CRYSTALLIZATION KINETICS AND PHASE-TRANSFORMATION CHARACTERISTICS IN SEEDED MONOPHASIC CORDIERITE GEL

Abstract

Crystallization kinetics and phase transformation characteristics of mu- or alpha-cordierite seeded gels were compared with those of unseeded monophasic gels. The alpha-cordierite seeding modified the sequence of phase transformation and lowered the temperature of alpha-cordierite formation from amorphous gel by approximately 150-degrees-C. The mu-seeded transformation was characterized by 3-dimensional isotropic growth with essentially zero activation energy for the nucleation step. Combining the nucleation theory with the transition state theory, we have separately estimated the activation free energy of nucleation and that of growth step in the crystallization of amorphous cordierite gel. The estimated activation free energies showed that the crystallization of unseeded cordierite gel is mainly growth controlled.