Multilayer Composite Films Research Articles

Internal-strain release and remarkably enhanced energy storage performance in PLZT–SrTiO3 multilayered films

The multilayered composite films combining antiferroelectric (AFE) Pb0.97La0.02(Zr0.95Ti0.05)O3 (PLZT) with paraelectric (PE) SrTiO3 (STO) have been fabricated by the sol–gel method, and their ferroelectric and energy storage performances were carefully investigated. It was revealed that both the dielectric breakdown strength (Eb) and the maximum polarization (Pm) in the multilayered composite films are increased. Consequently, an ultra-high and recoverable energy storage density (Wre) of ∼101 J/cm3 and a high efficiency (η) of ∼62% were achieved in the composite film with an 18 wt. % STO content. The enhanced Wre in the multilayered composite is attributed to the internal-strain release of the PLZT layers and charge blocking by the STO layers with significantly enhanced Eb. The results suggest an effective way of improving the energy storage performances by combining AFE PLZT and PE STO.

Microstructure, mechanical and tribological properties of multilayer Ti-DLC thick films on Al alloys by filtered cathodic vacuum arc technology

Low hardness and poor wear resistance are major limitations of Al alloys, which hinder their application in several fields, especially automotive moving parts. DLC can effectively improve hardness and wear resistance of Al alloys, but high residual stress and poor adhesion limit the film thickness. Multilayer thick films (~10 μm) composed of alternating Ti and Ti-DLC layers were successfully deposited on Al alloys. The influence of Ti content on the microstructure, mechanical and tribological properties of the film was emphasized. As the Ti content decreased from 10.42 to 1.35 at.%, the microstructure evolved from a polycrystalline composite film to a nanocrystalline composite film, and then to an amorphous film. The mechanical and tribological properties of the film depended on the microstructure. The amorphous composite film (Ti >6.06 at.%) exhibited better wear resistance than the polycrystalline composite film (Ti <6.06 at.%) due to the higher H/E⁎ (>0.1), H3/E⁎2 (>0.2) and elastic recovery (>60%). When the doped Ti content was 6.06 at.%, the nanocrystalline composite multilayer film showed superior comprehensive performance of high hardness (~23 GPa), high elastic recovery (~69%), low friction coefficient (~0.13) and low wear rate (1.0 × 10−7 mm3/Nm).

High-barrier polymeric multilayer film with organic and interactive materials

Barrier or encapsulate films are indispensable components of organic electronic devices. The stability of organic electronic devices strongly depends on the efficiency of these barrier films, for they prevent device degradation and moisture penetration in the device. In this study, a hybrid composite multilayer film, comprising an interactive composite layer sandwiched between two composite organic layers, was devised. The middle interactive composite layer (COMM) comprised inorganic montmorillonite dispersed throughout an epoxy and phenoxy polymer (POL) matrix. The external organic composite layers (POL-EZ) consisted of POL and the newly synthesized eugenol benzoxazine (EZ) composite. The new multilayer film exhibited excellent transparency, tensile strength, chemical resistance, and stability. The POL-EZ/COMM/POL-EZ/PET film (where PET denotes polyethylene terephthalate and was used as the substrate) exhibited a remarkable moisture permeation rate of 7.140 × 10−3 gm-2 day-1. Moreover, the multilayer film could be easily processed via roll-to-roll coating processes. Thus, the newly fabricated barrier film is an exceptional candidate for commercialization as barrier films for organic electronic devices.

Preparation of Functionalized Graphene Multilayer Composite Films Supported Pt Catalyst and its Electro-Oxidation for Methanol

