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Abstract
In this paper, we propose a high-temperature resistant bilayer structure for electromagnetic protection with low reflection, consisting of a metasurface and an absorbing layer. The bottom metasurface decreases the reflected energy by using a phase cancellation mechanism to make electromagnetic wave scattering in the 8–12 GHz range. While the upper absorbing layer assimilates the incident electromagnetic energy through electrical losses and simultaneously regulates the reflection amplitude and phase of the metasurface to enhance scattering and expand its operating bandwidth. Research shows that the bilayer structure achieves a low reflection of -10 dB in the range of 6.7–11.4 GHz due to the combined effect of the above two physical mechanisms. In addition, long-term high-temperature and thermal cycling tests verified the stability of the structure in the temperature range of 25–300°C. This strategy provides the feasibility of electromagnetic protection in high-temperature conditions.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Since excessive electromagnetic (EM) radiation has been defined as novelty pollution, the corresponding EM protection materials have gradually become hot research. Microwave absorbing materials (MAMs) effectively achieve electromagnetic protection, which typically employs dielectrics or magnetic additives, such as carbon and iron powder, in the matrix material. Introducing electrical and dielectric [1–3] or magnetic losses [4–6] allows the incident electromagnetic energy to be dissipated and converted into other forms of energy such as thermal energy. The attenuation capability of MAM for EM wave is determined by its EM parameters: the relative permittivity ɛr and the relative permeability µr. These two determine the impedance matching and the absorption strength of the MAM and are influenced by the composition, microscopic properties, and filling rate of the EM additive, as well as the strength of the external EM field and the ambient temperature.
MAMs made from metallic micro-powders, ferrite, and other magnetic additives have poor high-temperature adaptation and short oxidation resistance. Its magnetic response gradually weakens with increasing temperature and demagnetizes when the Curie temperature is reached [7]. In the case of application to high-temperature components such as traveling wave tubes and high-power microwave heating devices [8–10], the stability of EM protection performance is affected. Correspondingly, the high-temperature resistant MAMs are predominantly of the electrical loss type. Carbon-based composites and ceramic-based materials with better thermochemical stability are the main high-temperature resistant electric loss additives at present [11–18]. Despite the progress in the study of high-temperature resistant MAMs, the existence of a series of problems has limited their development. Due to the lack of magnetism, the impedance of these materials is poorly matched for broadband absorption [15,16] and typically exhibits a larger thickness to obtain better absorption strength in a limited operating band [17,18]. Furthermore, based on the Debye theory [19], the relaxation polarization time of the electrically depleted additives shortens at high temperatures, the carrier concentration increases, and the relative permittivity ɛr produces significant changes. Consequently, the operating bandwidth and absorption strength of the electric loss type MAMs have large fluctuations with temperature changes and poor stability [20,21].
Metasurfaces have shown great potential in various applications such as stealth cloak [22], polarization conversion [23,24], and vortex beam generation [25,26] based on their ability to manipulate EM wave transmission. The phase gradient metasurface [27–32] introduces the concept of EM diffusion into EM protection applications by controlling the reflected energy to deviate from the protected target in the spatial domain. The metasurface consists of a permutation of subwavelength metal/dielectric periodic cells, and the EM properties depend mainly on the geometrical parameters and the arrangement of the periodic cells. Therefore, it is less affected by the EM parameters of the constituent materials and is more likely to ensure stable EM performance in high-temperature environments. Accordingly, in the latest work, metasurfaces have also been employed to construct EM protection materials at high temperatures [32–36]. Metallic Meta-Skin [33] that can resist 300°C is proposed, but the all-metal structure brought a tremendous weight and large thickness of 9 mm. An all-ceramic coding metasurface [36] can endure ultra-high temperatures of 1000°C, however, the special meta-atomic design required elevated preparation accuracy, while the uneven surface of some columns limited the application scenario.
Compared to single-mechanism MAMs and metasurfaces, materials with composite electromagnetic protection mechanisms based on the integration of absorption losses into the metasurface design [37] achieve multiband and multifunctional integration by acting together in the spatial and energy domains, offering the potential for better electromagnetic performance stability when applied to high temperatures as well. However, dielectric materials such as Rogers and FR-4 used in existing work [38–41], as well as magnetic materials [39] and aggregate circuit elements [40] incorporated to improve EM protection, lose their functionality at high temperatures, making them unsuitable for applications at high temperatures.
