Multilayer Structure Research Articles

Effect of surface treatment on oxidation film of 55SiCr spring steel wire

Abstract In this work, the surface pretreatments of 55SiCr spring steel wire rods were conducted using shot blasting and phosphating. After drawing, the steel wire was heated at 950°C × 15 s, followed by oxidation treatment with high-temperature steam or air for 3 seconds, and tempering treatment at 520°C. The effects of different surface treatment methods on the surface oxide film of spring steel wire were studied using stereomicroscopy, SEM, EDS, and XRD. The results showed that the steel wire surface oxide film with phosphating pretreatment was thicker and easy to fall off. The thickness of the oxide film formed by phosphating pretreatment samples increased by 2.1 um (high-temperature steam) and 0.3 um (air) compared to the shot-blasting samples under different oxidation atmospheres. High-temperature steam oxidation treatment significantly increased the thickness of the oxide film by 0.65 um (shot blasting) and 2.45 um (phosphating) under different surface pretreatment conditions. The outer surface of the oxide film turned black with high-temperature steam oxidation treatment and turned yellowish brown with air oxidation treatment. By both above oxidation treatments, the oxide film showed a multilayer structure, with enrichment of Cr and Si on the inner side.

Computations of fields induced in biological tissues by electromagnetic (EM) wave in multilayered structure

The assessment of the fields induced in biological tissue by an electromagnetic (EM) wave is a major issue, not only for its relevance in medical research, but also for its implications on the setting of industrial standards. This paper describes the analysis of electromagnetic (EM) absorption properties of biological multilayered structure. The biological structure comprises three different tissues of skin, fat and muscle. A step-by-step approach for the computation of the EM fields within the multilayered structure is presented. The estimated specific absorption rate (SAR) distribution in tissues due to exposure from plane waves of frequencies 433, 900, 1300, 1800, and 2450 MHz, based on an incident power density 4.5 [mW/cm2], are also presented.

Spin-coating ANF based multilayer symmetric composite films for enhanced electromagnetic interference shielding and thermal management

The demand for flexible composite films with electromagnetic interference (EMI) shielding capabilities is rapidly increasing. Balancing high EMI performance with flexibility and portability has become a critical research focus in practical applications. In this study, an optimized strategy for aramid nanofibers (ANF) films was developed using spin-coating and sol–gel techniques. The resulting film features a smooth surface and excellent mechanical properties. ANF, initially an insulator, was transformed into a conductor through the in-situ polymerization of ion-doped polypyrrole (PPy). Leveraging a multilayer structural strategy, we prepared a symmetric composite film, ANF@PPy-(TA-MXene)-AgNWs-(TA-MXene)-ANF@PPy (PMA), using vacuum-assisted filtration and lamination hot pressing. This film, composed of ANF@PPy (PA) as the matrix, tannic acid (TA) modified MXene, and silver nanowires (AgNWs) as fillers, exhibited multiple shielding mechanisms as electromagnetic wave (EMW) passed through its various layers. This multilayer configuration provides significant flexibility in EMW shielding. Moreover, TA-modified MXene expands the lamellar spacing, enhancing the scattering efficiency of EMWs within the film, and serves as a medium connecting the upper and lower layers. This results in the efficient integration of the multilayer structure, synergistically improving both EMI shielding performance and mechanical properties. When the ratio of PA/MXene/AgNWs was 1:3:1, the film demonstrated optimal properties, including an EMI shielding effectiveness of 70.2 dB, thermal conductivity of 4.62 W/(m•K), and tensile strength of 50.2 MPa. Due to the exceptional EMI shielding and thermal properties of the PMA composite film, it holds great potential for applications in artificial intelligence, wearable heaters, and military equipment.