The multilayer composite films consisting of poly (diallyldimethylammonium chloride) functionalized graphene (PDDA-rGO) and phosphomolybdic acid functionalized graphene (PMo12-rGO) were prepared by layer-by-layer self-assembly method. The {PDDA-rGO/PMo12-rGO}n multilayer composite films were used as a support for electro-deposition of Pt particles in situ. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy and scanning electron microscopy were employed for examining the composition, structure, and morphology of the catalyst. Results revealed that the Pt/{PDDA-rGO/PMo12-rGO}n catalyst is successfully prepared and that the multilayer composite films support improves the dispersion of the Pt particles. CV and chronoamperometry were employed to evaluate the electrocatalytic performance for methanol oxidation. Results revealed that the electrocatalytic activity and stability of the Pt/{PDDA-rGO/PMo12-rGO}3 catalyst for methanol oxidation are considerably improved in comparison with that of the Pt/GCE catalyst. The current density for the oxidation of methanol increased from 0.66 mA/cm2 to 1.21 mA/cm2. In addition, the ratio of the forward current density to the backward current density (If/Ib) was 1.92 for Pt/{PDDA-rGO/PMo12-rGO}3 catalyst, corresponding to 1.3 times that of the Pt/GCE catalyst. This result indicated that the multilayer composite films remarkably enhanced the electrocatalytic activity regarding methanol oxidation.

A molecularly imprinted polymer combined with dual functional Au@Fe3O4 nanocomposites for sensitive detection of kanamycin

Based on molecular imprinting and nanotechnology, a highly specific and sensitive electrochemical aptasensor was proposed for assaying kanamycin (KAN). First, chitosan-graphene (CG) composite multilayer films and Au nanoparticles (AuNPs) were applied to modify a glassy carbon electrode (GCE) for augmented “electron antennae». Then, we constructed a KAN sensor using functional monomer of 3-aminophenylboronic acid (3-APBA) as trap. Au@Fe3O4 nanocomposites, Fe3O4 nanoparticles (Fe3O4NPs) loaded with AuNPs, were dual functionally modified with β-cyclodextrin-ferrocene (Fc/β-CD-SH) and KAN aptamers (APT/Fc/β-CD-SH/Au@Fe3O4) were applied as the tracing tag. The KAN aptamer acted as the bind unit to specifically identify the KAN captured by the imprinted cavities on the MIP modified electrode surface, while the Fc/β-CD-SH was used as a signal unit for KAN quantification. The presented assay exhibited a good linear relationship between KAN concentration (10–500 nM) and the strength of the electrochemical signal, with a detection limit of 1.87 nM and a correlation coefficient of 0.98. The selectivity, stability and reproducibility of the proposed sensor were acceptable. Furthermore, it was used successfully to detect KAN in different aqueous solution, such as in spiked milk, the proposed sensor could be applied for specifically, sensitively and rapid determination for antibiotic contamination in food, water and biological samples.

Multilayer packaging: Advances in preparation techniques and emerging food applications.

In recent years, with advantages of versatility, functionality, and convenience, multilayer food packaging has gained significant interest. As a single entity, multilayer packaging combines the benefits of each monolayer in terms of enhanced barrier properties, mechanical integrity, and functional properties. Of late, apart from conventional approaches such as coextrusion and lamination, concepts of nanotechnology have been used in the preparation of composite multilayer films with improved physical, chemical, and functional characteristics. Further, emerging techniques such as ultraviolet and cold plasma treatments have been used in manufacturing films with enhanced performance through surface modifications. This work provides an up-to-date review on advancements in the preparation of multilayer films for food packaging applications. This includes critical considerations in design, risk of interaction between the package and the food, mathematical modeling and simulation, potential for scale-up, and costs involved. The impact of in-package processing is also explained considering cases of nonthermal processing and advanced thermal processing. Importantly, challenges associated with degradability and recycling multilayer packages and associated implications on sustainability have been discussed.

Enhancing performance of perovskite solar cells with efficiency exceeding 21% via a graded-index mesoporous aluminum oxide antireflection coating

