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Search Results (2,270)

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Keywords = film-substrate structures

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14 pages, 6988 KiB  
Article
Effect of Substrate Temperature on the Structural, Morphological, and Infrared Optical Properties of KBr Thin Films
by Teng Xu, Qingyuan Cai, Weibo Duan, Kaixuan Wang, Bojie Jia, Haihan Luo and Dingquan Liu
Materials 2025, 18(15), 3644; https://doi.org/10.3390/ma18153644 (registering DOI) - 3 Aug 2025
Abstract
Potassium bromide (KBr) thin films were deposited by resistive thermal evaporation at substrate temperatures ranging from 50 °C to 250 °C to systematically elucidate the temperature-dependent evolution of their physical properties. Structural, morphological, and optical characteristics were examined by X-ray diffraction (XRD), scanning [...] Read more.
Potassium bromide (KBr) thin films were deposited by resistive thermal evaporation at substrate temperatures ranging from 50 °C to 250 °C to systematically elucidate the temperature-dependent evolution of their physical properties. Structural, morphological, and optical characteristics were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). The results reveal a complex, non-monotonic response to temperature rather than a simple linear trend. As the substrate temperature increases, growth evolves from a mixed polycrystalline texture to a pronounced (200) preferred orientation. Morphological analysis shows that the film surface is smoothest at 150 °C, while the microstructure becomes densest at 200 °C. These structural variations directly modulate the optical constants: the refractive index attains its highest values in the 150–200 °C window, approaching that of bulk KBr. Cryogenic temperature (6 K) FTIR measurements further demonstrate that suppression of multi-phonon absorption markedly enhances the infrared transmittance of the films. Taken together, the data indicate that 150–200 °C constitutes an optimal process window for fabricating KBr films that combine superior crystallinity, low defect density, and high packing density. This study elucidates the temperature-driven structure–property coupling and offers valuable guidance for optimizing high-performance infrared and cryogenic optical components. Full article
(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))
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37 pages, 5131 KiB  
Review
Coating Metal–Organic Frameworks (MOFs) and Associated Composites on Electrodes, Thin Film Polymeric Materials, and Glass Surfaces
by Md Zahidul Hasan, Tyeaba Tasnim Dipti, Liu Liu, Caixia Wan, Li Feng and Zhongyu Yang
Nanomaterials 2025, 15(15), 1187; https://doi.org/10.3390/nano15151187 (registering DOI) - 2 Aug 2025
Abstract
Metal–Organic Frameworks (MOFs) have emerged as advanced porous crystalline materials due to their highly ordered structures, ultra-high surface areas, fine-tunable pore sizes, and massive chemical diversity. These features, arising from the coordination between an almost unlimited number of metal ions/clusters and organic linkers, [...] Read more.
Metal–Organic Frameworks (MOFs) have emerged as advanced porous crystalline materials due to their highly ordered structures, ultra-high surface areas, fine-tunable pore sizes, and massive chemical diversity. These features, arising from the coordination between an almost unlimited number of metal ions/clusters and organic linkers, have resulted in significant interest in MOFs for applications in gas storage, catalysis, sensing, energy, and biomedicine. Beyond their stand-alone properties and applications, recent research has increasingly explored the integration of MOFs with other substrates, particularly electrodes, polymeric thin films, and glass surfaces, to create synergistic effects that enhance material performance and broaden application potential. Coating MOFs onto these substrates can yield significant benefits, including, but not limited to, improved sensitivity and selectivity in electrochemical sensors, enhanced mechanical and separation properties in membranes, and multifunctional coatings for optical and environmental applications. This review provides a comprehensive and up-to-date summary of recent advances (primarily from the past 3–5 years) in MOF coating techniques, including layer-by-layer assembly, in situ growth, and electrochemical deposition. This is followed by a discussion of the representative applications arising from MOF-substrate coating and an outline of key challenges and future directions in this rapidly evolving field. This article aims to serve as a focused reference point for researchers interested in both fundamental strategies and applied developments in MOF surface coatings. Full article
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13 pages, 1717 KiB  
Article
High-Performance Hydrogen Gas Sensor Based on Pd-Doped MoS2/Si Heterojunction
by Enyu Ma, Zihao Xu, Ankai Sun, Shuo Yang and Jianyu Jiang
Sensors 2025, 25(15), 4753; https://doi.org/10.3390/s25154753 (registering DOI) - 1 Aug 2025
Viewed by 56
Abstract
High-performance hydrogen gas sensors have gained considerable interest for their crucial function in reducing H2 explosion risk. Although MoS2 has good potential for chemical sensing, its application in hydrogen detection at room temperature is limited by slow response and incomplete recovery. [...] Read more.
