The characterisation of carbon fibre surfaces by electrochemical methods
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The possibility of surface characterisation of carbon fibres by electrochemical methods is investigated. A three electrode cell set-up is used and the carbon fibre electrode/solution electrolyte interface is studied. The interface is represented as an equivalent circuit of electrical components and the variation in the nature and value of these components is investigated for various high modulus fibres. Initial studies using non-sinusoidal techniques show that the simple equivalent circuit model, containing a solution resistance, a charge transfer resistance and a double layer capacitance, normally used for this type of cell is completely inadequate. It is not feasible to distinguish between fibres or even between different electrolyte solutions using these methods. However, it is shown that by applying an a.c. impedance technique coupled with equivalent circuit analysis developed by Boukamp it is possible to generate a more accurate representation of the fibre/solution interface. The new circuit contains additional elements such as an interfacial inductance and a constant phase diffusional element. By monitoring the d.c. polarisation potential dependence of these circuit components it is shown to be possible to distinguish between untreated and surface-treated fibres. However, it is not possible to distinguish between different batches of the same fibre. It is shown that galvanic oxidation of untreated fibres can be monitored by this method. The effects of time on oxidised fibres is also investigated.
Thesis, MSc Master of Science
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