15^th Annual Congress on Materials Research and Technology February 19-20, 2018 Paris, France

Biography:

Alejandro Pacheco Sanjuan performs theoretical and computational research in solid mechanics and nanomechanics, utilizing large-scale molecular dynamics/mechanics (MD/MM) simulations, finite element (FEM) and particle methods (MESHLESS). In 2009 he has completed his graduation from the Engineering Science and Mechanics PhD program at Virginia Tech. After graduation he has joined the Mechanical Engineering Department at the Universidad del Norte, Barranquilla, Colombia.

Abstract:

Statement of the Problem: The kinematical description of deformation processes in two-dimensional nanostructures in most cases do not comply the assumptions made by the continuum mechanics theory. During deformation lattice vectors may change significantly in magnitude and orientation. In a first order continuum mechanics approximation each one of the lattice vectors would be erroneously mapped to a tangent space since crystalline membranes do not fall in the category of space-filling 3D materials. i.e., the ones that follow the Cauchy-Born rule. The purpose of this study is to analyze the deformation mechanisms of 2D crystalline nanostructures (graphene and silicene) under mechanical loads by using a kinematical description based on discrete differential geometry concepts.

Methodology & Theoretical Orientation: Molecular dynamics/mechanics (MD/MM) simulations of mechanical tests are performed to characterize the behavior of single and multilayer 2D nanostructures. Two virtual mechanical experiments are analyzed: Displacement controlled planar twist and spherical indentation. Finite deformations of single and multiple layered 2D crystals are analyzed in order to rationalize their mechanical behavior in terms of the existing shearable (Mindlin–Reissner theory) and non-shearable (Kirchhoff-Love theory) continuum shell models.

Findings: Being 2D nanostructures already a discrete system, triangular and tetrahedral geometrical constructions from their geometry are a natural set up to derive expressions for local strain and curvature tensors. Based on simple geometrical parameters an accurate kinematical description of the deformation of these very compliant structures is obtained.

Conclusion & Significance: Non-linear deformations of 2D nanostructures do not comply the assumptions of a first order continuum mechanics theory. The proposed method provides an accurate description of the geometrical changes in thin materials and has contributed to the analysis of the coupling between electromagnetic properties and changes in the local geometry induced by strains and curvatures.

Biography:

Kazuhiro Marumoto has completed his PhD from Osaka University and worked as an Assistant Professor at Nagoya University. He is an Associate Professor of Division of Materials Science at University of Tsukuba and also a Member of Tsukuba Research Center for Interdisciplinary Materials Science (TIMS) at University of Tsukuba. He has published more than 140 papers in journals and has been serving as a Chief Editor of The Society of Electron Spin Science and Technology (SEST) and an Editorial Board Member of Scientific Reports.

Abstract:

Graphene has been actively investigated as an electronic material owing to many excellent physical properties such as high charge mobility and quantum Hall effect due to the characteristics of a linear band structure and an ideal two-dimensional electron system. However, the correlations between the transport characteristics and the spin states of charge carriers or atomic vacancies in graphene have not yet been fully elucidated. Here, we show the spin states of single-layer graphene to clarify the correlations using an electron spin resonance (ESR) spectroscopy as a function of accumulated charge density using transistor structures. Two different electrically induced ESR signals were observed. One is originated from a Fermi-degenerate two-dimensional electron system, demonstrating the first observation of electrically induced Pauli paramagnetism from a microscopic viewpoint, showing a clear contrast to no ESR observation of Pauli paramagnetism in carbon nanotubes (CNTs) due to a one-dimensional electron system. The other is originated from the electrically induced ambipolar spin vanishments due to atomic vacancies in graphene, showing a universal phenomenon for carbon materials including CNTs. The degenerate electron system with the ambipolar spin vanishments would contribute to high charge mobility due to the decrease in spin scatterings in graphene.

Biography:

Masae Takahashi is currently an Associate professor of School of Agricultural Science, Tohoku University in Japan. She has received her BSc, MSc and Science Doctor’s degree (PhD) in Physics at Tohoku University. She was a Researcher of Institute of Physical and Chemical Research (RIKEN) from 1991-2003. Since then she became an Assistant Professor of Institute for Materials Research, Tohoku University and promoted to an Associate Professor at the same institute in 2006. She moved to Graduate School of Agricultural Science, Tohoku University in 2010 as an Associate Professor. She got the Shiseido Female Researcher Science Grant Award in 2008, the SJWS (the Society of Japanese Women Scientists) Promising Scientific Award in 2010 and the Ube-foundation Academic Award in 2016. Currently her researches focus on two-dimensional materials such as silicene and silicene molecules.

