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SiO 2 -supported SiC/B 4 C (SiO 2 –SiC/B 4 C) nanowires were synthesized by using SiO 2 @C nanospheres, amorphous B powders and catalyst Ni(NO 3) 2 ·6H 2 O as raw materials, and exhibited remarkable microwave absorbing characteristics. The minimum reflection loss of the SiO 2 –SiC/B 4 C nanowire/paraffin composite reaches −41.33 dB with an effective absorption bandwidth up to 9.69 GHz. The broadband microwave absorption of SiO 2 –SiC/B 4 C nanowires is attributed to the synergistic effect of interfacial polarization relaxation and conduction loss. While conductive loss dominates at low frequencies within 2–8 GHz, polarization loss caused by the heterogeneous interfaces plays an important role at high frequencies, especially between 10 and 16 GHz. The movement of the polarization relaxation peaks to lower frequencies in the composites is further investigated by modeling the relaxation process as a rotating sphere in a viscous fluid. The linear relationship between relaxation time and conductivity indicates that the conductivity is an important factor that affects the electromagnetic wave (EMW) absorption performance not only on the impedance matching and attenuation constant of the materials, but also regulates the relaxation time, and this result provides a new idea for exploring the absorption mechanism of EMW absorbing materials. [ABSTRACT FROM AUTHOR]

High yielding synthesis of hollow carbon cubes (HCCs) was realized by using easily available NaCl cubes as templates in a simple way. The cubic carbon shells featuring an average side length of 3.5 μm, a thickness of 22.9 nm and the presence of macro and mesopores in the material, endow the HCCs/paraffin composites with an appropriate balance between good impedance matching and strong loss capacity. Superior electromagnetic wave (EMW) absorption performance was obtained at a very low loading ratio of 1.5 wt% of the HCCs. The composite having 4.5 mm thickness gave the maximum reflection loss of −46.0 dB at 7.8 GHz. At a thickness of 2.6 mm, a maximum effective absorption bandwidth of 6.6 GHz was achieved. Further investigation on the EMW dissipation mechanism of HCCs surrounding polarization relaxation and conductive loss was conducted. The integrity of the hollow structure plays a dominant role during EMW dissipation. The present study provides easy processing, cost-effective and environment-friendly HCCs as a predominant candidate for ultralight carbon-based EMW absorbing materials. [Display omitted] • High-yielding synthesis of hollow carbon cubes using NaCl cubes as template. • Superior microwave absorption performance at a low loading ratio of 1.5 wt %. • Dipole polarization observed by measuring temperature dependence of ε′ and tanδ. • Hollow structure effect on the performance studied by damage treatment of HCCs. [ABSTRACT FROM AUTHOR]

Novel FeB/B 4 C nanowire composite was synthesized by a catalyst-assisted process. The results showed that the composite contains mainly B 4 C nanowires with diameters under 100 nm and FeB nanoparticles with a size of ~50 nm. Reflection loss value of the FeB/B 4 C nanowire-paraffin composite reaches −13.6 dB at 8.2 GHz when the thickness is 3.5 mm, and absorption bandwidth with RL below −10 dB reaches 1.6 GHz (7.5–9.1 GHz). The minimum RL value reaches −50.8 dB at 17.4 GHz when the thickness is 4.8 mm, with the absorption bandwidth increased to 2.4 GHz (15.6–18.0 GHz). Electromagnetic parameters of the composite were studied to understand its excellent microwave absorbing properties. [ABSTRACT FROM AUTHOR]

The ingenious design of heterogeneous structures is an effective strategy for developing advanced microwave absorption materials. In this study, high-efficiency void@carbon@TiO 2 (void@C@TiO 2) cubes were synthesized by a template sol method. Compared with void@carbon (void@C) and void@TiO 2 cubes, the void@C@TiO 2 cubes/paraffin composites of 2.1 µm edge length show excellent microwave absorption performances (MAPs). When the thickness is 2.1 mm, the minimum reflection loss (RL) of – 69.8 dB is superior to – 31.5 dB of void@C cubes at 4.1 mm and – 3.1 dB of void@TiO 2 cubes at 3.7 mm. The effective absorption frequency covers 11.8 GHz (6.2–18.0 GHz, RL below – 10 dB) by matching the coating thickness with 1.7–5.0 mm. The enhanced MAPs originated from the synergistic processes of good impedance matching (|Z in /Z 0 |) and various microwave dissipation mechanisms, including electrical conduction, interfacial charge accumulation, and defect dipolar polarization. The void@C@TiO 2 cubes are a lightweight, easy, environment-friendly, and extendible strategy for microwave absorption applications. • The novel template sol method is a simple, non-toxic, cheap, short-cycle, and recycling strategy for void@C@TiO 2 cubes. • The void@C@TiO 2 cubes with 2.1 µm edge length show a minimum RL of − 69.8 dB when the thickness is 2.1 mm, simultaneously satisfying the EAB of 4.9 GHz at a 20.0 wt% low loading ratio. • The dissipation mechanisms are attributed to conductance loss (annular current), interfacial polarization between TiO 2 and A (A = TiO 2 , C, and paraffin), and defect dipole polarizations (V O • • , T i T i ˊ , and T i T i ˊ → V O • • ← T i T i ˊ ). [ABSTRACT FROM AUTHOR]