Ultrathin MoS2 Nanosheets Encapsulated in Hollow Carbon Spheres: A Case of a Dielectric Absorber with Optimized Impedance for Efficient Microwave Absorption

Advances in Carbon Microsphere-Based Nanomaterials for Efficient Electromagnetic Wave Absorption

Carbon microspheres have indeed shown great promise as effective materials for absorbing electromagnetic waves, particularly in microwave applications. Their unique properties, such as high surface area, porosity, and electronic characteristics, make them ideal candidates for addressing the growing concerns around electromagnetic pollution from electronic devices. By leveraging the properties of these materials, we can work toward creating more efficient and sustainable electromagnetic wave absorption technologies. Recent efforts have focused on synthesizing and investigating carbon microsphere-based electromagnetic wave-absorbing nanomaterials with the ambition of achieving the desired attributes of being thin, light, wide, and robust. This Review first delves into the detailed mechanism of electromagnetic wave absorption, followed by an elucidation of the preparation methods for carbon microsphere-based nanomaterials. Furthermore, it systematically outlines the common methods and strategies employed to improve the microwave absorption capabilities of carbon microspheres, including chemical vapor deposition, emulsion polymerization, hydrothermal methods, and template methods. Lastly, it outlines the challenges encountered by carbon microsphere-based electromagnetic wave absorption nanomaterials and outlines their prospects, mainly morphology change, component hybridization, and elemental doping. This Review aims to provide valuable insights into the creation of carbon microsphere nanomaterials with excellent electromagnetic wave absorption properties.

Multidimensional Engineering Induced Interfacial Polarization by in-Situ Confined Growth of MoS2 Nanosheets for Enhanced Microwave Absorption

Interface design has enormous potential for the enhancement of interfacial polarization and microwave absorption properties. However, the construction of interfaces is always limited in components of a single dimension. Developing systematic strategies to customize multidimensional interfaces and fully utilize advantages of low-dimensional materials remains challenging. Two-dimensional transition metal dichalcogenides (TMDCs) have garnered significant attention owing to their distinctive electrical conductivity and exceptional interfacial effects. In this study, a series of hollow TMDCs@C fibers are synthesized via sacrificial template of CdS and confined growth of TMDCs embedded in the fibers. The complex permittivity of the hollow TMDCs@C fibers can be adjusted by tuning the content of CdS templates. Importantly, the multidimensional interfaces of the fibers contribute to elevating the microwave absorption performance. Among the hollow TMDCs@C fibers, the minimum reflection loss (RLmin) of the hollow MoS2@C fibers can reach -52.0 dB at the thickness of 2.5 mm, with a broad effective absorption bandwidth of 4.56 GHz at 2.0 mm. This work establishes an alternative approach for constructing multidimensional coupling interfaces and optimizing TMDCs as microwave absorption materials.

Hierarchical Co2 P/CoS2 @C@MoS2 Composites with Hollow Cavity and Multiple Phases Toward Wideband Electromagnetic Wave Absorption

The synergistic effect of hollow cavities and multiple hetero-interfaces displays huge advantages in achieving lightweight and high-efficient electromagnetic wave absorption, but still confronts huge challenges. Herein, hierarchical Co2 P/CoS2 @C@MoS2 composites via the self-sacrificed strategy and a subsequent hydrothermal method have been successfully synthesized. Specifically, ZIF-67 cores first act as the structural template to form core-shell ZIF-67@poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (ZIF-67@PZS) composites, which are converted into hollow Co2 P@C shells with micro-mesoporous characteristics because of the gradient structural stabilities and preferred coordination ability. The deposition of hierarchical MoS2 results in phase transition (Co2 P→Co2 P/CoS2 ), yielding the formation of hierarchical Co2 P/CoS2 @C@MoS2 composites with hollow cavities and multiple hetero-interfaces. Benefiting from the cooperative advantages of hollow structure, extra N,P,S-doped sources, lattice defects/vacancies, diverse incoherent interfaces, and hierarchical configurations, the composites deliver superior electromagnetic wave capability (-56.6 dB) and wideband absorption bandwidth (8.96 GHz) with 20 wt.% filler loading. This study provides a reliable and facile strategy for the precise construction of superior electromagnetic wave absorbents with efficient absorption attenuation.

