Design of controlled-morphology NiCo2O4 with tunable and excellent microwave absorption performance

In recent years, the high-performance microwave absorbers with strong loss, broad frequency bandwidth, thin thickness and light weight have been intensively investigated to address the problem of electromagnetic pollution and improve stealth technology. Considering the fact that microwave absorption performance is quite sensitive to morphology, studying NiCo₂O₄ with different morphologies is a valuable step towards developing a high-performance microwave absorber. The different morphologies are prepared by adjusting the addition of the structure-directing agent NH₄F. When the amount of added NH₄F is 1 mmol, a flower-like NiCo₂O₄ morphology (NC–F1) is obtained with a large specific surface area of 158.97 m²/g and pore volume of 0.3525 cm³g^-1, which easily generates conductive loss, polarization loss, and multiple scattering, thereby enhancing its microwave absorption performance. The maximum reflection loss reaches −50.3 dB at 3 mm, and the effective bandwidth is 4 GHz with the matching thickness of 2 mm when the fill ratio is only 30 wt% in the epoxy resin. As the thicknesses range from 1.5 mm to 5 mm, the effective bandwidth is 14.2 GHz (3.8 GHz–18 GHz) and covers the entire C, X, and Ku bands. Therefore, the defined-morphology NiCo₂O₄ is expected to be a novel wide-band and strong-loss microwave absorber.     

Self-supported construction of three-dimensional NiCo2O4 hierarchical nanoneedles for high-performance microwave absorption

Grafting one-dimensional (1D) structure onto three-dimensional (3D) carbon foam is a practical and novel protocol to improve its microwave attenuation capability. Herein, a unique microwave absorber with NiCo₂O₄ nanoneedle grew on carbon foam (NCOCF) has been built via a combined approach of carbonization and hydrothermal treatment. The obtained NCOCF exhibit good impedance matching and excellent attenuation capability, which means that the microwave energy can be dissipated through conductive loss, interfacial polarization and multiple-scattering. These advantages result in the effective transformation of microwave energy to heat, thus yielding a remarkable microwave adsorption (with a thickness of 2.8 mm, the maximum reflection loss (RL_max) is −63.6 dB, and the effective absorption bandwidth (E_AB) is as wide as 4.72 GHz with a thickness of 1.3 mm). The study would offer a strategy for development of the high-performance microwave absorber.     

Glycine-assisted solution combustion synthesis of NiCo2O4 electromagnetic wave absorber with wide absorption bandwidth

Design of high-performance electromagnetic (EM) wave absorbing materials has been regarded as an effective solution to excessive EM wave interference problem. As a promising candidate, NiCo₂O₄ absorbers have attracted enormous research attentions. However, currently reported morphology-manipulation synthetic methods of NiCo₂O₄ absorbers are time-consuming and require high energy consumption, which inhibit their practical applications. Herein, a more facile and cost-effective solution combustion synthesis was utilized to fabricate NiCo₂O₄ materials. The absorber prepared by using glycine as fuel displayed the best EM wave absorption performance. Impressively, ultra wide absorption bandwidth of 7.44 GHz from 10.56 GHz to 18 GHz could be achieved with relatively thin thickness of 2.1 mm NiCo₂O₄ sample fabricated in this work displayed the widest effective absorption bandwidth (EAB) among reported NiCo₂O₄-based EM wave absorbing materials so far. In view of its simple and low-cost synthetic process and excellent EM wave dissipation capacity, NiCo₂O₄ samples in this work showed great feasibility as practical absorber. In addition, our findings may also provide new sight for facile preparation of other high-performance EM wave absorbers by solution combustion synthesis instead of complex morphology-manipulation routes.     

