Ferrite nanoparticles with a composition of ${\text{Ni}}_{0.5}{\text{Zn}}_{0.3}{\text{Co}}_{0.2}{\text{Fe}}_2{\text{O}}_4$ were prepared by a coprecipitation method. The sample obtained after treating at appropriating conditions had almost equal real permeability and permittivity, of $4.8+\text{j}0.15$ (loss $\text{tangent}\sim 0.04$ ) and $4.9+\text{j}0.10$ (loss $\text{tangent}\sim 0.018$ ), respectively, over 100 to 500 MHz. This material had a refractive index n of close to 5 and a reduced impedance $\text{Z}/{\text{Z}}_0$ of close to 1. These properties make the material useful to the design of miniaturized antennas at very high frequency-ultra high frequency (VHF-UHF) (100–500 MHz) bands.

This paper reports on dielectric properties of ternary mixtures involving sodium chloride (NaCl) and sucrose (C₁₂H₂₂O₁₁) dissolved into water (H₂O). Broadband electromagnetic characterizations of such mixtures at various concentrations were performed, evidencing a dual behavior made of conductive effects at low frequencies and dipolar relaxation at microwave frequencies. Conductive and dielectric properties resulting from these both effects were integrated into predictive models for variations of Cole–Cole model parameters. Based upon this modelling, an innovative microwave-based sensor able to retrieve concentrations of both sodium chloride and sucrose in ternary aqueous solutions was introduced, designed, realized and assessed. The proposed sensor shows an error lower than 5.5% for concentration ranges of 0 to 154 mmol/L for sodium chloride and 0 to 877 mmol/L for sucrose.

This article reports on an isotropic model of the magnetic susceptibility based on an average field theory and proposes to predict the dynamic behaviors of powder magnetic materials. It was essentially built around a so-called effective demagnetizing factor capable of taking the particle shapes into account. So, for a population of randomly distributed particles of anisotropic shapes like, for instance, needles or flakes, we show that the effective demagnetizing factor of this population of particles can be significantly lowered with regard to the well known value of 1/3 classically used to represent the isotropy state. This phenomenon is interpreted as the natural tendency of particles to form clusters to which a moving demagnetizing factor must be assigned. Taking then the aggregation process of particles into account, the ability of the model to predict the dynamic properties of many composite magnetic materials is successfully demonstrated. Our development is illustrated by experimental results concerning a nickel–zinc ferrimagnetic (Ni0.7Zn0.3Fe2O4) powder.

In this article, we propose to apply 3-D printing technology to the design and realization of honeycomb microwave absorbers. First, printability of simple honeycomb structures, made of a lossy dielectric material, was evaluated and validated by measurement in the 2–18 GHz frequency band. Effective dielectric properties of honeycomb structures with different dimensions are also discussed. Then, the interest of 3-D printing technology was highlighted by the design, fabrication, and measurement of a multiscale honeycomb absorber that can significantly increase the relative bandwidth. The 3-D printed honeycomb absorbers are compared with others technologies. The potential of this technology was also illustrated by the fabrication and measurement of a pyramidal honeycomb absorber that demonstrates an absorption level of more than 22.9 dB over the 2–18 GHz frequency band.