Université du Littorale Côte d’Opale, France
Talk: Impedance spectroscopy of Lead-free ferroelectric materials for environmentally friendly capacitors applications
Abstract: The study of dielectric and ferroelectric materials has led in recent years to important technological advances in electronics. The development of components such as resonators, capacitors, sensors, memories, tunable microwave devices…, has largely contributed to the developments and innovations in computer science, microelectronics and telecommunications (satellite communication, mobile telephony,…) both in the military and civilian fields. Currently, with the intensive development of transmission systems and portable electronics in general, an important need for high-frequency tunable components and multifunctional devices has arisen, with increasingly high technical requirements in terms of integration and miniaturization for more efficient electronic microdevices. Therefore, fundamental and applied research in materials is an important objective for the future. The current requirements are twofold: a very strong integration of components and a rise in frequency caused in particular by the increasing congestion of the allocated frequency bands. New solutions are therefore to be considered through the search for new materials and/or new structures.
Today, ceramic capacitors are one of the most widely used forms of capacitor used in electronic equipment. With the progress of high-frequency technologies, the dielectric properties of materials used in electronic components, such as telecommunication devices, are of importance for satisfying conditions on the quality factor Q = 1/tgδ [1-2]. In this way, high-frequency systems for telecommunications have attracted great interest. Lead-based ferroelectric ceramics, such as Pb(Zr,Ti)O 3 (PZT), have attracted worldwide research interest due to their high dielectric performance. However, it contains lead in regards with the European directive Restriction of Hazardous Substances, 2002/95/CE (RoHS)…
Accordingly, it is now necessary to implement materials without these prohibited substances, and presenting low losses, high dielectric permittivity and relatively stable properties in frequency and temperature. In particular, Barium titanate (BaTiO 3 ) material has good dielectric properties, which make it the most used base material to elaborate high dielectric permittivity capacitors. Also, the strontium titanate (SrTiO 3 ) material is interesting because it presents low dielectric losses at high frequency. To improve the dielectric properties of these materials, it is possible to make different substitutions at their A and B sites , allowing them to respond to the required specifications, while developing ecological capacitors. This work is part of an international context that aims at exploiting the physical properties of ferroelectric materials for tunable and environmentally friendly capacitor applications.
Université du Littoral Côte d’Opale, France
Talk: Measurement and Analysis of electrochemical noise in Li-ion batteries
Biography: Gérard Leroy is a professor at the University of Littoral Côte d'Opale, France. He obtained a doctorate degree from the University of Littoral Côte d’Opale, France, in 2002. He carries out his research in the Dynamics and Structure of Molecular Materials Unit.
Abstract: Electrochemical noise measurements have been applied to electrochemical systems exhibiting stochastic behavior. The standard area of study that benefits from this stochastic analysis is that of localized corrosion modes such as pitting and crevice corrosion. The application of electrochemical noise measurements to battery systems, although rare, has recently become more popular. This contribution presents electrochemical measurement benches and establishes a method for analyzing electrochemical voltage noise data for Li-ion batteries.
Ruhr-Bochum University, Germany
Talk: Solvent effects in shape memory polymers: Experiments and computer simulations
Biography: Fathollah Varnik received his PhD in theoretical physics at the University of Mainz, Germany. After three postdoctoral years in France (ENS Lyon and CECAM) he became a research group leader at the Max-Planck Institute for Iron Research in Düsseldorf (2004-2008). In 2007, he received habilitation (Venia Legendi) from RWTH-Aachen, Germany. In 2008, he joined the newly founded Interdisciplinary Centre for Advanced Materials Simulation (ICAMS) at the Ruhr- University Bochum, where he later received professorship at the faculty of mechanical engineering (2017). Research interests of Fathollah Varnik cover a broad range including metallic glasses, polymers as well as fluid dynamics. In the years 2010-2015, his research unit made major contributions to the development of lattice-Boltzmann based models to study nano-fluidic phenomena. Since a few years, he has been also working on modelling gas flow through packed beds and combustion via a combination of the lattice Boltzmann method and the phase field approach.