Antireflection (AR) film is a widely used technology to enhance the performance of photovoltaic devices that require transparent electrodes in the photovoltaic industry. At present, several AR films including monolayer MgF2 or multilayered composite films, textured polydimethylsiloxane (PDMS) and porous SiO2 have been successfully applied due to their excellent properties. Nevertheless, all of the above-mentioned AR films have some minor drawbacks to overcome, for instance, the cost or thermal durability. Herein, we report a cost-effective and low-temperature method to fabricate a mesoporous aluminum oxide (meso-Al2O3) layer as the AR coating with high thermal durability, which will meet the fabrication condition of various photovoltaic devices. Briefly, the process begins at magnetron sputtering a compact Al2O3 film, which shows no AR effect, followed by a hot water treatment at 80 °C to turn the compact film into a mesoporous film with graded-index and AR effect. The application of meso-Al2O3 AR film enhances the maximum transmittance of our laboratory-used fluorine-doped tin oxide (FTO) from 84% to 89%, which is in good agreement with our theoretical simulation named graded-index approximation. Taking perovskite solar cells (PSCs) as an example, planar PSCs with meso-Al2O3 AR film deliver excellent photon conversion efficiency of 21.5%, which is higher than that of cells without meso-Al2O3 AR film (20.9%).

Multilayer polyethylene/ hexagonal boron nitride composites showing high neutron shielding efficiency and thermal conductivity

Abstract Polymer composites show huge potential as high efficiency neutron shielding and thermally conductive materials applying in aerospace, nuclear reactors, medical treatment fields, where neutron radiation is inevitable. Designing multilayer structure with concentrated filler in one layer is an effective strategy for achieving high neutron shielding efficiency at low filler loading. Herein, multilayer composite films with alternating high density polyethylene/hexagonal boron nitride (HDPE/hBN) layers and low density polyethylene (LDPE) layers were prepared by stacking hot-pressing. By selecting suitable hot-pressing temperature and pressure, multilayer composite films with highly oriented hBN sheets were successfully fabricated, and confirmed by the morphology and structure characterizations. As a result, the multilayered PE/hBN films show excellent neutron shielding performance through multiple repeated scattering, absorption, and dissipation between multilayers. At the filler content of 30 wt%, the ratio of transmitted neutrons to incident ones decreases to 4.16%, which is much lower than that with random PE/hBN composite (14.95%). Meanwhile, the concentrated and oriented hBN results in multilayer PE/hBN composite with a higher in-plane thermal conductivity than random one. Such the high thermal conductivity can contribute to the rapid dissipation of heat converted by neutron energy. Therefore, the superhigh neutron shielding efficiency and excellent thermally conductivity, as well as the simple and scale preparation process, mean our multilayer PE/hBN films with a huge application prospect.

Influence of microstructure on tribological properties and corrosion resistance of MoS2/WS2 films

Transition metal dichalcogenides (TMDs) are easily oxidized in the marine atmosphere environment, which results in a sharp deterioration of lubricity and limits its application. Combining two TMDs with different properties to form composite film or multilayer film is an important way to improve the performance. In this work, the MoS2/WS2 composite film and multilayer film with different microstructure characteristics were prepared by magnetron sputtering. For the MoS2/WS2 multilayer film, the regular and favorable (002) stacking plane parallel to the substrate was obtained and the compact structure was achieved by interrupting the continuity of the same component film. The multilayer interface not only significantly improved the hardness by hindering dislocation movement, but also improved the corrosion resistance by hindering the diffusion of H2O, O2, Cl− and Na+ corrosives. Consequently, the mechanical properties, the tribological properties and corrosion resistance of the MoS2/WS2 multilayer film were significantly better than that of the MoS2/WS2 composite film. The study can provide guidance for the design of high-performance and corrosion-resistant TMD films.

Magnetoelectric Coupling in Epitaxial Multiferroic BiFeO3–BaTiO3 Composite Thin Films

Herein, the magnetoelectric (ME) performance of epitaxial multilayer composite films built from nanometer‐thick layers of multiferroic BiFeO3 and ferroelectric BaTiO3 is reviewed. A successful implementation of shadow‐mask pulsed laser deposition considerably reduces the interface and surface roughness of the multilayers. In dependence of double‐layer thickness and the degree of structural perfection, the multilayers show high ME voltage coefficients up to 480 V cm−1 Oe−1 at 300 K and 0 T bias magnetic field. With decreasing double‐layer thickness, an interface‐driven effect critically enhances the ME coupling in this strain and charge–comediated system. Interestingly, the characteristics of temperature and DC magnetic field dependencies of magnetoelectric voltage coefficients change with the transition from the 2D to 3D character of the single layers, i.e., for BiFeO3 layers thicker than 5 nm within the multilayers. These changes are attributed to variations of the contributing ME coupling mechanisms. Furthermore, scanning transmission electron microscopy (STEM) with energy‐dispersive X‐ray (EDX) spectroscopy mapping‐based nanoanalysis indicates that chemical effects at the interfaces play an important role for the ME performance of the BiFeO3–BaTiO3 multilayer thin films.

