Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 5, pp. 760−764.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.A. Tyumentsev, A.G. Fazlitdinova, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 5, pp. 813−817.
AND POLYMERIC MATERIALS
X-ray Diffraction Analysis of the Fine Structure
of Carbon Fiber
V. A. Tyumentsev and A. G. Fazlitdinova
Chelyabinsk State University, Chelyabinsk, Russia
Received December 18, 2012
Abstract—X-ray diffraction analysis showed that the material of carbon ﬁ bers prepared from polyacrylonitrile is
heterogeneous. Its component composition is determined by the ﬁ ber preparation conditions and depends on the
angle at which the coherent scattering domains are oriented relative to the thread axis. The size of coherent scatter-
ing domains increases in going to components corresponding to lower d
values and depends on the orientation
angle φ relative to the thread axis.
Physicomechanical properties of carbon ﬁ bers are
determined by their structure, including the size of coher-
ent scattering domains (CSDs), and texture formed in the
course of high-temperature thermomechanical treatment.
The carbon ﬁ ber material undergoes graphitization dif-
ﬁ cultly. Therefore, when preparing high-modulus ﬁ bers,
thermomechanical treatment to form CSDs of optimal size
should be performed at high (~3000°С) temperatures. To
activate the mass transfer at lower temperatures, recrystal-
lization of the ﬁ brous carbon material can be performed
with the addition of boron. X-ray diffraction analysis is
widely used for determining the mean CSD size and tex-
ture of the material and for ﬁ nding relationship between
the structure and properties of the ﬁ ber. However, the
002 peak observed in the diffraction patterns of carbon
ﬁ bers is essentially asymmetric , which may be due
to simultaneous presence of components that appreciably
differ in the CSD size and in the interplanar spacing.
Therefore, the CSD size and interplanar spacing calcu-
lated from the integral width and position of the center
of gravity of such peaks do not reﬂ ect the real structure
of the material. Analysis of the asymmetric proﬁ les of
diffraction peaks can allow estimation of the component
composition of the carbon material and determination of
clearer relationship between the preparation conditions
and ﬁ ne structure of ﬁ bers.
Here we analyze the possibilities and results of ap-
plication of X-ray diffraction analysis to studying the
ﬁ ne structure of carbon ﬁ bers prepared under different
conditions of heat treatment.
We performed comparative studies of the ﬁ ne struc-
ture of carbon ﬁ ber obtained from polyacrylonitrile and
subjected to two-step high-temperature thermomechani-
cal treatment at 2300°С in a nitrogen atmosphere and
then at Т ~3000°С in an argon atmosphere, and also of
carbon ﬁ bers prepared in the presence of boron additive
at 2500, 2600, and 2650°С. The ﬁ ber bundle consists of
7200 ﬁ laments. The copolymer composition is 95% poly-
acrylonitrile + 5% methyl acrylate. Boron was introduced
into the carbon material in the course of high-temperature
treatment in an argon atmosphere of a thermostabilized
bundle after its preliminary impregnation with an aqueous
solution of boric acid and sodium tetraborate hydrate .
Structural studies of carbon ﬁ bers were performed
with a D8 ADVANCE X-ray diffractometer (ﬁ ltered CuK