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1.
Small ; : e2404907, 2024 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-39051519

RESUMO

Colorless, transparent, and mechanically robust aramid polymers are synthesized from two diamine monomers with strong electron-withdrawing groups, using low-temperature solution condensation with diacid chloride. The aramids dissolved very well in the liquid acrylamide monomers. When N,N-dimethylacrylamide (DMA) is used as a reactive diluent, films with the desired features are produced from the hybrid aramid-DMA resins via ultraviolet (UV) curing. The hybrid films are colorless and transparent in the visible region and showed an increase in the glass transition temperature, tensile strength, and elastic modulus in proportion to the aramid content. Laminated glass is manufactured using the hybrid resin as an interlayer, which exhibits very strong adhesion between the two sheets of glass, is not easily broken by an external impact, and do not scatter fragments. Moreover, the laminated glass do not distort images and functioned very effectively in UV blocking, soundproofing, and suppressing changes in the ambient temperature. Heat treatment further improves the light transmittance and impact resistance of the laminated glass. Laminated glass specimens with various fluorescence colors are also manufactured. Aramid-reinforced films prepared using N,N-diethylacrylamide as a reactive diluent underwent thermally induced phase separation in a wet state, providing smart glass with a privacy protection function.

2.
Small ; 20(8): e2304734, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-37828641

RESUMO

Lithium metal-based rechargeable batteries are attracting increasing attention due to their high theoretical specific capacity and energy density. However, the dendrite growth leads to short circuits or even explosions and rapid depletion of active materials and electrolytes. Here, a functionalized and laminated scaffold (PVDF/TiO@C fiber) based on lithiophilic titanium monoxide is rationally designed to inhibit dendrite growth. Specifically, the bottom TiO@C fiber sublayer provides rich Li nucleation sites and facilitates the formation of stable solid electrolyte interphase. Together with the top lithiophobic PVDF sublayer, the prepared freestanding scaffold can effectively suppress the growth of Li dendrite and ensure stable Li plating/stripping. Based on the dendrite-free deposition, the Li/PVDF/TiO@ C fiber anode enables over 1000 h at a current density of 1 mA cm-2 in a symmetrical cell and delivers superior electrochemical performance in both Li || LFP and Li-S batteries. The functional laminated fiber scaffold design provides essential insights for obtaining high-performance lithium metal anodes.

3.
Small ; 20(25): e2308727, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38229134

RESUMO

T-Nb2O5 characterized by the pronounced intercalation pseudocapacitance effect, is regarded as a promising and alternative anode for fast-charging Li-ion batteries. However, its electrochemical kinetics are still hindered by the absence of sufficient and homogenous conductive wiring inside active microparticles. Herein, an in situ pillaring strategy of electronic nano-wires is proposed to slice T-Nb2O5 laminated particles for the development of durable and fast-charging anodes for Li-ion batteries. A micro-level layered structure consisting of nano-carbon-inserted T-Nb2O5 composite flakes is designed and enabled by successive ion exchange, slice exfoliation, in situ polymerization, and carbonization processes. The pillared carbon interlayer (derived from polyaniline) can serve as in-built conductive wires to promote and homogenize electron transfer inside the micro-level particles. The porous structure (formed by the self-assembly of exfoliated flakes) contributes to the improved electrolyte immersion and enhanced lithium migration. Benefitting from the kinetically favorable effects, the modified T-Nb2O5 anode achieves the high-rate capability (108.4 mAh g-1 at 10 A g-1) and ultralong cycling durability (138 mAh g-1 at 1.0 A g-1 after 8000 cycles, with an average capacity decaying rate as small as 0.043‰). This work provides an effective strategy of electron wire pillaring with the slicing effect for laminated electrode materials with high tap density.

