Single Layer Of Material Research Articles

Vapor and Light Responsive Biocompatible Soft Actuator.

Bioinspired smart polymeric materials that undergo three-dimensional shape deformation in response to specific stimuli have gained significant attention in the field of soft robotics and intelligent devices. Despite the substantial advancements in soft robotics, there is a growing demand for the design of multistimuli-responsive soft actuators using a single layer of material due to its reduced complexity and ease of manufacturing and durability. Here, we report the actuation characteristics of a single-layer, dual-responsive soft actuator that overcomes the commonly encountered delamination issues often associated with bilayer systems by incorporating PEDOT:PSS with cassava starch. This soft actuator exhibits deformations in response to various solvent vapors, such as water, alcohol, and acetone. Remarkably, it demonstrates opposite deformations upon exposure to water and alcohol vapors. Additionally, the actuator responds to light triggers and folds upon exposure to sunlight and infrared light. The degree of folding can be precisely controlled by adjusting the intensity of the light source. Furthermore, the periodic geometric patterns imposed on the surface of the actuator provide an additional handle to control the bending axis. For proof of concept, we leverage the actuation capabilities of our actuator to showcase a range of potential applications, including its usage in wearable textiles, crawler robots, smart curtains, push-and-pull machines, and smart lifts.

Layering Technique of Resin Composite Method for Direct Anterior Teeth Restorations: A New Appraisal

Introduction: Composite resins can be effectively recycled to progress the patient's esthetics concluded minimally invasive, low cost and high clinical presentation managements. The layering techniques of composite resins in different thicknesses, with varying grades of opacity and translucency, permit to create esthetic restorations with dental structures physical appearance. Aim: The intention of the training was to appraise the characteristics, values and approaches of stratification of resins composite materials and to demonstrate these approaches with clinical cases. Materials and method: An electronic search of scientific articles referring to the stratification of composite materials was done using a single medical database. The attention on the choice of keywords as well as the presence and elimination criteria were the directorial elements of the research. All articles were included after the title, the abstract and finally, the full text was checked. Only relevant research has been reviewed. Based on the results, several methods of stratifications have been used in clinical practice. Results and discussion: The concept of natural stratification, anatomical stratification, the stratification of the anterior teeth using a dentine hue and a predefined thickness of enamel, or a single layer of material and the correct placement of pigments and opacities, lead to the achievement of esthetic and predictable direct restorations of nanocomposite resins. Conclusions: Within the limit of this study, it is concluded that, to achieve aesthetic excellence, dentists should understand and apply artistic and scientific principles when layering materials, respecting the optical properties of natural dental structures.

Investigations of the ballistic response of hybrid composite laminated structures

Classic lightweight composite armour systems are usually made of ceramics, metals and fabric laminates separately or combination of two materials to resist a ballistic impact by 7.62 mm projectile. To enhance the ballistic impact resistance, this paper proposes hybrid laminated structures, which are developed through combinations of ceramics, Dyneema, Kevlar and compressed wood. There were twenty-five hybrid ballistic panels manufactured first, which were then subjected to field ballistic tests with 7.62 mm (×39 mm) bullets in a velocity range from 806.0 to 887.5 m/s. Here, five of twenty-five panels successfully stopped 7.62 mm projectile. The results of the ballistic performance, energy absorption, back face signature and failure mode of each type of the composite panels were obtained and examined. The mechanisms of ballistic resistance associated with different hybrid panels designed are investigated and discussed. In addition, analytical models are developed to predict ballistic perforation performance of single material layers and the related hybrid composite structures. The theoretical predictions of residual velocities are compared with the corresponding experimental measurements in a good agreement. These results provide the first-hand data to support further concept design of the hybrid ballistic panels and to validate computer models for optimizing lightweight composite armour.

