Multilayer Structure Research Articles

Multidimensional dynamic control of optical skyrmions in graphene–chiral–graphene multilayers

Abstract Optical skyrmions are topological quasiparticles with a complex vectorial field structure. Their associated characteristics of ultra-small, ultra-fast and topological protection have great application prospects in high density data storage, light matter interaction and optical communication. At present, the research of optical skyrmions is still in its infancy, where the construction and flexible regulation of different topological textures are current research hotspot. Here, we combine the twist degree of freedom of materials and optical skyrmions. Based on graphene–chiral–graphene multilayers structure, we demonstrate the field mode symmetry and hybridization to form Bloch-type graphene plasmons skyrmion lattice. At the same time, by changing chirality parameter, the Fermi energy of graphene and the phase of incident light, multidimensional control of Bloch-type optical skyrmions can be realized. Our work demonstrated that the properties of materials provide the additional dimensions to regulate the topological states, and the combination of different materials structures provides the possibility for dynamic construction and manipulation of multiple topological states, which is expected to find applications in integrated nanophotonics devices.

Cell envelope diversity and evolution across the bacterial tree of life.

The bacterial cell envelope is a complex multilayered structure conserved across all bacterial phyla. It is categorized into two main types based on the number of membranes surrounding the cell. Monoderm bacteria are enclosed by a single membrane, whereas diderm cells are distinguished by the presence of a second, outer membrane (OM). An ancient divide in the bacterial domain has resulted in two major clades: the Gracilicutes, consisting strictly of diderm phyla; and the Terrabacteria, encompassing monoderm and diderm species with diverse cell envelope architectures. Recent structural and phylogenetic advancements have improved our understanding of the diversity and evolution of the OM across the bacterial tree of life. Here we discuss cell envelope variability within major bacterial phyla and focus on conserved features found in diderm lineages. Characterizing the mechanisms of OM biogenesis and the evolutionary gains and losses of the OM provides insights into the primordial cell and the last universal common ancestor from which all living organisms subsequently evolved.

A quasi-3D SinZZ model-driven multi-field Chebyshev FEM for nonlinear vibration control in multilayer multiferroic composite plates

This paper presents an advanced numerical method for modeling and mitigating nonlinear vibrations in thin multilayered fiber-reinforced multiferroic composite plates, addressing complex multi-physical interactions. The proposed methodology leverages a multi-physical coupling Chebyshev finite element formulation, utilizing high-order shape functions derived from Chebyshev polynomials. By integrating the strengths of spectral element methods and Legendre spectral finite element methods, this approach effectively overcomes challenges such as shear locking and spurious zero energy modes while ensuring high convergence rates in multi-physical problems. A quasi-3D refined model, incorporating the Murakami zig-zag model and sinusoidal shear deformation theory, is employed to accurately capture the nonlinear Von Kármán strain–displacement relationship and the magneto-electro-elastic coupling in multilayer structures with thickness-dependent material properties. To suppress nonlinear vibrations, the study utilizes a closed-loop multiphysical Chebyshev finite element model for time-domain analysis of viscoelastically damped systems, employing the Golla–Hughes–McTavish model. The results underscore the significant influence of multiferroic properties and the strategic distribution of ferroelectric fibers within the substrate on the dynamic behavior of the plate. The numerical validation, supported by rigorous verification, demonstrates the robustness of the proposed method in effectively simulating and controlling multilayer fiber-reinforced multiferroic composite plates. Additionally, this research highlights the potential for significant vibration reduction through semi-active damping mechanisms, offering valuable insights for practical applications in industries where precision and stability are critical.

