Study of Transport Properties of Tantalum Pentoxide for High Temperature Thermal Management and Water Purification Systems
Chandrasekharan, Ramesh
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Permalink
https://hdl.handle.net/2142/72227
Description
Title
Study of Transport Properties of Tantalum Pentoxide for High Temperature Thermal Management and Water Purification Systems
Author(s)
Chandrasekharan, Ramesh
Issue Date
2008
Doctoral Committee Chair(s)
Shannon, Mark A.
Department of Study
Mechancial Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Abstract
The convolution of heat and mass transfer with material properties is an important issue in the design and operation of many different engineering systems. Two semiconductor oxide systems based on Ta2O5, one a high temperature radiative thermal management system and the other a photocatalytic water purification system, are explored. Of particular importance in designing and engineering such systems is the ability to identify and estimate both the relevant transport (heat, mass and reactive species transfer) properties and the convolution of these transport phenomena with the material parameters. This research explores both the experimental aspects and the analyses required to estimate the transport properties of Ta2O5 as applicable to the two systems of interest. The high temperature thermal management system for a microcombustor presented here is essentially a 1-D photonic structure consisting of alternating layers of Ta2O5 and SiO 2. A combination of multiple angle FTIR spectrometry, reactive-diffusive modeling and thin-film elemental spectroscopy (Auger, XPS) is used to quantify reactive diffusion coefficients and high temperature IR optical properties of Ta2O5. The temperature induced changes in material composition are convolved with the changes in IR optical properties. This is shown by quantifying the changes in IR reflectance and optical properties brought about by crystallization and the formation of an interfacial layer between films or between film and substrate. The photocatalytic water purification system considered in this study is based on nano-sized Ta2O 5 supported on SiO2 nanoparticles or a nitrogen doped version of the same. In this study an experimental methodology to compare different photocatalysts by accounting for the interaction of light, reactive species transport and photoactive properties of the photocatalyst particles is devised. By using this experimental system, the photochemical and photoelectrical properties of Ta2O5 decorated on SiO2 and nitrogen doped Ta2O5 are quantified.
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