Modulation of MoSe2 & MnFe2O4@MnO2 nano-architectures for microwave absorption properties via single- and bilayer method

The electromagnetic pollution problem, particularly at microwave frequencies, poses a threat to not only sensitive technological gadgets but also to the health of humans. Therefore, there is a great need for lightweight and highly effective microwave-absorbing materials (MAMs). Here, we fabricated a hierarchical flower-like MoSe₂ structure and a rod-like MnFe₂O₄@MnO₂ architecture via a solvothermal method. Single-layer and bilayer samples were fabricated to study the microwave absorption feature. In single-layer samples, the flower-like MoSe₂ structure has better microwave absorption properties than the rod-like MnFe₂O₄@MnO₂ architecture. And in bilayer absorbing samples, a sample with a flower-like MoSe₂ structure as the top layer shows high absorption performance. Moreover, in bilayer samples, changes were made to the thickness of both layers to find the best parameters. An optimal bilayer sample has been achieved with a flower-like dielectric MoSe₂ structure as a top layer having a 1 mm thickness and magnetic MnFe₂O₄@MnO₂ as a bottom layer also with a 1 mm thickness; indicating that a strong absorption can only be attained by balancing dielectric loss and magnetic loss. Moreover, the optimal sample shows decent absorption with an effective absorption bandwidth (EAB) of 5.4 GHz (14.7–9.3 GHz) with a 1 mm thickness of each layer. The simulated results of the optimal sample have also been compared with experimental results. These results suggest a different approach for developing MAMs in the future.     

Hydrothermal solvothermal synthesis and microwave absorbing study of MCo2O4 (M = Mn,Ni) microparticles

ABSTRACT

MCo₂O₄ (M?=?Mn,Ni) microparticles were synthesised by a simple hydrothermal solvothermal method. The samples were characterised by X-ray diffraction, X-ray energy dispersive spectroscopy and scanning electron microscopy, which showed that MnCo₂O₄ microparticles with spherical particles aggregated by a large number of small cubes and cubic shaped NiCo₂O₄ microcubes were obtained. The microwave absorption properties of these products were systematically investigated by vector network analysis. Results indicated that the minimum reflection loss value of MnCo₂O₄ microparticles was ?26.34?dB at 11.04?GHz with the absorber thickness of 2.5?mm, which was much lower than that of NiCo₂O₄ microcubes with the same absorber thickness. The possible mechanism was analysed, indicating that the geometry and size of MCo₂O₄ (M?=?Mn,Ni) microparticles played a key role in microwave absorption.     

Design of double-layer ceramic absorbers for microwave heating

We propose a guide for designing double-layer ceramic absorbers in microwave heating by optimizing the thickness based on the analysis of reflection loss (RL) of a double-layer absorber consisting of a high-loss SiC layer and a low-loss Al₂O₃ layer. The calculated reflection losses for individual layers of SiC and Al₂O₃ show that the former with a thickness of 0.0054 m has the maximum microwave absorption while the latter in the thickness range up to 0.1 m is identified as a poor microwave absorbing material with RL larger than −0.4 dB. By using a 0.0054-m-thick SiC layer as the susceptor, the absorption in the Al₂O₃ layer and of the entire double-layer absorber increases significantly. The results demonstrate that high microwave absorption throughout the heating process can only be achieved in a sample with a small thickness in which a slight absorption peak shift during heating (less than one eighth-wavelength in the medium) occurs.     

Efficient single and bi-layer absorbers of CaTiO3 micro-cubes and polypyrrole nanotubes composites for enhanced microwave absorption in X and Ku band

The present study is focused on the investigation of the absorption properties of the bi-layer absorber with different thickness and orientation approaches. Improvement in absorption exclusively depends on the various parameters as interfacial polarization, multiple reflections among layers, conduction loss, phase cancellations, and shape anisotropy, etc. By considering these parameters. Calcium titanate micro-cubes CaTiO3 (CTO) and polypyrrole nanotubes (PPy) nanocomposites were prepared and microwave absorption from single layer coaxial absorbers having M1 = CaTiO₃+15 wt% polymer and M2 = CaTiO₃+30 wt% polymer were determined. Different layer orientations and thicknesses of the bi-layer absorber were optimized by CST software. FESEM, XRD, VSM, and VNA were used to find out the microstructural, phase, morphology, magnetic, and absorptions properties in microwave region. The values of the RL from M1 and M2 are ?24 dB and ?32 dB for 2.5 mm thickness. However, the RL response absorber with 2 mm thickness shows ?19 dB and ?11 dB. The bi-layer absorber with M1 and M2 having 0.5/0.5 mm (lower/upper) arrangement layer depicted minimum loss in Ku band. It is expected that CTO/PPy absorbers are versatile absorbers for Ku and X band purposes.     

