Multilayer Films Research Articles

Effects of Ta and W insertion on thermal stability in Co2FeAl/HM/Co2FeAl multilayers

In this paper, by inserting a certain thickness of the Ta and W into the Ta (5)/MgO (1)/Co2FeAl (1.5)/HM/Co2FeAl (1.5)/MgO (1)/Ta (2) multilayer films, the thermal stability of the multilayers is regulated. When Ta is inserted, the sample shows perpendicular magnetic anisotropy (PMA) in the as-deposited state, but the thermal stability is only maintained at 250 °C; when Ta is replaced with a W insertion, the thermal stability is increased to 450 °C.The XPS results show that after annealing at 350°C, Ta diffused into the ferromagnetic layer to absorb oxygen atoms, resulting in underxidation of Fe and Co, and PMA disappeared in films with Ta insertion. During the preparation of the film with W insertion, the oxygen in MgO sputtered onto the ferromagnetic layer, resulting in excessive oxidation of Fe and Co in films, so the as-deposited film shows in-plane magnetic anisotropy (IMA). However, after annealing at 350 °C, FeOx and CoOx were reduced, and some oxygen atoms returned to MgO. The oxidation state in the ferromagnetic layer is adjusted to the ideal level. Additionally, the roughness of the CFA/MgO interface of the films with W insertion was reduced, so the films with W insertion after annealing still maintained good PMA.

Development of multilayer composite film based on protein‐polysaccharides with the addition of onion waste extracts and their impact on the shallot quality

AbstractAt present, multilayer composite film is attractive in the production of biodegradable films due to its essential film properties. The current study mainly focused on overcoming the problems of poor water barrier and mechanical strength observed in monolayer films (SA‐CMC and G/SA‐CMC) made from gluten (G), sodium alginate (SA), and carboxymethylcellulose (CMC). The film was developed with the addition of onion waste extracts (OWEs), primarily from peel and stalk, to enhance functional properties. The multilayer composite film consists of three layers: an outer layer made of G, an inner layer made of SA, CMC, and a middle layer made of G/SA‐CMC. The developed composite film exhibited improved physical properties (thickness: 0.348–0.629 mm and moisture: 20.889%–21.403%), mechanical properties (tensile strength: 21.943–20.640 MPa), and barrier properties (WVP: 0.212–0.516 g/m.s.Pa × 10−14) compared to monolayer films (SA‐CMC and G/SA‐CMC). The addition of OWEs enhanced the multilayer film's phenolic (20.076 and 36.175 mgGAE/g) and antioxidant activity (73.850% and 42.667%). The study found that the multilayer control film had minimal changes in weight loss (9.75% ± 0.18%) and firmness (6.68 ± 0.64 N) compared to OWEs‐added films (9.93% ± 0.49–10.02% ± 0.14% and 6.61 ± 0.37 to 6.64 ± 0.18 N). However, fresh‐peeled shallot onion packed with control film exhibited higher bacterial counts (6.70 ± 0.42 CFU/g) and yeast and mold counts (5.08 ± 0.20 CFU/g) than those packed with the OWEs‐added film (6.49 ± 0.28–6.56 ± 0.27 CFU/g and 4.75 ± 0.18–4.89 ± 0.21 CFU/g), indicating that OWEs protect the onions from microbial degradation. Overall, the multilayer control film (without OWEs) showed better results for storing the fresh‐peeled shallot onion at 4°C for 21 days.Highlights Onion waste extracts have potent high antioxidant and antimicrobial properties Multilayer film's physical, mechanical, barrier, and functional properties improved Addition of onion waste extracts increased the film's antimicrobial activity Control film showed a better effect for storing fresh‐peeled shallot onion Developed film can store fresh‐peeled shallot onion for 21 days at 4°C.