Plakun Burial Ground: a new discovery of the well-known site based on the results of the aerial lidar and ground penetrating radar research

The article presents findings of complex interdisciplinary researches of a group of sopkas in the Plakun terrain feature. The monument is part of the Staroladozhky archaeological complex located in Volk- hovsky district, Leningrad region, 120 km east of St. Petersburg. The sopkas are one of the main landmarks of the region. They are high steep embankments 11 – 30 m in diameter and 3 – 8 m high. They date back to the 8th – 10th centuries. The ethnicity of their makers is uncertain. Historiographical data suggest that the monu- ment consisted of 6 sopkas divided into clusters 3 embankments each. In 1955, the southernmost sopka was excavated for demolition. In 2022 – 2023, scheduled scientific researches and Russian Science Foundation Grant No. 23-18-00515 implied an aerial laser scanning of the monument territory. The area was scanned at the attitude of 70 – 90 m with a DJI Matrice 300 RTK drone and an L1 LiDAR from a DJI D-RTK ground station. The coordinates are referenced in LCS-47 Zone 2 with Spectra Epoch 50 GNSS receiver and amended by Geospider survey station network. The findings allow to distinguish a range of small hills in two groups of remaining sopkas. The standard presentation of Digital Elevation Model (DEM) clearly distinguishes 5 remaining large rounded embankments and piles of the excavated southernmost one. However, the research matches several relief color gradations. The study combines several DEM copies in QGIS geographic information system. Consequently, it is revealed that the chain of remaining embankments includes 4 rounded elevations. 3 of them resemble ploughed embankments. In 2023, two identified elevations were studied with OKO-2 ground penetrating radar equipped with a probe antenna which radiates 100 and 700 MHz pulses. The research involves gridding the area of the alleged lost ploughed sopkas and one apparent embankment. The profiles of the site were double-scanned. The radargrams reveal common structure features in the hills and sopka such as contrast mound foundations, heterogeneous centers, multi-layered structures and local depressions in the top layer around 0.5 meters thick. The findings suggest that 3 out of 4 hills can be viewed as demolished embank- ments of a sopka burial. The fourth one requires additional research.

Honeycomb Bionic Graphene Oxide Quantum Dot/Layered Double Hydroxide Composite Nanocoating Promotes Osteoporotic Bone Regeneration via Activating Mitophagy.

Abnormal osteogenic and remodeling microenvironment due to osteoblast apoptosis are the primary causes of delayed fracture healing in osteoporotic patients. Magnesium (Mg) alloys exhibit biodegradability and appropriate elastic moduli for bone defects in osteoporosis, but the effect on the local bone remodeling disorder is still insufficient. Inspired by the "honeycomb," layered double hydroxide (LDH) with regular traps with graphene oxide quantum dots (GOQDs) inlayed is constructed by pulsed electrodeposition to generate GOQD/LDH composite nanocoatings on the surfaces of Mg alloy substrates. The honeycomb bionic multi-layer stereoscopic structure shows good regulation of the degradation of Mg alloy for the support of healing time required for osteoporotic bone defect. Within its lattice, the local microenvironment conducive to osteogenesis is provided by both the rescue effect of GOQD and LDH. The osteoblast apoptosis is rescued due to the activation of mitophagy to clear dysfunctional mitochondria, where the upregulation of BNIP3 phosphorylation played a key role. The osteoporotic rat model of femoral defects confirmed the improvement of bone regeneration and osseointegration of GOQD/LDH coating. In summary, honeycomb bionic composite nanocoatings with controllable degradation and excellent pro-osteogenic performance demonstrated a promising design strategy on Mg alloy implants in the therapy of osteoporotic bone defects.

Zygospore formation in Zygnematophyceae predates several land plant traits.

