Directed Growth and Microwave Absorption Property of Crossed ZnO Netlike Micro-/Nanostructures

Abstract

Three-dimensional ZnO micro/nanorod networks were synthesized through the direct evaporation of metal zinc and graphite powders in Ar and O 2 at 910 °C without any catalyst. The micro/nanorod networks of as-synthesized ZnO were characterized by using scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. The branches within one network show very regular cross orientation. The nanorods follow a growth direction [0001]. Mircrowave absorption properties of the ZnO netlike structures have been investigated in detail. The reflection loss (RL) of the netlike structures and nanotetrapod-shaped ZnO were calculated by using the relative complex permeability and permittivity. And the value of minimum RL for the composite with 50 vol % ZnO netlike structures is -37 dB at 6.2 GHz with a thickness of 4.0 mm. These results provide a wide insight for the netlike structure ZnO as desirable materials for the fabrication of micro/nanoscale functional electromagnetic shield devices.

Electromagnetic Wave Absorption Properties of Nanoscaled ZnO

“…13 (Li et al, 2010). It can be seen that CNTs and T-ZnO nanostructures concentration has an obvious effect on microwave absorption properties.…”

“…Also, the Fig. 5b indicates the ZnO microrods with a rough surface, possibly due to the competition between surface energy and strain energy (Li et al, 2010).…”

Synthesis and Excellent Microwave Absorption Properties of ZnO/Fe3O4/MWCNTs Composites

“…The uniform coating of Ni nanoparticles considerably enhances the interfacial polarization, dielectric properties, and magnetic loss of ZnO@Ni; hence, the MA properties of this material are remarkably improved. Zhang et al 25 have reported that ZnO net-like micro/nanostructures/para±n composites present a high performance in MA. Liu et al 26 reported that ZnO@MWCNTs show a re°ection coe±cient of approximately À20 dB at room temperature; this nding indicates that ZnO induces a synergistic e®ect in enhancing MA.…”

Coprecipitation Synthesis of Fe-doped ZnO Powders with Enhanced Microwave Absorption Properties

“…[4][5][6] In order to further improve the microwave absorption performance of ZnO, scientists have made much e®orts and their interest is mainly focused on the two aspects. On the one hand, ZnO with unique microstructure is fabricated, such as tetra-needlelike ZnO whiskers, 6 ZnO nanorods, 9 ZnO nanotrees, 14 ZnO dendritic nanostructures, 15 nanoneedlelike ZnO, 16 crossed ZnO netlike micro-/nanostructures, 17 etc. For example, Liu et al fabricated nanoneedlelike ZnO via a facile combustion synthesis route and the materials exhibited enhanced permittivity and multi-region microwave absorption in the X-band at elevated temperature and the minimum re°ection loss (RL min ) reached À44 dB.…”

“…The value of RL min for the composites with 50 vol.% ZnO netlike structures was À37 dB at 6.2 GHz with a thickness of 4.0 mm. 17 On the other hand, ZnO is complexed or hybridized with other components to fabricate composites, such as ZnO/reduced graphene oxide (ZnO/ RGO), 4,18,19 ZnO/multi-wall carbon nanotubes (ZnO/MWCNTs), 5,20 ZnO/Fe 3 O 4 composites 21,22 etc. For instance, Wu et al fabricated 3D ZnO/ RGO nanocomposites using a two-step reduction process and found that the composites exhibited excellent microwave absorbing properties, i.e., the maximum e®ective absorption bandwidth of RL lower than À10 dB could reach 6.4 GHz when thē ller loading was 10 wt.% and the thickness of the absorber was 2.5 mm.…”