4.
Nanotechnology ; 35(39)2024 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-38955131

RESUMO

To overcome the severe problems arising from the insufficient light absorption of ultrathin self-assembly active layers and the high cost use of atomic force deposition (ALD)-grown low-leakage-current transport layers, we successfully developed a low-cost, simple and facile strategy of floating-film transfer and multilayer lamination (FFTML) for constructing highly-efficient ALD-free broadband polarization-sensitive organic photodetectors (OPDs) with the two commonly used structures of donor/acceptor planar heterojunction (PHJ) and donor:acceptor multilayer bulk heterojunction (BHJ). It was found that the PHJ-based polarization-sensitive OPD by FFTML possesses a low dark current due to the high carrier injection barrier, indicating it is more suitable to be applied in low polarized light detection scenarios. In contrast, the BHJ-based device by FFTML has a higher spectral responsivity in the whole wavelength due to more photo-excitons transferred to the donor:acceptor interface and dissociated into photoexcited carrirers. Furthermore, the film thickness, which is tuned by increasing lamination number of BHJ layers, has a big effect on the polarization-sensitive photodetection performance. The polarization-sensitive 4-BHJ OPD by FFTML finally achieved a high specific detectivity of 8.33 × 1010Jones, which was much higher than 2.72 × 1010Jones for the 2-BHJ device at 0 V. This work demonstrates that layer-by-layer lamination of self-assembly films can effectively improve the polarized-light detection performance, contributing significantly to the rapid development of the field.

5.
Sensors (Basel) ; 24(16)2024 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-39205062

RESUMO

This study investigates the manufacturing, testing, and analysis of ultra-thick laminated polymer matrix composite (PMC) beams with the aim of developing high-performance PMC leaf springs for automotive applications. An innovative aspect of this study is the integration of Fiber Bragg Grating (FBG) sensors and thermocouples (TCs) to monitor residual strain and exothermic reactions in composite structures during curing and post-curing manufacturing cycles. Additionally, the Calibration Coefficients (CCs) are calculated using Strain Gauge measurement results under static three-point bending tests. A major part of the study focuses on developing a properly correlated Finite Element (FE) model with large deflection (LD) effects using geometrical nonlinear analysis (GNA) to understand the deformation behavior of ultra thick composite beam (ComBeam) samples, advancing the understanding of large deformation behavior and filling critical research gaps in composite materials. This model will help assess the internal strain distribution, which is verified by correlating data from FBG sensors, Strain Gauges (SGs), and FE analysis. In addition, this research focuses on the application of FBG sensors in structural health monitoring (SHM) in fatigue tests under three-point bending with the support of load-deflection sensors: a new approach for composites at this scale. This study revealed that the fatigue performance of ComBeam samples drastically decreased with increasing displacement ranges, even at the same maximum level, underscoring the potential of FBG sensors to enhance SHM capabilities linked to smart maintenance.

6.
Infect Immun ; 91(6): e0003123, 2023 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-37162364

RESUMO

Cystic echinococcosis is caused by the larval stages (hydatids) of cestode parasites belonging to the species cluster Echinococcus granulosus sensu lato, with E. granulosus sensu stricto being the main infecting species. Hydatids are bladderlike structures that attain large sizes within various internal organs of livestock ungulates and humans. Hydatids are protected by the massive acellular laminated layer (LL), composed mainly of mucins. Parasite growth requires LL turnover, and abundant LL-derived particles are found at infection sites in infected humans, raising the question of how LL materials are dealt with by the hosts. In this article, we show that E. granulosus sensu stricto LL mucins injected into mice are taken up by Kupffer cells, the liver macrophages exposed to the vascular space. This uptake is largely dependent on the intact mucin glycans and on Clec4F, a C-type lectin receptor which, in rodents, is selectively expressed in Kupffer cells. This uptake mechanism operates on mucins injected both in soluble form intravenously (i.v.) and in particulate form intraperitoneally (i.p.). In mice harboring intraperitoneal infections by the same species, LL mucins were found essentially only at the infection site and in the liver, where they were taken up by Kupffer cells via Clec4F. Therefore, shed LL materials circulate in the host, and Kupffer cells can act as a sink for these materials, even when the parasite grows in sites other than the liver.


Assuntos
Equinococose , Echinococcus granulosus , Animais , Humanos , Camundongos , Equinococose/parasitologia , Echinococcus granulosus/química , Genótipo , Células de Kupffer , Lectinas , Mucinas
7.
Chemistry ; 29(68): e202302355, 2023 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-37681404

RESUMO

Preparation of flexible supercapacitors with excellent mechanical properties and self-healing properties is of great significance but still remains a challenge. A self-healable conductive hydrogel based on poly N-hydroxyethyl acrylamide (PHEAA) is fabricated as electrolyte for supercapacitors. The design of the physically cross-linked dual network, and rich hydrogen bonds endow the hydrogel with robust mechanical properties and strong self-healing ability. The hydrogel exhibited an excellent stretchability (723 %) and a high ionic conductivity (21.8 mS/cm). Specially, by in situ growth of electrode film, a non-laminated supercapacitor is obtained with flexibility and self-healing ability. Due to the non-laminated structure, the supercapacitor can work stably under bending and punching. The supercapacitor possessed an areal capacitance of 253.1 mF/cm2 and the capacitance retention was 80 % after five cutting-healing cycles. The pseudo-capacitance contribution of the supercapacitor after self-healing was discussed. It is noteworthy that the supercapacitor maintains the ability to power a clock after self-healing.

