共查询到20条相似文献,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(5):6338-6346
The potential of two-dimensional layered MXenes in electromagnetic wave (EMW) absorption needs further development. Herein, we carried out the in situ growth of carbon nanotubes (CNTs) on the surface of Ti3C2Tx MXene at ultra-low temperature via chemical vapor deposition. The obtained CNTs exhibited a bamboo-like structure and were accompanied by helical carbon nanofibers. The ultra-low temperature solved the problem that the high temperature required in the traditional CNT growth process would destroy the structural integrity of MXene. The lush CNT forest cross-linked the MXene layers, transforming the two-dimensional layered structure into a three-dimensional conductive network, providing abundant conductive channels for carriers, optimizing the impedance matching of the CNT/MXene hybrid, and resulting in a significant dielectric loss. The as-prepared CNT/MXene hybrid exhibited a minimal reflection loss of ?52.56 dB (99.9994% EMW absorption) in the X-band. This work proposes a new idea to enhance the EMW absorption properties of Ti3C2Tx MXene and fabricate high-performance MXene-based EMW absorbers. 相似文献
2.
《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
3.
《Ceramics International》2022,48(14):20168-20175
To improve the electromagnetic (EM) wave absorption performance of rare earth silicate in harsh environments, this work synthesized dense SiC–Y2Si2O7 composite ceramics with excellent EM wave absorption properties by using the polymer permeation pyrolysis (PIP) process, which introduced carbon and SiC into a porous Y2Si2O7 matrix to form novel composite ceramics. SiC–Y2Si2O7 composite ceramics with different numbers of PIP cycles were tested and analysed. The results show that the as-prepared composites exhibit different microstructures, porosities, dielectric properties and EM wave absorption properties. On the whole, the SiC–Y2Si2O7 composite ceramics (with a SiC/C content of 29.88 wt%) show superior microwave absorption properties. The minimum reflection loss (RLmin) reaches ?16.1 dB when the thickness is 3.9 mm at 9.8 GHz. Moreover, the effective absorption bandwidth (EAB) included a broad frequency from 8.2 GHz to 12.4 GHz as the absorbent thickness varied from 3.15 mm to 4.6 mm. In addition, the EM wave absorption mechanism was analysed profoundly, which ascribed to the multiple mediums of nanocrystalline, amorphous phases and turbostratic carbon distributed in the Y2Si2O7 matrix. Therefore, SiC–Y2Si2O7 composite ceramics with high-efficiency EM wave absorption performance promise to be a novel wave absorbing material for applications in harsh environments. 相似文献
4.
《Ceramics International》2022,48(2):1869-1878
As electromagnetic wave (EMW) pollution has become a serious problem in daily life, lightweight, efficient, and mass-produced EMW-absorbing materials are urgently needed. Herein, we developed a novel method for the continuous growth of carbon nanotubes (CNTs) on the surface of polyacrylonitrile (PAN)-based carbon fibers (CFs) by chemical vapor deposition (CVD), which can be applied to mass production. The obtained CF/CNT composites demonstrate outstanding EMW absorption capability, exhibiting a -58.75 dB reflection loss (RL) at a thickness of 1.54 mm. An effective absorption bandwidth (RL < -10 dB) of 4.24 GHz (13.76–18.00 GHz) was achieved at a thickness as low as 1.25 mm, which almost covers the entire Ku band. The excellent EMW-absorbing performance can be attributed to the 3D conductive network constructed by the CNT forest, which effectively promotes multiple reflections and scattering, and further favors dipole and interface polarizations. The mechanical properties of CF, CF-electrochemical anodic oxidation (EAO), and CF/CNT composites were examined, the results showed that the single-filament tensile strength of CF/CNT@0.07 and CF/CNT@0.09 was effectively improved. Our work suggests that the novel CF/CNT composite is a promising material for EMW absorption and strength enhancement owing to its light weight, high strength, low thickness, and good scale-up ability. 相似文献
5.