From VIB- to VB-Group Transition Metal Disulfides: Structure Engineering Modulation for Superior Electromagnetic Wave Absorption

The laminated transition metal disulfides (TMDs), which are well known as typical two-dimensional (2D) semiconductive materials, possess a unique layered structure, leading to their wide-spread applications in various fields, such as catalysis, energy storage, sensing, etc. In recent years, a lot of research work on TMDs based functional materials in the fields of electromagnetic wave absorption (EMA) has been carried out. Therefore, it is of great significance to elaborate the influence of TMDs on EMA in time to speed up the application. In this review, recent advances in the development of electromagnetic wave (EMW) absorbers based on TMDs, ranging from the VIB group to the VB group are summarized. Their compositions, microstructures, electronic properties, and synthesis methods are presented in detail. Particularly, the modulation of structure engineering from the aspects of heterostructures, defects, morphologies and phases are systematically summarized, focusing on optimizing impedance matching and increasing dielectric and magnetic losses in the EMA materials with tunable EMW absorption performance. Milestones as well as the challenges are also identified to guide the design of new TMDs based dielectric EMA materials with high performance.

Hierarchical and Orderly Surface Conductive Networks in Yolk-Shell Fe3 O4 @C@Co/N-Doped C Microspheres for Enhanced Microwave Absorption

Constructing the adjustable surface conductive networks is an innovation that can achieve a balance between enhanced attenuation and impedance mismatch according to the microwave absorption mechanism. However, the traditional design strategies remain significant challenges in terms of rational selection and controlled growth of conductive components. Herein, a hierarchical construction strategy and quantitative construction technique are employed to introduce conductive metal-organic frameworks (MOFs) derivatives in the classic yolk-shell structure composed of electromagnetic components and the cavity for remarkable optimized performance. Specifically, the surface conductive networks obtained by carbonized ZIF-67 quantitative construction, together with the Fe3 O4 magnetic core and dielectric carbon layer linked by the cavity, achieve the cooperative enhancement of impedance matching optimization and synergistic attenuation in the Fe3 O4 @C@Co/N-Doped C (FCCNC) absorber. This interesting design is further verified by experimental results and simulation calculations. The products FCCNC-2 yield a distinguished minimum reflection loss of -66.39 dB and an exceptional effective absorption bandwidth of 6.49 GHz, indicating that moderate conduction excited via hierarchical and quantitative design can maximize the absorption capability. Furthermore, the proposed versatile methodology of surface assembly paves a new avenue to maximize beneficial conduction effect and manipulate microwave attenuation in MOFs derivatives.

Co/CeO2/C composites derived from bimetallic metal-organic frameworks for efficient microwave absorption

CeO2, an n-type semiconductor material, has been widely used in microwave absorption (MA) due to its unique structural features such as oxygen vacancies and interstitial atoms. In this paper, Co/CeO2/C composites were prepared by a hydrothermal method followed by a pyrolysis process. The effect of different pyrolysis temperatures (650-950 °C) on the MA property of the composites was investigated. When the pyrolysis temperature was 850 °C, the Co/CeO2/C-850 composite exhibited outstanding MA behavior in the frequency range of 2-18 GHz, displaying a minimum reflection loss (RLmin) of -45.22 dB and an effective absorption bandwidth (EAB) of 4.61 GHz at a thin thickness of 1.75 mm. The MA performance of the Co/CeO2/C composites is mainly attributed to the dielectric loss due to interfacial polarization originating from different interfaces and dipole polarization caused by the oxygen vacancies in CeO2. In addition, the introduction of Co nanoparticles not only provides the magnetic loss but also modulates impendence matching for the current magnetoelectric coupling system.

Combination strategy of large interlayer spacing and active basal planes for regulating the microwave absorption performance of MoS2/MWCNT composites at thin absorber level

Recently, molybdenum disulfide (MoS₂)/carbon has become a promising candidate for efficient microwave absorption. However, it is still challenging to simultaneously optimize the synergy of impedance matching and loss capability at the level of a thin absorber. Here, a new adjustment strategy is proposed by changing the concentration of precursor l-cysteine for MoS₂/multi-walled carbon nanotubes (MWCNT) composites to unlock the basal plane of MoS₂ and expand the interlayer spacing from 0.62 nm to 0.99 nm, leading to improved packing of MoS₂ nanosheets and more active sites. Therefore, the tailored MoS₂ nanosheets exhibit abundant sulfur-vacancies, lattice-oxygen, more metallic 1T-phase, and higher surface area. Such sulfur-vacancies and lattice-oxygen promote the electronic asymmetric distribution at the solid-air interface of MoS₂ crystals and induce stronger microwave attenuation through interface/dipole polarization, which is further verified by first-principles calculations. In addition, the expansion of the interlayer spacing induces more MoS₂ to deposit on the MWCNT surface and increases the roughness, improving the impedance matching and multiple scattering. Overall, the advantage of this adjustment method is that while optimizing impedance matching at the thin absorber level, composite still maintains a high attenuation capacity, which means enhancing the attenuation performance of MoS₂ itself offsets the weakening of the composite's attenuation ability caused by the decrease in the relative content of MWCNT components. Most importantly, adjusting impedance matching and attenuation ability can be easily implemented by separate control of l-cysteine content. As a result, the MoS₂/MWCNT composites achieve a minimum reflection loss value of -49.38 dB and an effective absorption bandwidth of 4.64 GHz at a thickness of only 1.7 mm. This work provides a new vision for the fabrication of thin MoS₂-carbon absorbers.

