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Cascading time evolution of dissipative structures leading to unique crystalline textures.

Hashimoto T, Murase H - IUCrJ (2015)

Bottom Line: The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields.The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures.Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

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Affiliation: Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan ; Quantum Beam Science Directorate, Japan Atomic Energy Agency , Tokai-mura, Ibaraki, 1319-1195, Japan ; Professor Emeritus, Kyoto University , Kyoto, 606-8501, Japan.

ABSTRACT
This article reports unique pattern formation processes and mechanisms via crystallization of materials under external flow fields as one of the general problems of open nonequilibrium phenomena in statistical physics. The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields. The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures. Moreover, this cascading pattern evolution obeys the Ginzburg-Landau law. It first evolves a series of large-length-scale amorphous precursors driven by liquid-liquid phase separation under a relatively low bulk stress and then small-length-scale structures driven by a large local stress concentrated on the heterogeneous amorphous precursors, eventually leading to the formation of unique crystalline textures which cannot be developed free from the external fields. Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

No MeSH data available.


Related in: MedlinePlus

Typical TEM images (b) and (c) of the specimen at P2, 20 mm downstream from the nozzle as illustrated in (a). Image (c) is a zoomed-in image of the dark part in the image (b). The data based on those given by Murase et al. (2011 ▶).
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fig9: Typical TEM images (b) and (c) of the specimen at P2, 20 mm downstream from the nozzle as illustrated in (a). Image (c) is a zoomed-in image of the dark part in the image (b). The data based on those given by Murase et al. (2011 ▶).

Mentions: The fibre running through the spinning line was quickly sampled out from the spinning line with a pair of frames having razor blades at its upper and lower edges to cut off and clamp the running fibres. The specimen fixed by the clamping frames was quickly cooled to room temperature with a nitrogen gas flow in order to lock in the structures evolved in the running fibre via solidification (crystallization). The solidified specimens were still gel-like with a concentration of solvent close to but less than 90 wt% at the positions from P2 to P4 and 40 wt% at P5: the positions P2 to P4 and P5 will be defined later in Figs. 9 ▶(a) and 13(b), respectively. In order to obtain specimens suitable for TEM observations without changing the structures developed in the solidified specimens, we used the following ‘fixation technique’. The solvent was stepwise replaced first from decalin to acetone and then from acetone to epoxy monomer, as detailed elsewhere (Murase et al., 2011 ▶). The epoxy monomer was then cured into epoxy resin at 60°C for ∼8 h. This fixation process was confirmed to hardly affect the structures in the solidified fibres.


Cascading time evolution of dissipative structures leading to unique crystalline textures.

Hashimoto T, Murase H - IUCrJ (2015)

Typical TEM images (b) and (c) of the specimen at P2, 20 mm downstream from the nozzle as illustrated in (a). Image (c) is a zoomed-in image of the dark part in the image (b). The data based on those given by Murase et al. (2011 ▶).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4285881&req=5

fig9: Typical TEM images (b) and (c) of the specimen at P2, 20 mm downstream from the nozzle as illustrated in (a). Image (c) is a zoomed-in image of the dark part in the image (b). The data based on those given by Murase et al. (2011 ▶).
Mentions: The fibre running through the spinning line was quickly sampled out from the spinning line with a pair of frames having razor blades at its upper and lower edges to cut off and clamp the running fibres. The specimen fixed by the clamping frames was quickly cooled to room temperature with a nitrogen gas flow in order to lock in the structures evolved in the running fibre via solidification (crystallization). The solidified specimens were still gel-like with a concentration of solvent close to but less than 90 wt% at the positions from P2 to P4 and 40 wt% at P5: the positions P2 to P4 and P5 will be defined later in Figs. 9 ▶(a) and 13(b), respectively. In order to obtain specimens suitable for TEM observations without changing the structures developed in the solidified specimens, we used the following ‘fixation technique’. The solvent was stepwise replaced first from decalin to acetone and then from acetone to epoxy monomer, as detailed elsewhere (Murase et al., 2011 ▶). The epoxy monomer was then cured into epoxy resin at 60°C for ∼8 h. This fixation process was confirmed to hardly affect the structures in the solidified fibres.

Bottom Line: The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields.The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures.Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan ; Quantum Beam Science Directorate, Japan Atomic Energy Agency , Tokai-mura, Ibaraki, 1319-1195, Japan ; Professor Emeritus, Kyoto University , Kyoto, 606-8501, Japan.

ABSTRACT
This article reports unique pattern formation processes and mechanisms via crystallization of materials under external flow fields as one of the general problems of open nonequilibrium phenomena in statistical physics. The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields. The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures. Moreover, this cascading pattern evolution obeys the Ginzburg-Landau law. It first evolves a series of large-length-scale amorphous precursors driven by liquid-liquid phase separation under a relatively low bulk stress and then small-length-scale structures driven by a large local stress concentrated on the heterogeneous amorphous precursors, eventually leading to the formation of unique crystalline textures which cannot be developed free from the external fields. Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress.

No MeSH data available.


Related in: MedlinePlus