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1.
Junjie Qian Bin Du Chao He Mei Cai Xinrong Zhong Sizhu Ren Jiayi Lou Anze Shui 《Journal of the American Ceramic Society》2022,105(5):3339-3352
The development of electromagnetic wave (EMW) absorption materials with lightweight, wide absorption bandwidth, thin thickness, and strong EMW absorption performance has become a hotspot. Herein, the morphology-controlled preparation of α-manganese dioxide (α-MnO2) was successfully obtained via a facile hydrothermal method, and the EMW absorption performance of α-MnO2 was investigated in detail. The results indicated the as-obtained Mn-1.0-120 possessed the best EMW absorption performance with minimum reflection loss of −53.43 dB at about 5.2 GHz with a thickness of 4.1 mm originated from the synergistic effects of multiply scattering, dielectric loss, and magnetic loss. This contribution demonstrates that the MnO2 has promising candidates with a tunable EMW absorption performance for applications in the electromagnetic field in the future. 相似文献
2.
《Ceramics International》2023,49(18):30125-30136
Rational multicomponent regulation and microstructure design have proven to be effective strategies for achieving high performance electromagnetic wave (EMW) absorbers. Herein, the ultralight hierarchically porous SiC/SiO2 aerogels (HPSA) were successfully synthesized by an ingenious one-step method to achieve carbonization and carbothermal reduction. The composition of the HPSA and the quantity of SiC/SiO2 fibers grown by in situ reaction can be controlled by adjusting the amount of silicon source introduced. The results indicate that the composition of HPSA and the quantity of fibers have a significant effect on the EMW absorption properties. When the introduced silicon source concentration was 0.7 mol/L, the HPSA exhibited excellent EMW absorption performance, with a minimum reflection loss (RLmin) of -55.01 dB at 6.00 GHz and a maximum effective absorption bandwidth (EABmax) of 6.16 GHz. The highly interconnected porous SiC/SiO2 skeleton structure significantly contributes to the multiple reflection-absorption effect of EMW and provides available pathways for electron conduction losses. The in situ reaction generates SiC/SiO2 fibers with a large number of stacking faults and heterojunctions, which further promote the dissipation of EMW. In addition, the maximum radar cross section of HPSA under far-field conditions is reduced to 20.21 dB m2 compared to the PEC conductive layer, which implies a much lower probability of detection by radar. In brief, this work provides a reference for the use of highly efficient EMW absorbers and electromagnetic stealth materials. 相似文献
3.
《Ceramics International》2022,48(4):4986-4998
In this paper, the mixture of Fe and Ni nanoparticles (abbreviated as FeNi) was added to liquid polysilazane (PSZ) as a magnetic source, to prepare a series of magnetic carbon-rich SiCN-based composite ceramics by adjusting the mass ratio of FeNi through the polymer derivation method. The phase composition, microstructure, conductivity, electromagnetic wave (EMW) absorption performance and mechanism of composite ceramics prepared were discussed. The analysis shows that the introduction of magnetism has adjusted the impedance matching and improved the magnetic loss performance of composite ceramics on the whole, and the dielectric loss ability of composite ceramics has been strengthened benefiting from the formation of conductive path of CNTs precipitated by FeNi catalysis in the matrix. Therefore, the addition of magnetic particles improves the EMW absorption peak intensity and effective absorption bandwidth (EAB) of composite ceramics. When the addition amount of FeNi was 5 wt%, the sample 5# exhibited the best comprehensive EMW absorption performance: Its minimum reflection loss (RLmin) was ?18 dB and the EAB was 2.5 GHz when the thickness was 1 mm, the EAB covering the C, X and Ku bands can be obtained by adjusting the thickness from 1.0 mm to 4.0 mm. Through calculation, the EAB (EABtf) of 5# with a thickness of 1 mm and a filling rate of 1 wt% can reach 50, which is significantly higher than that of a series of SiCN-based composite ceramics previously reported. In addition, the density of 5# was 2.3 g/cm3, and its compressive strength (CS) can reach 337 MPa. The data shows that the composite ceramic 5# prepared in this experiment has the merits of light weight, excellent comprehensive EMW absorption performance and good compression resistance, and is expected to be one of the promising materials in the field of new-generation EMW absorbers. 相似文献
4.