Abstract: Shape memory materials find a large variety of applications ranging from solar panels and wind foils to stents, the latter used to widen sclerotic coronary arteries. Among these, metallic shape memory alloys (SMAs) are often used as mechanical switches, whereas shape memory polymers (SMPs) show promising biocompatibility potentials and therefore find increasing applications in biomedicine. Common to all these materials is their ability to recover a programmed shape via activation of a switching mechanism, e.g., heating above a certain threshold temperature. The recovery process in SMAs is a diffusionless martensitic phase transformation. The shape memory effect in polymers, on the other hand, has an entropic origin: Upon heating above the glass transition temperature, stretched polymers, which had been immobilized via cooling to room temperature, become mobile again and recover a high entropic spherical conformation. This presentation provides a brief survey of these fascinating materials and their applications. It also addresses the effect of small solvent molecules on the shape recovery process in SMPs both from the experimental side and via molecular dynamics computer simulations of simple model systems.
University of Tours, France
Talk Title: Raman scattering and Photoluminescence on single crystals of rare earth orthochromite RCrO3 (R = La, Pr, Nd and Sm)
Biography: Mustapha Zaghrioui est maître de conférences au laboratoire GREMAN à l’université de Tours depuis 2002. Il a obtenu son Doctorat en physique à l’université du Mans en 2000 sous la direction de Patrick Laffez et Alain Bulou.
Abstract: We report on flux single crystal growth, polarized Raman scattering and photoluminescence of rare earth orthochromites RCrO 3 (R = La, Pr, Nd and Sm). These compounds belong to multiferroic materials family as they exhibit both ferroelectric order and antiferromagnetic order. Different explanations were then given to interpret this behaviour, among them we can mention the role of exchange striction between the rare-earth moments and chromium atoms or also a local symmetry breaking due to the antiferromagnetic order. However, origin and mechanism of ferroelectricity remains elusive. To investigate structural changes related to this property, we first focus on the Raman mode assignment and their evolution versus rare earth at room temperature; then we investigate thermal behaviour of these modes between 80 K and 300 K. Finally, we probed the magnetic coupling by studying the luminescence spectra of Nd 3+ ion as a function of the temperature.
Université du Mans, France
Talk Title: Raman detection of analytes in the 10-6 – 10-8 M range: Highlight on commercial SERS substrates and on a low-cost nano-rough gold substrate
Biography: Jean-François BARDEAU est Directeur de Recherche au CNRS à l’Institut des Molécules et Matériaux du Mans (IMMM) de l’Université du Mans. Il s’est spécialisé dans l’étude des propriétés structurales et dynamiques de différentes classes de matériaux dont les matériaux hybrides organique/inorganiques et les biomatériaux (bio-minéralisation de mollusques marins à coquille unique et bivalves, pigments).
Plus récemment, il a orienté une partie de ses recherches sur la compréhension des phénomènes d’exaltations électromagnétiques associés aux systèmes confinés et nanostructurés pour développer des capteurs SERS (surface enhanced. Raman scattering) robustes, fiables et reproductibles en vue d’ applications dans les domaines de la santé et de l’environnement.
Abstract: Surface Enhanced Raman Spectroscopy (SERS) is a powerful non-invasive technique that is increasingly used to detect and identify traces of molecules. Although the sensitivity of SERS-active substrates is widely recognized, most of the applications have been severely limited by the low reproducibility, very small active surface area and high manufacturing cost of substrates. Today, commercial SERS substrates can be purchased, but because the manufacturing processes are generally different, the surface quality is not equivalent, nor are the enhancement factors and the reproducibility from one batch to another.
We have recently investigated and compared the efficiency of three different commercial SERS substrates and our home-made optimized nanorough substrate to detect a standard target molecule, thiophenol in alcoholic solution diluted at 10-6 M and 10-8 M. The spectral quality, signal homogeneity, distribution of intensity and thermal stability under laser beam will be discussed. Finally, I will show how our nanorough gold substrate can be used to detect and identify model molecules in binary systems by using statistical tools and multivariate data analysis.
