Electrochemical performances of vitreous materials in the system Li2O–V2O5–P2O5 as electrode for lithium batteries

International audienceGlass composition 25Li2O–50V2O5–25P2O5 has been investigated as a potential material for electrode. Electrical properties as well as electrochemical performances of this glass composition have been characterized and results show a capacity less than 80mAhg−1 when tested in the [3–4.5V] potential window. To the best of our knowledge, this is the first lithiated amorphous material reported as a potential positive electrode material. Glasses, due to their wide available compositions in a given system and their easy processing, pave the way to new type of electrode material

All-solid-state silver batteries assembled by Spark Plasma Sintering

Bulk-type Ag0.7V2O5//Ag6I4WO4//Ag0.7V2O5 all-solid-state batteries have been assembled in one step by Spark Plasma Sintering (SPS). Their electrochemical performances were compared to the ones of similar solid state cells assembled by cold pressing, as reported in the 90s. The cold-pressed all-solid-state batteries with thick composite electrodes (above 400μm) display poor electrochemical properties explained by an important cell polarization associated to poorly defined electrode/electrolyte interfaces. In contrary, the thick batteries obtained by SPS exhibit excellent reversibility without any need of pressure load during cycling. The behavior lies on the well-defined interfaces and a good mechanical aspect, which are kept upon cycling. During the charge/discharge cycles, the electrochemical formation of AgxV2O5 does not display a drastic volume change, preserving the electrode/electrolyte interfaces. The structural evolution of AgxV2O5 upon cycling is discussed in comparison to the known phases synthesized by solid state reactions. The obtained results on silver batteries allow a general reflection on the development of all-solid-state Li-ion technology by SPS

Glasses for thermoelectricity

Auteurs du chapitre AInternational audienc

Nanoporous glass ceramics transparent in infrared range to be used as optical sensor (mechanical and viscoelastic properties for the TAS (Te-As-Se) glass)

Une nouvelle classe de capteur basé sur la création de vitrocéramiques nano-poreuses transparentes dans l infrarouge a été synthétisée dans le système GeS Sb S CsCl. La vitrocéramique nano-poreuse est obtenue par dissolution des cristaux de CsCl à la surface de l échantillon grâce à un traitement à l acide. Les premiers essais effectués avec différentes molécules montrent une augmentation de la sensibilité d un facteur 4 à 5 comparé au même échantillon non poreux. Les fibres de verre TAS (Te As Se ) sont actuellement utilisées en tant que capteur biochimique dans des domaines tels que la médicine ou l environnement. Les propriétés mécaniques de ces fibres se dégradent très rapidement ce qui empêche leur utilisation. Pour comprendre leur vieillissement prématuré et permettre de définir les meilleures conditions de stockage, nous avons étudié l influence de l environnement, de la lumière, du nombre de coordination, , ainsi qu un effet de recuit sur les propriétés mécaniques des fibres TAS.GeS Sb S CsCl glass-ceramics with nanoporous surface were synthesized and tested as optical elements. The nanoporosity is obtained through a two-step process, including controlled nucleation of CsCl nuclei in the glass matrix followed by selective etching of the nuclei with an acid solution. This novel porous material designed as an ATR (Attenuated Total Reflexion) plate and used as optical sensor shows higher detection sensitivity in initial experiments. The TAS (Te As Se ) infrared fiber, used as optical sensor in many fields of applications such as in medicine or environment exhibits poor mechanical properties rapidly that prevent it to be used. Its mechanical properties have been investigated as a function of time, environment (ageing in air, under vacuum or under static stress) and coordination number . TAS glass viscoelastic behavior at room temperature has also been the purpose of a study.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

The impact of glass structure on photoinduced changes in amorphous chalcogenides

International audienceIt is shown that the photostructural changes introduced during irradiation of chaclogenide glasses are dependent on the glass structure and composition. Photodarkening experiments performed on a series of As-S-Se glass suggest that the photostructural changes decrease as the network connectivity tends to an average coordination value of =2*4. Photorelaxation experiments perfomed on Ge-Se glasses show that contamination with oxygen does not appear to significantly affect photostrucral changes. On the contrary, the addition of CsCl in a Ge-Sb-S glass appears to suppress photostrucral effects entirely

Spark Plasma Sintering: An Easy Way to Make Infrared Transparent Glass-Ceramics

International audienceInfrared transparent glass-ceramics have been prepared in the system GeS2-Sb2S3-CsCl using spark plasma sintering in shorter times in comparison with conventional thermal treatments. The combined effects of pressure, time, and temperature allow the controlled crystallization of Cs-based crystals. The different glass-ceramics have been characterized by scanning electron microscopy and X-ray diffraction. The optical properties were also investigated

Multimaterial polarization maintaining optical fibers fabricated with the powder-in-tube technology

International audienc

Short range order and network connectivity in amorphous AsTe3 : a first principles, machine learning, and XRD study

International audienceThe atomic scale structure of amorphous AsTe 3 is investigated through X-ray diffraction, firstprinciples molecular dynamics (FPMD), and machine learning interatomic potentials (ML-GAP) obtained by exploiting the ab-initio data. We obtain a good agreement between the measured and modelled diffraction patterns. Our FPMD results show that As and Te obey the 8-N rule with an average coordination numbers of 3 and 2, respectively. We find that small fractions of under and over coordinated As and Te atoms occur in the amorphous phase with about 6% (FPMD), and 13% (ML-GAP) of 3-fold Te. As is found at the center of pyramidal structures predominantly linked through Te n chains rather than rings. Despite the low As concentration in AsTe 3 , its local environment feature a very high chemical disorder that manifests through the occurrence of homopolar bonds including at least 57% of As atoms

Fibre optique à maintien de polarisation fonctionnalisée avec une matrice vitreuse par l’exploitation de la technologie ’Poudre’

International audienc

Comparative study of ZnSe powders synthesized by two different methods and sintered by Hot-​Pressing

International audienceZnSe powders have been synthesized using two different methods: hydrothermal and high energy ball milling. The obtained powders have been dispersed and sepd. through the ultrasonic process. A comparison has been made between the powders by means of X-​Ray powder Diffraction (XRD) and SEM (SEM)​. The as-​prepd. ZnSe powders and the fine powders obtained after ultrasonic sepn. have been sintered by conventional uniaxial Hot-​Pressing (HP) technique in order to prep. ZnSe bulk ceramics. The optical properties of the ceramics have been characterized and compared. As a result, the sintering of the fine hydrothermal powder presents the best transparency in the visible and IR range. The transmission exceeds 60​% in the range from 11 to 19 μm