Mesophase pitches which have different mesophase contents were prepare
d from a coal tar pitch and separated into mesophase and isotropic pha
se by high-temperature centrifugation. Properties of mesophase during
its nucleation, growth, and coalescence stages were investigated by me
asuring the solubility, density, C/H atomic ratio, and thermogravimetr
ic analysis. Mesophase pitch is easily separated into mesophase and is
otropic phase by high-temperature centrifugation. However, when the me
sophase content in pitch is above 82 vol%, the centrifugal separation
becomes difficult because of a very small density difference between t
he mesophase and isotropic phase. The mesophase content in pitch was i
ncreased by centrifugal acceleration at constant temperature. The C/H
atomic ratio of the mesophase separated under higher centrifugal accel
eration was also increased. QI was the main component of smaller mesop
hase spheres, and beta-resin of the isotropic matrix contributed to th
e growth of spheres. The density and C/H atomic ratio of mesophase wer
e nearly constant at 1.385 g/cm3 and 2.00, respectively, during heat t
reatment.