A novel approach to obtain superior microwave absorption using Non-Conducting polymer jacket coated Multi-Layer Hexaferrite-TMDC nanocomposite film

This article represents the imposing electromagnetic interference (EMI) shielding behaviour of non-conducting polymer jacket-coated Co2Y-hexaferrite-MoS2 binary nanofillers incorporated PVDF multi-layer nanocomposite films. The presence of Co2Y-hexaferrite inside PVDF enhanced the magnetic permeability, whereas the incorporation of semiconducting transition metal dichalcogenide (TMDC), MoS2, inside the PVDF matrix improves the polarization effects of the nanocomposite films. The crystalline phases corresponding to Co2Y-hexaferrite, MoS2 nanoparticles and the multi-phase nanocomposite films have been justified using XRD analysis and Rietveld refinement study. FESEM micrographs confirm the hexagonal and cotton-ball structures of Co2Y-hexaferrite and MoS2 nanoparticles, respectively; in addition, the presence of Co2Y-MoS2 binary nanofillers inside the PVDF matrix has been confirmed. The stability of the nanocomposite films against electrical breakdown is clearly demonstrated by the minimum leakage current observed at 90 kV/m under J-E characteristics. The room temperature maximum magnetization of 33.32 emu/g of Co2Y-hexaferrite at an external magnetic field of 50,000 Oe helps in incurring magnetic losses and the corresponding improvement of shielding effectiveness due to absorption (SEA) of the nanocomposite films. This article demonstrates the modulation of SEA of the nanocomposite films depending on both the binary nanofillers loading percentage inside PVDF and the thickness of the nanocomposite films. Also, a unique mechanism corresponding to the coating of a non-conducting polymer jacket over a multi-layer structure has been opted herein to improve SEA in the frequency range of 12–18 GHz. This unique mechanism demonstrates that the maximum SEA for the non-conducting polymer jacket-coated multi-layer nanocomposite film is −51.23 dB at 14.03 GHz, and the corresponding total shielding effectiveness (SET) is −74.51 dB at 13.23 GHz, along with > 99.9999 % attenuation.

Metamaterial structure design based on genetic algorithm and phase change material GST for multispectral camouflage

This study proposes a multispectral camouflage tunable multilayer film metamaterial (TMFM) with thermal management function based on genetic algorithm (GA), which is composed of ZnS/YbF3/Ge/Ge2Sb2Te5 (GST)/Au multilayer film. Through numerical analysis, we assess its efficacy in visible-infrared compatibility camouflage and radiative heat dissipation. Within the visible light band, different structural colors can be produced by adjusting the thickness of the ZnS film. The average emissivity within the 3–5 μm and 8–14 μm infrared bands is measured at 0.04 and 0.14, respectively. The low emissivity facilitates effective thermal management. Moreover, an average emissivity of 0.52 within the 5–8 μm range is instrumental in achieving efficient radiation heat dissipation. Laser stealth capability is further enhanced, with an emissivity reaching 0.70 at 10.6 μm. Therefore, this metamaterial structure has broad application prospects in both military and civilian industrial fields.

Preparation and characterization of ZnS/metal/ZnS transparent conductive multilayer films with different metal layers

ZnS/metal/ZnS transparent conductive multilayer films were deposited on quartz glass by pulsed laser deposition at room temperature with Au, Ag and Cu as the metal layers, and annealed in air at 100, 200 and 300℃ for 1 h. XRD patterns show that β -ZnS(111) diffraction peak of ZnS/Au/ZnS is stronger and sharper than the other two samples, indicating that its crystalline quality is the best. SEM images show the good structural homogeneity of the samples with smooth and compact film surfaces. When the annealing temperature increases from 100 to 300℃, the sheet resistance decreases first and then increases, while the carrier concentration changes in the opposite trend. The maximum transmittance (~85%) for ZnS/Au/ZnS in the visible light region is observed when the sample is annealed at 200℃. The figure of merit is calculated, and the best sample suitable for transparent conductive electrode is determined.

