N. G. PRIKHODKO ET AL.
(а) (b)
Figure 1. The photo of flames with a catalyst substrate: (a)
plate, (b) cylinder.
Table 1. The flow rate of oxygen depends on the type of fuel
to obtain the desired ratio С/О.
The value of С/О 0.75 0.85 0.95 1.05
2
for С3Н8, cm3/mi n 438.2 386.6 345.9 313.0
2
for С4Н10, cm3/mi n 584.3 515.5 461.3 417.3
at 1351 cm−1, G second peak at 1580 cm−1 and 2D third
peak at 2700 cm−1. The ratio between the intensity of the
G peak (IG) and 2D peak (I2D) gives an estimate of the
number of layers (IG/I2D). For a mono-layer of graphene
and this ratio is less than unity. Raman spectroscopy has
allowed to establish the presence of layered graphene
films, as well as to evaluate the quality of the graphene
layers.
3. Results
The experimental results in the synthesis of the graphene
layers of the premixed combustion of propane and bu-
tane-oxygen mixtures at various ratios of С/О are shown
below. Argon consumption in all experiments was con-
stant and equal to 250 cm3/min. The Results obtained
minimum ratio IG/I2D, characterize the amount of gra-
phene layers on the substrate depending on the fuel
source and the ratio C/O, are given in Table 2.
It is stated that preferably in the flame of propane and
butane is observed under these conditions the formation
of graphene layers in an amount of 5 - 10 layers. The
results of Ram an spectroscopic studies of soot samples
are shown in Figures 2 and 3.
It is found that the graphene layers are formed inde-
pendently of the type of fuel in the studied range of ratios
С/О with a pronounced peak of graphite G. The tendency
for increasing the degree of disorder of the graphene lay-
ers with increasing ratio of С/О, which is characterized
by an increase in the peak intensity D. For propane-
oxygen mixture degree of disorder is observed at a higher
ratio of С/О than for butane-oxygen mixture. However,
butane-oxygen mixture at a ratio of С/О = 0.95 was ob-
tained the minimum number of graphene layers (three
layers, IG/I2D = 1.3, Table 2).
It was studied the effect of argon flow on the synthesis
of graphene layers in its submission to the propane or
butane-oxygen flames. Feed argon flame affects its tem-
perature. There is a process of lowering the temperature
of the flame adjustment to the values of 950˚C - 970˚C,
which is most favorable for the synthesis of graphene
layers. It was necessary to determine the flow rate of
argon, the most favorable for the synthesis of graphene at
different combustion conditions.
It is found that when the ratio of С/О = 0.75 for pro-
pane-oxygen flame increases in argon from 150 cm3/min
to 500 cm3/min not activate the process of the formation
of graphene layers, and leads to the formation of pre-
dominantly amorphous soot structure. However, the ar-
gon flow rate 150 cm3/min there is a clear graphitized
structure that is characterized by the presence of three
peaks characteristic of the graphene layers, Figure 4.
The research for propane-oxygen flame at a ratio of
C/O = 1.05 at different flow rates of argon showed the
presence of layers of graphene, but with the presence of
disorder, which is characterized by a peak of D greater
intensity. When the ratio of C/O = 1.05 with filing 150
cm3/min argon on nickel substrate in propane-oxygen
flame is observed the formation of a minimum number of
graphene layers (three layers—IG/I2D = 1.3).
For butane-oxygen flame at C/O = 0.75 increase in
argon does not lead to the formation of a particulate
amorphous structure. With increasing argon flow rate at
C/O = 0.75 in butane-oxygen flame is observed the for-
mation of graphene layers, and even a minimal amount
of Figure 5 (три слоя—IG/I2D = 1.3).
As a result, studies have found that as the ratio of C/O
trend increases in the degree of disorder of graphene lay-
ers, which is characterized by an increase in the peak
intensity D. For propane-oxygen mixture degree of dis-
order is observed at a higher ratio of C/O than for butane-
oxygen mixture. It is shown that the formation of gra-
phene layers, the optimal value is the ratio of С/О = 0.85
- 0.9 and the flow of argon in the amount of 150 - 250
cm3/min.
Table 2. The minimum ratio IG/I2D depending on the ratio
of C/O and type of fuel.
The value of the ratio, С/О 0.75 0.85 0.95 1.05
Propane, IG/I2D 2.2 1.8 1.5 1.9
Butane, IG/I2D 1.5 2.0 1.3 1.6
OPEN ACCESS MSCE