《Ceramics International》2022,48(16):22896-22905
Spinel ferrites are widely used for electromagnetic wave (EMW) absorption applications. In this study, spinel Ni–Zn ferrites with excellent microwave absorption properties were synthesized. Their EMW absorption characteristics and interaction mechanisms were studied to lay the foundation for the study of the role of Ni–Zn ferrite as a magnetic substrate for composites. Herein, Ni0·5Zn0·5Fe2O4 was prepared by the hydrothermal method (H-NZFO) and the sol–gel auto-combustion method (S-NZFO); both samples exhibited distinct microwave absorption properties. The S-NZFO absorber (thickness = 3.72 mm) demonstrated the best dual-zone microwave absorption with two strong reflection loss peaks at 5.1 and 10.5 GHz. The corresponding effective absorption bandwidth (EAB) reached 9.0 GHz, which covered part of the S-band and all of the C- and X-bands. These results were attributed to the high saturation magnetization, outstanding complex permeability, and multiple magnetic loss channels of S-NZFO. The H-NZFO sample exhibited excellent absorption capability and matching thickness. At a thickness as low as 1.71 mm, the minimum reflection loss (RLmin) of the H-NZFO absorber reached -60.2 dB at 13.1 GHz. The maximum bandwidth corresponding to RL below -10 dB was 4.6 GHz. These results can be attributed to small particle size, high complex permittivity, and multiple dielectric loss channels of H-NZFO. The observed wide effective absorption bandwidth of S-NZFO and strong microwave absorption capability of H-NZFO suggest the potential of both materials as substrates for efficient microwave absorbers in military as well as civilian absorption applications. 相似文献
5.
《Ceramics International》2023,49(18):30214-30223
The development of ultralightweight and broadband electromagnetic wave (EMW) absorbing materials remains a big challenge. In this work, porous magnesium ferrite microspheres decorated nitrogen-doped reduced graphene oxide (NRGO/MgFe2O4) composite aerogels were prepared by a two-step route of solvothermal synthesis and hydrothermal self-assembly. Results of microscopic morphology characterization showed that NRGO/MgFe2O4 composite aerogels had a unique hierarchical porous structure. Moreover, the influence of additive amounts of graphene oxide on the electromagnetic parameters and EMW absorption properties of NRGO/MgFe2O4 composite aerogels was explored. Remarkably, the attained binary composite aerogel with the content of NRGO of 70.21 wt% exhibited the best EMW absorption performance. The minimum reflection loss reached up to −55.7 dB, and the corresponding effective absorption bandwidth was as large as 5.36 GHz at a thin matching thickness of 1.98 mm. Furthermore, when the matching thickness was slightly increased to 2.29 mm, the widest effective absorption bandwidth was enlarged to 7.1 GHz, covering the entire Ku-band. The magnetodielectric synergy and unique hierarchical porous structure in NRGO/MgFe2O4 composite aerogels not only improved the impedance matching, but also greatly enhanced the EMW absorption capacity. It was believed that the results of this work could be helpful for the preparation of graphene-based magnetic composites as broadband and efficient EMW absorbers. 相似文献
6.
