Functional Magnetic and Dielectric Composites: Fabrication, Properties and Applications

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Surface Engineering for Energy Harvesting, Conversion, and Storage".

Deadline for manuscript submissions: 21 May 2024 | Viewed by 11611

Special Issue Editors


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Guest Editor
School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 610054, China
Interests: magnetic materials; magnetic thin films; ferrites; hexagonal ferrites

E-Mail Website
Guest Editor
College of Optoelectronic Engineering, Chengdu University of Information Technology, Chengdu 610025, China
Interests: magnetic materials; dielectric materials; magnetic thin films; ferrites
School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 610054, China
Interests: magnetic materials; microwave materials; magnetodielectric materials; ferrites

Special Issue Information

Dear Colleagues,

For many years, functional magnetic and dielectric composites have been attractive to both academia and industry in various applications, such as electric energy convention, wireless communication, sensors, biomedical treatment, etc. Modern challenges in the characteristics of these applications, including high power, lightweight, durability, and resource-friendliness, place more stringent demands for the research on functional magnetic and dielectric composites. To solve these challenges, it is crucial to understand the interaction mechanisms of multiphase magnetic and dielectric composite systems. Advanced fabrication techniques are also important for the effective assembly of magnetic and dielectric composites with complex microstructures. More importantly, the properties of magnetic and dielectric composites can be tailored by modifying the multiphase interaction or preparation methods. Driven by the extreme application environment, high-performance magnetic and dielectric composites which can withstand high power, high temperatures, high stress have seen a huge demand in experimental, theoretical and modeling activities.

This Special Issue of Coatings aims to provide a collection of papers focusing on the fabrication, properties, and applications of functional magnetic and dielectric composites. Original research articles and reviews are welcome in this Special Issue. Research topics welcome in this Special Issue may include (but are not limited to) the following:

  • Theoretical and experimental research on the interaction mechanisms of multiphase magnetic and dielectric composite systems;
  • Recent developments in preparation methods of functional magnetic and dielectric composites;
  • Advanced preparation techniques for high-performance magnetic and dielectric nanocomposites;.
  • Theoretical and experimental research on complex microstructures of composites;
  • Recent developments in characterization, test, and measurement methods for mechanical, chemical, and electrochemical properties and performances;
  • Recent developments in novel application areas of functional magnetic and dielectric composites;
  • Modeling, simulation, and calculation of the properties, performance, durability, and reliability of the composites in various applications.
  • High-performance magnetic and dielectric composites for high power, high temperatures, high stress, and other extreme environment applications.

We look forward to receiving your contributions.

Dr. Chuanjian Wu
Prof. Dr. Lezhong Li 
Dr. Qifan Li
Guest Editors

Manuscript Submission Information

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Keywords

  • magnetic and dielectric composites
  • nanocomposites
  • preparation methods
  • complex microstructure
  • advanced characterization

Published Papers (10 papers)