In this paper, we design a high-temperature resistant bilayer structure with a broadband low reflection by combining absorption loss and phase cancellation mechanisms. The bottom layer is a checkerboard metasurface of Al2O3 ceramic and silver, which enables the conversion of EM waves from mirror reflection to scattering. The upper layer is an absorbing layer composed of graphite and silicone rubber composites, using electrical losses to enhance the absorption of incident EM waves, while the reflection amplitude, as well as the phase of the bottom metasurface, are simultaneously modulated to enhance scattering and broaden its operating bandwidth. Compared to scattering-type metasurfaces that merely act in the spatial domain, we introduce energy loss in the energy domain, making EM protection more effective. Meanwhile, the surface is mechanically resistant, hydrophobic and oil resistant, and has a wider range of potential application scenarios. Results show, under the combined effect of the above two physical mechanisms, a low reflection of -10 dB is achieved in the 6.7–11.4 GHz range, covering virtually the entire X-band and part of the C-band. Moreover, it maintains a decent low-reflection performance after the environmental temperature is raised from 25°C to 300°C. In addition, we verified its thermal stability through long-term high-temperature and thermal cycling tests.
2. Theory and simulation analysis
Beam scattering results in phase cancellation, which is a superposition of the reflected wave vector fields between different constituent cells in the reflected array. Compared with a PEC of the same size, the normalized reflection of a reflect array consisting of m x n elementary reflecting cells can be estimated as:
The bilayer structure is shown in Fig. 1(a), with the upper layer being the absorbing layer to the lower one being the metasurface. The two elementary reflection cells 0 and 1 of the checkerboard metasurface consist of a metallic background plate, a dielectric substrate, and a metallic pattern on its surface from the bottom up. To meet the high-temperature working environment, the dielectric substrate is Al2O3 ceramics (ɛr = 9.8 and tanδ=0.015), metal background and pattern are about 0.035 mm thick silver. The metal patterns are taken in the cross and square shapes, respectively, and the geometry parameters optimized by CST Microwave Studio simulations are h = 2.3 mm, p = 7.5 mm, l = 5.9 mm, b = 0.4 mm, and a = 1 mm. The reflection amplitude and phase of the elementary reflection cells are shown in Figs. 1(b) and (c), with the minimum amplitude of cell 0 appearing at 7.5 GHz and 13.2 GHz while cell 1 appears at 10.1 GHz, indicating that the elementary reflection cells have an absorption peak. The phase difference ranges from 143° to 217°in the frequency range of 7.4 to 12.9 GHz, covering the entire X-band. After arranging the elementary cells in a 5 × 5 array alternately into a checkerboard-shaped metasurface, the reflection performance as shown in Fig. 1(d) was obtained. The ERLB (low reflection bandwidth with RL below -10 dB) is 2.3 GHz, with an average reflection of -11 dB from 8 to 12 GHz, insensitivity to TE and TM polarized incident waves due to structural Centro symmetry.
Fig. 1. (a) Proposed bilayer structure. (b) and (c) Reflection amplitude and phase of the elementary cells of the checkerboard metasurface. (d) Reflection of the checkerboard metasurface.
The absorbing layer has a thickness of t and consists of a micron-sized conductive graphite powder with effective temperature resistance and a silicone rubber material reinforced by silica bonded to the metasurface by a 0.1 mm thick high-temperature resistant adhesive. (ɛr = 2.8 and tanδ=0.001).To investigate the effect of variations in the thickness of the absorbing layer and changes in the graphite weight ratio on the reflection performance of the metasurface, a gradient variation of the thickness was set by simulation. Besides, various contents (3wt.%, 7 wt.%, 11 wt.%, 15 wt.%) of graphite were used in absorbing layers correspondingly named G3, G7, G11 and G15. The complex permittivity of the four measured by the coaxial method is shown in Figs. 2(a) and (b), the magnetic properties of the material resemble that of free space and are therefore neglected. Figures 3(a)-(d) demonstrate the absorption of the absorbing layers of various thicknesses without checkerboard metasurface, exhibiting a limited EM attenuation capability.
Fig. 2. Complex EM parameters of G3, G7, G11, G15 with (a) real part of permittivity and (b) imaginary part of permittivity.
Fig. 3. Absorption with different thicknesses of absorbing layers containing (a) 3 wt.%, (b) 7 wt.%, (c) 11 wt.% and (d)15wt.% graphite filler.