Structural integrity and mechanical properties of the functionally graded material based on 316L/IN718 processed by DED technology

Additive manufacturing is a one of the most promising technology nowadays that offers the advantages not only in building products of complex shapes but also of complex materials. A complex structure is characteristic for Functionally Graded Composites, which basics, principles and applicability have been widely investigated over the last years. The present study is focused on the detailed investigation of mechanical and structural properties of FGC consisting of stainless steel 316L and Inconel 718 processed by Blown Powder Directed Energy Deposition system. Mechanical properties within single layers and over layers transitions were investigated with the use of tensile tests and fracture toughness tests. Metallographic and fractographic investigations were carried out. Metallographic investigation revealed the differences in the interfaces between single material layers, nucleation processes and subsequent growth of the grains of the used materials. It has been shown that the formation of transition region between deposited single material layers is dependent on the order of material deposition since different deposition parameters are used for certain material. Evaluation of the tensile properties showed that the mechanical properties of a single material layers are in very good agreement regardless of the deposition height. However, the types of interfaces considering to the results of fractographic observations affect the tensile performance of the Functionally Graded Composite. The fracture toughness test results demonstrate changes in the mechanism of crack propagation at the interface between materials with respect to the type of transition. Furthermore, the material layers interfaces turned out to be the weakest points of the Functionally Graded Composite. • A great continuation of the Inconel's grains is observed when deposited on 316 L. • 316 L grains show rare crystallographic traceability when deposited on the IN718. • Tensile properties are in very good agreement regardless of the deposition height. • Material layers interfaces are the weakest points of the functionally graded material. • The crack propagation mechanism in FGC is dependent on interface type.

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

Heat generation and therefore thermal transport plays a critical role in ensuring performance, ageing and safety for lithium-ion batteries (LIB). Increased battery temperature is the most important ageing accelerator. Understanding and managing temperature and ageing for batteries in operation is thus a multiscale challenge, ranging from the micro/nanoscale within the single material layers to large, integrated LIB packs. This paper includes an extended literature survey of experimental studies on commercial cells investigating the capacity and performance degradation of LIB. It compares the degradation behavior in terms of the influence of operating conditions for different chemistries and cell sizes. A simple thermal model for linking some of these parameters together is presented as well. While the temperature appears to have a large impact on ageing acceleration above room temperature during cycling for all studied cells, the effect of SOC and C rate appear to be rather cell dependent.Through the application of new simulations, it is shown that during cell testing, the actual cell temperature can deviate severely from the reported temperature depending on the thermal management during testing and C rate. It is shown, that the battery lifetime reduction at high C rates can be for large parts due to an increase in temperature especially for high energy cells and poor cooling during cycling studies. Measuring and reporting the actual battery (surface) temperature allow for a proper interpretation of results and transferring results from laboratory experiments to real applications.

Evidence that Bacteria Packaging by Tetrahymena Is a Widespread Phenomenon

Protozoa are natural predators of bacteria, but some bacteria can evade digestion once phagocytosed. Some of these resistant bacteria can be packaged in the fecal pellets produced by protozoa, protecting them from physical stresses and biocides. Depending on the bacteria and protozoa involved in the packaging process, pellets can have different morphologies. In the present descriptive study, we evaluated the packaging process with 20 bacteria that have never been tested before for packaging by ciliates. These bacteria have various characteristics (shape, size, Gram staining). All of them appear to be included in pellets produced by the ciliates Tetrahymena pyriformis and/or T. thermophila in at least one condition tested. We then focused on the packaging morphology of four of these bacteria. Our results demonstrated that, as shown previously for Mycobacterium smegmatis, the packaging of Microbacterium oxydans, Micrococcus luteus, and Cupriavidus sp. was formed of a single layer of material. The packaging of Cellulosimicrobium funkei was made of indistinguishable material. A different pellet morphology was obtained for each of the four bacterial strains studied. The ingestion of small bacteria resulted in rounder, denser, and more regular pellets. These results support the idea that bacteria packaging is a relatively widespread phenomenon.