High-performance hydrogen gas sensors have gained considerable interest for their crucial function in reducing H2 explosion risk. Although MoS2 has good potential for chemical sensing, its application in hydrogen detection at room temperature is limited by slow response and incomplete recovery. In this work, Pd-doped MoS2 thin films are deposited on a Si substrate, forming Pd-doped MoS2/Si heterojunctions via magnetron co-sputtering. The incorporation of Pd nanoparticles significantly enhances the catalytic activity for hydrogen adsorption and facilitates more efficient electron transfer. Owing to its distinct structural characteristics and sharp interface properties, the fabricated Pd-doped MoS2/Si heterojunction device exhibits excellent H2 sensing performance under room temperature conditions. The gas sensor device achieves an impressive sensing response of ~6.4 × 103% under 10,000 ppm H2 concentration, representing a 110% improvement compared to pristine MoS2. Furthermore, the fabricated heterojunction device demonstrates rapid response and recovery times (24.6/12.2 s), excellent repeatability, strong humidity resistance, and a ppb-level detection limit. These results demonstrate the promising application prospects of Pd-doped MoS2/Si heterojunctions in the development of advanced gas sensing devices. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Sensing Technology)
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12 pages, 2346 KiB  
Article
SERS and Chiral Properties of Cinnamic Acid Derivative Langmuir-Blodgett Films Complexed with Dyes
by Xingdi Zhao, Xinyu Li, Pengfei Bian, Qingrui Zhang, Yuqing Qiao, Mingli Wang and Tifeng Jiao
Coatings 2025, 15(8), 890; https://doi.org/10.3390/coatings15080890 (registering DOI) - 1 Aug 2025
Viewed by 105
Abstract
Chiral molecules are crucial in the field of optical devices, molecular recognition, and other novel functional materials due to their unique spatially asymmetric configuration and optical activity. In this study, a chiral molecule, Cholest-3-yl (E)-3-(4-carbamoylphenyl)acrylate (CCA), was combined with dyes containing large conjugated [...] Read more.
Chiral molecules are crucial in the field of optical devices, molecular recognition, and other novel functional materials due to their unique spatially asymmetric configuration and optical activity. In this study, a chiral molecule, Cholest-3-yl (E)-3-(4-carbamoylphenyl)acrylate (CCA), was combined with dyes containing large conjugated structures, tetramethylporphyrin tetrasulfonic acid (TPPS), and Nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (TsNiPc), and composite LB films of CCA/TPPS and CCA/TsNiPc were successfully prepared by using Langmuir-Blodgett (LB) technology. The circular dichroism (CD) test proved that the CCA/TPPS composite film had a strong CD signal at 300–400 nm, and the composite film showed chirality. This significant optical activity provides a new idea and option for the application of LB films in chiral sensors. In the Surface Enhanced Raman Spectroscopy (SERS) test, the CCA/TPPS composite film was sensitive to signal sensing, in which the enhancement factor EF = 2.28 × 105, indicating that a large number of effective signal response regions were formed on the surface of the film, and the relative standard deviation (RSD) = 12.08%, which demonstrated that the film had excellent uniformity and reproducibility. The high sensitivity and low signal fluctuation make the CCA/TPPS composite LB film a promising SERS substrate material. Full article
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16 pages, 993 KiB  
Article
Optical and Photoconversion Properties of Ce3+-Doped (Ca,Y)3(Mg,Sc)2Si3O12 Films Grown via LPE Method onto YAG and YAG:Ce Substrates
by Anna Shakhno, Vitalii Gorbenko, Tetiana Zorenko, Aleksandr Fedorov and Yuriy Zorenko
Materials 2025, 18(15), 3590; https://doi.org/10.3390/ma18153590 - 30 Jul 2025
Viewed by 160
Abstract
This work presents a comprehensive study of the structural, luminescent, and photoconversion properties of epitaxial composite phosphor converters based on single crystalline films of Ce3+-activated Ca2−xY1+xMg1+xSc1−xSi3O12:Ce (x = 0–0.25) [...] Read more.
