Materials Sciences and Applicatio n, 2011, 2, 834-838
doi:10.4236/msa.2011.27113 Published Online July 2011 (http://www.SciRP.org/journal/msa)
New Insight into the Graphene Based Films
Prepared from Carbon Fibers
Yanxiang Wang*, Wenxin Fan, Guoli Wang, Minxia Ji
Carbon Fiber Engineering Research Center of Shandong Province, College of Materials Science and Engineering, Shandong Univer-
sity, Jinan, China.
Received October 13th, 2010; revised January 10th, 2011; accepted May 21st, 2011.
ABSTRACT
In this work, ultrathin sections from longitudinal polyacrylonitrile (PAN) based T700 and T300 carbon fibers were
prepared by ultramicrotomy, a promising graphene based thin films were developed in one step at ambient temperature.
It is investigated that the network-graphene planes composed with carbon atoms are partly straight and partly twisted
in the thin films p repared from T700 carbon fibers, the distance between the carbon atoms of network-graphene plane
decreases, the order design of graphene in the films prepared from T700 carbon fibers is denser and its arrangement
shows a preferred orientation along the drawing direction, its consistency of the neighboring graphene based planes is
better, moreover, the relative content of the forming SP2-hybridized orbit of carbon atoms in the films prepared from
T700 carbon fibers is higher, in the other words, the fa ct of the graphene based film prepared from carb on fibers with-
out having the characteristic of skin-core structu re has been verified.
Keywords: Carbon Ma terials, Microstructure, Graphene, Thin Films
1. Introduction
In recent years, carbon materials have gained an increas-
ing attraction in more and more fields owing to its exten-
sive application ranges and extreme-potential perspec-
tives, which are rapidly becoming the global research hot
spot [1-3]. The preparation methods of graphene based
carbon materials mainly included mechanical exfoliating
[4-6], oxidation reduction process of graphite [7-9], solu-
tion method [10-13], and chemical method [14-19]. But
the yield of obtained graphene based on the mechanical
exfoliating method was lower. Although large scale uni-
form graphene based films could be synthesized by the
oxidation reduction process of graphite, the electronic
structure and crystalline integrity of graphene were heav-
ily damaged by the strong oxidizer. The graphene based
thin-film semiconductor with the large area could be
produced by the chemical method, but its application was
limited by the immature technology. As we know, the
carbon atoms of graphene are bonded by the covalent
bond [20]. During research of polyacrylonitrile (PAN)
based carbon fibers, some valuable research achievement
have been obtained [21,22]: the high strength of carbon
fibers are based on the preferred orientation of highly
extended crystalline structure along fiber axis and high
bond energy among the interfacial layers. We also veri-
fied the Ribbon model put forward by Perret [23] and the
two-dimensional model proposed by Bennet [24]: the
skins of PAN based carbon fibers have a remarkable
anisotropy [25], the elementary unit of stripe model is
made up of the sp2 -hybridized carbon atoms [20]. The
examination not only verifies some results presented
previously but also gives some new features of PAN
based carbon fibers that have not proposed in literature.
To the best of our knowledge, it is the first time to report
a detailed investigation on the novel cutting technique
that the graphene based films could be prepared from
PAN based carbon fibers.
2. Experimental Section
2.1. Samples Prepared
PAN based carbon fibers were charged with the electric-
ity for 5 minutes, the samples were immersed into the
acetone liquid for 12 h. The solution of epoxy resin pre-
pared was poured into the rubber mould. A tow of PAN
fibers soaked was cut and embedded in epoxy resin solu-
tion. The mould was dried into the oven at 60˚C. After
solidification, ultrathin sections of samples from longitu-

New Insight into the Graphene Based Films Prepared from Carbon Fibers835
dinal parts were cut respectively on the Reichert-Jung
Ultracut E ultramicrotome using a diamond knife. The
ultrathin sections of samples collected from the distilled
water and were dried to test.
2.2. Characterization
The specimens were examined using a Philips Tecnai
20U-Twin high-resolution transmission electron micros-
copy (HRTEM) at an accelerating voltage of 200 kV. A
Rigaku X-ray diffractometer (D/MAX-rA, Japan) with
Ni-filtered CuKα radiation as the source was used to
study the wide angle at 40 KV and 60 mA, the scanning
speed was 6 deg/min, scanning step was 0.02 deg. The
Raman spectrum were taken with Raman scope of LRS-
LabRam-1B from Jobinyvon with He-Ne gas laser as the
light source, its laser power was 4.3 mW, the excitation
laser was 632.8 nm.
3. Results and Discussion
3.1. HRTEM Analysis of Graphene Based Films
HRTEM images of ultrathin sections prepared from T700
carbon fibers are investigated in Figure 1, it has been
found that such graphene based films have the better
orientation structures and more graphene layers which
regularly piled up and highly oriented, its consistency of
the adjacent graphene based planes is better, several
graphene layers are closely arranged in the ordered ori-
entation texture. The length of each graphene layer in
such films is longer which was about 7 nm on the ave-
rage, the stack height (Lc) and the width (La) of such
graphenes are obviously seen in the range of 1.0 - 2.7 nm
and of 2.4 - 5.2 nm respectively. The interlamellar spac-
ing between graphene layers is about in the range of 0.34
- 0.35 nm.
HRTEM images of ultrathin sections prepared from
T300 carbon fibers are reported in Figure 2, it has been
observed that such graphene based films have the rela-
tively loose orientation structures. The stack height (Lc)
and the width (La) of such graphenes are obviously seen
in the rage of 0.8 - 2.0 nm and of 2.2 - 3.1 nm respec-
tively. The interlamellar spacing between graphene lay-
ers is about in the range of 0.34 - 0.36 nm. After the layer
Figure 1. HRTEM images of ultrathin sections prepared from T700 carbon fibers, (a) low magnification image, the direction
of white arrow is defined as the direction of axis; (c), (d), (e) is high magnification image of C, D, E areas in Figure1 (a), Lc
and La is the stack height and the width in the graphene respectively .

