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

Abstract

The relationships between the density measured by butanol immersion (real density D_R) 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, L_c and L_a, on D_R were clearly different on the three cokes, particularly the dependence of c₀ on D_R 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 D_C calculated from c₀ and a₀ was compared with observed D_R, suggesting that the volume of “closed voids” in the particle, which was calculated as (D_C-D_R)/D_C, and its change during graphitization was characteristic for each coke.