《Ceramics International》2017,43(2):1887-1894
Fe3O4/reduced graphene oxide (RGO) nanocomposite was synthesized by a simple hydrothermal method and then SiO2 coated onto Fe3O4 by a modified Stӧber method. The transmission electron microscopy and field emission scanning electron microscopy characterization indicate that masses of Fe3O4@SiO2 core-shell structure nanospheres attached to the RGO sheets, and that the thicknesses of SiO2 shells are about 20–40 nm. The X-ray diffractograms and Raman spectra illustrate that the synthesized samples consist of highly crystallized cubic Fe3O4, amorphous SiO2 and disorderedly stacked RGO sheets. The magnetic hysteresis loops reveal the ferromagnetic behavior of the samples at room temperature. In addition, the Fe3O4@SiO2/RGO paraffin composite exhibit excellent electromagnetic wave absorption properties at room temperature in the frequency range of 2–18 GHz, which are attributed to the effective complementarities between the dielectric loss and magnetic loss. For Fe3O4@SiO2/RGO-1 and Fe3O4@SiO2/RGO-2 nanocomposite, the minimum reflection loss can reach −26.4 dB and −16.3 dB with the thickness of 1.5 mm, respectively. The effective absorption bandwidth of the samples can reach more than 10.0 GHz with the thickness in the range of 1.5–3.0 mm. It is demonstrated that such nanocomposite could be used as a promising candidate in electromagnetic wave absorption area. 相似文献
6.
《Ceramics International》2022,48(24):35966-35985
With the research and development of nanomaterials, one-dimensional (1D) nanowire structures have received a lot of attention due to their unique physical and chemical properties. Among them, silicon carbide nanowires (SiC NWs) have low density, excellent oxidation resistance, dielectric properties, and electromagnetic (EM) wave absorption properties, which can well meet the development needs of civilian equipment and military weaponry. SiC NWs have outstanding research and application potential in the field of EM wave absorption. However, comprehensive summaries of SiC NWs have not been available so far. Based on this, this paper reviews the research progress of SiC NWs microwave absorbing materials, various micro-morphologies of SiC NWs are introduced in detail, as well as diverse preparation strategies and multiple growth mechanisms are also stated. Ultimately, recent advances in research progress of SiC NWs and their composites in EM wave absorption are elaborated, along with the future research directions of SiC NWs in the field of EM wave absorption. 相似文献
7.
《Ceramics International》2019,45(13):16369-16379
With the rapid development of high power electromagnetic (EM) equipment and high-speed aircraft, the powerful and high oxidation-resistance absorbers are fundamentally desirable for the EM field. Herein, a novel high temperature anti-oxidative SiC/Fe3Si/CNTs composite is synthesized by a facile polymer derived ceramic (PDC) route from a Fe-containing polysilyacetylene (PSA). The microstructure of as-prepared SiC/Fe3Si/CNTs composite absorber is featured by micro-sized SiC ceramic grains with spherical Fe3Si nanoparticles and carbon nanotubes (CNTs) attached to. The vector network analyzer tests show a tunable wave-absorbing performance by adjusting the thickness of layer, and the effective bandwidth (the reflection loss < −10 dB) is 3.3–16.8 GHz for the sample S-1400 (heat treatment at 1400 °C in nitrogen flow). The minimal RL value is −41.2 dB at 10.5 GHz at a thickness of 2 mm and an effective bandwidth is nearly 4 GHz (12.9–16.9 GHz) at the thickness of only 1.5 mm. Moreover, after the oxidation treatment at 800 °C in the air, this absorber maintains the main structure and shows a good high temperature oxidation resistance. This absorber still remains excellent wave absorption property, in view of a minimal RL value of −40 dB at the thickness of 3 mm and a bandwidth of 4.8 GHz (10.4–15.2 GHz) at the thickness of 2.5 mm. The mechanism of high EM wave absorption performance is studied and attributed to the impendence matching, polarization, and the magnetic properties. Thus, the SiC/Fe3Si/CNTs composite is a promising EM absorber for high-temperature EM wave-absorbing applications. 相似文献
8.
《Ceramics International》2022,48(20):29715-29721
In this work, the dielectric loss behavior and electromagnetic wave absorption (EMA) property of MoO2 ceramic from single crystal to polycrystal have been in-depth investigated. It is found that polycrystal MoO2 shows better dielectric loss ability than single crystal MoO2, leading to greatly enhanced EMA performance. It is determined that polarization loss occupies the dominant position in the dielectric loss of MoO2 ceramic. This research provides new insights in understanding of dielectric loss behavior and EMA mechanism for dielectric MoO2 crystals. 相似文献
9.
