Oriented Polarization Tuning Broadband Absorption from Flexible Hierarchical ZnO Arrays Vertically Supported on Carbon Cloth

Abstract

A novel strategy is used to design large‐scale polarized carbon‐based dielectric composites with sufficient interaction to electromagnetic waves. Highly uniform polar zinc oxide arrays are vertically grown on a flexible conductive carbon cloth substrate (CC@ZnO) via an in situ orientation growth process. Anion regulation is found to be a key factor to the morphology of hierarchical ZnO arrays including single‐rod, cluster and tetrapod‐shaped. As a typical dielectric loss hybrid composite, the electromagnetic parameters of the CC@ZnO system and charge density distribution in polarized ZnO rods confirm that the 3D intertwined carbon cloth is used as a conductive network to provide ballistic electron transportation. Moreover, the defect‐rich ZnO arrays are well in contact with the CC substrate, favoring interface polarization, multiscattering, as well as impedance matching. Surprisingly, the efficient absorption bandwidth of the CC@ZnO‐1 composite can reach 10.6 GHz, covering all X and Ku bands. The oriented ZnO possesses oxygen vacancies and exposure to a large amount of intrinsic polar surfaces, encouraging the polarization behavior under microwave frequency. Optimized CC@ZnO materials exhibit fast electron transportation, strong microwave energy dissipation, and superior wide absorption. The results suggest that the CC@ZnO composites have promising potential as flexible, tuning, and broadband microwave absorbers.

Galvanic Replacement Reaction Involving Core–Shell Magnetic Chains and Orientation‐Tunable Microwave Absorption Properties

“…Stimulated by alternating EM fields, the electron hopping effects can be exacerbated, which can cause conductive loss and thus dissipate microwave energy. [63] Similar with PVDF composites containing CNTs and magnetic metals, [64,65] the free electrons present in the bimetallic chains lead to absorption of the incident EM waves. Third, because of the numerous interfaces of the core-shell structures, charge accumulation can occur between interfaces, thus resulting in energy scattering and intensive interfacial polarization loss irradiated by EM waves to attenuate EM energy, [10] as proved in Figure S7a-c, Supporting Information.…”

Hierarchical Carbon Fiber@MXene@MoS2 Core‐sheath Synergistic Microstructure for Tunable and Efficient Microwave Absorption

“…The layer spacing of Ti 3 C 2 T x is about 0.99 nm, while MoS 2 layers grow tightly on Ti 3 C 2 T x and orient randomly with bending feature (Figure 3d). Furthermore, a prominent and wide peak at 25.5° in the X-ray diffraction (XRD) pattern of CF is ascribed to integrated microfibers of carbon materials (Figure 4a), [17] which also can be found in that of CM but sharply weakened in that of CMM. Ti 3 C 2 T x displays four peaks at 8.9°, 18.2°, 34.2°, and 60.6°, corresponding to the (002), (006), (0010), and (110) crystal planes, respectively, [42,43] which stay invariably in that of CM and become weak or even disappear in that of CMM.…”

MOF-Derived Ni1−xCox@Carbon with Tunable Nano–Microstructure as Lightweight and Highly Efficient Electromagnetic Wave Absorber

“…Related electromagnetic parameters were measured via a vector network analyzer (VNA, HP8510C, Agilent, USA) over the 2-18 GHz range. Related reflection loss curves are calculated by the following equations [30,31]:…”