The reflection of the bilayer structure with a composite absorbing layer and the metasurface is shown in Figs. 4(a)-(d). Based on the simulation results, it is found that as the thickness of the absorbing layer increases from 0.2 mm to 4.0 mm, the reflection peak starts to increase gradually after the minimum is reached. However, the ERLB widens to a maximum and then gradually decreases while moving to the lower frequency ranges. As the weight ratio of graphite in the absorbing layer increases, the bilayer structure has a lower reflection peak and the ERLB tends to shift to a lower frequency range. Simulation results indicate that the optimized absorbing layer thickness and graphite weight ratio leads to the lowest reflection peak and maximum low reflection bandwidth of the bilayer structure. It is noted that the bilayer structure has a total thickness of 4 mm when it consists of a 1.6 mm thickness G7 absorbing layer compounded with the metasurface (TLG7-1.6). In the range of 6-12 GHz, the relative bandwidth of the ERLB is 55% with an average reflection ratio of -15.3 dB. Among them, 37% of the relative bandwidth of the ERLB in the X-band with an average reflection ratio of -17.8 dB and a peak ratio of -52 dB at 9.47 GHz.
Fig. 4. Reflection of the bilayer structure with different thicknesses of absorbing layer containing (a) 3 wt.%, (b) 7 wt.%, (c) 11 wt.% and (d)15wt.% graphite filler.
The EM property of the metasurface in the bilayer structure is determined by the structural parameters and the arrangement of the periodic cells which is less affected by the variation of the material EM parameters, making it much easiest to maintain a stable EM performance in high-temperature environments. With regards to the absorbing layer, interfacial polarization loss of the material decreases and dipole polarization and conductivity loss increase as the temperature increases, leading to changes in EM parameters, thus affecting the EM performance of the bilayer structure. To verify the high-temperature EM performance of the bilayer structure, the reflection spectrum at different temperatures was simulated based on TLG7-1.6. According to the prediction of the Debye theory, the permittivity of G7 at different temperatures is set as shown in Figs. 5(a) and (b), while the simulated values of Al2O3 are 9.8, 10.1 and 10.4 at 25°C, 150°C and 300°C, respectively. The reflection peak of TLG7-1.6 remains at a low ratio of about -30 dB as the temperature increases to 300°C along with the ERLB moving to a lower frequency range by less than 0.5 GHz, demonstrating good temperature resistance of the EM properties of the bilayer structure, depicted in Fig. 5(c).
Fig. 5. Simulated EM parameters of G7 at 25°C,150°C and 300°C with (a) real part of permittivity and (b) imaginary part of permittivity. (c)The simulated reflection of TLG7-1.6 at 25°C, 150°C and 300°C.
Figure 4(a)-(d) reveals the effect of the changes in the graphite weight ratio and thickness of the absorbing layer on the reflection performance of the bilayer structure at room temperature. Further, we investigated the effect of both changes at 300°C. Maintain the high-temperature EM parameters of Al2O3 and G7 of TLG7-1.6, and set G3, G11 and G15 as shown in Figs. 6(a) and (b). Figure 6(c) shows the changes in the reflection when varying the graphite content of the absorbing layer. While changing the thickness of the absorbing layer, the corresponding change of reflection is shown in Fig. 6(d). As the graphite weight ratio of the absorbing layer decreases and the thickness decreases, the reflection peak of the bilayer structure decreases and moves toward the higher frequency range together with the ERLB, which is opposite to the trend shown in Fig. 5(c). Therefore, for the high-temperature working environment, the graphite weight ratio of the absorbing layer can be reduced or its thickness can be appropriately reduced to cope with the increase in reflection peak and shift in ERLB due to temperature increase.
Fig. 6. Simulated complex EM parameters of G3, G11 and G15 at 300°C with (a) real part of permittivity and (b) imaginary part of permittivity. The reflection of the bilayer structure is simulated at 300°C with (c) The thickness of the absorbing layer maintained at 1.6 mm, and the absorbing material is changed and (d) Maintaining the absorbing material as G7 and changing the thickness of the absorbing layer.