Layer-by-layer immobilizing of polydopamine-assisted ε-polylysine and gum Arabic on titanium: Tailoring of antibacterial and osteogenic properties.

Bacterial infection has become a crucial reason that give rise to failure of medical implants in clinical applications. In this regard, various antibacterial surface modifications of implants have been developed in recent years. However, it remains a challenge to enable the implant surfaces with both suitable antibacterial and osteogenic properties. In this work, ε-polylysine and gum Arabic multilayer composite films were immobilized layer by layer (LBL) on anodized titanium with the assistance of polydopamine for the first time. In vitro antibacterial results showed that the bacteria numbers decreased with an increase in the loading amount of ε-polylysine. Furthermore, long-term antibacterial property up to 3weeks against both gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) was obtained combined with the merits of covalent binding and LBL methods. Meanwhile, the cell proliferation and osteogenic differentiation of BMSCs on titanium dioxide nanotubes (TNTs) modified with composite films was significantly improved. Remarkably, a facile method to optimize anti-infective and osteogenic properties of medical titanium has been developed, and it was demonstrated that the ε-polylysine and gum Arabic multilayer composite films with assistance of polydopamine were able to endow the orthopedic implant materials both improved antibacterial property and excellent biocompatibility, which is of profound significance for practical application of titanium-based implants.

Multilayer porous Pd-WO3 composite thin films prepared by sol-gel process for hydrogen sensing

Based on sol-gel, multilayer porous Pd-WO3 composite thin films have been successfully prepared by utilizing a layer-by-layer deposition strategy. The crystal structure and microstructure were analyzed by various characterization methods. The sensing performance of the prepared films at different hydrogen concentrations and the temperature was studied. Results show that the performance of the hydrogen sensor can be improved greatly by the use of composite structure and soft template (Pluronic F127). The response performance of 1 mol% porous Pd-WO3 composite films was better than that of 2–10 mol% films. The porous Pd-WO3 composite films showed a high sensitivity (~346.5 times better than the sensitivity of pure WO3 films for 1000 ppm H2) and a fast response time (7 s) at the temperature of 250 °C. Porous Pd-WO3 composite films had good selectivity for hydrogen and stable sensing performance. The different response and recovery behavior of samples were contrasted and discussed to explain the effect of the special composite structure and porous structure on hydrogen sensing performance.

An alternating multilayer architecture boosts ultrahigh energy density and high discharge efficiency in polymer composites.

Poly(vinylidene fluoride) (PVDF)-based polymers with excellent flexibility and relatively high permittivity are desirable compared to the traditional bulk ceramic in dielectric material applications. However, the low discharge efficiency (<70%) caused by the severe intrinsic dielectric loss of these polymers result in a decrease in their breakdown strength and other problems, which limit their widespread applications. To address these outstanding issues, herein, we used a stacking method to combine poly(methyl methacrylate) (PMMA) with poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) for the synthesis of a series of alternating multilayer films with different layers. Benefitting from the blocking effect of the multilayer structure and excellent insulation performance of PMMA, simultaneous improvements in the breakdown strength and discharge efficiency of the multilayer films were achieved. Compared with the pure polymer films and other multilayer films with different layers, the film with a 9-layer structure exhibited the highest energy storage density of 25.3 J cm−3 and extremely high discharge efficiency of 84% at 728 MV m−1. Moreover, the charge and discharge performance of the other multilayer films were also better than that of P(VDF-HFP). In addition, it was also found that for the multilayer composite films with the same components, the blocking effect was reinforced with an increase in the number of layers, which led to a significant improvement in the breakdown strength. We consider that the multilayer structure can correlate with the dielectric properties of different polymer materials to enhance the energy storage of composite materials, and will provide a promising route to design high dielectric performance devices.