University of Tripoli, Libya
Talk Title: Electro-physiological study of the heart cases using ECG
Biography: Prof. Dr. Abdalla Al-Kelsh, works mainly in Physics Department / Faculty of Science / University of Tripoli. HE was the President of the Libyan Academy / Gharyan. He teaches many advanced subjects such as electromagnetic theory, solid-state physics, statistical physics, and quantum mechanics, and supervises several scientific theses within the department’s postgraduate program. His scientific researches are based on: The applications of DFT theory on conductors and semiconductors elements & Mechanisms of formation and diffusion of impurities in complex ionic materials & Sources and applications of renewable energies & Simulation of the human nervous system, and in the electroencephalography EEG and electrocardiography ECG.
Omari Lhaj El Hachemi
University Hassan II of Casablanca, Morocco
Talk Title: Prediction investigation of optical and photovoltaic properties of Eco and Stable compounds as Chalcogenides ABS3 and Halide double perovskites A2BB’X6
Biography: Professor of Physics in the Faculty of Science Ain Chock, University Hassan II of Casablanca – Morocco.
Research interest: Materials Science, Energy and Environment.
Skills and expertise: Computation and simulation; Physical Properties; Synthesis and elaboration; Techniques of characterization; Magnetic Properties; Electrical Conductivity; Thermoelectricity; Composite Materials; Nanomaterials; Thin Films and Nanotechnology; Magnetic Materials; Optical materials; Ferroelectric Materials; Dielectric Materials; Construction Materials.
Abstract: In recent years, photovoltaic energy and photonic applications have given lead-free perovskite materials a lot of attention. Photovoltaic cells composed of lead-halide perovskites have shown a remarkable increase in energy conversion efficiency. However, they face instability problems which, combined with lead toxicity, have led to the search for new non-toxic semiconductor compounds. In this study, we start from stable perovskite halides which have emerged as an effective and environmentally friendly alternative to lead halide perovskites.
The properties of the double perovskite halides Cs2InSbX6 (X = F, Cl, Br, I) and Cs2Zr1-xTixI6 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) are examined by density functional theory (DFT) calculations via the Wien2k code. Calculated results show that these materials exhibit good structural stability and a suitable band gap (1.17 < Eg < 2.33 eV). In addition, the estimation of the theoretical efficiency was investigated by the Spectroscopic Limited Maximum Efficiency (SLME) method. For Cs2Zr0.75Ti0.25I6 (x = 0.25), we obtain an SLME (η) of 32.96% at a thickness of 500 nm.
We have also studied the electronic, optical, and photovoltaic properties of Chalcogenides BaHf1-xZrxS3 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) compounds. The band structure calculations reveal that these compounds exhibit a semiconductor behavior with a small band gap (Eg < 2 eV). We found a remarkable α exceeding 105 cm−1 near Eg. Predicted results required for photovoltaic applications with a maximum photovoltaic efficiency (η) between 22.22% and 30.09% for thickness L = 500 nm. The obtained results show that the studied compounds are promising candidates for solar cell applications.
Manuel Pedro Fernandes Graça
Universidade de Aveiro, Portugal
Talk Title: Influence of specific cations insertion on the electrical and biological properties of a modified 45S5 Bioglass
Biography: Manuel Pedro Fernandes Graça (M.P.F. Graça) graduated in Physics Engineering, Master’s degree in Science and Materials Engineering and PhD in Physics. He is an associate professor at the Physics Department of the University of Aveiro. MPFG is the author and co-author of 2 books, 30 chapter books, and +300 articles in international peer-review journals, plus 14 in conference proceedings, more than 4500 citations, and an h-index of 35 based on the Scopus platform. MPFG gave +50 oral communications including international plenary sessions. He is a co-author of more than 230 posters in international scientific meetings and 3 patents/utility models. MPFG was Editor Chief at the Nova Science Publishers of the book ”Electrical Measurements: Introduction, Concepts, and Applications”. His research team comprises 26 post-doc projects, 11 Ph.D. students. He completed the supervision of 31 final course project theses and 33 master dissertations.
