Transient phase-induced nucleation

Area of Science:

• Materials Science
• Crystallography
• Physical Chemistry

Background:

• Crystallization from supercooled melts is crucial for materials processing.
• Understanding metastable phases is key to controlling final crystal structures.
• Hexadecane's crystallization provides a model system for studying phase transitions.

Purpose of the Study:

• To directly observe and characterize the transient metastable rotator phase in hexadecane.
• To investigate the role of this transient phase in determining the limit of supercooling.
• To elucidate the crystallization kinetics of n-alkanes and confirm the nature of the transient phase.

Main Methods:

• Time-resolved synchrotron X-ray scattering was employed for direct observation.
• Crystallization kinetics of a homologous series of n-alkanes were measured.
• Thermodynamic stability analysis was used to understand supercooling limits.

Main Results:

• A transient metastable rotator phase was directly observed during hexadecane crystallization.
• The limit of supercooling is governed by the thermodynamic stability of this transient phase.
• A crossover in crystallization kinetics from metastability to transient metastability was identified.

Conclusions:

• The transient metastable rotator phase plays a critical role in the crystallization of hexadecane.
• The observed crossover in metastability explains the crystallization kinetics of n-alkanes.
• Direct observation confirms the nature and significance of the transient phase in supercooling phenomena.