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Research

10 pages, 3473 KiB  
Article
Contribution of Magnetization Mechanisms in MnZn Ferrites with Different Grain Sizes and Sintering Densification
by Hai Liu, Jihong Liao, Chonghua Li and Gang Huang
Coatings 2024, 14(3), 302; https://doi.org/10.3390/coatings14030302 - 29 Feb 2024
Viewed by 685
Abstract
This study investigates the magnetization mechanisms in MnZn ferrites, which are key materials in high-frequency power electronics, to understand their behavior under various sintering conditions. Employing X-ray diffraction and scanning electron microscopy, we analyzed the microstructure and phase purity of ferrites sintered at [...] Read more.
This study investigates the magnetization mechanisms in MnZn ferrites, which are key materials in high-frequency power electronics, to understand their behavior under various sintering conditions. Employing X-ray diffraction and scanning electron microscopy, we analyzed the microstructure and phase purity of ferrites sintered at different temperatures. Our findings confirm consistent spinel structures and highlight significant grain-growth and densification variabilities. Magnetic properties, particularly the saturation magnetization (Ms) and initial permeability (μi), were explored, revealing their direct correlation with the sintering process. The decomposition of magnetic spectra into domain-wall-motion and spin-rotation components offered insights into the dominant magnetization mechanisms, with the domain wall movement becoming increasingly significant at higher sintering temperatures. The samples sintered at 1310 °C showcased superior permeability and the least loss in our investigations. This research underscores the impact of sintering conditions on the magnetic behavior of MnZn ferrites, providing valuable guidelines for optimizing their magnetic performance in advanced electronic applications and contributing to the material science field’s understanding of the interplay between sintering, microstructures, and magnetic properties. Full article
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12 pages, 5242 KiB  
Article
Wide-Spectrum Antireflective Properties of Germanium by Femtosecond Laser Raster-Type In Situ Repetitive Direct Writing Technique
by Kaixuan Wang, Yubin Zhang, Jun Chen, Qingzhi Li, Feng Tang, Xin Ye and Wanguo Zheng
Coatings 2024, 14(3), 262; https://doi.org/10.3390/coatings14030262 - 22 Feb 2024
Viewed by 674
Abstract
A femtosecond laser raster-type in situ repetitive direct writing technique was used for the fabrication of anti-reflective microhole structures in Germanium (Ge) in the visible near-infrared range (300–1800 nm). This technique builds a layer of microstructured arrays on the surface of Ge, enabling [...] Read more.
A femtosecond laser raster-type in situ repetitive direct writing technique was used for the fabrication of anti-reflective microhole structures in Germanium (Ge) in the visible near-infrared range (300–1800 nm). This technique builds a layer of microstructured arrays on the surface of Ge, enabling Ge to exhibit excellent anti-reflective properties. The large-area micro-nanostructures of Ge were fabricated using femtosecond laser raster-type in situ repetitive direct writing. Ge microstructures are characterized by their structural regularity, high processing efficiency, high reproducibility, and excellent anti-reflective properties. Experimental test results showed that the average reflectance of the Ge microporous structure surface in the range of 300–1800 nm was 2.25% (the average reflectance of flat Ge was 41.5%), and the lowest reflectance was ~1.6%. This microstructure fabrication drastically reduced the optical loss of Ge, thus enhancing the photothermal utilization of Ge. The many nanoburrs and voids in the Ge microporous structure provided excellent hydrophobicity, with a hydrophobicity angle of up to 133 ± 2° (the hydrophobicity angle of flat Ge was 70 ± 2°). The high hydrophobicity angle allows for strong and effective self-cleaning performance. The femtosecond laser raster-type in situ repeatable direct writing technology has many desirable properties, including simplicity, high accuracy, flexibility, and repeatability, that make it one of the preferred choices for advanced manufacturing. The Ge micro-nanostructured arrays with excellent optical anti-reflective properties and hydrophobicity have become an attractive alternative to the current photo-thermal absorbers. It is expected to be used in many applications such as solar panels, photovoltaic sensors, and other optoelectronic devices. Full article
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11 pages, 12013 KiB  
Communication
Interface Modulation of CoNi Alloy Decorated with Few-Layer Reduced Graphene Oxide for High-Efficiency Microwave Absorption