Yurun Feng Xue Guo Junbin Lu Jie Liu Guantong Wang Hongyu Gong 《Ceramics International》2021,47(14):19582-19594
The SiCN(Fe) fibers with excellent one-dimensional microstructure and electromagnetic wave (EMW) absorption performance were synthesized by combining polymer-derived ceramics (PDCs) method and electrospinning. The in-situ generation of Fe3Si and CNTs by adding ferric acetylacetonate (FA) into the raw materials effectively improved the dielectric properties, magnetic properties and the impedance matching performance of the SiCN(Fe) fibers. The EMW absorption performance of SiCN(Fe) fibers were mainly based on dipole polarization loss, interface polarization loss and eddy current loss. The RLmin value of SiCN(Fe) fibers reached ?47.64 dB at 1.38 mm and the effective absorption band (EAB, RL ≤ ?10 dB) reached 4.28 GHz (13.72–18 GHz, 1.35 mm). 相似文献
7.
《Ceramics International》2023,49(20):33039-33050
Hydrotalcite-like layered double hydroxides (LDHs) exhibit distinct microstructures and atomic compositions, and thus, they are expected to be superior microwave absorbing materials. However, preparation of excellent absorbers from LDHs is still a challenging task. Herein, NiCo-LDHs@SiC/C heterostructure composites were designed and then heat-treated to obtain NiCo@SiC/C nanofibers. Finally, with a synergistic effect of dielectric and magnetic losses, the minimum reflection loss value of the sample could reach −56.3 dB with a thickness of 2.7 mm, and the maximum effective bandwidth absorption reached 6.8 GHz at 2.3 mm. Moreover, the simulated radar cross-section indicates that the NiCo@SiC/C nanofibers well suppress the electromagnetic scattering from metal trench structure. This result further indicates the outstanding microwave absorption properties of the nanofibers. This study contributes to the development of LDH materials in the field of wave-absorbing materials, and is an important guideline for exploring efficient microwave absorbers with fibrous structure. 相似文献
8.
《Ceramics International》2022,48(1):811-823
Polyaniline (PANI)-based networks combined with Fe3O4 hollow spheres and carbon balls (FCP) for improved electromagnetic wave (EMW) absorption were investigated using an easy-to-industrialize solvothermal and physical method. Hollow structure Fe3O4 spheres with a lower density than that of the common solid sphere were prepared. As a thin and light magnetic material, Fe3O4 hollow spheres generate magnetic loss, carbon balls and PANI networks generate dielectric loss. The magnetic and conductive parts play appropriate roles in achieving complementarity in the EMW absorption. The relatively high specific surface area introduced by PANI networks promotes interfacial polarization and further supports dielectric loss. In conclusion, the above reasons provide multiple attenuation mechanisms. Samples FCP1 (?65.109 dB, at 12.800 GHz, 1.966 mm, from 5.6 to 18.0 GHz) and FCP2 (?61.033 dB, at 8.480 GHz, 3.328 mm, from 4.3 to 18.0 GHz) demonstrated a wide bandwidth, a small thickness, a minimum reflection loss (RL), and a low loading ratio (25%) in paraffin-based composites. Specifically, their loading ration of 25% is much lower than the loading ratio of conventional materials (usually 50% and above). In addition, the bandwidth is excessively wide, above 12 GHz, possessing good absorption performance in continuous intervals with different thicknesses. Such excellent characteristics have rarely been reported in literature. 相似文献
9.
《Ceramics International》2023,49(5):8048-8057
To enhance the absorption performance of silicon carbide fiber (SiCf), hybrid fibers with a double shell structure (Ti3SiC2 and carbon nanotubes (CNTs)) on the SiCf (CNT@Ti3SiC2@SiCf) were successfully synthesized by the combination of molten salt method and floating catalytic chemical vapor deposition. A series of 10% weight fraction fibers reinforced paraffin samples was prepared to study the double coating influences on the electromagnetic wave (EMW) absorption performances. Coated by Ti3SiC2 and CNTs, the dielectric permittivity of hybrid fibers could be modulated in a quite wide range. The CNT@Ti3SiC2@SiCf with a thickness of 3.8 mm showed a minimum reflection loss value of ?53 dB at 6.57 GHz, and the CNT@Ti3SiC2@SiCf with a thickness of 2.5 mm presented a wide effective absorption bandwidth of 5.6 GHz (from 9 to 14.6 GHz). The highly improved EMW absorption performance of CNT@Ti3SiC2@SiCf was attributed to the combination of conductive loss and dielectric loss aroused by interfaces. The excellent absorption performance provided the modified SiCf with a high potential in the application of EMW absorbers. 相似文献
10.
