Glass-liquid transition

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Glass-liquid transition: The glass-liquid transition is a pseudo second order phase transition in which a solid amorphous material (glass) transforms, on heating, into a supercooled melt^[1]. The glass-liquid transition is characterised by the glass transition temperature, T_g. Below T_g amorphous materials are in glassy state and above T_g they are liquid. Most of joining bonds in amorphous materials are intact in the glassy state (Tg). The viscosity of amorphous materials is characterised in the glassy state by a high activation energy. Thermal fluctuations break joining bonds: the higher temperature the higher concentration of broken bonds (termed configurons). At temperatures approaching T_g configurons begin to form large clusters which become macroscopic large above the T_g. Broken bonds facilitate the flow and the viscosity of amorphous materials is characterised in the liquid state by a low activation energy.   The bond system of an amorphous material changes its Hausdorff-Besikovitch dimensionality from Euclidian 3 below T_g (where the amorphous material is solid), to fractal 2.55±0.05 above T_g, where the amorphous material is liquid^[2].

References

1. ^ The IUPAC Compendium of Chemical Terminology, 66, 583 (1997)
2. ^ M.I. Ojovan, W.E. Lee. Topologically disordered systems at the glass transition. J. Phys.: Condensed Matter, 18, 11507-11520 (2006); http://eprints.whiterose.ac.uk/1958/