Avrami Model
The Johnson-Mehl-Avrami equation (eq. 5) was used to model the
spectrophotometric data for non-isothermal nucleation kinetics
(Garcia-Andrade et al., 2020):
\(ln(1-F)={-zt}^{n}\) (5)
where n is the Avrami exponent, z is a constant associated
with the overall phase transition velocity, t is the time andF is the uncrystallized fraction over time. Integer values (1, 2,
3) of n represent the formation of rod-shaped crystals (1-D),
disk-shaped crystals (2-D) and spherical crystals (3-D), respectively. A
non-integer value indicates the formation of irregularly shaped
crystals. The methodology of Toro-Vázquez et al. (2000) was followed to
calculate the Avrami parameters from the exotherms obtained by DSC.F values were taken as the integration of the non-isothermal
crystallization curves. The n and z parameters were determined by
nonlinear estimation using the Rosenbrock and Quasi-Newton algorithm.