Kinetics of non-isothermal crystallization process and activation energy for crystal growth in amorphous materials

Glass Transition Phenomena, Crystallization Kinetics and Enthalpy Released in Binary Se100-xInx (x = 2, 4 and 10) Semiconducting Glasses

“…It has been pointed out [8] that in the crystallization process three types of activation energies have to be considered, the activation energy of nucleation E n , the activation energy of growth E g , and the activation energy of the whole crystallization process E c . Further it has been shown by various studies [8,11,12,30] that the activation energy for growth may be taken equal to the activation energy of the whole crystallization provided it is evaluated using the thermal analysis of the sample. The Johnson-Mehl-Avrami (JMA) [32,33] equation has been developed basically to study the kinetics of phase transformations involving nucleation and growth process under isothermal conditions.…”

“…The Johnson-Mehl-Avrami (JMA) [32,33] equation has been developed basically to study the kinetics of phase transformations involving nucleation and growth process under isothermal conditions. However, extending the use of the JMA equation, Matusita et al [11] have suggested an equation which is applicable for non-isothermal crystallization and is given by ln Àln 1 À X Àn ln a À 1:052 mE c =RT const: ; 5…”

“…At this moment the size of the nuclei does not reach the critical size required to initiate the nucleation process and hence the glass is assumed to have no nuclei (of critical size). According to Matusita et al [11], when the glass is heated in the DSC furnace, the rate of crystal nucleation in glass reaches the maximum at a temperature somewhat higher than the glass transition temperature and then decreases rapidly with increasing temperature, while the rate of crystal growth reaches the maximum at a temperature much higher than the temperature at which the nucleation rate is highest. When the glass is heated at a constant rate, crystal nuclei are formed only at lower temperatures and crystals grow in size at higher temperatures without any increase in number.…”

“…In this context the glass transition temperature T g , the onset crystallization temperature T c as a function of heating rate and the dependence of T g on the coordination number with varying composition have been studied. The activation energy of both phases has been obtained using theoretical models [11,12] reported in literature. The demands of stability have been ensured through the calculation of the temperature difference T c ±T g and the enthalpy released during the crystallization process.…”

Influence of UV Radiation on the Physical-chemical and Mechanical Properties of Banana Fiber

“…The UV radiation is a potential energy source able to promote photochemical reactions in the molecular structures of natural fibers changing its mechanical properties, and simultaneously, acts as a clean method to modify surface of natural fibers. However, the study of photochemical reactions in organic materials is an area of intense scientific research [8][9][10][11] . Despite its relevance, the degradation mechanisms induced by photons in polymers or natural fibers, which trigger changes in their physical and chemical properties are not yet fully understood 12 .…”