WO3/Cu2O-CuO and WO3/Au/Cu2O-CuO heterojunctions photocatalysts for self-cleaning and photocatalytic degradation of organic pollutants applications

In this work, a high-performance WO3/Au/Cu2O-CuO heterojunctions was deposited via dc reactive magnetron sputtering, which displayed superhydrophilicity conversion and superior photocatalytic performance for the degradation of methylene blue. WO3, WO3/Cu2O-CuO, WO3/Au and WO3/Au/Cu2O-CuO heterojunctions were sputtered on precleaned glass and Si(100) substrates. The chemical composition, crystal structure, surface morphology, optical absorption, water contact angle and photocatalytic activities of the prepared single and multilayers films were examined to elucidate the correlation between structure and other properties. SEM revealed tiny small nanoparticles for WO3 film, close-packed nanoparticles for WO3/Cu2O-CuO multilayers and nanoparticles with more open structure for WO3/Au/Cu2O-CuO heterojunctions. The WO3/Au/Cu2O-CuO heterojunctions had the highest optical absorption. The estimated band gap values were 3.16, 3.08, 2.97 and 2.65 eV for WO3, WO3/Cu2O-CuO, WO3/Au and WO3/Au/Cu2O-CuO, respectively. The WO3/Cu2O-CuO, WO3/Au and WO3/Au/Cu2O-CuO became superhydrophilic after UV illumination. The remarkable photocatalytic activities of WO3/Au/Cu2O-CuO is attributed to the enhanced efficiency of separation for photogenerated hole–electron pairs.

Thermal stress concentration points and stress mutations in nano-multilayer film structures

Abstract In the multilayer film-substrate system, the buckling, delamination and cracking of the film caused by the thermal stress concentration point and the stress mutation are the main factors leading to the failure of the corresponding device function. In this paper, we studied the multilayer film system composed of the substrate and the three-layer film. The thermal stress distribution inside the structure was calculated by the finite element method (FEM). It was observed that there was a large thermal stress difference between the layers. This is mainly due to the mismatch of thermal expansion coefficient (CTE) between materials. Different materials have different degrees of change with the external environment temperature, and the layers are squeezed. In particular, there are obvious thermal stress concentration points at the corners of the base layer and the transition layer, which is due to the sudden change of the shape at the geometric section of the structure, resulting in a sudden increase in local stress. In order to solve this problem, we have chamfered the substrate and added an intermediate layer between the substrate and the transition layer to analyze whether the difference between the thermal stress concentration point and the thermal stress can be reduced or eliminated, and the service life of the multilayer structure can be extended. The conclusion shows that chamfering and increasing the intermediate layer can reduce the stress mutation and weaken the thermal stress concentration point, which can effectively improve the interlayer bonding strength.

Laboratorial investigation on optical, thermal and pavement performance of biomimetic dark reflective coatings with composite structure for pavement cooling

The surface temperature of asphalt pavement in summer can reach up to 70 °C, which leads to poor outdoor thermal comfort and exacerbates the urban heat island effect. Reflective coatings can effectively reduce pavement temperature, but their intrinsic light color with high reflectance causes safety issues such as glaring. In this study, based on the biomimetic idea of chameleon skin structure, composite pavement coatings for cooling and anti-glare were developed. Their optical properties, thermal behavior, adhesion and skid-resistance performances were investigated. The results showed that near-infrared reflectance of black and grey double-layer reflective coatings could reach 0.66 and 0.70, respectively (58 % higher than single-layer coatings). The optimal mass fraction of perylene black in the upper black/grey coating was 2.94 % and 0.74 %, respectively. The double-layer dark coatings could decrease the temperature by 14 °C at the depth of 3 cm below road surface, which achieved cooling effect close to that of white single-layer reflective coatings. The adhesion between coating and stone was generally higher than the cohesion of asphalt, therefore, opening traffic for a period of time or carrying out micro-milling before coating could improve the abrasion resistance. Due to increase in the thickness of the double-layer coating, the microscopic texture of road surface was reduced, thereby reducing skid-resistance. However, it still met the standard requirements. This study intends to provide a reference for developing pavement coatings that balance cooling and visual safety to mitigate the heat island effect, and improve the sustainability of transportation infrastructure.