This work presents a comprehensive study of the structural, luminescent, and photoconversion properties of epitaxial composite phosphor converters based on single crystalline films of Ce3+-activated Ca2−xY1+xMg1+xSc1−xSi3O12:Ce (x = 0–0.25) (CYMSSG:Ce) garnet, grown using the liquid phase epitaxy (LPE) method on single-crystal Y3Al5O12 (YAG) and YAG:Ce substrates. The main goal of this study is to elucidate the structure–composition–property relationships that influence the photoluminescence and photoconversion efficiency of these film–substrate composite converters, aiming to optimize their performance in high-power white light-emitting diode (WLED) applications. Systematic variation in the Y3+/Sc3+/Mg2+ cationic ratios within the garnet structure, combined with the controlled tuning of film thickness (ranging from 19 to 67 µm for CYMSSG:Ce/YAG and 10–22 µm for CYMSSG:Ce/YAG:Ce structures), enabled the precise modulation of their photoconversion properties. Prototypes of phosphor-converted WLEDs (pc-WLEDs) were developed based on these epitaxial structures to assess their performance and investigate how the content and thickness of SCFs affect the colorimetric properties of SCFs and composite converters. Clear trends were observed in the Ce3+ emission peak position, intensity, and color rendering, induced by the Y3+/Sc3+/Mg2+ cation substitution in the film converter, film thickness, and activator concentrations in the substrate and film. These results may be useful for the design of epitaxial phosphor converters with tunable emission spectra based on the epitaxially grown structures of garnet compounds. Full article
(This article belongs to the Section Materials Physics)
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16 pages, 3091 KiB  
Article
Fabrication and Evaluation of Screen-Printed Electrodes on Chitosan Films for Cardiac Patch Applications with In Vitro and In Vivo Evaluation
by Yu-Hsin Lin, Yong-Ji Chen, Jen-Tsai Liu, Ching-Shu Yen, Yi-Zhen Lin, Xiu-Wei Zhou, Shu-Ying Chen, Jhe-Lun Hu, Chi-Hsiang Wu, Ching-Jung Chen, Pei-Leun Kang and Shwu-Jen Chang
Polymers 2025, 17(15), 2088; https://doi.org/10.3390/polym17152088 - 30 Jul 2025
Viewed by 229
Abstract
Myocardial infarction (MI) remains one of the most common cardiovascular diseases and a leading cause of morbidity and mortality worldwide. In recent years, natural polymeric patches have attracted increasing attention as a promising therapeutic platform for myocardial tissue repair. This study explored the [...] Read more.