Abstract:

Silicene is the silicon equivalent of graphene, which is composed of a honeycomb carbon structure with one atom thickness and has attractive characteristics of a perfect two-dimensional -conjugated sheet. However, unlike flat and highly stable graphene, silicene is relatively sticky and thus unstable due to its puckered or crinkled structure. Flatness is important for stability, and to obtain perfect-conjugation, electron-donating atoms and molecules should not interact with the electrons. The structural differences between silicene and graphene result from the differences in their building blocks, flat benzene and chair-form hexasilabenzene. It is crucial to design flat building blocks for silicene with no interactions between the electron donor and orbitals. Here, we report the successful design of such building blocks with the aid of density functional theory calculations. Our fundamental concept is to attach substituents that have sp-hybrid orbitals and act as electron donors in a manner that it does not interact with the orbitals. The honeycomb silicon molecule with BeH at the edge designed according to our concept clearly shows the same structural, charge distribution and molecular orbital characteristics as the corresponding carbon-based molecule. The minimum structure of all the obtained silicon polycyclic molecules is flat. The charge is nearly neutral inside the ring and strongly negative at the ring edge due to the terminal BeH substituent. The HOMO and LUMO are -orbitals. The designed molecules could act as building blocks for flat silicene, which is a conjugated 2D sheet composed of six-membered silicon rings. Flat six-membered silicon rings have long been desired in silicon chemistry and 2D silicon materials. In this study, flat hexasilabenzene was realized and it was confirmed that the extended ring molecules are also flat. The flatness of these building blocks opens the way to flat silicene ribbons or films constructed by them.

Biography:

Masaki Tanemura is currently a Professor at Nagoya Institute of Technology (NITech), Nagoya, Japan and Special Adviser to the NITech President as well as a Director of Multi-Energy Innovation Center at NITech. Before joining NITech, he has worked at Toyota Central Research and Development Laboratories, Inc., Aichi, Japan and at Bonn University, Germany, as Alexander von Humboldt Fellow. His recent research activities include the synthesis, characterization using in situ TEM (transmission electron microscopy) and application of 1- and 2-dimensional nanomaterials, such as carbon nanofibers (CNFs), graphene, boron nitride and transition metal dichalcogenide materials.

Abstract:

Graphene, 2-dimensional carbon nanomaterial, is promising for various kinds of devices of next generation. In the graphene research, the low-temperature growth and transfer free growth onto the substrate as well as the controllable growth in position and quality are still challenging. Chemical vapor deposition (CVD) is widely used for the synthesis of high quality graphene on the catalyst surface. In CVD, unfortunately, high temperature (~1000 ^oC) and transfer processes are generally unavoidable. From a viewpoint of the future device applications, especially for transparent and flexible devices using non-heat tolerant substrates, and also of the energy saving, graphene itself should be synthesized at lower temperatures. Here we will deal with a novel approach different from the conventional CVD to grow graphene at and below 250 ^oC. The key in this approach is the selection of catalyst metal. The metal catalysts employed here were never popular for CVD graphene growth. Catalyst metal films were deposited onto amorphous carbon coated substrates of SiO₂ and glass. The samples thus prepared were simply annealed in vacuum at 150-250 ^oC. A typical example of a Raman spectrum obtained for a graphene flake thus synthesized at 250 ^oC on a glass substrate is being shown. As seen in the Raman spectrum, the surface was characterized by the intense G and 2D peaks together with a small D peak, confirming the growth of bilayer graphene directly on the glass substrates. Although the domain size of the graphene formed by this method was still small (<20 um), this approach will open up a new route for transfer free and position control graphene growth at low temperatures.

Biography:

Ar Sayed Ahmed is a Bangladeshi practicing Architect, Academician and Social Activist. He studied Architecture from SUST; Sylhet. He is currently a Lecturer in the Department of Architecture, Bangladesh University, Dhaka; where he conducts art appreciation courses, design classes and seminars and also researches as a free scholar. He successfully obtained his Master’s degree in Monumental Heritage from Anhalt University of Applied Sciences, Bauhuas of Dessau, Germany. He specializes in cultural studies, philosophy of art and architectural history, urban collective memory, material and climatic issues regarding vernacular architecture. He has already published articles on architecture and art from several journals around the globe which includes countries like UK, USA, Australia, Nigeria, India, China and Indonesia.

