Design Of Multilayer Structures Research Articles

Current research status of rare earth oxygenated hydride photochromic films

Photochromic material, as an adaptive smart material, has a wide range of applications in smart windows, photoelectric sensors, optical storage, etc. Oxygen-containing rare-earth metal hydride (REH<sub><i>x</i></sub>O<sub><i>y</i></sub>) film, a new type of photochromic material, has attracted the attention of researchers for its efficient and reversible color-changing properties, simple and reproducible preparation methods, and fast darkening-bleaching time. In this paper we review the current research status of structural composition, color change mechanism, and property modulation of oxygen-containing rare-earth metal hydride films. Exposure to visible light and ultraviolet (UV) light can lead the optical transmission of visible and infrared (IR) light to degrade. The photochromic mechanisms can be grouped into four mechanisms: lattice contraction mechanism, oxygen exchange mechanism, local metal phase change, and hydrogen migration mechanism. Currently, performance can be tuned by controlling film morphology, designing chemical components, improving substrate adaptation, multilayer film structure design, etc. Finally, the future research focus of thin film is prospected.

Current Research on Rare Earth Oxygenated Hydride Photochromic Films

Photochromic materials, as an adaptive smart material, have a wide range of applications in smart windows, photoelectric sensors, optical storage, etc. Oxygen-containing rare-earth metal hydrides (REHxOy) films, a new type of photochromic material, have attracted the attention of researchers for their efficient and reversible color-changing properties, simple and reproducible preparation methods, and fast darkening-bleaching times. This paper reviews the current status of research on the structural composition, color change mechanism, and property modulation of oxygen-containing rare-earth metal hydrides films. Exposure to visible and ultraviolet (UV) light triggers a decrease in the optical transmission of visible and infrared (IR) light. The photochromic mechanism can be categorized into four explanations: lattice contraction mechanism, oxygen exchange mechanism, local metal phase change, and hydrogen migration mechanism. Currently, performance can be tuned by controlling film morphology, designing chemical components, improving substrate adaptation, multilayer film structure design, etc. Finally, an outlook on research priorities after thin films is provided.

A Fast Computational Method for the Optimal Thermal Design of Anisotropic Multilayer Structures with Discrete Heat Sources for Electrified Propulsion Systems

This work investigates the effect of the anisotropy on the heat transfer properties of layered composite materials with discrete heat sources, that are used in the power electronics of hybrid-electric propulsion systems. An analytical method, based on closed-form expressions structured on Fourier expansion series, is proposed for the solution of the Laplace’s steady-state anisotropic heat equation. The physical presence of electrical components is replaced by externally applied power sources. The method provides an accurate prediction of the temperature distribution and of the heat transfer across perfect layer-to-layer adhesion or finite conductance interfaces; its use is therefore encouraged for the optimization of composite substrates. Code verification has been employed on test cases for which the analytical solution was available.

Fully 3D printed multi-material soft bio-inspired frog for underwater synchronous swimming

Inspired by the relatively simple morphology of Anura such as Rana Esculenta (a semi aquatic frog), we propose the design, fabrication, characterization of a soft biomimetic robotic frog based on multilayer structural design of Shape Memory Alloy (SMA) and ultra-flexible material. Dual thrust generation approach has been proposed to achieve the synchronous swimming motion of frog, utilizing four SMA (BMF 150) muscle wires. The frog robot is named as Exploratory Frog (EXPOG) and is fabricated using multiheaded 3D printing system. Whereas the body of the EXPOG is printed using polylactic acid (PLA), which is connected with functionally responsive limbs (50 mm length and average 6 mm gradient thickness). Each limb consists of two muscles (SMA-1 and SMA-2). SMA-1 works as the main thrust creating unit, which is powered by 5V, 250 mA whereas SMA-2 creates back thrust force for antagonistic motion. The proposed kinematic model was simulated in COMSOL to verify the surface velocity and vortex generation in water using the frog's strokes. The design motivated from the rigorous modelling and real frog dynamics analysis, enabled the as-developed EXPOG swim synchronously in significant level of consistency with the real frog. Electrical and mechanical characterizations have been performed. Moreover, experimental data was further processed using TRACKER for angle, displacement, and velocity analysis. The EXPOG (weighing 57 g) can swim at different controllable frequencies (0.5 – 2 Hz) which enables it to swim at the speed up to 15 mm/s (0.3 BLS) on the surface of deep water (150 cm) with excellent weight balance.

