Effect Of Layer Thickness Research Articles

MICROPOLAR FLUID FLOWS RELATIVE TO A SWARM OF SPHERICAL POROUS SHELLS

This article investigates the creeping axisymmetric flow of an incompressible micropolar fluid past a swarm of porous shells. Employing the Darcy and a transition Brinkman porous layer, the study presents an analytical model that captures the flow behavior by integrating continuity conditions for velocity, normal and tangential stresses, and microrotations at fluid-porous interface regions.Distinct unit cell techniques, including those proposed by Happel, Kuwabara, Kvashnin, and Mehta and Morse, are analyzed to observe the effects of hydraulic resistivity, porous layer thickness, and porosity on the dimensionless drag for a bounded micropolar fluid system. The results, graphically represented in a series of plots, reveal a complex interplay between these parameters, significantly impacting drag forces and providing insight into the hydrodynamics of a swarm of porous particles, akin to that encountered in oral drug delivery systems.The study identifies a general inverse relationship between hydraulic resistivity and drag and highlights the nuanced effects of porous layer thickness and porosity on fluid resistance, with stark contrasts observed among different unit cell models. These findings underscore the importance of the chosen unit cell technique in predicting and optimizing the flow behavior in micropolar fluid systems.

Investigation of The Effect of Asphalt Layer and Sub-Base Layer Thicknesses on Pavement Surface Deformation by The Finite Element Method

The layer thickness of flexible pavements is one of the important parameters affecting permanent deformations. In this study, the effect of sub-base thickness and asphalt concrete thickness on the deformations under axial loads was investigated using the Plaxis 2D finite element software. In the study, 100, 200, 300, 400, 500, and 600 kPa pressure were applied to the asphalt pavement surface. In the first case, the base layer of 30 cm thickness was kept constant, and the asphalt layer was changed from 9 to 14 cm. In the second case, the asphalt thickness at 9 cm and the base layer thickness of 30 cm were kept constant, and the sub-base layer thickness was selected at 30, 40, and 50 cm. As a result of the completed analysis, it was observed that the deformations on the pavement surface decreased with increasing thickness of the layers; furthermore, the use of a sub-base layer in the pavement considerably increases the deformation resistance.

Photocatalytic removal of VOCs on TiO2 nanotube layers. Effect of layer thickness and humidity

The current work is focused on the influence of TiO2 nanotube (TNT) layer thickness, texture properties and chemical nature of volatile organic compounds (VOCs) on the efficiency of their photocatalytic oxidative removal. Attention was also given to the evaluation of the degree of mineralisation and the influence of air humidity. The fabricated TNT layers have a thickness from 2to13 μm, TiO2 mass from 0.27 to 1.15 mg cm−2, tube diameter of 108 ± 17 nm and porosity of 74 ± 5 %. Values of areal SBET determined from Kr adsorption are higher than the inner surface area of the TNT layer calculated from morphology parameters, this suggests the rough nature of the inner surface of nanotubes. Acetaldehyde was more easily degraded in comparison to hexane which was explained by a simpler chemical structure. The degree of acetaldehyde mineralisation was almost 100 %, suggesting the formation of no intermediates, analysis confirmed negligible formation of formaldehyde. In contrast, degree of hexane mineralisation was lower, 80 %. An increase in humidity has a negative effect on the photocatalytic performance; this effect is more significant for non-polar hexane compared to water-miscible acetaldehyde. The conversion of hexane and absorptance of the TNT layer at 365 nm increase similarly with increasing thickness. Hexane conversion increases significantly up to a layer thickness of about 4 μm where more than 80 % of incident light is absorbed. The simultaneous degradation of four pollutants (acetaldehyde, acetone, heptane and toluene) results in the highest degradation rate of acetaldehyde and the lowest for heptane, this was attributed to their different solubility in water as well as to their different adsorption.