by Hai Xie, Jinmei Li, Yaoming Zhang, Juan Yang, Tingmei Wang and Qihua Wang
Coatings 2024, 14(2), 228; https://doi.org/10.3390/coatings14020228 - 15 Feb 2024
Viewed by 811
Abstract
Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) [...] Read more.
Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) in the precursors, the resulting CoNi/rGO-2 composite demonstrates optimal microwave absorption performance with a minimum reflection loss (RLmin) of −66.2 dB at 7.6 GHz in the C band. Moreover, the CoNi/rGO-2 with 50 wt% filler loading achieves a maximum effective absorption bandwidth (EAB) of 6.8 GHz (10.6–17.4 GHz) at a thickness of 2.5 mm, almost spanning the entire Ku band and a portion of the X band. The outstanding performance of CoNi/rGO-2 is ascribed to the high magnetic loss from the CoNi alloy and the incorporation of rGO, which induces interfacial polarization to enhance the dielectric loss and improve the impedance matching of composite. These favorable findings highlight the considerable potential and superiority of the CoNi/rGO-2 composite as an electromagnetic wave absorption material. This work sets forth a viable strategy for designing high-efficiency alloy/rGO absorbers. Full article
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10 pages, 5043 KiB  
Article
Effect of Oxidant Concentration on Properties of Ferrite Films by Spin-Spray Deposition
by Hai Liu, Jihong Liao, Gang Huang, Xiaona Jiang, Zhong Yu, Zhongwen Lan and Ke Sun
Coatings 2024, 14(1), 120; https://doi.org/10.3390/coatings14010120 - 16 Jan 2024
Viewed by 647
Abstract
In response to the demands for high frequency, miniaturization, and high integration in electronic devices, such as inductors and DC-DC convertors, nickel–zinc ferrite thin films exhibit significant application value and development potential. For regulating the magnetic properties and microstructure of spin-sprayed polycrystalline ferrite [...] Read more.
In response to the demands for high frequency, miniaturization, and high integration in electronic devices, such as inductors and DC-DC convertors, nickel–zinc ferrite thin films exhibit significant application value and development potential. For regulating the magnetic properties and microstructure of spin-sprayed polycrystalline ferrite materials, a comprehensive understanding of the impact of oxidant concentration on film reaction is essential. This study finds that as the concentration of the NaNO2 oxidant increases, the grain size of the nickel–zinc ferrite thin film samples progressively enlarges. Due to the preferential occupation of iron ions at the B sites, the saturation magnetization correspondingly increases. However, when the oxidant concentration becomes excessive, the preferential (222) orientation growth of the film is disrupted, leading to the agglomeration and uneven growth of grains, transitioning from triangular plate-like to spherical in shape. This increase in grain size alters the magnetization mechanism of the thin film, predominantly favoring domain wall movement. Upon analyzing the microstructure and magnetic characteristics, it becomes evident that the concentration of oxidant is a key determinant in the spin-spray deposition process. Full article
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8 pages, 2978 KiB  
Communication
Effect of Film Thickness on Microstructural and Magnetic Properties of Lithium Ferrite Films Prepared on Strontium Titanate (001) Substrates
by Kun Liu, Ruyi Zhang, Lu Lu, Jiankang Li and Songyou Zhang
Coatings 2023, 13(12), 2097; https://doi.org/10.3390/coatings13122097 - 17 Dec 2023
Viewed by 776
Abstract
Epitaxial lithium ferrite (LiFe5O8) films with different thicknesses were successfully fabricated on strontium titanate (SrTiO3) (001) substrates using the magnetron sputtering deposition technique. The microstructural and magnetic properties of the films were characterized by an advanced transmission [...] Read more.
Epitaxial lithium ferrite (LiFe5O8) films with different thicknesses were successfully fabricated on strontium titanate (SrTiO3) (001) substrates using the magnetron sputtering deposition technique. The microstructural and magnetic properties of the films were characterized by an advanced transmission electron microscope and a magnetic measurement device. It was found that the formation of structural defects can be influenced by the thickness of the film. In addition to misfit dislocations, orientation domains form in thinner films and twin boundaries appear in thicker films, respectively, contributing to the misfit strain relaxation in the heterosystem. The magnetic measurement showed that the thinner films have enhanced magnetization and a relatively lower coercive field compared with the thicker films containing antiferromagnetic twin boundaries. Our results provide a way of tuning the microstructure and magnetic properties of lithium ferrite films by changing the film thickness. Full article