Recent research on a special type of sexual reproduction and zygospore formation in Zygnematophyceae, the sister group of land plants, is summarized. Within this group, gamete fusion occurs by conjugation. Zygospore development in Mougeotia, Spirogyra and Zygnema is highlighted, which has recently been studied using Raman spectroscopy, allowing chemical imaging and detection of changes in starch and lipid accumulation. Three-dimensional reconstructions after serial block-face scanning electron microscopy (SBF-SEM) or focused ion beam SEM (FIB-SEM) made it possible to visualize and quantify cell wall and organelle changes during zygospore development. The zygospore walls undergo strong modifications starting from uniform thin cell walls to a multilayered structure. The mature cell wall is composed of a cellulosic endospore and exospore and a central mesospore built up by aromatic compounds. In Spirogyra, the exospore and endospore consist of thick layers of helicoidally arranged cellulose fibrils, which are otherwise only known from stone cells of land plants. While starch is degraded during maturation, providing building blocks for cell wall formation, lipid droplets accumulate and fill large parts of the ripe zygospores, similar to spores and seeds of land plants. Overall, data show similarities between streptophyte algae and embryophytes, suggesting that the genetic toolkit for many land plant traits already existed in their shared algal ancestor. This article is part of the theme issue 'The evolution of plant metabolism'.

Thermomechanical Analysis of Cement Hydration Effects in Multi-layered Pier Head Concrete: Finite Element Approach

Mass concrete plays a crucial role in infrastructure development, yet its complex thermo-mechanical behavior poses challenges, especially in the construction of multi-layered structures like pier heads. This study investigated the thermo-mechanical behavior of a pier head during its concreting process in three stages, including the influence of temperature differences that impact the thermomechanical balance of the concrete. By utilizing the ABAQUS software, thermo-mechanical analysis was conducted to simulate temperature fluctuations during cement hydration. The model integrates thermal analysis to simulate temperature fluctuations during cement hydration and stress distribution during construction, validated through mesh convergence studies and field data comparison. The mechanical analysis considered concrete properties, temperature variations, and construction phase. Nonlinear material behavior and contact interactions between layers were incorporated to obtain a realistic simulation. The results indicated that a multi-layer system can balance temperatures, reducing thermal stress-induced cracking risks. Furthermore, specific test points within the pier head were assessed, revealing potential internal cracks by comparing thermal stresses to the concrete’s tensile strength. This research offers insight into pier head conditions during construction, highlighting critical stress zones, crack prediction, and construction sequence efficacy.

Quantization of topological edge mode in a one-dimensional photonic crystal heterostructure

The study of topological phases of matter has seen significant advancements in recent years, largely driven by the discovery and exploration of their distinctive topological edge states. Here, we delve into the edge properties of a one-dimensional periodic multilayer structure. The analysis reveals that this system exhibits characteristics akin to the Su–Schrieffer–Heeger model in optics. The theoretical analysis explores the impact of multiple interfaces on the emergence of a topological edge mode (TEM) within the structure. The proposed heterostructure functions as a general beam splitter. Moreover, when the interface is doubled, the heterostructure exhibits two TEM states, resulting from the quantization of an incoming beam into its two equally orthogonal constituents. As the number of interfaces increases, more quantized TEM states occur within the photonic bandgap. Also, it identifies that the quality factor of the original TEM mode at 382.08 THz frequency linearly increases with respect to the number of interfaces. The outcome suggests potential applications in photonic sensors, optoelectronics, and photonic devices, indicating the heterostructure’s pivotal role in advancing these fields.

Aperiodic multilayer masks for M3D mitigation in high- and hyper-NA extreme ultraviolet lithography

As extreme ultraviolet lithography tools with higher image numerical apertures (NAi) are introduced, the range of angles at the multilayer mask stack is also increased. Lithography systems are designed to fulfill the “abbe sine rule,” where NAm is related to NAi by the reduction factor. As a result, increases in NAi will increase NAm. High-NA and hyper-NA systems will be implemented with anamorphic optics, 4× in “X,” and 8× in “Y” to reduce the necessary angles. Even so, hyper-NA masks may see illumination angles as high as 13.4°, up from 10.8° for 0.33 NA. This represents a challenge for maintaining through-angle mask reflection using the current periodic mask multilayer structures. In addition to the reflectance amplitude, the phase of reflected light, which plays an important role in imaging, is also strongly influenced by increasing angles. The propagation of light through each bilayer in the stack imparts a phase shift based on the incidence angle. This is then accumulated over many layers, inducing phase effects, which are unique to each illumination point. This will become especially true for high-NA and hyper-NA mask applications. While adjustments to the multilayer period are sufficient to achieve acceptable reflectance, periodic multilayers may suffer in normalized image log slope (NILS) and image placement error (IPE) metrics as a result of strong oblique multilayer M3D phase effects. In this work, we present a first principles methodology for the systematic reduction of oblique multilayer M3D effects through the use of aperiodic multilayer design. We find that when used for low-k1, hyper-NA patterning NILS is improved by 40+%, while IPE through pitch is similarly improved. Under high-NA conditions, a 5%–25% NILS gain is found alongside the enhanced depth of focus.

