Adjustable iron-containing SiBCN ceramics with high-temperature microwave absorption and anti-oxidation properties

Quaternary siliconboron carbonitride (SiBCN) ceramics show excellent high-temperature stability and oxidation resistance, indicating great potential as high-temperature electromagnetic (EM) wave absorbing materials. In this contribution, an efficient and facile method was developed to prepare bulk iron-containing SiBCN (Fe–SiBCN) ceramics with remarkable EM wave absorption at high temperature by pyrolyzing boron and iron containing precursors (PSZV-B–Fe). The introduction of boron and iron not only improves the high-temperature stability but also influences the complex permittivity and EM wave absorption. The minimum reflection coefficient (RC_min) is −61.05 dB, and the effective bandwidth absorption (EAB) is 3.35 GHz (9.05–12.4 GHz). The RC_min will be decreased to −52.3 dB at 600°C as well as the EAB covers more than 67% of the X band (2.8 GHz). The high-temperature stable Fe–SiBCN ceramics with adjustable dielectric properties can be utilized as high-performance EM wave-absorbing materials in high-temperature and harsh environments.     

The heterointerface of graphene in-situ growth for enhanced microwave attenuation properties in La-doped SiBCN ceramics

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 (RL_min) 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 RL_min 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.     

Advanced Ti3C2Tx MXene-modified cement nanocomposites toward high efficiency electromagnetic functional materials for green buildings

The proliferation of electronic devices and wireless communication is leading to serious electromagnetic (EM) interference. In this work, Ti₃C₂/cement composites were developed as high efficiency EM functional materials by introducing exfoliated Ti₃C₂T_x MXene with cement for green buildings with EM shielding function. In the composites, few-layered Ti₃C₂ MXene were dispersed homogeneously throughout the cement matrix. The EM properties of the composites were studied as a function of the MXene content. With increasing MXene content, real and imaginary part of permittivity was significantly improved owing to the polarization and electrical conduction caused by the MXene phase. Composites with 15 wt.% MXene showed good EM absorbing properties with a maximum effective absorbing bandwidth of 2.67 GHz. Strong EM shielding can be achieved when MXene content increased to 25 wt.%. The EM shielding effectiveness of such composites was higher than 22.0 dB, and the dominating shielding mechanism was EM absorption. This work finds new materials for the development of advanced green buildings with EM shielding function.     

Lightweight and resilient SiOC/SiC foam with efficient electromagnetic wave absorption and high-temperature stability

Integrating multiple functions such as high electromagnetic (EM) wave absorption, thermal insulation, and resilience into one material is critical, especially for applications in harsh environment. SiC ceramic has received considerable attention as high-temperature wave absorber, but its applications are limited by common wave absorption performance and brittleness of ceramics. Here by incorporating SiO₂ with SiC in a unique three-dimensional network structure, SiOC/SiC foam consisting of abundant SiOC thin flakes interconnected by numerous long interweaving SiC nanowires have been prepared. The foam shows high EM wave absorption with minimum reflection loss of −30.23 dB, broad effective absorption bandwidth of 5.4 GHz, and a nearly complete compressive resilience from 10% strain. Besides, the foam displays high-temperature resistance up to 1400°C in air and good thermal insulation performance. Such multifunctional material is promising for applications in advanced aerospace industry under extreme conditions.     

Microstructure and electromagnetic wave absorption property of reduced graphene oxide-SiCnw/SiBCN composite ceramics

In this account, RGO-SiC_nw/SiBCN composite ceramics were fabricated using polymer derived ceramic (PDC) combined with chemical vapor infiltration (CVI) technology. Dielectric property of as-obtained RGO-SiC_nw/SiBCN composite ceramics was significantly enhanced thanks to established conductive pathway through overlapped nanoscale SiC_nw and micro-sized RGO. The minimum RC of composite ceramics with 0.5 wt% GO and 2.29 wt% SiC_nw at thickness of 3.6 mm reached -42.02 dB with corresponding effective absorption bandwidth (EAB) of 4.2 GHz. As temperature rose from 25 to 400 °C, permittivity increased with enhanced charge carrier density and then it decreased due to oxidation process of RGO from 400 to 600 °C. The minimum reflection coefficient (RC) was recorded as -39.13 dB and EAB covered the entire X-band at 600 °C. EMW absorption ability was evaluated after high-temperature oxidation experiment under protective effect of wave-transparent Si₃N₄ coating. RGO-SiC_nw/SiBCN composite ceramics maintained outstanding EMW absorption ability with minimum RC of -10.41 dB after oxidation at 900 °C, indicating RGO-SiC_nw/SiBCN composite ceramics with excellent EMW absorption characteristic even at high temperatures and harsh environments.     