Effect of filler loading and thickness parameters on the microwave absorption characteristic of double-layered absorber based on MWCNT/BaTiO3/pitted carbonyl iron composite

In this work, single- and double-layer electromagnetic wave absorbers were prepared by as-prepared MWCNTs/BaTiO₃/pitted carbonyl iron composites. MWCNT/BaTiO₃ (MW/BTO) was prepared via sol-gel method whereas the carbonyl iron particles (CI) were corroded via pitting corrosion method. The structural, microstructural, magnetic and microwave absorption properties of the composites were evaluated via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) methods. CST studio software was employed to simulate the microwave absorption characteristics of double-layer absorbers. Moreover, the effects of changing matching and absorbing layer thickness (3 mm in total) and filler loading (10, 20 and 30 wt%) of the as-prepared composite on the microwave absorption properties were investigated. According to the results, maximum RL value for single layer absorber with 20 wt% filler loading can reach ?11.5 dB at 9.7 GHz with 3 mm thickness and 0.4 GHz bandwidth. In contrast, double-layered absorber using 10 wt% of the composite in the upper layer (as matching layer) and 30 wt% of the composite in lower layer (as absorbing layer) can increase the reflection loss and absorption bandwidth values to ?15.5 dB and 1 GHz respectively. Improving in absorption characteristics can be attributed to coupling interactions, impedance matching and multiple scattering. The main advantages of the prepared double layer absorber than single layer absorber are tuning the intensity and effective absorption bandwidth by adjusting the layer order, thickness and filler loading of each layer which shown good potential for practical application.     

Multi-interface-induced by regulating nanocomposite morphology and absorber design to achieve wideband electromagnetic wave absorber

The current study describes the fabrication of a bilayer microwave absorber made of magnetic Sr₂FeReO₆ (SRO) powder and a magnetoelectric nanocomposite formed of rod-like magnetic Sr₂FeReO₆ powder wrapped in polygonal SnS₂ powder (SRSS), which was then annealed and analyzed. The analysis of phase constituents, as well as morphological and magnetic measurements, revealed that rod and polygonal particles with soft magnetic properties were successfully synthesized. Additionally, our findings showed that 30:70 wt ratio nanocomposite powders were unable to exhibit broad X-band frequency absorption capabilities. Due to the bi-layer absorber's rational design, the reflection loss was found to be increased and reached -33 dB at 10.3 GHz by covering practically the whole X-band frequency with only 2.5 mm of thickness. The prepared absorber's optimum design included SRSS nanocomposite powder as an absorbing layer with a 1.5 mm thickness and SnS₂ powder as a matching layer. The exceptional electromagnetic wave dissipation performance of bi-layer samples compared to single-layer absorber samples may be the result of multiple interfaces being formed as a result of controlling component morphology and composition as well as the absorber's design, which enhanced critical absorbing factors like various polarization phenomena and relaxation losses. The research presented here suggests a simple method for enhancing microwave dissipation performance with a broad absorption band based on the development of heterojunction structures and the integration of various loss processes.     

Tunable magnetic coupling and dipole polarization of core-shell Magnéli Ti4O7 ceramic/magnetic metal possessing broadband microwave absorption properties

There are few reports on the application of Magnéli Ti₄O₇ in the field of electromagnetic wave absorption. Herein, we designed and prepared a Ti₄O₇/magnetic metal composite via an electrostatic assembly with in-situ reduction reaction. This system utilized distinct magnetic coupling deriving from the subtle designed structures and magnetic-dielectric synergy. The core-shell magnetic metallic nanoparticles/oxygen deficient Ti₄O₇ are useful microwave absorbers in terms of wide broadband, strong absorption and ultra-low filler amount. The optimal reflection loss of Ti₄O₇@CoNi composite was −43.6 dB at 2.5 mm, meanwhile the effective absorbing band could reach over 5.12 GHz at only a 2.7 mm thickness. The results confirm that the dependence of the electromagnetic characteristics of the absorber on the filler ratio, frequency, and absorber thickness. Therefore, this work may be beneficial in constructing core-shell structured magnetic metal/Magnéli Ti₄O₇ composites to tune electromagnetic parameters and strengthen electromagnetic absorption.     