Design and investigation of indium tin oxide-based transparent broadband microwave absorbers

This paper presents the design of a novel wideband transparent microwave absorber based on indium tin oxide (ITO). The absorber adopts a multilayer structure, with the top layer composed of a nested square structure made of ITO material, an intermediate dielectric layer of polyvinyl chloride (PVC), and a bottom layer of polyethylene terephthalate (PET) coated with ITO as the reflector. By optimizing structural parameters such as the thickness of the ITO film and the dimensions of the spacer layer, efficient broadband microwave absorption exceeding 90% is achieved within the frequency range of 2.43 to 5.67 GHz, while simultaneously meeting requirements for optical transparency and broadband performance. Simulation experiments and theoretical analyses demonstrate excellent polarization and incident angle stability of the absorber structure. Finally, samples are fabricated using screen printing technology, and free-space testing results are consistent with simulation predictions, validating the feasibility of the design.

Supramolecular-driven construction of multilayered structure by modified hummers method for robust silicon anode

Rational design of nano-structured silicon (Si)-based composites to enhance the structural stability and electrical conductivity is key to developing high-performance lithium-ion batteries. Here, a supramolecular self-assembly strategy is first adopted to prepare Si@rGO composites with multilayered structure through the modified Hummers method. Experimental results demonstrate that Si@SiOx NPs are uniformly distributed in rGO interlayers by supramolecular interaction. In situ Raman results suggest that the multilayer embedded structure can effectively confine the Si NPs and preserve the integrity of the electrode. Theoretical calculations indicate that the imbalanced charge distribution in inner interface shows enhanced dual-interfacial bonding and charge interactions in the Si@SiOx⊂rGO composite, resulting in an interfacial electric-field between Si NPs and rGO for fast ionic and charge migration. The fabricated MSi@SiOx⊂rGO anode with high Si contents (> 60 wt.% Si) exhibits superior Li-ion reaction kinetics (882.4 mAh g−1 at 8 A g−1), durable structural stability (0.031% per cycle capacity attenuation with an average Coulombic efficiency > 99.7%), and low expansion rate. High-mass-loading electrodes show great potential for commercial applications. Full cells assembled with LiCoO2 cathodes also demonstrate outstanding Li-ion storage properties. This work provides insights into the interfacial design of Si@C anodes for advanced Li-ion battery.

Effects of Magnetostatic Interactions in FeNi-Based Multilayered Magnetoimpedance Elements.

Multilayered [Cu(3 nm)/FeNi(100 nm)]5/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/[Cu(3 nm)/FeNi(100 nm)]5 structures were obtained by using the magnetron sputtering technique in the external in-plane magnetic field. From these, multilayer magnetoimpedance elements were fabricated in the shape of elongated stripes using the lift-off lithographic process. In order to obtain maximum magnetoimpedance (MI) sensitivity with respect to the external magnetic field, the short side of the rectangular element was oriented along the direction of the technological magnetic field applied during the multilayered structure deposition. MI sensitivity was defined as the change of the total impedance or its real part per unit of the magnetic field. The design of the elements (multilayered structure, shape of the element, etc.) contributed to the dynamic and static magnetic properties. The magnetostatic properties of the MI elements, including analysis of the magnetic domain structure, indicated the crucial importance of magnetostatic interactions between FeNi magnetic layers in the analyzed [Cu(3 nm)/FeNi(100 nm)]5 multilayers. In addition, the uniformity of the magnetic parameters was defined by the advanced technique of the local measurements of the ferromagnetic resonance field. Dynamic methods allowed investigation of the elements at different thicknesses by varying the frequency of the electromagnetic excitation. The maximum sensitivity of 40%/Oe with respect to the applied field in the range of the fields of 3 Oe to 5 Oe is promising for different applications.