Construct of CoZnO/CSP biomass-derived carbon composites with broad effective absorption bandwidth of 7.2 GHz and excellent microwave absorption performance

Biomass-carbon materials have excellent electromagnetic wave attenuation properties, which is one of the essential factors for developing ultra-thin matched-thickness, and high-performance microwave absorption materials. This study reports a two-step procedure consisting of carbonization and subsequent in-situ growth for preparing a wrinkle-like multilayer biomass-derived composites with magnetic Co particles and ZnO particles (CoZnO/C-X). The synergistic effect of a wrinkle-like multilayer structure and Co and ZnO particles, as well as the existence of many heterogeneous interfaces in the composites structure, and efficiently creates multiple scattering and reflections, which gives the composites the strong microwave absorption properties. The minimum reflection loss value (RL_min) of CoZnO/C-X reaches - 54.90 dB with a thickness of 1.8 mm, and the effective absorption bandwidth (lower than - 10 dB) is 7.2 GHz covering from 10.8 GHz to18.0 GHz with matching thickness of 2.0 mm. Furthermore, the reasonable dielectric/magnetic losses, optimized impedance matching and enhanced polarization loss play an indispensable role among improving microwave absorption performance. Thus, this result provides a good potential method for preparation of magnetic particle/metal oxide/biomass-derived carbon microwave absorbing structural materials.

Regulation of Impedance Matching and Dielectric Loss Properties of N-Doped Carbon Hollow Nanospheres Modified With Atomically Dispersed Cobalt Sites for Microwave Energy Attenuation

The rational design of lightweight, broad-band, and high-performance microwave absorbers is urgently required for addressing electromagnetic pollution issue. Metal single atoms (M-SAs) absorbers receive considerable interest in the field of microwave absorption due to the unique electronic structures of M-SAs. However, the simultaneous engineering of the morphology and electronic structure of M-SAs based absorbers remains challenging. Herein, a template-assisted method is utilized to fabricate isolated Co-SAs on N-doped hollow carbon spheres (NHCS@Co-SAs) for high-performance microwave absorption. The combination of atomically dispersed Co sites and hollow supports endows NHCS@Co-SAs with excellent microwave absorption properties. Typically, at an ultralow filler content of 8 wt%, the minimum reflection loss and effective absorption bandwidth of the NHCS@Co-SAs are up to -44.96 dB and 5.25 GHz, respectively, while the absorbing thickness is only 2 mm. Theoretical calculations and experimental results indicate that the impedance matching characteristic and dielectric loss of the NHCSs can be tuned via the introduction of M-SAs, which are responsible for the excellent microwave absorption properties of NHCS@Co-SAs. This work provides an atomic-level insight into the relationship between the electronic states of absorbers and their microwave absorption properties for developing advanced microwave absorbers.

Multilayer Ultrathin MXene@AgNW@MoS2 Composite Film for High-Efficiency Electromagnetic Shielding

Structure and material composition is crucial in realizing high electromagnetic interference (EMI) shielding effectiveness (SE). Herein, an ultrathin MXene@AgNW@MoS₂ (MAM) composite film that resembles the structure of a pork belly and exhibits superior EMI shielding performance was fabricated via the vacuum-assisted suction filtration process and atomic layer deposition (ALD). The staggered AgNWs form skeletons and intersperse in MXene sheets to build a doped layer with three-dimensional network structures, which improves the electrical conductivity of the film. Based on the optimal dispersion concentration of Ag in doped and single layers, the MXene/AgNW doped layer and AgNW single layer are alternately vacuum-assisted-filtered to obtain laminated structures with multiple heterogeneous interfaces. These interfaces generate interface polarization and increase multiple reflection and scattering, resulting in the increased electromagnetic (EM) wave losses. On the other hand, MoS₂ outer nanolayers fabricated precisely by ALD effectively increases the absorption proportion of electromagnetic waves, reduces the secondary reflection, and improves the stability of EMI shielding properties. Ultimately, an ultrathin MAM film (a thickness of 0.03 mm) with five alternating internal layers and MoS₂ outer layers exhibits an excellent EMI SE of 86.3 dB in the X-band.

