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1.
《Ceramics International》2023,49(20):32458-32469
Absorbers at microwave frequencies with multiple frequency-band response are particularly important for use in military for stealth technology. Specially, ferrite based absorbing materials are significant for electromagnetic shielding and signal attenuation. The enhancement of reflection loss of ferrites along with carbonaceous materials are even more beneficial. Recently double-layer absorbers have extensively studied to meet the requirements of advanced absorbing materials in multiple frequency-band response. It still remains a challenge how to determine the type and thickness to couple the impedance-matching-layer to the absorption-layers for a double-layer absorber. We applied hydrothermal method to prepare Fe3O4 nanoparticle and combine them with either graphene oxide (GO) or reduced graphene oxide (rGO) to prepare a composite of specific quality to obtain Fe3O4@GO and Fe3O4@rGO nanocomposite. We studied microwave attenuation capabilities of single and double-layer absorbers containing these two materials. We have demonstrated that with a thin impedance matching layer as a first layer and an absorbing layer behind this layer for the double-layered absorber has much higher reflection loss (RL) than a single-layer. The Fe3O4@rGO composite as a single-layer absorber shows the best microwave absorption performance with RL close to −30 dB in all three microwave bands (X, Ku and K bands). The use of a double-layer structure as Fe3O4@GO as impedance matching layer and Fe3O4@rGO as absorbing layer exhibits the best absorption of −50 dB. This is much larger than the single-layered absorbers at all three frequency-bands. Such a performance is superior to many reported ferrite-based carbonaceous composites. Therefore, a double-layer absorber is best suited to coat the whole body of the aircraft or missiles to evade satellite detection, a preparation towards new-generation weapons for future warfare. Before performing the absorption studies we have characterized the ferrites, GO and rGO materials with various microstructural and magnetic characterizations.  相似文献   

2.
The electromagnetic materials are featured by good magnetic permeability and dielectric constant characteristics, which are of significant importance in solving the pollution problem of electromagnetic. In this study, after the complete of the use of sol-gel method, argon gas was then introduced for calcination, and eventually a new type of MWCNTs/Ni0.5Zn0.5Nd0.04Fe1.96O4 composites was synthesized after the above mentioned procedures. The synthesized MWCNTs were able to be adsorbed on the surface of Ni0.5Zn0.5Nd0.04Fe1.96O4 and could form a good conductive work of 3D. Also, the effect of additional MWCNTs on microwave absorption properties of MWCNTs/Ni0.5Zn0.5Nd0.04Fe1.96O4 composites were also observed in this study. The results indicate that the additional MWCNTs function to significantly improve the microwave absorption property of MWCNTs/Ni0.5Zn0.5Nd0.04Fe1.96O4. Through altering the amount of MWCNTs, the microwave attenuation performance and impedance matching coefficient of this electromagnetic materials can be effectively improved. The S2 sample presented a minimum reflection loss of ?35.05 dB when its thickness reached 1.6 mm, meanwhile, the effective absorption bandwidth achieved 4.55 GHz. The prepared composites perform well in microwave absorption, which can attribute to the reasonable ratio of composites as well as its interaction with both of the magnetic and dielectric components. This research paved the way for novel ideas to be put in the electromagnetic absorption materials with high-efficient.  相似文献   

3.
Magnetic/dielectric composites can offer good electromagnetic impendence. However, the strategy for embodying strong absorbing ability and broad effective absorption band simultaneously is a significant challenge. Therefore, assembled porous Fe3O4@g-C3N4 hybrid nanocomposites have been designed and synthesized, in which porous Fe3O4 nanospheres assembled by ~ 3?nm Fe3O4 nanoparticles are surrounded by g-C3N4. The introduction of g-C3N4 improves dielectric loss ability at 2–18?GHz and magnetic loss ability at 2–10?GHz, and enhances attenuation constant, and increases electromagnetic impedance degree. These merits ensure that assembled porous Fe3O4/g-C3N4 hybrid nanocomposites deliver superior microwave absorption performance, such as effective absorption bandwidth, fE, (reflection loss less ??10?dB) exceeding 5?GHz at 2.0–2.3?mm, the maximal fE of 5.76?GHz and minimal reflection loss of at least ??20?dB with thickness ranging from 2.3 to 10.0?mm, avoiding the sensitivity of absorption properties to absorbing layer thickness. Stable microwave absorbing performance originates from multi-interfacial polarization, multi-reflection, enhanced electromagnetic loss capability, and good electromagnetic impedance. Our study offers a new idea for stable microwave absorber at 2–18?GHz.  相似文献   

