Three-layer Structures Research Articles

Epoxy/ferrite nanocomposites as microwave absorber materials: effect of multilayered structure

In the present work, different ferrite-type nanoparticles (Ni0.5Zn0.5Fe2O4, NiFe2O4 and Fe3O4) were incorporated into an epoxy resin to obtain composites loaded with 20 and 40 wt% of filler. The morphology of these monolayered composites was investigated by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), which allow identifying a fractal structure of the ferrite-based filler with rough surface. The electromagnetic properties of the monolayer composites with 1 mm thickness were evaluated by the transmission line method in X-band (8.2–12.4 GHz), whose better response in terms of reflection loss was obtained for the composite filled with Ni0.5Zn0.5Fe2O4. Epoxy-based composites containing 20 and 40 wt% of Ni0.5Zn0.5Fe2O4 in the form of plaques were arranged in two types of three-layered structures: (i) stacked monolayers and (ii) low dielectric spacer sandwiches between monolayers (air, honeycomb and foam), whose structure sequence was built based on the reflectivity simulation. The best system, designed by mathematical simulation and experimental results, consisted of ER/NiZn(40)–honeycomb–ER/NiZn(20) arrangement, which presented RL of around − 40 dB at a frequency of 8.75 GHz. Broadband with > 90% attenuation (minimum of − 10 dB) with band width of around 1.2 GHz and minimum RL ≈ 20 dB (Eabs ≈ 99%) was achieved for both three-layered structures contain in PU foam or honeycomb as low dielectric spacer. The ferrite-based multilayer structures with only 6 mm of thickness constitute promising absorbing materials for applications in both civil and military fields.

High-contrast optical microscopy of graphene sheets.

In the way of making graphene an industry-friendly material, it must be mass-produced with high-quality and reduced cost over large areas. Assisted by machine-learning techniques, rapid, nondestructive and accurate determination of large graphene sheets on SiO2 /Si substrates has been made possible in recent years by the optical microscopy method. Optimization of the substrate to achieve the maximum contrast can further extend the application of the optical microscopy method for quality control of the mass-produced graphene. Graphene/n2 /n3 three-layer structures, where n2 and n3 are refractive indices, are routinely used for identifying the number of graphene layers by optical reflection microscopy. In this paper, two analytical equations are derived that can be easily used for high-contrast optical imaging of graphene sheets without any need to resort to the cumbersome numerical methods. One of the equations is derived for choosing the best material with refractive index n2 that when coated on a substrate with refractive index n3 , maximizes the optical contrast. The other equation is derived for finding the best thickness of the SiO2 layer in graphene/SiO2 /Si structures, which are in common use for fabrication of graphene-based devices. The results are implemented in a MATLAB GUI, see Supporting Information, to assist the users in using the equations.

Influence of contact layers on cracking resistance of bending three-layer structures

Introduction. In the present-day construction practice, multilayer building envelopes are applied; their layers are made of concretes having different physical and mechanical characteristics. When different concretes are poured in successive layers, contact layers are formed; their physical and mechanical properties are unlike those of the adjacent layers. The strength and stress-strain characteristics of the contact layers can affect the behaviour of a multilayer structure.
 Materials and methods. Numerical and experimental methods are applied to study the stress-train state of such structures exposed to loading. Bending three-layer structural models, having external layers made of strong structural concrete and the middle layer made of low-strength concrete, were applied in the research project. A contact layer is formed in the process of their manufacturing; its geometrical, strength and stress-strain characteristics are simulated in the process of numerical studies.
 Results. The co-authors have identified the effects produced by geometrical, strength and stress-strain characteristics of contact layers on the analysis of bending multilayer structures. Design models and a novel method of analysis have been developed for bending multilayer reinforced concrete structures with account taken of the influence of geometrical, strength and stress-strain characteristics of the contact layer. According to the results of numerical calculations, differences between cracking moments can reach 4.3 % or more for three-layer reinforced concrete beams. As for the practical calculations, if the thickness of the contact layer is below 0.4 cm, one can ignore the influence produced by the contact layer on the calculation result.
 Conclusions. The results of the research help to identify the rational parameters for the design of multilayer enclosing structures having varying strength reinforced concrete layers interconnected by the monolithic contact layer.