《Ceramics International》2023,49(16):26642-26653
The electromagnetic wave (EMW) absorbing materials are widely applied to attenuate the useless and harmful EMW generated from wireless communication and 5G networks, which could protect the human health and electronic device safety. In this study, La-doped SiBCN ceramics with broadband EMW absorption capability were prepared via generating abundance of heterointerfaces, as graphene were in-situ grown by La2O3 catalyzing. The graphene in-situ formed in the ceramics can be attributed to the La atom decreasing the potential energy of the free carbon ring nucleation from −760.9 Ha to −8984.3 Ha. Consequently, the electrical conductivity of the SiBCN ceramics improved from 12.360 S/m to 18.025 S/m, the minimum reflection loss (RLmin) obtained was −26.48 dB at 7.2 GHz and the effective absorption bandwidth (EAB) was 6.32 GHz (11.68–18.00 GHz) at a thickness of 1.7 mm. At 700 °C, the RLmin and EAB values reached −43.18 dB and 4.2 GHz, respectively. The enhanced EMW absorbing capability can be attributed to the rationally tailor the heterointerfaces to improve the polarization loss and conduction loss of the SiBCN ceramics. The interfaces between graphene and amorphous phases generate built-in electric fields and space chare regions to strengthen the interface polarization, while the electrons migrating rapidly in the graphene and other crystals improved the electrical conductivity. The positive effect of heterointerfaces regulation of graphene in-situ growth improved the dielectric loss capacity of the SiBCN ceramics; therefore, this study provides a feasible method to enhance the EMW absorption capability of polymer-derived ceramics. 相似文献
11.
Developing light-weight, thin thickness and high-efficiency electromagnetic wave (EMW) absorbers is an effective strategy for dealing with the increasingly serious problem of electromagnetic radiation pollution. Herein, nickel/zinc oxide/carbon (Ni/ZnO/C) hollow microspheres decorated graphene composites were facilely prepared through the high-temperature pyrolysis of bimetallic NiZn metal-organic frameworks (MOFs) precursors. Morphological characterization results manifested that the Ni/ZnO/C microspheres with unique hollow structure were almost evenly anchored on the wrinkled surfaces of flake-like graphene. Moreover, the influences of additive amounts of graphene oxide (GO) in the MOFs precursors on the crystal structure, graphitization degree, micromorphology, magnetic properties, electromagnetic parameters and EMW absorption performance were investigated in detail. It was found that the superior EMW absorption performance could be achieved through facilely adjusting the additive amounts of GO in the precursors. As the additive amount of GO was equal to 60 mg, the obtained composite showed the comprehensive excellent EMW absorption performance. Notably, the optimal minimum reflection loss reached ?57.5 dB at 16.5 GHz in the Ku-band under an ultrathin matching thickness of merely 1.34 mm, and the broadest effective absorption bandwidth achieved 5.6 GHz (from 12.4 to 18 GHz) when the thickness was 1.5 mm. Furthermore, the underlying EMW absorption mechanisms of as-prepared composites were revealed. It was believed that our results could be valuable for the structural design and EMW absorption performance modulation for MOFs derived magnetic carbon composites. 相似文献
12.
