Lecturer

Dr. Apiwat Wisitsorasak

♠เบอร์โทรศัพท์ (+66)0982524313

E-mail - apiwat.wis@mail.kmutt.ac.th

 

Towards a Unifying Concept of the Structural Glasses

 

The understanding and the complete description of the glass transition are impeded by the complexity of nature of the glass. Parts of this complexity come from the emergence of long-lived inherent structures of a liquid at a temperature below which the activated reconfiguration events play a dominant role. In our research group we ultimately seek understanding of the underlying physics of the glass transition and its practical applications of the developed theories. 

Metallic glasses are alloys that have a glass-like disordered structure rather and the polycrystalline structures of familiar metals. They can be both brittle and ductile and can be made into complex shapes, like the heads of golf clubs. However all glasses are not meant to deform and they will break catastrophically. Over time, when a metallic glass is put under stress, its atoms will shift, slide and ultimately form bands that leave the material more prone to breaking.

Outwardly, glasses may seem solid, but the random array of molecules inside is always moving. It has been known for decades that when stressed, glasses will form shear bands, lines that localize the strain. Arising of these bands prevents them to be used as structural materials. 

The key to understanding this problem is the interplay between the activated events that generate mobility and the transport of mobility in which they are also subjected under stress and strain fields.

 Our developed theory suggests that activating events play important role in the dynamics of the shear bands. Such activated events happen naturally as a supercooled liquid flows and become rare when the glass settles into its shape but ramp up when the glass is stressed. The event trigger the cooperative movement of adjacent molecules and eventually result in shear bands. The bands also mark regions of high mobility and where local crystallization can occur and ultimately lead to structural failure. This opens up the ability to do realistic calculations on the strength of glasses, especially metallic glasses. One could add the features of crystallization and fractures to the model as well, which would be of interest to materials scientists working on practical applications.

Besides the mechanical properties of the glasses, we also explore fluctuating mobility generation and transport in glasses to understand the dynamics of the glassy state within the framework of the RFOT theory of glass. Fluctuating spatiotemporal structures in aging and rejuvenating glasses lead to dynamical heterogeneity in glasses. This can lead us to illustrate how the heterogeneity in glasses gives rises of a non-Gaussian distribution of activation free energies, the stretching exponent, and the growth of characteristic lengths Moreover the dynamical heterogeneity can lead to a growth front of mobility in rejuvenating glasses that emanates from the surface where stable glasses are heated. 

References

1. A. Wisitsorasak, P. G. Wolynes, “Dynamical Theory of Shear Bands in Structural Glasses,” Proceedings of National Academy of Science, vol. 114, no. 6, pp. 1287 - 1292, 2017.
2. A. Wisitsorasak, P. G. Wolynes, “Dynamical Heterogeneity of the Glassy State,” The Journal of Physical Chemistry B, vol. 118, pp. 7835-7847, 2014. 

3. A. Wisitsorasak, P. G. Wolynes, “On the strength of glasses,” Proceedings of the National Academy of Sciences, vol. 109, no. 40, pp. 16068 - 16072, 2012.

No.SubjectYearOwner
1- Apiwat Wisitsorasak, P. G. Wolynes, 2014, Dynamical Heterogeneity of the Glassy State, The Journal of Physical Chemistry B, vol. 118, pp. 7835-7847.2014Apiwat Wisitsorasak
2- Apiwat Wisitsorasak, P. G. Wolynes, 2013, Fluctuating mobility generation and transport in glasses, Physical Review E, vol. 88, no. 2, pp. 022308.2013Apiwat Wisitsorasak
3- Apiwat Wisitsorasak, P. G. Wolynes, 2012, On the strength of glasses, Proceedings of the National Academy of Sciences, vol. 109, no. 40, pp. 16068 - 16072.2012Apiwat Wisitsorasak

EducationEducationInstituteYear
DoctoralPhD (Physics)Rice University (USA)2014
MasterMSc (Physics) University of California, San Diego (USA)2011
BachelorBSc (Physics) Mahidol University (Thailand)2009