Fundamental mechanical relations of open-cell metal foam composite materials with reticular porous structure

The compressive behavior is one of the most fundamental mechanical properties for engineering materials. In this paper, the octahedral structure model of porous materials is used to evolve the mechanical analysis model under compressive loading for the porous composite materials, which are resulted from reticular metal foams with pore struts presenting multilayered structure. Starting from this analysis model, some fundamental mechanical relationships, including those of the safe load-bearing and overall strength, have been deduced for these porous composite materials. The compressive strength has been characterized for the porous composite body, corresponding to the overall failure caused by the prior breakage of the strut core and by the prior breakage of the strut shell, respectively. The nickel foam products manufactured on the production line of enterprise were used to make porous composite materials by coating the pore struts with epoxy resin, and the metal foam composite material was obtained with the composite pore-struts of metal/resin multilayered structure. Using this porous composite material for compression experiments, it is found that the experimental data match well with the mathematical relationship from the present theoretical model. The results verify the feasibility of this analysis model and the practicality of the relevant mathematical relationship.

Stable energy storage performance of introduced PI-PESU dielectric composite serving at the high electric and thermal fields with the designed layer structure

Excellent energy storage performance of dielectric capacitor is critical in modern electronic devices and power systems. However, the key component of dielectric composite may fail to function properly under severe service conditions, such as elevated temperature and great applied electric field. Here, the linear dielectrics of PI and PESU with high glass transition temperature (Tg) were proposed to improve the energy storage performance of composite, which hold the weakened carrier migration. The large band-gap of PESU and tight molecular chain of PI are beneficial for reducing leakage current density of composite, enhancing inter-molecular stability over a wide temperature and electric field range. Finally, the energy storage performance is improved by constructing a multi-layer structure with alternating outer layers. For instance, the discharge energy density (Ue) of 0.4PI-0.6PESU composite reaches 6.38 J/cm3 at 700 kV/mm and 80 °C. Significantly, the Ue of multi-layer 2/1/PVDF/1/2 composite is increased by 92.36 % at 80 °C and 400 kV/mm (from 2.88 J/cm3 to 5.54 J/cm3), and the efficiency (η) of it keeps at 68.5 %. Meanwhile, it owns a good cycle stability after 50,000 cycles with η > 90 %. This work provides a new direction of developing dielectric composite serving in severe service conditions for capacitors.

Process parameters selection for multi-layer friction surfacing of 7075 aluminium alloy

The effect of deposition parameters on the microstructure and mechanical properties are studied in multi-layer friction surfacing of 7075 aluminium alloy. These multi-layer structures were successfully manufactured after a parametric study which allows the generation of a deposition window, including an interface quality comparison. A higher rotational speed leads to a larger grain sizes. The coarse precipitates size and volume fraction decrease along the build direction in correlation with the thermal cycles’ profile. The top layer has a higher hardness after deposition, while bottom layers are in annealed state due to the growth of the strengthening phases. Fracture surface analysis revealed that transversal cracks are due to interlayer decohesion and that voids nucleated on the coarse precipitates.

Highly efficient multi-layer flexible heatsink for wearable thermoelectric cooling

Flexible thermoelectric cooler (fTEC), which interfaces well with curved human body surface and provides cooling functions, is an emerging candidate for personal thermal management and non-hospitalized medical treatment. Achieving efficient and long-term cooling performance of TEC requires high thermal conductivity and heat diffusion of the hot side, which has yet to achieve. In this study, we design and fabricate a highly thermally conductive and flexible heatsink with a multi-layered structure especially for wearable TEC wristband, which obtains a large temperature drop (8.8 °C) for imitated on-body test and the maxim 13.1 °C temperature decrease in air. Here, we demonstrate that a well-designed functional composite layer, including phase change material, thermally conductive fillers and metal foam, can establish an effective equilibration among cooling performance, thermal management capacity and mechanical property. Particularly, the heatsink with highly thermal conductive skeleton (k ∼ 2.7 W/mK) and effective heat dissipating fins can significantly improve heat conduction and dissipation, which improve the cooling performance by more than 55 %. With the help of theoretical simulation, we propose a promising strategy for heat management on thermoelectric device through a flexible multi-layered structure, paving the way for achieving practical applications of wearable thermoelectric coolers for personal thermal regulation or cooling therapy.