4.
《Ceramics International》2020,46(17):26466-26485
With the advances and extensive application of electromagnetic (EM) waves in electronic and communication devices. EM pollution has been identified as a threat to human health whereby EM interference also affects the proper functioning of electronic devices. Therefore, the fabrication of novel microwave absorbing materials (MAMs) has become important to mitigate EM pollution and protect humans as well as other nearby electronic devices. The use of sole cobalt as MAM has gained significant attention due to its EM properties and suitable saturation magnetization. However, large density, eddy current loss, and poor corrosion resistance are some of the factors that hinder its practical application as an ideal MAMs. In this paper, recent advances towards overcoming these challenges have been reviewed. In particular, ways of regulating the morphology and optimizing the EM properties of cobalt-based MAM. Furthermore, fabrication of high-performance lightweight absorbers with hierarchical structures and formation of cobalt-based hybrid MAM with other lossy materials are discussed. Several factors affecting the microwave absorption performance of cobalt-based MAM are further discussed. Finally, the present limitations as well as prospects are put forward to give a new insight into the design of improved cobalt-based MAM.  相似文献   

5.
《Ceramics International》2019,45(15):18347-18355
Cobalt ferrites (CoxFe3-xO4, 0 ≤ x ≤ 1) may possess large magnetocrystalline anisotropy and coercivity at certain cobalt/iron (Co/Fe) ratios, while further explorations on their microwave absorption mechanisms are not adequate so far. In this study, a series of CoxFe3–xO4 nanocrystals were synthesized by a developed oxidation-precipitation method, and a combination of dielectric relaxation and magnetic resonance was revealed in electromagnetic studies. Dielectric relaxation peaks were originated from orientation polarization and affected by oxygen vacancy densities. Magnetic resonance peaks were shifted to higher frequency due to the increased magnetocrystalline anisotropy at higher Co/Fe ratios. The excellent microwave absorption performance of as-prepared CoxFe3–xO4 were also obtained, which should be attributed to the electromagnetic matching of dielectric relaxation and magnetic resonance at higher frequency ranges.  相似文献   

6.
《Ceramics International》2017,43(16):13146-13153
Ideal electromagnetic absorbing materials with lightweight and high efficiency have broad application outlook in military and civil fields. In this work, a 3D nanostructure material by hybridizing Fe3O4 nanocrystals and reduced graphene oxide (Fe3O4/rGO) were synthesized through an environmental-friendly one-pot solvothermal method. The effect of GO loading on electromagnetic (EM) wave absorption characteristic of Fe3O4/rGO was investigated. The introduction of rGO sheets not only prevented Fe3O4 from agglomerating, also improved the absorption performance of Fe3O4/rGO hybrids. With an appropriate addition, Fe3O4/rGO obtained a minimum reflection loss (RL) of −22.7 dB and the absorption bandwidth was 3.13 GHz (90% absorption).  相似文献   

7.
The three-dimensional porous Fe3O4/graphene composite foam as a new kind of absorbing composite with electrical loss and magnetic loss was successfully synthesized by a facile method. Fe3O4 was evenly attached on structure of graphene sheets which overlapped with each other to form three-dimensional porous graphene foam. The results revealed that when the mass ratio of graphene oxide (GO) and Fe3O4 was 1:1, the Fe3O4/graphene composite foam possessed the best absorption properties: the minimum reflection loss was up to ??45.08?dB when the thickness was 2.5?mm and the bandwidth below ??10?dB was 6.7?GHz when the content of the composite foam absorbents was just 8%. The micron-sized three-dimensional porous structure provided more propagation paths, enhancing the energy conversion of incident electromagnetic waves. The addition of Fe3O4 contributed to improving the impedance matching performance and magnetic loss. The three-dimensional porous Fe3O4/graphene composite foam was a kind of high-efficiency wave absorber, providing a new idea for the development of microwave absorbing materials.  相似文献   

