Chemical impurities (principally sulfur) derived from petroleum-based
precursor materials can impact the graphitization process by volatiliz
ing during high temperature thermal treatment. In an attempt to elimin
ate the crystal damage caused by the evolution of sulfur-bearing gases
from petroleum-based fibers, the present research utilizes a chemical
ly pure precursor synthetically derived from naphthalene. Structural a
nd chemical changes were then monitored as a function of heat treatmen
t temperature with X-ray diffraction and spectroscopic techniques in a
n attempt to better understand how the graphitic crystal structure dev
elops in these materials. As is the case with fibers produced from alt
ernative precursors, gas evolution during the thermolysis region (i.e.
< 1000 degrees C) damaged the crystal structure of the synthetically-
derived fibers. Although this damage cannot be eliminated, optimizatio
n of all phases of fiber production can minimize the extent of crystal
damage incurred during thermal processing. An ideal thermal treatment
is also proposed which maximizes various physical properties by manip
ulating crystal structure. ''Optimization'' consisted of determining t
he relationships between structural properties and various physical pr
operties (namely electrical resistivity and tensile modulus) of AR-der
ived carbon fibers. Using these relationships, the crystal structure i
n these fibers was manipulated (i.e. optimized) by controlling the the
rmal treatment process. Variables such as heating rate, dwell time and
firing atmosphere were investigated. (C) 1997 Elsevier Science Ltd.