The stabilisation process in mesophase pitch based carbon materials

The primary aim of this work is to investigate the stabilisation process and how it impacts on mesophase products. The stabilisation step in the production of mesophase products has long been of great interest. This study will be broken down to asses the physical and chemical changes that occur during the stabilisation of mesophase products (in particular highly orientated mesophase pitch-based tapes); the transport mechanisms involved in the stabilisation process, how subsequent carbonisation of the mesophase pitch-based products are affected by the stabilisation conditions and how stabilisation affects the optical and mechanical properties of the mesophase pitch-based tapes. Highly oriented mesophase pitch-based (ARMPH) carbon tapes were oxidatively stabilised at 160°C, 240°C and 300°C for 5hrs and 25hrs. A weight gain as a result of the incorporation of oxygen was observed with increasing temperature and time. Improved structural ordering of the tapes was also noticed with increased stabilisation time and temperature. A clear correlation between the softening point and oxygen content of the mesophase pitch-based tapes was evident, as oxygen content increases so does the softening point of the mesophase pitch-based tapes influenced by the distribution of oxygen through out the tapes. Carbonisation of the stabilised material showed the bulk of the weight loss takes place between 400-700°C in the form of evolved CO, CO2 and hydrocarbons. Improved dimensional stability and morphology was also demonstrated in mesophase pitch-based tapes which were stabilised to greater degrees. Stabilisation conditions were also seen to play a key role in determining the final mechanical properties of the mesophase pitch-based tapes. Higher temperatures of stabilisation were seen to greatly improve the tensile strength of the tapes. The maximum values of stain to failure were recorded for tapes stabilised to 240°C for 25hrs. The mechanical reliability of the tapes was also seen to improve with increasing temperature of stabilisation.