Search results for "Cathode"

<title>Forward diffracted parametric X radiation from a thick Tungsten single crystal at 855 MeV electron energy</title>

2007

Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward d…

(Invited) The Effect of (La,Sr)MnO 3 Cathode Surface Termination on Its Electronic Structure

2017

La1-xSrxMnO3 (LSM) was one of the first perovskites used as SOFC cathode material. Its (001) surface has two possible terminations, LaSrO and MnO2, with quite different properties and oxygen reduction efficiencies. To avoid effects of surface polarity and the dipole moment across the material, symmetric non-stoichiometric slabs are commonly used in theoretical calculations with identical terminating planes on its both sides. We analyzed the dependence of the electronic structure (density of states) and charge distribution (effective atomic charges and chemical bond covalency) on the slab termination and Mn ion oxidation state (controlled by the Sr content and slab nonstoichiometry).

Stable and transient color centers in Gd3Ga5O12 crystals

2004

The work is devoted to investigation of stable color centers (CC) that are created in Gd3Ga5O12 (GGG) crystals under irradiation with γ-quanta (E = 1.25 MeV, D = 105 Gy ) as well as transient CC created in the crystals under irradiation with pulsed electron beam (E = 0.25 MeV, pulse duration 10 ns, fluence 1012 cm-2, time interval of registration 0-500 ns). On the basis of the performed study of optical absorption spectra of the as-grown and irradiated crystals it was established the correlation between a defect subsystem of as-grown crystals and a type of CC induced by radiation in the crystals. The role of Ca2+ dopant ions in the processes of CC formation is examined. Models of the stable…

Thermogalvanic effects on the corrosion of copper in heavy brine LiBr solutions

2012

Thermogalvanic corrosion of copper in heavy brine LiBr solutions has been investigated using a zero-resistance ammeter (ZRA). The temperature gradients between copper electrodes immersed in the same LiBr solution result in the formation of thermogalvanic cells with hot anodes, leading to high and sustained thermogalvanic currents. Copper loss rates, calculated using Faraday's law, substantially exceed 0.025mmyear -1, a value regarded as the threshold of low corrosion rates. The effects of thermogalvanic coupling on the surface properties of the anode and the cathode have been analysed by means of electrochemical impedance spectroscopy (EIS). The results obtained in this analysis have been r…

EXPERIMENTAL OBSERVATION OF THE INTERACTION BETWEEN A MICROSCOPIC CATHODE TIP AND ELECTRICAL ARC

2008

ELECTROCHEMICAL CONVERSION OF CARBON DIOXIDE TO FORMIC ACID IN A PRESSURIZZED FILTER PRESS CELL

2018

To limit the negative effect of carbon dioxide as a greenhouse gas, an interesting approach is the utilization of Carbon Capture and Conversion (CCC) methodology, which is focused on the use of CO2 waste as a feedstock to produce added-value product by using the excess electric energy from renewable source [1]. In this framework, an increasing attention has been devoted in the electrochemical conversion of carbon dioxide to formic acid in water [2,3], which is considered one of the more attractive pathway to convert CO2. Since the main hurdle of the CO2 reduction from aqueous solution is the low CO2 solubility in water, in this work, the effect of some operating parameters, including pressu…

Electrochemical treatment of paper mill wastewater by electro-Fenton process

2019

Abstract The electrochemical oxidation of organics in paper mill wastewater belonging to Halfa industries (Tunisia) was performed by galvanostatic electrolyses using electro-Fenton (EF) process. The effect of several operating parameters, such as applied current density, electrodes material, air pressure and the presence of sodium chloride (NaCl) was evaluated. In particular, carbon felt (CF), modified carbon felt (MCF) and gas diffusion electrode (GDE) were used as cathode while Ti/IrO2-Ta2O5 and Boron Doped Diamond (BDD) as anode. Total Organic Carbon (TOC) measure was chosen as reference parameter to assess the extent of the treatment. The experimental results show that, by adopting the …

Study of the Growth Mechanism of some Oxide Scales on Alloy 230 in High Temperature Vapor Electrolysis (HTVE) Conditions

2012

Alloy 230 (also named Haynes® 230) was tested as interconnect for production of hydrogen via High Temperature Vapor Electrolysis (HTVE). Samples were oxidized at 800°C in the both atmospheres representative of the HTVE operating conditions: Ar-1%H2-9%H2O (for cathode side) and air (for anode side). The high temperature oxidation behaviour was studied in both atmospheres together with the electrical conductivity of the thermally grown oxide scales. Oxidation kinetics indicated lower oxidation rate in H2/H2O compared to air (kp = 3.8 .10-15 g2.cm-4.s-1 in H2/H2O and kp = 1.6 .10-14 g2.cm-4.s-1 in air). The corrosion products were characterized by scanning electron microscopy associated with X…

Development and Scale-Up of the Electrochemical Dehalogenation for the Synthesis of a Key Intermediate for NS5A Inhibitors

2015

The electrochemical 2-fold dehalogenation of a spirocyclopropane-proline derivative at leaded bronze was scaled-up in a divided batch-type electrolysis cell in good yield and excellent selectivity. The upscaling via a flow electrolysis cell was also successful. Conditions were elaborated employing a single cell passage for complete conversion. The keys here are the direct cooling of the cathode and ensuring a good laminar flow.

First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO

2005

The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developped a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting de…