Science of Ceramic Processing and Surface Treatments

This study presents a new design of a reduced volumetric ultra‐wideband (UWB) antenna using innovative dielectric based on the use of geopolymer material which is safe and eco‐friendly. The created antenna is intended to radiate in the air. The impedance mismatch due to interface dielectric/air at the aperture of the antenna imposes to choose dielectric material with an appropriate permittivity value. In this study, the authors focus on the experimental protocol that they use to elaborate a dielectric material with suitable dielectric properties over an UWB domain. An experimental phase of dielectric properties assessment is also described. The conceived antenna is inspired by K‐antenna which constitutes the starting point of the proposed new antenna design, particularly because of their small dimensions. The antenna is intended to operate in a frequency band ranging from 300 MHz to 3 GHz. The authors demonstrate that the use of an appropriate innovative dielectric material like a geopolymer is an efficient way to reduce the antenna size. Furthermore, the behaviour of the antenna filled with geopolymer is validated using experimental results.

\nAt the macroscopic scale, such media as rocks or ceramics can be seen as homogeneous continuum. However, at the microscopic scale these materials involve sophisticated micro-structures that mix several phases. Generally, these micro-structures are composed by a large amount of inclusions embedded in a brittle matrix that ensures the cohesion of the structure. These materials generally exhibit complex non linear mechanical behaviors that result from the interactions between the different phases. This paper proposes to study the impact of the diffuse damages that result from the thermal expansion mismatch between the phases in presence. The Discrete Element Method (DEM) that naturally take into account discontinuities is proposed to study these phenomena.\n

The first-order lattice distortion undergone by β-As2Te3 around 200 K results in a cycling effect on its transport properties.

This study presents a new design of a multi-band filter-antenna subsystem dedicated to high-speed wireless communications at 60 GHz. The objective is to design the subsystem as a monolithic object realized with a ceramic material. The broadband antenna is composed of a conical horn acting as a primary source for illuminating a reflect-array. The 9-GHz spectrum, which covers the unlicensed 60-GHz band, is divided into four channels of 1.65 GHz. In this paper, the primary source and the four bandpass filters are designed and integrated together. Keywords— Antenna; co-design; filter-antenna; microwave filter; stereolithography.

Solution precursor plasma spraying (SPPS) is an innovative process for obtaining finely structured coatings from metallic salt solutions. Lanthanum and zirconium precursors were studied to understand their influence on lanthanum zirconate (La2Zr2O7) synthesis by SPPS. Thermal analysis revealed that the nature of the precursor and the solvent affected mixture decomposition by changing the decomposition temperature. The surface tensions of precursor solutions in various media were investigated and revealed the influence of the nature of the counter-cation. Different solutions of precursor mixtures were used to obtain La2Zr2O7 splats on metallic substrates. A decrease in solution surface tension led to an increase in splat size. Coating mechanisms by SPPS are governed by the nature of the precursors and solvents.