Cuiping Li Yaqing Ge Xiaohui Jiang Geoffrey I.N. Waterhouse Zhiming Zhang Liangmin Yu 《Ceramics International》2018,44(16):19171-19183
Porous Fe3O4/C microspheres, which were Fe3O4 nanocrystals (~8?nm) embedded in an open nanostructured carbon network, were successfully synthesized via a facile hydrothermal process. The porous Fe3O4/C microspheres possessed many distinct attributes that facilitate efficient broadband electromagnetic wave absorption (EMWA). EMWs were attenuated through multiple reflections and absorption in the 3D interconnected porous structure of the microspheres; these processes collectively improved the interaction between the EMWs and the absorber. Additionally, the carbon network and embedded Fe3O4 nanoparticles caused significant dielectric losses and magnetic losses, respectively, which also enhanced EMWA. The EMWA characteristics of the microspheres could be precisely tuned via changing the carbon content to achieve optimized impedance matching. Porous Fe3O4/C microspheres with a 71.5?wt% carbon content displayed particularly impressive EMWA properties: a maximum reflection loss (RL) value of ??31.75 across broad band frequencies in the range of 7.76–12.88?GHz (RL < ?10?dB) at an absorber thickness of 3.0?mm. These excellent EMWA properties may be attributed to both dielectric loss (carbon) and magnetic loss (Fe3O4). Additionally, the 3D interconnected porous structure of the Fe3O4/C microspheres is especially favorable for impedance matching. 相似文献
10.
Dongchao Wei Yujie Qi Senhao Lv Guimei Shi Yuxiang Dai Yang Qi 《Ceramics International》2019,45(4):4448-4454
C/ZnO composites with increased electromagnetic (EM) wave absorbing features have been synthesized through a simple one-pot hydrothermal process and subsequent high temperature carbonization under the protection of argon. The results depict that the maximum absorption of C/ZnO composites synthesized with the optimal molar ratio of zinc acetate to glucose is ?50.43?dB at 15.77?GHz. The 1.16-mm-thick coating shows a wide effective absorption bandwidth (3.52?GHz) of EM wave (RL≤?10?dB). The thin coating thickness of the C/ZnO composites is desirable for decreasing the absorber weight in EM wave absorption. And there are no other reagents used throughout the synthesis process except for the green glucose and zinc acetate. Thus, C/ZnO composites would be highly promising lightweight EM wave absorbing materials. 相似文献
11.
Xiang Gao Yan Wang Qiguan Wang Xinming Wu Wenzhi Zhang Meng Zong Lijuan Zhang 《Ceramics International》2019,45(3):3325-3332
In recent years, porous or layered magnetic materials have received increasing attention due to their low density and lightweight. In this work, porous BiFeO3 microspheres and three-dimensional porous BiFeO3 microsphere-reduced graphene oxide (RGO) composite (3D porous BiFeO3/RGO) were prepared by one-step etching processing using pure BiFeO3 particles as precursors. The precursor undergoes dissolution-recrystallization/reduction process, resulting in large amount of BiFeO3 fragments and graphene hybrid product, which forms 3D porous BiFeO3/RGO composite. Electromagnetic (EM) absorption performance measurements exhibit that at low thickness of 1.8?mm, porous BiFeO3/RGO composite can achieve reflection loss (RL) value up to ?46.7?dB and absorption bandwidth (defined by RL <?10?dB) exceeding 4.7?GHz (from 12.0 to 16.7?GHz), testifying outstanding microwave absorbing performance. Compared with pure porous BiFeO3, improved EM wave absorption ability of as-prepared porous BiFeO3/RGO composite is attributed to interfacial polarization, multiple reflections, scattering, and appropriate impedance matching. 相似文献
12.
《Ceramics International》2022,48(20):30317-30324
MXenes have been utilized to fabricate electromagnetic wave (EMW) absorbers owning to large aspect ratio, high electronic conductivity, and favorable hydrophilicity. In this work, the core-shell MXene/nitrogen-doped (N-doped) C heterostructure was firstly prepared via HCl and LiF etching, in-situ polymerization, and carbonization. When mixed with paraffin at a low filler loading of 30 wt%, the MXene/N-doped C hybrid reached a wide effective absorption bandwidth of 5.0 GHz (13.0 GHz–18.0 GHz) at a thin thickness of 1.72 mm. The stronger ability of attenuating EMWs promoted the absorption performance of MXene/N-doped C, overcoming the deficiency in the characteristics of impedance compared with its counterparts. This work provides a new insight in manufacturing MXene-based absorbers to alleviate EMW pollution by delicate structural design and effective multi-component strategy. 相似文献
13.