8.
《Ceramics International》2020,46(4):4329-4334
The increasing electromagnetic interference problems have drawn much attention to microwave absorbing materials. To satisfy the needs of practical application, FeSiAl and flaky graphite filled Al2O3 composites were sintered by hot-pressing for microwave absorption application. The effect of FeSiAl particle size on the electromagnetic and microwave absorption properties was investigated in the X-band (8.2–12.4 GHz). The results show that the dielectric properties enhance significantly with increasing FeSiAl particle size, which is attributed to the increased interfacial polarization and conductance loss. As a result of the favorable impedance matching and appropriate electromagnetic attenuation, the reflection loss (RL) of the composites filled with 25–48 μm flaky FeSiAl achieves -15.2 dB at 10.6 GHz and the effective absorption bandwidth (RL < -10 dB) is 1.2 GHz in 10.0–11.2 GHz with a matching thickness of 1.0 mm. It indicates that FeSiAl and flaky graphite filled Al2O3 composites are potential candidates for thin-thickness microwave absorbing materials, and the microwave absorption properties can be enhanced by adjusting absorbent particle size.  相似文献   

9.
A naval hybrid buckypaper was fabricated by vacuum filtration method with monodispersion solution of Fe3O4 decorated Multiwalled carbon nanotubes (MWCNTs). The morphology, element composition and phase structure of hybrid buckypaper were characterized by field‐emission scanning electron microscope, energy dispersive spectrometer, and X‐ray diffraction. The microwave absorption and complex electromagnetic properties of the composites surface coated MWCNTs buckypaper (or Fe3O4/MWCNTs hybrid buckypaper) have been investigated in the frequency range of 8–18 GHz. The results indicate that the microwave absorption properties of composite structure have been evidently improved due to the Fe3O4/MWCNTs hybrid buckypaper' high magnetic loss and suitable dielectric loss properties. The reflection loss of composite surface coated Fe3O4/MWCNTs hybrid buckypaper (with a matching thickness d = 0.1 mm) is below ?10 dB in the frequency range of 13–18 GHz, and the minimum value is ?15.3 dB at 15.7 GHz. Thus, Fe3O4/MWCNTs hybrid buckypaper can become a promising candidate for electromagnetic‐wave‐absorption materials with strong‐absorption, thin‐thickness and light‐weight characteristics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41974.  相似文献   

10.
Composite materials made of polymers and carbon-based ferromagnetic filler are attractive for electromagnetic interference shielding through a combination of reflection and microwave absorption. It is possible to enhance their shielding properties by controlling electrical conductivity, dielectric, and magnetic properties. In this work, the aforementioned properties are tailored to achieve optically transparent films with microwave absorbing properties. Nanocarbon materials, namely carbon nanotubes, graphene nanoribbons (GNR) and their ferromagnetic nanocomposites with Fe3O4 and cobalt in PVA-PEDOT:PSS matrix were made and tested in X-band. The highest shielding effectiveness for PVA films with nanocarbon filler was observed for 0.5 wt% GNR − Fe3O4 at 16.36 dB (9.7 GHz) with 79.8% transmittance.  相似文献   

