Relationships between real density and XRD parameters during the graphitization of cokes

The relationships between the density measured by butanol immersion (real density DR) and the XRD parameters were examined during the graphitization of three kinds of coke; pitch cokes with mosaic and needle-like textures and a petroleum coke. The heat treatment was performed at 2100–3000 °C for 5–960 min. The dependences of XRD parameters, c0, Lc and La, on DR were clearly different on the three cokes, particularly the dependence of c0 on DR being approximated linear. The results suggest that these relationships depend strongly on the origin of the cokes, either coal-tar pitch or petroleum and whether they have a mosaic or needle-like texture. In order to consider these relationships, crystal density DC calculated from c0 and a0 was compared with observed DR, suggesting that the volume of “closed voids” in the particle, which was calculated as (Dc − DR)/Dc, and its change during graphitization was characteristic for each coke.