8.
Int J Legal Med ; 137(4): 1235-1244, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36383262

RESUMO

In the frame of an experimental setting, the formation of round-shaped compounded glass fragments on the exit site after gunshots through a windshield was examined. For that purpose, a 9 × 19 mm pistol (HK P30) and two different cartridges containing (a) a full metal jacketed round-nosed projectile and (b) a deformation projectile were used. On the basis of 52 gunshots, the morphology, impact angles and terminal ballistics of occurring compounded glass fragments were examined. The results showed that the compounded glass fragments' morphology allowed for the differentiation of two used projectiles. Fragments were able to cause round-shaped defects in a single cotton layer (T-shirt) with subsequent penetration of up to 2.4 cm into ballistic gelatin (10%, 4 °C). As a function of the projectile type, the compounded glass fragments showed different reproducible impact angles that differed notably from the known conical pattern of expelled glass fragments after bullet penetration. These findings might help to explain the atypical morphology of gunshot wounds with laminated glass as an intermediate target and prevent possible misinterpretations when reconstructing the sequence of events.


Assuntos
Armas de Fogo , Ferimentos por Arma de Fogo , Humanos , Balística Forense , Têxteis , Vidro
9.
Exp Parasitol ; 250: 108535, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37116772

RESUMO

The effect of helminthic infections on allergic diseases and asthma is still inconclusive. Moreover, there is considerable evidence suggesting that nitric oxide (NO), metalloproteinases and pro-inflammatory cytokines play a significant role in the physiopathology of these diseases. In this sense, the aim of our study is to investigate the ex vivo immunomodulatory effect of the laminated layer (LL, outside layer of parasitic cyst) of the helminth Echinococcus granulosus on NO, IL-17A and IL-10 production. In the first step of our study, we evaluated in vivo the NO, MMP-9, IL-17A, IL-10 levels in Algerian patients with allergic asthma and allergic rhinitis and their changes in relation with exacerbation status of the patients. In the principal part of our work, we assessed NO, IL-10 and IL-17A levels in supernatants of patients PBMC cultures before and after stimulation with LL. Our results indicate a significant reduction in NO production by PBMC of patients with allergic rhinitis and allergic asthma whether mild, moderate or severe after stimulation with LL. Interestingly, LL induces a significant decrease in the production of NO and IL17-A levels as well as an increase in the production of IL-10 in the cultures performed with PBMC of patients with severe allergic asthma. Importantly, our data indicate that LL exert a down-modulatory effect on inflammatory mediators (NO, IL-17A) and up immune-regulatory effect on IL-10 production. Collectively, our study supports the hygiene hypothesis suggesting that Echinococcus granulosus infection like other helminths could prevent and/or modulate inflammation responses during inflammatory diseases.


Assuntos
Asma , Echinococcus granulosus , Rinite Alérgica , Animais , Humanos , Echinococcus granulosus/fisiologia , Interleucina-17 , Interleucina-10 , Leucócitos Mononucleares , Citocinas
10.
Sensors (Basel) ; 23(18)2023 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-37765982

RESUMO

Delamination damage is one of the most critical damage modes of composite materials. It takes place through the thickness of the laminated composites and does not show subtle surface effects. In the present study, a delamination detection approach based on equivalent von Mises strains is demonstrated for vibrating laminated (i.e., unidirectional fabric) composite plates. In this context, the governing relations of the inverse finite element method were recast according to the refined zigzag theory. Using the in situ strain measurements obtained from the surface and through the thickness of the composite shell, the inverse analysis was performed, and the strain field of the composite shell was reconstructed. The implementation of the proposed methodology is demonstrated for two numerical case studies associated with the harmonic and random vibrations of composite shells. The findings of this study show that the present damage detection method is capable of real-time monitoring of damage and providing information about the exact location, shape, and extent of the delamination damage in the vibrating composite plate. Finally, the robustness of the proposed method in response to resonance and extreme load variations is shown.

