Search results for "Metals and Alloys"
showing 10 items of 1325 documents
Chemistry of lanthanide–metal carbonyl systems: the ytterbium–chromium carbonyls interaction
2001
Abstract The interaction of the chromium carbonyl hydrides HCr2(CO)10− or HCr(CO)5− with Yb(acac)3·3H2O has been investigated, and the experimental conditions leading to the isolation of ytterbium–chromium carbonyl complex species are reported. Formulation of the coordination compounds produced by such interactions has been proposed on the basis of analytical data and IR spectroscopy.
Investigation of the SHS mechanisms of titanium nitride by in situ time-resolved diffraction and infrared thermography
2007
Abstract The self-propagating high-temperature synthesis (SHS) or combustion synthesis is a promising process to produce advanced ceramics due to the high purity of the elaborated materials and the very short synthesis time. Titanium nitride has been synthesised from pressed titanium powder and a nitrogen gas flow under a 0.1 MPa pressure. The influence of the addition of a TiN diluent was investigated. For the first time, SHS reaction mechanisms were determined from in situ time-resolved X-ray diffraction (TRXRD) experiments using the synchrotron radiation. These experiments were coupled with infrared thermography to study the propagation of the combustion reaction. It appeared that the in…
Suivi de l'endommagement dans les structures en composites par une analyse optique in-situ
2009
National audience; Ce travail présente une technique de détection et de suivi de l'endommagement dans les structures en matériaux composites. Les mécanismes d'endommagement dans ces matériaux sont complexes. Dès lors que l'on souhaite modéliser le comportement d'une structure, il est important de comprendre comment celle-ci s'endommage. La méthode optique d'observation in-situ proposée est appliquée au cas d'une plaque trouée.
A physical-based constitutive model for surface integrity prediction in machining of OFHC copper
2017
International audience; Due to the rising interest in predicting machined surface integrity and sustainability, various models for metal cutting simulation have been developed. However, their accuracy depends deeply on the physical description of the machining process. This study aims to develop an orthogonal cutting model for surface integrity prediction, which includes a physical-based constitutive model of Oxygen Free High Conductivity (OFHC) copper. This constitutive model incorporates the effects of the state of stress and microstructure on the work material behavior, as well as a dislocation density-based model for surface integrity prediction. The coefficients of the constitutive mod…
Terpyridine-based metallopolymer thin films as active layer in ammonia sensor device
2016
International audience; A metal-containing polymer has been prepared by electropolymerization of an homoleptic Ru(II)-terpyridine complex bearing pyrrole heterocycles. The polymer is obtained as a thinfilm at the surface ofelectrodes, and has been characterized by electrochemical measurements, XPS and microscopy. It hasbeen shown that this polymer acts as an active gas sensitive layer since it enables the detection of anammonia gasflow through layer’s resistivity measurements.
Gas sensors arrays (electronic noses) : a study about the speed/accuracy ratio
2000
Abstract New Fingerprint Mass Spectra (FMS) systems claim for a higher precision, a reduced analysis time, and a lower drift, compared with Gas Sensors Arrays ‘Electronic Noses’. We demonstrated in this study that metal oxide gas sensors may have highly improved performances for both accuracy and run time, when used in optimum conditions. The different noise components were quantified referring to popular words (equivalent of ethanol concentration) using the transfer function of the sensor. It was pointed out that sample surrounding greatly affects the noise level, and that the signal-to-noise ratio may be dramatically increased, reducing the distortion generally assessed between sensor and…
Electronic noses : specify or disappear
2000
Abstract When the quality control is achieved by using GC or GC/MS, the apparatus must comply with the applicable norms, but what about “electronic noses”? End users demand for formal specifications for selectivity, sensitivity, repeatability and sample throughput. The behavioural modelling of electronic olfactometers may provide specifications for these required parameters. This will allow both the measure itself, and evaluate the influence of the experimental errors on the sample classification. Users may expect to find a methodology allowing the performances of systems to be checked before any final decision and during routine use. We have demonstrated that the system sensitivity and log…
Combustion wave structure during the MoSi2 synthesis by Mechanically-Activated Self-propagating High-temperature Synthesis (MASHS): In situ time-reso…
2006
Abstract In situ synchrotron time-resolved X-ray diffraction experiments coupled with an infrared imaging camera have been used to reveal the combustion wave structure during the production of MoSi2 by Mechanically Activated Self-propagating High-temperature Synthesis (MASHS). The fast combustion front exhibits a form described as an ‘equilibrium structure’ where the chemical reaction is the sole major driving force. In the MASHS process, oxide-free interfaces between Mo and Si nanocrystallites enhance the reaction Mo+2Si→MoSi2. Exhaustive time-resolved investigations show a possible solid-state process in the first second of the reaction within the combustion front. If preheating is added,…
Influence of interfering gases on a carbon monoxide differential sensor based on SAW devices functionalized with cobalt and copper corroles
2021
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Immobilization of single-stranded DNA fragments to solid surfaces and their repeatable specific hybridization : covalent binding or adsorption ?
2004
Abstract The different steps of the immobilization process of single-stranded DNA (ssDNA) on surfaces by means of chemical grafting have been investigated using systematic measurements of grafting and hybridization densities by means of radioactive labelling. The immobilization by chemical grafting to a dense monomolecular layer of N-hydroxysuccinimidyl ester reactive functions attached to silica plates was performed from a dilute solution of amino-terminated oligonucleotides (10 μmol/l). The slow evaporation of the solvent allowed to increase the DNA grafting density by a factor of 10. A precise control of the rinsing process that followed the immobilization reaction allowed the discrimina…