Abstract:

As an exceptional case of being modern monument, the concept of social functionalist housing at Siedlung Gropius Torten Estate in Dessau needs some reconsideration due to conserving or replacing materials. For this, evolution of social housing from the 18^th century was shortly discoursed with distinguished trends of architecture. The main concern of the study is how to introduce sustainability to a preset composite material design to suit todays need for affordable housing in suburban settings without doing any harm to its initial aesthetics. To deal with the local specifics of Dessau, some possibilities of localization and alternatives of modern installation were suggested. By potential rehabilitation of neglected suburban areas, this housing can also be an income generating organization as monumental heritage. Collective memory is applied in its architectural materials and housing pattern which might affect some strategic themes of social sustainability like social networking, communal identity, civic pride, neighborhood perceptions and community participation. Two main approaches of collective memory were followed: Conservation of materials having collective values and adaptive change of these with contemporary essentials. Experimental suggestions may demonstrate the possible links for sustainable redesigning with confined architectural expression of Bauhaus style. Aim is to reveal the various potential layers of collective memories in the used materials by reviving vitality.

Biography:

Soonnam Kwon is a Staff Scientist of PAL-XFEL division group, Pohang University of Science and Technology has obtained his PhD degree from the Department of Physics, Yonsei University in 2001. He has worked in Daewoo Advanced Institute of Technology as a Principal Researcher until 2005, where he concentrated on organic materials characterization for use in OLED.

Abstract:

Experimental techniques such as nano-ARPES are expected to provide an opportunity to measure the electronic properties of disordered nanomaterials directly. However, the interpretation of the spectra is not quite simple as it contains complicated quantum mechanical effects related to the measurement process itself. In this talk, I would like to demonstrate a novel approach that can overcome this conundrum by corroborating the experimental results with an adequate simulation. Ab. initio calculation on arbitrarily shaped or chemically ornamented nanostructures is elaborately correlated to the photoemission theory, a method also known as independent atomic center approximation (IAC). This correlation can be directly exploited to interpret the experimental results. To test this study, a direct comparison was made between the calculation results and experimental results on pentacene molecule and highly oriented pyrolytic graphite (HOPG). As a general extension, the unique electronic structures of nano-sized graphene oxide and features from the experimental result of black phosphorous (BP) are disclosed for the first time as supportive evidence for the usefulness of this method. This work opens an unprecedented approach to intuitive and practical understanding of the electronic properties of disordered nanomaterials.

Biography:

Raymond Fresard currently works at the Laboratoire CRISMAT, National Graduate School of Engineering and Research Center (Caen). After getting a degree of Physicien (1984) and a PhD in Physics from the University of Neuchatel, Switzerland (1989), in the field of liquid and amorphous metals I moved to the University of Karlsruhe, Germany, where I started to work in the field of strongly correlated electrons. In 1994, I moved to Shimane University, Japan, where I accepted an Associate Professor position. I pursued research activities in the fields of strongly correlated electrons and bosons, and on the transport properties of amorphous metals. In 1996 I returned to the University of Neuchatel, Switzerland, where I stayed until 2000. I then accepted a Professor position at the Institute des Sciences de la Matiere et du Rayonnement, Caen, France, where I am pursuing research activities in the field of strongly correlated electrons, in close connection with experiment.

Abstract:

The cooperative properties of strongly correlated electrons have often been related to key technologies, for instance with the aim of developing high capacitance hetero-structures. In this contribution we unravel the electrical permittivity contained in the extended two-dimensional Hubbard model. Regarding static properties we consider a pair of plates hosting correlated electrons separated by a dielectric medium, that comprise a capacitor. We show that the natural tendency towards phase separation harbored in the two-dimensional Hubbard model extended by over-screened Coulomb interaction results in an increase of the capacitance. This effect competes with the electrostatic contribution and in a thermodynamically stable state we find it to be enhanced by the proximity to a van Hove singularity. The mutual influence of the interaction parameters and the distance of the van Hove singularity to half-filling are also discussed, as well as the parameters controlling the disparity of the capacitance and the compressibility. The dynamical properties will be addressed as well. It will be shown that the spectra generically consists of a continuum, a gapless collective mode with anisotropic zero-sound velocity and a correlation induced high-frequency mode dispersing at energies close to the Hubbard U. The influence of the loss of the particle-hole symmetry on these spectra will be presented too.

Biography:

Marie-Amandine Pinault-Thaury is a Researcher of the French National Center for Scientific Research (CNRS), working at the “Groupe d’etude de la Matiere condensee” (GEMaC) laboratory. She is the Co-Head of the Diamond for Electronics group and In-Charge of the CAMECA-IMS7f equipment, a secondary ion mass spectrometer (SIMS). She is an expert in epitaxy and physical study of semiconductors.