To clarify the coupling effect with the metasurface after the introduction of the absorbing layer, Figs. 7(a) and (b) show the reflection amplitude and phase on cells 0 and 1 in TLG7-1.6, respectively. Unlike direct incidence from free space, the EM wave is first incident on the absorbing layer and then arrives at the metasurface introducing an additional optical range, which causes a change in the reflection phase of cells 0 and 1. The phase difference between the two no longer satisfies 143°<Δϕ<217° at 9-11 GHz. Also, the reflection amplitude is further reduced due to the loss of the absorbing layer. The minimum amplitude of cell 0 is 0.74 and 0.68, respectively, and moves to the lower frequency range at 6.7 GHz and 11.9 GHz, while the minimum amplitude of cell 1 is 0.84 at 9 GHz.
Fig. 7. (a) and (b) Reflection amplitude and phase of the elementary cells of the metasurface layer of TLG7-1.6. (c) The calculated proportion of reflected, absorbed and reflected EM energy of the metasurface layer and the simulated reflection result of the bilayer structure.
Based on Eq. (2), the percentage of energy reflected or scattered by the metasurface back to the absorbing layer, and absorbed directly by it, can be further simplified as Eqs. (4)–(6):
From the calculated results in Fig. 7(c), most of the energy within 6.5 GHz-12.5 GHz is directly absorbed by the metasurface or scattered back to the absorbing layer, and only small amounts of energy are reflected to the absorbing layer. S.reflection is the simulated result of TLG7-1.6 with 300 mm × 300 mm size, which shows the percentage of incident EM wave energy reflected to free space after the coupling effect of the absorbing layer and metasurface.
According to the calculated results, at around 7.5 and 11.5 GHz, few incident wave energies are directly absorbed, most of them return to the absorbing layer in the form of scattered energy, and almost no reflected energy returns to the absorbing layer. However, the result of S.reflection is different, indicating that reflected energy is returning from the metasurface to the absorbing layer and back to free space after transmission through it. We believe that this error stems from the difference between the calculation and the simulation model since the calculation involves a periodic model of infinite size with no boundary effects or intercellular coupling. Simulation models are limited in size and the effects of any of them can no longer be ignored. Similarly, the calculated result shows that there is more reflected energy back to the absorbing layer at 9-10.5 GHz. Whereas, the reflected energy in free space at 9–10.5 GHz is extremely rare according to the result of S. Reflection. Therefore, we believe that the reflected energy returning to the absorbing layer is absorbed by it.
Consequently, as shown in Fig. 8(a), we intercepted one repetition period of TLG7-1.6 as a reference and compared the loss density at 6.9 GHz, 9.5 GHz and 11.2 GHz. Figures 8(b)-(d) are top views showing the loss density distribution of the absorbing layer. As shown in Figs. 8(b) and (d), the scattered energy loss occurs in the absorbing layer mainly in several oblique directions at 6.8 GHz and 11.2 GHz. While, at 9.5 GHz shown in Fig. 8(c), in addition to the scattered energy loss in the four oblique directions of the absorbing layer, there is also a strongly reflected energy loss in the + Z vertical direction. Figures 8(e)–(g) provide side views. Compared with Figs. 8(e) and (g), at 9.5 GHz shown in Fig. 8(f), virtually no far-field energy is available in the vertical reflection direction due to the loss of reflected energy in the absorbing layer.
Fig. 8. Side views of simulated loss density and far-field results for one repetition of TLG7-1.6 and top views of loss density in the absorbing layer. (a) One repetition period. (b), (e) At 6.9 GHz. (c), (f) At 9.5 GHz. (d), (g) At 11.2 GHz.
Further, the scattered patterns at 6.9 GHz, 9.5 GHz and 11.2 GHz were analyzed, and the checkerboard metasurface without a composite absorbing layer of the same size and the perfect electric conductor PEC were selected for comparison. As shown in Figs. 9(a)–(c), the incident waves generate strong reflections on the PEC surface at different frequency points. However, the reflection from the TLG7-1.6 surface is significantly reduced and leads the incident wave to scatter in the four main directions of phi = 45°, 135°, 225° and 315°. According to the generalized Snell's law, the angle of scattering can be calculated as:
Fig. 9. (a) – (c) Two-dimensional scattering angle diagram of TLG7-1.6 and PEC. (d) – (f) Three-dimensional scattering pattern of TLG7-1.6 and the checkerboard metasurface. (a), (d) At 6.9 GHz. (b), (e) At 9.5 GHz. (c), (f) At 11.2 GHz.
