Texture formation in carbonaceous mesophase fibers

Abstract

Carbonaceous mesophases are discotic nematic liquid crystals that are spun into high performance carbon fibers using the melt spinning process. The spinning process produces a wide range of different fiber textures. Planar polar (PP) and planar radial (PR) textures are two ubiquitous ones. This paper presents theory and simulation of the texture formation process using the Landau-de Gennes mesoscopic theory for discotic liquid crystals. The computed PP and PR textures phase diagram, given in terms of temperature and fiber radius, is presented to establish the processing conditions and geometric factors that lead to the selection of these textures. Thin fibers adopt the PR texture, while thicker fibers and higher temperatures adopt the PP texture. The influence of elastic anisotropy to the formation of textures and structure is thoroughly characterized.

Nonisothermal Model for the Direct Isotropic/Smectic-A Liquid-Crystalline Transition

“…where n/m/l are the eigenvectors of Q, which characterize the average molecular orientational axes, and S/P are scalars which characterize the extent to which the molecules conform to the average orientational axes [47][48][49]. Uniaxial order is characterized by S and n, which correspond to the maximum eigenvalue (and its corresponding eigenvector) of Q,…”

Entropic Behavior of Binary Carbonaceous Mesophases

“…The type and extent of NLC applications [13] are mainly determined by their thermal properties. For instance, it is known that the final structure of the fibers based on the pure liquid crystalline materials is influenced by the temperature [14][15][16][17]. The results of our previous study [1] shows that the structure of the fibers based on the real CMs which are composed of DNLC species with different molecular weights and concentrations are also influenced by the thermal effect.…”

Rheological Theory and Simulation of Surfactant Nematic Liquid Crystals

“…In addition to singular defects, nonsingular defects arise in the form of lines and inversion walls (de Luca and Farhoudi and Rey 1993a -c ;Grecov and Rey, 2003a,b ;Hwang and Rey, 2006a Lhuillier and Rey, 2004a,b ;Rey, 2000aRey, -c , 2001aRey, ,b , 2007Rey, , 2009Rey, , 2010Soule et al, 2009 ;Stewart, 2004 ;Tsuji and Rey, 1988, 1997Yan and Rey, 2002 ;Zhou et al, 2006 ). Nonsingular defects are captured by the LE model since they do not involve changes in the order parameters.…”