Abstract:

Diamond offers very interesting potential applications for high temperature, high frequency and high power electronics. In order to use it as an electronic grade material, the controls of its quality and its doping are necessary. As most of wide band-gap semiconductors, diamond suffers from an asymmetry in the control of its doping. While the p-type conductivity is easily achieved by using boron impurities, the n-type doping is still an issue for the development of bipolar electronics based on diamond. As electronic applications need high material chemical purity, the microwave plasma assisted chemical vapor deposition (MPCVD) is currently the most used growth techniques for diamond. For n-type doping, the range of impurities that should fit into the diamond lattice is limited and the equilibrium solubility of dopants in bulk diamond is often low. Despite a covalent radius ~1.4 times bigger than carbon and a donor level relatively deep (E_C=0.6eV), the highest n-type conductivities have been achieved with incorporation of phosphorus impurities during the homoepitaxial growth. This impurity has been reproducibly incorporated into (111) mono-crystalline diamond by using different phosphorus precursors (gaseous or liquid) during MPCVD diamond growth up to a few 10²⁰ P/cm³. However to incorporate phosphorus in donor sites is more difficult (100) orientation that is preferential for electronics. In this review, the difficulties inherent to the n-type doping of diamond will be presented. The different donors in diamond will be reviewed as well as the doping methods. The properties of n-type diamond grown in the GEMaC laboratory with phosphorus doping will be shown. The results achieved both on the (111) and the (100) orientated-substrates used for the homoepitaxy will be given. The incorporation in substitutional site and the high compensation level by residual impurities and defects will be discussed.

Biography:

Laeticia Petit has received her PhD in Materials Science from the University of Bordeaux in France in 2002. She is currently an Assistant Professor in the Laboratory of Photonics at Tampere University of Technology (TUT, Finland). She is also an Adjunct Professor in the Faculty of Biomedical Sciences and Engineering at TUT and in the Inorganic Chemistry Laboratory at Abo Akademi University, Finland. Her current research interests include the processing and characterization of novel active glasses/glass-ceramics and fibers for photonic applications. She focuses her research on understanding composition-structure-property relationship in these materials, with the goal to tailor new compositions to suit specific applications in photonics. He is co-author of 2 patents and more than 110 refereed publications, reviews, proceedings and book chapters and she has presented more than 15 invited and contributed presentations in her career.

Abstract:

The fabrication of new rare-earth (RE) doped glasses has attracted lots of research interests, the improvement in the performances of the glasses remaining the prime objective of the studies. Silica glass, as a host material, has proven to be very attractive because of its wide wavelength range with good optical transparency and high mechanical strength, just to cite few attractive properties. However, RE tends to cluster in silica glasses. Phosphate glasses are good host materials due to their ability to incorporate high amount of RE. Because the local environment around the RE is of paramount importance for determining the optical properties, there is a constant interest in investigating new RE doped glasses with improved spectroscopic properties. A route of interest to improve the spectroscopic properties consists of controlling the RE optical response independently of the core glass composition. Different techniques have been developed: One technique consists of synthesizing RE doped nanoparticles directly in situ in the glass. In another technique, RE doped nanoparticles, formed by solution chemistry, are added in the glass batch prior to or after the melting using the direct doping method. In this presentation, we will review our latest development of glass-ceramics. First, we report the preparation and characterization of new Er³⁺ doped glasses. We discuss the impact of the glass composition and of the effect of nucleation and growth on the luminescence properties of the newly developed glasses. Then, we will explain the direct doping method and its challenges which are related to the particles corrosion. We explain how to process particles containing glasses which possess the spectroscopic properties of the particles.

Biography:

Nashwa El Shafei is an expert in fashion design and has established several fashion shows on the level of the faculty of applied arts and university.

Abstract:

Chaos is the primeval state of existence from which the first gods appeared, in other words, the dark void space in Greek mythology. It is made from a mixture of what the Ancient Greeks considered the four elements: Earth, Air, Water and Fire. On the other hand chaos Theory is an alternative name for “nonlinear dynamical systems theory”. The latter is an umbrella term for the study of phenomena such as attractors, bifurcations, chaos, fractals, catastrophes and self-organization, all of which describe systems as they change over time randomly. In chaotic phenomena, seemingly random events are actually predictable from simple deterministic equations. Thus a phenomenon that appears locally unpredictable may indeed be globally stable, exhibit clear boundaries and display sensitivity to initial conditions. The latter property is also known as the Butterfly Effect. The initial positioning of the costume design therefore, is the deconstruction of the consumer group. How does one define a dress code, who sets the standards for the invitation that reads, “smart casual” or “formal “or chaos casual? Unfortunately it is the society you live in who set the rules and standards of these fashion rules, but how far it could be gone to trust the society we live in on fashion rights? It is believed that fashion design system is a chaotic system, with a typically non-periodic, and seemingly erratic disorder steady-state movement patterns. Chaos Theory is determined as a design methodology, which is the basic view of the world observed by designers and it also plays a liberal role in understanding the world thinking. Therefore it will highly promote the creative thinking of present and future designers. Although there is certainly no lack of creativity or striking imagery in fashion today and during most of the last century, fashion (in the Western world) was dictated by a handful of designers in places like Paris and Hollywood and trends got filtered down to the masses via magazines, movies and sewing patterns, but there seems to be no direction. On the other hand, the styles might be not likeable or unacceptable, but they were undoubtedly clear. The present research is exploring the chaos fashion design through the different elements of fashion design as such the fabric colors, the dress constructions, the dress structures as well as all of them totally.

