arXiv subjects

Jaume Calvo-de la Rosa

Publications and source records attributed to Jaume Calvo-de la Rosa.

3 recordsLinked to original sources

arXiv2025

Radar shielding experiments by composite bilayer magnetic systems

An experimental strong increase of the reflection loss (from 25 up to 35 dBs) and an extension of the absorption bandwidth up to 20% is measured in a set of novel functional bilayer systems. We focus our work on studying the samples in an anechoic chamber under far-field real radar conditions. Each layer consists of a composite material, typically a dielectric matrix filled with random anisotropy hexaferrite and soft metallic materials (powder or wires). Combining the two types of materials into a submillimetric bilayer structure has shown unprecedented improvements in microwave absorption capacities compared to the former absorption of each layer. The capacity to improve the shielding behavior is strongly related to each layer permittivity, permeability, and thickness leading, therefore, to a strong control over the design of novel materials for stealth applications.

cond-mat.mtrl-sci↗

arXiv2024

Microwave absorption in barium hexaferrite nanocomposites with random anisotropy

This work reports experimental evidence of random magnetic behavior observed in modified barium hexagonal ferrites. We observe a significant transition in the magnetic properties of this system when divalent cations (Ni2+, Cu2+, Mn2+) are incorporated into the structure and give rise to a magnetic nanocomposite. Such introduction randomly occurs throughout each sample and creates conditions for such materials to behave as random anisotropy magnets. We verify the occurrence of such behavior in our samples by fitting the magnetization in approaching saturation to the corresponding theoretical model. We therefore analyze the microwave absorption capacities of random anisotropy magnets in the GHz range and predict large and broad absorption signals under certain conditions. The findings presented here postulate, for the first time, ceramic materials as promising random anisotropy magnets and underline their potential as microwave absorbers, in good agreement with recent theoretical models.

cond-mat.mtrl-sci↗

arXiv2024

Experimental radar absorption in high-filling factor magnetic composites

The electromagnetic properties and microwave absorption capabilities are studied in an anechoic chamber under real radar conditions for mono and bilayer composite samples consisting of a polymeric matrix and a magnetic powder filler, either metallic or ceramic. The effect of the filler type and the filling factor is investigated. The results demonstrate exceptional broadband microwave absorption, making these materials highly suitable for stealth technology applications. The experimentally measured absorptions reach -40 dB, while model-based predictions suggest that these systems could overpass the barrier of -50 dB. The experimental results are supported by models, both for single and bilayer systems.

cond-mat.mtrl-sci↗