Non-isothermal Nucleation Kinetics
Non-isothermal nucleation kinetics of OGs were obtained on a Jenway 6705
spectrophotometer (OSA, UK), coupled to a water bath with Techian
temperature controller (OSA, UK). Kinetics were performed from OGs
melted at 80°C (isothermal 10 min) and then cooled to room temperature.
During absorbance kinetics, readings were taken every 10s (550 nm)
(Garcia-Andrade et al., 2020). Nucleation induction time
(tn), nucleation rate (J) and nucleation free energy
(ΔGn) were determined using the Fischer-Turnbull model
(Rogers & Marangoni, 2009), described below:
\(J=\frac{1}{t_{n}}\) (1)
The cooling rate (Ø) was also determined as a ratio of temperature
change over time (simulating the DSC cooling ramp):
\(O=\frac{\text{ΔT}}{\text{Δt}}\) (2)
The effective supercooling (δ), which incorporates a thermodynamic
component from an initial temperature (80°C) where the material is
completely melted, to the nucleation process (Ti-Tn) and
a kinetic component (Ø), was determined:
\(\delta=\frac{\text{ΔT}_{c}}{\sqrt{2O}}\) (3)
The determination of ΔGn was determined from the
kinetic parameters obtained above:
\(\text{ΔG}_{n}=\frac{\text{mk}\delta}{{(\Delta T)}^{2}}\) (4)
where m is the slope of the ratio of δ and the normalized
nucleation rate (J/Jmax) and k is the Boltzman constant.