Biography:

Toshihiro Miyata is a Professor at the Kanazawa Institute of Technology (KIT) in Japan and a Researcher of the Optoelectronic Device System R&D Center at KIT, where his interests center on optoelectronic devices, especially solar cells using Cu₂O. He has received his BE degree in Electronics Engineering from KIT in 1987 and his ME and Doctor of Engineering degrees from the KIT in 1989 and 1992, respectively. From 1992 to 1993, he was a Visiting Scientist at the Micro Systems Technology Laboratory at MIT, USA.

Abstract:

Oxide semiconductor thin films are very attractive materials for optoelectronic device applications, such as transparent conducting electrode and solar cells. Recently, a substantial improvement of conversion efficiency has been reported in solar cells fabricated using n-type oxide semiconductor thin films deposited on p-type cuprous oxide (p-Cu₂O) as the active layer. This paper describes the present status and prospects for further development of super low-cost Cu₂O-based hetero- and/or homo-junction solar cells. We have recently reported that the obtainable photovoltaic properties could be dramatically improved in p-n hetero-junction solar cells fabricated by depositing appropriate n-type oxide semiconductor thin films on p-type Cu₂O sheets that had been prepared by a thermal oxidization of copper sheets. The observed improvement suggests that it is necessary to stabilize the surface of techniques for applying the hetero-junctions. Consequently, the obtainable performance could be improved by not only the formation of an n-type oxide semiconductor thin-film layer, prepared using low-temperature and low-damage deposition methods such as pulsed laser deposition (PLD), but also the use of high-quality Cu₂O sheets. It shows the structure of Cu₂O-based p-n hetero-junction solar cells. The thermally oxidized polycrystalline Cu₂O sheets exhibited a resistivity on the order of 10³ Ωcm, whole concentration on the order of 10¹³ cm^-3 and Hall mobility in the range of 100-110 cm²/Vs. For example, a high efficiency of 8.23% was obtained by AZO/n-type Zn1-X- GeX-O/p-Cu₂O hetero-junction solar cell fabricated by depositing using low-damage PLD on non-intentionally heated Cu₂O sheets. This is the highest value of the efficiency of hetero-junction solar cells using Cu₂O system. In addition, we will also describe that the fabrication of p-n homo-junction Cu₂O solar cells using i-type or n-type Cu₂O thin films grown by electrochemical deposited (ECD) method.

Biography:

Yuta Saito has received his BS (2008), MS (2010) and PhD (2013) in Materials Science from Tohoku University, Japan. After obtaining his PhD, he has worked as a Postdoctoral Researcher in National Institute of Advanced Industrial Science and Technology (AIST), Japan, from 2013 to 2014 and then became a tenure-track Researcher in AIST. Currently he mainly focuses on the development of novel materials for future electronics, including phase change memory, chalcogenide materials and two-dimensional semiconductors, both experimentally and theoretically based on first-principle calculations.

Abstract:

Chalcogenides materials including the elements S, Se and Te have attracted attention due to their exotic electronic properties. These materials can be categorized into two groups, topological insulators (TIs) and transition metal dichalcogenides (TMDs). Even though there are fundamental differences in the electronic structures between these groups, interestingly, both systems assume a layered crystal structure where chalcogen atoms always terminate an individual unit layer, and each unit layer weakly interacts with other layers via van der Waals (vdW) forces. TIs have an energy band gap in bulk, but possess linearly dispersive conducting channels due to surface states that are characterized by a Dirac cone. On the other hand, one of the most intriguing properties of TMDs is that typical TMDs demonstrate an indirect-direct transition in the monolayer limit, while bulk TMDs are indirect band gap semiconductors. Recently, more and more attention has been paid not only to layered materials themselves, but also to their hetero-structures due to the emergence of interesting properties from the interfaces. It is also expected that since vdW forces are weak, there is a strong possibility of forming a high-quality hetero-structure regardless of the differences in lattice constants between the two component materials, a problem that is sometimes severe in three-dimensionally bonded compound semiconductors. In this study, we focus on the hetero-structure of two different tellurides. An example of a telluride heterostructure consisting of MoTe₂ (TMD) and Sb₂Te₃ (TI) is being shown. It should be noted that the band structure of this hetero-structure has two representative features, namely, the formation of a Dirac cone at the Γ point attributed to Sb₂Te₃ and the direct transition at the K point due to MoTe₂. The electronic structure of other hetero-structures will be discussed in the presentation.

