Title page for ETD etd-05272004-000606


Type of Document Master's Thesis
Author Dicic, Zorana
Author's Email Address zdicic@vt.edu
URN etd-05272004-000606
Title High Temperature Corrosion of Single Crystal Sapphire and Zirconia in Coal Gasification and Commercial Glass Environments
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Pickrell, Gary R. Committee Co-Chair
Wang, Anbo Committee Co-Chair
Kampe, Stephen L. Committee Member
Keywords
  • sapphire
  • reaction kinetics.
  • corrosion rate
  • corrosion
  • coal gasifier
  • coal slag
  • soda lime glass
  • alumina
  • zirconia
Date of Defense 2004-05-22
Availability unrestricted
Abstract
To meet the requirements of precise temperature monitoring at high temperatures in extremely corrosive environments, such as in coal gasifiers, a new sensor technology has been developed. This optical, ultra high temperature measurement system utilizes single crystal sapphire as a sensing element. A series of experiments was performed to determine the corrosion resistance of single crystal sapphire and single crystal fully stabilized cubic zirconia at high temperatures in coal slag and soda lime glass. The amount of corrosion of sapphire and zirconia in corrosive slags was measured at 1200oC, 1300oC, and 1400oC for different exposure times. The microstructural features at the interface of sapphire and zirconia were investigated using SEM and EDX analysis. The experimental measurements as well as SEM micrographs show very little or no degradation of sapphire and zirconia samples in corrosive slags. An interesting phenomenon was observed in the EDX scans of sapphire in the coal slag: the iron from the slag appears to have completely separated from the silicon and deposited at the sapphire surface. This interesting observation can be further explored to study whether this iron layer can be used to control the corrosion of sapphire.
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