Cooling rate dependency of fluctuations in the melt volume of amorphous materials

Abstract

It has been shown that the physical properties of any amorphous material in the glass transition region change in a similar manner. The cooling rate depen dence q = dT/dt of glass transition temperature T g can thus be described universally by the Bartenev-RitlandAs can be seen from the table, the ratio of the two vari ables in this formula has the same constant value for any glasslike material [2]:In this work, we used both relaxation theory [1-3] and the excited state model [4-6] to provide a possible explanation for the observed constancy. According to the excited state model, the liquid-glass transition occurs when the average thermal energy of the oscilla tion of atoms in a crystal lattice (3kT) becomes equal to or less than the enthalpy of the ultimate elastic deformation of interatomic bonds (ΔH e ): 3kT ≤ ΔH e .The ΔH e /kT g ratio remains ~3 at T = T g [5], con firming that the fraction of the fluctuation volume (f = ΔV e /V) formed by the displacement of structural units (an atom or group of atoms) from their equilibrium Abstract-Fluctuations in the melt volume of the amorphous materials as a function of cooling rate is estab lished. The observed dependency is similar to the one found for the glass transition temperature (the Bar tenev-Ritland equation). The constant ratio of the empirical parameters in the equation is explained in terms of the excited state model.