Biography:

John Marc C Puguan is currently an Assistant Research Professor at the Department of Energy Science and Technology, Myongji University, South Korea. He is passionate in producing and enhancing new class of advanced materials for energy applications. His specific interest covers the synthesis of organic-inorganic based electrolytes for electrochemical devices such as energy efficient electrochromic glass and windows.

Abstract:

Currently the use of ionic liquids as electrolytes is enhancing the performance, security, speed, cyclability and long term stability of various electrochemical devices such as batteries, solar cells, fuel cells, super-capacitors, electrochromic devices, light-emitting electrochemical cells, actuators, biosensors and field effect transistors among others as well as in catalysis. However, ionic liquids are intrinsically liquids that present drawbacks that are difficult to overcome such as the need of thorough encapsulation due to leakage. Replacement of the liquid electrolyte with safer and mechanically stable material but still exhibiting excellent electrochemical properties is the goal of this study. A new poly(ionic liquid) or PIL which is a special type of polyelectrolyte carrying a cationic center constrained in the repeating units of the main chain is synthesized. This exhibits a dynamic combination of the unique properties of ionic liquids and the solid state properties of a polymer. A heterobifunctional ethylene glycol (EG)-based monomer was synthesized prior to the cycloaddition reaction. Propargyl group was introduced on one of the terminal end of the PEG unit and an azide group on the other end. Monomer was purified and underwent a copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction to yield poly(1,2,3-triazole). PIL was reacted with methyl iodide to activate the cationic moiety. Subsequently, the iodide anion underwent anion exchange with bis(trifluoromethane)sulfonimide lithium (LiNTf2) salt to yield poly(3-methyl-1,2,3-triazolium bis(trifluoromethane)sulfonimide). This new PIL exhibits ionic conductivity of 1.2×10^-4 S cm^-1 at 30 ^oC which is at par with best side-chain PILs in literature. This new electrolyte efficiently switches an electrochromic device (ECD) with 18% optical contrast from its transparent state to a colored state and vice versa. The development of this polyelectrolyte with simple structure and excellent physical and thermal properties is promising for the design of new all-solid state electrochromic devices and other electrochemical device applications.

Biography:

Guy Antou is the Assistant Professor since 2005 at SPCTS Laboratory, University of Limoges, mainly dealing with the experimental characterization, the modeling and the numerical simulation of the thermo-mechanical behavior (in particular viscoplastic) of ceramic materials during their elaboration by pressure-assisted sintering or in service (creep). His has 29 publications in international journals, 4 invited conferences, 55 oral communications, 3 grants, etc. to his credit.

Abstract:

Boron carbide is a promising ceramic in the armor field and in nuclear reactors due to its low weight, its high hardness and its high capacity to absorb neutrons. The poor sinterability inherent to the covalent character of the B-C bonding makes the complete densification of boron carbide powder difficult to obtain by conventional sintering technique (i.e. pressure-less sintering). In this work, fully-dense boron carbide ceramics exhibiting fine microstructure (i.e. sub-micrometric grain size) are elaborated using the spark plasma sintering (SPS) without any sintering additive. The SPS densification mechanisms are investigated through the determination of the associated densification parameters (i.e. stress exponent around 3.6 and apparent activation energy of 101±20 kJ.mol^-1). These values are correlated with structural observations conducted by transmission electron microcopy. It is shown that the induced deformation mechanism corresponds to a power law creep regime controlled by dislocation motion and potentially associated with a twinning phenomenon at high temperature. In addition, the effect of the impurity content decrease by a suitable heat-treatment of the starting commercial powder is studied on the mechanical properties at room temperature (i.e. Vickers hardness and fracture toughness) and high temperature (up to 1600 °C) by bending tests (i.e. elastic modulus, flexural strength). These properties are correlated with (micro) structural characteristics of both materials. It is shown that heat treatment of the powder decreases the contents of free carbon (exhibiting an onion-like structure) and of secondary oxide phases (silicon and boron-rich) at grain boundaries. It leads to a slight decrease of the hardness, fracture toughness and bending modulus and an increase of the flexural strength. In addition, no brittle-to-plastic transition is noticed up to 1600 °C.

Biography:

Mineo Hiramatsu is a Full Professor of Department of Electrical and Electronic Engineering and the Director of Nanocarbon Research Center, Meijo University, Japan. He also serves as the Director of Research Institute, Meijo University. He has served as the Director of The Japan Society of Applied Physics. His main fields of research are plasma diagnostics and plasma processing for the synthesis of thin films and nanostructured materials. He has authored more than 100 scientific papers and patents on plasma processes for materials science.

