Tunable Dielectric Performance Derived from the Metal–Organic Framework/Reduced Graphene Oxide Hybrid with Broadband Absorption

Abstract

In terms of microwave absorption, dielectric performance acts vital but has negative characteristics in attenuation and impedance matching. In this study, ZnO/nanoporous carbon (NPC)/reduced graphene oxide (RGO) materials have been fabricated through a simple and valid hydrothermal method derived from Zn metal–organic frameworks (MOFs). By changing the molar ratio of the precursors, the permittivity of the ZnO/NPC/RGO can be calculated, and the greatest balance between energy conservation and impedance matching eventually emerged with the addition of 4 mL of GO. It could be found that, at 14 GHz, a thin sample consisting of 40 wt % ZnO/NPC/RGO in the wax matrix exhibited minimum reflection loss of −50.5 dB with a thickness of 2.4 mm, and with a thickness of 2.6 mm, the effective microwave absorption bandwidth coverage is from 9.6 to 17 GHz. It is worth mentioning that we have also interpreted the relationships between the highest reflection loss values and matching thicknesses. This work not only proposes that ZnO/NPC/RGO samples are able to function as a perfect absorbent with broad frequency bandwidth and strong absorption but also provides better candidates in designing other lightweight microwave absorbents.

Effect of SiC layer on microwave absorption properties of novel three-dimensional interconnected SiC foam with double-layer hollow skeleton

“…It can be seen that the decrease in ε′ is resulted from the increase in ω. This is usually attributed to the polarization relaxation [33]. As described above, the ε′ of the 3D-ISF is significantly lower than that of the ICF, indicating that the as-prepared 3D-ISF has a stronger polarization relaxation ability than ICF.…”

“…Additionally, the thickness of SiC layer has little effect on ε′. It should be emphasized that the complex permittivities of 3D-ISF-I and 3D-ISF-II show multiple fluctuations, which are usually caused by the dipole and interface polarization [33]. In comparison with ICF, 3D-ISF exhibits complex permittivities due to the special dielectric properties of SiC materials [34].…”

Dielectric loss behavior and microwaves absorption properties of TiB2 ceramic

“…The complex permittivity was obtained from a VNA analyzer (N5242A PNA-X, Agilent), where the samples for test were prepared by pressing the mixture of TiB 2 ceramics/paraffin into coaxial ring (inner diameter: 3.0 mm, outer diameter: 7.03 mm). The reflection loss values were calculated by the following equations (1) and (2), according to the classical theory [3,28],…”

“…During the past decade, much effort has focused on the development of high-performance materials for microwaves absorption (MA) [1][2][3]. Conventionally developed MA materials are usually metal/metal oxides including ZnO nanorods [4], Ag nanofibers [5,6], NiCu alloy [7], and complex nanostructures; [8][9][10][11][12] conducting polymers including polyaniline(PANI) [13], poly (3, 4-ethylenedioxythiophene)(PEDOT) [14], and polypyrrole (PPy); [15][16][17][18] carbonaceous materials including reduced graphene oxide (RGO) [19,20], and carbon-nanotube (CNT); [21] and their hybrids including metal oxide/sulfide complexes [22,23], polymer complexes [24][25][26][27], RGO complexes [28][29][30], and CNT complex [31][32][33]. However, most of these reported MA materials cannot be considered to be used under harsh conditions, such as high temperature, high corrosion, high stress, and etc Therefore, searching for a MA material with excellent tolerance under harsh condition is highly desirable, but still a challenge up to date.…”

Facile synthesis of highly conductive MoS2/graphene nanohybrids with hetero-structures as excellent microwave absorbers

“…It should be noted that the preparation of MoS 2 /graphene hybrids with hetero-structures involves the conversion of insulating GO into conductive RGO using reducing agents or high-temperature thermal annealing treatments. 31,32 The conversion process is usually tedious and with some troubles, such as insufficient conductivity recovery, morphological changes, phase transitions, even samples polluted with reducing agents. And the reported preparation of MoS 2 /graphene hybrids with pure GNs is inefficient and highcost, which is not viable from the viewpoint of practical application.…”