Enhancing the MRI contrast and hyperthermic properties of magnetic nanoflowers by modulating magnetisation dynamics using poly(butyl cyanoacrylate) shells; towards multi-functional clinical carriers

Magnetic-polymeric complexes have strong potential as theranostic tools; when prepared as stable suspensions in the nano-range they are functionalisable carriers which can provide MRI (magnetic resonance imaging) tracking, static-field targeting and localised hyperthermia (on AC-field irradiation). In this work the effect of the polymer layer thickness on the MRI and hyperthermic efficacies, in clinically relevant ranges, for poly(butyl cyanoacrylate) encapsulated multi-domain γ-Fe2O3 nanoparticles was investigated for the first time. A series of nanocomposites were prepared at varying particle/polymer ratios revealing that progressively thicker polymer shells maximised the carrier potential and improved the MRI and hyperthermic efficacy due to enhancement of the Néel and partial suppression of the Brownian contribution to the dynamics of the magnetic moments. The implications for the development of multifunctional theranostic agents with optimised efficacy for AC-field triggered release are discussed.

Fluorescent nanocomposites of Ag nanoclusters grown in anionic polymer layers grafted to plastic substrate: Preparation, characterization and evaluation in Hg2+ sensing and white light generation

AbstractFluorescent noble metal nanoclusters (NCs) are emerging optical nanomaterials with properties similar to those of quantum dots. Their applications can be expanded by combining them with polymer matrices to obtain flexible and transparent light‐emitting nanocomposites. However, achieving highly fluorescent nanocomposites of this type remains challenging due to phase separation and aggregation of NCs in polymer hosts leading to a strong reduction in fluorescence efficiency. We address this key issue by covalently grafting a layer of a specifically selected matrix polymer onto a transparent plastic film and photochemically synthesizing the fluorescent metal NCs directly in the grafted layer. The surface‐grafted matrix polymer effectively captures the noble metal (Ag) ions, photo‐reduces them to atoms, acts as a capping ligand for the growing Ag NCs, and immobilizes them on the substrate surface. The Ag NCs were produced by both wet and dry synthesis, and effects of synthesis method, reaction time, and matrix polymer layer thickness on the fluorescence properties of the resulting nanocomposites were investigated and discussed. Importantly, the fluorescence intensity of these nanocomposite films is sensitive to submicromolar concentrations of aqueous Hg2+ that makes them useful as fluorescent sensing materials for selective and ultrasensitive detection of Hg2+ ions in water. Besides, the nanocomposite films obtained by the dry synthesis of NCs exhibit an intensive emission covering the whole green to red range of the visible spectrum and, hence, produce bright white light under illumination with a blue LED that makes them attractive as down‐conversion materials in one‐phosphor‐converted white LEDs.

Estimation of friction and wear properties of additively manufactured recycled-ABS parts using artificial neural network approach: effects of layer thickness, infill rate, and building direction

Abstract This investigation aims to elucidate friction and wear features of additively manufactured recycled-ABS components by utilizing neural network algorithms. In that sense, it is the first initiative in the technical literature and brings fused deposition modeling (FDM) technology, recycled filament-based products, and artificial neural network strategies together to estimate the friction coefficient and volume loss outcomes. In the experimental stage, to provide the required data for five different neural algorithms, dry-sliding wear tests, and hardness measurements were conducted. As FDM printing variables, layer thickness (0.1, 0.2, and 0.3 mm), infill rate (40, 70, and 100 %), and building direction (vertical, and horizontal) were selected. The obtained results pointed out that vertically built samples usually had lower wear resistance than the horizontally built samples. This case can be clarified with the initially measured hardness levels of horizontally built samples and optical microscopic analyses. Besides, the Levenberg Marquard (LM) algorithm was the best option to foresee the wear outputs compared to other approaches. Considering all error levels in this paper, the offered results by neural networks are notably acceptable for the real industrial usage of material, mechanical, and manufacturing engineering areas.

GaN-HEMT Performance Enhancement

In this work, a simulation analysis and calibration are carried out to improve the performance of AlGaN/GaN- MOSHEMTs (Metal-Oxide Semiconductor High Electron Mobility Transistors). The effect of the AlGaN layer thickness, gate length, Al mole fraction, and the interface traps on the electrical performance of the device has been presented. Device simulations have been done using Sentaurus technology computer-aided design (TCAD). The simulations and analysis show better drain current, transconductance, and cut-off frequency performance. The maximum cut-off frequency shown by the proposed HEMT device is 45.7 GHz at 100-nm gate length. Good transcoductance has been obtained by scaling down the gate length of the device, which is ascribed to the present two-dimensional electron gas (2DEG) density that supports upgrading the output current. Higher drain current is achieved without using acceptor-like traps in the Al2O3/AlGaN interface. Results show that the Al2O3/AlGaN/GaN-based MOSHEMT is a promising device for high-frequency and power electronic applications.

