Exploration of Twin‐Modified Grain Boundary Engineering in Metallic Copper Predominated Electromagnetic Wave Absorber

Abstract

High density and skin effect restrict the research progress of metal predominated electromagnetic wave absorbing (EMA) materials. Although some works try to solve it, they do not focus on the metal itself and do not involve the optimization of the active site of the inherent defects of the metal. In this work, the modulation of morphology, composition, interface, defects, and conductivity is achieved by adjusting the ratio of copper salt to reducing agent chitosan. Uniquely, the appearance of twin boundaries (TBs) accelerates the ability of the homogeneous interfaces to transfer charges, resists the oxidation of metal Cu0, keeps the high electric conductivity of Cu0 nanoparticles, and enhances the conduction loss, which provides a boost for electromagnetic wave dissipation. As a result, the metal Cu0 predominated absorber (Cu‐NC (N‐doped carbon)−10,) exhibits an ultra‐width effective absorption band of 8.28 GHz (9.72–18.00 GHz) at a thickness of 2.47 mm and the minimum reflection loss (RL) value of −63.8 dB with a thickness of 2.01 mm. In short, this work explores the EM regulation mechanism of TBs compared with grain boundaries (GBs), which provides a new insight for the rational design of metal predominated EMA materials.

Regulated electron migration in sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly boosted electromagnetic wave absorption

“…The insertion of Fe 3 O 4 signicantly increases the activation energy for electrons to hop across bulks and layers; hence the electron hopping behaviors are hindered. 46 The decreasing conductivity shown in Fig. S6 † conrms this process, and compared with m-Ti 3 C 2 , MTF-1 shows a declining conductivity by several orders of magnitude.…”

“…41,42 High 3 ′′ denotes a desirable ability to dissipate EM energy but is hardly conducive to impedance matching, which results in the total reection of the EM wave. [43][44][45][46] Pure Fe 3 O 4 nanoparticles exhibit utterly low 3 ′′ on the contrast (Fig. S3a †), revealing their negligible dielectric loss capacity.…”

Exploring the Ni 3d Orbital Unpaired Electrons Induced Polarization Loss Based on Ni Single‐Atoms Model Absorber

“…The polarization relaxation which is studied by using Debye theory, shown in distorted Cole-Cole semicircles appears on Debye relaxation curves in Ni-SAs3/NC, indicating significant polarization exists (Figure 4b, Figure S15, Supporting Information). [30] However, for the second stage, from the results of Ni-NPsx/NC (x = 1, 2, and 3), the value of the complex permittivity gradually increases with the further addition of Ni species, exhibiting the exact opposite regular variation from the first stage. Especially, the value of Ni-NPs3/NC reaches a new height (ε': 45.5, ε": 38.9).…”

“…The designed ligand strategy consists of anchoring the ligand sites to the support groups, and the amino (NH 2 ) and hydroxyl (OH) functional groups in chitosan act as "claws" to capture and anchor the mononuclear metal precursors (Figure 1a,b). [30][31][32] The formation of polar Ni-N x is fixed by strong chelation between metal ions and ligand sites and further driven by thermodynamic factors, which effectively prevents migration and agglomeration between monoatoms. Uniformly dispersed monoatomic active metal centers can be interconnected with each other by the ligand linkage function of the conductive carbon support for intra-group "electron exchange" effects.…”

“…First, both the magnitude and the variation of the permeability tangent (tan δ µ ) are much smaller than that of permittivity tangent (tan δ ε ), indicating that the magnetic loss plays only an auxiliary role in the overall electromagnetic loss mechanism (Figure S13, Supporting Information). [30,46] Hence, the weak magnetic loss forces us to turn to the investigation of the complex permittivity (ε', ε"), which is directly related to the dielectric loss.…”