Hybrid Carbon Sphere Chain-MnO2 Nanorods as Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc-Air Batteries

It is now recognized that the development of self-supported and efficient bifunctional air cathodes via the direct growth of earth-abundant catalysts onto the surface of the conductive collector would be a cutting-edge strategy to reduce interfacial resistance, enhance the mechanical tenure, and reduce the final weight and cost of manufacturing of rechargeable Zn-air batteries (ZABs). This work reports an innovative self-supported precious metal-free electrode, comprising carbon sphere chains (CSCs) directly grown onto a carbon paper (CP) substrate, wherein the CSCs have a functionalized surface bearing carbon nanobud defects, oxygen functional groups, and high-density MnO₂ hierarchical nanorods (NRs), uniformly coating the surface of CSCs. Not only is the metal-free functionalized CSC catalyst functional for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) but its combination with MnO₂ NRs impressively enhances the ORR/OER activities. A homemade ZAB assembled with functionalized CSC/MnO₂ air cathode can successfully power a timer for a period of 17 days with no voltage loss, whereas two series-connected ZABs can light up 39 red light-emitting diode (LED) bulbs. The self-supported and earth-abundant-based CSC/MnO₂ materials open up an opportunity for lightweight and cost-effective ZABs and metal-air batteries in general.

Magnetic Composite Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Thermal Effects and Reactive Oxygen Species

It is difficult to effectively treat bacterial osteomyelitis using photothermal therapy or photodynamic therapy due to poor penetration of light. Here, a microwave (MW)-excited magnetic composite of molybdenum disulfide (MoS₂ ) / iron oxide (Fe₃ O₄ ) is reported for the treatment of bacteria-infected osteomyelitis. In in vitro and in vivo experiments, MoS₂ /Fe₃ O₄ is shown to effectively eradicate bacteria-infected mouse tibia osteomyelitis, due to MW thermal enhancement and reactive oxygen species (ROS) (¹ O₂ and ·O₂ ^- ) production under MW radiation. In addition, the mechanism of MW heat generation is proposed by MW network vector analysis. By the density functional theory and finite element method, the ROS generation mechanism is proposed. The synergy or conductive network between dielectric MoS₂ and magnetic Fe₃ O₄ can reach both enhancement of the dielectric and magnetic attenuation capability. In addition, abundant interfaces are generated to enhance the attenuation of electromagnetic waves by MoS₂ and Fe₃ O_4, introducing multiple reflections and interfacial polarization. Therefore, MoS₂ /Fe₃ O₄ has excellent MW absorption ability based on the synergy or conductive network between MoS₂ and magnetic Fe₃ O₄ as well as multiple dielectric reflections and interfacial polarization.

Micro-flower like Core-shell structured ZnCo@C@1T-2H-MoS2 composites for broadband electromagnetic wave absorption and photothermal performance

Core-shell structure has been receiving extensive attention to enhance the electromagnetic wave (EMW) absorption performance due to its unique interface effect. In this paper, a micro-flower like ZnCo@C@1T-2H-MoS₂ was prepared through MOF self-template method. The introduction 1T-2H-MoS₂ shell helps optimize impedance matching of the CoZn@C particles to improve the EMW absorption ability. The minimal reflection loss (RL_min) value of ZnCo@C@1T-2H-MoS₂ is -35.83 dB with a thickness of 5.0 mm at 5.83 GHz and the effective absorption (RL < -10 dB) bandwidth up to 4.56 GHz at 2.0 mm thickness. Meanwhile, the overall effective absorption bandwidth (OEAB) can reach up to 13.44 GHz from 4.56 to 18.0 GHz. Moreover, ultrafast photothermal performances are also achieved, which can guarantee the normal functioning of ZnCo@C@1T-2H-MoS₂ materials in cold conditions. The excellent EMW absorption and photothermal performance are attributed to the unique structure designed with the core of magnetic ZnCo@C rhombic dodecahedral and the shell of dielectric micro-flower like 1T-2H-MoS₂ optimize impedance matching.

