fitted with a 12-hole, 75 lm U spinneret (AJA Inc., Greenville, SC). This
Ace-SKL/acetone solution was successfully dry-spun into lignin
fibers; the smallest average fiber diameter achieved was
30 ± 1 lm. SEM micrographs of the as-spun fibers, displayed
in Fig. 2a (left), showed that the fibers were slightly non-circular
with surface crenulations resulting from evaporation of
acetone. Subsequently, Ace-SKL fibers were thermo-oxidatively
stabilized using a temperature ramp of 0.2 C/min from
ambient to a maximum temperature of 220 C under tension,
which led to an extension of up to 800%. The stabilized lignin
fiber diameter reduced to about 12 ± 1 lm. Carbonization was
also performed under tension using a heating rate of 4.5 C/
min up to 1000 C (HP50 furnace, Thermal Technology LLC).
An extension of up to 25% could be achieved during carbonization
with adequate tension. The carbon fiber size ranged
between 6 and 8 lm, as displayed in Fig. 2b (right). Carbon fi-
bers also preserved the non-circular cross section observed
for precursor fibers.