Detection of explosives vapours on quartz crystal microbalances: generation of very low-concentrated vapours for sensors calibration

AbstractA controlled vapours generator of explosives compounds has been evaluated for delivering low-concentrated vapours in order to determine the threshold of quartz crystal microbalances based chemical gas sensors

Low temperature dynamics of small γ\gamma-Fe2_203_3 particles

We have studied the response of a system of small (~ 4 nm) ferrimagnetic particles to a field reversal at low temperature (0.6 to 12 K). The reversal of the particle magnetic moments through the anisotropy barriers is shown to be governed by thermally activated dynamics down to 0.6 K, with no evidence for quantum effects. We propose a data analysis in terms of the unique variable $T \cdot Ln(t/{\tau_0})$, which accounts for a non-constant distribution of anisotropy barriers

Wet Chemistry of Spinel Iron oxide Particles

Various properties of spinel iron oxide nanograins are reviewed, illustrating the broad possibilities of wet chemistry for tailoring materials for a wide range of utilizations, from catalysis and sensors to cast magnetic materials

Matériaux cimentaires pour piégeage du césium et de l'iode

Pour la gestion des déchets, les matériaux cimentaires peuvent jouer le rôle de barrière chimique grâce à des réactions préférentielles qui limitent la dissémination des éléments polluants. Ces réactions interviennent au cours des processus d'hydratation du matériau cimentaire ou ultérieurement ; le matériau peut contenir des charges réactives. Enfin, il est possible de céramiser le matériau cimentaire pour former des phases minérales de stabilité accrue. L'illustration est faite pour le cas du césium, et les perspectives sont situées pour l'iode

Ageing of thin films used in explosives detection

International audienceThe ageing of fluorescent materials (phenyleneethynylene) has been studied to evaluate there lifetime as chemical sensors and to identify the ageing mechanism

Ultra trace detection of explosives in air: development of a portable fluorescent detector.

International audienceThis paper describes a system for the detection of nitroaromatic explosives consisting of a portable detector based on a specific fluorescent material. The developed sensor was able to perform an ultra trace detection of explosives, such as trinitrotoluene (TNT) or its derivate 2,4-dinitrotoluene (DNT), in ambient air or on objects tainted with explosives. In the presence of nitroaromatic vapors, the fluorescence of the material was found to decrease due to the adsorption of nitroaromatic molecules on its specific adsorption sites. The sensor exhibited a large sensitivity to TNT or DNT at their vapor pressures (respectively 6 and 148 ppbv) and the detection threshold was evaluated on a laboratory test setup and was found to be 0.75 ppbv for TNT. Moreover, the detector demonstrated no loss of performance in the presence of humidity or interfering compounds. All the tests led to the conclusion that the sensor fulfills the main requirements for the identification of suspect luggage, forensic analyses or battlefields clearing