Abstract:

Graphene-based nanocarbons include fullerene, carbon nanotube (CNT) and graphene sheet itself; nowadays they have a wide range of possible applications. Plasma enhanced-chemical vapor deposition (PECVD) can be easily applied to grow diamond, CNT and graphene films. In the case of PECVD, the main reaction mechanisms of deposition are determined by the species produced in the plasma. In the case of deposition of carbon-based materials, the balance between carbon precursors and etching radicals is important. Control of surface reaction is also important. Sometimes, pretreatment of substrate or selection of substrate is required for the nucleation. In short, for the synthesis and structure control of carbon nanostructures, we should consider the control of multiple radicals playing different roles such as carbon precursors and H atoms. In addition, control of surface reaction for the nucleation should be considered. For instance, ion flux onto substrate is unnecessary for plane graphene formation, but necessary for vertical grapheme nucleation on Si substrate. Moreover, pretreatment of substrate or selection of substrate would be crucial for synthesizing CNTs and graphene, catalyst nanoparticles for CNT growth and metal substrates (Ni and Cu) for plane graphene formation are these examples. We have investigated the synthesis of CNWs and planar few-layer graphene using PECVD with controlling the ion flux incident on the substrate and surface pretreatment with metal nanoparticles. For the growth of CNWs, ion bombardment on the substrate surface would play an important role in nucleation by creating active sites for neutral radical bonding, resulting in the formation of vertical graphene. On one hand, by reducing the ion flux incident on Ni or Cu substrate, planar graphene can be formed. We focus on the structure control of CNWs during the growth processes to be used as platform of the electrochemical and bio applications.

Biography:

Hajar Ghanbari has her expertise in carbonaceous and 2D materials, ceramic composites and laser-assisted synthesis of nanomaterials. She has proposed her explosion model on the laser-assisted synthesis of graphene in organic solvents in 2014. She has joined Iran University of Science and Technology, Faculty of Metallurgy and Materials Engineering, Ceramics Division since September 2016 and established a research group focusing on modern ceramics.

Abstract:

Hexagonal boron nitride (h-BN) is an advanced ceramic material similar in electronic structure to the most versatile of elements, carbon, sharing the same number of electrons between adjacent atoms. This hexagonal phase is the most stable and softest among BN polymorphs. h-BN powders are mostly used as lubricants. Compared to graphite, the h-BN can be utilized in an oxidizing atmosphere up to 900 °C, as well as low temperatures. Good lubricity, corrosion and oxidation resistance in high temperature guaranteed the premium market for this light material. In this paper, we have been successfully synthesized h-BN from a precursor obtained by urea and boric acid, following by nitridation in >1000 °C temperature and leaching step. We studied the effect of nitridation temperature (1000 °C-1200 ^oC) through the addition of lithium carbonate (Li₂Co₃), sodium carbonate (Na₂Co₃) and calcium carbonate (CaCo₃) on the powder morphology and microstructure. Synthesized particles are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). In addition, we measured the contact angle of water on the pressed disks prepared at different temperatures and with different additives. Comparing the results showed that the nitridated powder prepared with the Li₂Co₃ additive in 1200 °C possessed the highest purity and largest grain size. In addition, the results confirm the non-uniform effect of temperature increase while utilizing three different additives.

Biography:

Tauqir A Sherazi is an Associate Professor and Head of Material Chemistry Group at Department of Chemistry, COMSATS Institute of Information Technology, Pakistan. His expertise is in the development of cost effective and highly efficient polymer electrolyte membrane materials through controlling the chemistry and morphology of the polymers.

Abstract:

Most electrochemical conversion and storage devices, such as fuel cells and redox-flow batteries, rely on the amazing properties of ion conducting polymer membranes. The development of polymer electrolyte membranes (PEMs) combining high ion conductivity and durability is a major challenge for materials chemistry. Nafion^® (DuPont) is state of the art membrane due to its good mechanical strength, excellent proton conductivity and stability, but its limitation to low temperature operation, high cost and fuel crossover are major obstacles that renders its usage in commercialization of fuel cell. Various polymers have been synthesized and explored as an alternative membrane material to reduce cost and improved proton conduction to Nafion but most of these showed trade off properties. The membranes showing good conduction may have poor stability or mechanical strength. This fact impedes the technology to achieve commercialization status. In present study, radiochemical pore filled membranes were prepared in which porous polyethylene (PPE) substrate was radio-chemically grafted and filled with styrene/acrylic acid copolymer. Proton Exchange Membranes prepared through radiochemical pore filling process exhibited high ionic conductivity. High conductivity is attributed to the formation of micro level confinement within the membranes for ion transport is reported for the first time. Despite their simple preparation method, consisting single radiochemical grafting and pore-filling step using commercially available porous substrate, involves least amount of chemical. The polymer provides PEMs which exhibited exceptional proton conductivity at good but relatively lower ion-exchange capacity, as well as a high swelling resistance. An unprecedented hydroxide conductivity of 274 mS cm^-1 is obtained at an ion-exchange capacity of 2.85 meq g^-1 under optimal operating conditions. The exceptional ion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid cation transport.

