Contribution à la microanalyse X des revêtements superficiels. Application aux biomatériaux

L objet de l étude concerne la caractérisation physico-chimique des revêtements superficiels par microanalyse x et son application a l étude des revêtements prothétiques phosphocalciques. Nous avons étudies les mécanismes de formation des phosphates de calcium par electrodeposition. Nous avons vérifie les hypothèses avancées par une étude portant sur l influence de la densité de courant sur les phosphates de calcium électrodéposés. Pour caractériser ces revêtements, nous avons développé une méthodologie en microanalyse x basée sur la complémentarité de la microscopie électronique a balayage et de la microscopie électronique a balayage transmission. Par la suite, nous nous sommes intéressés aux cartographies quantitatives des films minces sur substrats. Nous avons illustre l impact de l hétérogénéité du substrat sur la quantification des films minces ; puis, nous avons présente TF_Quantif, l algorithme de quantification (concentrations et épaisseurs) que nous préconisons pour s affranchir de ces problèmes. Nous avons aussi mené une étude théorique pour déterminer les limites d application de TF_Quantif. Enfin, nous avons présenté les développements logiciels et instrumentaux nécessaires a l utilisation de TF_Quantif et nous avons effectue des profils et cartographies quantitatifs sur des films minces (de composition et d épaisseur connue) sur substrats hétérogènes ainsi que sur un revêtement de phosphate de calcium. Les résultats ont été compares avec ceux obtenus par un logiciel de quantification que nous avons développé a partir du logiciel commercial STRATAGem (SAMx, France).This work deals with electron probe microanalysis of thin films and its application to thickness and concentration determination in the case of prosthetic calcium phosphate coatings. In a first part, we have studied the formation mechanisms of calcium phosphate elaborated by electrodeposition. We carried out a methodology based on the complementarities of scanning electron microscopy and scanning transmission microscopy both associated to x-ray microanalysis. This method allowed us to verify our hypothesis about calcium phosphate formation and showed that the current density is directly connected to the kind of electrodeposited calcium phosphate. In a second part, we have carried out quantitative elemental mapping of thin film on heterogeneous substrate. Through different examples, we showed that substrate heterogeneity has a direct influence on the thin film quantification. We developed a new quantification algorithm called tf_quantif which allows us removing substrate effects during the analysis associated to a theoretical approach which determine the thickness limit of this method. Moreover, we presented the quantification software and experimental setup developed in order to use tf_quantif . Finally, we applied tf_quantif on quantitive profiles and maps on several kinds of thin films on heterogeneous substrate (including electrodeposited calcium phosphate coatings). The results were compared to those obtained from commercial software (stratagem, samx, france). We showed that our quantification algorithm gave better results in the case of thickness determination and could be successfully applied in the case of quantitative maps of thin film on heterogeneous substrate.REIMS-BU Sciences (514542101) / SudocSudocFranceF

Laser diode absorption spectroscopy for accurate CO₂ line parameters at 2 μm: consequences for space-based DIAL measurements and potential biases

International audienceSpace-based active sensing of CO2 concentration is a very promising technique for the derivation of CO2 surface fluxes. There is a need for accurate spectroscopic parameters to enable accurate space-based measurements to address global climatic issues. New spectroscopic measurements using laser diode absorption spectroscopy are presented for the preselected R30 CO2 absorption line ((2001)III←(000) band) and four others. The line strength, air-broadening halfwidth, and its temperature dependence have been investigated. The results exhibit significant improvement for the R30 CO2 absorption line: 0.4% on the line strength, 0.15% on the air-broadening coefficient, and 0.45% on its temperature dependence. Analysis of potential biases of space-based DIAL CO2 mixing ratio measurements associated to spectroscopic parameter uncertainties are presented

From microbiological to ecosystemic scale evaluation of carbon-based (CO2, CH4) greenhouse gas sources, production, and transfers in temperate peatlands: a pluridisciplinary week at the playground for Critical Zonists in Frasne, Jura Mountains

International audienceDespite covering only 3% of the global land surface, peatlands are an active part of the Critical Zone (CZ) exchanging large water and greenhouse gas (GHG) fluxes with the surrounding aquifers, surface waters, and the atmosphere. While ecosystem services of peatlands (carbon and water storage, buffering of local climate) are essential to address 21st century challenges regarding climate, biodiversity, and water resources, they are directly threatened by human activities at global (climate change) and local (drainage for agriculture, forestry and peat harvesting) scales. Understanding the hydrological, biogeochemical, and ecological mechanisms of peatlands functioning at different spatiotemporal scales is therefore fundamental to mitigate these impacts. In order to characterize the mechanisms and factors controlling GHG sources, production and transfers in peatlands, we organized an interdisciplinary field campaign at the Frasne peatland. The site (7 ha, 46.826 N, 6.1754E, 840 m a.s.l) is a long-term observatory since 2008 and one of the four French peatland observatories (SNO Tourbi`eres) of the French CZ research infrastructure (OZCAR). The peatland is also an observatory of the Zone Atelier of Arc Jurassien dedicated to exploring the interrelationships between human and nature.This campaign is supported by the TERRA FORMA project, aiming at designing and testing in-situ smart, connected, low-cost, low-impact and socially appropriated environmental sensors to capture the trajectory of the CZ in the Anthropocene. This field campaign will combine microbiological characterization (membrane lipid analysis to trace the involved microbial metabolisms) with hydrogeochemical analyses of peat pore water (major elements, DOC (quantity and quality), CO2, CH4, δ18OH2O-δ2HH2O, δ13CDIC, δ13CDOC, δ13CCH4, δ2HCH4, δ13CCO2) along upstream-downstream and surface-depth gradients. In parallel, GHG fluxes will be measured from the plot to the ecosystem scale, by combining dissolved gas profiles, chamber measurements, eddy-covariance and unmanned aerial vehicle characterization. This multiscale campaign will have the potential to address various challenges faced by Critical Zonists and environmental managers: (1) assessing 3D carbon fluxes (lateral and vertical) at the peatland scale; (2) characterizing biological processes and in particular how they favor or limit GHG production; (3) and transfers and developing affordable and user-friendly tools to face the above-mentioned topics