Nano-SiC-decorated Y2Si2O7 ceramic for enhancing electromagnetic waves absorption performance

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 (RL_min) 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.     

Fabrication of urchin-like ZnO-MXene nanocomposites for high-performance electromagnetic absorption

The recently developed two-dimensional transition metal carbides (such as MXene) have shown amazing electrical properties. MXene and derivative two dimensional (2D) materials are widely used in electron devices, and have large potential application in electromagnetic (EM) absorber. Herein we describe a mild method to prepare an urchin-like ZnO-MXene Ti₃C₂T_x nanocomposite through a coprecipitation process. The nanocomposite delivers a substantially enhanced EM absorbing performance with an optimum reflection loss of −26.30 dB, which is significantly better than that of primitive Ti₃C₂T_x (−6.70 dB), owing to the construction of unique semiconductive networks and larger interfaces. The EM absorption performance can be effectively controlled in the range of 14.0–18.0 bands by changing the growth time of ZnO. Considering the large amount of members in MXene, this study demonstrates a new strategy applicable in maximizing their applications in EM absorbing materials.     

Effect of SiBCN content on the dielectric and EMW absorbing properties of SiBCN-Si3N4 composite ceramics

Siliconboron carbonitride ceramics (SiBCN) were introduced into porous Si₃N₄ substrates via low pressure chemical vapor deposition and infiltration from SiCl₃CH₃-NH₃-BCl₃-H₂-Ar system. To improve the electromagnetic wave(EMW) absorbing properties, the molar ratio, n_CH3SiCl3/(n_NH3 + n_BCl3), was increased based on thermodynamics analysis. The results show that nanosized silicon carbide crystals and free carbon dispersed uniformly in the amorphous SiBCN phase, resulting in suitable dielectric properties and improved absorption capabilities of SiBCN-Si₃N₄ ceramics. Additionally, with increasing SiBCN ceramics loading, the amount of nanocrystals and interface between nanocrystals and amorphous SiBCN phase increased, leading to enhanced polarization and dielectric loss of the composite ceramics. When SiBCN content was up to 3.64 wt%, the electromagnetic reflection coefficient (RC) of SiBCN-Si₃N₄ composite ceramics reached ?40 dB (>99.97% absorbing) with the effective electromagnetic absorbing bandwidth of 3.64 GHz in the X-band. This study makes it possible to fabricate SiBCN-based composite materials with excellent EMW absorbing properties at a low temperature.     

Synthesis,microstructure and electromagnetic properties of Hf-based SiBCN ceramics

In this work, two kinds of ceramic polymers, polyborosilazane and polyhafnoxane, were mixed by a precursor blending method, followed by curing and pyrolysis to obtain Hf-based SiBCN ceramics. Through FTIR and NMR characterization of cured product, it can be found that the two precursors underwent cross-linking reaction during the curing process, resulting in the increase of crystallization temperature of HfO₂ and β-SiC, and the formation of new components (HfB₂ and HfN) during pyrolysis. When the pyrolysis temperature increases, the average values of the real part and imaginary part of the dielectric constant of Hf-based SiBCN ceramics increased from 7.2 to 4.9 to 9.0 and 6.6, respectively, resulting from the precipitation of HfB₂ and HfC(N) with high dielectric constants. The effective absorption width decreased from 3.4 to 2.5 GHz, and the minimum value of reflection coefficient increased from −14.9 to −12.2 dB, which is caused by poor impedance matching. After being oxidized at 500 °C for 50 h in air, the free carbon basically disappears, and the full X-band absorption can be realized for the Hf-based SiBCN ceramic pyrolyzed at 1500 °C with a thickness of 2.8 mm.     

Electromagnetic wave absorbing properties of Cr2AlB2 powders and the effect of high-temperature oxidation

The electromagnetic (EM) wave absorbing properties of Cr₂AlB₂ powders and those after high-temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr₂AlB₂ with good absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth (E_AB) is 4.4 GHz (13.0-17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding E_AB values, respectively, are 3.8 GHz (13.6-17.4 GHz, 1.7 mm), 4.1 GHz (13.5-17.6 GHz, 1.6 mm), and 4.4 GHz (13.0-17.4 GHz, 1.7 mm). With an absorber thickness of 1.5-4.0 mm, the E_AB with a RL value of less than −10 dB can be tuned in a broad-frequency range 5.0-18.0 GHz, which basically covers C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) bands. These results demonstrate that Cr₂AlB₂, as a high-efficient and oxidation-resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high-temperature oxidation.     