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15 pages, 4575 KiB  
Article
Influences of Magnetization Direction on the Flux Leakage Field of Weld Defects
by Yunfei Ye, Kailun Ji and Ping Wang
Coatings 2023, 13(6), 1005; https://doi.org/10.3390/coatings13061005 - 29 May 2023
Cited by 1 | Viewed by 1021
Abstract
The magnetic flux leakage (MFL) detection technique is applied to the detection of weld defects, such as cracks and pores. As the weld has a distinct structure, there are differences in the magnetization path and leakage field intensity under different magnetization directions. According [...] Read more.
The magnetic flux leakage (MFL) detection technique is applied to the detection of weld defects, such as cracks and pores. As the weld has a distinct structure, there are differences in the magnetization path and leakage field intensity under different magnetization directions. According to surveys, a suitable magnetization direction can significantly enhance detection rates of small-sized defects by stimulating a stronger field signal of the defect leakage. In this study, ANSYS finite element simulation software is used to calculate the weld defect leakage field based on the quantitative analysis. Specifically, the leakage field component strengths of circular hole defects and longitudinal rectangular groove defects are compared when the magnetization direction is perpendicular or parallel to the weld. Furthermore, the characteristic rules of the defect leakage field and its components under any magnetization direction are discussed, and a weld MFL detection platform is set up for validation. According to the experimental results, the amplitude of the magnetic leakage signal during vertical magnetization of circular hole defects is only 18.6% of that during parallel magnetization. Similarly, the amplitude of the magnetic leakage signal during parallel magnetization of longitudinal crack-type defects is only 9.2%~29.3% of that during vertical magnetization. Full article
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11 pages, 5502 KiB  
Article
Effects of Substrates on Thin-Film Growth of Nickel Zinc Ferrite by Spin-Spray Deposition
by Hai Liu, Zhong Yu, Xinglian Song, Maojun Ran, Xiaona Jiang, Zhongwen Lan and Ke Sun
Coatings 2023, 13(4), 690; https://doi.org/10.3390/coatings13040690 - 28 Mar 2023
Cited by 1 | Viewed by 1045
Abstract
In certain applications, such as on-chip integrated inductors, ferrite materials are highly desirable owing to their superior magnetic and insulation properties. Spin-spray deposition is a promising method for producing high-quality thin films of ferrite, as it does not require a vacuum and can [...] Read more.
In certain applications, such as on-chip integrated inductors, ferrite materials are highly desirable owing to their superior magnetic and insulation properties. Spin-spray deposition is a promising method for producing high-quality thin films of ferrite, as it does not require a vacuum and can operate at low temperatures. A comprehensive analysis was conducted to investigate the influence of the substrate on the microstructure and magnetic properties of the thin films, and the growth mechanism of this phenomenon was discussed. In addition, first-order reversal curve measurements were used to study the coercivity and grain size distribution. The results indicate that thermal conductivity played a significant role in determining the thin-film growth during spin spray deposition. Polyimide is considered a more suitable substrate under this process due to its appropriate thermal conductivity, which results in more uniform grain distribution and improved magnetic properties, with maximum permeability and a cutoff frequency reaching 55 and 485 MHz, respectively. Our results provide valuable insights into the mechanism of spin-spray deposition and offer an effective way to tune the performance of ferrite thin-film materials. Full article
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11 pages, 34937 KiB  
Article
Strain Modulation of Microstructure, Magnetic Domains, and Magnetic Properties of Ti/Fe/Ni81Fe19/Fe/Ti Multilayer Thin Films
by Zongsheng He, Zenan Ma, Ziyu Li, Yangzhong Du, Jun Yang, Chuanjian Wu, Qifan Li, Xiaona Jiang, Chaoming Wang, Zhong Yu, Zhongwen Lan and Ke Sun
Coatings 2023, 13(2), 363; https://doi.org/10.3390/coatings13020363 - 05 Feb 2023
Viewed by 1225
Abstract
A simple and convenient method is demonstrated in this work by continuously applying uniaxial tensile strains to tune the high-frequency properties of flexible magnetic films. The magnetostriction effect causes the uniaxial magnetic anisotropy in the Ti/Fe/Ni81Fe19/Fe/Ti multilayer film when [...] Read more.