11.
《Ceramics International》2020,46(9):13397-13406
Microwave absorbing materials with enhanced microwave absorption performance and self-cleaning function are of great interest for military applications and human health caused by electromagnetic radiation pollution. Herein we report the synthesis of FeNi/NiFe2O4/NiO/C nanofibers (NFs) via electrospinning technique using nickel acetylacetonate (Ni(acac)2), ferric acetylacetonate (Fe(acac)3), and N, N-dimethylformamide (DMF)/polyacrylonitrile (PAN) solution as precursor. We also show the abilities of the materials to attenuate electromagnetic microwave and their ease of self-cleaning performance. X-ray diffraction patterns and HRTEM images reveal that the materials possess FeNi, NiFe2O4, NiO and graphite. HAADF-STEM images show that the magnetic nanoparticles distribute uniformly along the fibers. Contrast experiments had been conducted on different calcination temperatures to elucidate the impedance matching and loss mechanism. Based on the results of the experiment, excellent microwave absorption was exhibited by blending the NiFe2O4/NiO/CNFs and FeNi/NiFe2O4/NiO/CNFs into paraffin at 50 wt% and 5 wt%, respectively. Moreover, the contact angles (CA) of the as-prepared fiber films calcined at 650, 750 and 950 °C were 143°, 141° and 144°, respectively, indicating that fiber films exhibited excellent hydrophobicity and self-cleaning function. It suggested that the as-obtained NFs had an excellent application prospect in self-cleaning microwave absorbing materials.  相似文献   

12.
Ni0.5Co0.5Fe2O4/graphene composites were synthesized successfully via one-step hydrothermal method. The crystal structure, morphology and corresponding elemental distribution, electromagnetic parameters and microwave absorption performances of the as-prepared composites were measured by XRD, SEM, TEM and VNA, respectively. The results indicated that the microwave absorbing performance can be obviously enhanced through the addition of graphene in a suitable range, the magnetic loss plays a dominant contribution for the microwave absorption of composites. The maximum reflection loss of ?30.92?dB at 0.84?GHz with a ?10?dB bandwidth over the frequency range of 0.58–1.19?GHz is obtained when the composite contains 12?wt% graphene and the thickness of sample is 4?mm. This investigation presents a simple method to prepare Ni0.5Co0.5Fe2O4/graphene composites with excellent microwave absorption performance in the low frequency band of 0.1–3?GHz.  相似文献   

13.
《Ceramics International》2022,48(14):20187-20193
Microwave absorption materials need to be thin and lightweight and possess strong wave absorption ability and a wide absorption frequency band. To satisfy these conditions, we changed the microstructure of the composite by mixing ferrite material with different particle sizes. Specifically, we mixed nanosized nonmagnetic ZnFe2O4 powder into Ni0.6Zn0.4Fe2O4 powder, investigated the microwave absorption properties depending on the packing fraction. The crystal structure of the synthesized ferrite powders was analyzed through XRD, and the particle size was analyzed using a PSA and SEM. The density of the powders, which is required to measure the packing fraction, was determined via the gas disposition method, and the magnetic properties of the composites were analyzed using a VSM. The reflection loss represents the electromagnetic wave absorption characteristics, and it was calculated by substituting the measured permittivity and permeability values, into the equation based on the transmission line theory. The Ni0.6Zn0.4Fe2O4/ZnFe2O4 composite showed 99.9% absorption with a high packing fraction, and the absorption peak shifted to high frequencies. These characteristics suggest that the absorption ability and frequency range of the electromagnetic-wave-shielding composite can be easily controlled. Because of the high-absorption characteristic, absorption frequency control, and cost effectiveness, this composite can be applied to products such as thin electromagnetic-wave-shielding sheets.  相似文献   

14.
《Ceramics International》2022,48(11):15105-15115
The performance of radio frequency identification (RFID) tags deteriorates in transmitting/receiving characteristics when the tags are mounted on conductive substances such as metals due to the interference from the metal reflected electromagnetic waves. In this work, the manganese-doped magnetite (MnXFe3?XO4 (0 ≤ X ≤ 1)) nanoparticles with different manganese contents are synthesized by the one-pot sol-gel method for the application of microwave absorber. The effects of Mn doping on the morphology, microstructure, dielectric and magnetic properties, and microwave absorption ability of MnXFe3?XO4 nanoparticles are investigated. The saturation magnetization and dielectric and magnetic losses of MnXFe3?XO4 nanoparticles enhance as the Mn doping increases, and achieve the maximum when X = 0.50, and decrease as the Mn doping further continues to augment. At the optimized value of X = 0.50, the reflection and transmission losses are measured to be 17.51 and 3.88 dB, respectively. Furthermore, the nanoparticles are mixed with polytetrafluoroethylene powder and hot-pressed into a composite mat to demonstrate its application as microwave absorber. When the composite mat is inserted between the RFID tag and metal surface, the RFID tag recovers the read count by 86%, which is due to the high absorption ability (80.77%) of the composite mat. Therefore, the composition tunable MnXFe3?XO4 nanoparticles can be a potential candidate for the application of microwave absorber in wireless communication and electronic industries.  相似文献   