Automatic control for laser-based repair preparation of composites by fiber orientation detection and short coherent interferometry

In automobile and aviation industries, composite materials are the key to lightweight efficiency. Composites containing carbon fiber reinforcements are of particular interest due to their supreme stiffness-to-weight-ratio, but the machining of this material class is still a challenge in production, rework, and repair. Laser technology presents a powerful solution to this obstacle. Laser ablation is a technique that can be utilized for repair preparation of composites. However, for large-scale industrial acceptance, laser processes must incorporate a high degree of automation. In this paper, an approach to fully automatic control of the laser-based repair preparation is presented. It features two process monitoring techniques: fiber orientation detection and short coherent interferometry. Both techniques aim to support the material ablation process by enabling homogeneous material removal to a specific material layer or specified depth. Between laser scanning cycles, a camera-based system scans the processed surface and measures the fiber orientation in each pixel with regard to an adjustable tolerance. When scarfing composite parts made from noncrimped carbon fibers, this technique can be used to detect the transition between two consecutive layers. Areas in the scarfing zone that reveal fibers of the next layer will be excluded from further laser scanning until the current fiber layer is completely ablated. Composite parts reinforced by crimped fabrics are similarly processed, but since single material layers are not easily identified, the ablation process is not controlled by fiber orientation measurements. Instead, short coherent interferometry is used to detect the ablated depth and compare it to the part's ideal layer thickness. Areas in the scarf zone that have reached the desired depth are excluded from further laser scanning. This technique is also applicable to noncrimped fabrics. The results show that when the laser-based repair preparation is controlled by these techniques, precise scarfing can be achieved.

Modifying interlayer space of montmorillonite with octakis(3-(1-methylimidazolium)propyl) octasilsesquioxane chloride

Highly water-soluble material of multi-imidazolium based silsesquioxane cages (material 2) is a promising candidate for modifying clay mineral interlayer space, which is successfully demonstrated by using montmorillonite. The modified montmorillonite can be easily prepared via cation exchange reaction between material 2 and sodium ions of montmorillonite, dispersed in an aqueous solution at room temperature. The modified montmorillonite formed a precipitate within a few seconds. A single layer of material 2 found to be intercalated in the modified montmorillonite with a maximum interlayer space (d-value) of 18 Å (1.8 nm) from 13 Å (1.3 nm) of the unmodified one was confirmed by transmission electron microscopy (TEM) and X-rays diffraction (XRD). Moreover, the percentage uptake and nature of incorporation of material 2 into montmorillonite layers were investigated by thermal gravimetric analyses (TGA), 29Si NMR and FT-IR spectroscopies.

Formation of Complex Craters in Layered Targets With Material Anisotropy

AbstractMeteorite impacts often occur in layered targets, where the strength of the target varies as a function of depth, but this complexity is often not represented in numerical impact simulations because of the high computational cost of resolving thin layers. To address this limitation, we developed a method to approximate the effect of multiple thin weak layers within a sedimentary sequence using a single material layer to represent the entire sequence. Our approach, implemented in the iSALE (impact‐Simplified Arbitrary Lagrangian Eulerian) shock physics code, combines an anisotropic yield criterion with a cell‐based method to track the orientation of layers. To demonstrate the efficacy of the method and constrain parameters of the anisotropic strength model required to replicate the effects of thin, weak layers, we compare results of simulations of an ~20‐ to 25‐km diameter complex crater on Earth using the new method to those from simulations that explicitly resolve multiple thin weak layers. We show that our approach allows for a reduction in computational cost, negating the need for an increase in spatial resolution to resolve thin layers in the target, while replicating crater formation and final morphology from the high‐resolution models. In keeping with field observations, we also find that anisotropic layers may be responsible for a lack of central uplift expression observed at many craters formed in targets with thick sedimentary layers (e.g., the Haughton and Ries impact structures).

