the Co-intercalation in the 1T-CoTe2 layers. More significantly, we unveil the flat band states in the ultrathin Co9Te16 and identify the real-space localization of the flat band states by in situ scanning tunneling microscopy/spectroscopy (STM/STS) combined with first-principles calculations. A ferrimagnetic order is also predicted in kagome-Co9Te16. This work should provide a novel route for the direct synthesis of ultrathin kagome materials via a metal self-intercalation route, which should shed light on the exploration of the intriguing flat band physics in the related systems.

65‐1: Invited Paper: Biaxially Formed LC Cells and Organic Transistors for 3D Curved Displays for Automotive Applications

Unsurprisingly, the FPD industry began life making flat display panels. In recent years curved displays have entered production, including TVs and foldable smartphone displays built on polyimide. These are manufactured in a flat state, then uniaxially curved.However, many real‐world surfaces have surfaces with biaxial curvature, either for aesthetic or functional reasons, and require biaxially curved displays with active optics that enable these surfaces to actively modulate, steer and focus light.We report on recent developments which show that flexible OTFT arrays, LC cells and Organic LCDs (OLCDs) can be biaxially thermoformed to spherically curved surfaces.

Tensile behavior of square-twist origami inspired mechanical metamaterials with soft joints and chirality applications

The performance and behavior of origami-inspired mechanical metamaterials are closely related to their structural design and the joints sub equivalent to the crease, in addition to material selection. Current research on square-twist origami focused on the unidirectional formation between its stable states. However, the complete process of squeezing-folding and stretching-unfolding as well as the mechanical behavior under tensile loading have not been thoroughly studied. In this study, square-twist origami mechanical metamaterials (STOMMs) with soft joints are proposed and investigated. The complete process of typical STOMMs from a flat state to folded stable state by extrusion folding and then returning to a flat state by stretch unfolding is explored using the finite element method. The strain energy and deformation characteristics of STOMMs are revealed at eight special stages during the folding, stable state, and unfolding processes. Additionally, the influence of geometric parameters on strain energy, deformation, and tensile behavior is also investigated. Finally, inspired by origami chirality, combinatorial mechanical metamaterials with self-locking/non-self-locking behavior are proposed and validated for their tensile and self-locking behavior. The studies could provide new content for origami-inspired soft joint mechanical metamaterials in terms of self-locking and load-bearing.

Superconductivity in breathing kagome-structured C14 Laves phase XOs2(X = Zr, Hf)

Recently, the emergence of superconductivity in kagome metals has generated significant interest due to its interaction with flat bands and topological electronic states, which exhibit a range of unusual quantum characteristics. This study thoroughly investigates largely unexplored breathing kagome structure C14 Laves phase compounds XOs2 (X = Zr, Hf) by XRD, electrical transport, magnetization, and specific heat measurements. Our analyses confirm the presence of the MgZn2-type structure in ZrOs2 and HfOs2 compounds, exhibiting type-II superconductivity with critical temperature ( TC ) values of 2.90(3) K and 2.69(6) K, respectively. Furthermore, specific heat measurements and electron–phonon coupling constants for both compounds indicate weakly coupled fully gapped superconductivity.

Multi-stable metastructure with multi-layer and multi-degree of freedom: A numerical and experimental investigation

This paper proposes a family of multi-stable metastructures with multiple layers, which possess the capability of multi-degree of freedom deformations. In its single layer, four preshaped beams connecting two frames are employed as the main component for the design of multi-stable metastructures. Compared with the traditional flat state obtained by axial compression when all beams snap through, four inclined stable states are easy to trigger by lateral compression at a local position when two adjacent beams snap through. The transitions between these states are studied by both experiments and numerical simulation. The transition to inclined states requires less energy than the transition to the flat state. Different trends of load–displacement responses are associated with loading positions and transitions. A parametric analysis is performed to illustrate the relationship between the stability of inclined states and critical parameters, such as span, apex height, and thickness. Two types of hourglass double-layer units are designed and studied through experiments. The continuous transitions in two steps or three steps are observed, and the load–displacement response is the accumulation of responses from each single layer. At last, two multi-layer structures with multi-stability have been developed to demonstrate their deformation capability in multiple directions through multiple steps.

Flexible light-stimulated artificial synapse based on detached (In,Ga)N thin film for neuromorphic computing

Because of wide range of applications, the flexible artificial synapse is an indispensable part for next-generation neural morphology computing. In this work, we demonstrate a flexible synaptic device based on a lift-off (In,Ga)N thin film successfully. The synaptic device can mimic the learning, forgetting, and relearning functions of biological synapses at both flat and bent states. Furthermore, the synaptic device can simulate the transition from short-term memory to long-term memory successfully under different bending conditions. With the high flexibility, the excitatory post-synaptic current of the bent device only shows a slight decrease, leading to the high stability. Based on the experimental conductance for long-term potentiation and depression, the simulated three-layer neural network can achieve a high recognition rate up to 90.2%, indicating that the system comprising of flexible synaptic devices could have a strong learning-memory capability. Therefore, this work has a great potential for the development of wearable intelligence devices and flexible neuromorphic systems.