Morphology optimization strategy of flower-like CoNi2S4/Co9S8@MoS2 core@shell nanocomposites to achieve extraordinary microwave absorption performances

Morphology optimization is an effective strategy to take full advantage of interface polarization for the improvement of electromagnetic wave attenuation capability. Herein, a general route was proposed to produce the flower-like core@shell structured MoS₂-based nanocomposites through a simple hydrothermal process. Through the in-situ hydrothermal reaction between the Mo and S sources on the surface of CoNi nanoparticles, flower-like core@shell structured CoNi₂S₄/Co₉S₈@MoS₂ nanocomposites could be successfully synthesized. By regulating the hydrothermal temperature, the flower-like geometrical morphology of samples could be effectively optimized, and the as-prepared sample (S2) synthesized at 200 °C displayed very excellent flower-like morphology compared to the samples (S1 and S3) obtained at 180 and 220 °C. Owing to the excellent interface polarization effect, the as-prepared S2 presented the evidently superior comprehensive microwave absorption properties in terms of strong aborption capability, wide absorption bandwidth and thin matching thicknesses compared to those of S1 and S3. The as-prepared core@shell structured CoNi₂S₄/Co₉S₈@MoS₂ sample with very excellent flower-like morphology simultaneously displayed the minimal reflection loss of -50.61 dB with the matching thickness of 2.98 mm, and the effective absorption bandwidth of 8.40 GHz with the matching thickness of 2.36 mm. Therefore, we provided a general route for the production of flower-like core@shell structured MoS₂-based nanocomposites, which could make the best of interface polarization to develop high-efficiency microwave absorbers.

Lightweight and broadband 2D MoS2 nanosheets/3D carbon nanofibers hybrid aerogel for high-efficiency microwave absorption

Three-dimensional (3D) porous molybdenum disulfide nanosheets/carbon nanofibers (MoS₂/CNF) hybrid aerogels were synthesized by using solvothermal method and following carbonization, where two-dimensional (2D) MoS₂ nanosheets were homogenously in-situ grown on the interconnected CNF skeleton derived from bacterial cellulose, forming a hierarchical porous structure. This unique heterogeneous structure of the MoS₂/CNF hybrid aerogels were conducive to electromagnetic loss, including conduction, polarization, multi-scatterings, and reflections, thus resulting in a balanced impedance matching and microwave attenuation capacity. It was found that the resulted MoS₂/CNF hybrid aerogels demonstrate excellent microwave absorbing performance when the only 5.0 wt% fillers were loaded in paraffin. Particularly, MoS₂/CNF-2-900 hybrid aerogel displayed an effective absorption bandwidth of 5.68 GHz and minimum reflection loss (RL_min) value of -36.19 dB at a thickness of 2.0 mm. As the thickness increases to 4.4 mm, the RL_min value of MoS₂/CNF-2-900 hybrid aerogel reaches -48.53 dB. Electromagnetic loss mechanism analysis indicates that such improved microwave attenuation is attributed to proper component, multiple heterogenous interface and hierarchical porous structures. All the results in this work pave the avenue for the development of ultralight microwave absorber with high absorption capacity as well as broad effective absorption bandwidth.

Dumbbell-Like Fe3O4@N-Doped Carbon@2H/1T-MoS2 with Tailored Magnetic and Dielectric Loss for Efficient Microwave Absorbing

Ferroferric oxide (Fe₃O₄)/C composites have received much attention as a result of converting electromagnetic waves to heat for harvesting efficient electromagnetic wave (EMW) absorbing performance. However, the practical EMW absorbing of these absorbers is still greatly hindered by the unmatched impedance properties and limited EMW absorbing ability. Tuning the morphologies at nanoscale and assembling the nanoarchitecture construction are essential to address this issue. Herein, dumbbell-like Fe₃O₄@N-doped carbon (NC)@2H/1T-MoS₂ yolk-shell nanostructures are rationally designed and fabricated via a facile etching and wet chemical synthesis strategy. By manipulating the etching time toward the magnetic Fe₃O₄ component, the dielectric and magnetic loss of absorbers could be well-tuned, thus achieving the optimized impedance characteristics. As a result, the maximum refection losses (RL_maxs) of Fe₃O₄@NC-9h and Fe₃O₄@NC-15h are -19.8 dB@7.9 GHz and -39.5 dB@8.3 GHz, respectively. Moreover, the MoS₂ nanosheets with a mixed 2H/1T phase anchored on Fe₃O₄@NC-15h (Fe₃O₄@NC-15h@MoS₂) further boost the RL_max to -68.9 dB@5.8 GHz with an effective absorbing bandwidth of ∼5.25 GHz. The tailored synergistic effect between dielectric and magnetic loss and the introduced interfacial polarization (Fe₃O₄@NC/MoS₂) are discussed to explain the drastically enhanced microwave absorbing ability. This work opens up new possibilities for effective manipulation of electromagnetic wave attenuation performance in magnetic-dielectric-type nanostructures.

