Open Journal of Microphysics, 2013, 3, 1-4
doi:10.4236/ojm.2013.33B001 Published Online August 2013 (
Gas-phase Synthesis of Carbon Nanostructures and
Kh. A. Abdullin1, D. G. Batryshev1, Y. V. Chikhray2, M. T. Gabdullin1,
D. V. Ismailov1, A. K. Togambaeva2
1Al-Farabi KazNU, National Nanotechnological Laboratory of Opened Type, al-Farabi Str, Almaty, Kazakhstan
2Al-Farabi KazNU, Institute of Experimental and Theoretical Physics, al-Farabi Str, Almaty, Kazakhstan
Received May, 2013
CVD synthesis of carbon nanotubes was carried out using ethanol paralysis in tubular quartz reactor at atmospheric
pressure of hydrogen. Ni, Co and Fe catalyst were used for CNT deposition. The CNT samples obtain ed under various
experimental conditions were studied by scanning electron microscopy (SEM), X-ray fluorescent microanalysis and
Raman spectroscopy. The ratio of ID/IG of D ( ~1360 cm-1) and G (~1580 cm-1) Raman peaks was monitored to estimate
the crystalline of graphite-like material. The optimal conditions for synthesis of CNTs on the Si-substrates and on the
SiO2-based fiberglass were determined. MWNT were produced with 25-30 nm diameters, up to 30 microns in length
and with crystallite size La from 2.7 nm to 7 nm. DC electrical properties of carbon composites MWNT/SiO2-fiberglass
were examined. Specific resistance was about 10 cm and more depending on CNT content. It was found that the resis-
tivity of the carbon composites MWNT/SiO2 is sensitive to external pressure. Processing of composite with binding
polymer significantly improves stability and repeatability of its voltage-current characteristics.
Keywords: Carbon Nanotubes (CNT); Chemical Vapor Deposition (CVD); Scanning Electron Microscopy (SEM);
Raman Spectroscopy
1. Introduction
Carbon nanotubes (CNT) have found applications in dif-
ferent areas, such as semiconductor structures on unipo-
lar transistors, field emitters, gas sensors, solar cells, cat-
alysts, ultra capacitors etc [1-9]. CNT-based na-
no-structured composite materials and reinforced poly-
mers have been developed for use in a variety of prod-
ucts. Increasingly wide range of applications of CNT
requires a big amount of low cost materials. Therefore,
the development of low cost techniques of CNT synthe-
sis still remains actual. In the present work, we fabricate a
nanostructure carbon with nickel impurities, carbon na-
notubes and carbon-related composites by gas-phase de-
2. Experiment
The synthesis of CNT by chemical vapor deposition
(CVD) was carried out in hydrogen under the atmos-
pheric pressure. The CVD process was carried out in a
tube quartz reactor (diameter 25 mm) within a tube fur-
nace at temperatures between 600 and 900℃. Ethanol
was used as a carbon source. When the necessary tem-
perature of synthesis was obtained, sweep gas comes via
the bubbler filled with ethanol at room temperature.
Single side polished p-type <111> silicon substrates
with SiO2 layers and catalyst layer of Ni ( 5÷10 nm thick)
were used as a substrate for CNT growth by fixed bed
CVD method. Thin nickel films were deposited on Si
substrates by electron-beam evaporation of Ni target.
Silica based glass fiber was also used as a substrate for
fixed bed growth of CNT. A catalyst was deposited by
wet impregnation method. First of all, 2 g of nickel ni-
trate and 2 g of cobalt nitrate were dissolved into 100 ml
distilled water and 10 g of the silica based glass fiber was
immersed in the solution for 24 hours at ambient tem-
perature. Then the solution was poured out and the glass
fiber was dried at 100℃ for 24 h in an oven. The fibers
were loaded in the reactor, filling the entire diameter of
the tube quartz reactor. Nitrates were reduced under hy-
drogen flow while the desired temperature of CNT
growth is being achieved.
The Fe was used a catalyst and TiO2 powders with
granule size of ~0.2 m was used as a catalyst carrier in
the fluidized bed method. The Fe-loaded TiO2 powder
was prepared by wet impregnation method during proc-
essing of the powder in water solution of iron chloride
for 12 hours, with the following drying at 105℃. The
synthesis was carried out in vertical reactor under hy-
drogen flow.
Copyright © 2013 SciRes. OJM
The properties of obtained samples were studied by
the method of scanning electron microscopy (SEM) with
X-ray fluorescence analysis and Raman spectroscopy.
