Date of Award
Doctor of Philosophy (PhD)
Vishnu K. Lakdawala
Linda L. Vahala
John B. Cooper
A new technique for continuous, real-time, in-situ detection of natural corrosion of aluminum alloys is presented. The technique is a generalized version of attenuated total reflectance (ATR) spectroscopy, that combines optical fibers and a Michelson interferometer spectrometer to make evanescent wave absorption measurements. Aluminum hydroxide is one of the major corrosion products of aluminum. Absorption spectra of powdered samples of aluminum corrosion, in the spectral region around three micrometers have been studied and compared with the spectra from pure powdered aluminum hydroxide. A chalcogenide optical fiber was used as an attenuated total reflectance (ATR) optical element. The same samples were studied using conventional ATR spectroscopy, with a zinc selenide crystal optical element as a reference. The corrosion samples are from different aircraft components. The corrosion samples showed spectral features such as positions, widths, and shapes similar to those of aluminum hydroxide. Five spectral features are identified in aluminum hydroxide in the spectral region from 3300 to 3650 cm-1. Two spectral features are identified in the data for aluminum corrosion in the same spectral region. Absorptance was determined in each case. The experimental results from pure aluminum hydroxide and aluminum corrosion agree with the theoretical values. However for the fiber case, those values are lower than theoretical values. This discrepancy is due to the conditions under which radiation is launched into the fiber.
Namkung, Juock S..
"Optical Fiber Fourier Transform Infrared Evanescent Wave Absorption Spectroscopy of Aluminum Hydroxide and Natural Corrosion"
(1996). Doctor of Philosophy (PhD), Dissertation, Electrical/Computer Engineering, Old Dominion University, DOI: 10.25777/yw0h-4a98