15.
《Ceramics International》2020,46(15):23932-23940
A three-step strategy combining solvothermal and liquid phase reduction method had been developed for preparation of magnetic triple-shell hollow structural Fe3O4/FeCo/C (TSH–Fe3O4/FeCo/C) composite microspheres. FeCo was used to enhance electromagnetic (EM) wave absorption in different frequency band and broaden effective absorbing bandwidth, while carbon was used to improve impedance matching. Triple-shell hollow structure was designed to enrich the multiple interfaces to favor the interfacial polarization, increase the multiple reflections and scattering, and provide physicochemical protection to Fe3O4 core from oxidation. The microstructure and morphology of TSH-Fe3O4/FeCo/C composite microspheres were characterized by TEM, XRD and Raman in detail. The results indicated that magnetic Fe3O4 was completely covered by FeCo and carbon via layer by layer. As an EM wave absorber, the maximum reflection loss of TSH-Fe3O4/FeCo/C composite microspheres was up to -37.4 dB due to better normalized characteristic impedance at a thickness of 2.2 mm and the bandwidth less than -10 dB even reached up to 5.9 GHz. The excellent EM wave absorption performance was attributed to the combination of shell materials (Fe3O4, FeCo and carbon) and unique triple-shell hollow structure, which lead to multiple relaxation processes and good impedance matching. Consequently, this work would contribute to the design and preparation of high performance EM wave absorbent with outstanding absorbing property and wider absorption range.  相似文献   

16.
《Ceramics International》2016,42(9):10682-10689
A ternary nanocomposite of Fe3O4@SnO2/reduced graphene oxide (RGO) with different contents of SnO2 nanoparticles was synthesized by a simple and efficient three-step method. The transmission electron microscopy and field emission scanning electron microscopy characterization display that plenty of Fe3O4@SnO2 core–shell structure nanoparticles are well distributed on the surface of RGO sheets. The X-ray diffractograms show that the products consist of highly crystallized cubic Fe3O4, tetragonal SnO2 and disorderedly stacked RGO sheets. The magnetic hysteresis measurement reveals the ferromagnetic behavior of the products at room temperature. The microwave absorption properties of paraffin containing 50 wt% products were investigated at room temperature in the frequency range of 2–18 GHz by a vector network analyzer. The electromagnetic data show that the maximum reflection loss is −45.5 dB and −29.5 dB for Fe3O4@SnO2/RGO-1 and Fe3O4@SnO2/RGO-2 nanocomposite, respectively. Meanwhile, the reflection loss less than −10 dB is up to 14.4 GHz and 13.8 GHz for Fe3O4@SnO2/RGO-1 and Fe3O4@SnO2/RGO-2 nanocomposite, respectively. It is believed that such nanocomposite could be used as promising microwave absorbers.  相似文献   

17.
Controlling material structure and its electromagnetic properties, including complex permittivity and permeability, could enhance the microwave absorption performance of the material in terms of reflection loss and effective absorption bandwidth. In this study, La-substituted barium hexaferrite, Ba3−xLaxCo2Fe24O41 (x = 0, 0.1, 0.3, and 0.5) compounds were successfully prepared using the solid-state reaction method, and their corresponding microstructures, static magnetic properties, and electromagnetic features in 2–18 GHz were investigated. The doping of La content increased saturation magnetization, coercivity, and remnant magnetization. The Ba2.7La0.3Co2Fe24O41 epoxied sample with 3.5 mm thickness possessed an excellent microwave absorption of −47.3 dB at 3.52 GHz, and its corresponding effective absorption bandwidths were 3.75 GHz (2.25–6 GHz) and 0.57 GHz (17.43–18 GHz). It is shown that doping with various La concentrations on Ba3Co2Fe24O41 can be used as an effective technique to tune the performance of microwave absorbers based on barium hexaferrite.  相似文献   