New Insight into the Graphene Based Films Prepared from Carbon Fibers 836
Figure 2. HRTEM images of ultrathin sections prepared from T300 carbon fibers, (a) low magnification image, the direction
of white arrow is defined as the direction of axis; (c), (d), (e) is high magnification image of C, D, E areas in Figure 2(a) re-
spectively, Lc and La is the stack height and the width in the graphene re spectively.
structure turned up in the square region of Figure2(a)
being partially enlarged, it has been found that the length
of each graphene layer in such films is about 4 nm on the
average, which testifies the coherence of such graphene
layers be worse.
3.2. Raman Spectrum Analysis of Graphene
Based Films
The Raman spectroscopy of graphene thin films and
T300 carbon fibers are shown in Figure 3. It appeared
that the common features which are so-called G and D
peaks in the 1000 - 2000 cm–1, the peak at G-band（1580
- 1600 cm–1） which belongs to the Raman-allowed
phonon mode E2g, which involves out-of-phase dis-
placements, the peak at D peak（1350 - 1370 cm–1）which
is the disorder-induced phonon mode due to the infinite
size of crystals and defects. But it has been investigated
that a notable peak at 1620cm–1 appeared for the gra-
phene based thin films, which results from the variation
of carbon atoms on the surface of graphene, also, it has
been demonstrated that the twist of graphene planeresults
in an obvious reduction of distance and the increase of
Figure 3. Raman spectroscopy of the graphene based films
and T300 carbon fibers, BM1 and BM2 graphene based
films were prepared from and T700 and T300 carbon fibers
respectively.
mutual action among carbon atoms. The half width of
G-band for ultrathin section prepared from T700 carbon
fibers is the smaller and becomes comparatively sharp

New Insight into the Graphene Based Films Prepared from Carbon Fibers837
when compared with that of ultrathin section prepared
from T300 carbon fibers, which suggests the graphene
layer be the more parallel along the fiber axis.
The intensity ratio of the D-band against the G-band
(R = ID/IG) is widely used to evaluate the quality of gra-
phene materials, it shows the dependence both on the
degree of graphitization and the orientation of graphite
planed in the surface of graphene materials. As calcu-
lated from the data obtained from Figure 3, the intensity
ratio of a spectral line RBM1= 0.52 < RBM2 = 0.65 < RT300 =
0.78, which clearly demonstrates the relative content of
sp2 -hybridized carbon atoms in BM1 films should be the
highest when compared with that of BM2, on the other
hand, its skeleton structure of carbon atoms becomes
more regular, and its lamellar spacing is more complete
and compact.
3.3. XRD Analysis
The samples were also investigated by XRD as shown in
Figure 4, it has been reported that there is the same
common evident peak at 2

= 25˚ which is termed as
the (002) reflection, the weak peak at 2

= 43˚ which is
ascribed to (100) reflection, the other weak peak at 2

=
55˚ which is attributed to (004) reflection. The stack
height (Lc) and the planar spacing d002 can be calculated
by the Scherrer formula and the Bragg equation respec-
tively. The d002 spacing calculated of 0.332 nm for the
graphene based in BM1 films is slightly smaller than that
of 0.345 nm for BM2 films and that of 0.356 nm for
T300, the stack height (Lc) calculated of 2.05 nm for the
graphene based in BM1 films is larger than that of 1.76
nm for BM2 films and that of 1.44 nm for T300. This
indicates that the graphene based in BM1 films have
relatively high graphitization.
The half-value width in the (002) reflection for BM1
films is smaller than that of BM2 films, which results in
the increasing of graphene based crystallite thickness and
the reducing of interlayer spacing. So the stacking layers
of crystallite become more and more, the porosity among
the crystallite is smaller. It has been found that the dif-
fraction peak in the (002) reflection for BM1 films is
fairly sharp, the intensity is extremely high, which sug-
gest that the planes of hexatomic ring of carbon orderly
stack in the intermolecular acting force, the degree of
orientation for such graphene is better than that of BM2
due to its high stereo-tacticity.
4. Conclusions
The graphene based films prepared from carbon fibers
has been developed by a novel cutting technique –the
ultramicrotomy. The distance between the network-gra-
phene plane in graphene based films prepared from T700
carbon fibers decreases, the order design of graphene is
Figure 4. XRD patterns of the graphene based films and
T300 carbon fibers, BM1 and BM2 graphene based films
were prepared from and T700 and T300 carbon fibers re-
spectively.
denser and the arrangement shows a preferred orientation
along the drawing direction. The relative content of the
forming SP2-hybridized orbit of carbon atoms in the
graphene based films prepared from T700 carbon fibers
is higher.
5. Acknowledgements
The authors are very grateful to Graduate Independent
Innovation Foundation of Shandong University, GIIF-
SDU (2009TS004) and National Basic Research Program
of China (2011CB605601) for providing financial sup-
port.
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