Kinetic Processes in Amorphous Materials Revealed by Thermal Analysis: Application to Glassy Selenium

Area of Science:

• Materials Science
• Physical Chemistry
• Condensed Matter Physics

Background:

• Viscous flow influences kinetic processes in supercooled liquids, impacting structural relaxation and crystallization.
• These kinetic processes are crucial for understanding the behavior of quenched glasses.

Purpose of the Study:

• To investigate the relationship between the activation energy of viscous flow and the activation energy of crystal growth and structural relaxation in glassy selenium.
• To elucidate the role of viscous flow in the kinetics of glass formation and behavior.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis.
• Thermomechanical analysis (TMA) to assess mechanical properties under temperature changes.
• Hot-stage infrared microscopy for direct observation of structural changes at elevated temperatures.

Main Results:

• The activation energy of structural relaxation in glassy selenium matches the viscous flow activation energy at the lowest glass transition temperatures observed.
• The temperature-dependent activation energy of crystal growth closely mirrors the viscous flow activation energy.
• Observed decoupling between viscosity and crystal growth rate suggests a departure from Stokes-Einstein behavior.

Conclusions:

• Viscous flow plays a critical role in the structural relaxation and crystallization kinetics of glassy selenium.
• The activation energies of viscous flow, structural relaxation, and crystal growth are interconnected, providing insights into glass transition and crystallization mechanisms.
• Deviations from Stokes-Einstein behavior are important for understanding the relationship between viscosity and crystal growth rates in this system.