Natural dyes in hybrid chalcogenide multi-layer thin films

New highly photoconductive hybrid multi-layer semiconductors have been developed, comprising cathodically electrodeposited CdSe or $${\hbox {Zn}}_{x} {\hbox {Cd}}_{1-x} \hbox {Se}$$ thin films and natural photosynthetic pigments, isolated from spinach. A layer of the organic dye, Chlorophyll $$\alpha $$ or Carotenes, is either deposited by spin coating technique over an inorganic thin film (two-layer structures) or ‘sandwiched’ between two inorganic semiconductive films (three-layer structures). X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, diffused reflectance spectroscopy and photoelectrochemical studies are employed, in order to fully characterize the received products. In the case of the three-layer hybrids, a significantly enhanced photo-response is observed, leading up to 300% improved photoelectrochemical efficiency values, compared to that of the pure inorganic films. This amelioration, stemming from the synergetic action of hybrids’ components, is more prominent in the case of $${\hbox {Zn}}_{x} {\hbox {Cd}}_{1-x} \hbox {Se}$$ systems, where a significant amount of Cd has been substituted by Zn: therefore, Zn are considered environmentally friendlier alternatives to pure CdSe-based semiconductors.

Shoe-Integrated, Force Sensor Design for Continuous Body Weight Monitoring.

Traditional pedobarography methods use direct force sensor placement in the shoe insole to record pressure patterns. One problem with such methods is that they tap only a few points on the flat sole under the foot and, therefore, do not account for the total ground reaction force. As a result, body weight tends to be under-estimated. This disadvantage has made it more difficult for pedobarography to be used to monitor many diseases, especially when their symptoms include body weight changes. In this paper, the problem of pedobarographic body weight measurement is addressed using a novel ergonomic shoe-integrated sensor array architecture based on concentrating the applied force via three-layered structures that we call Sandwiched Sensor Force Consolidators (SSFC). A shoe prototype is designed with the proposed sensors and shown to accurately measure body weight with an achievable relative accuracy greater than 99%, even in the presence of motion. The achieved relative accuracy is at least 4X better than the existing state of the art. The SSFC shoe prototype is built using readily available soccer shoes and piezoresistive FlexiForce sensors. To improve the wearability and comfort of the instrumented shoe, a semi-computational sensor design methodology is developed based on an equivalent-area concept that can accurately account for SSFC’s with arbitrary shapes. The search space of the optimal SSFC design is shown to be combinatorial, and a high-performance computing (HPC) framework based on OpenMP parallel programming is proposed to accelerate the design optimization process. An optimal sensor design speedup of up to 22X is shown to be achievable using the HPC implementation.

Superhydrophobic coating fabricated by electrophoretic deposition using polydimethylsiloxane-based organic–inorganic hybrid materials and ceramic powders

Superhydrophobic surfaces have important applications in daily lives as well in various industries. In this study, composites with superhydrophobic surfaces were fabricated from polydimethylsiloxane-based hybrid materials and ceramic nanopowders by electrophoretic deposition. Under different appropriate conditions, such as the amount of a particular component, the composite possessed a three-layered hierarchical surface. The fabricated composite films comprising three-layered hierarchical structures exhibited contact angles greater than 160° and contact angle hystereses as well as sliding angles less than 5°.

Broadband Terahertz Near-Perfect Absorbers.

Broadband terahertz (THz) absorbers are highly desired in detection, modulation, receiving, and imaging devices. We report the design and successful implementation of a novel broadband THz metasurface with a near-perfect absorption. Different from the traditional metal/dielectric/metal three-layer structures, the as-designed THz absorber has one more metal layer and a dielectric spacer on top, both of which are 200 nm thick. Although the total thickness increased by ∼7%, the near-perfect THz absorption band significantly broadened by 4×, achieving a broadband absorption of 270 GHz. Broadband, polarization-insensitive, and near-perfect THz absorptions were also observed over wide incident angles in these meta-absorbers, where the electric field and power loss were mainly concentrated in the additional thin dielectric layer. Such a broadband THz absorption was achieved through electromagnetic coupling between the top and middle metal layers and the resultant overlapping of the resonance frequencies. This strategy can be adapted to other spectrum-shaping devices.