High transmission of negative permittivity materials based on strong magnetic field coupling

Materials with negative permittivity are opaque for electromagnetic wave such that the transmitted signal cannot travel through them. To combat this phenomenon, we propose a novel high transmission mechanism using periodic placed split-ring resonators and metallic wires to construct a transparent sandwich structure. This structure consists of three layers of materials, where the material with negative permittivity is sandwiched between the materials with high permittivity. With the given frequency, we firstly exploit the metallic wires and split-ring resonators to attain non-transparent negative permittivity and high permittivity, respectively. By effective medium theory, effective relative permittivity retrieved from these materials’ S parameters is verified to be negative or high. Then a resonant tunneling of electromagnetic fields occurs in the proposed three-layer sandwich structure. Simulated and measured results show that this structure fulfills high transmission, although each single material layer is nearly opaque. In addition, this high transmission mechanism is characterized by strong magnetic field coupling and an optimized coupling distance. The high transmission phenomenon and resonant tunneling mechanism provide an idea of reference to realize perfect transmission through opaque materials, which is also realizable in infrared or optical regimes with appropriate designs.

Thin film mechanical characterization of UV-curing acrylate systems

This study presents the mechanical characterization of UV-curing acrylate systems. UV-curable polymers are commonly used in the stereolithography (SLA) technique to build multi-layered objects. Typically, the mechanical properties of the 3D-printed product are affected by the intrinsic material heterogeneity along the sample thickness. To understand what determines this heterogeneity, single layers of UV-curable polymer are characterized and the effect of process conditions on the mechanical properties is studied. Micro-compression experiments are carried out to determine the intrinsic mechanical properties which are representative of one single UV-cured layer. To determine the right conditions to generate maximally-cured micropillars, the evolution with irradiation time of monomer conversion, glass-transition temperature and yield stress has first been studied. Thereto, micrometer-sized pillars and dog-bone shaped samples have been prepared via UV-curing. Micro-compression measurements on maximally-cured micropillars are performed to study possible size effects. The results reveal that with decreasing pillar size, the yield stress decreases. Tensile measurements are performed on dog-bone shaped samples which have been processed in the same way as compared to the compression samples. These tensile tests show higher yield stress values when compared with compression tests. This size effect can be attributed to the rinsing with acetone during the sample preparation that leads to a removal of monomer from the crosslinked network. As a consequence, in the real 3D-printing process, the mechanical properties will depend on the feature size. In conclusion, a method is presented to determine the mechanical properties of one single layer of material used in the rapid-prototyping SLA process. The experimental procedure we adopted requires only a few millilitres of material and, therefore, is well suited for screening materials under real SLA process conditions.

Automatic Toolpath Generation for Heterogeneous Objects Manufactured by Directed Energy Deposition Additive Manufacturing Process

A heterogeneous object (HO) refers to a solid component consisting of two or more material primitives distributed either continuously or discontinuously within the object. HOs are commonly divided into three categories. The first category has distinct material domains separating the different materials. The second, called functionally graded materials (FGMs), has continuous variation of material composition that produces gradient in material properties. The third category allows for any combinations of the first two categories within the same part. Modeling and manufacturing of HOs has recently generated more interest due to the advent of additive manufacturing (AM) technology that makes it possible to build such parts. Directed energy deposition (DED) processes have the potential for depositing multiple powdered materials in various compositions in the process of creating a single layer of material. To make this possible, tool paths that provide proper positioning of the deposition head and proper control over the material composition are required. This paper presents an approach for automatically generating the toolpath for any type of HO considering the material composition changes that are required on each layer. The toolpath generation takes into account the physical limitations of the machine associated with powder delivery and ability to continually grade the materials. Simulation results using the toolpath generation methodology are demonstrated by several example parts.

