Magnetic‒carbon composites, as functional materials, present significant challenges in understanding the mechanism by which magnetic particle distribution influences their electromagnetic (EM) properties. This study innovatively proposes a melamine-induced surface magnetic regulation strategy, successfully constructing a composite microsphere system with tunable microwave absorption (MA) performance. By precisely controlling the amount of melamine added, the distribution of magnetic nanoparticles (NPs) on the carbon microspheres was accurately regulated, thereby achieving customized space distribution and optimizing the impedance EM properties. The reduced magnetic Co NPs further catalyzed the formation of a graphitized carbon layer from polyvinylpyrrolidone. Moreover, the introduction of melamine further modulated Co NP growth, resulting in their spatial distribution along the interiors, surface, and exterior of the microspheres. Finally, Co@C-CNT-2 composites with optimized magnetic particle distributions exhibited excellent MA performance, achieving a minimum reflection loss value (RL_min) of −32.48 dB and excellent effective absorption bandwidth (EAB) of ~ 5.2 GHz at a thickness of 1.8 mm. The synergistic effect of dielectric and magnetic loss is realized through the surface magnetization strategy, which provides a new strategy for the design of high-performance EM wave absorption materials.

With the progress of electronic communication technology, the intensity of electromagnetic radiation is getting strength, and the traditional absorbing materials can no longer meet the needs of various current environments. Dielectric nanomaterials have received much attention in energy conversion, electromagnetic shielding and absorption due to their nanosize effects and structural tunable properties. However, the mismatch impedance and the single loss mechanism severely limit its application in the field of microwave absorption. In this paper, we modified the doped ZnCo₂O₄ with the guidance of density functional theory (DFT) simulation, effectively regulate the dielectric parameters and adjust the microwave absorption characteristics, which stems from the transformation of electron energy between doped ions and some defects. Meanwhile, we further experimentally observe significant magnetic components at the doped ZnCo₂O₄, resulting in improved magnetic properties and producing a large number of dipoles. Due to the best impedance match and enhanced polarization loss, the minimum reflection loss is −37 dB, and the effective absorption bandwidth (EAB) is 7.21 GHz. This provides ideas for the design of cobalt acid-based materials as efficient microwave absorbers.

Graphene is a promising electromagnetic wave absorption (EMWA) material because of its structural designability, controllable electromagnetic properties, and excellent stability. However, the impedance mismatch caused by high conductivity and dielectric properties has seriously hindered the application of graphene in the EMWA field. In this work, based on the dielectric dispersion behavior of ideal broadband absorption as a guide, a Fe microsheet/reduced graphene oxide (Fe/RGO) composite was prepared by simple hydrothermal and thermal reduction methods. The permittivity of RGO is optimized by adjusting the content of anisotropic Fe microsheets, and a balance between attenuation ability and impedance matching is achieved. Theoretical calculations and off-axis electron holography results reveal that the abundant polar sites and heterogeneous interfaces of Fe and RGO enhance the dipole and interface polarizations. The three-dimensional (3D) conductive network structure contributes to multiple reflections of incident electromagnetic waves and conduction loss. The natural and exchange resonances and eddy current loss caused by anisotropic Fe microsheets further increase magnetic loss. Based on the dielectric-magnetic loss mechanism and good impedance matching, Fe/RGO achieves a minimum reflection loss (RL_min) of −67.95 dB at 8.48 GHz and a maximum effective absorption bandwidth (EAB_max) of 6.91 GHz (11.09–18 GHz) with a low filling content of 10 wt%. In addition, Fe/RGO has excellent radar stealth performance, with a radar cross section (RCS) of −31.21 dBm² at 0°. Therefore, the proposed strategy and theoretical analysis provide a reference for the microstructure design, composition, and mechanism analysis of EMWA materials.