Impacts of operational parameters on the morphological structure and uranium bioleaching performance of bio-ore pellets in one-step bioleaching by Aspergillus niger

The impacts of operational parameters on the morphological structure and uranium bioleaching performance of the bio-ore pellets obtained in one-step bioleaching by Aspergillus niger were investigated. The uranium recovery of over 80% was achieved under the optimized conditions. Furthermore, the morphological changes of ore particles before and after bioleaching were characterized by scanning electron microscope. The results showed more reactive surfaces were generated by the wrap and adherence of mycelia and the corrosion of metabolites. Finally, the three-dimensional structures of bio-ore pellets were detected by X-ray full-field nano-computed tomography. The results showed the bio-ore pellet structures could be classified into one type of bilayer structure and two types of three-layer structures. The bio-ore pellets with bilayer structure that the mycelia and ore particles were evenly distributed presented preferable uranium bioleaching capability.

Theoretical Study of Electronic Properties of Nanostructures Composed of Blue Phosphorene and Graphene Sheet

In this study, structural and electronic properties of the single-layer structure of Graphene, the single-layer structure of blue Phosphorene, the two-layer structure of blue Phosphorene/Graphene, the three-layer structure of blue-Phosphorene/Graphene/blue-Phosphorene and the three-layer structure of Graphene/blue-Phosphorene/Graphene have been investigated. The calculations are conducted based on the density functional theory (DFT) and using SIESTA code and generalized gradient approximation (GGA). The results show that the single-layer structure of Graphene reveals quasi-metallic behavior, and the single-layer structure of blue Phosphorene exhibit semiconducting behavior. Two - and three-layer structures of Graphene and blue Phosphorene have a metallic behavior. Total energy and structural stability have also been investigated.

Comparison of Ash Layer Formation Mechanisms on Si-Containing Bed Material during Dual Fluidized Bed Gasification of Woody Biomass

Quartz, feldspar, and olivine are minerals commonly used as bed materials for dual fluidized bed gasification of biomass. During their interaction with biomass ash, the materials develop surface layers rich in ash-derived elements. These layers decrease the concentration of tar which is an unwanted side product of gasification. The interactions of quartz, feldspar, and olivine with woody biomass ash leading to the formation of active layers were studied with X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy, and iime-of-flight secondary ion mass spectrometry, and the results were compared to calculations done with FactSage. It was found that the interaction causes the formation of three-layered structures for all materials: a Mg-rich surface layer, a Ca-rich intermediate layer, and an inner layer which varies among the three materials. For quartz and feldspar, the integration of Ca and Mg into the structure causes a transition by depolymerizing the tectosilicate structure via an inosilicate intermediate to finally a nesosilicate. As the olivine structure is a nesosilicate from the beginning, no further depolymerization of the silicate structure can occur and a substitution of Mg by Ca occurs, leading to an accumulation of expelled MgO on the surface. The interaction of the materials with K was found to differ, causing melt formation for quartz, a substitution of Na-rich feldspar by K-rich feldspar, and the formation of feldspathoids for alkali feldspar, or retention as a separate phase for olivine.

