Systems and Applied Mechanics laboratory

Al Marsá, Tunisia

Systems and Applied Mechanics laboratory

Al Marsá, Tunisia
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Moutalibi N.,University of Carthage | M'chirgui A.,University of Carthage | M'chirgui A.,Systems and Applied Mechanics laboratory | Noudem J.,National Engineering School of Caen
Physica C: Superconductivity and its Applications | Year: 2010

The YBa 2Cu 3O 7-x (Y123) textured bulk superconductors with various amounts of nanometer alumina particles were fabricated by a seeded infiltration and growth process. The addition of nanometer alumina was found to be effective for an improvement of the superconducting properties. The critical current density (J c) values were increased twice in self field with a slight addition amount of nanometer alumina particles (maximum J c at 0.01 wt.% alumina addition). The present work suggests that the use of insulating inclusions in the nanometer sub-scale can stabilize the flux-line lattice and greatly enhance the pinning capabilities of the infiltrated samples. No refinement of Y211 particles was observed with alumina addition. The J c improvement by nanometer alumina inclusions is likely rendered to the insulating nano-pinning centers that have been successfully embedded into superconducting Y123 matrix. On the other hand, we examined the effect of the pinning centers size on the superconducting properties of infiltrated YBCO bulk samples. To this effect insulating nano-pinning centers with two different size distributions has been successfully incorporated within YBCO matrix of bulk superconductor by slightly doping with nano-particle alumina dispersions. Two alumina nano-particle dispersions with mean size diameters of about 20 nm and 130 nm were used. It was shown that the size of the pinning centers can affect considerably the J c performances and the pinning mechanism. © 2010 Elsevier B.V. All rights reserved.


Moutalbi N.,University of Carthage | Ouerghi A.,University of Carthage | M'chirgui A.,University of Carthage | M'chirgui A.,Systems and Applied Mechanics Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2011

The influence of pinning centers size on the superconducting properties was investigated. Through the addition of three batches of ZrO 2 nano-particles with mean size of D 1 = 13 nm, D 2 = 21 nm, and D 3 = 85 nm, we have succeeded in incorporating effective artificial pinning centers within the YBCO matrix of the bulk superconductor. An enhancement in the flux pinning and an improvement in the critical current densities (transport critical current density J ct and magnetic critical current density J cm) were achieved. The results indicate that slight inclusions of ZrO 2 can greatly enhance the flux pinning capability of samples. Comparative analyses of the critical current densities and the resulting pinning force F p for the three diameters have shown that pinning centers with finer size are much more efficient than those with a size larger than the coherence length ξ. © Springer Science+Business Media, LLC 2010.


Moutalbi N.,University of Carthage | M'Chirgui A.,University of Carthage | M'Chirgui A.,Systems and Applied Mechanics Laboratory | Noudem J.G.,CNRS Crystallography and Material Science Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2011

We have conducted an experimental study on the effect of the pinning centers size on the superconducting properties in textured YBCO samples. In this work, we investigated the effectiveness of the addition of an insulating inclusion on the superconducting and magnetic properties of textured YBCO bulk materials. The purpose of this study was to ascertain whether the size of artificial pinning centers is able to affect the superconducting properties of our samples. To this effect insulating nano-pinning centers with two different particle size distributions of about 20 nm and 130 nm have been successfully incorporated within YBCO matrix by slight doping with nano-particle alumina dispersions. The microstructure and superconducting properties were investigated by scanning electron microscopy (SEM) and SQUID. The results indicate that slight inclusions of nano-alumina can enhance the flux-pinning capability of samples. This study underlines the dependence of the pinning force on the size of the pinning centers. © Springer Science+Business Media, LLC 2010.


Chafra M.,Systems and Applied Mechanics Laboratory | Smaoui H.,Systems and Applied Mechanics Laboratory | Ben Arfa D.,Systems and Applied Mechanics Laboratory
Journal of Composite Materials | Year: 2010

The purpose of the present study is to propose a strategy for identifying the mechanical characteristics of fibers and the damage in composite materials, based on an inverse method coupled with homogenization. It consists, in a general and systematic way, in coupling a homogenization procedure chosen by the user, with an appropriate numerical optimization algorithm. The method can be interpreted as a procedure for passage from macroscopic to mesoscopic scale. In this respect, it is shown that our method is capable of providing estimates of mesoscopic properties that are difficult to obtain experimentally. The proposed identification method is applied to examples of damaged and undamaged composites including those made of woven and unwoven natural fibers of Alfa and a polyester resin matrix. Identification results obtained by the proposed inverse method are compared to data taken from the literature to show its effectiveness. © The Author(s), 2010.

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