Compression Experiment and Failure Analysis of Additive Manufactured Multi-Layer Lattice Sandwich Structure

The rapid development of additive manufacturing technology provides a new opportunity for the fabrication and research of multi-layer lattice sandwich structures, and thereby some excellent performances can be further discovered. Based on the manufacturing-experiment-analysis technical route, the failure mode of the additive manufactured aluminum multi-layer alloy lattice sandwich structure under quasi-static compression is systematically studied in this paper. Through the combination of experimental observation and finite element analysis, the complex failure mechanism of the multi-layer lattice sandwich structure is revealed. The results show that the multi-layer lattice sandwich structure under quasi-static compression conditions mainly manifests as a layer-by-layer failure mode of the internal lattice structure, which includes the yield, plastic buckling and material damage. At the same time, in comparison with the force–displacement curve and the structural deformation in the key locations, the analysis accuracy of the finite element model can be verified by the compression experiment. Based on the verified finite element model, the most significant influence of different face panel thicknesses, as well the rod radiuses and tilting angles on the energy absorption (EA) is identified via sensitivity analysis. Furthermore, size factors on the structural EA are revealed. This study can provide a helpful guidance for the design of multi-layer lattice sandwich structures in practical applications.

Self-polarization and energy storage performance in antiferroelectric-insulator multilayer thin films

Antiferroelectrics are famous for their unique electric field-induced phase transition polarization behavior, which have a wide application in the fields of power electronics and electrical engineering. In this work, Al2O3 and PbZrO3 films are chosen as the insulator and antiferroelectric, respectively, and the multilayer thin films are fabricated by chemical solution method. The microstructure and electrical performances are systematically investigated. The results demonstrate that antiferroelectric-insulator multilayer films exhibit remarkable ferroelectricity which may be induced by the self-polarization effect. The constructed PbZrO3/Al2O3 bilayer films accompany an amazing remanent polarization of 43 μC/cm2, and the PbZrO3/Al2O3/PbZrO3 trilayer films possess excellent energy storage performance. The values of recoverable energy storage density of 32.6 J/cm3 and efficiency of 88.1% are obtained for trilayer films annealed at 550 °C, meaning that the design of antiferroelectric-insulator multilayer structure is an effective approach to regulate polarization behaviors and enables the films to have excellent energy storage performances.

Fe2O3-decoration and multilayer structure design of Ti3C2 MXene materials toward strong and broadband absorption of electromagnetic waves in the X-band region

Although strong and effective absorption of electromagnetic waves in the X-band region is of utmost importance for practical applications, it still faces many challenges. In this work, we prepared Fe2O3-decorated Ti3C2 composites via a facile one-step solvothermal route. Scanning electron microscopy micrographs showed that Fe2O3 particles effectively cover the Ti3C2 surface and insert into the Ti3C2 layers. X-ray diffraction patterns demonstrated that the Fe2O3 particles are beneficial for the Ti3C2 delamination. A high attenuation constant and suitable impedance matching enabled wide-range microwave absorption properties; however, the minimum reflection loss was relatively high. To achieve both wide bandwidth and strong absorption, we designed a multi-layered structural absorber. When the thickness was 1.9 mm, the fourfold-layered structural absorber exhibited the optimal absorption properties with the minimum RL value of − 49.68 dB at 9.922 GHz and RL less than − 10.82 dB in the entire X-band region. Therefore, the synthesized multi-layered structural Ti3C2/Fe2O3 composites can be used for practical applications as a high-performance microwave absorber in the X-band region.

НАПРЯЖЕННО-ДЕФОРМИРОВАННОЕ СОСТОЯНИЕ ОСЕСИММЕТРИЧНОГО ИНСТРУМЕНТА

The ways to increase strength and durability of axisymmetric pre-stressed multilayer cylinders were studied in this article. Cold forging dies for extrusion of complex shape parts is an example of such equipment. The process of complex shape part cold extrusion was modeled; the internal contact pressure along the interface between die and forged part is studied. In the result, the design procedure and specialized software were developed to allow automated design of complex multilayer equipment and structures. Several approaches and recommendations are proposed for multilayer cylinders design in order to increase it durability