Figures 9(d)–(f) shows that both TLG7-1.6 and the checkerboard metasurface without the composite absorbing layer led to the scattering of the incident wave, but there are differences in the scattering patterns at different frequencies between the two. The scattering characteristics of the checkerboard metasurface are determined by the reflection amplitude and phase of the elementary cell 0 and 1, while the bilayer structure TLG7-1.6 enhances the coupling effect of the absorbing layer. As shown in Fig. 9(d), the Δφ of TLG7-1.6 increases from 58° to 132° at 6.9 GHz, while A0 and A1 decrease further, due to Eqs. (4)–(6), only a small amount of reflected energy is generated to appear in free space. In Figs. 9(e)–(f), TLG7-1.6 shows similar scattering patterns with the checkerboard metasurface. Notably, at 9.5 GHz, the absorbing layer of TLG7-1.6 absorbs much of the reflected energy, resulting in almost no reflected energy in the free space of the far field. However, at 11.2 GHz, the Δφ of TLG7-1.6 is reduced from 156° to 147°, but benefits from a further reduction of A0 and A1, making no significant difference between its scattering pattern and that of the checkerboard metasurface.
3. Fabrication and experiment
The results obtained from the simulation were verified by making a 300 mm × 300 mm sample of TLG7-1.6 for the experimental test. The main fabricated steps of the absorbing layer are shown in Fig. 10(a). The precursor consisted of 3wt.% MH360 hydrogen-containing silicone oil, 88 wt.% MP5000 vinyl silicone oil (Shanghai Silicon Power High-Tech Materials Co., Ltd.) and 9 wt.% silica Aerosil R812S (Shanghai Evonik Specialty Chemicals China Co., Ltd.). Subsequently, 15.2 g of 8000-mesh conductive graphite (Shenzhen Hanhui Graphite Co., Ltd.) was added to 200 g of precursors. The above was dispersed with a magnetic stirrer at 400r/min for 4 hours and eliminated air bubbles were in a vacuum for 1 hour. After eliminating the air bubbles, the mixture was added with 1 g of platinum catalyst, briefly mixed with a glass stirring bar and poured into a 300 mm × 300 mm × 1.6 mm mold, and cured at 150°C for 1 h for molding.
Fig. 10. (a) Checkerboard metasurface layer sample and its fabrication process. (b) Absorbing layer sample and its fabrication process.
The checkerboard metasurface is fabricated by screen printing as shown in Fig. 10(b). First, a 300-mesh screen is used to print metal patterns on the surface of the Al2O3 ceramic (Guangzhou Baile New Material Co., Ltd.), and the conductive silver paste (Shanghai Jurong Electronic Technology Co., Ltd.) is evenly printed on the surface of the ceramic substrate. Later, the sample was dried at 150°C for 30 min, and finally, the finished product was sintered at 800°C for 3 h. The step of printing the silver background on the other side of the Al2O3 ceramic was omitted because the metal plate on which the sample was placed provided a metal background for the metasurface during the test. Finally, the absorbing layer is bonded to it by a 380°C high-temperature resistant glue.
The arch method executes the reflection test in Fig. 11(a). The equipment mainly consists of an Agilent N5227B vector network analyzer, a metal heating table surrounded by absorbing cones for sample placement, and two rectangular angular antennas operating at 0.5-18 GHz and fixed on arch-shaped support for transmitting and receiving EM waves. Before formal testing, the reflection of the metal heating table without the sample placed was measured for calibration. Figure 11(b) shows the measurement results at temperatures of 25°C, 150°C and 300°C. It can be seen that when the temperature rises from room temperature to 300°C, the reflection peak of the bilayer structure increases and moves toward the lower frequency range together with the ERLB, consistent with the simulation results. The thermal stability of the bilayer structure was further evaluated by continuous high-temperature testing and thermal cycling tests. After the sample was heated to 300°C, it was kept continuously for about 30 and 60 minutes as shown in Fig. 11(c). The results show that the reflection of the bilayer structure tested remains well stabilized under the long-term high-temperature environment. Analogous results can be observed under the thermal cycling test, as shown in Fig. 11(d). In the thermal cycling test, a thermal cycle was completed by heating the sample from room temperature to 300°C at a rate of 60°C/min and maintaining 5 min, followed by natural cooling to room temperature and recording the reflection curve. The heating process lasts about 5 min and the cooling process lasts about 1 hour. On balance, the measurement results show that our designed bilayer structure can achieve good low reflection performance within 6.7–11.4 GHz and demonstrate good stability from 25°C to 300°C.