Effect of boron content on the microstructure and electromagnetic properties of SiBCN ceramics

Electromagnetic wave (EMW) absorbing materials have excellent potential for various applications in civil engineering and the military. In this study, siliconboron carbonitride (SiBCN) ceramics with excellent EMW absorption capability and oxidation resistance were obtained by adjusting the boron content. The results revealed that the graphite crystallite size in the SiBCN ceramics increased from 3.42 to 3.78 nm, whereas the thickness of the oxide layer decreased from 16.6 to 8.2 μm. The highest electrical conductivity and permittivity for the SiBCN ceramics were obtained when the boron content was 5%. The minimum reflection loss was ?35.25 dB at 10.57 GHz and a ceramic thickness of 2.0 mm. At a temperature of 600 °C, the SiBCN ceramic exhibited excellent EMW attenuation ability; particularly, the minimum reflection loss reached ?29.18 dB at 9.65 GHz and a ceramic thickness of 2.5 mm. The superior EMW absorption properties of the SiBCN ceramics at high temperatures can be ascribed to the synergistic effect of relaxation and conductivity. The results suggest that boron could enhance the transformation of amorphous carbon into crystalline graphite and increase the number of heterointerfaces and conductive paths. This work provides a method for obtaining SiBCN ceramics with excellent EMW absorption properties.     

Enhanced electromagnetic wave absorption of Fe-doped silicon oxycarbide nanocomposites

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.     

Dielectric response and electromagnetic wave absorption of novel macroporous short carbon fibers/mullite composites

For wider-band and stronger electromagnetic (EM) wave absorption, macroporous short carbon fibers/mullite matrix (C_f/Mu) composites were prepared via introducing short carbon fibers (0, 0.7, and 1.3 vol%) with length of 2-3 mm into macroporous mullite ceramic by gel-casting. The density of as-prepared C_f/Mu composites decreases from 2.93 g/cm³ to 2.74 g/cm³, while the porosity increases from 3.32% to 10.76% with the rise in carbon fibers content. The diameter of macropores in C_f/Mu composites is ranging from several microns to tens of microns. Complex permittivity and dielectric loss of the prepared composites in X-band (8.2-12.4 GHz) are significantly enhanced with increased carbon fibers content. The best EM wave absorption performance is obtained in the macroporous C_f/Mu composites containing only 0.7 vol% carbon fibers (C_f/Mu-0.7). The maximum absorption loss of C_f/Mu-0.7 is −38.3 dB at 12.08 GHz at the thickness of 2.1 mm, and effective absorption bandwidth below −10 dB (over 90% of EM wave absorption) covers the whole X band with the thickness of 2.35 mm. The results suggest that the C_f/Mu composites can be promising high-performance EM wave absorbing materials.     

Enhanced electromagnetic microwave absorption properties of SiCN(Fe) ceramics produced by additive manufacturing via in-situ reaction of ferrocene

SiCN(Fe) ceramics with excellent electromagnetic wave (EMW) absorption performance were successfully prepared from a preceramic polymer doped with ferrocene. Additive manufacturing (Digital Light Processing), providing enhanced structural design ability, was employed to fabricate samples with complex architectures. During pyrolysis, ferrocene catalyzed the in-situ formation of a large amount of turbostratic carbon, graphite and SiC nanosized phases, which formed carrier channels in the electromagnetic field and increased the conductivity loss. Meanwhile, it also increased the dipole polarization, interface polarization and the dielectric properties of the material, which finally enhanced the EMW absorption capacity of SiCN(Fe) ceramics. When containing 0.5 wt% ferrocene, the material showed good performance with EAB 4.57 GHz at 1.30 mm, and RL_min −61.34 dB at 2.22 mm. The RL_min of 3D-SiCN-0.5 ceramics was −6 dB, and the RL of the X-band was lower than −4 dB at 2 mm.     

Construction of multiple heterogeneous interface and its effect on microwave absorption of SiBCN ceramics

Iron-containing siliconboron carbonitride (SiBCN) ceramics with multiple heterogeneous interfaces were fabricated using the microstructural design and polymer-derived ceramics (PDC) approach. The characterization results revealed the in-situ generation of nanocrystals, including graphite, belt-like silicon nitride (Si₃N₄), and silicon carbide (SiC) whiskers, in amorphous SiBCN matrix after annealing. At the same time, these dielectric lossy phases successfully constructed multiple heterogeneous interfaces and three-dimensional network structures. Consequently, the conductivity of the ceramics increased from 4.49 × 10⁻⁹ (annealed at 800 °C) to 0.67 × 10⁻⁴ S cm⁻¹ (annealed at 1600 °C). The real part of permittivity improved from 4.57–3.36 (annealed at 800 °C) to 10.90–8.38 (annealed at 1600 °C) in the frequency range of 2–18 GHz. The formation of multiple heterogeneous interfaces caused interfacial polarization and increased the multiple relaxations, which ultimately led to a superior microwave absorption property with a minimum reflection loss (RL_min) of −34.28 dB and an effective absorption bandwidth (EAB) of 3.76 GHz (8.64–12.4 GHz).     