Impact of heat-treatment conditions on ferroelectric, ferromagnetic and magnetoelectric properties of multi-layered composite films of Ba0.9Ca0.1TiO3/CoFe2O4

The magnetoelectric films of Ba0.9Ca0.1TiO3(BCT)/CoFe2O4(CFO) were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel and spin-coating method under three kinds of heat-treatment conditions. It is shown that the heat-treatment conditions have a great effect on the ferroelectric, ferromagnetic and magnetoelectric properties of the composite films. Among the composite films prepared under three kinds of heat-treatment conditions, the composite films prepared under the complete heat-treatment condition (CHC composite films) have the best ferroelectric, ferromagnetic and magnetoelectric properties. They possess largest value of αE (82 mV cm−1 Oe−1). The complete heat-treatment condition is the most appropriate heat-treatment condition for obtaining the best magnetoelectric properties. Ferroelectric phase and ferromagnetic phase can coexist without inter-diffusion at the interface in CHC composite films.

Surface Instability of Composite Thin Films on Compliant Substrates: Direct Simulation Approach

Surface instability via wrinkle formation is a common feature in thin films attached to a compliant substrate. Wrinkled thin-film structures have been increasingly exploited to enhance device performance. In this study a numerical technique utilizing embedded imperfections is employed for direct simulations of wrinkle formation, extending from a single-film structure to composite films involving two or more layers. The incorporation of material elements, bearing different elastic properties at the film-substrate interface, assists in triggering buckling instability when the compressive strain reaches a critical value. The wrinkle wavelength and amplitude obtained from the numerical modeling show excellent agreements with available theoretical solutions involving bi-layer composite films, over the entire span of volume ratios of the constituent layers. A valid range of imperfection distribution, resulting in uniform wrinkle formation, is identified. The current numerical approach is robust and easy to implement and yields great promises in generating reliable wrinkling patterns. It can be readily applied to cases where realistic features cannot be captured by theories, such as the generalized plane strain deformation, indirect compression, and multilayer composite films.

Structure, phase transformation and corrosion resistance of CrAlN/CNx composite multilayer films in NaCl aqueous solution

Nanolayered CrAlN/CNx multilayer films (MFs) with varying modulation periods (thickness of the CNx layer: LCNx) were deposited by ion beam assisted magnetron sputtering. The morphologies and microstructures of these films were investigated. Results indicated that the CNx layer in the CrAlN/CNx-MFs transferred from an amorphous structure into polycrystalline body-centered cubic C3N4 when its thickness was less than 1.6 nm. The corrosion behavior of these CrAlN/CNx-MFs was investigated by polarization test and electrochemical impedance spectroscopy in a 3.5 wt% NaCl aqueous solution. Results showed that the multilayer structure could effectively increase the corrosion resistance of the alloy in the NaCl solution. The thick CrAlN layer accelerated the growth of perforative columnar defects as LCNx increased, which destroyed the compact structure, accelerated the infiltration of corrosive medium, and increased the probability of pitting corrosion. The CrAlN/CNx-MFs had a 1.6 nm thickness of laminated CNx, and their corrosion resistance was higher than those of the single layer CrAlN and single layer CNx because of the lack of surface cracks and pores.

Observation of inhomogeneous depinning in YBa2Cu3O7 composite multilayers

Composite multilayer films (CMLs) comprising YBa2Cu3O7 + BaHfO3 (4.7 vol%)/YBa2Cu3O7 + BaHfO3 (3.1 vol%) were fabricated, and vortex behavior in the CMLs was evaluated to discuss inhomogeneous depinning of vortices. Magnetic field and angular dependences of critical current density (Jc) in the CMLs were similar to those in the YBa2Cu3O7 + BaHfO3 (4.7 vol%) single layer film (SL). Variation of the CML structure shifted the matching field effect in global pinning force and irreversibility temperature. The Jc in the YBa2Cu3O7 + BaHfO3 (4.7 vol%) SL was smaller than that in the YBa2Cu3O7 + BaHfO3 (3.1 vol%) SL, suggesting that vortices preferentially moved along the low-Jc layers in the CMLs. The high-Jc layers pinned the vortices in the low-Jc layers, resulting in a shift of the matching field effect. These observations are characteristic of inhomogeneous depinning of vortices in the CMLs. The inhomogeneous depinning as well as pinned configuration should be considered for understanding Jc and for structural design of pinning centers in YBa2Cu3O7 films.