Enhancement of high-frequency harmonics in resonators using multilayered structures with polarity-inverted layers

Periodically Poled Piezoelectric Film (P3F) stacks have recently been reported as a promising platform for next-generation radio-frequency acoustic filters that extend into cm- and mm-wave bands. By demonstrating the potential for developing high-performance acoustic devices with frequencies up to 20 GHz, P3F structures based on lithium niobate (LiNbO3) films have opened up new possibilities. In this study, the influence of key parameters such as the number of layers, crystal orientation, duty factor, and variation in thicknesses between the layers on the efficiency of the n-th harmonic excitation and spurious modes was examined. To enhance higher-order harmonics, which are suppressed in P3F structures, a novel multilayered stack with Aperiodically Polarized Piezoelectric Films (APPF) is proposed. Optimizing the ratio between layer thicknesses can enhance higher-order harmonics. An optimization principle is described and illustrated by examples of three-layered APPF structures optimized for the generation of antisymmetric Lamb wave harmonics A3-A17, with electromechanical coupling continuously decreasing with frequency. High-frequency modes excited in APPF structures fill the gaps in frequencies and electromechanical coupling coefficients between the modes generated in P3F stacks and can provide greater diversity of device performance.

Correlations between adhesion and molecular interactions at buried interfaces of model polymer systems and in commercial multilayer barrier films.

Sum frequency generation vibrational spectroscopy (SFG) was applied to characterize the interfacial adhesion chemistry at several buried polymer interfaces in both model systems and blown multilayer films. Anhydride/acid modified polyolefins are used as tie layers to bond dissimilar polymers in multilayer barrier structures. In these films, the interfacial reactions between the barrier polymers, such as ethylene vinyl alcohol (EVOH) or nylon, and the grafted anhydrides/acids provide covalent linkages that enhance adhesion. However, the bonding strengths vary for different polymer-tie layer combinations. Here, using SFG, we aim to provide a systematic study on four common polymer-tie interfaces, including EVOH/polypropylene-tie, EVOH/polyethylene-tie, nylon/polypropylene-tie, and nylon/polyethylene-tie, to understand how the adhesion chemistry varies and its impact on the measured adhesion. Our SFG studies suggest that adhesion enhancement is driven by a combination of reaction kinetics and the interfacial enrichment of the anhydride/acid, resulting in stronger adhesion in the case of nylon. This observation matches well with the higher adhesion observed in the nylon/tie systems in both lap shear and peel test measurements. In addition, in the polypropylene-tie systems, grafted oligomers due to chain scission may migrate to the interface, affecting the adhesion. These by-products can react or interfere with the barrier-tie chemistry, resulting in reduced adhesion strength in the polypropylene-tie system.

Investigation of mechanical and tribological properties of NiCrAlY/ZrO2-Y2O3 coatings obtained by detonation spraying

In this study, multilayer gradient NiCrAlY/ZrO2-Y2O3 coatings obtained by detonation spraying in 1D (spot sputtering) and 2D (full-surface scanning sputtering) modes were investigated. The structure of coatings was analyzed using scanning electron microscopy and electron dispersion analysis, mechanical properties (hard- ness, modulus of elasticity) were determined using various techniques. The tribological characteristics of the coatings including abrasion resistance and coefficient of friction were also studied. It was determined that the coatings consist of alternating layers of NiCrAlY and ZrO2-Y2O3, creating a multilayer gradient structure. It was found that the NiCrAlY layers act as a bonding element, providing interlayer adhesion, and the ceramic ZrO2-Y2O3 layer serves as a thermal barrier protecting the substrate from high temperature loads. It was found that the coatings in 2D mode have high microhardness compared to coatings in 1D mode. It was deter- mined that the hardness of coatings smoothly increases from the substrate to the surface layers due to the gra- dient increase in the content of ceramic materials. It was found that coatings obtained in 2D mode have better wear resistance and lower coefficient of friction compared to coatings in 1D mode, indicating the greater effi- ciency of coatings in dry friction conditions and their ability to prevent wear of the substrate material.

