Simulation of Carbonaceous Mesophases Micro-Textures
L.R.P. de Andrade Lima and A.D. Rey
McGill University, CA
Keywords: texture, modeling, carbon fibers, mesophase pitch
Carbonaceous mesophases are liquid crystalline precursor that can be spun into carbon fibers using the melt spinning process; the manufacture optimization requires a better understanding of the principles that control the carbon fiber structure development during the fiber formation. This work uses the continuum theory of liquid crystals to simulate the structure formation for pressure-driven flow of carbonaceous mesophases in the industrial process. This theory allows solution multiplicity and multistability that arise because the flow-alignment angle has an infinite degeneracy. The steady state stable solutions can be classified as either primary or secondary, where the first exist for all pressure drop and the second exist for pressure drop above a certain critical value. The results shown that higher order solutions exhibit a narrow alignment region in between core and rim regions over which the molecular orientation exhibits also the same orientation periodically, and the low order solutions exhibit alignment over a wide annular region and narrow core and rim regions. The results also show, that as the pressure drop increases the aligned annular region increases, and the rim region exhibits sharp gradients. The solution multiplicity helps to explain micro-textural phenomena, such a multiple concentric ring formation, found in the flow processing of carbon mesophases.
Nanotech 2004 Conference Technical Program Abstract