Heat-Insulating Properties Of Effective Light Weight Concretes For Three-Layer Protecting Coverings Of Buildings

Аt present, an intensive change in the structure and materials of building envelopes is taking place in order to increase the energy efficiency of buildings, as well as to improve their appearance and extending the period of maintenance-free operation. The paper presents the results of studies of the physical-mechanical properties of light polystyrene concrete and effective heat-insulation of three-layer structures based on heat-insulating light and structural heavy concrete. To obtain the concrete mixture, Portland cement, granular foam polystyrene, polycarboxylate super-plasticizer, quartz sand and limestone crushed stone were used. All raw materials were of local origin (Vietnam). The composition of the heavy and light concrete mixture was calculated using the absolute volume method according to the standard of Vietnam, the thermal conductivity of concrete was measured with an appropriate device. It has been established that using local surface components it is possible to obtain structural concrete, as well as polystyrene concrete, which has sufficient tensile and tensile strength during bending and heat conduction in the dry state. From the calculations made with the use of the computer program, it follows that the three-layer reinforced concrete coating slab, consisting of heavy and polystyrene concrete, has better thermal insulation properties compared to a coating of the same thickness of solid and perforated structural concrete, as well as with a panel with foam polystyrene blocks.

Comparison of radome sandwich composite structures with finite element method

Today, composite sandwiches are used in almost all areas. One of the areas of use are radomes that protect the antenna structures from external effects. The sandwich composites used in radome structures generally consist of the monolayer, two-layer, three-layer (A-type radomes) and five-layer (C-type radom) structures. The number of layers and the materials to be used vary according to the mechanical requirements. This paper presents the results of the design and analysis of radomes made from three-layer and five-layer sandwich composites. The design starts with choosing the convenient material to satisfy the necessary service conditions such as electromagnetic radiation transparency and hydrostatic pressure. Two different design is considered for the analyses which are the three-layer structure was laid in a glass fabric-foam core-glass fabric configuration, and the five-layer structure was laid in a glass fabric-foam core-glass fabric-foam core-glass fabric configuration. Finite element analyses were performed by using commercial software. Mechanical characterization tests were carried out to provide material input for the ANSYS program. These tests were performed according to ASTM standards. The results of the finite element analyses showed that although both designs showed resistance to the hydrostatic pressure of 7.5 MPa the five-layer sandwich composite structure with two layers of foam was found to have better mechanical strength.

Design and implementation of quality management system for tumor radiotherapy

Objective To design and implement a network-based quality management system for tumor radiotherapy. Methods The system consists of B/S framework-based three-layer structures including the application layer, system service layer and data layer. It utilizes Nutz as the development framework to develop web applications, MySQL as the system database, Java programming language for system development, Tomcat as a system application server for project release and IE, Google and other mainstream browsers to achieve client access server functions. Results The system can support integrated information management and service of quality control institutions at the provincial, municipal and county levels. The functions include procedure management, case management, quality control management, notification announcement, data management and system management, etc. The system has been set up and tested in the cooperation units, and the operation and function are in good condition. Conclusion The system can support the assessment of online quality control, which is conducive to information analysis and sharing, promotes the standardization and normalization of quality control and improves work efficiency. Case management function can monitor the diagnosis and treatment processes of patients, establish continuous electronic record, deliver rational treatment and rehabilitation guidance plan, which play a pivotal role in the evaluation of tumor radiotherapy. Key words: Case follow-up; Web application; Quality control

A Perfect Absorber Based on Similar Fabry-Perot Four-Band in the Visible Range.

A simple metamaterial absorber is proposed to achieve near-perfect absorption in visible and near-infrared wavelengths. The absorber is composed of metal-dielectric-metal (MIM) three-layer structure. The materials of these three-layer structures are Au, SiO2, and Au. The top metal structure of the absorber is composed of hollow three-dimensional metal rings regularly arranged periodically. The results show that the high absorption efficiency at a specific wavelength is mainly due to the resonance of the Fabry–Perot effect (FP) in the intermediate layer of the dielectric medium, resulting in the resonance light being trapped in the middle layer, thus improving the absorption efficiency. The almost perfect multiband absorption, which is independent of polarization angle and insensitivity of incident angle, lends the absorber great application prospects for filtering and optoelectronics.