Yaqing Ge Cuiping Li Geoffrey I.N. Waterhouse Zhiming Zhang Liangmin Yu 《Ceramics International》2021,47(2):1728-1739
A series of ZnFe2O4@SiO2@PPy nanocomposites with different SiO2 contents were successfully fabricated using a combination of sol-gel and in-situ polymerization processes. Spherical ZnFe2O4 particles (mean diameter ~300 nm) were first synthesized, then coated successively with conformal layers of SiO2 and polypyrrole (PPy). The electromagnetic wave (EMW) absorption properties of the resulting ZnFe2O4@(SiO2)x@PPy nanocomposites (where x = the volume of TEOS used in the synthesis) were subsequently investigated in the K band (18–26.5 GHz) and Ka band (26.5–40 GHz). Results show that the EMW absorption properties of the nanocomposites can be precisely tuned by controlling the thickness of the SiO2. Compared with ZnFe2O4@PPy, the ZnFe2O4@(SiO2)x@PPy composites exhibited enhanced re?ection losses and broader effective absorption bandwidth (EAB, reflection loss less than ?10 dB). The ZnFe2O4@(SiO2)1.0@PPy nanocomposite offered the best EMW absorption performance, with a minimum re?ection loss (RLmin) of ?29.72 dB at 24.96 GHz (EAB of 7.0 GHz, 19.5–26.5 GHz) at 1.5 mm thickness and ?36.75 dB at 38.38 GHz (EAB of 9.56 GHz, 30.44–40 GHz) at 1.0 mm thickness. The main microwave absorption mechanisms used by the ZnFe2O4@SiO2@PPy composites were magnetic losses (ZnFe2O4 nanoparticles), dielectric losses (ZnFe2O4, SiO2 and PPy) and interfacial relaxation losses (at ZnFe2O4–SiO2-PPy interfaces). Results guide the development of improved microwave absorbers in the K and Ka bands. 相似文献
13.
《Ceramics International》2022,48(2):1908-1915
A novel ternary layered ceramic of Y3Si2C2 was successfully in-situ synthesized on the surface of home-made third-generation KD-SA SiC fiber for the first time by molten salt method aimed at improving the electromagnetic wave (EMW) absorption. After in-situ synthesis of Y3Si2C2 ceramic layer on SiC fiber (SiCf/Y3Si2C2), significantly improved EMW absorption performance was obtained. The minimum reflection loss (RLmin) of ?16.97 dB was reached in SiCf/Y3Si2C2 composites at the thickness of only 2.19 mm, and the effective absorption bandwidth (EAB) was up to 5.44 GHz (12.56–18 GHz) at a thin thickness of 2.64 mm. The improvement in EMW absorption of SiCf/Y3Si2C2 is mainly attributed to enhanced dielectric loss and conduction loss resulting from increased heterogeneous interfaces and multiple reflections and scattering originating from net structure. The SiCf/Y3Si2C2 could be a promising EMW absorber for application in high-performance EMW absorbing materials. 相似文献
14.
《Ceramics International》2022,48(17):25111-25119
Electromagnetic wave (EMW) absorbing materials have been widely applied in the fields of military and engineering areas. It is of great significance to develop high-performance EMW absorbing materials. This work assembled the sandwich-like Ti3C2Tx based nanocomposites by the microwave-assisted annealing of CoFe-MOF@Ti3C2Tx (CFMF@Ti3C2Tx) precursors at different temperatures. Results show that, as the heat treatment temperature is 450 °C, the sandwich-like Ti3C2Tx@CoFe@TiO2 nanocomposites present better EMW absorption properties. The minimum reflection loss (RL) value was ?62.9 dB at 17.95 GHz with a thin thickness of 1.2 mm. Moreover, the effective absorption bandwidth (EAB) value was 5.02 GHz (12.74–17.76 GHz) with a thickness of 1.4 mm. The application of microwave-assisted annealing contributed to the formation of CoFe nanoparticles and TiO2 nanoparticles because of the ultra-fast heating rate. The introduction of the nanoparticles enhanced the multiple polarization, optimized the impedance matching and introduced magnetic loss, leading to the improvement of EMW absorption. When the annealing temperature further increased to 550 °C, the EMW absorbing performance was weakened, which was mainly correlated with the decrement of the interface area due to the increase of the TiO2 nanoparticle size and CoFe nanoparticle size. Thus, the loss effect of the multiple interface polarization weakens in the EMW absorption. In addition, the high permittivity of Ti3C2Tx disappears, which deteriorated the impedance matching and attenuation ability of EMW. Ultimately, sandwich-like Ti3C2Tx@CoFe@TiO2 nanocomposite with satisfactory EMW absorbing properties is established, promising for various EMW absorbing applications. 相似文献
15.
