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Title: Photothermal studies of surfaces subjected to harsh environments
Author: Zakaria, A. B.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1993
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In this thesis we have been concerned with photothermal studies of surfaces subjected to harsh environments. In the context of harsh environments we have concentrated on the deleterious effects that atomic oxygen (ATOX) has on different materials. In order to study such effects an ATOX source has been developed which is capable of producing an ATOX flux of 1.5 x 1017 atoms/cm2s when operating at a pressure of 1 to 2 Torr. The characteristics of the source have been studied and the erosion effects on materials at various material temperatures and ATOX fluences have been measured. The erosion in materials may be stopped by coating with gold. However, imperfections in the coating may provide erosion sites. In order to study this, coated polymers were deliberately scratched and exposed so that the damaged areas were eroded and at longer exposures the coatings were found to be undercut at the damage sites. The development of the undercut sites has been monitored by using two dimensional photothermal scans after each exposure to ATOX. Materials studied were Kapton, graphite, Mylar and multi-layered Kapton. For coated Kapton, various conditions of coating imperfection have been studied. The increase of photoacoustic (PA) signal with fluence indicates that during exposure volatile material contaminates the coating surface. At the intact area near the deliberately scratched gold-coated sample there is a disbonded coating due to ATOX attack which increases the PA and decreases the piezoelectric (PZT) signals. The PZT scanned phase images are used to determine the undercut boundary while the scanned magnitude images are used to determined the undercut depth at the opened area, both the width and the depth measurements being cross checked with a profilometer after the final exposure. The new method of scanning by using an open PA cell has been introduced which is inexpensive and suitable for successive ATOX exposures and subsequent scanning.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available