Composition tunable manganese-doped magnetite microwave absorber composites for radio frequency identification communication

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 (Mn_XFe_3?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 Mn_XFe_3?XO₄ nanoparticles are investigated. The saturation magnetization and dielectric and magnetic losses of Mn_XFe_3?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 Mn_XFe_3?XO₄ nanoparticles can be a potential candidate for the application of microwave absorber in wireless communication and electronic industries.     

Design of hierarchical core-shell ZnFe2O4@MnO2@RGO composite with heterogeneous interfaces for enhanced microwave absorption

In order to overcome the problems caused by electromagnetic pollution, the design and development of high-performance microwave absorbers is urgently required. In this work, a hierarchical ZnFe₂O₄@MnO₂@RGO composite was successfully fabricated via a facile and rapid hydrothermal method. Its unique core-shell structure and synergistic effect between multiple components are beneficial for electromagnetic wave absorption. The morphology, elemental composition, microstructure and microwave absorption characteristics were systematically studied. With a filler loading of 20 wt%, the composite presents a minimum reflection loss (R_Lmin) of ?46.7 dB and an effective absorption bandwidth (EAB) as wide as 5.2 GHz at a thickness of 2.5 mm. The superior absorption ability profits from a special microstructure, good impedance matching, multiple attenuation features, interfacial polarization, and the synergistic effect of dielectric and magnetic loss. Consequently, this work lays a foundation for the design of high-performance electromagnetic wave absorbers with multicomponent heterogeneous structures.     

Comparative study of microwave absorption properties of Ni–Zn ferrites obtained from different synthesis technologies

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, Ni_0·5Zn_0·5Fe₂O₄ 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 (RL_min) 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.     

Single and double-layered Tri-band Microwave absorbing materials

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.     

Fabrication and microwave absorbing property of WO3@WC with a core-shell porous structure

Special microstructure can significantly improve the microwave absorption property of rare materials. In this paper, porous WC powders were successfully synthesized by spray granulation method. Then, WO₃@WC materials with core-shell porous structure can be prepared after 410 °C heating treatment at different time to form the outer WO₃ oxidation layer. In addition, the microstructure, morphology, phase analysis and electromagnetic property were fully studied by investigating the WC-based materials in different structures. For WO₃@WC core-shell porous materials, when the coating thickness was 2.1 mm, the maximum reflection loss can reach ?19.4 dB at 12.6 GHz, which shows quite good microwave absorbing effects. The core-shell porous structure enhances the original microwave absorption performance due to the multiple reflection reflections and polarizations.     

Enhanced structural,electromagnetic and absorption features of CoSm ferrite-metamaterial absorbers through synergistic effects

Currently, materials with outstanding absorption abilities, such as thin size, better absorbing power, and light weight are the need of industry to resolve the electromagnetic issues. However, the research on optimizing the composition of the material, microstructure and the structure of the absorber are also the important factors for enhancing the absorption features. A metamaterial microwave absorber (MMA) based on nano ferrites with desirable absorption peaks is proposed and simulated. Sol-gel auto combustion route is used to prepare the nanosized Sm doped Co ferrite with Co_1+xSm_xFe_2-2xO₄ at x = 0.00, 0.03, 0.06, 0.09, respectively. XRD, VSM, FESEM, and VNA were employed to evaluate the structural, magnetic, morphological, and dielectric features. Rietveld refinement of the XRD patterns of samples was evaluated. Refined parameters show the spinel phase's emergence and the Fe₂O₃ phase. Grain size and crystallite size were increased with Sm doping in Co ferrite. Electromagnetic studies depicted that the highest dielectric constant value was found at x = 0.09 and the minimum value at x = 0.03, respectively. Sm doped Co ferrite at x = 0.09 depicted high Q values at higher frequencies. The coercivity values first decreased and then increased. All samples exhibit variations in coercivity and magneto-crystalline anisotropy constant. This variation was attributed to the super-exchange interactions and strong LS coupling of the cations. The multiple absorption peaks are attained for TE-polarization, and the absorptivity is considerably improved for x = 0.09. The proposed absorber simulated from CST depicted the absorption peaks of the S-band and C-band of the microwave regime. The synergistic effects among the metamaterial and ferrite layers may enhance the absorption feature and would be useful for satellite communication applications.     