Study on damage of CRTS II slab tracks in coated-uncoated transition zones subjected to temperature and train loads

The CRTS II ballastless track is sensitive to temperature due to its longitudinal continuity. The application of reflective insulation coating can efficiently lower the temperature of the track slab, thereby decelerating track deterioration. Given the considerable length of high-speed railway lines, the application of reflective insulation coatings leads to numerous transitions between coated and uncoated sections. This study investigates the influence of reflective insulation coatings on the structural damage of coated-uncoated transition zones in railways. To this end, a CRTS II slab track model involving the bilinear cohesive zone model and the concrete plastic damage model is established. The model examines the combined impact of high temperature and train loading, aiming to investigate the damage patterns within the coated-uncoated transition zone of the track. The results indicate: (1) During high temperature loading, the center of the track slab layer is predisposed to warping compared to the sides. (2) If the cohesion parameter falls below 0.04 MPa, augmenting the cohesion model parameter effectively alleviates track slab arching. (3) In instances where the track slab lacks complete coverage of reflective insulation coatings, train loading may shift the location of the maximum vertical displacement and interface failure mode.

Multilayer film coating for laser ion source target for increase of low charge state production

The use of Laser Ion Source for accelerator facilities has the advantage to tune the characteristic of the produced beams by changing the laser parameters using the same primary target. The advantageous and innovative opportunity to manipulate the characteristic of charge state distributions by the use of composed target, may open new possibilities for the ion sources. In this experiment we characterize and study the plasma produced by the laser ablation of coated targets at constant laser parameters. The performed investigation has the double purpose to have a better understanding of penetration depth of laser in composed materials and understand how to tune the charge states by adding coating films. The obtained results showed that for particular thickness of coating, the low charge states were produced with higher yield than in the case of pure material.

Boosting third-order optical nonlinearity in ITO/Au multilayer films via interfacial effects

We present the enhancement of third-order optical nonlinearity in indium tin oxide (ITO)/Au multilayer films via interfacial effects. The overall thickness of prepared ITO and Au layer was kept as 200 nm and 14 nm, respectively, and thus multilayers are 214 nm, i.e., for the sandwich structure ITO/Au/ITO, the thickness of ITO and Au is 100 nm and 14 nm, respectively, while the thickness of ITO and Au is 40 nm and 3.5 nm in the nine-layer films composed of five layers of ITO and four layers of Au. The measured nonlinear refractive index (n2) and absorption coefficient (β) of the multilayers rise as the number of layers increases. The maximum n2 and β in the nine-layer film are 2.6×10−14 m2/W and −3.7×10−8 m/W, which are 3.8 and 2.3 times larger than the values in the pure ITO film, respectively. Such enhancement of optical nonlinearity as the number of layers increases originates from the increase of carrier concentrations in multilayers due to contact of metals/semiconductors (interfacial effects), not following the traditional effective media theory and epsilon-near-zero effect. The results pave a way to modulate the optical nonlinearity in special metal-dielectric multilayers of interfacial effects and indicates the promising applications in nonlinear photonics.

Simulations of Infrared Reflectivity and Transmission Phonon Spectra for Undoped and Doped GeC/Si (001).

Exploring the phonon characteristics of novel group-IV binary XC (X = Si, Ge, Sn) carbides and their polymorphs has recently gained considerable scientific/technological interest as promising alternatives to Si for high-temperature, high-power, optoelectronic, gas-sensing, and photovoltaic applications. Historically, the effects of phonons on materials were considered to be a hindrance. However, modern research has confirmed that the coupling of phonons in solids initiates excitations, causing several impacts on their thermal, dielectric, and electronic properties. These studies have motivated many scientists to design low-dimensional heterostructures and investigate their lattice dynamical properties. Proper simulation/characterization of phonons in XC materials and ultrathin epilayers has been challenging. Achieving the high crystalline quality of heteroepitaxial multilayer films on different substrates with flat surfaces, intra-wafer, and wafer-to-wafer uniformity is not only inspiring but crucial for their use as functional components to boost the performance of different nano-optoelectronic devices. Despite many efforts in growing strained zinc-blende (zb) GeC/Si (001) epifilms, no IR measurements exist to monitor the effects of surface roughness on spectral interference fringes. Here, we emphasize the importance of infrared reflectivity Rω and transmission Tω spectroscopy at near normal θi = 0 and oblique θi ≠ 0 incidence (Berreman effect) for comprehending the phonon characteristics of both undoped and doped GeC/Si (001) epilayers. Methodical simulations of Rω and Tω revealing atypical fringe contrasts in ultrathin GeC/Si are linked to the conducting transition layer and/or surface roughness. This research provided strong perspectives that the Berreman effect can complement Raman scattering spectroscopy for allowing the identification of longitudinal optical ωLO phonons, transverse optical ωTO phonons, and LO-phonon-plasmon coupled ωLPP+ modes, respectively.

