Nanoholes in Carbon Sheets via Air-Controlled Annealing for Improved Microwave Absorption

Abstract

Despite carbon materials normally exhibiting good absorption toward microwave radiation, there is still the need to develop facile strategies for further exploring the carbon matrix to achieve stronger and broadened absorbing performance. Here, we report a one-step air-controlled annealing approach to fabricate holey carbon sheets with significantly strengthened microwave-absorbing properties. The obtained metal-free product is barely synthesized from prawn crackers without any additive reagent addition. Both electric field simulations and experiments verify the improved absorbing capability achieved on the derived holey carbon absorbent. The performance measurements demonstrate that its reflection loss reaches −64.1 dB at a thickness of 1.45 mm, and the corresponding absorption bandwidth approaches 5.36 GHz at 1.65 mm, almost covering the whole Ku band from 12.64 to 18.00 GHz. These results overperform most biomass-derived absorbents. Benefiting from this air-modulated nanoscale holey structure, it endows the carbon matrix with higher surface areas associated with richer oxygen functional groups, which facilitates more incident microwaves to be consumed and regulates the dielectric loss of the final product. Meanwhile, the inherited Si components from raw prawn crackers supply more polarization centers, thereby enhancing the absorbing properties. We expect that these can represent a feasible addition to the family of sustainable carbon-based microwave absorbents.

Carbon Nanospheres for Electromagnetic Wave Absorption and Shielding

“…As shown in Figure e,f, the values of ε p ″ of these carbon nanosphere composites are all below 0.2, far less than their corresponding ε c ″ values, indicating that in the studied system, ε c ″ completely dominates the dielectric loss and the role of ε p ″ is very small. In fact, many studies on ε c ″ and ε p ″ of carbon material systems displayed the same findings as this study, namely, ε c ″ has absolute dominance in dielectric loss, in which the carbon materials involved included various hierarchical structures, such as core–shell, ,− yolk–shell, hollow, − and porous. − Table reveals the calculated values of ε c ″ and ε p ″ and the EMW absorbing performances presented in some published reports.…”

Joule-Heating-Driven Synthesis of a Honeycomb-Like Porous Carbon Nanofiber/High Entropy Alloy Composite as an Ultralightweight Electromagnetic Wave Absorber

“…Unlike HCNF/LEA and HCNF/MEA, HCNF/HEA exhibited a high I D / I G ratio (1.24), which may be related to HEA nanoparticles stabilizing the defects in the carbon matrix . In addition, the structural incompleteness of the pore edges can also lead to a large number of unsaturated dangling bonds and defect domains, which can act as polarization centers and cause an uneven charge distribution in the region, thus inducing more polarization loss. , …”

“…35 In addition, the structural incompleteness of the pore edges can also lead to a large number of unsaturated dangling bonds and defect domains, which can act as polarization centers and cause an uneven charge distribution in the region, thus inducing more polarization loss. 30,36 The specific surface area and pore structure of HCNF/HEA were analyzed via the N 2 adsorption−desorption isotherm method. Figure 3c depicts the HCNF/HEA exhibits of typical type I and IV adsorption−desorption isotherms.…”

Entropy engineering enhances the electromagnetic wave absorption of high-entropy transition metal dichalcogenides/N-doped carbon nanofiber composites

“…31 Both lattice distortions in MWSST and carbon defects in NCNF can produce defect polarization during EMW attenuation. 32,33…”