11.
Sensors (Basel) ; 23(23)2023 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-38067732

RESUMO

To study the acoustic characteristics of sound scattered from laminated structures such as elastic plates and shells, it is usually required to solve the Lamb waves' dispersion equations. Many traditional root-finding methods such as bisection, the Newton-Raphson method, and the Muller method are not able to tackle the problem completely. A simple but powerful method named local peaks search (LPS) is proposed to overcome their drawbacks. Firstly, the non-zero part of the dispersion equation is defined as the dispersion function, and its reciprocal is used to transform the zeros (i.e., roots) into local peaks. Secondly, the chosen complex domain is discretized, and the coarse local domains where the local peaks exist are determined by the direct search method globally. Thirdly, the Muller method is applied to obtain the refined locations of local peaks. Lastly, in order to refine the results, a hierarchical scheme is designed and the iteration of the above procedures is implemented; the error is set to be 10-16 as the stop criteria. The accuracy of the LPS method is validated by comparing it with the bisection method for the problem of elastic plates in the vacuum. The acoustic echo structures are analyzed experimentally. By computation of Lamb waves' phase velocity, the critical angles are derived numerically and compared with the results acquired by an experiment using monostatic sound transducers. In this way, it is validated that the elastic scattered wave components are the highlights shown in the time-angle figure. Furthermore, the work can be applied for non-destructive testing, especially underwater structural health monitoring.

12.
Sensors (Basel) ; 23(3)2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36772383

RESUMO

This paper presents a coupled thermoelastic finite element formulation for static and dynamic analysis of composite laminated plates with embedded active shape memory alloy (SMA) wires, which accounts for both the phase transformation and the nonlinearity effects of SMA wires. The equations of motion are obtained by using Hamilton's principle and first-order shear deformation theory (FSDT). Furthermore, based on Brinson's one-dimensional phase transformation constitutive law, a novel coupled thermoelastic finite element model that enables analysis of the SMA hybrid composite (SMAHC) plate is developed. The accuracy and efficiency of the developed computational model for analysis of SMAHC plates are reinforced by comparing theoretical predictions with data available from the literature. The results of the numerical examples also show the ability of the proposed model to predict the thermal-mechanical behavior of SMAHC plates in accordance with SMA's hysteresis behavior. In addition, based on the proposed model, the influence of temperature as well as SMA volume fraction, pre-strain value, boundary condition and layup sequence on the static bending and free vibration behavior of the SMAHC plates is investigated in detail. The results of parametric analysis show that the variations of both static deflection and natural frequency of the SMAHC plate over temperature exhibit a nonmonotonic behavior.

13.
Sensors (Basel) ; 23(21)2023 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-37960673

RESUMO

As was shown in the previous part of the study, windshields are an important part of the passive safety means of modern low-floor trams with an extraordinary effect on pedestrian safety in a pedestrian-tram collisions. Therefore, maximum attention must be paid to the definition of tram windshield characteristics. This article describes a windshield crash test, from which data are obtained to verify the feasibility of the applied computational approaches. A developed analytical model is utilised for a simple description of the energy balance during collision with an illustrative definition of the important parameters of laminated glass as well as their clear physical interpretations. The finite element analysis (FEA) performed in Ansys software using two versions of material definition, namely a simpler (*MAT_ELASTIC with nonlocal failure criterion) and a more complex (*MAT_GLASS with brittle stress-state-dependent failure) material model, which are presented as suitable for obtaining a detailed description of the shattering process of laminated glass, which can also be used effectively in windshield engineering.

14.
Small ; 18(27): e2202495, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35670146

RESUMO

WS2 anode materials show huge potential for fast-charging lithium-ion batteries (LIBs) due to the naturally good 2D diffusion pathways but suffer from large Li+ diffusion barrier energy and poor intrinsic electrical conductivity. Here, a defect-rich atomic-scale laminated structure of WS2 and C (D-WS2 -C) with O doping and enlarged interlayer distance from 0.62 to 1.06 nm of WS2 is first fabricated, which is assembled into micron-sized spheres to prepare WS2 /C composite microspheres. D-WS2 -C with maximized molecular layer contact area between WS2 and carbon and large interlayer spacing greatly enhances the electrical conductivity of WS2 and reduces Li-ion diffusion energy barrier, confirmed by density functional theory calculations. Besides, the unique D-WS2 -C enables the formation of vast superfine W nanoparticles (1-2 nm) during the conversation reaction, resulting in the construction of a space charge zone on W surface. Based on these characteristics of D-WS2 -C, the prepared WS2 /C composite microspheres show superior fast-charging capability with a high capacity of 647.8 mAh g-1 at 20 C in half cells. For full cells, a high-energy density of 100.9 Wh kg-1 is achieved at a charge time of only 8.5 min at 5 C, representing the best fast-charging performances in WS2 -based anode materials to date.