Microstructure and corrosion properties of Al1-xWxN coatings for potential use in gas turbine blades

Herein, a numerical approach of Al1-xWxN thin film coatings on Inconel 738LC superalloys for thermal barrier applications has been studied and the experimental analysis includes deposition of Al1-xWxN films on Si (100), glass and transparent quartz substrates at 40 % N2 flow rate using a dual target DC reactive magnetron sputtering technique to investigate the morphology, microstructure, chemical bonding and corrosion behaviour. AFM analysis revealed the rms roughness, Sq and average roughness, Sa increased with the increasing W content from 22 to 70 at.%. It was found that Al1-xWxN films tend to form tiny valleys on the film surface because the values of surface skewness, Ssk lie below zero. The TEM image showed a branched snowflake structure for the specimen of Al0.58W0.42N films with discrete spots in the SAED pattern, confirming the microcrystalline nature. The blue-shifting of Ecorr towards positive potential confirmed the lower corrosion resistance of WN films than those of AlN. XRD spectra of Al0.58W0.42N films showed an amorphous nature devoid of peaks, which is also confirmed by the SAED pattern. The quasi-passive oxide layer formation was spontaneous for WN films compared to the AlN films. The bending vibrations of AlN and WN showed the coordination environment of the metal centre in the Al1-xWxN films. The computational results indicated that the thermal barrier properties of Al1-xWxN films decreased with the increasing W content, i.e., AIN > Al0.58 W0.42N > WN.

XRF mapping for identifying inhomogeneity of elemental distribution in multi-layer flexible films for attenuating X-rays

XRF mapping for identifying inhomogeneity of elemental distribution in multi-layer flexible films for attenuating X-rays

Reversible Solar Heating and Radiative Cooling Devices via Mechanically Guided Assembly of 3D Macro/Microstructures.

Solar heating and radiative cooling are promising solutions for decreasing global energy consumption because these strategies use the Sun (≈5800K) as a heating source and outer space (≈3K) as a cooling source. Although high-performance thermal management can be achieved using these eco-friendly methods, they are limited by daily temperature fluctuations and seasonal changes because of single-mode actuation. Herein, reversible solar heating and radiative cooling devices formed via the mechanically guided assembly of 3D architectures are demonstrated. The fabricated devices exhibit the following properties: i) The devices reversibly change between solar heating and radiative cooling under uniaxial strain, called dual-mode actuation. ii) The 3D platforms in the devices can use rigid/soft materials for functional layers owing to the optimized designs. iii) The devices can be used for dual-mode thermal management on a macro/microscale. The devices use black paint-coated polyimide (PI) films as solar absorbers with multilayered films comprising thin layers of polydimethylsiloxane/silver/PI, achieving heating and cooling temperatures of 59.5 and -11.9°C, respectively. Moreover, mode changes according to the angle of the 3D structures are demonstrated and the heating/cooling performance with skin, glass, steel, aluminum, copper, and PI substrates is investigated.