Consequences of atomic layer etching on wafer scale uniformity in inductively coupled plasmas

Atomic layer etching (ALE) typically divides the etching process into two self-limited reactions. One reaction passivates a single layer of material while the second preferentially removes the passivated layer. As such, under ideal conditions the wafer scale uniformity of ALE should be independent of the uniformity of the reactant fluxes onto the wafers, provided all surface reactions are saturated. The passivation and etch steps should individually asymptotically saturate after a characteristic fluence of reactants has been delivered to each site. In this paper, results from a computational investigation are discussed regarding the uniformity of ALE of Si in Cl2 containing inductively coupled plasmas when the reactant fluxes are both non-uniform and non-ideal. In the parameter space investigated for inductively coupled plasmas, the local etch rate for continuous processing was proportional to the ion flux. When operated with saturated conditions (that is, both ALE steps are allowed to self-terminate), the ALE process is less sensitive to non-uniformities in the incoming ion flux than continuous etching. Operating ALE in a sub-saturation regime resulted in less uniform etching. It was also found that ALE processing with saturated steps requires a larger total ion fluence than continuous etching to achieve the same etch depth. This condition may result in increased resist erosion and/or damage to stopping layers using ALE. While these results demonstrate that ALE provides increased etch depth uniformity, they do not show an improved critical dimension uniformity in all cases. These possible limitations to ALE processing, as well as increased processing time, will be part of the process optimization that includes the benefits of atomic resolution and improved uniformity.

Engineering magnetic nanostructures with inverse hysteresis loops

Top-down lithography techniques allow the fabrication of nanostructured elements with novel spin configurations, which provide a new route to engineer and manipulate the magnetic response of sensors and electronic devices and understand the role of fundamental interactions in materials science. In this study, shallow nanostructure-patterned thin films were designed to present inverse magnetization curves, i.e., an anomalous magnetic mechanism characterized by a negative coercivity and negative remanence. This procedure involved a method for manipulating the spin configuration that yielded a negative coercivity after the patterning of a single material layer. Patterned NiFe thin films with trench depths between 15%–25% of the total film thickness exhibited inverse hysteresis loops for a wide angular range of the applied field and the trench axis. A model based on two exchange-coupled subsystems accounts for the experimental results and thus predicts the conditions for the appearance of this magnetic behavior. The findings of the study not only advance our understanding of patterning effects and confined magnetic systems but also enable the local design and control of the magnetic response of thin materials with potential use in sensor engineering.

A 3D Numerical Model for the Optimization of Running Tracks Performance

In previous works, a finite element model of the shock absorbing characteristics of athletics tracks was developed, able to give sufficiently reliable predictions from laboratory tests performed on suitable material samples. The model proved to be effective in discriminating the effects of geometry (i.e. thickness) and material properties (essentially the elastic characteristics) on force reduction, thus allowing a first optimization of the tracks in view of their approval by the International Association of Athletics Federations (IAAF).This simplified 2D model neglected the real track structure, considering it as a single layer of material having homogenized properties. In the present study, a new 3D model was developed to accurately describe the structure of multi-layered tracks, with properties and geometrical construction (e.g. solid or honeycomb) differing from one layer to another.Several tracks having different combinations of top/bottom layers varying in both material formulation (i.e. chemical composition) and geometry were thus considered. Mechanical properties of the individual elements constituting the track were measured with small-scale laboratory tests, taking into account their strain-rate dependence.The 3D model allowed a complete representation of the loads acting on the track and it gave results which are in very good agreement with the experiments. This proves it to be a valuable tool for the purpose of optimizing the track in terms of material formulation as well as layer geometrical construction and arrangement: as an example, the effect of changing the cell size of the honeycomb pattern was investigated.

In situ X-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices.

In epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in situ synchrotron X-ray diffraction during the growth of BaTiO3/SrTiO3 superlattices on SrTiO3 substrates by off-axis radio frequency magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO3 substrates and 20 nm SrRuO3 thin films on SrTiO3 substrates. These experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.

