Journal of physics. Condensed matter : an Institute of Physics journal, Jan 4, 2018
Key to resolving the scientific challenge of the glass transition is to understand the origin of ... more Key to resolving the scientific challenge of the glass transition is to understand the origin of the massive increase in viscosity of liquids cooled below their melting temperature (avoiding crystallisation). A number of competing and often mutually exclusive theoretical approaches have been advanced to describe this phenomenon. Some posit a bona fide thermodynamic phase to an ``ideal glass'', an amorphous state with exceptionally low entropy. Other approaches are built around the concept of the glass transition as a primarily dynamic phenomenon. These fundamentally different interpretations give equally good descriptions of the data available, so it is hard to determine which -- if any -- is correct. Recently however this situation has begun to change. A consensus has emerged that one powerful means to resolve this longstanding question is to approach the putative thermodynamic transition sufficiently closely, and a number of techniques have emerged to meet this challenge. ...
We have obtained some universal thermodynamic properties on glass transitions of molecular liquid... more We have obtained some universal thermodynamic properties on glass transitions of molecular liquids. The heat capacity Cp of glassy propene, which was vitrified by using a vapor-deposition technique, was measured with a newly developed adiabatic calorimeter. Propene has the lowest glass transition temperature (Tg=56  K), the largest Cp jump at Tg (Clqp/Cglp∼2.5), and the lowest residual entropy (Sres∼Rln2) compared with glass-forming molecules measured before. We have analyzed the present data with other hydrocarbon molecules vitrified by liquid quenching and obtained the following results: (1) The excess heat capacities are scaled well by using a Kauzmann temperature TK, (2) The size of the cooperative rearrangement region (CRR) frozen at Tg increases with decreasing the temperature difference between Tg and TK (Kauzmann temperature), and (3) The simpler the molecule is, the larger the frozen CRR becomes. These are all supporting the validity of the Adam-Gibbs theory.
Surface instabilities in vertically vibrated suspensions of various powders dispersed in silicone... more Surface instabilities in vertically vibrated suspensions of various powders dispersed in silicone oil are investigated in quasi-two-dimensional (2D) and quasi-one-dimensional (1D) systems. As vibration acceleration exceeded a critical value, the flat surface became unstable against a finite-amplitude perturbation. We found an expanding hole or viscous fingerlike pattern in the quasi-2D system and segregation between dried and wet areas in the quasi-1D system. We show that these instabilities are accompanied by convectionlike flow at their rim and in the quasi-1D system, the height of the convectionlike flow can be scaled by acceleration, vibration frequency, diameter of the dispersed powder, mean density of the suspension, and viscosity of silicone oil. We propose a simple model that accounts for the scaling and concentric motion of the convectionlike flow.
We report observations of stable, localized, line-like structures in the spatially periodic patte... more We report observations of stable, localized, line-like structures in the spatially periodic pattern formed by nematic electroconvection, along which the phase of the pattern jumps by $\pi$. With increasing electric voltage, these lines form a grid-like structure that goes over into a structure indistinguishable from the well known grid pattern. We present theoretical arguments that suggest that the twisted cell geometry we are using is indirectly stabilizing the phase jump lines, and that the PJL lattice is caused by an interaction of phase jump lines and a zig-zag instability of the surrounding pattern.
Journal of physics. Condensed matter : an Institute of Physics journal, Jan 4, 2018
Key to resolving the scientific challenge of the glass transition is to understand the origin of ... more Key to resolving the scientific challenge of the glass transition is to understand the origin of the massive increase in viscosity of liquids cooled below their melting temperature (avoiding crystallisation). A number of competing and often mutually exclusive theoretical approaches have been advanced to describe this phenomenon. Some posit a bona fide thermodynamic phase to an ``ideal glass'', an amorphous state with exceptionally low entropy. Other approaches are built around the concept of the glass transition as a primarily dynamic phenomenon. These fundamentally different interpretations give equally good descriptions of the data available, so it is hard to determine which -- if any -- is correct. Recently however this situation has begun to change. A consensus has emerged that one powerful means to resolve this longstanding question is to approach the putative thermodynamic transition sufficiently closely, and a number of techniques have emerged to meet this challenge. ...
We have obtained some universal thermodynamic properties on glass transitions of molecular liquid... more We have obtained some universal thermodynamic properties on glass transitions of molecular liquids. The heat capacity Cp of glassy propene, which was vitrified by using a vapor-deposition technique, was measured with a newly developed adiabatic calorimeter. Propene has the lowest glass transition temperature (Tg=56  K), the largest Cp jump at Tg (Clqp/Cglp∼2.5), and the lowest residual entropy (Sres∼Rln2) compared with glass-forming molecules measured before. We have analyzed the present data with other hydrocarbon molecules vitrified by liquid quenching and obtained the following results: (1) The excess heat capacities are scaled well by using a Kauzmann temperature TK, (2) The size of the cooperative rearrangement region (CRR) frozen at Tg increases with decreasing the temperature difference between Tg and TK (Kauzmann temperature), and (3) The simpler the molecule is, the larger the frozen CRR becomes. These are all supporting the validity of the Adam-Gibbs theory.
Surface instabilities in vertically vibrated suspensions of various powders dispersed in silicone... more Surface instabilities in vertically vibrated suspensions of various powders dispersed in silicone oil are investigated in quasi-two-dimensional (2D) and quasi-one-dimensional (1D) systems. As vibration acceleration exceeded a critical value, the flat surface became unstable against a finite-amplitude perturbation. We found an expanding hole or viscous fingerlike pattern in the quasi-2D system and segregation between dried and wet areas in the quasi-1D system. We show that these instabilities are accompanied by convectionlike flow at their rim and in the quasi-1D system, the height of the convectionlike flow can be scaled by acceleration, vibration frequency, diameter of the dispersed powder, mean density of the suspension, and viscosity of silicone oil. We propose a simple model that accounts for the scaling and concentric motion of the convectionlike flow.
We report observations of stable, localized, line-like structures in the spatially periodic patte... more We report observations of stable, localized, line-like structures in the spatially periodic pattern formed by nematic electroconvection, along which the phase of the pattern jumps by $\pi$. With increasing electric voltage, these lines form a grid-like structure that goes over into a structure indistinguishable from the well known grid pattern. We present theoretical arguments that suggest that the twisted cell geometry we are using is indirectly stabilizing the phase jump lines, and that the PJL lattice is caused by an interaction of phase jump lines and a zig-zag instability of the surrounding pattern.
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