As cutting-edge emerging electromagnetic (EM) wave-absorbing materials, the Achilles’ heel of graphenes is vulnerable to oxidation under high temperature and oxygen atmosphere, particularly at temperatures more than 600 °C. Herein, a graphene@Fe3O4/siliconboron carbonitride (SiBCN) nanocomplex with a hierarchical A/B/C structure, in which SiBCN serves as a “shield” to protect graphene@Fe3O4 from undergoing high-temperature oxidation, was designed and tuned by polymer-derived ceramic route. The nanocomplexes are stable even at 1100–1400 °C in either argon or air atmosphere. Their minimum reflection coefficient (RCmin) and effective absorption bandwidth (EAB) are −43.78 dB and 3.4 GHz at ambient temperature, respectively. After oxidation at 600 °C, they exhibit much better EM wave absorption, where the RCmin decreases to −66.21 dB and EAB increases to 3.69 GHz in X-band. At a high temperature of 600 °C, they also possess excellent and promising EW wave absorption, for which EAB is 3.93 GHz, covering 93.6% range of X-band. In comparison to previous works on graphenes, either the EAB or the RCmin of these nanocomplexes is excellent at high-temperature oxidation. This novel nanomaterial technology may shed light on the downstream applications of graphenes in EM-wave-absorbing devices and smart structures worked in harsh environments.

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Polypyrrole coated Fe3O4 nanoparticles have effectively enhanced the EMI shielding of epoxy nanocomposites compared with the physically mixed nanofillers.

High-temperature stable and metal-free siliconboron carbonitride ceramics with high electromagnetic (EM) wave-absorbing efficiency were achieved through the structural design and pyrolysis of carbon-rich hyperbranched polyborosilazane precursors with pendent phenyl groups. The introduction of benzene rings into the precursors dramatically changes the microstructure and the EM wave-absorbing property of ceramics. It reveals that the ceramics pyrolyzed from the benzene ring-containing preceramic precursors have a higher carbon content and a larger number of sp carbons and generate crystalline carbons (graphitic carbons and tubular carbons) in situ, which lead to excellent EM wave-absorbing properties. The EM wave absorption efficiency and effective absorption bandwidth (EAB, reflection coefficient (RC) below -10 dB) can be tuned via annealing of the ceramics. The ceramics stable at 1320 °C exhibit their optimized EM wave-absorbing performance with a minimum RC (RC) of -71.80 dB and an EAB of 3.65 GHz (8.2-11.85 GHz). We believe that the research extends the design strategy of advanced EM wave-absorbing functional materials, which have great potential as promising absorbers in commercial or military applications.

The microwave absorption materials in the X-band with high-temperature resistance are an important and urgent topic in functional materials. In this article, we present a useful and promising strategy to prepare cobalt-containing microwave absorption ceramics with high-temperature resistance. The polymer-derived ceramics were obtained via pyrolysis of carbon-rich poly(dimethylsilylene)diacetylenes coordinated with octacarbonyldicobalt. XRD and Raman spectra revealed that introduction of cobalt led to in situ formation of cobalt silicide nanocrystals and crystallized carbons (graphitic and tubular carbons), resulting in an enhanced microwave absorption property. The microwave absorption property and bandwidth could be tuned by controlling the cobalt content and annealing temperature of ceramics. When the average real permittivity, imaginary permittivity, and loss tangent of materials increased to 8.06, 3.10, and 0.39, the reflection coefficient (RC) value of as-synthesized ceramics was lower than −10 dB almost across the whole . The minimum RC value of −42.43 dB at 10.55 GHz showed over 99.99% absorption of electromagnetic waves. The highperformance cobalt-containing microwave absorption ceramics possess promising potential in the field of electromagnetic interference protection.

The enhancement of electromagnetic wave absorption at high-temperature as well as oxidation is cutting-edge issue in current electromagnetic functional materials due to the strong demand of stealth aircrafts or aero-engines working in harsh environments. In this contribution, the excellent electromagnetic wave absorption at 1158 K (885 C) with a minimum reflection coefficient (RC min ) of À12.62 dB and a wide effective absorption bandwidth (RC min < -10 dB) of 3.2 GHz was achieved on iron-containing siliconboron carbonitride (SiBCN) monolithic ceramics by using polymer-derived ceramics (PDC) route, setting a new record for EM wave absorption materials at high-temperature. In addition, these materials exhibited desirable mechanical properties and excellent hightemperature resistance until 1400 C in argon atmosphere and 885 C in air atmosphere, respectively. This ingenious strategy is generally benefiting the promotion of EM wave absorption materials with great potential in antenna housings, radomes, areo-engines, and stealth aircrafts in harsh environments.With rapid development of electronic equipments in wireless communication, medical and aerospace fields, electromagnetic (EM) wave transparency, absorption, and shielding are important issues. [1][2][3][4] EM wave absorbing materials are mainly deployed in high-power electronic instruments, satellite communication, radar, stealth ships, and aircrafts, which can eliminate adverse EM waves by converting into thermal energy. However, the stealth aircrafts or aero-engines are working in harsh environments such as high temperature and oxidation, the enhancement of electromagnetic wave absorption and stealth performance at high temperature more than 600 C (873 K) is cutting-edge issue in current electromagnetic functional materials.In this field, metamaterials, ferrites, carbon family materials (carbon black, carbon fibers (CFs), carbon nanotubes (CNTs), graphite flakes, graphene foams, or graphenes), metal-carbon nano-hybrids (Fe 3 O 4 /CNTs/CFs, Fe 3 O 4 /graphene capsules, Co-carbon nanotubes-graphene, Co-Carbon metal-organic framework), core/shell hierarchical nanostructures and dielectronic ceramics, 2D transition metal carbides (MXenes) show favorable EM absorbing performance in ambient environment. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] However, at high temperature more than 873 K (600 C), most of ferrites are limited by low Curie temperature (T c ), for example, 360-440 C for Ba 3 Me 2-Fe 24 O 41 (Me ¼ Co, Cu, Ni) and 570 C for Ni-Zn ferrites. [5] Above T c , the ferrite will be converted to paramagnetic and lose EM wave absorption functionality. For metamaterials, MXenes, and carbon family materials, they always suffer from the thermolysis and oxidation at high temperature more than 600 C (873 K).With resistance to both high temperature and oxidation, silicon carbide (SiC) or silicon nitride (Si 3 N 4 )-based ceramics are important dielectronic type EM wave absorbing materials in harsh environments. The SiC-based materials, including SiC ...

We theoretically study the transmission properties of a stack of metallic metama-terials and show that is able to achieve a perfect transmission selectively exhibiting broadband (Q< 10) or extremely narrowband (Q> 10 5) polarization rotation. We especially highlight how the arrangement of the stacked structure, as well as the metamaterial unit cell geometry, can highly influence the transmission in the spectral domain. For this purpose, we use an extended analytical Jones formalism that allows us to get a rigorous and analytical expression of the transmission. Such versatile structures could find potential applications in polarimetry or in the control of the light polarization for THz waves. a)

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