Lixin Chen Jia Zhao Lei Wang Fei Peng Hu Liu Jiaoxia Zhang Junwei Gu Zhanhu Guo 《Ceramics International》2019,45(9):11756-11764
Iron acetylacetonate (Fe(acac)3) modified polymethylsilsesquioxane (PMS), simplified as PMS(Fe), was firstly obtained from PMS and Fe(acac)3 via the condensation reaction. Multi-walled carbon nanotubes (MWCNTs) were then introduced to fabricate the corresponding MWCNTs/SiC nanocrystals/amorphous SiOC ceramic composites via pyrolyzed process. Owing to the catalytic effect of iron and heterogeneous nucleation promoted by MWCNTs, SiC nanocrystals were separated from SiOC amorphous ceramic matrix under 1400?°C. When the mass fraction of MWCNTs was 9?wt%, the obtained MWCNTs/SiC nanocrystals/amorphous SiOC ceramic composite (C9) demonstrated high microwave-absorbing properties. The minimum reflection loss (RLmin) and effective absorption bandwidth (EBA) of the obtained C9 at X-band (8.2–12.4) reached ?61.8?dB and 2.6?GHz (a thickness of 2.19?mm), respectively. Compared with other polymer-derived ceramics (PDCs), the RLmin was higher and the required thickness was thinner. This excellent microwave-absorbing property was due to the interfacial polarization relaxation generated between nanocrystals (MWCNTs & SiC) and amorphous SiOC, and the formed complete conductive networks inside the ceramic composites. 相似文献
14.
《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
15.
《Ceramics International》2023,49(13):21335-21345
Multi-component and a large number of non-homogeneous interface absorbers have been proven to be the preferred choice of electromagnetic wave (EMW) absorption materials. Herein, hollow porous Ni@SiC nanospheres (HPNS) were successfully constructed by combining a carbothermal reduction preparation strategy and subsequent electroless plating process. The heterogeneous dielectric/magnetic multi-component benefit to excellent EMW absorption properties through forming multiple polarizations, dielectric loss, and magnetic loss effects. Particularly, the HPNS at the optimal ratio with a low filler loading of 20 wt% exhibits the minimum reflection loss (RLmin) value of −62.39 dB at 13.28 GHz and the maximum effective absorption bandwidth (EABmax) is up to 5.36 GHz (12.64–18 GHz), and the corresponding thin matching thicknesses are 1.96 mm and 1.80 mm, respectively. Furthermore, the maximum radar cross section (RCS) reduction of HPNS over PEC reaches 26.02 dB m2 (1.96 mm) under far-field conditions, which means that the prepared HPNS is extraordinarily promising for practical applications. This work guides the preparation of high-performance EMW absorbers as well as radar stealth materials. 相似文献
16.
Bin Du Junjie Qian Ping Hu Chao He Mei Cai Xuan Wang Anze Shui 《Journal of the American Ceramic Society》2020,103(3):1732-1743
Polymer-derived ceramics (PDCs), such as SiOC, SiCN, SiBCN, and SiC are considered the best candidates for designing high-performance microwave absorber due to their controllable structure, homogeneous element composition at atom level, tunable electromagnetic and electrochemical properties. Herein, Fe ions doped silicon oxycarbide (Fe ions-SiOC) ceramics have been successfully fabricated via solvothermal method. The electromagnetic absorption performances of the nanocomposites prove to be controllable via tailoring Fe ion contents. The Fe ions effectively enhance both the interfacial polarization of amorphous SiOC, and the dielectric properties of the nanocomposites but barely effect magnetic properties of the nanocomposite. As for 0.16 mol/L-SiOC ceramics annealed at 1450°C, the effective absorption bandwidth as high as 2.00 GHz and reflection loss of −59.60 dB at 5.40 GHz with the thickness of 4.55 mm are obtained. Such work opens up a novel and simple route to scale up the PDC-based materials with broadband and excellent microwave absorbing performances. 相似文献
17.
《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
18.
Ran Mo Xiaowei Yin Fang Ye Xiaofei Liu Xiaokang Ma Quan Li Litong Zhang Laifei Cheng 《Journal of the European Ceramic Society》2019,39(4):743-754
It is difficult for ceramic matrix composites to combine good electromagnetic wave (EMW) absorption properties (reflection coefficient, RC less than -7 dB in X band) and good mechanical properties (flexural strength more than 300 MPa and fracture toughness more than 10 M P·m1/2). To solve this problem, two kinds of wave-absorbing SiC fibers reinforced Si3N4 matrix composites (SiCf/Si3N4) were designed and fabricated via chemical vapor infiltration technique. Effects of conductivity on EM wave absorbing properties and fiber/matrix bonding strength on mechanical properties were studied. The SiCf/Si3N4 composite, having a relatively low conductivity (its conduction loss is about 33% of the total dielectric loss) has good EMW absorption properties, i.e. a relative complex permittivity of about 9.2-j6.4 at 10 GHz and an RC lower than ?7.2 dB in the whole X band. Its low relative complex permittivity matches impedances between composites and air better, and its strong polarization relaxation loss ability help it to absorb more EM wave energy. Moreover, with a suitably strong fiber/matrix bonding strength, the composite can transfer load more effectively from matrix to fibers, resulting in a higher flexural strength (380 MPa) and fracture toughness (12.9 MPa?m1/2). 相似文献
19.
《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
20.
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