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Nabeul, Tunisia

Tlili B.,National Engineering School of Tunis | Tlili B.,Arts et Metiers ParisTech | Nouveau C.,Arts et Metiers ParisTech | Walock M.J.,National Engineering School of Tunis | And 3 more authors.
Vacuum | Year: 2012

Cr/CrN/CrAlN, CrN/CrAlN and Cr/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200°C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also prepared for comparison purposes. The structural and morphological properties of PVD layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS + WDS microanalyses, stresses were determined by the Newton's rings methods using the Stoney's equation and surface hardening and hardness profiles were evaluated by micro hardness measurements. The XRD data and HRTEM showed that both the Cr/CrN, CrN/CrAlN and Cr/CrN/CrAlN multilayer coatings exhibited B1NaCl structure with a prominent reflection along (200) plane, and CrAlN sub-layer microstructures composed of nanocrystallites uniformly embedded in an amorphous matrix. The innovation of this work was to use the thickness of three different coating types to determine the thermal properties. Furthermore, an empirical equation was developed for the thermal properties variations with temperature of AISI4140 steel coated with different multilayer coatings. The thermal conductivity of CrAlN single layered was lower than the multilayer and the bulk material AISI4140. Moreover, the influences of structure and composition of the multilayer coatings on the thermal properties are discussed. The thermal conductivity of nanoscale thin film is remarkably lower than that of bulk materials because of its various size effects. © 2011 Elsevier Ltd. All rights reserved. Source


Ghrib T.,Photothermal Laboratory | Ben Kraiem M.S.,University of Sfax | Bordel C.,CNRS Material Physics Group | Yacoubi N.,Photothermal Laboratory | Cheikhrouhou A.,University of Sfax
EPJ Web of Conferences | Year: 2012

In this paper, we present a thermal properties investigation of giant magneto-resistance Mn/Fe layers as a function of Mn thickness using the Photothermal Deflexion Technique (PTD). We observe that the thermal resistance reaches its maximum for a Mn critical thickness corresponding to the antiparallel ferromagnetic coupling. © Owned by the authors, published by EDP Sciences, 2012. Source


Ghrib T.,Photothermal Laboratory | Yacoubi N.,Photothermal Laboratory
Journal of Physics: Conference Series | Year: 2010

In this work we have studied the nitriding effect for the 42CrMo4 steel on the evolution of their thermal and mechanical properties. The thermal properties are determined by the "Photothermal Deflection technique" method. It was shown that the thermal conductivity as well as the thermal diffusivity decreases if the nitrogen fraction in steel increases conversely the microhardness increases with the growth of the nitrogen rate. After, we have correlated the thermal and mechanical properties with an empirical equation that permits to determine the microhardness without its measure. © 2010 IOP Publishing Ltd. Source


Dhouib A.,Photothermal Laboratory | Yacoubi N.,Photothermal Laboratory
Applied Physics A: Materials Science and Processing | Year: 2014

Photothermal deflection which is a non-destructive technique is widely used to study defects in materials. However, high spatial resolution and high sensitivity are required to detect them. To validate the theoretical model that we developed in the case, the sample is immersed in a paraffin oil-filled cell and heated with a laser beam of a diameter less than the dimensions of defects and of power 2 mW instead of several 100 mW power frequently used. Our model was tested on a part of a circuit board card having copper strips spaced periodically and embedded in the resin. The experimental curves of amplitude and phase variations according to displacement of the sample are in good agreement with the corresponding theoretical ones; and their coincidence permit us to deduce several parameters such as the width of the copper and resin strips, their thicknesses and their thermal properties. These comparisons allowed also to detect some anomalies in the structure such as inhomogeneity in the width, the shape and the thicknesses of copper and resins strips. © 2014 Springer-Verlag Berlin Heidelberg. Source


Ktifa S.,Photothermal Laboratory | Saadallah F.,Photothermal Laboratory | Yacoubi N.,Photothermal Laboratory
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2012

The goal of this work is to investigate the influence of the anodization current on the optical properties of porous alumina layer, on which crystalline silicon films are deposited by a PECVD technique. Porous alumina layers were grown by a simple electrochemical anodization method, varying the anodizing voltage between 200 to 400 mV. The structural properties of the Si/Al 2O 3 films were studied by using Raman spectroscopy and XRD. Photothermal deflection spectroscopy (PDS) is used to determine the gap energy and the optical absorption spectrum by comparing the experimental amplitude of the photothermal signal to the corresponding theoretical one. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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