Glasses play a critical role in current and developing technologies. Modern communication would be impossible without amorphous silicates used in optical fibers. Organic glasses are essential for organic light emiting diodes and other devices. Amorphous chalcogenides have revolutionized optical disc technogies for data recording media and are promissing materials for non-volatile electronic memory. Polymer glasses and composite materials play important role also in automotive and aviation industry. Glasses, and the glass-forming liquids from which they are usually prepared, still provides some fundamental questions that have not been answered yet.
The physical property that dominates much of the behavior of glass-forming liquid is shear viscosity. Its dramatical increase (more than 1012 Pa.s) results in the transition from low viscosity fluid to a solid glass, characterized by glass transition temperature Tg. In this temperature region the molecular rearrangements occur on a scale of minutes or hours. The viscous flow is essential for processing and shaping in glass industry. However, the understanding of this irreversible deformation process is still mostly phenomenological.
There are two possible pathways expressing ultimate fate of the supercooled glass-forming liquid. The first pathway is characterized by molecular ordering leading to the formation of nucleus, later followed by crystal growth. Despite of technological importance of this process there are still many open questions concerning the scenarios of viscosity role. The second pathway is a gradual transformation of a metastable liquid to non-crystalline glassy state, usually called vitrification. As the change of viscosity is involved in this glass-forming, a time-dependent non-linear change in volume, enthalpy (and other physical properties) takes place. This process, called structural relaxation, is quite complex and still not fully understood.
Our research attempts to provide a better understanding of these complex pathways. We combine experimental results from several experimental techniques and theoretical background to get more detailed picture and theoretical description of these phenomena taking place in various materials (chalcogenides, oxides, polymers, etc.). Funding is provided mainly by the University of Pardubice and the Czech Science Foundation. Undergraduate and graduate students are involved in all main activities of our research group:
· Crystallization (Complex crystallization / Crystal growth / Nucleation)
· Kinetics (in Thermal Analysis)
· Structural relaxation
· Viscosity in supercooled liquids