15.
Sensors (Basel) ; 22(12)2022 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-35746239

RESUMO

Vibration-based energy harvesters consisting of a laminated piezoelectric cantilever have recently attracted attention for their potential applications. Current studies have mostly focused on the harvesting capacity of piezoelectric harvesters under various conditions, and have given less attention to the electromechanical characteristics that are, in fact, crucial to a deeper understanding of the intrinsic mechanism of piezoelectric harvesting. In addition, the current related models have mostly been suitable for harvesting systems with very specific parameters and have not been applicable if the parameters were vague or unknown. Drawing on the available background information, in this study, we conduct research on a vibration-based cantilever beam of composite-laminated piezoelectric patches through an experimental study of its characteristics as well as a modeling study of energy harvesting. In the experimental study, we set out to investigate the harvesting capacity of the system, as well as the electromechanical (voltage/current-strain and power-strain relationships) characteristics of the cantilever harvester. In addition, we summarize some pivotal rules with regard to several design variables, which provide configuration design suggestions for maximizing energy conversion of this type of harvesting system. In the modeling study, we propose a coupled electromechanical model with a set of updated parameters by using an optimization program. The preceding experimental data are used to verify the superiority of the model for accurately predicting the amount of harvested energy, while effectively imitating the characteristics of a cantilever harvesters. The model also has merit since it is suitable for diversified harvesters with vague or even unknown parameters, which cannot be dealt with by using traditional modeling methods. Overall, the experimental study provides information on a comprehensive way to enhance the harvesting capacity of piezoelectric cantilever transducers, and the modeling study provides a wide scope of applications for cantilever harvesters even if precise information is lacking.


Assuntos
Sistemas Microeletromecânicos , Transdutores , Fontes de Energia Elétrica , Vibração
16.
Sensors (Basel) ; 22(3)2022 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-35161932

RESUMO

Ti-CFRP-Ti laminated stacks have been widely used in aviation, aerospace, shipbuilding and other industries, owing to its excellent physical and electrochemical properties. However, chip blockages occur easily when drilling into Ti-CFRP-Ti laminated stacks, resulting in a rapid rise of drilling temperature and an increase of axial drilling force, which may lead to the intensification of tool wear and a decline of drilling quality. Cutting force signals can effectively reflect the drilling process and tool condition, however, the traditional plate dynamometer is typically difficult in realizing the follow-up online measurement. Therefore, an intelligent tool holder system for real-time sensing of the cutting force is developed and constructed in this paper, and the variable parameter drilling method of Ti-CFRP-Ti laminated stacks is studied on this basis. Firstly, an intelligent tool holder system with high flexibility and adaptability is designed; Secondly, a cutting force signal processing method based on compressed sensing (CS) theory is proposed to solve the problem of high-frequency signal transmission; Lastly, the drilling experiment of Ti-CFRP-Ti laminated stacks is carried out based on the intelligent tool holder system, and the drilling parameters are optimized using a compromise programming approach and analytic hierarchy process (AHP). The comparison of results show that the optimized drilling parameters can effectively reduce the hole wall surface roughness and improve the drilling efficiency while ensuring a small axial force.

17.
J Environ Manage ; 317: 115400, 2022 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-35653848

RESUMO

A cryogel solid amine adsorbent with a laminated structure has been prepared by crosslinking polyethylenimine (PEI) with ethylene glycol diglycidyl ether (EGDE) at a low temperature via liquid nitrogen treatment and freeze-drying. The effects of cryogenic treatment on the morphology of the cryogels were investigated. The liquid nitrogen treatment and freeze drying were critical to create the layered structure. The fast formation of ice crystals at 77 K served as a template which directed the ordered lamellar structure of the PEI and EGDE cross-linked polymer networks. The PEI cryogel adsorbent showed excellent CO2 adsorption performance both in dry and wet conditions. In dry conditions, the PEI-gel-5-0.25 cryogel showed a 5.60 mmol/g of CO2 adsorption capacity at 75 °C. After being swelled with water, the PEI-gel-15-0.25 cryogel showed an extremely high CO2 adsorption capacity of 11.39 mmol/g at 25 °C. The adsorption behaviors of adsorbents with varied water contents were explained using kinetic simulations and intraparticle diffusion simulations. It was found that the presence of water can significantly enhance the diffusion process. The regeneration performance was examined in both dry and wet conditions. After 20 adsorption-desorption cycles, the adsorption capacity of the regenerated PEI cryogel had barely decreased, indicating reliable regeneration stability.