Frictional properties and environmental adaptability of Ti-MoS2/WC multilayer films

Magnetron-sputtered molybdenum disulfide films are extensively utilized as solid lubricating coatings in space applications as a result of their low friction coefficient and minimal contamination. However, MoS2-based films are sensitive to hygrothermal and oxidation environment, and are easily oxidized to form MoO3, which results in high friction and wear of the films, significantly reducing their operational lifespan. Especially when the spacecraft adopts the launching mode of coastal launch or ocean platform, the performance deterioration caused by oxidation of MoS2 films during transportation, storage and launch is more serious. Therefore, to enhance the frictional performance and oxidation resistance of the films in humid and salt spray environments, the Ti-MoS2/WC multilayer films with preferred (002) crystal plane orientation were prepared, achieving a friction coefficient of 0.009 in a vacuum environment and a wear rate of 1.1×10-7 mm3/N∗m. In particular, the film can maintain this extremely low coefficient of friction even after exposure to moisture or salt spray. These findings demonstrate that the dual doping of Ti and WC and the design of multilayer structures enable MoS2 films to achieve outstanding frictional performance and oxidation resistance. This is crucial for designing MoS2 films with excellent environmental adaptability.

Expansivity of Fused Quartz Glass Measured Within 6×10-10K-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6 \ imes 10^{-10}\\,\ ext{K}^{-1}$$\\end{document}

A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from fused quartz glass. The standard uncertainty in the measurement was less than 0.6 (nm·m-1)·K-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\ extrm{nm}{\\cdot } \ extrm{m}^{-1}){\\cdot }\ extrm{K}^{-1}$$\\end{document}, or 0.15 %. The limit on performance is arguably uncertainty in the reflection phase-shift temperature dependence, because neither thermooptic nor thermal expansion coefficients of thin-film coatings are reliably known. However, several other uncertainty contributors are at the same level of magnitude, and so any improvement in performance would entail significant effort. Furthermore, measurements of three different samples revealed that material inhomogeneity leads to differences in the effective thermal expansion coefficient of fused quartz; inhomogeneity in thermal expansion among samples is 24 times larger than the measurement uncertainty in a single sample.

Effects of Intermetallic Phase Formation and Bilayer Spacing on the Oxygen Exchange Process in Mg–CuO Reactive Multilayer Films

Effects of Intermetallic Phase Formation and Bilayer Spacing on the Oxygen Exchange Process in Mg–CuO Reactive Multilayer Films

Polyarylene ether nitrile/boron nitride nanosheets thermally conductive films through heterogeneous multilayer electrostatic spinning

Thermal management materials with excellent thermal conductivity and electrical insulation are highly favorable in the modern integrated electronic areas. In present work, a novel polyarylene ether nitrile (PEN) composite film, integrating thermal conductivity, electrical insulation, and flexibility, was fabricated utilizing a hybrid approach combining heterogeneous multilayer electrostatic spinning with a subsequent hot pressing technique. BNNS acts as a thermally conductive filler which builds a good thermal conduction pathway, and PEN acts as a bonding agent which ensures the flexibility and insulation of the film. Heterogeneous multilayer electrostatic spinning ensures the formation of thermal conduction pathways. Compared to conventional composite film, heterogeneous multilayer film shows excellent thermal conductivity, increases by 83% in-plane, and 71% through-plane, respectively. Therefore, This work will provide a technological reserve for the preparation of thermally conductive and insulating flexible films.

Biobased Self-Healing Thin Film Coatings Based on Poly (Itaconic Acid Esters).

Paper used for packaging applications is often coated with thin polymer coatings to improve the properties, like printability and barrier properties, respectively. Today, these coatings are still often based on petroleum-based polymers. In this study, the fabrication of biobased thin film coatings is described. Poly(itaconic acid ester)s, which are prepared by emulsion polymerization, are used as water-based coatings for paper. The thermal properties of the polymers are tuned by the side chain of the monomers (diethyl itaconate vs. dibutyl itaconate). Different formulations based on the polymer emulsion and additives, like rheology modifiers, are prepared and their film formation is studied. The usage of a rheology modifier results in excellent film formation. These polymer coatings feature an additional function - they are capable of self-healing. The healing ability is studied in scratch healing tests, in which almost complete recovery can be observed after healing at 100 °C. Moreover, the restoration of optical properties/aesthetics is studied. In gloss measurements before and after damage as well as after a healing time the complete recovery of the gloss can be observed. Furthermore, the barrier properties against fat are studied.