Experimental investigation on punch shear strength of poly lactic acid specimens for biomedical applications.

The designed biomedical implants require excellent shear strength primarily for mechanical stability against forces in human body. However, metallic implants undergo stress shielding with release of toxic ions in the body. Thus, Fused Deposition Modeling (FDM) has made significant progress in the biomedical field through the production of customized implants. The mechanical behavior is highly dependent on printing parameters, however, the effect of these parameters on punch shear strength of ASTM D732-02 standard specimens has not been explored. Thus, in the current study, the effect of infill density (IFD), printing speed (PTS), wall thickness (WLT), and layer thickness (LYT) has been investigated on the punch shear strength using Response Surface Methodology. The Analysis of Variance (ANOVA) has been performed for predicting statistical model with 95% confidence interval. During the statistical analysis, the terms with p-value lower than 0.05 were considered significant and the influence of process parameters has been examined using microscopic images. The surface plots have been used for discussing the effect of interactions between printing parameters. The statistical results revealed IFD as the most significant contributing factor, followed by PTS, LYT, and WLT. The study concluded by optimization of printing parameters for obtaining the highest punch shear strength.

Enhanced solid particle erosion resistance of nanocrystalline Ni-W coatings through multilayer approach

Electrodeposited nanocrystalline Ni-W alloy coatings are projected as potential alternatives for hard chrome (HCr) coatings owing to their comparable hardness and superior corrosion resistance. However, the limited strain hardening ability of the nanocrystalline Ni-W coatings manifests in their poor resistance towards solid particle erosion involving a high strain-rate (>103 s−1) deformation. In the present study, a novel microstructural engineering strategy has been implemented to enhance the strain hardening ability of the nanocrystalline Ni-W coatings without compromising on their strength/hardness. Ni-W multilayer coatings composed of alternatively stacked soft (2.6 GPa) and hard (8.5 GPa) Ni-W layers were developed using the pulse reverse electrodeposition technique. Further, to investigate the effect of individual layer thickness (λ), multilayer coatings with different λ were deposited. Solid particle erosion testing using the angular SiO2 particles showed that the multilayer coatings (irrespective of λ) exhibit superior erosion resistance compared to the homogeneous nanocrystalline Ni-15W at both oblique (θ = 30°) and normal (θ = 90°) impact conditions. The post-erosion microstructural analysis of the multilayer coatings revealed that the hard Ni-W layers undergo uniform strain (ε > 50 %) without cracking due to the constrained co-deformation imposed by the surrounding soft Ni-W layers. Therefore, the enhanced erosion resistance of the multilayer coatings is attributed to the effective dissipation of impact energy through co-deformation of the individual hard and soft Ni-W layers.

Study of the Effect of Thin Layer Thickness on the Structural Properties of Copper Phthalocyanine (CuPc) Films Prepared by Vacuum Thermal Evaporation Method

Study of the Effect of Thin Layer Thickness on the Structural Properties of Copper Phthalocyanine (CuPc) Films Prepared by Vacuum Thermal Evaporation Method

In-situ monitoring of additive friction stir deposition of AA6061: Effect of layer thickness on the microstructure and mechanical properties

Depositions of AA6061 aluminum alloy with different thicknesses (0.5, 1.0 and 1.5mm) and homogeneous microstructure were successfully obtained through additive friction stir deposition (AFSD) technique. A self-developed in-situ process monitoring kit has been utilized to in-situ monitor the real-time temperature, force and torque during the AFSD process. Effect of thickness on the microstructure and mechanical properties are investigated based on the monitored parameters. With the electron back scattered diffraction (EBSD) analysis on a large area (4 × 4 mm2), the synergism of dynamic recrystallization (DRX) and shear deformation is found to affect the microstructure. DRX is the main reason for the grains refinement which are remarkably reduced to 7 μm as the thickness increases. Whereas, the shear deformation exhibits a stronger effect on the texture. The texture intensity reduces and then increases as the thickness increases from 0.5 to 1.5mm. Values of micro-hardness (46.8 HV0.5), yield strength (106.0MPa) and ultimate tensile strength (171.2MPa) of the deposition are the highest when the thickness is the largest (1.5mm) attributed to the lowest thermal cycle and evolution of DRX. All the findings provide useful guidance for the visualization and understanding of AFSD process.

