Search results for "Tungsten"
showing 10 items of 372 documents
Raman spectroscopic study of some lead phosphate glasses with tungsten ions
2006
Abstract The structure of x WO 3 · (100 − x )[2P 2 O 5 · PbO] glass system with 0 ⩽ x ⩽ 50 mol% was investigated by Raman spectroscopy. The characteristic bands of these glasses due to the stretching and bending vibrations were identified and analyzed by the increasing of WO 3 content. This fact allowed us to identify the specific structural units which appear in these glasses and thus to point out the network modifier role of tungsten oxide for low concentrations and its former role at high concentrations.
Electrochromic polyoxometalate material as a sensor of bacterial activity
2015
L. fermentum, a bacterium of human microbiota, acts as an electron donor to the electrochromic [P2MoVI18O62]6. Since, the reductive capacity of L. fermentum correlates with its metabolic activity, the reaction with [P2MoVI18O62]6- affords a means of evaluating its activity. Following this logic, we have concluded that vancomycin severely affects the activity of L. fermentum whereas omeprazole does not.
Weld pool surface temperature measurement from polarization state of thermal emission
2014
This paper presents a passive polarimetry method using a division of aperture optical device in order to measure the temperature distribution at the weld pool surface. Thermal emission from a hot liquid metal was investigated at a near-infrared wavelength corresponding to a blind spectral window of a helium plasma generated during gas tungsten arc welding process. The refractive index of liquid metal and the surface radiance are deduced from the polarisation state of thermal emissions. Based upon the knowledge of both characteristics, the temperature distribution can be calculated. Conseil Régional de Bourgogne
Self-assembly and alterable relaxivity of an organic cation-encapsulated gadolinium-containing polyoxometalate
2012
A new amphiphilic molecule bearing poly(ethylene oxide) (PEO) and quaternary ammonium group, was designed and synthesized to encapsulate paramagnetic Gd(III)-containing polyoxometalate (Gd-POM) through electrostatic interaction for obtaining a water-soluble organic-inorganic hybrid building block based on POM. The yielding organic cation-encapsulated Gd-POM (OCEP-Gd) complex exhibited water-solubility and amphiphility, leading to the spontaneous self-assembly into a regular vesicular structure with PEO chains towards water phase and POM units locating at the middle. The vesicular aggregate which has a regular monolayer structure, was further studied by means of dynamic light scattering, tra…
Tuning the photocatalytic activity of bismuth wolframate: Towards selective oxidations for the biorefinery driven by solar-light
2017
The sol–gel entrapment of nanostructured Bi2WO6 enhances the activity and the selectivity of the short-gap semiconductor in the sunlight-driven photo-oxidation of trans-ferulic and trans-cinnamic acid dissolved in water with air as the primary oxidant. Valuable products such as vanillin, benzaldehyde, benzoic acid and vanillic acid are obtained. This provides the proof of concept that photocatalysis could be a promising technology in tomorrow's solar biorefineries.
Supramolecular Design of Low-dimensional Carbon Nano-hybrids encoding a Polyoxometalate-bis-Pyrene Tweezer
2014
A novel bis-pyrene tweezer anchored on a rigid polyoxometalate scaffold fosters a unique interplay of hydrophobic and electrostatic supramolecular interactions, to shape carbon nanostructures (CNSs)-based extended architectures.
Metal Matrix Composites - Mmc - Turning: Comparison of Tool Materials
2002
The main properties required to the modem cutting tools to be employed in production, are both high wear resistance and chemical stability. In this last years, in the machining of MMCs several kinds of coated tools have been developed; they are characterized by high hardness to resist to the relevant strength and abrasive action of the reinforce fibers or particles, arranged inside the matrix. In turning of MMC the employ of Tungsten Carbide tools coated with Polycrystalline Diamond (PCD) have shown to be very effective, whereas they are very expensive thus increasing the production costs.
Influence of the focusing effect on XAFS in ReO3, WO3−x and FeF3
1995
Abstract The role of the focusing effect in the formation of X-ray absorption fine structure (XAFS) is considered for ReO3, non-stoichiometric tungsten oxides WO3−x and FeF3 having the perovskite-type structure. Two cases are mainly discussed: (1) an admixture of rhenium and tungsten L2-edge XAFS in ReO3 and WO3−x crystals to the one above rhenium and tungsten L1-edge and (2) high-order superfocusing effect in Fe0F1Fe2F3Fe4 atomic chain in iron K-edge XAFS of FeF3 which is analysed using an ab initio multiple-scattering approach.
Laser irradiation of carbon–tungsten materials
2014
Carbon–tungsten layers deposited on graphite by thermionic vacuum arc (TVA) were directly irradiated with a femtosecond terawatt laser. The morphological and structural changes produced in the irradiated area by different numbers of pulses were systematically explored, both along the spots and in their depths. Although micro-Raman and Synchrotron-x-ray diffraction investigations have shown no carbide formation, they have shown the unexpected presence of embedded nano-diamonds in the areas irradiated with high fluencies. Scanning electron microscopy images show a cumulative effect of the laser pulses on the morphology through the ablation process. The micro-Raman spatial mapping signalled an…
Barium depletion study on impregnated cathodes and lifetime prediction
2003
In the thermionic cathodes used in cathode ray-tubes (CRTs), barium is the key element for the electronic emission. In the case of the dispenser cathodes made of a porous tungsten pellet impregnated with Ba, Ca aluminates, the evaporation of Ba determines the cathode lifetime with respect to emission performance in the CRT. The Ba evaporation results in progressive depletion of the impregnating material inside the pellet. In the present work, the Ba depletion with time has been extensively characterized over a large range of cathode temperature. Calculations using the depletion data allowed modeling of the depletion as a function of key parameters. The link between measured depletion and em…