Biography:

Sadiye Pelin Erden has her expertise on the production of ceramic metal oxide powders by using different methods such as solid state and hydrothermal synthesis. She is working on production of zinc stannate powders via these methods and investigation of the effect of the material characteristic on the chemical stability of zinc stannate in different aqueous environment.

Abstract:

Zinc stannate that has unique properties, including high electron mobility, high electrical conductivity, low visible absorption and excellent optical properties. Recently, its potential applications have been investigated for various applications such as gas sensors, electrode materials for dye sensing solar cell (DSSC) and catalyst for photo-degradation of dyes and pollutants. In order to obtain the maximum performance in such applications, Zn₂SnO₄ materials should represent a high chemical stability. However, the chemical stability of Zn₂SnO₄ materials in aqueous environment depending on pH and this has not been well understood in detail yet. Therefore, the research objective of this study was to evaluate the effects of the material characteristics (particle surface area, particle size and form) and pH of the suspension on the chemical stability of Zn₂SnO₄ in aqueous environment and hence to determine the interaction between the particles and aqueous medium. In this study, zinc stannate particles with different surface area and particle size were synthesized by solid state reaction and hydrothermal methods. After the Zn₂SnO₄ powders were synthesized, Zn₂SnO₄ suspensions in aqueous environment were prepared at pH 3 and pH 9 by adding HCl acid and NaOH base solutions to the deionized water, respectively. Supernatants from the suspensions were collected for the following 30 days in 24 hours intervals. Zn⁺² and Sn⁺⁴ ion concentrations were determined by ICP-OES. The ICP-OES results showed that cations of Zn₂SnO₄ dissolve more in the acidic side than the basic one. In addition, dissolution rate of the hydrothermally synthesized Zn₂SnO₄ powder with higher surface area (18.053 m²/g) at pH 3 was much faster than that of the solid state synthesized Zn₂SnO₄ powder with relatively lower surface area (1.99 m²/g).

Biography:

Gisele Lecomte-Nana has developed a basic knowledge related to the characterization and use of phyllosilicates to manufacture materials for wide diffusion and technical applications. Indeed, I have investigated the consolidation routes of clay-based ceramics (sintering mechanisms) and developed a class of original sustainable products called “geomimetic” materials (chemical consolidation at moderate temperature). Taking advantage of this background, together with a smart match between “Formulation-Shaping-Ceramic/Composite Materials”, she is working on the following themes: (1) Control/Mastering of surfaces and interfaces through (non)reversible routes for phyllosilicates and hybrid systems; (2) Ceramic Processes and Multi-scale Texturing aiming to setup original method for controlling particles organization up to the product scale; (3) manufacturing Flexible and Original Hierarchical Materials targeting the highlight of structure-properties relations for smart and sustainable systems.

Abstract:

Statement of the Problem: Textured materials are offering a very interesting variation of properties of use depending on the chosen direction. The anisotropy that is exhibited by textured ceramics promotes their efficiency in service (filtration membranes, fuel cells or multilayer ceramic capacitors). Layered ceramics shaped by tape casting are developed in this scope. The thickness of the manufactured tapes ranges from 25 µm to 1600 µm. In most cases, relatively pure oxides or synthesized powders are used for these ceramics, and therefore induce great environment and economic impacts. In order to reduce the latter issues, the enhancement of using clays, which are environmentally friendly naturally occurring materials, appears as promising alternative. Thus, the prospective development of clay-based textured ceramics for highly technical applications. The purpose of this study is to highlight the effective influence of the nature and shape of clay minerals on the texture, sintering behavior and the final characteristics of ceramics shaped by tape casting.  Methodology & Theoretical Orientation: kaolin (K), halloysite (H), palygorskite (P) and talc (T) were used as raw materials; which are representing respectively 1:1, 2:1 and fibrous-like clay minerals. The optimized kaolin-based slurry served as the reference tape casting formulation. Each clay type was mixed with kaolin in various amounts: 10, 20, 30, 40, and 50 mass % (with respect to kaolin + added clay). The changes involved in the rheological behavior were analyzed. The sintering behavior of the dried tapes was investigated through thermo-dilatometry characterizations. The green and consolidated tapes were submitted to structural, mechanical and physical properties analyses. Conclusion & Rheological measurements allow determining the appropriate surfactant ratio for a given clay mixture. The presence of halloysite or palygorskite promoted the strengthening of green tapes, more than talc in relation with particle shape effects. P and T act as fluxing agents.