РЕЗЕРВ АНАЛИТИЧЕСКИХ ПОВЕРХНОСТЕЙ ДЛЯ АРХИТЕКТУРЫ И СТРОИТЕЛЬСТВА

After a period of relative calm in the construction and design of thin-walled large-span shells and network multilayer shell structures, which, according to the world's leading architects, began in the 1980 s, the time has come for the expanded use of spatial structures in the architecture of public and industrial buildings. Less commonly, shells are used in small-sized housing construction: ecological villages, noospheric and bionic architecture. The entire 20th century did not stop research on the development of analytical and numerical methods for analyzing shells for strength and stability, for the creation of new building materials. Geometers have created and studied more than 600 analytical surfaces that can be mistaken for the mid-surfaces of civil and mechanical engineering shells. As a result, by the beginning of the 21st century, architects and engineers had all the necessary tools to continue the traditions of the "golden age of shells". The analysis of problems with the use of new forms in parametric architecture, carried out in the article, showed that more than ten classes of surfaces from their classification have not yet found application in architecture and mechanical engineering. It is assumed that the number of applied classes of surfaces will not expand, and new ideas for the shaping of shells will be based on the use of already well-known surfaces, namely, surfaces of revolution, transfer, umbrella, minimal, ruled and wavy surfaces. Mainly, shell structures will be designed taking into account environmental, energy-saving requirements and transforming structures.

SbD-Based Synthesis of Low-Profile WAIM Superstrates for Printed Patch Arrays

An innovative strategy for the design of low-profile wide-angle impedance matching (WAIM) superstrates to active return loss (ARL) stability of scanned microstrip-printed periodic phased arrays (PPAs) is presented. Towards this end, an instance of the System-by-Design (SbD) paradigm is exploited and a task-oriented formulation of the WAIM synthesis problem is proposed. More specifically, a customized global optimization strategy is combined with an accurate and fast modeling of the array ARL, which is based on a semi-analytical approach, to enable an effective design of multi-layer structures with both isotropic and anisotropic materials. A set of representative numerical examples, concerned with different microstrip patch substrates, lattices, and design constraints, is presented to give the interested readers some insights on the features and the potentialities of the proposed implementation.

Thermoelasticity of multilayered plates with imperfect interfaces

Three-dimensional exact solutions for temperature and thermoelastic stresses in multilayered anisotropic plates are derived for advanced boundary-value problems with general boundary conditions. The extended Stroh formalism is formulated to include the thermal coupling with the Eringen nonlocal elasticity theory that captures small scale effects. The simply supported structures are subjected to time-harmonic distributions of temperature, combined with tractions, which are represented by means of Fourier series expansions. In particular, the prescribed loads on both the bottom and top surfaces include the uniformly and heterogeneously distributed normal stresses, while imperfect thermal and mechanical contacts between constituents are incorporated at the internal interfaces. Recursive field relations for multilayered plates with imperfect interfaces are consistently articulated by virtue of the traditional propagation matrix method, which is further completed by the dual variable and position technique to overcome numerical instability issues. Three application examples are proposed to throw light on various effects of the externally applied loads and internal imperfections on the thermoelastic fields in multilayered structures. The residual stress fields in graphite fiber-reinforced epoxy matrix composites are shown to be drastically different from those predicted by the classical elasticity theory when nonlocal effects are significant. The stacking sequence and the number of copper and molybdenum in laminated anisotropic plates are of great importance in tailoring interfacial properties, especially if the thermally conducting boundaries are taken into account. The forced vibration analysis of thermal barrier coatings on nickel based superalloys is investigated, including interfacial bonding effects between adjoining layers. Depending on the input frequency amplitude, severe oscillating displacements and stresses take place in the single crystal superalloys that can endanger the safety-related stability and integrity of aircraft engines. Overall, the present formalism should be utilized in the optimal design of sophisticated multilayered structures with desired steady-state and time-harmonic thermoelastic responses.

Optimized Design of Multi-layer Nano-photonic Structures for Selective Absorption Applications by Artificial Neural Networks

Data-driven method based on the machine learning provides an efficient tool to optimize nano-structure for the target spectrum applications. Artificial neural network (NN) can be trained with limited samples to approximate the complex physical simulation with the high accuracy. In this work, we use the artificial neural network to approximate the absorbance spectra of multi-layer structure. Results show that the forward design of NN can predicate the spectrum accurately based on the mean square error as the cost function. For inverse design and optimized design processes, the predicted results show great based on the physically realized spectrum. However, the ideal full absorption spectrum or selective absorption spectrum is usually needed for different photonic applications, which is not suitable based on the reverse network. An optimized network based on the forward and inverse network was designed to predicate the ideal selective or full absorption spectra, which provides a way to optimize complex photonic structures for different applications.

