Controllable synthesis of Fe3O4-based magneto-dielectric ternary nanocomposites and their enhanced microwave absorption properties.

In order to overcome the drawbacks of Fe3O4 composite samples and greatly increase their performance in microwave absorption, magnetic Fe3O4 spindles coated with dielectric SnO2 nanorods and MnO2 nanoflakes have been successfully synthesized by a four-step simple hydrothermal route. This rationally designed magneto-dielectric ternary nanocomposite will introduce multiple reflection and conductive losses caused by its special multilayer structure and the effective complementarity of dielectric loss and magnetic loss. Therefore, its absorbing performance can be greatly improved. It is notable that the as-prepared Fe3O4@SnO2@MnO2 nanocomposites show a minimum reflection loss value of -50.40 dB at 17.92 GHz at a thickness of 3.9 mm and the absorption bandwidth ranges from 3.62 to 12.08 GHz. The as-prepared Fe3O4@SnO2@MnO2 ternary nanocomposite is expected to be a potential candidate for high-performance microwave-absorbing materials with intensive electromagnetic wave absorption and wide effective absorbing bandwidth.

Investigation and optimization of Fe/ZnFe2O4 as a Wide-band electromagnetic absorber.

In this research, a facile in-situ growth method was applied to load ZnFe2O4 nanoparticles on carbonyl iron (Fe) flakes. These loaded ZnFe2O4 exhibited cone shape with an average size of ∼200 nm. The results revealed that the frequency region with reflection loss <-10 dB (fE) was up to 6.2 GHz (d = 1.5 mm), suggesting excellent wideband electromagnetic absorption (EM) properties. The electromagnetic absorption mechanism was discussed in depth which attributed to the synergetic effect of Fe and ZnFe2O4. The loaded ZnFe2O4 played a key role on suppressing inverse electromagnetic radiation, eddy effect, simultaneous maintaining moderate magnetic loss ability. Besides, the formed interface of ZnFe2O4/Fe could induce interface polarization relaxation effect at external electromagnetic field, which greatly boosted the effective dielectric loss ability (ε''E). Meanwhile, the interface polarization intensity was controllable by tuning the weight ratio of Fe.

A biomass derived porous carbon for broadband and lightweight microwave absorption.

With the continuous progress of science and technology, the traditional magnetic material is no longer able to meet the new complex electromagnetic (EM) environment due to its high bulk density. Therefore, the novel excellent EM absorber with the feature of thin thickness, low density, broad absorption bandwidth and strong absorption intensity is highly desired. Herein, we fabricated a porous carbon with ultrahigh porosity through a facile KOH activation from biomass waste pumpkin seed shell for lightweight EM wave absorption application. By optimizing the porous structures, the strong absorption intensity of -50.55 dB is achieved at thin thickness of 1.85 mm under low filler content of only 10 wt %. More interestingly, a broad frequency bandwidth of 7.4 GHz could cover the whole Ku band. These outstanding microwave absorption performances, couple with low cost ingredients and ease of fabrication process enable the porous carbon framework as the next generation promising candidate for lightweight and remarkable EM absorber.

Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption.

Currently, electromagnetic (EM) pollution poses severe complication toward the operation of electronic devices and biological systems. To this end, it is pertinent to develop novel microwave absorbers through compositional and structural design. Porous carbon (PC) materials demonstrate great potential in EM wave absorption due to their ultralow density, large surface area, and excellent dielectric loss ability. However, the large-scale production of PC materials through low-cost and simple synthetic route is a challenge. Deriving PC materials through biomass sources is a sustainable, ubiquitous, and low-cost method, which comes with many desired features, such as hierarchical texture, periodic pattern, and some unique nanoarchitecture. Using the bio-inspired microstructure to manufacture PC materials in mild condition is desirable. In this review, we summarize the EM wave absorption application of biomass-derived PC materials from optimizing structure and designing composition. The corresponding synthetic mechanisms and development prospects are discussed as well. The perspective in this field is given at the end of the article.