Effect of layer thickness, inner structure, and implant angulation on the accuracy of 3D printed models with implant analogs

Effect of layer thickness, inner structure, and implant angulation on the accuracy of 3D printed models with implant analogs

Active and passive monitoring of corrosion state of reinforced concrete based on embedded cement-based acoustic emission sensor

In this paper, a cement-based acoustic emission sensor is embedded in reinforced concrete, and the corrosion damage inside the concrete is activated by swinging ball impact. The changes of low frequency and high frequency acoustic emission signals are captured and analyzed by the sensor, and the concept of low-high-frequency (LH) is proposed. The changes of acoustic emission characteristics during the corrosion of steel bars were studied, and the effects of protective layer thickness and activation site on the ratio of LH were analyzed. The results show that with the increase of the corrosion degree, the amplitude of the frequency signal in the range of 13 kHz ∼ 22 kHz decreases gradually, from 2.59 mV to 1.29 mV. The amplitude of the frequency signal near 170 kHz increases first and then decreases with the increase of corrosion time. The frequency signal near 22 kHz is used as the low frequency signal, the amplitude of the frequency signal near 170 kHz is used as the high frequency signal, and the ratio of the two is used as the low-high-frequency (LH). The evaluation result of this ratio is consistent with the ultrasound test results. As the sound source continues to move to both ends of the concrete sample, the distance between this sound source and the sensor gradually increases, the low frequency signal decreases significantly, and LH changes significantly, influenced by the reflection of the boundary.

A finite deformation formulation for amorphous glassy polymers under moderate and impact strain rates: Application to adhesive films

This work describes a novel finite strain hypo-elastic formulation for amorphous thermoset polymers working in the glassy regime. The constitutive formulation is able to describe time and pressure-dependent behaviour under loading rates ranging from quasi-static to impact-type loading conditions and to account for thermo-mechanical coupling effects. A non-linear pressure dependent potential function is introduced to capture the non-associative visco-plastic potential flow for volumetric plastic strain control. The formulation also incorporates an internal state or deformation resistance variable to enable the description of the polymer hardening - softening behaviour, as well as a novel relation for the dissipative fraction of the plastic work in terms of the equivalent accumulated plastic strain. The constitutive model is formulated within a finite strain kinematics framework, and full details of its numerical implementation into the finite element method using a fully implicit Euler Backward algorithm are given. Model calibration is carried out for three different thermosetting resins (PR520 and RTM6 Epoxies, and MMA adhesives).To illustrate the model capabilities, two case studies are investigated: (i) the de-formation behaviour of epoxy under moderate and impact-type loading conditions under isothermal and fully adiabatic conditions, and (ii) the fracture behaviour of adhesive layers used to bond stiff metallic substrates. Results on RTM6 epoxy show that at, e.g., 60% true strain, 48.5% of the rate of plastic work is dissipative, and that the corresponding predicted increase in temperature due to the locally dissipated heat is consistent with published calorimetry data on a similar thermoset polymer. It was also found that, by coupling the proposed constitutive model with a cohesive zone model, it was possible to predict accurately the effect of an MMA adhesive layer thickness and pressure-dependency on the growth of an interfacial crack between the MMA adhesive and the metallic substrates. The proposed model should constitute a generic phenomenological formulation for the mechanical behaviour prediction of a wide range of thermoset polymers under confined and quasi-adiabatic conditions such as in composites and adhesive joints.