Myocardial infarction (MI) remains one of the most common cardiovascular diseases and a leading cause of morbidity and mortality worldwide. In recent years, natural polymeric patches have attracted increasing attention as a promising therapeutic platform for myocardial tissue repair. This study explored the fabrication and evaluation of screen-printed electrodes (SPEs) on chitosan film as a novel platform for cardiac patch applications. Chitosan is a biodegradable and biocompatible natural polymer that provides an ideal substrate for SPEs, providing mechanical stability and promoting cell adhesion. Silver ink was employed to enhance electrochemical performance, and the electrodes exhibited strong adhesion and structural integrity under wet conditions. Mechanical testing and swelling ratio analysis were conducted to assess the patch’s physical robustness and aqueous stability. Silver ink was employed to enhance electrochemical performance, which was evaluated using cyclic voltammetry. In vitro, electrical stimulation through the chitosan–SPE patch significantly increased the expression of cardiac-specific genes (GATA-4, β-MHC, troponin I) in bone marrow mesenchymal stem cells (BMSCs), indicating early cardiogenic differentiation potential. In vivo, the implantation of the chitosan–SPE patch in a rat MI model demonstrated good tissue integration, preserved myocardial structure, and enhanced ventricular wall thickness, indicating that the patch has the potential to serve as a functional cardiac scaffold. These findings support the feasibility of screen-printed electrodes fabricated on chitosan film substrates as a cost-effective and scalable platform for cardiac repair, offering a foundation for future applications in cardiac tissue engineering. Full article
(This article belongs to the Section Polymer Applications)
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24 pages, 5342 KiB  
Article
Esterase and Peroxidase Are Involved in the Transformation of Chitosan Films by the Fungus Fusarium oxysporum Schltdl. IBPPM 543
by Natalia N. Pozdnyakova, Tatiana S. Babicheva, Daria S. Chernova, Irina Yu. Sungurtseva, Andrey M. Zakharevich, Sergei L. Shmakov and Anna B. Shipovskaya
J. Fungi 2025, 11(8), 565; https://doi.org/10.3390/jof11080565 - 29 Jul 2025
Viewed by 234
Abstract
The majority of studies of fungal utilization of chitosan are associated with the production of a specific enzyme, chitosanase, which catalyzes the hydrolytic cleavage of the macrochain. In our opinion, the development of approaches to obtaining materials with new functional properties based on [...] Read more.
The majority of studies of fungal utilization of chitosan are associated with the production of a specific enzyme, chitosanase, which catalyzes the hydrolytic cleavage of the macrochain. In our opinion, the development of approaches to obtaining materials with new functional properties based on non-destructive chitosan transformation by living organisms and their enzyme systems is promising. This study was conducted using a wide range of classical and modern methods of microbiology, biochemistry, and physical chemistry. The ability of the ascomycete Fusarium oxysporum Schltdl. to modify films of chitosan with average-viscosity molecular weights of 200, 450, and 530 kDa was discovered. F. oxysporum was shown to use chitosan as the sole source of carbon/energy and actively overgrew films without deformations and signs of integrity loss. Scanning electron microscopy (SEM) recorded an increase in the porosity of film substrates. An analysis of the FTIR spectra revealed the occurrence of oxidation processes and crosslinking of macrochains without breaking β-(1,4)-glycosidic bonds. After F. oxysporum growth, the resistance of the films to mechanical dispersion and the degree of ordering of the polymer structure increased, while their solubility in the acetate buffer with pH 4.4 and sorption capacity for Fe2+ and Cu2+ decreased. Elemental analysis revealed a decrease in the nitrogen content in chitosan, which may indicate its inclusion into the fungal metabolism. The film transformation was accompanied by the production of extracellular hydrolase (different from chitosanase) and peroxidase, as well as biosurfactants. The results obtained indicate a specific mechanism of aminopolysaccharide transformation by F. oxysporum. Although the biochemical mechanisms of action remain to be analyzed in detail, the results obtained create new ways of using fungi and show the potential for the use of Fusarium and/or its extracellular enzymes for the formation of chitosan-containing materials with the required range of functional properties and qualities for biotechnological applications. Full article
(This article belongs to the Special Issue Innovative Applications and Biomanufacturing of Fungi)
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29 pages, 14906 KiB  
Article
Hydrothermal Engineering of Ferroelectric PZT Thin Films Tailoring Electrical and Ferroelectric Properties via TiO2 and SrTiO3 Interlayers for Advanced MEMS
by Chun-Lin Li and Guo-Hua Feng
Micromachines 2025, 16(8), 879; https://doi.org/10.3390/mi16080879 - 29 Jul 2025
Viewed by 180
Abstract
This work presents an innovative hydrothermal approach for fabricating flexible piezoelectric PZT thin films on 20 μm titanium foil substrates using TiO2 and SrTiO3 (STO) interlayers. Three heterostructures (Ti/PZT, Ti/TiO2/PZT, and Ti/TiO2/STO/PZT) were synthesized to enable low-temperature [...] Read more.
