Graphite graphitization temperature

Fig. 7. High-temperature neutron irradiation a-axis shrinkage behavior of pyrolytic graphite showing the effects of graphitization temperature on the magnitude of the dimensional changes [60].

Once the paper is cured, the carbonization and graphitization steps are performed under an inert environment. The exact temperatures for these two steps depend on the desired characteristics of the final products. In general, it is difficult to determine the best temperatures for these steps. In addition, the rate at which the sample is heated inside the furnace is an important parameter that determines the characteristics of the final product. For example, Mathur et al. [11,12] determined that a carbonization temperature of around 2,000°C (with a 900°C/hour heat rate) and a graphitization temperature of 2,500°C produced a CFP that performed the best in a PEMFC because it improved the hydrophobic properties of the material. 

During the graphitization process, the crystal size (both the Lc and La values) increases from about 5nm at 1200°C to the order of lOnm at 2000°C and to more than lOOnm at higher graphitization temperatures. 

On cooldown, the yarns do not shrink as much as the matrix and a gap is left between yarn and matrix consequently, the higher-density composites must creep more for the same graphitization temperature, thereby producing larger gaps at room temperature. 

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