Fig. 11. (a) Experimental setup. (b) The measured results at 25°C, 150°C and 300°C, compared with the simulated result at 25°C. (c) Continuous high-temperature test. (d) Thermal cycling test.
4. Conclusion
In summary, we propose a thermally stable checkerboard metasurface with the mechanism of phase cancellation to convert EM waves from specular reflection to scattering and thus achieve EM protection, based on the potential of the metasurface to maintain steady EM properties under high temperatures. Subsequently, a high-temperature resistant absorbing layer is compounded above the metasurface to enhance the absorption of incident EM waves by using the electric loss mechanism of the absorbing material, while modulating the reflection amplitude and phase of the metasurface to enhance scattering and expand its operating bandwidth. Results suggest a -10 dB low reflection in the range of 6.7–11.4 GHz is achieved by the bilayer structure under the combined effect of the above two physical mechanisms. Furthermore, as the ambient temperature rises from 25°C to 300°C, its broadband low-reflection performance remains stable, in addition, the thermal stability of the bilayer structure was further verified by long-term high-temperature and thermal cycling tests. The proposed structure is easy to fabricate and the performance is insensitive to temperature. Improving on this basis will lead to further breakthroughs in the operating bandwidth and expansion to higher temperatures for applications.
Funding
National Natural Science Foundation of China (51902269).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. H. Wang and D. Zhu, “Double layered radar absorbing structures of Silicon Carbide fibers/polyimide composites,” Synth. Met. 246, 213–219 (2018). [CrossRef]
2. Z. Nie, Y. Feng, Q. Zhu, Y. Xia, L. Luo, L. Ma, J. Su, X. Hu, R. Wang, and S. Qi, “Layered-structure N-doped expanded-graphite/boron nitride composites towards high performance of microwave absorption,” J. Mater. Sci. Technol. 113, 71–81 (2022). [CrossRef]
3. D. Micheli, A. Vricella, R. Pastore, and M. Marchetti, “Synthesis and electromagnetic characterization of frequency selective radar absorbing materials using carbon nanopowders,” Carbon 77, 756–774 (2014). [CrossRef]
4. Y. Li, D. Li, H. Luo, F. Chen, X. Wang, and R. Gong, “Co-Evaluation of Reflection Loss and Surface Wave Attenuation for Magnetic Absorbing Material,” IEEE Trans. Antennas Propag. 66(11), 6057–6060 (2018). [CrossRef]
5. A. Teber, I. Unver, H. Kavas, B. Aktas, and R. Bansal, “Knitted radar absorbing materials (RAM) based on nickel–cobalt magnetic materials,” J. Magn. Magn. Mater. 406, 228–232 (2016). [CrossRef]
6. H. Y. Atay and Ö. İçin, “Manufacturing radar-absorbing composite materials by using magnetic Co-doped zinc oxide particles synthesized by Sol-Gel,” J. Compos. Mater. 54(26), 4059–4066 (2020). [CrossRef]
7. Z. Jiang, P. Wang, J. Xing, X. Jiang, and J. Zhao, “Screening and Design of Novel 2D Ferromagnetic Materials with High Curie Temperature above Room Temperature,” ACS Appl. Mater. Interfaces 10(45), 39032–39039 (2018). [CrossRef]
8. N. Bai, W. Xiang, J. Shen, C. Shen, and X. Sun, “A Ka -Band Folded Waveguide Traveling Wave Tube With Lumped Resistance Metamaterial Absorber,” IEEE Trans. Electron Devices 67(3), 1248–1253 (2020). [CrossRef]
9. Y. Hou, B. Xiao, Z. Sun, W. Yang, S. Wu, S. Qi, G. Wen, and X. Huang, “High temperature anti-oxidative and tunable wave absorbing SiC/Fe3Si/CNTs composite ceramic derived from a novel polysilyacetylene,” Ceram. Int. 45(13), 16369–16379 (2019). [CrossRef]