Construction of Dawson-Type Molybdovanadophosphoric Acid-Based Electrochemical Sensor and Its Application in Sensing Folic Acid

In current work, vanidium-substituted polyoxometalate clusters H8P2Mo16V2O62 and carbon nanotubes (CNTs)@Au NPs were incorporated into a multilayer composite film via combining layer-by-layer self-assembly. The result showed that the incorporation of the three kinds of active components would improve the electrocatalytic activity to the oxidation of FA and electron transfer rate greatly. In 0.2 M phosphate buffer solution (pH = 7.35), the composite film (PEI/P2Mo16V2/PEI/CNTs@Au)2 had a linear range of FA from 4.99 × 10-7 M to 1.29 × 10-5 M and 1.29 × 10-5 M to 1.21 × 10-3 M, and a limit of detection to be 3.96 × 10-8 M (S/N = 3). In addition, the composite film has an excellent anti-interference property to potential co-exist interfering species like inorganic ions and biomolecules (including NaCl, K2CO3, NH4Cl, NaNO2, Na2SO4, fructose, L-glutamate and glucose). The developed sensor has a good working and long-term stability as well. Besides, the sensor was applied in detecting FA in vitamin b tablet, the recoveries were all in the allowable error range. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.) Figure 1

Enzyme-free glucose sensor based on layer-by-layer electrodeposition of multilayer films of multi-walled carbon nanotubes and Cu-based metal framework modified glassy carbon electrode

A high-performance nonenzymatic glucose sensor was successfully prepared by a layer by layer strategy through electrodeposition assembling multilayer films of Cu-metal-organic frameworks/multi-walled carbon nanotubes (Cu-MOF/MWNTs) modified glassy carbon electrodes (GCE). Different multilayer films of Cu-MOF/MWNTs modified GCE (Cu-MOF/MWNTs/GCE) were prepared by repeating the electrodeposition of MWNTs onto the GCE in an MWNTs solution (MWNTs/GCE) and electrodeposition of the Cu-MOF layer onto the MWNTs film surface to form a Cu-MOF/MWNTs composite layer in the crystallization solution of Cu-MOF. Results confirmed that this method to fabricate multilayer composite films on the GCE was fast and convenient, and that multilayer composite films were stable and unified. The electrode modified by the multilayer composite films could effectively increase the exposure of active sites and increase the surface area of reactive contact. The GCE modified by eight layers (four multilayers Cu-MOF/MWNTs films) showed the optimum catalytic performance in the oxidation of glucose. The novel glucose sensor exhibited a wider detection linear range of 0.5 μM–11.84 mM, with a detection limit of 0.4 μM and a sensitivity of 3878 μA cm−2 mM−1. Moreover, the electrochemical response of the sensor on glucose was fast (within 0.3 s) and stable, exhibited good selectivity and was free of interference.

Composite multilayer films based on polyelectrolytes and in situ‐formed carbon nanostructures with enhanced photoluminescence and conductivity properties

ABSTRACTWe report a facile route for the fabrication of thin composite films based on polyelectrolytes and carbon nanostructures. Composite films were made by layer‐by‐layer assembly of polyelectrolyte multilayers utilizing embedded dextran sulfate (Dex) solution as a carbon source. Raman measurements indicate the formation of carbon nanostructures from the Dex precursor over the whole film. Formation of these nanostructures results in enhanced photoluminescence and an increase in conductivity by two orders of magnitude to about 0.055 S cm−1. The latter corresponds to the level of wide‐gap semiconductors, in contrast to the initial insulating polyelectrolyte film. A distinct peak of photoluminescence of the films is found in the blue region at the wavelength of 450 nm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47718.