Thermal concentrating efficiency enhanced for multilayer circular thermal concentrators with gradient structures

The thermal concentrating efficiency of a thermal concentrator is determined by the ratio of its interior to exterior temperature gradients, serving as a crucial indicator influenced by the interaction of geometrical and thermal conductivity parameters. Finding simpler and more effective ways to improve thermal concentrating efficiency has been a key concern in this field. In our study, we present a method to enhance the concentrating efficiency of an isotropic multilayer circular thermal concentrator by introducing gradient-distributed thermal conductivities or layer thicknesses within the multilayer circular structure. Our goal is to identify the optimal structural setup parameters for achieving enhanced thermal concentrating efficiency using an optimization approach that combines stepwise refinement search with machine-learning predictions. Initial investigations explore the impacts of different gradient schemes on thermal concentration performance. The gradient distribution function with high thermal concentrating efficiency is established through the stepwise refinement search strategy and the machine-learning model. Subsequently, a detailed search process is carried out in small increments, followed by finite element simulations to validate the thermal concentrating efficiency and ascertain the optimal design parameters of the thermal concentrator. Our findings reveal that the optimally designed gradient thermal concentrator showcases an 8.56 % increase in thermal concentrating efficiency compared to a single-layer structure without gradients. Moreover, applying the gradient function to the outer and inner rings elucidates the inherent influence of the inner and outer layered ring structures on thermal concentrating efficiency. The optimization methodology, combining stepwise refinement search and machine-learning predictions, succeeds in improving the efficiency with easy, fast and efficient operation. This approach can be extended to advance the development of various other thermal metastructured devices.

Adsorption behavior and mechanism of NH2-MIL-101(Cr)@COFs@SA composite adsorbent for tetracycline removal

Herein, we employed a rational approach to develop a hydrogel composite material by encapsulating NH2-MIL-101(Cr)/covalent organic frameworks (COFs) in sodium alginate (SA) to effectively capture of tetracycline (TC). Experimental tests and various characterizations (including Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron spectroscopy (SEM), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS)) confirmed that the NH2-MIL-101(Cr)@COFs@SA composite exhibited a more robust, multilayer pore structure with abundant active functional groups. Under conditions of 298 K and pH = 7, the NH2-MIL-101(Cr)@COFs@SA adsorbent demonstrated remarkable TC adsorption capability, achieving a removal rate of 96.38 % in 120 min and a qmax of 252.6 mg/g at 298 K by Langmuir model. Kinetic analysis indicated that the interaction between TC and NH2-MIL-101(Cr)@COFs@SA follows a pseudo-second-order model, suggesting that chemisoption governs the process. The Langmuir model and thermodynamic analysis suggested that TC adsorption follows a monolayer sorption pattern and is spontaneous and exothermic. Even in the presence of other ions, NH2-MIL-101(Cr)@COFs@SA maintained high efficiency for TC adsorption, demonstrating superior selectivity. NH2-MIL-101(Cr)@COFs@SA demonstrated remarkable recyclability, with only a minimal reduction in the removal efficiency (85.5 % and 142 mg/g) after 10 cycles of adsorption and regeneration. Various analytical techniques, including FTIR spectroscopy, SEM, EDX, XPS, and density functional theory (DFT) calculations of adsorption energy were used to elucidate the TC adsorption mechanisms by NH2-MIL-101(Cr)@COFs@SA. The adsorption process primarily involved π-π stacking, hydrogen bonding, electrostatic interactions, and complexation.

Plasticity analysis and a homogenized constitutive model of compressible multi-layer structure of battery

A homogenized constitutive model for the compressible multi-layer structure of battery (CMLSB) under external loading is essential for optimizing the structural design of electric assemblies. Currently, there is no specific constitutive model that is both mechanically explanatory and operationally applicable to CMLSB under varied loading conditions. In this study, due to limited understanding of the in-plane behavior of CMLSB, an analytical model was developed to investigate plasticity in this specific direction using the strain probing method. The observed plastic characteristics inspired the formulation of a novel two-dimensional constitutive framework for CMLSB in the in-plane direction.By integrating this new constitutive framework with one-dimensional plastic descriptions, a hybrid constitutive model was introduced and implemented in finite element software. Calibration and validation of the model were performed using a commercial pouch cell battery and its segments under various loading conditions. Finite element simulations with the hybrid model demonstrated remarkable accuracy in predicting the mechanical behavior of the cell under various in-plane and out-of-plane compression scenarios. Additionally, simulations were carried out to analyze the impact of cell packaging and air pressure. The new hybrid battery model is considered a user-friendly, physically interpretable, and high-fidelity tool, poised to significantly facilitate the comprehensive design of electric devices.

