Mohamed Wajdi BEN AYOUB, Ph.D.

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Mohamed Wajdi BEN AYOUB soutiendra sa thèse le 17 juillet 2018 à 10H au CETIAT à Villeurbanne, intitulée "Measurement devices of dielectric constants in wet materials. Towards a better traceability of the measurement of the moisture in solids."

Le jury se compose de :
Jocelyn PARÉ IARC-Université de Moncton Rapporteur
Damienne BAJON ISAE-SUPAERO Rapporteur
Hugues GIOVANNINI Université Aix Marseille Examinateur
Marc HIMBERT CNAM Examinateur
Essam HEGGY CNRS / NASA Jet Propulsion Examinateur
Pierre SABOUROUX Université Aix Marseille Directeur de thèse
Éric GEORGIN CETIAT Co-encadrant de thèse
Jean-François ROCHAS WAVE CONCEPT Membre invité
Luc ERARD LNE Membre invité
Catherine POIRIER CTMNC Membre invité

Abstract

This thesis is part of a European research project called METfnet (Metrology for Moisture in Solids).
In industry, the electrical sensors for measuring the water content in the solids are generally mono-frequency and the operating frequency is chosen arbitrarily.
The sensitivity to the water content depends on the type of material and the existing water bounds. On the one hand, the dielectric relaxation frequency of water in the liquid state is located in the microwave band. On the other hand, the dielectric relaxation frequency of the bound water depends on the material, but it is known that it’s situated in the radio frequency band.
Based on this hypothesis, the aim of this thesis is to analyze the frequency sensitivity with respect to water bonds in solids by using as an intermediate parameter the complex dielectric permittivity.
In the first phase of the work, we validate metologically two instruments : capacitive and coaxial, both of them are developed at CETIAT for measuring the dielectric constant. The two measuring cells were validated to measure the complex dielectric permittivity of liquids, solids and wet products in the [1 MHz - 2 GHz] band and a comparison with the EpsiMu® tool developed by the Fresnel Institute was carried out.
In the second phase, we experimentally study wet materials by coupling electromagnetic characterization with the thermo-coulometric method, which selectively measures and distinguishes existing water bounding forms in a solid.
At the end of this phase, a parametric study on the complex dielectric spectrum was carried out to lead to the identification of sensitivities with respect to the existing water fractions.
This study was applied to a type of industrial cardboard, kaolinite clay and some monohydrate products such as α-D-Lactose and calcium oxalate.