MoS2 nanoparticle/activated carbon composite as a dual-band material for absorbing microwaves

In the search for novel high-performance microwave (MW) absorbers, MoS2 has shown promise as a MW-absorbing material, but its poor impedance matching limits its applications. Herein, a facile hydrothermal method was used to produce a composite consisting of activated carbon (AC) derived from waste biomass and in situ-grown MoS2 nanoparticles. Its microwave absorption properties were examined in the 2-18 GHz frequency range, and FESEM and HRTEM images confirmed the formation of MoS2 nanoparticles on the AC. The maximum reflection loss (RLmax) for the MoS2/AC composite was -31.8 dB (@16.72 GHz) at 20 wt% filler loading. At 50 wt% filler loading, the MoS2/AC (MAC50) composite exhibited unique dual-band absorption characteristics in the C and Ku bands. An effective absorption bandwidth (RL < -10 dB) of 10.4 GHz (3-5.2 GHz, 9.8-18 GHz) was achieved at various thicknesses that covered the entire Ku band. Therefore, a sole dielectric absorber can easily be tuned to absorb MWs at multiple frequency ranges. The large surface area and conduction losses of AC combined with the superior dielectric loss properties of MoS2 resulted in improved impedance matching and attenuation ability of the MoS2/AC composite. Thus, MoS2/AC is a promising low-cost dielectric absorber for MW absorption applications.

Melamine-induced formation of carbon nanotubes assembly on metal-organic framework-derived Co/C composites for lightweight and broadband microwave absorption

Extending effective absorption bandwidth at a low filling ratio is still a challenge for metal-organic framework-derived microwave absorbing materials. Herein, varied complex structures based on CNTs have been built on Co/C particles derived from ZIF-67 via melamine-involved annealing routes. It was found that cobalt nanoparticles derived from ZIF-67 act as catalysts for the growth of CNTs, effectively promoting and controlling the content of melamine. Due to the effective control of the CNT-containing complex structure, excellent microwave absorption performance was achieved at a rather low filling ratio of 20 wt%, which can be attributed to improved attenuation ability and ameliorated impedance matching. Results show that highly graphitic CNTs benefit the formation of the electron transport network and enhancement of conduction loss. Unique one-dimensional complex structure and abundant Co/C interfaces strengthen the polarization loss. When the dielectric loss was optimized at different frequencies, appropriate impedance matching was also gained to realize a broad effective absorption bandwidth of 5.6 and 4.4 GHz in Ku and X bands, respectively. This work may provide novel insights into the synthesis and design of CNT-containing metal-organic framework-derived materials with lightweight features and wide frequency response.

MoS2-Decorated/Integrated Carbon Fiber: Phase Engineering Well-Regulated Microwave Absorber

Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.

Defect Induced Polarization Loss in Multi-Shelled Spinel Hollow Spheres for Electromagnetic Wave Absorption Application

Defect engineering is an effective approach to manipulate electromagnetic (EM) parameters and enhance absorption ability, but defect induced dielectric loss dominant mechanism has not been completely clarified. Here the defect induced dielectric loss dominant mechanism in virtue of multi-shelled spinel hollow sphere for the first time is demonstrated. The unique but identical morphology design as well as suitable composition modulation for serial spinels can exclude the disturbance of EM wave dissipation from dipolar/interfacial polarization and conduction loss. In temperature-regulated defect in NiCo2O4 serial materials, two kinds of defects, defect in spinel structure and oxygen vacancy are detected. Defect in spinel structure played more profound role on determining materials' EM wave dissipation than that of oxygen vacancy. When evaluated serial Co-based materials as absorbers, defect induced polarization loss is responsible for the superior absorption performance of NiCo2O4-based material due to its more defect sites in spinel structure. It is discovered that electron spin resonance test may be adopted as a novel approach to directly probe EM wave absorption capacities of materials. This work not only provides a strategy to prepare lightweight, efficient EM wave absorber but also illustrates the importance of defect engineering on regulation of materials' dielectric loss capacity.