Magnetic and dielectric materials can be blended to enhance absorption properties at microwave frequencies, although the materials may have relatively weak attenuation capabilities by themselves. The specific goal of this work is to enhance microwave absorption properties of materials with interesting dielectric behavior by blending them with magnetic materials based on transition metals. The synthesized Mn_1−xZn_xFe₂O₄ (x = 0.0 and 1.0) spinel ferrite nanoparticles (MZF NPs) were blended with commercial multi-walled carbon nanotubes (MWCNTs) in various proportions with a binder matrix of paraffin. This simple and efficient process did not cause a significant variation in the energy states of MWCNTs. MZF NPs were synthesized with a citric acid assisted sol–gel method. Their electromagnetic characteristics and microwave absorption properties were investigated. These properties were derived from the microwave scattering parameters measured via the transmission line technique by using a vector network analyzer (VNA) in conjunction with an X band waveguide system. The return loss (RL) values of the samples were obtained from the electromagnetic constitutive parameters (permittivity and permeability). The results indicate that the minimum RL value and the bandwidth change significantly with the amount of ferrite material in the blend. These results encourage further development of MWCNTs blended with ferrite nanoparticles for broadband microwave applications.

This study presents a new dual‐band terahertz absorber (DBTA) with ease of production consisting of a metallic base plane of a certain thickness, a dielectric layer on this plane, and a hexagonal metallic metasurface structure. The proposed absorber exhibits absorption band peaks above 99% at two distinct frequencies (7.51 and 8.08 THz). The absorption origin is explained as a dual‐band response using the LC resonance and dipolar response. In this way, the presented absorber facilitates production by improving absorption responses with a much simpler structure, unlike studies with complex geometries. The proposed dual‐band absorber results in sensitivity to the polarization of the incident light. Thus, it also makes the proposed structure very helpful for manipulating wave polarization and detecting waves with particular polarization. The hexagonal structure of the absorber is scaled to millimeter dimensions, and its transformation into another dual‐band absorber that can also operate in microwave frequency regions. Similarly, the hexagonal structure is transformed into a circular structure with the same geometric dimensions, and a different dual‐band absorber is obtained in the terahertz (THz) region. Moreover, the proposed concept can be extended for various applications such as bolometric sensing, thermal imaging, energy harvesting, sensing, and selective thermal emitters.

Reflective polarization conversions with a simplistic design of an ultrathin, single-layered, and multi-functional anisotropic metasurface as a polarization converter is utilized for Ku- and K-band applications. The designs with two substrate thicknesses (0.095λ0 and 0.069λ0, respectively) are capable of a cross-polarization converter (CPC) and a linear-to-circular (LTC) polarization conversion. The design with 0.095λ0 thickness achieves a CPC between 17.96 and 26.90GHz with the efficiency of more than 90% and a relative bandwidth of 40% under normal incidence. It maintains angular stability by altering the oblique incidence angles up to 300 with greater than 80% of the PCR in the K-band. Meanwhile, an LTC in two frequency bands, 10.30-10.53GHz and 28.65-29.70GHz, is also numerically demonstrated. The second design with 0.069 λ0 thickness provides a CPC above the PCR value of 87% in the frequency range from 10.46-23.05GHz (covering the entire Ku- and part of the K-band) with angular stability of 40 above the PCR value of 80%. In the meantime, an LTC with relative bandwidth of 75% in the frequency range from 9.53-9.79&24.74-25.27GHz is numerically revealed. These polarization converters exhibit relatively good performances of facile structure and multi-functional properties, which can be useful in Ku- and K-band applications.