R. González-Palma

Theoretical study on the glass–crystal transformation and deduction of its kinetic parameters by DSC, using non-isothermal regime

Abstract A method has been developed for deriving the evolution equation with time of the volume fraction crystallized, for integrating the above-mentioned equation under non-isothermal conditions, and for deriving the kinetic parameters of the glass–crystal transformations in solid systems involving the formation and growth nuclei. By means of this method, and considering the assumptions of extended volume and random nucleation, a general expression of the fraction crystallized has been obtained as a function of the time. This equation has been integrated under continuous-heating regime and assuming an Arrhenian temperature dependence of the nucleation frequency and of the crystal growth rate, thus obtaining the volume fraction transformed as a function of temperature, in terms of the heating rate, and the related exponent with the dimensionality of the crystal growth. The kinetic parameters have been deduced, obtaining the maximum crystallization rate, bearing in mind the fact that, in the non-isothermal processes the reaction rate constant is a time function through its Arrhenian temperature dependence. Finally, the theoretical expressions of the kinetic parameters have been applied to the experimental data corresponding to a set of glassy alloys, quoted in the literature, thus obtaining mean values that agreed very satisfactorily with the published data. This fact shows the reliability of the theoretical procedure developed.