Magnetic/dielectric composite materials with numerous heterointerfaces are highly promising functional materials, which are widely applied in the fields of electromagnetic wave absorption. Constructing heterogeneous structure is beneficial to further enhance the microwave absorption performance of composite materials. However, the process of constructing multi-heterogeneous interfaces is extremely complex. In this work, hollow porous FeCo/Cu/CNTs composite microspheres are prepared by the simple spray drying method and subsequently two-step annealing treatment, which possess abundant heterogeneous interfaces, unique three-dimensional conductive network and magnetic coupling network. This unique structure is beneficial to improving the ability of dielectric loss and magnetic loss, and then achieving an excellent microwave absorption performance. The prepared FeCo/Cu/CNTs-1 composite microspheres maintain a minimum reflection loss (RL) of –48.1 dB and a maximum effective absorption bandwidth of 5.76 GHz at a thickness of 1.8 mm. Generally, this work provides a new idea for designing multi-heterogeneous of microwave absorbing materials.

Development of high-performance microwave absorption materials (MAM) with stabilized magnetic properties at high temperatures is specifically essential but remains challenging. Moreover, the Snoke's limitation restrains the microwave absorption (MA) property of magnetic materials. Modulating alloy components is considered an effective way to solve the aforementioned problems. Herein, a hollow medium-entropy FeCoNiAl alloy with a stable magnetic property is prepared via simple spray-drying and two-step annealing for efficient MA. FeCoNiAl exhibited an ultrabroad effective absorption band (EAB) of 5.84 GHz (12.16–18 GHz) at a thickness of just 1.6 mm, revealing an excellent absorption capability. Furthermore, the MA mechanism of FeCoNiAl is comprehensively investigated via off-axis holography. Finally, the electromagnetic properties, antioxidant properties, and residual magnetism at high temperatures of FeCoNiAl alloys are summarized in detail, providing new insights into the preparation of MAM operating at elevated temperatures.

Yolk–shell urchin-like porous Co₃O₄/NiO@C microspheres were successfully synthesized via a facile solvothermal method and annealing treatment under an argon atmosphere. High reversible specific capacity, long cycling stability, and excellent rate capability were achieved for the material due to its specific yolk–shell urchin-like porous structure and coated carbon layers. The pores distributed on the yolk and shell, as well as the gap between the yolk and shell, provide numerous pathways for the penetration of electrolyte, and enhance the reversible specific capacity (the initial discharge specific capacity was as high as 1405.7 mA h g⁻¹ at 0.1 C). Meanwhile, the stress and volume expansion could be greatly released and relieved through the pores, and long cycling stability was achieved (a high reversible specific capacity of 502.7 mA h g⁻¹ was maintained after 1000 cycles at 5 C). The coated carbon layers greatly enhance the conductivity of the yolk–shell urchin-like porous Co₃O₄/NiO microspheres, accelerate the transmission of electrons, and improve their rate performance (a reversible specific capacity of 397.5 mA h g⁻¹ was achieved when the current density was increased to 10 C).

The design and optimization of one-dimension (1D) magnetic material are of great importance for the energy conversion, storage and spin electron devices, which remain a huge challenge. Herein, 1D porous Fe₃O₄ nanotubes (NTs) have been fabricated via a combined process of electrospinning and calcination. In the electrospinning precursors, by regulating the content ratio between two types of polyvinyl pyrrolidone with different molecular weight, porous Fe₃O₄ NTs with vortex-domain configuration have been fabricated. Based on the unique 1D nanotube structure encapsulated with multi-domains, the composite Fe₃O₄ NTs exhibit high complex permeability (μʹ, μʺ) values, and hold both strong magnetic storage and dissipation capacity. Our Fe₃O₄ NTs exhibit excellent microwave absorption (MA) performance with the maximum reflection loss value of −57.1 dB and the efficient absorption bandwidth of 12.0 GHz. The generated magnetic vortices make the crucial contribution to the spin-wave resonance which improves the MA dissipation under high-frequency. Related magnetic flux line distribution and magnetic domain moment were confirmed by the electron holography and micro-magnetic simulation, respectively, providing the deep insight to the microwave absorption mechanism.