Failure mode analysis and prediction model of additively manufactured continuous carbon fiber‐reinforced polylactic acid

AbstractCarbon fiber‐reinforced composites are widely used in aerospace, rail transportation, and new energy vehicles due to their small specific gravity as well as good mechanical and chemical properties. Additive manufacturing of continuous carbon fiber‐reinforced polymer composites is an innovative composite manufacturing technique. In this paper, bending and shear specimens with different hatch spacing and layer thicknesses were prepared by fused filament fabrication (FFF) technique and subjected to three‐point bending experiments and interlayer shear experiments, respectively. The results showed that the maximum flexural strength and flexural modulus of the fabricated parts were 383.81 MPa and 41.23 GPa, respectively, and the maximum interlayer shear strength was 13.64 MPa. Finally, an optimized criterion for determining fiber kinking, fiber breakage, and matrix damage was proposed by considering in situ strength variations induced by process parameters. This new model was subsequently validated and could provide a method for fracture predicting of additive manufactured carbon fiber‐reinforced composites.Highlights CCFRC parts with different porosities were prepared by adjusting the layer thickness and hatch spacing. The bending and interlaminar shear damage mechanisms of CCFRC fabrications are revealed, and the effects of layer thickness and hatch spacing on their mechanical properties are investigated. Introduction of additive manufacturing factors to optimize failure models for CCFRC parts. Introduction of additive manufacturing coefficients to accurately predict the interlaminar shear strength of CCFRC parts by AM.

Rubidium based new lead free high performance perovskite solar cells with SnS2 as an electron transport layer

Lead-free perovskite-based solar cells has acquired rapid and expanding attention due to removing hazardous lead from perovskite materials. The major goal of this work is to supplement the research progress by doing a comparative analysis of lead-free perovskite-based solar cells using DFT and a numerical simulation method with the solar cell capacitance simulator-SCAPS-1D. At first, the bandgap and all optical performance were calculated via DFT then these data were applied SCAPS-1D simulator. Next design and optimized all solar cell performance parameters and compare of lead-free perovskite of RbSnCl3 and traditional perovskite RbPbBr3 solar cell with SnS2 as a high-bandgap chalcogenide electron transport layer (ETL) through SCAPS-1D. The effect of absorber and electron transport layer (ETL) thickness, doping concentration, defect density, interface defect density and temperature impact on solar cell efficiency has been comprehensively explored and compared. The proposed heterostructure of Al/FTO/SnS2/(RbPbBr3 and RbSnCl3)/Au shows that the PCE over 29.75% and 33.61% obtained with VOC of 0.978 and 0.825 V, Jsc of 34.58 and 51.44 mAcm−2, and FF of 87.91 and 79.19% for RbPbBr3 and RbSnCl3 absorber, respectively. These detailed findings revealed that high-performance lead-free perovskite solar cells can be achieved in a near future.

Thin silicon heterojunction solar cells in perovskite shadow: Bottom cell prospective

Perovskite/Silicon (Pero-Si) tandem with silicon heterojunction (SHJ) bottom cells is a promising highly efficient concept, which in the case of mass production will likely rely on the same wafer feedstock as the single junction Si solar cells. The thickness of these wafers is constantly decreasing for economic and sustainability reasons. We forecast that Si bottom cells for mass produced Pero-Si tandems will be based on wafers thinner than 100 μm. In our work we study challenges and opportunities related to this likely wafer thinning for the performance of the SHJ bottom cells operating in Perovskite shadow. We study SHJ cells prepared on 80 μm thick wafers in comparison to the reference cells based on 135 μm thick wafers addressing two issues: passivation and light management. Effects of passivating layer thickness, back reflector and antireflection coating are studied under AM1.5G standard test conditions, attenuated AM1.5G irradiance, and under Perovskite-filtered spectrum. We show that major wafer thickness reduction of 40% turns to only approx. 0.35%abs loss in the bottom cell efficiency. This minor loss can be reduced even further using highly technological ITO/MgF2/Ag back reflector and MgF2 anti-reflection coating. Our work shows that significant potential for Pero-Si tandems is waiting to be explored in the perovskite shadow from the SHJ bottom cell perspective.

