Applicability of Fraser-Suzuki function in kinetic analysis of complex crystallization processes

A modified peak-deconvolution procedure for complex crystallization processes was introduced. The method is based on the constrained curve-fitting technique using the Fraser-Suzuki (FS) function, where the FS asymmetry parameter a (3) correlates with the value of the Johnson-Mehl-Avrami (JMA) kinetic parameter m. The correlation was verified for an extensive number of theoretically simulated JMA curves; in addition, the dependencies of the a (3) parameter on other kinetic variables (E, A, q (+)) were quantified. The suggested deconvolution procedure was tested on two glassy systems with different overlay degree of the involved overlapping surface and bulk crystallization processes. In both cases, the kinetic analysis of deconvoluted data provided reasonable, consistent and accurate results. However, certain level of knowledge and experience was needed in order to correctly recognize and consequently account for all deviations from the theoretical behavior caused by thermal gradients or imperfections of the data acquisition process. As the input data for the fitting procedure can be in any form equivalent to the d alpha/dT temperature dependence, the method seems to be highly universal and may be applied to data obtained by various TA techniques.