Microwave responses and general model of nanotetraneedle ZnO: Integration of interface scattering, microcurrent, dielectric relaxation, and microantenna.

Based on the unique geometrical structure of nanotetra-ZnO needle (T-ZnO_N), we investigate the microwave responses of T-ZnO_N, including interface scattering, microcurrent attenuation, microantenna radiation, and dielectric relaxation, and build an energy attenuation model. The associated quantitative formula is deduced for calculating the microwave absorption properties of T-ZnO_N/SiO₂ nanocomposite (T-ZnO_N/SiO₂) in the range 8–14 GHz according to the present energy attenuation model. Very good agreement between the calculated and experimental results is obtained in a wide frequency range. The maximum deviation less than 0.5 dB in the range 8–14 GHz is obtained. Using the aforementioned model, we analyze the contribution of microwave responses to the energy attenuation in the frequency range 2–18 GHz, and the results reveal that interface scattering and microcurrent attenuation make the contribution most important. In addition, we calculate the effects of the volume fraction, conductivity, permittivity, needle length of T-ZnO_N, and thickness of T-ZnO_N/SiO₂ on the reflectivity. The results show that the microwave absorption is evidently dependent on these effect factors, and the optimal microwave absorption band and the strongest microwave absorption peak of T-ZnO_N/SiO₂ would appear when these physical parameters are changed. [ABSTRACT FROM AUTHOR]