10. C. Luo, T. Jiao, J. Gu, Y. Tang, and J. Kong, “Graphene Shield by SiBCN Ceramic: A Promising High-Temperature Electromagnetic Wave-Absorbing Material with Oxidation Resistance,” ACS Appl. Mater. Interfaces 10(45), 39307–39318 (2018). [CrossRef]
11. H. Wang, D. Zhu, W. Zhou, and F. Luo, “High temperature electromagnetic and microwave absorbing properties of polyimide/multi-walled carbon nanotubes nancomposites,” Chem. Phys. Lett. 633, 223–228 (2015). [CrossRef]
12. X. Yang, Y. Duan, S. Li, H. Pang, L. Huang, Y. Fu, and T. Wang, “Bio-Inspired Microwave Modulator for High-Temperature Electromagnetic Protection, Infrared Stealth and Operating Temperature Monitoring,” Nano-Micro Lett. 14(1), 28 (2022). [CrossRef]
13. L. Pang, J. Wang, S. A. Chen, H. Luo, X. Fan, Y. Li, W. Zhou, and P. Xiao, “Multiple dielectric behavior of Cf-SiCNFs/Si3N4 ceramic composite at high temperatures,” Ceram. Int. 47(3), 4127–4134 (2021). [CrossRef]
14. X. Lan and Z. Wang, “Efficient high-temperature electromagnetic wave absorption enabled by structuring binary porous SiC with multiple interfaces,” Carbon 170, 517–526 (2020). [CrossRef]
15. C. Gao, Y. Jiang, D. Cai, J. Xu, and W. Xiao, “Effect of Temperature on the Microwave-Absorbing Properties of an Al2O3–MoSi2 Coating Mixed with Copper,” Coatings 11(8), 940 (2021). [CrossRef]
16. C. Luo, Y. Tang, T. Jiao, and J. Kong, “High-Temperature Stable and Metal-Free Electromagnetic Wave-Absorbing SiBCN Ceramics Derived from Carbon-Rich Hyperbranched Polyborosilazanes,” ACS Appl. Mater. Interfaces 10(33), 28051–28061 (2018). [CrossRef]
17. H. Wang, D. Zhu, W. Zhou, and F. Luo, “Electromagnetic and microwave absorbing properties of polyimide nanocomposites at elevated temperature,” J. Alloys Compd. 648, 313–319 (2015). [CrossRef]
18. X. Yuan, L. Cheng, S. Guo, and L. Zhang, “High-temperature microwave absorbing properties of ordered mesoporous inter-filled SiC/SiO2 composites,” Ceram. Int. 43(1), 282–288 (2017). [CrossRef]
19. M.-S. Cao, W.-L. Song, Z.-L. Hou, B. Wen, and J. Yuan, “The effects of temperature and frequency on the dielectric properties, electromagnetic interference shielding and microwave-absorption of short carbon fiber/silica composites,” Carbon 48(3), 788–796 (2010). [CrossRef]
20. T. Shao, H. Ma, J. Wang, M. Feng, M. Yan, J. Wang, Z. Yang, Q. Zhou, H. Luo, and S. Qu, “High temperature absorbing coatings with excellent performance combined Al2O3 and TiC material,” J. Eur. Ceram. Soc. 40(5), 2013–2019 (2020). [CrossRef]
21. W. Zhang, H. Xiang, F.-Z. Dai, B. Zhao, S. Wu, and Y. Zhou, “Achieving ultra-broadband electromagnetic wave absorption in high-entropy transition metal carbides (HE TMCs),” J. Adv. Ceram. 11(4), 545–555 (2022). [CrossRef]
22. C. Wang, Y. Yang, Q. Liu, D. Liang, B. Zheng, H. Chen, Z. Xu, and H. Wang, “Multi-frequency metasurface carpet cloaks,” Opt. Express 26(11), 14123–14131 (2018). [CrossRef]
23. A. Zaidi, N. A. Rubin, A. H. Dorrah, J. S. Park, and F. Capasso, “Generalized polarization transformations with metasurfaces,” Opt. Express 29(24), 39065–39078 (2021). [CrossRef]
24. H. Zhang, Y. Liu, Z. Liu, X. Liu, G. Liu, G. Fu, J. Wang, and Y. Shen, “Multi-functional polarization conversion manipulation via graphene-based metasurface reflectors,” Opt. Express 29(1), 70–81 (2021). [CrossRef]
25. W. M. Pan and J. S. Li, “Diversified functions for a terahertz metasurface with a simple structure,” Opt. Express 29(9), 12918–12929 (2021). [CrossRef]