Maximizing wave function overlap (WFO) within type-II superlattices (T2SL) is demonstrated to be important for improving their photoelectric properties, such as optical transition strength and quantum efficiency, which, however, remains a great challenge for now. Herein, the dual strategy of modulating growth temperature and inserting ultrathin AlAs barrier into the AlSb layers is presented to enhance the WFO in InAs/AlSb T2SL. The charge distributions and strain states indicate that moderate growth temperature of 470 °C promotes the As–Sb exchange at AlSb-on-InAs (AOI) interfaces, which would introduce skew of energy band structure towards InAs-on-AlSb (IOA) interface. Such band structure could drive electrons and holes to the IOA interfaces simultaneously, thus resulting in the enhanced WFO. On this basis, insertion of relatively thick (0.3 nm) AlAs layers is found to squeeze more holes towards adjacent interfaces, boosting the WFO further. The InAs/AlSb superlattices with optimized WFO reveal better optical performance, where the peak intensity shows 50% improvement in the PL spectra than the original one. Moreover, a dual-miniband radiative transition mechanism appears in the InAs/AlSb superlattice with relatively thick AlAs intercalation, which helps broaden the wavelength range of the superlattice.

Cobalt diselenide (CoSe₂) hierarchical clew-like structure is synthesized via a dual-surfactant templated hydrothermal process, and for the first time, its microwave absorption capability has been established. Specifically, the as-synthesized hierarchical interconnected structure is assembled by numerous dense nanobelts. Meticulous tuning of the synthetic conditions which could influence the hierarchical architecture indicates that, in this system, cetyltrimethylammonium bromide (CTAB) plays a dominate role of "balling" while protonated diethylenetriamine (DETA) plays the role of "stringing" . As a novel absorbent, the microwave absorption performance of CoSe₂ microstructure is evaluated in 2-18 GHz band. Particularly, 3D hierarchical CoSe₂ microclews exhibit superior minimum reflection loss of -26.93 dB at 7.28 GHz and effective absorption bandwidth of 3.72 GHz, which are ~120% and ~104% higher than those of simple CoSe₂ nanosheets, respectively. Such drastic enhancement could be attributed to the large specific surface area, and more dissipation channels and scattering sites enabled by the unique clew-like microstructure. The versatile dual-surfactant templated assembly of hierarchical CoSe₂ microstructure, along with its appreciable dielectric microwave absorption performance, provides new inspirations in developing novel microwave absorbents for mitigation of electromagnetic pollution.

Ag₃PO₄ as a novel photoanode material, despite its arguably highest photoactivity, suffers for its poor light absorption and stability for photoelectrochemical (PEC) water oxidation. In this work, 4.5 × 4.5 cm² Ag₃PO₄ microcrystalline films are grown via a room-temperature solution process, and vacuum annealing is proposed to solve the stability and light absorption issues. It is found that the major process below 400 ℃ of vacuum annealing is the |Recovery| process for Ag₃PO₄ microcrystals, when lattice defects and Ag⁰ surface species get reduced. Next, |Recrystallization| stage occurs at >400 ℃. The recovery of native defects of silver vacancies, with both density functional theory calculation and experimental results, could simultaneously improve the light absorption and catalytic activity of Ag₃PO₄. The 400 ℃-annealed Ag₃PO₄ photoanode, with enhanced light harvesting and crystal quality, exhibits 88% increase in (J_light − J_dark) value (1.94 mA cm⁻²) than non-annealed photoanode (1.03 mA cm⁻²). Moreover, it retains >99% current density after a 4000-s stability test. These results suggest that vacuum annealing can substantially improve the PEC performance of Ag₃PO₄ microcrystalline film photoanodes due to mitigated effects of native defects, improved light harvesting, and inhibited Ag₃PO₄ decomposition during water oxidation reaction.