18.
Conductor-dielectric-magnetic multicomponent coordination composites with rhombic Fe2O3 lumps doping hollow ZnFe2O4 spheres through oxidative decomposition process implanted into graphene conductive network (hollow ZnFe2O4 spheres/rhombic Fe2O3 lumps/rGO composites) were successfully constructed by a facile method. The countless hollow ZnFe2O4 spheres were compactly attached to the curled-paper rGO and larger sized-rhombic Fe2O3 lumps were relatively dispersed. Among, the hollow structure of ZnFe2O4 spheres could attenuate the electromagnetic wave by multiple reflections and scatterings. Intriguingly, hollow ZnFe2O4 spheres reacted with GO to form intermediate rhombic Fe2O3 lump products, which ameliorated the hetero-interfaces structure and helped to improve impedance matching by weakening the strong magnetic ZnFe2O4 (Ms = 91.2 emu/g) and high conductive rGO after the introduction of weakly magnetic Fe2O3 semiconductor. Moreover, all three components could induce dielectric polarization losses, such as multilayer or dipole polarization. Therefore, the maximum absorption of ternary composites was up to ?64.3 dB at 7 GHz and 3.4 mm, simultaneously, and a bandwidth exceeding ?10 dB was 4.2 GHz at 1.7 mm. Meanwhile, with a thin thickness range of 1.5–5 mm, the absorption bandwidth below ?10 dB was from 2 to 18 GHz which occupied for 91.5% of whole study frequency range. These results provided a new approach and reference for the design and property regulation of electromagnetic materials at electronic communications, aerospace and military radar flied.  相似文献   

19.
Dy doped ceramic material of Ba4Fe2.6Dy1.4Nb8O30 with the tetragonal black bronze structure was synthesized by solid-state reaction at 1300°C. The composite powders of Ba4Fe2.6Dy1.4Nb8O30/FeSiAl with good flowing were prepared by spray drying using the powders slurry. The obtained composite powders were then plasma sprayed to fabricate coating. The microstructure and absorption characteristics of electromagnetic wave (EMW) of the coating materials are investigated. Results show that the composite powders significantly remain the phase stability during atmospheric plasma spraying and adsorbing heredity of EMW for the coating. The coating powders have excellent EMW absorption with the minimum reflection loss of −48.20 dB at the thickness of 3.5 mm. Also, the coating powders display the maximum effective absorption bandwidth of 6.24 GHz at the thickness of 1.5 mm, which covers the X-band. Moreover, the coating was found to have a certain EMW absorption performance at high temperature of 700°C. The Ba4Fe2.6Dy1.4Nb8O30 ceramic material with low thermal conductivity ensured the electromagnetic absorption capacity of the coating at high temperature. The Ba4Fe2.6Dy1.4Nb8O30/FeSiAl ceramic composite materials could have the potential applications as the high temperature EMW absorber.  相似文献   

20.
Silica-based ceramics have been explored extensively as a class of versatile materials for various applications in architecture, catalysis, energy, machinery, and biomedical engineering. Nevertheless, comprehensive information on silica-based ceramic and electromagnetic microwave (EMW) absorption is scarce, although excellent progress has been made in this field. Here, recent progress in the investigation of silica-based ceramics toward EMW absorption is reviewed. We first introduced the basis of ceramics (characteristics, classification, synthetic methods, potential applications). Subsequently, the silica-based ceramics, including Si-based oxides and alloys, SiOC/SiC/Si3N4/SiCN-based composite, Ti3SiC2 and composite for EMW absorption were systematically summarized. Notably, the fabrication strategies, absorption properties, and mechanisms of silica-based ceramics are described in detail, with a focus on structure and component design. Lastly, the prospects and ongoing challenges of this field in the future are presented. This review is expected to learn from the past and achieve progress toward the future of silica-based ceramic for EMW absorption.  相似文献   

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