Thermal Spray Processing of Ceramic Oxide Coatings: An Integrated Approach

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Authors
Colmenares Angulo, Jose Rafael
Issue Date
1-Dec-10
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Dissertation
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en_US
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Abstract of Dissertation: Thermal Spray Processing of Ceramic Oxide Coatings: An Integrated Approachby Jose Rafael Colmenares AnguloDoctor of Philosophy in Materials Science and EngineeringStony Brook University 2010Thermal spray represents a complex processing technology given the stochastic nature of rapid splat melting, impact and solidification. The present work represents a series of studies with the aim of improving the understanding of process-property relationships on ceramic oxides integrating recent work from the Center of Thermal Spray Research regarding particle and non-particle state issues intrinsic to thermal spray processing with material specific applicationsIssues regarding reliability of two-wavelength pyrometry and time-of-flight methods for thermal spray sensing are analyzed using a simultaneous comparative approach for HVOF and APS techniques with 5 different commercial sensors. Injection visualization techniques are included to analyze particle-plume interactions and the limitations of commercial ensemble measurements for first order process maps and repeatability measurements are discussed.Titanium dioxide coating formation mechanisms are examined with a wide range of process techniques and conditions applying an extended process map approach. Routes for coating formation from a microstructural, crystalline and stoichiometric perspective are correlated to issues of photocatalytical, electrical and thermal transport. The role of deposition rate as a key parameter in defining coating stress state is discussed, while particle state variations are found to be more significant in controlling phase content and transport properties. A key finding of this work is that the stochiometric distortions on TiO2 induced by thermal spray processing have a higher effect on coating photocatalytical activity than the fraction of metastable anatase phase.Novel techniques and applications are analyzed from a process oriented perspective including characterization of individual splats and ensemble coating properties. Precursor/Solution thermal spray coating and splat morphological characteristics are attributed mainly to atomization issues. 1st and 2nd order process maps of alumina-chromia coatings for fluorescent mapping of accelerated proton beams where constructed with the aim of increasing the fraction of the stable alpha phase and optimizing coating luminescence for the intended application
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The Graduate School, Stony Brook University: Stony Brook, NY.
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