Facile fabrication of ultra-light N-doped-rGO/g-C3N4 for broadband microwave absorption

"Thin thickness", "lightweight", "wide absorption bandwidth" and "strong absorption" are the new standards of contemporary science and technology for microwave absorption(MA) material. In this study, N-doped-rGO/g-C3N4 MA material was prepared for the first time by simple heat treatment, which the N atoms were doped into rGO and g-C3N4 was dispersed on the surface of N-doped-rGO, and its density is only 0.035 g/cm3. The impedance matching of the N-doped-rGO/g-C3N4 composite was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C3N4 semiconductor property and the graphite-like structure. Moreover, the distribution of g-C3N4 among N-doped-rGO sheets can produce more polarization effect and relaxation effect by increasing the lamellar spacing. Furthermore, the polarization loss of N-doped-rGO/g-C3N4 could be increased successfully by doping N atoms and g-C3N4. Ultimately, the MA property of N-doped-rGO/g-C3N4 composite was optimized significantly, with a loading of 5 wt%, the N-doped-rGO/g-C3N4 composite exhibited the RLmin of -49.59 dB and the effective absorption bandwidth could reach 4.56 GHz when the thickness was only 1.6 mm. The "thin thickness", "lightweight", "wide absorption bandwidth" and "strong absorption" of MA material are actually achieved by the N-doped-rGO/g-C3N4.

Lightweight Chain-Typed Magnetic Fe3O4@rGO Composites with Enhanced Microwave-Absorption Properties

A lightweight microwave-absorbing material with a strong electromagnetic-absorption capability of practical significance in the field of electromagnetic compatibility was obtained by adjusting the ratio of Fe₃O₄ and rGO. A nanoparticle material with a chain-typed structure consisting of a combination of Fe₃O₄ and rGO was produced by a hydrothermal method under an applied magnetic field. The electromagnetic loss property of the Fe₃O₄@rGO composites is studied in the frequency range from 2 to 18 GHz. In addition, the reflection loss and the mechanism of microwave absorption are explored. By changing the amounts of rGO, the electromagnetic loss of the Fe₃O₄@rGO composites can be effectively regulated, which obtain better reflection loss. The minimum reflection loss of the Fe₃O₄@rGO composites is -49.4 dB at 16.2 GHz only with a thickness of 1.75 mm. Thus, the Fe₃O₄@rGO composites have an extremely thin thickness and a strong electromagnetic wave absorption capacity, which is a candidate for the development of lightweight magnetic absorbing materials.

Ultralight reduced graphene oxide aerogels prepared by cation-assisted strategy for excellent electromagnetic wave absorption

In this work, to maximize the unique attributes of reduced graphene oxide (RGO) for excellent microwave absorption, the ultralight RGO aerogels with improved dispersion and interface polarization performance were fabricated via a facile cation-assisted hydrothermal treatment process. The prepared RGO/paraffin composite exhibits excellent microwave absorption (MA) performance in a wideband frequency range of 8.0 ∼ 18.0 GHz with an ultralow absorbent content of 0.5 wt.%. Such performance is comparable with most previously reported results on RGO-based composites but required much higher absorbent content. The mechanisms for the enhancement of polarization relaxation loss and conductive loss were investigated in detail. This study provides a promising and facile method for preparing RGO-based excellent microwave absorption materials with ultra-low filler content, which is significant for designing efficient MA absorbers.

A new flexible and ultralight carbon foam/Ti3C2T X MXene hybrid for high-performance electromagnetic wave absorption

A new ultralight carbon foam/Ti3C2T X (CF/MXene) electromagnetic (EM) absorbing hybrid with three-dimensional network structure was fabricated by vacuum impregnation and freeze-drying process. These hybrids display excellent flexibility and steady compression-resilience properties and also the special three-dimensional structure with ultralow density of only 5-7 mg cm-3 shows higher EM absorption than most foam-based EM absorbers. Studies have shown that the minimum reflection loss of CF/MXene-N2 reaches -45 dB at 8.8 GHz with the Ti3C2T X nanosheets content of 9.8%. In the meanwhile, the effective absorption bandwidth of CF/MXene-N2 can also reach up to 5 GHz (from 6.9 GHz to 11.9 GHz) with the thickness of 4.5 mm. Moreover, the fundamental EM absorption mechanism of CF/MXene hybrids involved to impedance matching, conductive loss and polarization loss is carefully analyzed. Thus, it is expected that the new ultralight carbon foam/Ti3C2T X hybrids with three-dimensional network structure will have great application prospects in the fields of EM absorption.

Ultralight MXene-Coated, Interconnected SiCnws Three-Dimensional Lamellar Foams for Efficient Microwave Absorption in the X-Band

Two-dimensional (2D) few-layered Ti₃C₂T _X MXene (f-Ti₃C₂T _X) has been proved to be one of the most promising electromagnetic interference (EMI) materials, but its electromagnetic (EM) absorption properties and loss mechanism have not been studied so far. Herein, for the first time, ordered lamellar f-Ti₃C₂T _X/SiCnws hybrid foams with ultralow density are synthesized by a combination of self-assembly and bidirectional freezing processes. The freestanding foams exhibit excellent EM absorption properties superior to most of the current foam-based counterparts. The effective absorption bandwidth is always able to cover the whole X-band, when the sample thicknesses of f-Ti₃C₂T _X/SiCnws hybrid foams distribute in any value between 3.5 and 3.8 mm, and the minimum reflection coefficient reaches -55.7 dB at an ultralow density of only about 0.029 g·cm^-3. The fundamental mechanism associated with optimized impedance matching, enhanced polarization loss, and conductive loss is discussed in detail. Our results evidence that 2D flexible f-Ti₃C₂T _X MXene has great potential in EM absorption field like graphene.

Facile Fabrication of Three-Dimensional Lightweight RGO/PPy Nanotube/Fe3O4 Aerogel with Excellent Electromagnetic Wave Absorption Properties

In this article, a three-dimensional chemically reduced graphene oxide/polypyrrole nanotubes (PPy nanotubes)/Fe₃O₄ aerogel (GPFA) was fabricated by a simple one-step self-assembly process through hydrothermal reduction. The addition of both PPy nanotubes and Fe₃O₄ nanoparticles is aimed to avoid the aggregation of graphene sheets, effectively adjust the permittivity, and make better impedance matching between dielectric loss and magnetic loss of the composite aerogel to gain excellent electromagnetic (EM) wave absorption performance. The EM wave-absorbing results indicate that the ternary composite with an ultralow density of about 38.3 mg/cm³ shows an improved EM wave-absorbing property with a maximum reflection loss of -49.2 dB at the frequency of 11.8 GHz, with an effective absorption bandwidth below -10 dB reaching 6.1 GHz (9.8-15.9 GHz) at a thickness of 3.0 mm. Such an outstanding EM wave absorption behavior can be attributed to the multiple reflections, polarizations, and relaxation processes in the aerogel.