A ~ianthrene-anthracene mixture has been used to study the influence of Fe@, addition in suppressing the volume expansion of carbons due to suifur release on heat treatment. For undoped carbons, the particle density began to decrease above about 1200°C and continued to 2500°C. There was an accompanying sharp reduction in sulfur content between 1400-1600°C. With Fe,@ addition, the sulfur content was higher over the whole temperature range studied. Between 1200-16M)"C the carbon density increased slightly, while from 1600-2500°C the density continuously decreased. Below 1600°C iron sulfide was detected in the cooled reaction mixture, consistent with the presence of an iron-s&fur liquid phase during heat treatment. The liquid phase appears to influence density changes through modifying the mechanisms for sulfur release. Although FeS was no longer evident at higher temperatures. the presence of iron compounds appeared to have an influence in reducing expansion.
The addition of Fez03 did not affect crystal growth and development of structural order during graphitization. Density decreases for doped and undoped carbons are attributed to disruption of crystallite alignment. Porosity measurements showed that the increase in pore volume is due to the formation of pores smaller than 200 nm diameter.