This work presents an innovative hydrothermal approach for fabricating flexible piezoelectric PZT thin films on 20 μm titanium foil substrates using TiO2 and SrTiO3 (STO) interlayers. Three heterostructures (Ti/PZT, Ti/TiO2/PZT, and Ti/TiO2/STO/PZT) were synthesized to enable low-temperature growth and improve ferroelectric performance for advanced flexible MEMS. Characterizations including XRD, PFM, and P–E loop analysis evaluated crystallinity, piezoelectric coefficient d33, and polarization behavior. The results demonstrate that the multilayered Ti/TiO2/STO/PZT structure significantly enhances performance. XRD confirmed the STO buffer layer effectively reduces lattice mismatch with PZT to ~0.76%, promoting stable morphotropic phase boundary (MPB) composition formation. This optimized film exhibited superior piezoelectric and ferroelectric properties, with a high d33 of 113.42 pm/V, representing an ~8.65% increase over unbuffered Ti/PZT samples, and displayed more uniform domain behavior in PFM imaging. Impedance spectroscopy showed the lowest minimum impedance of 8.96 Ω at 10.19 MHz, indicating strong electromechanical coupling. Furthermore, I–V measurements demonstrated significantly suppressed leakage currents in the STO-buffered samples, with current levels ranging from 10−12 A to 10−9 A over ±3 V. This structure also showed excellent fatigue endurance through one million electrical cycles, confirming its mechanical and electrical stability. These findings highlight the potential of this hydrothermally engineered flexible heterostructure for high-performance actuators and sensors in advanced MEMS applications. Full article
(This article belongs to the Special Issue Manufacturing and Application of Advanced Thin-Film-Based Device)
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15 pages, 2504 KiB  
Article
The Effect of the Interaction of Intense Low-Energy Radiation with a Zinc-Oxide-Based Material
by Ihor Virt, Piotr Potera, Nazar Barchuk and Mykola Chekailo
Crystals 2025, 15(8), 685; https://doi.org/10.3390/cryst15080685 - 28 Jul 2025
Viewed by 146
Abstract
Laser annealing of oxide functional thin films makes them compatible with substrates of various types, especially flexible materials. The effects of optical annealing on Ni-doped ZnO thin films were the subject of investigation and analysis in this study. Using pulsed laser deposition, we [...] Read more.
Laser annealing of oxide functional thin films makes them compatible with substrates of various types, especially flexible materials. The effects of optical annealing on Ni-doped ZnO thin films were the subject of investigation and analysis in this study. Using pulsed laser deposition, we deposited polycrystalline ZnNiO films on sapphire and silicon substrates. The deposited film was annealed by laser heating. A continuous CO2 laser was used for this purpose. The uniformly distributed long-wavelength radiation of the CO2 laser can penetrate deeper from the surface of the thin film compared to short-wavelength lasers such as UV and IR lasers. After growth, optical post-annealing processes were applied to improve the conductive properties of the films. The crystallinity and surface morphology of the grown films and annealed films were analyzed using SEM, and their electrical parameters were evaluated using van der Pauw effect measurements. We used electrical conductivity measurements and investigated the photovoltaic properties of the ZnNiO film. After CO2 laser annealing, changes in both the crystalline structure and surface appearance of ZnO were evident. Subsequent to laser annealing, the crystallinity of ZnO showed both change and degradation. High-power CO2 laser annealing changed the structure to a mixed grain size. Surface nanostructuring occurred. This was confirmed by SEM morphological studies. After irradiation, the electrical conductivity of the films increased from 0.06 Sm/cm to 0.31 Sm/cm. The lifetime of non-equilibrium charge carriers decreased from 2.0·10−9 s to 1.2·10−9 s. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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50 pages, 4603 KiB  
Review
Polymeric Composite Thin Films Deposited by Laser Techniques for Antimicrobial Applications—A Short Overview
by Anita Ioana Visan and Irina Negut
Polymers 2025, 17(15), 2020; https://doi.org/10.3390/polym17152020 - 24 Jul 2025
Viewed by 379
Abstract
Polymeric composite thin films have emerged as promising antimicrobial materials, particularly in response to rising antibiotic resistance. This review highlights the development and application of such films produced by laser-based deposition techniques, notably pulsed laser deposition and matrix-assisted pulsed laser evaporation. These methods [...] Read more.