Hydrothermally synthesized microrods and microballs of NiCo2O4 for supercapacitor application

The microrods and microballs of NiCo₂O₄ are successfully synthesized by the hydrothermal method. The effect of ammonium hydroxide and ammonium fluoride on the surface microstructure is observed. The prepared microrods and microballs of NiCo₂O₄ are analyzed by various analytical tools like powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), with energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties are studied by using cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS), using the workstation Biologic SP-200. The maximum specific capacitance of the NiCo₂O₄ microrods electrode is 1671 F/g. The areal specific capacitance of the NiCo₂O₄ microrods electrode is 284 mF/g. The energy density and power density of microrods of NiCo₂O₄ electrode are 19 Wh/Kg and 282 W/kg, respectively. The equivalent series resistance (Rs) is 0.62 Ω for NiCo₂O₄ microrods.     

Preparation of scale-like nickel cobaltite nanosheets assembled on nitrogen-doped reduced graphene oxide for high-performance supercapacitors

Ultrathin scale-like nickel cobaltite (NiCo₂O₄) nanosheets supported on nitrogen-doped reduced graphene oxide (N-rGO) are successfully synthesized through a facile co-precipitation of Ni²⁺ and Co²⁺ in the presence of sodium citrate and hexamethylenetetramine and subsequent calcination treatment. The composition and morphology of NiCo₂O₄ nanosheets@nitrogen-doped reduced graphene oxide (denoted as NiCo₂O₄ NSs@N-rGO) were characterized by Scanning electron microscope, Transmission electron microscope, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller and thermogravimetric analysis. The thickness of NiCo₂O₄ nanosheets anchored on the reduced graphene oxide is around 4 nm. The capacitance of NiCo₂O₄ NSs@N-rGO is evaluated by cyclic voltammogram and galvanostatic charge/discharge with the result that the NiCo₂O₄ NSs@N-rGO could deliver a specific capacitance of 1540 F g⁻¹ after 1000 cycles at 10 A g⁻¹.     

Extended effective absorption bandwidth of Sendust/phosphate flaky particles by TiO2 insulation coating

How to obtain a wide effective absorption bandwidth is still a challenge for Sendust micro-powder as microwave absorber at 2–10 GHz range. Double shell-core structured composites are desirable to extend effective absorption bandwidth through optimizing impedance match degree in wider frequency and forming a broad dielectric loss peak. In this work, TiO₂ layer is fabricated on surface of flaky Sendust/phosphate composites through the hydrolysis reaction for constructing double shell-core structured TiO₂@phosphate@Sendust flaky composites. The synergistic effect of TiO₂-phosphate interface and phosphate-Sendust interface induces a broad peak for dielectric loss, microwave absorption ratio and attenuation constant, resulting in wider effective absorption bandwidth of 3.2 GHz compared with that (2.4 GHz) of raw Sendust/phosphate composites. This work offers a facile and effective strategy for extending effective absorption bandwidth of micron-scale microwave absorber.     

Fabrication of novel silicon carbide-based nanomaterials with unique hydrophobicity and microwave absorption property

Novel SiC-based nanomaterials, namely the nitrogen and aluminum co-doped SiC@SiO₂ core-shell nanowires and nitrogen-doped SiO₂/Al₂O₃ nanoparticles, have been fabricated through a facile thermal treatment process based on the chemical vapor deposition and vapor-liquid reaction. These nanomaterials show remarkable hydrophobicity with a water contact angle (CA) over 140°, which are aroused by the surface zigzag morphology of the nanostructures and the hydrocarbyl groups generated during the preparation process. Moreover the nanocomposites also exhibit relatively prominent microwave absorption (MA) properties in the frequency range of 2.0-18.0 GHz. The minimum reflection loss (RL) value as low as −23.68 dB can be observed at 14.16 GHz when the absorber thickness is 2.6 mm with a loading rate of 16.7 wt%. And the nanocomposites-based absorbent can achieve an effective absorption bandwidth (RL < −10 dB) of 4.48 GHz with the absorbent thickness of 2.5 mm. This enhanced microwave attenuation performance can be attributed to multiple polarizations and perfect impedance matching conditions, as well as multiple internal reflections. These marvelous properties make these N and Al co-doped SiC@SiO₂ core-shell nanowires and N-doped SiO₂/Al₂O₃ nanoparticles display extensive application potential as MA materials in harsh environment.