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Title: Surface characterisation of modified pan based carbon fibres.
Authors: Osbeck, Susan
Supervisors: Bradley, Robert
Liu, Chaozong
Idriss, Hicham
Ammar-Khodja, Isabelle
Baidak, Alex
Ward, Steven
Issue Date: May-2011
Publisher: Robert Gordon University
Abstract: This thesis examines the surfaces of polyacrylonitrile (PAN) based high strength (HT) carbon fibres modified by electrochemical and ultra-violet ozone (UV/O3) treatment methods. The surface and bulk study was conducted by x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. In addition, immersion calorimetry in polar and non-polar liquids, as well as dilute resins, is used to investigate fibre surface energies while temperature programmed desorption (TPD) is used to investigate adsorption of linear alcohols (C1 to C4) on the fibres. One of the main aims of the work is to understand the reaction mechanisms that take place between the surface oxygen functionalities on treated carbon fibres and the resin molecules that are used in forming composites. UV/O3 treatments were shown to produce significant levels of oxygen on the fibre surface. Anodic treatments did not alter the surface morphology, while UV/O3 treatments were seen to increase surface areas six fold. Immersion calorimetry measurements showed similar trends to carbon black materials but, due to the small surface areas of the fibre (typically 1 m2/g), the rush-in effect and heat of ampoule breakage was found to overshadow the signal from the fibre. TPD measurements showed that alcohol adsorption was considerably enhanced by the presence of surface oxygen. In addition a relationship between the acidity scale of the alcohols in the gas phase and the extent of their dissociative adsorption at room temperature was established. Overall this work has shown UV/O3 to be a successful surface treatment method, superior to electrochemical treatments and TPD to be a promising method for investigating bonding.
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