Polymeric composite thin films have emerged as promising antimicrobial materials, particularly in response to rising antibiotic resistance. This review highlights the development and application of such films produced by laser-based deposition techniques, notably pulsed laser deposition and matrix-assisted pulsed laser evaporation. These methods offer precise control over film composition, structure, and thickness, making them ideal for embedding antimicrobial agents such as metal nanoparticles, antibiotics, and natural compounds into polymeric matrices. The resulting composite coatings exhibit enhanced antimicrobial properties against a wide range of pathogens, including antibiotic-resistant strains, by leveraging mechanisms such as ion release, reactive oxygen species generation, and membrane disruption. The review also discusses critical parameters influencing antimicrobial efficacy, including film morphology, composition, and substrate interactions. Applications include biomedical devices, implants, wound dressings, and surfaces in the healthcare and food industries. Full article
(This article belongs to the Special Issue Polymer Thin Films and Their Applications)
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15 pages, 2557 KiB  
Article
Multiline Laser Interferometry for Non-Contact Dynamic Morphing of Hierarchical Surfaces
by Biagio Audia, Caterina Maria Tone, Pasquale Pagliusi, Alfredo Mazzulla, George Papavieros, Vassilios Constantoudis and Gabriella Cipparrone
Biomimetics 2025, 10(8), 486; https://doi.org/10.3390/biomimetics10080486 - 23 Jul 2025
Viewed by 334
Abstract
Hierarchical surface structuring is a critical aspect of advanced materials design, impacting fields ranging from optics to biomimetics. Among several laser-based methods for complex structuring of photo-responsive surfaces, the broadband vectorial interferometry proposed here offers unique performances. Such a method leverages a polychromatic [...] Read more.
Hierarchical surface structuring is a critical aspect of advanced materials design, impacting fields ranging from optics to biomimetics. Among several laser-based methods for complex structuring of photo-responsive surfaces, the broadband vectorial interferometry proposed here offers unique performances. Such a method leverages a polychromatic laser source, an unconventional choice for holographic encoding, to achieve deterministic multiscale surface structuring through interference light patterning. Azopolymer films are used as photosensitive substrates. By exploring the interaction between optomechanical stress modulations at different spatial periodicities induced within the polymer bulk, we demonstrate the emergence of hierarchical Fourier surfaces composed of multiple deterministic levels. These structures range from sub-micrometer to tens of micrometers scale, exhibiting a high degree of control over their morphology. The experimental findings reveal that the optical encoding scheme significantly influences the resulting topographies. The polarization light patterns lead to more regular and symmetric hierarchical structures compared to those obtained with intensity patterns, underscoring the role of vectorial light properties in controlling surface morphologies. The proposed method is fully scalable, compatible with more complex recording schemes (including multi-beam interference), and it is applicable to a wide range of advanced technological fields. These include optics and photonics (diffractive elements, polarimetric devices), biomimetic surfaces, topographical design, information encoding, and anti-counterfeiting, offering a rapid, reliable, and versatile strategy for high-precision surface structuring at a submicrometric scale. Full article
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10 pages, 3121 KiB  
Article
Influence of Niobium Substitution on the Properties of Pb2Fe2O5 Thin Films Synthesized via Reactive Magnetron Sputtering
by Benas Beklešovas, Vytautas Stankus and Aleksandras Iljinas
Coatings 2025, 15(8), 863; https://doi.org/10.3390/coatings15080863 - 23 Jul 2025
Viewed by 218
Abstract
Lead ferrite (Pb2Fe2O5) is a promising multiferroic material that exhibits both ferroelectric and magnetic properties at room temperature. This study investigates how substituting niobium and adjusting the synthesis temperature affect the structural, morphological, and ferroelectric properties of [...] Read more.