Exploration of Unconventional excitation wavelength and dynamic emission in rare-earth doped multilayer core-shell Structures: Application for optical “Hard” and “Soft” switching

Optical switches are increasingly acknowledged for their potential advantages over mechanical counterparts in various domains. However, research on optical switches remains relatively nascent, primarily focusing on applications like anti-counterfeiting, switching chemical reactions, etc., while neglecting the control of photocurrent switching. Here, we have developed NaYF4:30 %Er-NaYF4-NaYF4:20 %Ho-NaYF4 core–shell nanocrystals with unique upconversion (UC) multi-color emission properties under 1530 nm, 980 nm and 1150 nm laser excitations. These nanocrystals allow for optical control of circuit switching by modulating photocurrent signals in photosensitive circuits. The UC emission is due to the self-sensitization of rare earth ions in the core and shell. By adjusting the intermediate shell thickness, we have optimized the luminescence and investigated the mechanism. Combining these nanocrystals with a WO3 quantum dots (QDs) photochromic hydrogel, dynamic variation of UC emissions could be realized. Moreover, by combining with a commercial silicon photodetector, we constructed a photosensitive circuit demonstrating the modulation of photocurrent signal output and realized the “hard switching” of rapid circuit cutoff. Furthermore, by using the photochromic effect of WO3 QDs, the “soft switching” of slow circuit cutoff and recovery were also achieved. This work has significant implications for the development and application such as energy management system and smart home of optical switches in various fields.

Multiscale topology optimization of anisotropic multilayer periodic structures based on the isogeometric analysis method

Multiscale topology optimization of anisotropic multilayer periodic structures based on the isogeometric analysis method

Chemical vapor deposited TiCN/TiC multilayer coatings: On the interplay between coating architecture and mechanical properties

Modifying the architecture from a monolithic to a multilayered structure allows adjusting the mechanical properties and cutting performance of industrially relevant hard coatings. The present work focuses on the microstructural, micro-mechanical and cutting performance evaluation of a multilayered TiC0.67N0.33/TiC coating grown by chemical vapor deposition. Energy dispersive X-ray spectroscopy and atom probe tomography confirmed the presence of individual TiC and TiC0.67N0.33 layers of ∼120 nm thickness with well-defined interfaces. The overall C/(C + N) ratio of the coating amounts to 0.82. Individual peaks for the TiC0.67N0.33 and the TiC layer can be observed in the X-ray diffractogram of the TiCN/TiC coating. Scanning electron microscopy showed that the grains grow through the interfaces between the TiCN and TiC layers. Finally, the micro-mechanical properties and cutting performance of the TiCN/TiC multilayer were compared with a monolithic TiCN coating. The fact that the TiCN/TiC coating outperformed the monolithic reference TiCN in regard of hardness and cutting performance emphasizes the high potential of multilayered coatings for use in demanding applications.

Методы монохроматизации синхротронного излучения (обзор исследований)