Multi-layer light trapping structures for enhanced solar collection.

Light trapping is a commonly used technique for enhancing the efficiency of solar collection in many photovoltaic (PV) devices. In this paper, we present the design of multi-layer light trapping structures that can potentially be retrofitted, or directly integrated, onto crystalline or amorphous silicon solar panels for enhanced optical collection at normal and extreme angle of incidence. This approach can improve the daily optical collection performance of solar panel with and without internally integrated light trapping structure by up to 7.18% and 159.93%, respectively. These improvements predict an enhancement beyond many research level and commercially deployed light trapping technologies. We further enhance this performance by combining our multi-layer optics with high refractive index materials to achieve a daily optical collection of up to 32.20% beyond leading light trapping structures. Our additive light trapping designs could enable the upgradeability of older PV technologies and can be tailored to optimally operate at unique angular ranges for building exteriors or over a wide range of incidence angle for applications such as unmanned aerial vehicles.

Mechanical properties and thermal shock in thin ZrO2–Y2O3–Al2O3 films obtained by the sol-gel method

Thin multilayer coatings of ZrO2–Y2O3–Al2O3 were prepared using the sol-gel method and dip-coating technique in order to advance in the study of what influence the incorporation of Al2O3 has on films of Y2O3-doped ZrO2, investigating its role in the synthesis of the solutions and in the characteristics and properties of the coatings. After the characterization of the solutions used in the process, the microstructure of the films was studied and their mechanical behaviour and resistance to thermal shock were determined so as to optimize the characteristics and functionality of these coatings. With increased alumina content, 3YSZ-Al2O3 (20 mol%), the cubic phase of the zirconia disappeared completely at the sintering temperature used (700 °C), resulting in the tetragonal phase with Al in solution. There was also a decrease in the coatings' hardness and Young's modulus, and an increase in toughness and resistance to thermal shock. These results allow guidelines to be established for the design of multilayer structures that are, tougher, more resistant, and have improved surface properties.

Design of a novel all-carbon multi-layer structure with excellent thermal protection performance based on carbon/carbon composites and carbon foam

In order to obtain high-performance thermal protection materials, a novel all-carbon triple-layer structure was designed by orderly combining high thermal conductivity carbon/carbon composites (HTC-C/C), polyacrylonitrile-based carbon fiber reinforced composites (PAN-C/C) and carbon foam. During exposure to the oxyacetylene torch, compared with the multi-layer structure made of PAN-C/C and carbon foam, the maximum surface temperature of the triple-layer structure was lowered from 2348 °C to 2215 °C, and the mass ablation rate was reduced by 90.0%, attributed to the excellent heat-dissipation performance and the higher anti-oxidation property of HTC-C/C. When compared with the multi-layer structure composed of HTC-C/C and PAN-C/C, the back surface temperature of the triple-layer structure is further decreased by 700 °C, proving the effective thermal insulation of carbon foam; meanwhile, by isolating the air structure of the intermediate layer made of PAN-C/C was protected from oxidation.

Synthesis of Hollow Carbon Microspheres with Tunable Shell Numbers for High-Performance Anode Material in Lithium-Ion Batteries.

In this paper, hollow carbon microspheres (HCMs) with tunable shell numbers were controllably synthesized by the combination of facile hydrothermal method and etching treatment. The microstructure, morphology and electrochemical performance of HCMs were investigated by X-ray photoelectron, spectra SEM and TEM measurements, and galvanostatic charge-discharge tests. The size of HCMs was uniform and increased with increasing the number of inner carbon shells. Compared to the single-layer carbon microspheres and double-layer carbon microspheres, threelayer HCMs (TLCs) with diameters of 310-360 nm exhibited the highest reversible capacity presenting original discharge and charge capacity of 626.04 and 575.68 mAh·g-1 at 0.1 C. Moreover, the capacitance retention reached to 360 mAh ·g-1 and charge-discharge efficiency was still over 97% after 100 cycles. The superior properties of TLCs can be mainly attributed to their unique three-layer hollow structure which can significantly enhance the pore volume and specific surface area, and thus provides more Li-ions reaction sites and larger contact area between electrodes. Furthermore, the design strategy of HCMs is expected to provide a novel guidance for the design of multi-layer carbon structure with improved electrochemical properties.