26. Y. Wang, H. Wang, R. Su, S. Li, X. Tu, J. Wu, C. Zhang, B. Jin, H. Wang, J. Chen, and P. Wu, “Flexible bilayer terahertz metasurface for the manipulation of orbital angular momentum states,” Opt. Express 29(21), 33445–33455 (2021). [CrossRef]
27. F. Yuan, G.-M. Wang, H.-X. Xu, T. Cai, X.-J. Zou, and Z.-H. Pang, “Broadband RCS Reduction Based on Spiral-Coded Metasurface,” IEEE Antennas Wirel. Propag. Lett. 16, 3188–3191 (2017). [CrossRef]
28. Y. Meng, J. Wang, W. Wang, L. Zheng, Y. Li, H. Ma, and S. Qu, “Electromagnetic Signal Modulation by Chromatic Dispersion in Phase Gradient Metasurface,” IEEE Access 10, 90752–90760 (2022). [CrossRef]
29. T. Liu, Y. Meng, H. Ma, R. Zhu, S. Huang, C. Xu, L. Zhang, J. Wang, and S. Qu, “Broadband surface wave coupler with low infrared emission and microwave reflection,” Opt. Express 29(22), 35490–35500 (2021). [CrossRef]
30. T. Liu, Y. Meng, H. Ma, C. Xu, X. Wang, S. Huang, S. Zhao, L. Zheng, and S. Qu, “Simultaneous reduction of microwave reflection and infrared emission enabled by a phase gradient metasurface,” Opt. Express 29(22), 35891–35899 (2021). [CrossRef]
31. Y. Fan, J. Wang, Y. Li, J. Zhang, Y. Pang, Y. Han, and S. Qu, “Low-RCS Multi-Beam Metasurface-Inspired Antenna Based on Pancharatnam–Berry Phase,” IEEE Trans. Antennas Propag. 68(3), 1899–1906 (2020). [CrossRef]
32. Y. Wang, Y. Yuan, G. Yang, X. Ding, Q. Wu, Y. Jiang, S. N. Burokur, and K. Zhang, “Perfect Control of Diffraction Patterns with Phase-Gradient Metasurfaces,” ACS Appl. Mater. Interfaces 14(14), 16856–16865 (2022). [CrossRef]
33. X. Xie, M. Pu, Y. Huang, X. Ma, X. Li, Y. Guo, and X. Luo, “Heat resisting metallic meta-skin for simultaneous microwave broadband scattering and infrared invisibility based on catenary optical field,” Adv. Mater. Technol. 4(2), 1800612 (2019). [CrossRef]
34. L. Sun, X. Wang, Z. Yu, J. Huang, and L. Deng, “Patterned AlN ceramic for high-temperature broadband reflection reduction,” J. Phys. D: Appl. Phys. 52(23), 235102 (2019). [CrossRef]
35. T. Han, K. Wen, H. Lu, X. Wang, L. Zhang, D. Liang, and L. Deng, “High-temperature broadband reflection reduction: design, fabrication, and characterization,” Opt. Express 29(26), 42621 (2021). [CrossRef]
36. C. Ji, J. Peng, L. Yuan, C. Huang, and X. Luo, “All-Ceramic Coding Metastructure for High-Temperature RCS Reduction,” Adv. Eng. Mater. 24(8), 2101503 (2022). [CrossRef]
37. W. Pan, C. Huang, M. Pu, X. Ma, J. Cui, B. Zhao, and X. Luo, “Combining the absorptive and radiative loss in metasurfaces for multi-spectral shaping of the electromagnetic scattering,” Sci. Rep. 6(1), 21462 (2016). [CrossRef]
38. C. Ji, C. Huang, X. Zhang, J. Yang, J. Song, and X. Luo, “Broadband low-scattering metasurface using a combination of phase cancellation and absorption mechanisms,” Opt. Express 27(16), 23368–23377 (2019). [CrossRef]
39. S. Leung, C. P. Liang, X. F. Tao, F. F. Li, Y. Poo, and R. X. Wu, “Broadband radar cross section reduction by an absorptive metasurface based on a magnetic absorbing material,” Opt. Express 29(21), 33536–33547 (2021). [CrossRef]
40. C. Li, Z. Xu, L. Lin, S. Guo, Y. He, L. Miao, and J. Jiang, “Ultralow Scattering and Broadband Metasurface Using Phase Adjustable FSS Elements Embedded With Lumped Resistors,” IEEE Antennas Wirel. Propag. Lett. 20(5), 793–797 (2021). [CrossRef]
41. F. Yuan, Q. Chen, Y. Zheng, and Y. Fu, “Dual-Mechanism Absorptive Metasurface with Wideband 20 dB RCS Reduction,” Crystals 12(4), 493 (2022). [CrossRef]