《Ceramics International》2023,49(6):8772-8780
Despite Co3O4 has been widely applied in electromagnetic wave (EMW) absorbers, single Co3O4 doesn't have excellent EMW absorbing performance. Modification of Co3O4 with other metal ions addition is an effective way to improve its impedance matching and EMW attenuation. Herein, CuO/Cu0.3Co2.7O4/Co3O4 and NiCo2O4/Co3O4 composites have been obtained via a facile two-stage strategy, and the influence of Cu2+ and Ni2+ on the high-frequency and low-frequency EMW absorbing performance of the composites has been investigated as well. The electromagnetic parameters of samples are regulated by adding different metal ions to achieve optimum impedance matching. Dipole polarization and magnetic resonance are the main loss mechanisms. The composite with Cu2+ and Ni2+ additions exhibits the best EMW absorption with an effective absorption bandwidth (EAB) of 10.8–18.0 GHz for 2.1 mm thickness at high-frequency and 4.5–8.5 GHz for 4.9 mm thickness at low frequencies, respectively. This work offers an effective method for preparing composite materials with multicomponent broadband absorption of oxides. 相似文献
16.
Maoyun Liu Guantong Wang Yalan Miao Hongyu Gong Jie Jing Mingming Sheng Junbin Lu 《International Journal of Applied Ceramic Technology》2023,20(5):2930-2941
In this paper, Co2Si(Co)/SiCN composite ceramics were synthesized by simple precursor-derived ceramics method. The phase composition, morphology, and microwave absorption properties of Co2Si(Co)/SiCN composite ceramics at different pyrolysis temperatures (1000–1400°C) were studied. When pyrolysis temperature was 1300°C, carbon nanowires (CNWs), Co2Si, Si2N2O, SiC and Si3N4 were in situ generated and the best electromagnetic wave (EMW) absorption performance was obtained. The minimum reflection loss reached−50.04 dB at 4.81 mm, and the effective absorption bandwidth broadened to 3.48 GHz (14.52–18 GHz) at 1.31 mm. The excellent EMW absorption performance mainly comes from the coexistence of multiple loss mechanisms, including the magnetic loss of Co2Si, the conduction loss of CNWs, and the heterogeneous interfaces polarization between varieties of nanocrystals and amorphous ceramic matrix. By adjusting the sample thickness from 1 to 5 mm, the effective absorption of S1300 can cover the entire X and Ku bands, from 3.36 to 18 GHz. This study provides a simple way to synthesize high performance ceramic-based microwave absorbing materials. 相似文献
17.
《Ceramics International》2023,49(20):33205-33213
High-performance SiOC(Fe) wave-absorbing ceramics, containing a large number of carbon nanowires, were successfully prepared using a combination of photopolymerization 3D printing technology and the polymer-derived ceramic pyrolysis method. By employing an optimized segmented slow heating scheme with extended holding time, the pyrolysis of SiOC(Fe) ceramics at 1000 °C facilitated the growth of carbon nanowires, Fe3C and SiO2 grains. These carbon nanowires were interlaced and interconnected within the samples, forming abundant conductive networks. This highly conducive network efficiently converted electromagnetic energy into thermal energy, effectively dissipating electromagnetic waves, and consequently enhancing the microwave absorption performance of ceramics. Moreover, this approach not only reduced ceramic cracks but also improved the dielectric loss performance of the materials, achieving a minimum reflectivity value of −35.72 dB. The SiOC(Fe) ceramics added with 5 wt% VcFe effectively enhanced the magnetic loss of the material, reduced the difference between the relative complex permeability (μr) and the relative complex dielectric constant (εr), and improved the impedance matching between the material surface and air, thereby further improving its microwave absorption performance. This resulted in an increase in the maximum effective absorption bandwidth of the material to 12.7 GHz at 5 mm. This study offers a promising solution for the preparation of ceramic matrix composite materials incorporating carbon nanowires, magnetic particles and ceramic precursors, which would be potentially valuable for radar detection and sensor applications. 相似文献
18.
