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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.


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Steady-state scattering functions as a function of  over a wide range of q [wavenumber of Fourier modes of the CF or magnitude of the scattering vector defined as q = (4π/λ) sin (θ/2) with λ and θ being the wavelength of the incident beam and scattering angle θ in the medium]. The small-angle neutron scattering (SANS) data were taken with the D11 spectrometer at ILL, Grenoble, France, with a set of sample-to-detector distances of 35.7, 10.0 and 2.5 m. The sample used was deuterated UHMWaPS having Mw = 2.0 × 106 in DOP. C = 8.0 wt%, C/C* = 6.4 and T = 22°C much higher than the cloud point (2°C). Here qx and qz are magnitude of the scattering vector (q) parallel to the x axis and z axis, respectively. The data were reproduced from Saito et al. (2002 ▶).
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fig5: Steady-state scattering functions as a function of over a wide range of q [wavenumber of Fourier modes of the CF or magnitude of the scattering vector defined as q = (4π/λ) sin (θ/2) with λ and θ being the wavelength of the incident beam and scattering angle θ in the medium]. The small-angle neutron scattering (SANS) data were taken with the D11 spectrometer at ILL, Grenoble, France, with a set of sample-to-detector distances of 35.7, 10.0 and 2.5 m. The sample used was deuterated UHMWaPS having Mw = 2.0 × 106 in DOP. C = 8.0 wt%, C/C* = 6.4 and T = 22°C much higher than the cloud point (2°C). Here qx and qz are magnitude of the scattering vector (q) parallel to the x axis and z axis, respectively. The data were reproduced from Saito et al. (2002 ▶).

Mentions: What about the -dependent dissipative structures developed over a wide length scale ranging from nm to µm under the steady shear flow? The fundamental question raised above can be answered in part by Fig. 5 ▶ which presents the shear-induced steady-state scattering functions I(qx, 0) and I(0, qz), proportional to structure factors S(qx, 0) and S(0, qz), parallel (Fig. 5 ▶a) and perpendicular (Fig. 5 ▶b), respectively, to the FD as a function of (Saito et al., 2002 ▶). Note that the sample solution used here is slightly different from Solution 2 for the sake of convenience of SANS measurements. However, general behaviours to be described below are universally applicable to Solution 2 and even to Solution 1. At the low shear rate = 0.1 s−1 (Fig. 5 ▶a) or 0.1, 0.2 and 0.4 s−1 (Fig. 5 ▶b), the scattering functions were identical to that for the single-phase solution at rest ( = 0 s−1) and are predicted by the Ornstein–Zernike equationfor thermal CFs in the solution at rest, as shown by the dotted lines which illustrate the crossover in the qK dependence of the scattered intensity from to with increasing qK across qKc (K = x or z). ξT is the thermal correlation length. Thus, we conclude that these shear rates are too small, satisfying the condition < Γdis, so that the solution remains homogeneous under the flow, as discussed earlier in this section.


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

Hashimoto T, Murase H - IUCrJ (2015)

Steady-state scattering functions as a function of  over a wide range of q [wavenumber of Fourier modes of the CF or magnitude of the scattering vector defined as q = (4π/λ) sin (θ/2) with λ and θ being the wavelength of the incident beam and scattering angle θ in the medium]. The small-angle neutron scattering (SANS) data were taken with the D11 spectrometer at ILL, Grenoble, France, with a set of sample-to-detector distances of 35.7, 10.0 and 2.5 m. The sample used was deuterated UHMWaPS having Mw = 2.0 × 106 in DOP. C = 8.0 wt%, C/C* = 6.4 and T = 22°C much higher than the cloud point (2°C). Here qx and qz are magnitude of the scattering vector (q) parallel to the x axis and z axis, respectively. The data were reproduced from Saito et al. (2002 ▶).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig5: Steady-state scattering functions as a function of over a wide range of q [wavenumber of Fourier modes of the CF or magnitude of the scattering vector defined as q = (4π/λ) sin (θ/2) with λ and θ being the wavelength of the incident beam and scattering angle θ in the medium]. The small-angle neutron scattering (SANS) data were taken with the D11 spectrometer at ILL, Grenoble, France, with a set of sample-to-detector distances of 35.7, 10.0 and 2.5 m. The sample used was deuterated UHMWaPS having Mw = 2.0 × 106 in DOP. C = 8.0 wt%, C/C* = 6.4 and T = 22°C much higher than the cloud point (2°C). Here qx and qz are magnitude of the scattering vector (q) parallel to the x axis and z axis, respectively. The data were reproduced from Saito et al. (2002 ▶).
Mentions: What about the -dependent dissipative structures developed over a wide length scale ranging from nm to µm under the steady shear flow? The fundamental question raised above can be answered in part by Fig. 5 ▶ which presents the shear-induced steady-state scattering functions I(qx, 0) and I(0, qz), proportional to structure factors S(qx, 0) and S(0, qz), parallel (Fig. 5 ▶a) and perpendicular (Fig. 5 ▶b), respectively, to the FD as a function of (Saito et al., 2002 ▶). Note that the sample solution used here is slightly different from Solution 2 for the sake of convenience of SANS measurements. However, general behaviours to be described below are universally applicable to Solution 2 and even to Solution 1. At the low shear rate = 0.1 s−1 (Fig. 5 ▶a) or 0.1, 0.2 and 0.4 s−1 (Fig. 5 ▶b), the scattering functions were identical to that for the single-phase solution at rest ( = 0 s−1) and are predicted by the Ornstein–Zernike equationfor thermal CFs in the solution at rest, as shown by the dotted lines which illustrate the crossover in the qK dependence of the scattered intensity from to with increasing qK across qKc (K = x or z). ξT is the thermal correlation length. Thus, we conclude that these shear rates are too small, satisfying the condition < Γdis, so that the solution remains homogeneous under the flow, as discussed earlier in this section.

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