A simple and convenient method is demonstrated in this work by continuously applying uniaxial tensile strains to tune the high-frequency properties of flexible magnetic films. The magnetostriction effect causes the uniaxial magnetic anisotropy in the Ti/Fe/Ni81Fe19/Fe/Ti multilayer film when the flexible substrate transitions from the convex state to the planar state after preparation. In addition, the microstructure, magnetic domain morphology, and the high-frequency magnetic performance of the pre-strained Ti/Fe/Ni81Fe19/Fe/Ti multilayer films are investigated. The results show that the flexible Ti/Fe/Ni81Fe19/Fe/Ti multilayer films’ initial permeability can be monotonically varied over a hundred units, and the resonant frequency can be adjusted around 1.5 GHz. The flexible Ti/Fe/Ni81Fe19/Fe/Ti films, with their elastic-tunable magnetic performance, are promising candidate materials for flexible microwave devices. Full article
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11 pages, 4109 KiB  
Article
A Four-Band Terahertz Metamaterial Sensor Based on Symmetric E-Shaped Structure
by Li Li, Hongyi Ge, Yuying Jiang, Guangming Li, Fei Wang, Ming Lv, Xiaodi Ji, Zhiyuan Jia, Zhi Li and Yuan Zhang
Coatings 2022, 12(11), 1694; https://doi.org/10.3390/coatings12111694 - 07 Nov 2022
Cited by 1 | Viewed by 1607
Abstract
To realize the multi-frequency selectivity of the analyte, a novel four-band terahertz metamaterial sensor is proposed in this work. In particular, the sensor performance is analyzed theoretically and numerically within a terahertz frequency range (0.8–1.5 THz) via the finite element method. According to [...] Read more.
To realize the multi-frequency selectivity of the analyte, a novel four-band terahertz metamaterial sensor is proposed in this work. In particular, the sensor performance is analyzed theoretically and numerically within a terahertz frequency range (0.8–1.5 THz) via the finite element method. According to the results, higher-order Fano resonance is the main cause of the four narrow and sharp transmission valleys in the operating band region of the sensor, yielding high resolution with Q values up to 177. Moreover, this sensor is polarization-insensitive over a wide polarization angle range of 0° to 50°. In addition, the sensor achieves refractive index sensitivity of 200 GHz/RIU and offers FOM values of up to 26.7. The sensor proposed in this study exhibits a simple structure, frequency selection characteristics, low cost, and enhances the interaction between terahertz waves and substances, which is of great theoretical and practical significance for the development of terahertz functional devices such as sensors and filters. Full article
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12 pages, 4694 KiB  
Article
Design and Fabrication of Temperature-Compensated Film Bulk Acoustic Resonator Filter Based on the Stress Compensation Effect
by Ya Liu, Ke Sun, Jinyi Ma, Zhong Yu and Zhongwen Lan
Coatings 2022, 12(8), 1126; https://doi.org/10.3390/coatings12081126 - 05 Aug 2022
Cited by 4 | Viewed by 2154
Abstract
To ensure that the performance of filters matches the continuous development in communication frequency bands, the influence of temperature on filter performance must be considered during the fabrication of filters. In this study, a cavity-type temperature-compensated film bulk acoustic resonator (TC-FBAR) device was [...] Read more.
To ensure that the performance of filters matches the continuous development in communication frequency bands, the influence of temperature on filter performance must be considered during the fabrication of filters. In this study, a cavity-type temperature-compensated film bulk acoustic resonator (TC-FBAR) device was prepared with an SiO2 temperature filter between the bottom electrode and the piezoelectric layer. A one-dimensional Mason model of the TC-FBAR was established. An advanced design system, a high-frequency structure simulator, and COMSOL software were used to optimize the design of the TC-FBAR. After the optimization, the out-of-band rejection was improved by 10 dB. To address the compensation effect of the tensile and compressive stresses, a multilayer film was implemented for low-stress control and a reduction in stress to |P| ≤ 150 MPa, thereby improving the orientation of the piezoelectric film. Moreover, the influence of the thickness of the SiO2 temperature-compensated layers on the temperature-compensated characteristics was studied. When the SiO2 thickness was 50 nm, the temperature coefficient of frequency (TCF) was ±1 ppm/°C. The center frequency and 3 dB bandwidth of TC-FBAR were 2.492 GHz and 15.02 MHz, respectively, and the center insertion loss was −3.1 dB. Moreover, the out-of-band rejection was greater than 40 dBc, and TCF was 0.8 ppm/°C. Full article
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