0000000000222022
AUTHOR
J. Jouhannaud
Rapid synthesis of tin (IV) oxide nanoparticles by microwave induced thermohydrolysis
Abstract Tin oxide nanopowders, with an average size of 5 nm, were prepared by microwave flash synthesis. Flash synthesis was performed in aqueous solutions of tin tetrachloride and hydrochloric acid using a microwave autoclave (RAMO system) specially designed by the authors. Energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, nitrogen adsorption isotherm analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM), were used to characterize these nanoparticles. Compared with conventional synthesis, nanopow…
Experimental approach of the interaction between a sub-microscopic cathode tip and the plasma
The interaction between electrical arc and cathode represents a crucial problem in the conception of arc jet thrusters, circuit breakers, and plasma torch or arc heaters. At the cathode surface, the current and energy transfers are controlled by the current emitting site (cathodic spot). Theories and experimental observations, at macroscopic and mesoscopic scale, deal with the erosion of the cathodic surface. Under micrometer range, theories refer to the arc root to describe the erosion of the surface. The works presented here propose an original method to evaluate the arc-cathode interaction at micrometric scale. A nanotechnology is used in order to control the roughness of the electrode s…
Développement d'un nouveau capteur de gaz basé sur la détection à large bande micro-onde
Resume Nous presentons une methode originale de detection des gaz. Notre capteur se compose d'un materiau sensible introduit dans une structure coaxiale. Un champ electromagnetique (micro-ondes), emis a travers le capteur par un analyseur de reseaux vectoriel, sollicite le materiau sensible soumis a un gaz. La variation de la reponse du capteur observee est due aux variations des proprietes dielectriques du materiau sensible induite par l'adsorption du gaz. L'etude fait apparaitre que le capteur a base d'oxyde SrTiO3 est quantitatif et selectif pour trois gaz differents (eau, ethanol, toluene). Pour citer cet article : J. Jouhannaud et al., C. R. Physique 8 (2007).
Broadband microwave gas sensor: A coaxial design
The method of gas detection by a broadband microwave gas sensor is presented in this article. The principle of this method is to use a sensitive material as substrate of a transmission coaxial line. The sensor represents an open line with an extreme surface in contact with gas. The interaction with the gas and the surface induces a dielectric variation of the substrate. From experimental results, the interaction between the sensitive material and each tested gas present a specific frequency spectrum of the reflection coefficient at the input of the line. The proposed method has the advantage of a compact size, wide bandwidth, simple structure, and capable with all sensitive materials. © 201…