Mechanisms of heat and mass transfer during drying of mate (Ilex paraguariensis) twigs

ABSTRACTExperimental results of surface temperature and moisture content of twigs of mate were obtained in a conveyor-belt dryer operated batchwise. The first response was determined with an infrared sensor, while the second was by conventional gravimetry. A set of 0.04-m-long cylindrical twigs classified manually into three different subgroups on the basis of their diameters (3.5 × 10−3, 6.5 × 10−3, and 10 × 10−3 m) were used in the experiments. Drying always took place in a chamber fed with a thin single layer of material 0.5 m in length and 0.05 m wide. The fresh twigs without leaves at ambient temperature (≈27.2 ± 2.6°C) and with an initial moisture content close to 0.8 ± 0.1 were dried at three different average air temperatures (65.5, 80.2, and 83.8°C) for 7200 s. A full set of nine (31 × 31) drying experiments were performed by varying the examined factors (particle diameter and drying temperature) at three levels. The low estimated Biot numbers (<0.55) indicate that convection plays a much more important role than conduction in heat transfer. Because of this and since heating was much faster than drying, the Newton’s law of cooling alone was successfully applied to describe the increase of particle temperature with time. From a similar analysis involving a convective mass transfer coefficient calculated with the Chilton-Colburn analogy emerged high-mass-transfer Biot numbers (≈5.37 × 103 − 3.65 × 105) that reveal drying of twigs is governed by diffusion. In fact, the equation that represents the Fick’s second law of diffusion in a long cylinder (one-dimensional transfer), solved analytically and coupled to the model of heat transfer, was able to describe the kinetics of drying of mate twigs.

Thermal Impact Resistance of Integrated Thermal Protection System of Space Vehicles

Space vehicles which enter earth’s atmosphere require a thermal protection system (TPS) to protect them against aerodynamic pressure and heating impact. The use of material with high temperature capability in combination with low thermal conductivity, to limit transfer of heat into interior of the structure, is required of the TPS. Because these requirements cannot be accomplished by a single material layer, two material layers are proposed, and their functions are integrated through the TPS design. Future reentry vehicle’s capabilities will in great extent depend upon the capabilities of the materials used for these layers [1]. This paper is devoted to the protection layer of the TPS, to predict its strength and life under the aerodynamic pressure and heat impact loads.

Impact response of granular layers

Motivated by the wave tailoring potential of granular media, this study aims at evaluating force transmission through granular layers made of spherical particles. 2D simulations based on Hertzian contact law between adjacent particles are performed on two distinct systems: (1) layers consisting of ordered bimaterial lattices, and (2) single material layers with random packing. For the ordered systems, force transmission properties are found to vary with material mismatch and layer thickness. Transmitted force-decay in random configurations is substantially higher than those in the ordered systems.

One-dimensional time-domain finite-element modelling of nonlinear wave propagation for non-destructive evaluation

This one-dimensional time-domain finite-element model achieves accurate quantitative modelling of ultrasonic wave propagation in multi-layered structures. First, a sinusoidal wave toneburst is sent into a single layer of material exhibiting inherent material nonlinearity characterised by the nonlinear parameter β and thick enough for the toneburst received in through transmission to be resolved. The signal processing protocol that yields the theoretically correct quantitative value of β involves measuring the received toneburst for several propagation distances as well as the use of scaling factors taking into account the fast Fourier transform implementation, input signal windowing and material damping. Using that model configuration, model parameters (element size, time step, frequency step, input pressure, etc.) are then optimised and chosen quantitatively to generate accurate results. Finally, these model parameters are used for cases of interest where the configuration is not such that the exact β value can be obtained – e.g. thinner sample, pulse-echo etc. but where confidence in the results remains. This quantitative model that can be used for multi-layered structures provides a tangible resource useful to NDE engineers: a new prediction tool expected to enable them to choose the experimental set-up, driving frequency and post-processing method that would optimise kissing bond detection capability.