Estimation of activation energies for structural relaxation and viscous flow from DTA and DSC experiments

Physical Processes

“…3.21, z * is inversely proportional to the configurational entropy that increases with T so that both z * and the effective activation energy (i.e., z * Δμ) decrease with T. Note that even before the first applications [30,46] of isoconversional methods to the glass transition kinetics, the trend for the activation energy to decrease with increasing temperature was observed in other studies [47][48][49]. In them, the activation energy was determined from the shift in the value of T g with the heating rate in accord with the equation proposed by Moynihan et al: [42,43] (3. 22) where β can be the rate of heating or cooling.…”

“…Φ represents the heat flow value at a given temperature, T. Φ l and Φ g represent the extrapolated heat flow baselines for the liquid and glass at the same temperature T. These are the values to be substituted in Eq. 3.20 to determine α at this T is equal to the rate of the following heating [42,43]. A suitable temperature range of measurements is typically from T g + 40 to T g − 40.…”

A Calorimetric Investigation of Thermodynamic andMolecular Mobility Contributions to the Physical Stability of Two Pharmaceutical Glasses

“…Prior to heating, the sample was cooled from temperature well above T g to temperature greater than 408C below T g at the same rate as the subsequent heating rate. 26,27 RESULTS AND DISCUSSION Thermal Stability…”

Synthesis and Characterization of Nd3+‐Doped Indium‐sodium Tetraborate Glasses

“…If a kinetically impeded process such as crystallization or a chemical reaction that is accompanied by absorption or evolution of heat occurs within the sample, DSC and DTA can be used to characterize the kinetics of the process. 19 The glass sample (x＝5 mol%) was subjected to DTA in order to determine glass transition (T g ) and crystallization (T cr1, T cr2 ) temperatures. A typical DTA plot obtained for the present sample is depicted in Figure 4.…”