A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of CeO2 powders produced from dissolved cerium nitrate salts. The reactor minimized particle recirculation and provided a highly symmetric and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of CeO2 powders. The sampling probe provided in-situ sampling of in-flight CeO2 particles and allowed continuous sampling without cross contamination. The sampled particles were collected using a wet collection system composed of a mist atomizer acting as a scrubber and a custom-made spray chamber. The entire collection system is portable and it was tested in the particle range of 20 nm to 100 mum. This information provided a picture of how CeO2 particles were formed. A numerical simulation of different plasma operating parameters using Fluent was presented. A comprehensive droplet-to-particle formation mechanism was deduced based on calorimetry, thermodynamics of CeO2 formation, numerical simulations and collected particles. The effect of adding water soluble fuels (alanine and glycine) to the original cerium nitrate solutions was investigated. Fuel addition decreased the temperature of CeO2 formation by acting as a local heat source as a result of fuel auto-ignition. The addition of fuel caused "particle size discrimination", and a single mode particle size distribution centered between 50-140 nm was achieved along the centerline of the reactor. / Also, heat and mass transfer effects were numerically investigated in evaporating solution droplets (20-40 mum in diameter) containing dissolved hexahydrated cerium nitrate in a stationary rf Ar-O2 thermal plasma. This model was developed to study the evaporation of a solution droplet surrounded by a porous crust in a stagnant rf Ar-O2 thermal plasma under reduced pressure. It considered a three phase system: a liquid core of dissolved Ce(NO 3)3.6H2O in water, a dry porous crust of homogeneously precipitated spherical crystals of equal size, and an Ar-O2 plasma under reduced pressure. The impact of different plasma operating parameters on the temperature and dissolved solid content profiles in the droplet was studied, i.e. surrounding plasma temperature, initial salt content and droplet size, plasma gas composition, and system pressure. Temperature and composition dependant thermophysical properties were used. The model was solved in a moving boundary frame using an ALE approach and considering Stefan flow. It provided the necessary information to understand the droplet to particle transformation steps in regions where in-flight probing was unfeasible, i.e. torch zone.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.111890 |
| Date | January 2007 |
| Creators | Castillo Martinez, Ian Altri. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002666868, proquestno: AAINR38566, Theses scanned by UMI/ProQuest. |
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