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CoZr columnar structured magnetic films were fabricated by oblique sputtering onto porous aluminum oxide substrates with different oblique angles. The scanning electron microscope images showed the formation of columnar structure and nanoporous structure was disappeared with increasing oblique angle. The static magnetic properties showed larger coercivity and lower magnetization squareness due to columnar structure resulted from nanopores. Dynamic magnetic properties were determined by effect of holes and oblique sputtering. Enhanced microwave absorption was obtained by complex permeability measurement, which line width of columnar film increased 1.4 GHz comparing with 0.5 GHz of continuous film. Therefore, it is an effective way to get the adjustable anisotropy field and line width, which is desirable for obtaining the high resonance and high permeability ferromagnetic film materials for high frequency application. [ABSTRACT FROM AUTHOR]

Abstract: We report a template-free hydrogen reduction approach to prepare sponge-like cobalt nanoporous structures employing Co3O4 as precursors, which were obtained by thermal-decomposing of CoCO3 intermediates prepared by a facile solvent-thermal route. A three-step formation mechanism for the Co nanoporous structures was proposed. The epoxy resin composites with 65wt.% rhomb-like and rod-like samples showed efficient electromagnetic wave absorption characteristics (RL<−20dB) in the ranges of 12.8–18GHz and 11.2–18GHz over absorber thicknesses of 1.05–1.5mm and 1.0–1.6mm, respectively. It is believed that the porous metallic magnets would gain wide applications as more efficient electromagnetic wave absorbers. [Copyright &y& Elsevier]

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 NiCo 2 O 4 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. [ABSTRACT FROM AUTHOR]

Low density, high stability and strong dielectric loss capacity endow carbon-based nanocomposites with superb microwave dissipation performances. Different from grapheme or carbon nanotubes, the graphitization degrees of carbon-based composites derived from the organic precursor pyrolysis can be accurately regulated by controlling the carbonization temperature. As such, their electromagnetic properties can be easily tuned. In this work, we report the preparation of TiO 2 /Co/Carbon nanofibers (CNFs) through a combined approach of electrospun and carbonization at different temperatures. The nanofibers with an average diameter of 300 nm were coated by a dense layer of TiO 2 and embedded by Co/CoO nanoparticles. The performance evaluation indicated the composite obtained at 700 °C exhibits remarkably strong absorption of −63.2 dB at 9.8 GHz and wide effective absorption bandwidth of 6.4 GHz with a pretty low filling rate of 15 wt%. Further analysis on the electromagnetic behaviors shows that the composite possesses regulable impedance matching characteristic and absorption performances, implying the huge application potential under various demand conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multiple polarizations and losses are enhanced by the Co-N-C particles. • The RL min of PI/rGO/CNC-1 aerogel reaches −75 dB with the EAB max of 7.28 GHz. • The PI/rGO/CNC aerogel integrates excellent multifunctional features. The fabrication of dielectric/magnetic multicomponent hybrids represents a promising strategy for achieving advanced electromagnetic wave (EMW) absorption performances. However, it also poses a significant challenge due to the difficulty in fully utilizing the properties of each component. Here, in this work, metal–organic frameworks (MOFs) derived Co-N-C species were combined with graphene oxide/polyamide acid and then freeze-dried and annealed to produce PI/rGO/CNC aerogels. These aerogels exhibit outstanding EMW absorption properties owing to their multiple heterogeneous interfaces and synergetic electromagnetic losses while retaining satisfying mechanical properties and lightweight features of PI/rGO aerogels. In particular, PI/rGO/CNC-1 aerogel shows the optimal EMW attenuation performance with a minimal reflection loss (RL min) value of –75 dB, and its maximal effective absorption bandwidth (EAB max) is as broad as 7.28 GHz. Moreover, the lightweight nature, elastic feature, structural stability, thermal insulation and hydrophobicity of the PI/rGO/CNC aerogels ensure that they have vast application prospects as advanced EMW absorption materials in complicated environment. [ABSTRACT FROM AUTHOR]

• A specific and feasible method to fabricate specially designed one-dimensional structure. • A complicated nanostructure of the flakes-assembled porous ZnO/Ni hybrid nanotubes. • Revealing the inner attenuation mechanism of enhanced electromagnetic absorption performances. Flakes-assembled ZnO/Ni hybrid nanotubes were synthesized by electrospinning with hydrothermal treatment, calcination and reduction reaction for the electromagnetic wave absorption. The synergy effects between ZnO and Ni and absorbing mechanisms were investigated. [Display omitted] Electromagnetic (EM) wave absorption materials with excellent absorption performances are highly desirable because of military applications and EM radiation pollution protection. In this work, we have synthesized and demonstrated the flakes-assembled porous ZnO/Ni hybrid nanotubes by combining electrospinning and hydrothermal reaction, coupled with following calcination and reduction process. The rational-designed ZnO/Ni nanocomposites exhibited extremely superb EM wave absorption property with a minimum reflection loss (RL) of −71.2 dB at 15.3 GHz, corresponding to a thickness of 3.4 mm and the maximum effective absorption bandwidth (RL≤–10 dB) is up to 9.4 GHz (8.6–18.0 GHz) with the thickness of 4.2 mm. The significant performance improvement originated from that the unique three-dimensional architecture optimized impedance matching characteristics and magnetic-dielectric synergetic effect contributed to a strong attenuation capacity. This work provided a feasible strategy to synthesize flakes-assembled nanotube microstructure and the ZnO/Ni composites promised great potential in the EM wave absorption fields. [ABSTRACT FROM AUTHOR]

• A facile method to design carbon nanofibers loaded with oxides or metals. • Unique 3D micro-network morphology contributing to electromagnetic absorption. • Deeply investing the separate function of dielectric metal oxide and magnetic metal. • Employing 2D projection images of impedance matching characteristic to assist in the analysis. • Revealing the inner attenuation mechanism of enhanced electromagnetic absorption performances. Carbon materials are widely used for electromagnetic wave absorption. However, to find out a more rational approach to improve the electromagnetic (EM) wave absorption performance is still worthy of attention. In this work, the carbon nanofibers (CNFs) decorated by titanium oxide and metallic cobalt (TiO 2 /Co/CNFs) were synthesized by electrospinning and carbonizing process, and the microtopography, structure, composition and magnetic properties of which were characterized in detail. The TiO 2 /Co/CNFs nanocomposites acquired optimal electromagnetism parameters and exhibited superb electromagnetic wave absorption property. The results showed that the minimum reflection loss (RL) values of TiO 2 /Co/CNFs samples with different filling ratios are less than −50 dB with the matching thickness less than 3.5 mm. The maximum effective absorption bandwidths (RL ≤ −10 dB) exceed 5.2 GHz. Besides, the strong absorption frequency range can be regulated by adjusting filling ratios to broaden the application. This work provides a unique approach to design carbon nanofibers loaded with oxides or metals, and the TiO 2 /Co/CNFs nanocomposites could be an ideal candidate as light-weight and high-efficiency electromagnetic wave absorption materials and the tunable absorption property portend the potential application in various environmental conditions. [ABSTRACT FROM AUTHOR]