Polymer-derived Co2Si@SiC/C/SiOC/SiO2/Co3O4 nanoparticles: Microstructural evolution and enhanced EM absorbing properties

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 (RC_min) −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.     

Impedance matching optimization of SiCf/Si3N4–SiOC composites for excellent microwave absorption properties

SiC fiber reinforced ceramic matrix composites (SiC_f-CMCs) are considered to be one of the most promising materials in the electromagnetic (EM) stealth of aero-engines, which is expected to achieve strong absorption and broad-band performance. Multiscale structural design was applied to SiC_f/Si₃N₄–SiOC composites by construction of micro/nanoscale heterogeneous interfaces and macro double-layer impedance matching structure. SiC_f/Si₃N₄–SiOC composites were fabricated by using SiC fibers with different conductivities and SiOC–Si₃N₄ matrices with gradient impedance structures to improve impedance matching effectively. Owing to its unique structure, SiC_f/Si₃N₄–SiOC composites (A3-composites) achieved excellent EM wave absorption performance with a minimum reflection coefficient (RC_min) of ?25.1 dB at 2.45 mm and an effective absorption bandwidth (EAB) of 4.0 GHz at 2.85 mm in X-band. Moreover, double-layer SiC_f/Si₃N₄–SiOC with an improved impedance matching structure obtained an RC_min of ?56.9 dB and an EAB of 4.2 GHz at 3.00 mm, which means it can absorb more than 90% of the EM waves in the whole X-band. The RC is less than ?8 dB at 2.6–2.8 mm from RT to 600 °C in the whole X-band, displaying excellent high-temperature absorption performance. The results provide a new design opinion for broad-band EM absorbing SiC_f-CMCs at high temperatures.     

Construction of Si3N4/SiO2/SiC–Y2Si2O7 composite ceramics with gradual impedance matching structure for high-temperature electromagnetic wave absorption

Good impedance matching is vital in upgrading the performance of electromagnetic (EM) wave-absorbing materials. In this study, Si₃N₄/SiO₂/SiC–Y₂Si₂O₇ composite ceramics were synthesized by sintering and chemical vapor infiltration (CVI) technology with gradual impedance matching. The relationship between the microstructure of the as-prepared composite ceramics and EM wave absorption characteristics was thoroughly explored. It was found that the amorphous Si₃N₄, SiO₂, and SiC layers were constructed with a gradual impedance matching structure, which not only improved impedance matching but also increased the number of nano interfaces. More importantly, SiC nanocrystals effectively increased the conduction loss, and the presence of defects and nanoscale heterogeneous interfaces further increased the polarization loss. Consequently, the as-prepared composite ceramics displayed enhanced EM wave absorption properties, with a minimum reflection coefficient (RC_min) value of less than ?20 dB over a temperature range of 25 °C (RT)-300 °C, and an effective absorption bandwidth (EAB) maintained at 4.2 GHz with the thickness range of 3.75–4.75 mm. These results demonstrated the practical significance of high-performance EM wave absorption materials that can be applied in high-temperature and water vapor environments.     

Polymer-derived Co2Si(Co)/SiCN composite ceramics with tunable microwave absorption properties

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.     

Electromagnetic wave absorbing performance of multiphase (SiC/HfC/C)/SiO2 nanocomposites with an unique microstructure

Dielectric properties and electromagnetic (EM) wave absorbing performance of monolithic (SiC/HfC/C)/SiO₂ nanocomposites (denoted as SHCOs) have been investigated in the X-band (8.2–12.4 GHz). The multiphase SHCOs are composed of insulating SiO₂ and SiC/HfC/C nanocomposite fillers (SHC), which fillers composed of semiconducting β-SiC, conductive HfC-Carbon core-shell nanoparticles, and interconnected carbon nanoribbons. Dielectric response indicates that the increased SHC content results in an enhanced imaginary part of the permittivity and dielectric loss, leading to an improved EM absorbing performance. The unique microstructure with an EM wave-transparent SiO₂ matrix is favorable for impedance matching and effective EM wave propagation. The enhanced interface polarization and conduction loss are considered as the key mechanisms for EM wave attenuation. The minimum reflection loss of the SHCOs achieves – 60.7 dB containing 20 vol% of SHC (at 9.98 GHz) with the sample thickness of 3.33 mm, and the effective absorbing bandwidth (EAB) covers ca. 72 % of the X-band. The monolithic (SiC/HfC/C)/SiO₂ nanocomposites with outstanding EM wave absorbing performance are promising candidates for EM application at high temperatures.