Bond strength between concrete layers of three-layer concrete structures

Development of the methods for the calculating reinforced concrete structures covers a wide range of issues, including the expansion of the application of new innovative materials such as concrete and reinforcement. In practice, modern construction of multilayer structures is made of concrete with different strengths and it is compulsory to conduct numerical and experimental studies of the bond strength between concrete layers with different strengths. In this study, the influence of some physical-mechanical factors and temporal manufacturing parameters on the monolithic bond of concrete layers of three-layer structures made of concrete with different densities according depending on the sample is considered. An experiment was conducted to evaluate the development of the shear bond strength between two concrete layers of three-layers sandwich concrete. Three-layer samples consist of normal concrete (NC) in the external layers and lightweight concrete (LWC) in the inner layer. The results of the study show that these factors directly affect the monolithic bond of concrete layers in three-layer structures, which are made by concrete of different strengths. The obtained scientific results allow the determination of reasonable parameters to ensure the monolithic bond of concrete layers with different strengths of the 3-layers structure in design and production.

Electrochemical Lithiation and Delithiation of Si(100) Single-crystal Surface

By the electrochemical lithiation of a Si(100) single-crystal substrate, regular quadrangular pyramidal shaped three-layered structures on Si(100) were observed in scanning electron microscopic ima...

Магнитоэлектрический эффект в трехслойных асимметричных структурах в области изгибных мод колебаний

Abstract A theory of the magnetoelectric effect in three-layer asymmetric structures composed of a piezoelectric layer and two magnetostriction layers with opposite magnetostriction signs is presented. The thickness ratio of the layers is obtained, at which this effect is maximum. It is shown that the sign of the magnetoelectric coefficient changes to opposite (with respect to the initial two-layer structure) with an increase in the third-layer thickness. It is established that the magnetoelectric coefficients of the structures with different arrangements of the layers with positive and negative magnetostriction have opposite signs.

Increase of energy performance of residential buildings with enclosing structures made of masonries with application of ceramic blocks

Economy of energy resources in the Russian Federation is currently the urgent national environmental and economic problem as the package of measures providing energy saving has high profitability and environmental safety as compared with energy resources buildup. Therefore, much attention is paid to energy saving for the account of reducing heat loss through the enclosing structures at engineering and construction of residential buildings. Therewith, diverse elements of three-layer wall structures are reducing general reliability thereof at failure probability exposed to various factors. The buildings with the enclosing structures made of hollow porous blocks are slightly behind the three-layer wall structure by specific heat-resistant performance, with the base layer thereof consisting of solid ceramic brick and efficient heat insulation layer. The problem of construction and erection work quality is arising therewith. The heat engineering calculation of monolayer structure made as masonry of 510mm PORIKAM 14.3NF ceramic hollow porous blocks finished on the outside by heat insulation plaster is presented herein. Temperature fields are calculated in Therm 7.4 program. The design diagram for the structure part (cross section of the wall) is being made in the program for this purpose with indication of heat engineering data of the materials and overlaying of boundary conditions in both “inside” and “outside” surfaces. Graphic images of thermal fields and heat transfer are presented by the calculation results. Noncompliance with some regulatory requirements at making construction and erection operations are reviewed and simulated, with the reduced heat transfer resistance of the structures being calculated therewith. Noncompliance with the masonry technology results in increase of heat loss thereby reducing heat efficiency.

Modeling and analysis of three-layer floor slabs made of composite materials

A three-layer composite floor slab is considered, consisting of two external bearing layers made of a multilayer composite material, and a filler layer between the bearing layers made of polystyrene. Relations are given to determine the characteristics of multilayer composite materials with different locations of the base layers of the material. The technique of the optimal arrangement of the basis of the composite material in layers is given. Methodology for calculating three-layer structures consisting of external bearing layers and a filler layer between them. The analysis of the results and prospects of using three-layer composite floor slabs in construction.

Magnetic properties of Fe-Bi films

In the paper the results of experimental studies of film structures in the Fe-Bi system are presented. By the method of electron magnetic resonance, it is shown that for bilayer structures the magnetic state depends on the order of deposition of the magnetic and non-magnetic layers. In the three-layer structures, the effect of exchange bias was found, the magnitude of that depends on the thickness of the bismuth layer.