The paper presents an analysis of studies related to the monochromatization of X-ray radiation (XR) at synchrotron radiation sources. A review of monochromators based on of X-ray diffraction on crystals is given, and the peculiarities of their technical realization are considered. The ideas about monochromators which include multilayer structures are examined. The authors also study technical problems arising during designing devices and its possible solutions. Introduction. The possibilities of using X-rays in scientific research are described. The high efficiency of synchrotron radiation sources is noted, and its characterization is given. Elementary information about diffraction of X-rays. The paper describes the properties of X-ray radiation and the possibilities of its using while studying various materials. Degree of monochromaticity. The degree of monochromaticity is an important characteristic of the synchrotron radiation (SR). Depending on the width of the wavelength band, “white”, “pink” and monochromatic beams are distinguished. Monochromators based on multilayer structures are used to obtain “pink” beams. Monochromatic radiation is formed using monocrystals. When conducting experiments with “white” beams, the monochromator is not used. The authors also describe the factors that violate the ideal fulfillment of the Wolf-Bragg condition and affect the degree of monochromaticity (heat, vibration). The reflectivity values at different beam grazing angles are noted to have different widths. Monochromators based on multilayer structures. Periodic structures combining thin layers of two heterogeneous materials make it possible to obtain “pink” beams. The wavelength bandwidth of such devices is one or two orders of magnitude greater than that of monochromators using crystals as optical elements. Configurations and geometry of optical elements. There are two types of X-ray diffraction on a crystal: Bragg and Laue diffraction. Bragg diffraction refers to reflective geometry, Laue diffraction is based on the passage of beams through the crystal. The section provides examples of monochromators with different configurations of crystals and X-ray mirrors. The arrangement of optical elements in a monochromator plays an important role in the geometry of the beam path. When designing monochromators, it is necessary to take into account the methods of fixation and orientation of the rotation axes of optical elements. Examples of monochromators with different configurations of crystals and X-ray mirrors are given. Focusing monochromators. It is possible to provide sagittal and meridional types of deformation by bending the optical element of the monochromator. Due to the curved crystal surface the beam is not only monochromatized but also subjected to focusing. Modern focusing monochromators are equipped with adaptivity elements allowing it to change the radius of curvature of the optical element. Examples of practical realization of such monochromators are presented. Thermal load of SR on optical elements. The SR is characterized by high brightness and a wide spectrum of emitted wavelengths. While operating optical elements of SR stations absorb a large amount of thermal power. The problems of heat dissipation have a fundamental influence on the quality of synchrotron radiation monochromatization. Additional information about monochromators. Examples of special design solutions for monochromators are given. Conclusion. The design of monochromators is relevant to the synchrotron radiation source 4+ “SKIF” under construction in Novosibirsk.

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

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

Experimental study on combustion characteristics of engineered bamboo considering smoldering and self-extinction

Bamboo and wood materials have the characteristics of low carbon and high strength, making them the best building material for building green buildings. Compared to traditional building materials, the easy to burn characteristic has become an obstacle to the promotion and widespread application of bamboo and wood materials, so it is urgent to study their combustion characteristics. This article investigated the combustion characteristics of engineered bamboo at different heat fluxes, taking into account the smoldering and self-extinction characteristics through cone calorimeter experiments. The combustion performance, mass loss rate, heat release rate, etc. were studied, and the self-extinction phenomenon of the specimens was explored. The results indicated that the direction of heating had a certain impact on the combustion characteristics of glued laminated bamboo (LBL), and the fire resistance of parallel strand bamboo (PSB) was better than that of LBL. When the heat flux exceeded 50 kW/m2, the color of the flame on the surface of the specimen would change from bright yellow to strong orange, which is an important sign that the flame will self-extinguish. The self-extinction of flames at different heat fluxes was caused by insufficient supply of combustible gas generated by bamboo pyrolysis, with slightly different specific reasons. The multi-layer structure of glued laminated bamboo also makes it more difficult to self-extinguish than PSB, cross-laminated timber (CLT), and solid wood is the most prone to self-extinguish. The impact of adhesive layer delamination was not considered in this experiment, and further research is needed.

