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Mesoscopic Structure (mesoscopic + structure)

Distribution by Scientific Domains
Polymers and Materials Science33%

Selected Abstracts

Mesoscopic Structure and Properties of Liquid Crystalline Mesophase Pitch and Its Transformation into Carbon Fiber

THE CHEMICAL RECORD, Issue 2 2002
Isao Mochida
Abstract The history and present state of the art in the chemistry of mesophase pitch, which is an important precursor for carbon fiber and other high-performance industrial carbons, are reviewed relative to their structural properties. The structural concepts in both microscopic and macroscopic views are summarized in terms of the sp2 carbon hexagonal plane as a basic unit common to graphitic materials, its planar stacking in clusters, and cluster assembly into microdomains and domains, the latter of which reflect the isochromatic unit of optical anisotropy. Such a series of structural units is described in a semiquantitative manner corresponding to the same units of graphitic materials, although the size and stacking height of the hexagonal planes (graphitic sheets) are very different. Mesophase pitch is a liquid crystal material whose basic structural concepts are maintained in the temperature range of 250 to 350,°C. The melt flow and thermal properties are related to its micro- and mesoscopic structure. The structure of mesophase-pitch,based carbon fiber of high tensile strength, modulus, and thermal conductivity has been formed through spinning, and has inherited the same structural concepts of mesophase pitch. Stabilization settles the structure in successive heat treatments up to 3000,°C. Carbonization and graphitization enable growth of the hexagonal planes and their stacking into units of graphite. Such growth is governed and controlled by the alignment of micro- and mesoscopic structures in the mesophase pitch, which define the derived carbon materials as nanostructural materials. Their properties are controlled by the nanoscopic units that are expected to behave as nanomaterials when appropriately isolated or handled. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2:81,101, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10016 [source]

Book Review: Nanocrystals Forming Mesoscopic Structures.

ADVANCED MATERIALS, Issue 14 2006
By Marie-Paule Pileni (Ed.).
No abstract is available for this article. [source]

"Sponge-like" structures in polymer blends: visualization, physico-mathematical analysis, and universality

MACROMOLECULAR SYMPOSIA, Issue 1 2002
Takeji Hashimoto
Mesoscopic structures formed during an ordering process in thermodynamically unstable, isometric, binary molecular mixtures were explored by time-resolved scattering (TRS) and laser scanning confocal microscopy (LSCM). Three-dimensional (3D) bicontinuous structures, which were constructed for the first time by time-resolved LSCM, were found to have a "sponge-like" structure composed of two phases. The structure factor obtained by 3D Fourier transformation of the sponge was found to be identical to that obtained by TRS, confirming that the sponge truly reflects the structural entities evolving in the system. Furthermore, the sponge was shown for the first time to be theoretically predictable by using 3D computer simulations based on the time-dependent Ginzburg-Landau theory. The sponge was subjected to differential geometrical analysis: its Gaussian curvature K, mean curvature H, and their distributions were successfully determined for the first time. The result revealed that the sponge has hyperbolic interfaces with area-averaged curvatures satisfying < 0 and , 0 and that its interface has some deviations from a minimal surface. The sponge was found to be strikingly similar to that occurring in oil/water/surfactant systems at the hydrophile-lipophile-balance, though their characteristic length scales are diversely different (, vs nm), implying universality of the sponge. [source]

Shallow and deep excited states of mesoscopic structure in AgI,,Al2O3 composites

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2003
Shosuke Mochizuki
Abstract The photoluminescence (PL) and PL excitation (PLE) spectra of superionic conducting AgI,,Al2O3 composites have been measured at different temperatures between 7 K and room temperature. The X-ray diffraction patterns of these composites have also been measured at room temperature. The PL intensity peak observed at 426 nm is closely connected with radiative decay of free excitons in AgI, while other emission bands are connected with shallow excited states in AgI and deep excited states at the AgI/,Al2O3 interface. With increasing excitation light intensity, the PL efficiencies of several emission bands become saturated, except for the free exciton band. These results may give important information about the origins of the high ionic motion in these composites. [source]

Mesoscopic Structure and Properties of Liquid Crystalline Mesophase Pitch and Its Transformation into Carbon Fiber

THE CHEMICAL RECORD, Issue 2 2002
Isao Mochida
Abstract The history and present state of the art in the chemistry of mesophase pitch, which is an important precursor for carbon fiber and other high-performance industrial carbons, are reviewed relative to their structural properties. The structural concepts in both microscopic and macroscopic views are summarized in terms of the sp2 carbon hexagonal plane as a basic unit common to graphitic materials, its planar stacking in clusters, and cluster assembly into microdomains and domains, the latter of which reflect the isochromatic unit of optical anisotropy. Such a series of structural units is described in a semiquantitative manner corresponding to the same units of graphitic materials, although the size and stacking height of the hexagonal planes (graphitic sheets) are very different. Mesophase pitch is a liquid crystal material whose basic structural concepts are maintained in the temperature range of 250 to 350,°C. The melt flow and thermal properties are related to its micro- and mesoscopic structure. The structure of mesophase-pitch,based carbon fiber of high tensile strength, modulus, and thermal conductivity has been formed through spinning, and has inherited the same structural concepts of mesophase pitch. Stabilization settles the structure in successive heat treatments up to 3000,°C. Carbonization and graphitization enable growth of the hexagonal planes and their stacking into units of graphite. Such growth is governed and controlled by the alignment of micro- and mesoscopic structures in the mesophase pitch, which define the derived carbon materials as nanostructural materials. Their properties are controlled by the nanoscopic units that are expected to behave as nanomaterials when appropriately isolated or handled. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2:81,101, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10016 [source]