Multilayer porous poly (vinylidene fluoride)/MXene/cobalt ferrite composites with ternary gradients for electromagnetic wave absorption

A composite material with a high potential for absorbing electromagnetic waves (EMW) was obtained by selecting poly (vinylidene fluoride) (PVDF) as the matrix, MXene as the conductive filler, and cobalt ferrite (CoFe2O4) as the magnetic filler. A layer-by-layer assembly strategy involved hot pressing and sequential blade coating, followed by vapor-induced phase separation, was used to implement the preparation of PVDF/MXene/CoFe2O4 (PMC) composites. The process facilitates the formation of a well-organized multilayer porous framework, providing a gradient of positive conductivity, negative magnetism, and porosity within the composites. Incorporating distinct multilayer, porous, and gradient structures into a single composite led to exceptional impedance matching (Z), with an area percentage of up to 8.4 % in the optimal range of 0.8 to 1.2. Furthermore, the multiple interfaces formed by the various components, multilayer structure, and porous configuration significantly enhanced the EMW attenuation capability, with the attenuation constant reaching as high as 274. Consequently, the PMC composite demonstrated outstanding performance with a minimal reflection loss (RLmin) of −56.5 dB, a specific RLmin of 23.5 dB/mm, and the broadest effective absorption bandwidth of 3.2 GHz. The combination of the competitive EMW absorption capability, low density, flexibility, adequate tensile strength, and amphiphilic Janus surface may significantly broaden the application scenarios of PMC composites.

THE EFFECT OF THE ELECTROLYTE COMPOSITION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STEEL 45 AFTER CATHODIC ELECTROLYTE-PLASMA NITRIDING

This research offers an in-depth exploration of the impact of cathodic nitriding on the structural and mechanical characteristics of 45 steel treated in different aqueous electrolytes. Through a combination of Xray diffraction and electron microscopy analyses, it was determined that the nitriding process facilitates the development of a multilayered surface structure, which includes oxide, nitride, and martensitic layers. The composition of the electrolyte plays a crucial role in determining the phase composition and thickness of the modified layers, directly influencing the steel's mechanical properties, as reflected by variations in hardness and wear resistance post-treatment. Notably, an electrolyte containing sodium carbonate (Na₂CO₃) and urea (CH₄N₂O) achieved a maximum microhardness of 986 HV due to the formation of a dense nitride layer. On the other hand, introducing ammonium nitrate to the electrolyte, while slightly decreasing the microhardness to 882 HV, resulted in the formation of a more intricate and stable phase structure, including additional nitrides and oxides, which contributed to enhanced corrosion resistance. These findings underscore the critical importance of optimizing electrolyte composition to improve the performance characteristics of steel, such as hardness, wear resistance, and corrosion resistance. This study underscores the effectiveness of cathodic nitriding as a method for significantly enhancing the mechanical and surface properties of 45 steel, thereby expanding its potential for use in high-load and aggressive environments.

“Reinforced concrete” design of robust mineralized cellulose composite with multilayered structure for efficient CO2 capture and passive radiative cooling ability

The construction industry promotes the economic development of the country by addressing society's housing needs. However, the industry's energy consumption and carbon dioxide (CO2) emissions are the primary contributors to global warming. Traditional building materials are no longer capable of meeting the requirements of sustainable development, while natural cellulose can be used as a new type of carbon capture construction material. Inspired by the “reinforced concrete” methodology, a mineralized cellulose composite (ML-CCM) was fabricated through a strategy of vacuum filling and in-situ mineralization, resulting in a composite with a multi-level structure (a natural microporous 3D scaffold loofah as “rebar” and cellulose filler as “cement” are staggered in the composite). The resultant ML-CCM1 exhibited a significantly high flexural strain (approximately 215.9 % of that of cellulose composite without loofah) because of the 3D scaffold loofah acting as a “rebar”. Furthermore, the composite possesses flame retardancy, superior thermal insulation at 90 °C, and passive radiative cooling performance due to the micro-nano ZnO particle in the “cement”. Moreover, the multi-level structure, consisting of pores and micro-nano particles, enables it to effectively adsorb CO2 and environment tobacco smoke. As a result, lifecycle assessments underscore the composite's low Global Warming Potential. Therefore, this work reports a promising 3D bio-based composite with CO2 capture for energy conservation and carbon reduction in the construction industry.