Assuntos
Criogéis , Polietilenoimina , Adsorção , Carbono , Dióxido de Carbono/química , Criogéis/química , Nitrogênio , Polietilenoimina/química , Água
18.
J Radiol Prot ; 42(2)2022 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-35226882

RESUMO

In the few years leading up to this research, CLEAPSS noticed a small but steadily increasing number of calls from UK schools regarding a red-brown discolouration on the surface of the foil of their radium source. There were no reports of this type of discolouration on foils of other radionuclides. CLEAPSS and the University of Liverpool collaborated to investigate the nature and cause of this discolouration and the likelihood that the foils were becoming unsafe. The evidence indicates that the discolouration is principally caused by some combination of silicon, sulfur and possibly lead from within the foil diffusing into the face layer. There is no indication currently that the face layers are fragmenting on these foils, but the longer-term integrity of the discoloured foils now becomes questionable. Given the age of the foils and the radiotoxicity of radium, the recommendation from this research is that discoloured foils should be taken out of service and disposed.


Assuntos
Rádio (Elemento) , Instituições Acadêmicas , Reino Unido
19.
Nanotechnology ; 32(50)2021 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-34555821

RESUMO

FCC-structured CoCrFeMnNi high entropy alloy (HEA) has attracted abroad interests for years because of its excellent mechanical properties, except for strength. Recent experiments have reported a kind of nano-laminated dual-phase (NLDP) FCC/HCP structure that can strengthen the HEA. However, it is still unknown why the HEA can be strengthened by this kind of NLDP structure. Here, we employ molecular dynamics simulations to study the atomistic strengthening mechanism of the NLDP HEA. Dislocation-assisted multiple plastic deformation mechanisms in both FCC and HCP single phase HEAs are observed, and amorphization is also found in the plasticity of HCP phase, which are consistent with the previous experimental characterizations. The HCP phase possesses higher strength because of its higher stacking fault energy, higher Peierls-Nabarro stress and less active dislocation slip systems. It is also found that the introduction of HCP phase can enhance the mechanical properties, including yield stress, yield strain and plastic flow stress, of the NLDP HEAs, which also show volume fraction dependence. And the phase boundary plays crucial roles in the deformation and strengthening of the NLDP HEAs. The plastic deformation of the NLDP HEAs can be divided into two stages, i.e. stage I (plasticity only appears in FCC lamella) and stage II (plasticity in both FCC and HCP lamellas). With the increase of volume fraction, the lamella thickness of FCC matrix phase decreases, leading to continuous strengthening of yield properties and flow stress of stage I because of suppressed dislocation nucleation and confined dislocation motion in FCC matrix phase by the phase boundary. While there is no monotonous relationship between the flow stresses of stage II and the increasing volume fraction of HCP phase, which can be attributed to the competitive mechanisms between strengthening effect of phase boundary on the dislocation motion in FCC phase and softening effect of phase boundary on the dislocation motion in HCP phase. The results should be helpful for understanding the underlying physical mechanism of strengthening of HEAs with NLDP structure.

20.
Nanotechnology ; 32(23)2021 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-33739940

RESUMO

The adhesive contact problem between a rigid cylindrical punch and a gradient nanostructured (GNS) coating is investigated by considering the size effect. The laminated plate model is applied to characterize the material properties of a GNS coating in plane strain couple stress elasticity. By using the Fourier integral transform and transfer matrix method, the governing integral equation(s) for the two-dimensional adhesive contact problem are obtained. Numerically calculated results are presented to analyse the effect of characteristic material length, the adhesion parameter and nonhomogeneous parameters on the mechanical response of the GNS coating for the adhesive contact problem. We explore the nanoscale contact of a GNS coating with shear modulus varying as a function of depth according to an exponential function or the power-law function. The present results provide a way to improve the contact deformation and damage to nanoelectromechanical systems by adjusting the gradient index of the GNS coating.

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