Lead ferrite (Pb2Fe2O5) is a promising multiferroic material that exhibits both ferroelectric and magnetic properties at room temperature. This study investigates how substituting niobium and adjusting the synthesis temperature affect the structural, morphological, and ferroelectric properties of lead ferrite thin films deposited via reactive magnetron sputtering. Niobium-substituted PFO films (Pb2Fe2(1−x)Nb2xO5), where x corresponds to Nb2O5 contents of 3 wt.%, 5 wt.% and 10 wt.%, were prepared for this study, and denoted as PFONb3, PFONb5 and PFONb10, respectively. X-ray diffraction analysis confirmed the formation of Nb-substituted PFO phases, while polarization–electric field measurements demonstrated an increase in remnant polarization (Pr), with higher Nb content reaching a maximum Pr of 65 µC/cm2 at 10 wt.% Nb and a substrate temperature of 500 °C. Scanning electron microscopy and energy-dispersive spectroscopy revealed a uniform distribution of elements and a well-defined surface structure. These results highlight the need to fine tune synthesis parameters, such as temperature and substitution concentrations, to achieve optimal ferroelectric characteristics. Full article
(This article belongs to the Special Issue Advances in Novel Coatings)
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28 pages, 14374 KiB  
Article
Novel Airfoil-Shaped Radar-Absorbing Inlet Grilles on Aircraft Incorporating Metasurfaces: Multidisciplinary Design and Optimization Using EHVI–Bayesian Method
by Xufei Wang, Yongqiang Shi, Qingzhen Yang, Huimin Xiang and Saile Zhang
Sensors 2025, 25(14), 4525; https://doi.org/10.3390/s25144525 - 21 Jul 2025
Viewed by 326
Abstract
Aircraft, as electromagnetically complex targets, have radar cross-sections (RCSs) that are influenced by various factors, with the inlet duct being a critical component that often serves as a primary source of electromagnetic scattering, significantly impacting the scattering characteristics. In light of the conflict [...] Read more.
Aircraft, as electromagnetically complex targets, have radar cross-sections (RCSs) that are influenced by various factors, with the inlet duct being a critical component that often serves as a primary source of electromagnetic scattering, significantly impacting the scattering characteristics. In light of the conflict between aerodynamic performance and electromagnetic characteristics in the design of aircraft engine inlet grilles, this paper proposes a metasurface radar-absorbing inlet grille (RIG) solution based on a NACA symmetric airfoil. The RIG adopts a sandwich structure consisting of a polyethylene terephthalate (PET) dielectric substrate, a copper zigzag metal strip array, and an indium tin oxide (ITO) resistive film. By leveraging the principles of surface plasmon polaritons, electromagnetic wave absorption can be achieved. To enhance the design efficiency, a multi-objective Bayesian optimization framework driven by the expected hypervolume improvement (EHVI) is constructed. The results show that, compared with a conventional rectangular cross-section grille, an airfoil-shaped grille under the same constraints will reduce both aerodynamic losses and the absorption bandwidth. After 100-step EHVI–Bayesian optimization, the optimized balanced model attains a 57.79% reduction in aerodynamic loss relative to the rectangular-shaped grille, while its absorption bandwidth increases by 111.99%. The RCS exhibits a reduction of over 8.77 dBsm in the high-frequency band. These results confirm that the proposed optimization design process can effectively balance the conflict between aerodynamic performance and stealth performance for RIGs, reducing the signal strength of aircraft engine inlets. Full article
(This article belongs to the Section Electronic Sensors)
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25 pages, 3459 KiB  
Article
Phase Composition, Structure, and Microwave Absorption of Magnetron-Sputtered Co–C–Cr Multilayer Films
by Nadezhda Prokhorenkova, Almira Zhilkashinova, Madi Abilev, Leszek Łatka, Igor Ocheredko and Assel Zhilkashinova
Compounds 2025, 5(3), 27; https://doi.org/10.3390/compounds5030027 - 20 Jul 2025
Viewed by 217
Abstract
Multilayer thin films composed of cobalt (Co), carbon (C), and chromium (Cr) possess promising electromagnetic properties, yet the combined Co–C–Cr system remains underexplored, particularly regarding its performance as a microwave absorber. Existing research has primarily focused on binary Co–C or Co–Cr compositions, leaving [...] Read more.