Evolution of Atomic-Level Interfacial Fracture Mechanics in Magnesium-Zinc Compounds Used for Bioresorbable Vascular Stents.

Bioresorbable magnesium-metal vascular stents are gaining popularity due to their biodegradable nature and good biological and mechanical properties. They are also suitable candidate materials for biodegradable stents. Due to the rapid degradation rate of Mg metal vascular scaffolds, a Mg/Zn bilayer composite was formed by a number of means, such as magnetron sputtering and physical vapor deposition, thus delaying the degradation time of the Mg metal vascular scaffolds while providing good radial support for the stenotic vessels. However, the interlaminar compounds at the metal interface have an essential impact on the mechanical properties of the bi-material interface, especially the cracking and delamination of the Mg matrix Zn coating vascular stent in the radially expanded process layer. Intermetallic compounds (IMCs) are commonly found in dual-layer composites, such as Mg/Zn composites and multi-layer structures. They are frequently overlooked in simulations aiming to predict mechanical properties. This paper analyses the interfacial failure processes and evolutionary mechanisms of interfacial fracture mechanics of a Mg/Zn interface with an intermetallic compound layer between coated Zn and Mg matrix metallic vascular stents. The simulation results show that the fracture mode in the Mg/Zn interface with an intermetallic compound involves typical ductile fracture under static tensile conditions. The dislocation line defects mainly occur on the side of the Mg, which induces the Mg/Zn interfacial crack to expand along the interface into the pure Mg. The stress intensity factor and the critical strain energy release rate decrease as the intermetallic compound layer's thickness gradually increases, indicating that the intensity of stress and the force of the crack extending and expanding along the crack tip are weakened. The presence of intermetallic compounds at the interface can significantly strengthen the mechanical properties of the material interface and alleviate the crack propagation between the interfaces.

Optimizing CuInSe2 solar cells with kesterite-based upper absorber and back surface field layers for enhanced efficiency: a numerical study

Abstract This study explores the performance enhancement of an innovative multi-layer solar cell structure using the SCAPS-1D (Solar Cell Capacitance Simulator in One Dimension) software. We aim to improve the efficiency of a solar cell structure comprising ZnO/ZnSe/CZTSe/CuInSe2/CZTSSe/Mo by incorporating CZTSe as the upper absorber layer, CuInSe2 as the main absorber layer, and CZTSSe as a back surface field (BSF) layer. Initially, we compare the performance of three different configurations by analyzing their J-V characteristics. For the best performing structure, we further examine the external quantum efficiency (EQE) spectrum. We then evaluate various window (ZnO, ZnMgO, SnO2, Zn2SnO4) and buffer (ZnSe, ZrS2, SnS2, In2S3) materials, identifying ZnO and ZrS2 as the most effective for achieving high current density and efficiency. Through detailed simulations, we determine the optimal thicknesses for CZTSSe (0.2 µm), CZTSe (0.4 µm), and CuInSe2 (3.2 µm). Additionally, by optimizing the acceptor density to 1020 cm−3, we significantly enhance the performance of both CZTSe and CZTSSe layers. Temperature management is shown to be crucial, with the highest efficiency observed at 300 K. As a result of these optimizations, the solar cell structure achieves a remarkable efficiency of 35.38%. Furthermore, we compare our results with existing literature to highlight the advancements made in this study. These findings underscore the importance of material selection and structural optimization in developing high-efficiency solar cells and provide a framework for future advancements in photovoltaic technology.