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With the rapid development of the electronic information industry, issues of electromagnetic leakage and high-temperature infrared radiation have become increasingly prominent. Especially in the field of military protection, they can easily lead to information leakage and infrared exposure. Therefore, designing and manufacturing compatible low-reflectivity electromagnetic interference shielding/high-temperature infrared stealth materials is of significant importance in the military domain. However, how to synergistically design and manufacture compatible composites with low reflectivity electromagnetic interference shielding and infrared stealth performance has gradually become a major challenge in the metallized polymer nonwoven fabric system.
To address the aforementioned challenges, Professor Liu Tianxi and Associate Professor Wang Zicheng from Jiangnan University prepared hierarchical polyimide (PI) fiber composites through alkali treatment, in-situ growth of magnetic particles, and a “self-activating” chemical plating silver process. In particular, by systematically assembling Fe3O4/Ag loaded PI nonwoven fabric (PFA) and pure Ag coated PI nonwoven fabric (PA), layered impedance matching can be constructed, resulting in ultralow reflectivity electromagnetic interference shielding performance. Furthermore, the thermal insulation of the fluffy three-dimensional (3D) spatial structure of PFA and the low infrared emissivity from the silver plating of PA contribute to excellent infrared stealth performance. More importantly, the strong bonding interactions between Fe3O4, Ag, and PI fibers enhance the thermal stability and high-temperature infrared stealth performance of the electromagnetic interference shielding. This outstanding comprehensive performance provides broad application prospects for military tents in protecting internal equipment from electromagnetic interference from adjacent equipment and/or enemies, as well as suppressing external infrared detection.
The related research is titled “Hierarchical Polyimide Nonwoven Fabric with Ultralow-Reflectivity Electromagnetic Interference Shielding and High-Temperature Resistant Infrared Stealth Performance” and was published in the journal Nano-Micro Letters.
In this study, PI nanofiber materials were first prepared using an electrospinning device (Yongkang Leye ET series). Then, through alkali treatment, in-situ growth of magnetic particles, and a “self-activating” chemical plating silver process, hierarchical PI fiber composites with ultralow reflectivity electromagnetic interference shielding and high-temperature infrared stealth performance were successfully obtained.
The developed hierarchical polyimide fiber composites have ultralow reflectivity and electromagnetic interference (EMI) shielding capabilities, with various potential applications in military environments. For instance, the low reflectivity and high electromagnetic wave absorption capacity of this material make it suitable for stealth technology. The EMI shielding performance can protect sensitive electronic devices and communication systems from electromagnetic interference. Additionally, it can also be used in soldiers’ protective clothing. The material can be designed with specific optical properties to achieve camouflage effects, helping personnel and equipment blend into the surrounding environment.
Scheme 1 Schematic diagram of the preparation process of PFA/PA nonwoven fabric.
Figure 2 XRD spectra of PI, PA1.5, PFA0, and PFA1. b Hysteresis loop of PFA0, PFA1, and PFA2. c Conductivity and density of PA1, PA1.5, and PA2. d XPS spectra of PA1.5, PFA0, PFA1, and PFA2. e High-resolution XPS spectra of Fe 2p for PFA0 and f Ag 3d for PFA1. g Optical photos of 4*PFA1, h PA1.5, and i, j 4*PFA1/PA1.5.
Figure 3 a SET, b EMI SE, c A, d R, e Power coefficient, f Reflectivity map of N*PFA1/PA1.5, g EMI SE, h A, i Reflectivity map of 4 * PFAx / PA1.5.
Figure 4. Electromagnetic shielding performance of 4*PFA1/PA1.5 and PA1.5/4*PFA1 under different incident directions (a) and their corresponding (b, c) power coefficient maps; (d) Demonstration of electromagnetic shielding performance: between the transmitter and receiver (e) with no sample, (f) PA1.5/4*PFA1, (g) 4*PFA1/PA1.5 when inserted into the electromagnetic shielding system.
Figure 5. (a) Infrared emissivity curve of PAx; (b) Infrared imaging of 4*PFA1/PA1.5 on a thermal stage at 150, 200, and 250 โ; (c) Surface actual temperature and infrared radiation temperature curve of 4*PFA1/PA1.5 on a thermal stage at 150 โ; (d) Schematic diagram of a simulated desert environment; (e) Infrared imaging of 4*PFA1/PA1.5 at different heat source temperatures; (f) Infrared imaging of 4*PFA1/PA1.5 on the palm under day and night conditions.
Figure 6. (a) Electromagnetic shielding performance of 4*PFA1/PA1.5 at 8.2 – 40 GHz, (b) Power coefficient, (c) Reflectivity; (d) Schematic diagram of the low reflectivity electromagnetic shielding mechanism of 4*PFA1/PA1.5; (e – h) Demonstration of electromagnetic shielding and infrared stealth compatibility performance of 4*PFA1/PA1.5.
Figure 7. Schematic diagram of possible application scenarios for compatible low-reflectivity electromagnetic shielding and infrared stealth performance of 4*PFA1/PA1.5.
Original link:
https://doi.org/10.1007/s40820-024-01590-3
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