Multilayer thin films composed of cobalt (Co), carbon (C), and chromium (Cr) possess promising electromagnetic properties, yet the combined Co–C–Cr system remains underexplored, particularly regarding its performance as a microwave absorber. Existing research has primarily focused on binary Co–C or Co–Cr compositions, leaving a critical knowledge gap in understanding how ternary multilayer architectures influence electromagnetic behavior. This study addresses this gap by investigating the structure, phase composition, and microwave absorption performance of Co–C–Cr multilayer coatings fabricated via magnetron sputtering onto porous silicon substrates. This study compares four-layer and eight-layer configurations to assess how multilayer architecture affects impedance matching, reflection coefficients, and absorption characteristics within the 8.2–12.4 GHz frequency range. Structural analyses using X-ray diffraction and transmission electron microscopy confirm the coexistence of amorphous and nanocrystalline phases, which enhance absorption through dielectric and magnetic loss mechanisms. Both experimental and simulated results show that increasing the number of layers improves impedance gradients and broadens the operational bandwidth. The eight-layer coatings demonstrate a more uniform absorption response, while four-layer structures exhibit sharper resonant minima. These findings advance the understanding of ternary multilayer systems and contribute to the development of frequency-selective surfaces and broadband microwave shielding materials. Full article
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15 pages, 3200 KiB  
Article
Stress Compensation in TiO2/SiO2 Optical Coatings by Manipulating the Thickness Modulation Ratio
by Bo Wang, Taiqi Wu, Weidong Gao, Gang Hu and Changjun Wang
Coatings 2025, 15(7), 848; https://doi.org/10.3390/coatings15070848 - 19 Jul 2025
Viewed by 313
Abstract
With the rapid advancement of high-precision optical systems, increasingly stringent demands are imposed on the surface figure accuracy of optical components. The magnitude of residual stress in multilayer films directly influences the post-coating surface figure stability of these components, making the control of [...] Read more.
With the rapid advancement of high-precision optical systems, increasingly stringent demands are imposed on the surface figure accuracy of optical components. The magnitude of residual stress in multilayer films directly influences the post-coating surface figure stability of these components, making the control of multilayer film stress a critical factor in enhancing optical surface figure accuracy. In this study, which addresses the process constraints and substrate damage risks associated with conventional annealing-based stress compensation for large-aperture optical components, we introduce an active stress engineering strategy rooted in in situ deposition process optimization. By systematically tailoring film deposition parameters and adjusting the thickness modulation ratio of TiO2 and SiO2, we achieve dynamic compensation of residual stress in multilayer structures. This approach demonstrates broad applicability across diverse optical coatings, where it effectively mitigates stress-induced surface distortions. Unlike annealing methods, this intrinsic stress polarity manipulation strategy obviates the need for high-temperature post-processing, eliminating risks of material decomposition or substrate degradation. By enabling precise nanoscale stress regulation in large-aperture films through controlled process parameters, it provides essential technical support for manufacturing ultra-precision optical devices, such as next-generation laser systems and space-based stress wave detection instruments, where minimal stress-induced deformation is paramount to functional performance. Full article
(This article belongs to the Section Thin Films)
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