Yongfeng Wu Yunwang Zhong Yan Guan Chong Gu Guangyu Shao Benyang Shi Zhiming Su Binbin Xu Zhaoju Yu Anhua Liu 《Journal of the American Ceramic Society》2020,103(12):6764-6779
In this work, porous core-shell structured Co2Si@SiC/C/SiOC/SiO2/Co3O4 nanoparticles were fabricated by a polymer-derived ceramic approach. The in situ formation of mesopores on the shell, microstructural, and phase evolution of resulting nanoparticles were investigated in detail. The obtained nanoparticles-paraffin composites possess a very low minimum reflection coefficient (RCmin) −60.9 dB, broad effective absorption bandwidth 3.50 GHz in the X-band and 15.5 GHz in the whole frequency range (from 2.5 to 18 GHz). The results indicate outstanding electromagnetic wave (EMW) absorbing performance among all the reported cobalt-based nanomaterials, due to the reasons as follows: (a) The unique core-shell structure as well as complex phase composition of SiC/C/SiOC/SiO2/Co3O4 in the shell, result in a large number of heterogeneous interfaces in the nanoparticles; (b) Nanoparticles have both dielectric and magnetic loss; (c) Mesopores in the shell prolong the propagation path of EMW, thereby increasing the absorption/reflection ratio of EMWs. Thanks to the material structure design, the resulting core-shell structured cobalt-containing ceramic nanoparticles have great potential for thin and high-performance EMW absorbing materials applied in harsh environment. 相似文献
19.
《Ceramics International》2022,48(14):19882-19890
Carbon fiber reinforced unidirectional composite (CFRC) structures were developed by impregnating various dielectric and magnetic nanofillers at a 2% loading concentration of the weight of the matrix. Microwave absorption properties were studied in a broad frequency range of 0.1–13.6 GHz covering the L, S, C, and X frequency ranges. The variation of radar absorption properties with frequency were studied in detail. The effect of dielectric and magnetic materials on microwave absorption properties was also investigated. The results shows that the microwave absorption properties increases with increasing the measuring frequency and maximum absorption was at X frequency range (8.2–12.4 GHz). The Dielectric nanoparticles showed better absorption properties compared with magnetic nanoparticles. Among dielectric nanoparticles, silicon carbide showed maximum reflection loss properties of ?15.32 dB with an absorptance value of 97.06%. Among magnetic nanoparticles, ferric oxide showed a maximum reflection loss of ?9.14 dB with an absorptance value of 87.81%. The addition of nanoparticles significantly improved the complex permittivity, permeability, and loss tangent properties. 相似文献
20.
《Ceramics International》2022,48(12):16744-16753
Manganese dioxide (MnO2) has been widely utilized in the electromagnetic wave (EMW) absorption field because it exhibits numerous crystal types including α-MnO2, β-MnO2, γ-MnO2, and δ-MnO2, and is environmentally friendly. To enhance the EMW absorption performance of this material, we combined the precipitation method and calcination process to obtain γ-MnO2 microspheres, and developed a core-shell structure of γ-MnO2@SiO2 and γ-MnO2@SiO2@TiO2 microspheres via the sol-gel process. Based on the synergistic effects between the core-shell structure and dielectric loss, γ-MnO2@SiO2 with a thickness of 2.85 mm achieved the minimum reflection loss of ?60.2 dB, demonstrating that these microspheres are excellent candidates for EMW absorbers. 相似文献