Systèmes micro-nano-structurés et couches minces multifonctionnels, à base de dioxyde de ruthénium : élaborations et propriétés catalytiques et électriques

摘要

In this work, we present studies on nanomaterials and thin layers based on ruthenium oxides and having interesting catalytic and electrical properties. These materials are multifunctional and might be devoted to various applications as well for microelectronic or microsensor applications as for chemistry (catalysis, methane conversion). The study develops relations between elaborations microstructures and catalytic and electric properties. The RuO2 nanopowders elaborated by sol gel have interesting catalytic properties for methane or CO conversions. Structural refinements (Rietveld method applied to XRD analyses) have shown some correlation between lattice parameter variation and crystallite size effects. Transmission Electron Microscopy allowed confirming the XRD results on crystallite sizes. The catalytic efficiency was determined from infrared spectroscopy as a function of temperature and exposition time during solid gas interaction. The conversions of CH4 and CO into CO2 were observed above 200°C for CH4 and room temperature for CO. A semi empirical model for conversion rate was proposed and allowed to simulate a large variety of behaviors as a function of time. Studies of thin layers based on RuO2 phase and on RuO2 - CeO2 composites were carried out first by spin coating then by rf sputtering. The spin coating RuO2 layers present a catalytic activity linked to their porosity. They present a non linear electrical behavior strongly depending on microstructure and composition. A power law model was successfully applied to describe the composition dependence. These layers might be used in piezoresistive devices. A specific device allowing integration of these materials is also described as a first step for fabrication of a multisensor prototype.