Ordered Solid Solution γ′-Fe4N-Based Absorber Synthesized by Nitridation Engineering and Applied for Electromagnetic Functional Devices

Electrical Engineering Materials Science Engineering Metallic Materials
Electromagnetic wave absorption Nitridation engineering Ordered solid solution Energy conversion and storage device Electromagnetic stealth antenna

Academic Background

With the advancement of industrial upgrading and disciplinary integration, significant progress has been made in the informatization, intelligence, and automation of human society. However, this has also raised higher demands for new materials, especially in the field of electromagnetic functional materials. The increasingly severe problem of electromagnetic pollution has made the development of magnetic nanomaterials with stable characteristics and wide-band operation an urgent need. As an ordered solid solution, γ′-Fe4N exhibits enormous potential in improving electromagnetic wave absorption performance due to its stable chemical properties, high conductivity, and saturation magnetization. However, its harsh preparation conditions have long been overlooked. This study successfully prepared Fe4N nanospheres embedded in nitrogen-doped carbon fibers (Fe4N@NCFs) through nitridation engineering and electrospinning technology, aiming to achieve high-efficiency, broad-bandwidth, and thin-thickness microwave absorption, while exploring its application potential in electromagnetic functional devices.

Source of the Paper

This paper was co-authored by Xiangwei Meng, Jia Li, Shuting Zhang, Di Lan, Meijie Yu, Teng Long, and Chengguo Wang, from the School of Material Science and Engineering, Shandong University, the School of Mechanical, Electrical and Information Engineering, Shandong University, and the School of Materials Science and Engineering, Hubei University of Automotive Technology. The paper was accepted by the journal Advanced Fiber Materials on November 12, 2024, and submitted on July 31, 2024.

Research Process

1. Material Preparation and Characterization

The study first prepared Fe4N nanospheres embedded in nitrogen-doped carbon fibers (Fe4N@NCFs) through hydrothermal reaction, electrospinning, carbonization, and nitridation treatment. The specific steps are as follows:

  1. Hydrothermal Reaction: Fe3O4 nanospheres were prepared, with a rough surface composed of numerous small nanoparticles.
  2. Electrospinning: Fe3O4 nanospheres were successfully extruded and confined in fiber bundles using the pulling force of the electric field and friction with polyvinylpyrrolidone (PVP).
  3. Carbonization: PVP was pyrolyzed into carbon fibers, and Fe3O4 was converted into Fe4N crystals under high temperature.
  4. Nitridation Treatment: A strictly controlled nitridation process was carried out in an ammonia atmosphere to ensure the purity of Fe4N crystals.

The material was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM), confirming the successful preparation of Fe4N crystals and their uniform dispersion in the fibers.

2. Electromagnetic Wave Absorption Performance Testing

The electromagnetic wave absorption performance of Fe4N@NCFs was tested, showing a minimum reflection loss (RL) of -77.7 dB at 2.0 mm thickness and a maximum effective absorption bandwidth (EAB) of 5.8 GHz at 1.8 mm thickness. Additionally, the effective absorption frequency range of Fe4N@NCFs within 1-5 mm thickness spanned 3.8-18.0 GHz, covering the S, C, X, and Ku bands, demonstrating its potential to meet diverse demand scenarios.

3. Analysis of Electromagnetic Wave Absorption Mechanisms

The study deeply explored the electromagnetic wave absorption mechanisms of Fe4N@NCFs through density functional theory (DFT) calculations and electromagnetic parameter analysis. The results showed that the conductivity of Fe4N is similar to that of a conductor, with a zero bandgap, indicating excellent conductive loss capability. Moreover, the fibrous microstructure of Fe4N@NCFs increased multiple reflections and local micro-current formation of electromagnetic waves, enhancing interfacial polarization and charge migration.

4. Functional Device Design

The study further designed a waste energy secondary utilization device and an electromagnetic stealth antenna based on Fe4N@NCFs, verifying its broad application potential in multifunctional devices. The waste energy secondary utilization device converts absorbed electromagnetic waves into heat energy, which is then converted into electrical energy based on the Seebeck effect, achieving the clean utilization of environmentally harmful electromagnetic energy. The electromagnetic stealth antenna efficiently receives signals in a wide frequency band, showing its application prospects in communication and navigation fields.

Research Results

  1. Material Characterization: XRD and XPS results indicated the successful preparation of Fe4N crystals and their uniform dispersion in nitrogen-doped carbon fibers. HR-TEM images showed that Fe4N nanospheres were enveloped by carbon shells with a thickness of 10-20 nm, forming heterogeneous interfaces that enhanced interfacial polarization.
  2. Electromagnetic Wave Absorption Performance: Fe4N@NCFs exhibited a minimum reflection loss of -77.7 dB at 2.0 mm thickness and a maximum effective absorption bandwidth of 5.8 GHz at 1.8 mm thickness, demonstrating excellent electromagnetic wave absorption performance.
  3. Electromagnetic Wave Absorption Mechanisms: DFT calculations and electromagnetic parameter analysis revealed that the conductivity of Fe4N is similar to that of a conductor, with a zero bandgap, indicating excellent conductive loss capability. The fibrous microstructure increased multiple reflections and local micro-current formation of electromagnetic waves, enhancing interfacial polarization and charge migration.
  4. Functional Device Design: The waste energy secondary utilization device and electromagnetic stealth antenna based on Fe4N@NCFs showed broad application potential, verifying the design feasibility of multifunctional devices.

Conclusion

This study successfully prepared Fe4N nanospheres embedded in nitrogen-doped carbon fibers through nitridation engineering, achieving excellent electromagnetic wave absorption performance and impedance matching properties. Fe4N@NCFs exhibited a minimum reflection loss of -77.7 dB and a maximum effective absorption bandwidth of 5.8 GHz, demonstrating broad application potential in electromagnetic stealth and waste energy recovery fields. The study revealed the electromagnetic wave absorption mechanisms of the ordered solid solution Fe4N, providing theoretical guidance for the development and application of functional materials in the future.

Research Highlights

  1. High-Efficiency Electromagnetic Wave Absorption: Fe4N@NCFs exhibited a minimum reflection loss of -77.7 dB at 2.0 mm thickness, demonstrating excellent electromagnetic wave absorption performance.
  2. Wide-Band Operation: Fe4N@NCFs achieved a maximum effective absorption bandwidth of 5.8 GHz at 1.8 mm thickness, covering the S, C, X, and Ku bands.
  3. Multifunctional Device Design: The waste energy secondary utilization device and electromagnetic stealth antenna based on Fe4N@NCFs showed broad application potential, verifying the design feasibility of multifunctional devices.

Other Valuable Information

This study was supported by the Key Research and Development Program of Shandong Province (2021ZLGX01, 2021CXGC010903) and the Natural Science Foundation of Shandong Province (ZR2022ME055). All data can be accessed from the corresponding author upon reasonable request.