Numerical simulations on strong coupling of Bloch surface waves and excitons in dielectric-semiconductor multilayers

Simulations on Bloch surface waves and Bloch surface wave–exciton–polaritons based on the transfer matrix method were performed using only the layer thicknesses and refractive indices of the materials. We demonstrate that the incorporation of the influence of active layer is necessary to accurately determine the Bloch surface wave dispersion. Furthermore, the mode splitting that gives rise to the lower and upper polariton branches can be simulated by including the full dispersive refractive index of the active layer in the transfer matrix calculation. We show the dependence of coupling strength on active layer and truncation layer thicknesses, which implies that the Bloch surface wave–exciton interaction strength can be tuned just by changing these structural parameters. Furthermore, we calculate the area inside the dips corresponding to the lower and upper polariton modes, which can serve as an indicator of mode visibility. We find that in the Kretschmann–Raether configuration, a tradeoff between high Rabi splitting and good mode visibility must be taken into account in designing multilayer structures for Bloch surface wave–exciton–polaritons. Angle-resolved reflectivity maps were also calculated to illustrate how these results can be observed in an experimental set-up. This work serves as a guide map in the design and potential optimization of multilayer structures for the study of two-dimensional polaritonic systems.

Improvement in the tribocorrosion performance of CrCN coating by multilayered design for marine protective application

Steel structures significantly degrades owing to tribology and corrosion in aggressive marine environment and is unavoidable. Chromium nitride (CrN) based coatings material has aroused great interest as one of the most promising protective system in the marine equipment or its components. In the present study, we provided insights for the tribocorrosion mechanism of CrN and CrCN monolayers as well as CrN/CrCN multilayered coatings deposited on steel substrates via a multi-arc ion method. Field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) revealed that the design of multilayer structure could interrupt the continuous growth of columnar crystals and making the coating denser. Furthermore, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) results confirmed the CrN/CrCN multilayered coating presented a high content of graphite-like phase and hard Cr-C compounds, which might play a key role enhancing lubrication and hardness. In particular, tribocorrosion tests in artificial seawater showed that the as-deposited CrN/CrCN multilayered coating could demonstrate significant improvement of tribocorrosion resistance compared to the CrN and CrCN monolayers coatings. The corresponded mechanisms were discussed in term of the coatings microstructure and tribocorrosion behaviors.

Design and analysis of multilayered hybrid structures with plasma-metals, dielectrics and contact cascaded gratings for freely resonance manipulation and flexibly filtering

A hybrid structure incorporating plasma-metals, dielectrics and contact cascaded subwavelength gratings, with capabilities of creating desired optically resonance and flexibly filtering behaviors for TE and TM polarizations, is proposed. Its novel capability of resonances of multi-polarizations in spectra, i.e., peak-resonance in reflection and valley-resonance in transmission, is discussed along with complementation in spectra for reflected and transmitted lights. Design principles of it are provided as well as unexpected optically resonance and freely filtering properties. Moreover, a device with functions of both blue-peak-resonance for TE lights and red-peak-resonance for TM lights is designed by it to uncover potentials of flexibly control of resonance for both polarizations. Its novel properties in resonance and filtering are discovered especially influences of its parameters on spectral resonances and color variations for two polarizations. Capabilities owned by the structure of freely manipulation of peak, valley and bandwidth of spectra for both polarizations make it feasible to create artificially structural colors with high quality, unusually dynamic effect and abundantly color variety. The structure together with its related properties has better values of practically application in fields of adornment, security, display, sensing, imaging and encoding, etc.

Free vibrations and supersonic flutter of multilayered laminated cylindrical panels

In the present paper the problems of optimal design of multilayered composite structures subjected to free vibration and supersonic flutter constraints are discussed. The analysis is carried out for laminated flat plates and cylindrical panels with rectangular plan form. The solutions are derived with the aid of analytical and finite element formulations. A special attention is focused on the formulation of fundamental relations for panels with the use of the approximate Donnell-Mushtari-Vlasov shallow shell theory. The structures with different boundary conditions, geometrical parameters, angle-ply fibre orientations, discrete stacking sequences and air flow directions are considered. For discrete fibre orientations a new form of design variables (reduced to four only) is proposed and employed successfully in the optimal design. Both for flat plates and cylindrical panels the maximal values of aerodynamic pressures are obtained for angle-ply laminates, and not for discrete 0°2, ±45°, 90°2 (an even number of layers of the same thickness and mechanical properties) stacking sequences.