CALCULATION OF THE THERMAL PROPERTIES OF AMORPHOUS AND CRYSTALLINE SUBSTANCES

An improved classical theory of the nucleation of crystals in a disordered medium with conservation of the spherical shape of the growing crystals is presented. The counteractions of the matrix of such a medium to the growth of crystals in it as well as the changes in this medium with change in its temperature and with time, calculated by a simple thermodynamic model of a two-phase system, are demonstrated. The coeffi cients of thermal expansion of a number of metals and the heat capacities of them at temperatures falling within a wide range were calculated. The temperature and time dependences of the volume fraction of the crystalline phase in a metal were constructed using the indicated thermodynamic model, and they were in good agreement with the experimental ones. It is shown that the changes in the volume of a metal, caused by its heating or cooling, are defi ned correctly by this model and that the indicated changes are determined by the dependences of the thermal volume expansion of the metal on its temperature and the volume fraction of the ordering phase in it. It was established that the thermodynamic model of a two-phase system can be used for the defi nition of the temperature dependence of the heat capacities of metals experiencing diff erent phase transitions
An improved classical theory of the nucleation of crystals in a disordered medium with conservation of the spherical shape of the growing crystals is presented. The counteractions of the matrix of such a medium to the growth of crystals in it as well as the changes in this medium with change in its temperature and with time, calculated by a simple thermodynamic model of a two-phase system, are demonstrated. The coeffi cients of thermal expansion of a number of metals and the heat capacities of them at temperatures falling within a wide range were calculated. The temperature and time dependences of the volume fraction of the crystalline phase in a metal were constructed using the indicated thermodynamic model, and they were in good agreement with the experimental ones. It is shown that the changes in the volume of a metal, caused by its heating or cooling, are defi ned correctly by this model and that the indicated changes are determined by the dependences of the thermal volume expansion of the metal on its temperature and the volume fraction of the ordering phase in it. It was established that the thermodynamic model of a two-phase system can be used for the defi nition of the temperature dependence of the heat capacities of metals experiencing diff erent phase transitions
Author:  S. V. Terekhov
Keywords:  amorphous alloys, crystallization, smeared phase transition, thermodynamic model, heat capacity
Page:  1631