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Mesoscopic Structure and Properties of Liquid Crystalline Mesophase Pitch and Its Transformation into Carbon Fiber
Author(s) -
Mochida Isao,
Yoon SeongHo,
Korai Yozo
Publication year - 2002
Publication title -
the chemical record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.61
H-Index - 78
eISSN - 1528-0691
pISSN - 1527-8999
DOI - 10.1002/tcr.10016
Subject(s) - mesophase , materials science , stacking , mesoscopic physics , composite material , spinning , carbon fibers , fiber , graphite , anisotropy , melt spinning , liquid crystal , nanotechnology , crystallography , chemistry , organic chemistry , optics , condensed matter physics , optoelectronics , physics , composite number
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 sp 2 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