Search results for "Coupled"
showing 10 items of 742 documents
Modeling the Interaction of Carbon Monoxide with Flexible Graphene: From Coupled Cluster Calculations to Molecular-Dynamics Simulations
2018
The interaction of CO with graphene was studied at different theoretical levels. Quantum-mechanical calculations on finite graphene models with the use of coronene for coupled cluster calculations and circumcoronene for B97D calculations showed that there was no preferential site for adsorption and that the most important factor was the orientation of CO relative to graphene. The parallel orientation was preferred, with binding energies around 9 kJ mol-1 at the CCSD(T) and B97D levels, which was in good agreement with experimental findings. From a large number of CO-circumcoronene and CO-CO interactions, computed at different distances and randomly generated orientations, parameters were fi…
Advanced numerical models for the thermo-mechanical-metallurgical analysis in hot forging processes
2013
In the paper a literature review of the numerical modeling of thermo-mechanical-metallurgical evolutions of a metal in hot forging operations is presented. In particular models of multiaxial loading tests are considered for carbon steels. The collected examples from literature regard phases transformations, also martensitic transformations, morphologies evolutions and transformation plasticity phenomena. The purpose of the tests is to show the correlation between the mechanical and the metallurgical behavior of a carbon steel during a combination of several types of loads. In particular a few mechanical tests with heat treatment are analyzed. Furthermore, Ti-6Al-4V titanium alloy is conside…
Electrochemical and Spectroelectrochemical Behavior of a Tetracyanotriphenodioxazine in Solution and Thin-Films
2018
International audience; We report the electrochemical behavior of a tetracyano triphenodioxazine bearing two triisopropylsilylethynyl moieties (TiPS‐TPDO‐tetraCN) during its reduction studied either in solution or after vacuum evaporation deposition on indium tin oxide (ITO) support. While in dichloromethane, it typically proceeds in two successive monoelectronic reactions, in acetonitrile, the mechanism appears more complex. Fine analysis of the spectroelectrochemical results combined with simulation of the voltammograms with various amount of water suggest the involvement of water and of a restructured dianion in the electrochemical process. In the solid‐state, the formation of the diprot…
Photoinduced Electron Transfer Reactions in a Porphyrin−Viologen Complex: Observation of S2 to S1 Relaxation and Electron Transfer from the S2 State
1999
Photoinduced Energy Transfer Reactions in a Porphyrin-Viologen Complex: Observation of S2 to S1 Relaxation and Electron Transfer from the S2 state
Thermal and infrared spectroscopic characterization of historical mortars
1998
Abstract The characterization of historical mortars was performed by thermal analysis (TG-DTG), simultaneous infrared spectroscopy (TG-FTIR) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The samples were taken from St. John Church (Tartu, Estonia), built in the 13th–14th centuries. The analyses are important for the restoration of the church. In reality, mortar is a very difficult system, the lime is accompanied with different hydraulic components. TG-DTG analysis and FTIR methods can be used to identify various components of mortar and to observe the reactions associated with the controlled heating at 25–900°C in dynamic air and nitrogen atmosphere. The elemental c…
Ultrasonic detection by photo-EMF sensor and by wideband air-coupled transducer
2004
Two non-contact remote ultrasonic detection systems are compared. The first consists of a continuous wave (CW) Nd:YVO4 laser operating at 532 nm used in conjunction with a photo-induced electromotive-force (EMF) sensor. The second system employs an air-coupled capacitance transducer that has a bandwidth from 100 kHz up to 2 MHz. Both systems exhibit higher sensitivity to out-of-plane than in-plane measurements of stress wave signals. Ultrasound generation is carried out by an Nd:YAG pulsed laser at 532 nm in the thermoelastic regime in a 1.6 mm aluminum plate. A0 Lamb mode is generated at frequency-thickness product with strong out-of-plane displacements. Ultrasonic waveforms acquired are r…
New process of silicon carbide purification intended for silicon passivation
2017
Abstract In this work, we report on a new, efficient and low cost process of silicon carbide (SiC) powder purification intended to be used in photovoltaic applications. This process consists on the preparation of porous silicon carbide layers followed by a photo-thermal annealing under oxygen atmosphere and chemical treatment. The effect of etching time on impurities removal efficiency was studied. Inductively coupled plasma atomic emission spectrometry (ICP-AES) results showed that the best result was achieved for an etching time of 10 min followed by gettering at 900 °C during 1 h. SiC purity is improved from 3N (99.9771%) to 4N (99.9946%). Silicon carbide thin films were deposited onto s…
Antenna-coupled spintronic terahertz emitters driven by a 1550 nm femtosecond laser oscillator
2019
We demonstrate antenna-coupled spintronic terahertz (THz) emitters excited by 1550 nm, 90 fs laser pulses. Antennas are employed to optimize THz outcoupling and frequency coverage of ferromagnetic/nonmagnetic metallic spintronic structures. We directly compare the antenna-coupled devices to those without antennas. Using a 200 μm H-dipole antenna and an ErAs:InGaAs photoconductive receiver, we obtain a 2.42-fold larger THz peak-peak signal, a bandwidth of 4.5 THz, and an increase in the peak dynamic range (DNR) from 53 dB to 65 dB. A 25 μm slotline antenna offered 5 dB larger peak DNR and a bandwidth of 5 THz. For all measurements, we use a comparatively low laser power of 45 mW from a comme…
Direct determination by portable ED-XRF of mineral profile in cocoa powder samples
2019
Abstract The present study has exploited the rapidity of the analysis and the multi-elemental capability of the energy dispersive X- ray fluorescence (ED-XRF) technique for the mineral profile determination in cocoa powder. A fast, cheap and environmental sustainable method without reagent consumption or toxic waste generation has been proposed. The samples can be prepared in the form of pellets of 13 mm in diameter and 2–3 mm thickness. The different internal calibrations used by ED-XRF equipment did not provide accurate results when comparing the mineral profile with the concentration obtained by Inductively Couple Plasma Optical Emission Spectroscopy (ICP-OES) after microwave assisted di…
Room-temperature plasma-enhanced atomic layer deposition of ZnO: Film growth dependence on the PEALD reactor configuration
2017
Room-temperature plasma-enhanced atomic layer deposition (PEALD) of ZnO was studied by depositing the films using diethylzinc and O2 plasma from inductively-coupled plasma (ICP) and capacitively-coupled plasma (CCP) plasma source configurations. The CCP-PEALD was operated using both remote and direct plasma. It was observed that the films deposited by means of remote ICP and CCP were all highly oxygen rich, independently on plasma operation parameters, but impurity (H, C) contents could be reduced by increasing plasma pulse time and applied power. With the direct CCP-PEALD the film composition was closer to stoichiometric, and film crystallinity was enhanced. The ZnO film growth was observe…