The operational environment of colloid thrusters is high vacuum (10-3 _ 10-6 mbar) however, much of the experimental data collected to date to identify parameter relationships in cone jet mode electrosprays (ES), such as current-volumetric flow rate scaling laws, has been conducted in atmospheric conditions. This highlights a need for electrospray data under high vacuum conditions. Electrospray experimental data was collected using medium conductivity solutions (0.0025 -0.0160 S/m) of TEG doped with sodium iodide in high vacuum. These sprays were obtained from a stainless steel capillary and a disk counter electrode with central aperture. An online flow measurement system is described, which has been developed during this research to measure the fluid volumetric flow rate, concurrently with applied voltage and spray properties such as spray current and cone, jet and spray geometry. This automated flow measurement system was used to measure flow rates as low as InUs with an absolute accuracy of 0.3nUs and a resolution of 0.03nus. It is identified that this system may be easily adapted for lower flow rates and higher resolutions. The ES data collected demonstrates, for the first time, the detailed dependence of volumetric flow rate upon the applied voltage. The sensitivity of nominal flow rate to applied voltage was found to be higher for lower nominal flow rates. For a volumetric flow rate -4nLIs a 25% a change in flow rate per kV was recorded over a cone-jet mode stability range spanning -1.5kV. This volumetric flow rate voltage sensitivity holds particular significance for colloid thruster systems, which operate at or near minimum flow rate conditions. The current was found to have a power law dependence on flow rate similar to the current scaling laws of F. de la Mora and Gahan-Calvo however the exponent of this power law differs significantly from these scaling laws. A study considering the effect of charge carrier mobility in simple 1: 1 electrolytes shows that the exponent of the power law current-flow rate scaling increased with increasing charge carrier mobility. Contrary to the various scaling laws the spray current was found to be dependent on electrostatic conditions. The sensitivity of the emitted current to the applied voltage was also found to increase with increasing nominal volumetric flow rate. The geometrical parameters of cone angle, spray angle and jet length were measured for varying TEG/Nal solution conductivity. Cone geometry was found to be relatively independent of conductivity in the range tested. Jet length was found to have an inverse relationship with solution conductivity.

Des couches minces d'oxyde de vanadium, V2O5, ont été déposées à température ambiante sur substrat ITO/verre en utilisant trois conditions de dépôt différentes, à savoir la pulvérisation cathodique par magnétron haute fréquence (RFMS) avec cible métallique en V (métal V2O5RF) et cible d’oxyde de V2O5 (oxyde V2O5RF) et la pulvérisation cathodique par magnétron en régime d’impulsions de haute puissance (HiPIMS) avec cible métallique (V2O5HiPIMS), respectivement. L’optimisation des différents paramètres de dépôt conduit à une modulation de la structure et morphologie des films, d’amorphes à cristallisés et de denses à poreux. Le cyclage en milieu lithié ou sodé montre un multichromisme associé à un changement réversible de coloration impliquant 4 couleurs, orange, vert, bleu et gris, en fonction des états de réduction et d’oxydation. Un cyclage prolongé sur 1000 CV, indique une différence de stabilité en fonction de la méthode de dépôt. Les films denses déposés par HiPIMS présentent une grande stabilité tandis qu’une dégradation très rapide est observée pour les films amorphes (oxyde V2O5RF) et qu’une augmentation de capacité est observée pour les films (métal V2O5RF). Ces différences de comportement sont attribuables à des différences de morphologie faisant apparaitre des films fissurés et fragiles dans un cas et denses sans grande évolution dans l’autre cas. Par ailleurs, le cyclage longue durée entraine une amorphisation des films. La caractérisation par un grand nombre de techniques (GIXRD, XPS, TOF-SIMS, AES et RBS / NRA) des différents comportements au cours du processus électrochrome a mis en évidence que le mécanisme ne peut être simplement décrit par une unique réaction d’insertion/désinsertion. Les propriétés électrochromes prometteuses des couches unitaires de V2O5 (métal V2O5RF) ont permis leur intégration dans des dispositifs complets à base d’électrolyte transparent ou opaque. Ainsi, des dispositifs WO3/V2O5 et V2O5/V2O5 ont été caractérisés pour des applications vitrage et afficheur. / Vanadium oxide thin films were deposited on ITO coated glass substrate at room temperature using three different deposition conditions, namely radio frequency magnetron sputtering (RFMS) with V metallic target (V2O5RF-metal) or V2O5 oxide target (V2O5RF-oxide) and High Power Impulse Magnetron Sputtering (HiPIMS) with V metallic target (V2O5HiPIMS), respectively. Significant difference in structure and morphologies are reported. V2O5RF-metal films are crystalline and dense with a disturbed surface which is thickness dependent, while V2O5RF-oxide and V2O5HiPIMS films are amorphous and porous or dense respectively. V2O5 thin films show reversible electrochromism with 4 colors, which are orange, green, blue and gray, in reduction/oxidation states when cycled in Li and Na based electrolytes. However, depending on the deposition method, V2O5 films show different cycling stability, recorded up to 1000 cycles, that is attributed to a modification of the morphology (i.e. increase of the surface area due to cracks and increase porosity, as well as a progressive amorphization particularly in lithium electrolyte. The different behaviors during the electrochromic process were investigated with GIXRD, XPS, TOF-SIMS, AES and RBS/NRA indicating a mechanism more complex than a simple insertion/deinsertion. Finally, two types of ECDs using either transparent electrolyte membrane or opaque are fabricated coupling V2O5 thin films to WO3 or to V2O5 in a symmetrical device aiming at application in smart windows and displays, respectively.

Ce mémoire traite de la mise au point et des applications d’un fluxmètre gazeux à pression constante, instrument de référence primaire pour la mesure de très faibles débits gazeux, couramment utilisé par les Laboratoires nationaux de métrologie. Il intervient dans la traçabilité des basses pressions absolues, via la méthode d’expansion continue, et celle des fuites d’hélium, liées aux applications dans le domaine du vide. De plus, nous avons montré que le fluxmètre à pression constante du Laboratoire commun de métrologie (LCM) permettait le raccordement des mesures de micro-débits, sous-domaine de la débitmétrie. Outre les points clés de la conception et la caractérisation métrologique, ce mémoire décrit l’étude de l’expansion continue ainsi que les travaux de comparaison du fluxmètre gazeux à pression constante avec les méthodes de référence employées au LCM, en particulier la méthode de gravimétrie dynamique. / This dissertation concerns the development and applications of a constant pressure gas flowmeter, the primary reference instrument used by National metrology laboratories to measure very low gas flows. It guarantees the traceability of low absolute pressures, via the continuous expansion method, and that of helium leaks, both related to applications in the field of vacuum. In addition, we have shown that the Laboratoire commun de métrologie (LCM) constant pressure flowmeter is well suited to micro-flow measurements, a sub-field of flow metering. Besides key points of the design and metrological characterization, this document describes the study of the continuous expansion method and work on comparisons of the constant pressure gas flowmeter with reference methods used at LCM, in particular the dynamic gravimetric method.