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Title: Study of early electrical aging of polyethylene using electroluminescence technique
Author: Wong, Kiing Ing
ISNI:       0000 0001 3571 5450
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2003
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Electroluminescence is defined as light emission resulting from the application of an electrical field to solid state materials. Electroluminescence has been used to study charge injection and recombination phenomena and its use as a probe to study electrical aging mechanisms of insulating polymers. EL provides information on charge trapping centres within the polymer which will change with ageing and degradation of the polymer. However, in the literature, the measured electroluminescence of insulating polymers by different researchers are different and the electroluminescence excitation mechanisms have not been fully understood. A charge couple device (CCD) camera has been used to detect several electroluminescence characteristics: electroluminescence spatial distribution, temporal behaviour, spectral resolution and phase angle relationship with respect to a 50Hz applied ac voltage. In the latter case, the new technique, employing a CCD camera offers significant advantages on traditional methods where a photomultiplier was used as the optical detection. The electroluminescence characteristics of thin film polyethylene samples have been investigated as a function of applied voltage, sample thickness, electrode materials and electrode coating method.  It was found that two types of electroluminescence could be produced, homogenous and inhomogenous, depending on the number of surface defects present on the samples. These two types of electroluminescence have different spectra indicating that field enhancement of defects leads to charge being injected further into the bulk of the polymer. It was also found that different electrode metals, and in particular the coating method (sputtered or evaporated) leads to significant differences in the electroluminescence intensity that cannot be related to work functions of these materials alone. It is concluded that the evaporation method leads to a greater diffusion of metal atoms into the polymer and these impurities act as charge recombination centres for electroluminescence.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available