Enhancement of tribological performance of PTFE/aramid fabric liner under high-temperature and heavy-load through incorporation of microcapsule/CF multilayer composite structure

Liners suffer from low service life under high-temperature and heavy-load conditions, hindering their widespread use in aerospace applications. A novel strategy of incorporating polyaryl ether sulfone/polymethylphenlsiloxane (PES/PMPS) microcapsules and carbon fibers (CFs) into the polytetrafluoroethylene (PTFE)/aramid fabric liner was used. At the micro-scale level, the worn surface morphology and the transfer film morphology were analyzed to reveal the tribological mechanisms. At the nano-scale level, molecular dynamics simulation was used to analyze the formation mechanism of the transfer film. The results showed that the friction coefficient and wear rate of the liner with microcapsule/CF multilayer structure were reduced by 17 % and 24 %, respectively. The incorporation of microcapsule/CF multilayer structure can be effectively applied to enhance the tribological performance of liners in harsh operating conditions.

Enhancing nitrogen and phosphorus removal in plant-biochar-pyrite stormwater bioretention systems: Impact of temperature and high-frequency heavy rainfall

Global climate change and rapid urbanization have resulted in more frequent and intense rainfall events in urban areas, raising concerns about the effectiveness of stormwater bioretention systems. In this study, we optimized the design by constructing a multi-layer filler structure, including plant layer, biochar layer, and pyrite layer, and evaluated its performance in nitrogen (N) and phosphorus (P) removal under different temperatures (5–18 °C and 24–43 °C), rainfall intensity (47.06 mm rainfall depth), and frequency (1–5 days rainfall intervals) conditions. The findings indicate that over 775 days, the plant system consistently removed 62.3% of total nitrogen (TN) and 97.0% of total phosphorus (TP) from 103 intense rainfall events. Temperature fluctuations had minimal impact on nitrate nitrogen (NO3−-N) and TP removal, with differences in removal rates of only 1.0% and 0.6%, respectively, among plant groups. Across the multi-layer structure, plant roots mitigated the impact of temperature differences on NO3−-N removal, while high-frequency rainfall fluctuated the stability of NO3−-N removal. Dense plant roots reinforced N and P removal by facilitating denitrification in the vadose zone (biochar) and strengthening denitrification processes. Biochar and pyrite contributed to stable microenvironments and diverse ecological functions, enhancing NO3−-N and PO43− removal. In summary, the synergistic effects of the multi-layer filler structure improved and stabilized N and P removal, providing valuable insights for addressing runoff pollution in bioretention systems amidst rapid urbanization and climate change challenges.

Conductivity and corrosion resistance of TiSiC/MeN multilayer films

TiSiC/MeN (where Me represents Zr, Ti, and Cr) multilayer films were deposited onto 316LSS substrates for proton exchange membrane fuel cells via magnetron sputtering. A comparative investigation of the microstructures and corrosion resistances of the films was conducted. The results indicate that the incorporation of the MeN interlayers interrupts the continuous growth of the columnar TiSiC layer. The TiSiC/MeN multilayer coated 316LSS exhibits better resistance to corrosion and higher electrical conductivity compared to the TiSiC monolayer. The film porosity dominates the corrosion resistance while the electrical conductivity depends on both the phase structure and oxygen concentrations of the films. The multilayer structure suppresses ion diffusion in the etchant solution and decreases the film porosity. However, interfacial delamination caused by the interaction of the solution with the substrate produces the failure of the monolayer TiSiC.

Sodium into γ-Graphyne Multilayers: An Intercalation Compound for Anodes in Metal-Ion Batteries.

The bulk synthesis of γ-graphyne has been recently achieved and evidenced a multilayered structure, which suggests its potential exploitation as a substitute of graphite-based anode materials for metals heavier than lithium (Li). In fact, each of its regular pores of sub-nanometric size features an optimal environment for hosting a single sodium (Na) ion, as reported here by means of accurate electronic structure calculations. We show that the graphyne/Na ion coupling mimics that found on the graphene/Li ion in terms of metal-single layer interaction and equilibrium distance. More importantly, in contrast to what is found for graphite, we demonstrate that graphyne intercalation compounds with Na are thermodynamically stable and feature an optimal storage capacity of 372 mAh·g-1. These findings, together with a limited crystal structure expansion upon Na intercalation, a low metal diffusion barrier as well as high electrical conductivity, pave the way to the development of novel graphyne-based anodes for efficient Na-ion batteries.