Design of metallization layers for PZT piezoelectric ceramics and joining to 4J29 Kovar alloy

To enhance the bonding strength of PZT ceramics/4J29 Kovar alloy joints, the metallization layers on PZT ceramics were strategically designed, fabricated, and optimized. Subsequently, the metallized PZT ceramics were successfully joined with the 4J29 Kovar alloy using Sn-3.0Ag-0.5Cu (SAC305) solder. In this study, the wetting behavior, joining mechanism and the effect of metallization layers thickness on the joining strength were investigated. The (Ti + Ni + Au) multilayer structure enhances wetting, as Au dissolves into the solder to improve wetting, while Ni serves as a barrier to prevent direct contact between the solder and Ti, thereby ensuring the integrity of the metallization layer. The joining mechanism for PZT ceramics/solder and solder/4J29 Kovar alloy involves the reaction between Ni (in the metallization layer) and Sn (in the solder), and Sn diffusion into 4J29 Kovar alloy, respectively. The highest joint strength of 29.0±1.4 MPa was achieved with (Ti + Ni + Au) metallization layers (Ti:100 nm, Ni:1000 nm, Au:300 nm), marking a 120% improvement over the adhesive currently used for joining PZT ceramics to 4J29 Kovar alloy. Our work presents a promising method for joining PZT ceramics with 4J29 Kovar alloy, which is applied in transducers as a core component for oil logging.

Numerical investigation of internal damage in heterogeneous-structured laminates using a 3D multiple physical mechanisms based constitutive model

Heterogeneous-structured laminates (HSLs), which consist of multiple layers of metallic materials arranged in successive pairs of coarse-grained (CG) and nano-grained (NG) layers, have been recently reported to display excellent balance of strength and ductility. However, it is argued that accompanying state-of-art numerical models developed to simulate the deformation of this specific class of composite materials have limitations for investigating their underlying damage evolution. Addressing this issue is essential to support the rational design, optimisation and application of HSLs, especially when subjected to contact and dynamic processes. For this reason, a novel 3D numerical framework for HSLs is proposed and tested in this research considering published experimental findings and dislocation theories. This framework comprehensively considers the evolution of various types of dislocations and back stress while being coupled with the Johnson Cook damage criterion. The HSL specimens simulated here were made of alternating layers of CG and NG copper separated by interface affected zones. Following initial microhardness and uniaxial tensile simulations on homogenous copper with different grain sizes, simulations of HSLs were conducted to study the effect of different layer thickness and the volume fraction of the NG layer. Overall, a good correlation between numerical and experimental results was achieved. An important and distinguishing characteristic of this research is that the proposed model enables the evolution of internal damage and the synergetic effect between the CG and NG layers to be investigated. Through the evaluation of the damage accumulation factor in the NG layer, the simulations results yielded quantitative information which aligned with the following known experimental observations: 1) the smaller the layer thickness, then the smaller the internal damage and 2) the internal damage increases with the increase in volume content of the NG layer. In addition, for a set simulated strain of 10%, the developed model could be used to show that the damage accumulation factor in the NG layer was 10 times lower than that in its counterpart, i.e., a stand-alone NG layer not sandwiched between two CG layers.

Simulation study on the effect of operating and materials parameters on electrocaloric device for battery cooling

The present simulation work discusses the effect of different electric pulses, operating temperatures, electrodes and substrate materials on electrocaloric(EC) performance. The electrocaloric effect (ECE) is analyzed using poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) P(VDF-TrFE-CFE) polymer with electrode. The P(VDF-TrFE-CFE) film (100 μm) shows an effective adiabatic temperature change (ΔT ad)effective (considering losses) of 4.01 K at 100 MV m−1 when a square electric field (E) pulse is used. An effect of electrode and substrate layer thickness is also analyzed; the electrocaloric performance decreases with an increase in the thickness of the substrate layer. A smartphone battery’s surface (7 cm × 3 cm) is considered for cooling by the proposed design. The simulation study shows battery’s surface/source temperature dropped from 313.15 K to ∼298 K, ∼297.5 K, and ∼293.5 K when air cooling, the EC device in contact with the battery (no ECE, E = 0) and EC device in contact with battery (with ECE, E = 100 MV m−1), respectively are used in ∼6.5 s. The proposed EC device design can provide new insight for mobile or other electronic cooling applications.