Physical Properties of Ternary NaPO3-KHSO4-MX (M=Na, K and X=Cl, Br) Glasses

AbstractThis contribution focusses on some thermal, optical and mechanical properties of sulfophosphate glasses containing MX (M=Na, K and X=Cl, Br) synthesized in the NaPO3- KHSO4- MX systems. The synthesized samples of 1cm in thickness present large vitreous areas. These glasses are stable at room atmosphere and soluble in water. Characteristic temperatures of glass transition and onset of crystallization were measured. The temperature of glass transition and the coefficient of thermal expansion range between 180 and 254°C and between 217.10-7 k-1 and 270.10-7k-1, respectively. Refractive index of all the samples is found is close to 1.48 in the 633-1555nm wavelength range. The micro hardness and the elastic moduli of the samples were also measured

Strontium fluorohafnate glasses

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Physical Properties of Multicomponent Fluorohafnate Glasses

International audienceFluoride glasses based on HfF4 have been synthesized in the HfF4-SrF2-BaF2 system. In order to decrease the crystallization rate, various fluorides (PbF2, ZnF2, AlF3 and YF3) have been introduced in the 66HfF(4)-22SrF(2)-12BaF(2) composition as substituent of alkali earth cations. Glass transition temperature is close to 320 degrees C, and coefficient of thermal expansion is 155 10(-7) K-1. Microhardness and elastic moduli have been measured. Values of refractive index are given for wavelengths ranging from 633 nm to 1551 nm. By comparison to fluorozirconates, fluorohafnate glasses exhibit larger density, lower refractive index, lower phonon energy and extended transmission in the mid-infrared spectrum. Potential applications relate to active optical fibres and supercontinuum generatio

Pure perovskite BiFeO3–BaTiO3 ceramics prepared by reaction flash sintering of Bi2O3–Fe2O3–BaTiO3 mixed powders

In this work, the 0.67BiFeO3-0.33BaTiO3 ferroelectric ceramic was prepared by Reaction Flash Sintering (RFS). This preparation technique combines synthesis and sintering in a single Flash experiment. The starting oxides reacted during the flash to produce a stoichiometric well-sintered solid solution at a temperature of 858 °C by applying a modest field of 35 V cm−1. The process takes place in a matter of seconds, which allows obtaining a pure perovskite structure without secondary phases. X-ray diffraction (XRD) results show the mixture of rhombohedral and pseudocubic phases expected for a composition that lies within a morphotropic phase boundary (MPB) region, since a significant splitting is observed in the reflections at 2θ values of 39° and 56.5°. The microstructure exhibit a peculiar bimodal grain size distribution that determines the electrical properties. As compared with previous results, flash-prepared 0.67BiFeO3-0.33BaTiO3 evidences smaller grain size, as well as slightly lower remanent polarization (Pr) and smaller coercive field (Ec) under similar electric fields. It is also demonstrated that the preparation by RFS provides benefits regarding electrical energy consumption.Ministerio de Economı́a y Competitividad, FEDER CTQ2017–83602-C2–1-RJunta de Andalucı́a, Consejerı́a de Economı́a, Conocimiento, Empresas y Universidad P18-FR-1087; US-12625

Electrical and dielectric properties of glass system NaPO3-KHSO4

International audienceGlass samples have been prepared in the NaPO3-KHSO4 binary system with the classical melting, casting and annealing steps. Electrical and dielectrical properties of glass samples were studied. Measurements of DC and AC conductivity and complex electrical permittivity of xNaPO3-(100 − x)KHSO4 glass system were carried out at temperatures ranging from room temperature to temperature located 15 °C below glass transition temperature Tg. Results showed that changes of NaPO3 concentration considerably affect values of observed parameters. DC conductivity of glass increases as NaPO3 concentration grows until concentration x = 60. However, beyond this value a sharp decrease of DC conductivity was observed. In addition relaxation times showed abrupt changes at concentration x = 60, corresponding to the lowest relaxation times at the temperature 90 °C

Journal of Nanoparticle Research: An Interdisciplinary Forum for Nanoscale Science and Technology© Springer Science+Business Media Dordrecht

Abstract In this work, we developed a new type of nanostructured photoanodes for photoelectrochemical water splitting. They are based on CdS-TiO 2 nanocomposite films, supported on conductive Ti sheets, prepared by an easy-to-achieve three-step method. It involves the production of TiO 2 nanofibers (NFs) using a controlled corrosion route of polished Ti sheets, the preparation of size-controlled CdS quantum dots (QDs) by the polyol process and the direct impregnation of TiO 2 /Ti sheets by QDs in suspension. The photoelectrochemical (PEC) properties of the resulting nanostructures were measured, using a homemade electrochemical cell illuminated with a standard Xenon lamp, and compared to those of bare TiO 2 NFs. A net enhancement of the photocurrent was observed after CdS impregnation, suggesting a low carrier recombination rate and a higher efficiency of the PEC device for solar water splitting, as the induced photocurrent is related to the electrons needed to reduce H + ions into H 2 at the cathode electrode (Pt wire). Keywords TiO 2 nanofibers CdS quantum dots CdS-TiO 2 /Ti nanocomposites Photoelectrochemical properties X-ray photoelectron spectroscopy Electron microscopy Energy conversio

The structural and the photoelectrochemical properties of ZnO–ZnS/ITO 1D hetero-junctions prepared by tandem electrodeposition and surface sulfidation: on the material processing limits

International audienceZnO–ZnS 1D hetero-nanostructures were prepared by an easy and scalable processing route. It consists of ZnO nanorod electrodeposition on ITO substrate and surface sulfidation by ion exchange in an aqueous Na 2 S solution. Increasing the treatment contact time (t c) from 8 to 48 h involves different ZnS growth mechanisms leading to different structural and microstructural rod characteristics, even if the overall size does not change significantly. Grazing X-ray diffraction, high-resolution microscopy, energy-dispersive spectrometry and X-ray photoelectron spectroscopy describe the outer surface layer as a poly-and nanocrystalline ZnS blende shell whose thickness and roughness increase with t c. The ZnO wurtzite–ZnS blende interface goes from continuous and dense, at short t c , to discontinuous and porous at long t c , indicating that ZnS formation proceeds in a more complex way than a simple S 2À /O 2À ion exchange over the treatment time. This feature has significant consequences for the photoelectrochemical performance of these materials when they are used as photoanodes in a typical light-assisted water splitting experiment. A photocurrent (J p) fluctuation of 45% for less than 5 min of operation is observed for the sample prepared with a long sulfidation time while it does not exceed 15% for that obtained with a short one, underlining the importance of the material processing conditions on the preparation of valuable photoanodes