Abstract: Bioglasses are used since the past century as a biomaterial in the bone regeneration field. However recent studies are trying to use them also as a therapeutic material mainly in the treatment of osteosarcomas. The most known bioglasses is the 45S5 Bioglass®, invented by Larry Hench et al., presenting a higher bioactivity. A possible application of this bioglass in the treatment of osteosarcomas can be accomplished by adding specific ions, such as iron oxide, that will allow the use of magnetic hyperthermia and the Fenton reaction as therapeutic mechanisms.
In this study, a 45S5 glass modified with specific metal ions (ex.: Zn, Cu, Ce, Fe, etc) were produced by the melt-quenching. A group of samples were prepared by changing the overall ball milling time, from 1 h up to 48 h. The objectives are to analyze the effects of the metal ion in the bioactive glass matrix and evaluate the influence of particle size on their physical and biological properties.
The studied glasses showed no evidence of structural changes compared to the 45S5 pure glass. The reduction of the particle’s size influences cytotoxicity and bioactivity. The samples with lower particle sizes showed a higher level of cytotoxicity. The electrical properties were evaluated by TSDC measurements.
University of Paris-Est Creteil, France
Talk Title: Multifunctional Co-based intermetallic alloys
Biography: Lotfi Bessais is a professor at the University of Paris-Est Creteil, France. He obtained a doctorate degree and HDR from the University of Paris 7, France. His research interests cover a broad range including nanomagnetic intermetallic materials.
Abstract: Multifunctional R-Co (R= rare earth) intermetallic alloys exhibit performant magnetic, magnetocaloric and important hydrogenation properties. Samples were prepared by high-energy ball milling followed by an optimized heat treatment.
Structural properties were determined using x-ray powder diffraction, while local environment around each cobalt atom were studied utilizing synchrotron beam local probes. Magnetic and magnetocaloric measurements were performed using a Quantum Design magnetometer.
Ab initio FP-LAPW calculations combining density functional theory and the full-potential linearized augmented plane wave method are performed to investigate the electronic and magnetic structure of the Co-based intermetallic alloys. The calculated magnetic moments are in good agreement with the experimental measurements.
The maximum hydrogen absorption content of R-Co reached 1.2 H/M (H/M: hydrogen per metal). High coercivity of 1.7 T are obtained for theses alloys after an optimization of their microstructure. In addition, these uniaxial anisotropic compounds exhibit a large magnetic entropy change at Curie temperature with a magnetocaloric effect equal to 6 J/(kg.K) under low magnetic field of 0-1T. These results indicate that, these nanomaterials are suitable for hydrogen storage, permanent magnet applications and for magnetic refrigeration.
University of Sidi Bel-Abbès of Algeria
Talk Title: New semiconductors for optoelectronic applications: Structure & Properties
Biography: Prof. Ali ZAOUI of Djillali Liabes University of Sidi Bel-Abbès of Algeria. He is Director of Physics Computational Materials Laboratory and Dean of the Faculty of Exact Sciences. His research interests: Condensed Matter Physics, Strongly Correlated Systems, and Magnetism.
Abstract:To complete and/or modify the optoelectronic properties of conventional semiconductors and in order to improve their yield and performance, it is necessary to research other new semiconductors with tailored physical properties to the desired applications. The Heusler materials and the compounds, with tetragonal ThCr2Si2-type structure, are new promising ternary materials. Heretofore only a little number of them is investigated. Several properties are considered as basic criteria for selecting new semiconductors. From a quantitative point of view, the values of the calculated properties of classical and conventional semiconductors such as the lattice constants, the band gap, the inter-atomic distance, the height, the static real dielectric function, the static refractive index are in the same order. From a qualitative point of view, we also compared the band structure, the density of states and the optical properties of these semiconductors with their III-V and II–VI analogs. Results are very motivating for these new semiconductors to take a deserving place in the optoelectronic area.