Electric characteristics of obtained composites were meas-
ured at direct current. The optimal conditions for synthe-
sis of CNT layers were defined.
The Figure 1 shows the morphology of obtained mul-
ti-wall CNT with 25-70 nm in diameter and ~30 m in
length. The Figure 2 demonstrates the Raman spectra of
obtained CNT samples. As it is well known [10], that the
intensity of the D band compared with the Raman- al-
lowed G band depends on the size (La) of the graphite
micro crystals in the sample, and La can be defined by
the Tuinstra–Koenig relationship La = 4.4·I(G)/I(D) nm
which is used for the estimation of sizes of crystallites.
The Raman spectra obtained (Figure 2) demonstrates
that the ratio of I(G)/I(D) depends on parameters of syn-
thesis and the sizes of CNT crystallites are varied from
2.4 nm to 5.2 nm.
Figure 1. SEM of CNT layers on silicon substrates. CNTs
were obtained at ~800℃ for 15 min in hydrogen atmosphere.
The magnification of the SEM images is 150000 (a), 5000 (b)
and 3000 (c). SEM images of the CNT were obtained at a
tilt angle of (a), 7(b) and 9(c).
Figure 2. Raman spectra of CNT layers obtained on Si+Ni
substrates at growth temperatures of 600, 700 and 800℃,
and Raman spectra of CNTs on TiO2 powder with Fe cata-
lyst. The Raman spectra were obtained in a NTEGRA
Spectra spectrometer (NT-MDT) equipped with a 473 nm
excitation laser.
The SEM studies have shown that annealing of silicon
substrates with catalytic nickel layer at temperatures
650-900℃ in the inert or hydrogen atmosphere without
supplying of carbon containing components leads to the
formation of nickel nanoclusters at the surface of silicon
oxide. The average size of nanoclusters ranges from 5 to
50 nm and depends on the thickness of deposited Ni
layer. These nanoclusters are acting as catalysts of CNT
growth by widely-accepted CNT growth mechanism,
which assumes that the h ydrocarbon vapor is adsorbed to
the metal nanoparticles upon reaching supersaturating
and then carbon atoms precipitate out in the form of
The SiO2 based fibers were used as catalyst carriers to
increase the amount of CNT grown in a single experi-
ment. The morphology of obtained samples is shown on
Figure 3. As it can be seen from this figure, the SiO2
fibers are covered more or less uniformly by CNTs
which are 20-80 nm in diameter. Raman scattering spec-
tra have shown that the CNTs deposited on fibers have
lower crystalline than those obtained on Si-Ni substrates.
The Figure 4 shows the morphology of CNTs ob-
tained in vertical fluidized bed reactor with use of Fe
catalyst loaded on TiO2 particles. It can be concluded
from the Raman spectra (Figure 2) that the level of crys-
tallinity of CNTs obtained in fluidized bed is quite high,
the estimated size of crystallites is about 5 nm.
Copyright © 2013 SciRes. OJM
Figure 3. SEM images of CNT layers deposited in hydrogen
atmosphere on SiO2 fibers with Ni-Co catalyst at tempera-
ture of 700℃. The magnification of the SEM images is
15000 (a) and 100000 (b). The bar in the right-lower corner
in frame b is shown as scale of 500 nm.
Figure 4. SEM images of CNT layers deposited on TiO2
powder with Fe catalyst. CNTs were obtained on fluidized
bed catalyst in hydrogen atmosphere at TiO2 powder with
iron catalyst at temperature of 800℃, after 60 minutes of
synthesis, zoom: 100000 (a) and 20000 (b).
Figure 5. Volt-ampere curves and dependence of electrical
conductance from the external pressure for two types of
composites: a– with low content of CNT and b – with high
content of CNT.
The composite material of SiO2 fibers covered with
multi-walled CNTs has a high electrical conductance.
Room temperature direct current (DC) electrical conduc-
tance was measured for these composites. It was found
that resistivity of the composites can be easily varied in
the range from 10 ohm*cm and higher. The resistivity of
the composite depends on synthesis conditions and con-
tent of CNTs in the composite. Voltage-current charac-
teristics were found to be close to the linear dependences
and have shown at Figure 5 for two samples with low (a)
and high (b) CNT content. It was find out that the electric
conductance of composites is quite sensitive to the ex-
ternal pressure.
Electrical resistance of the composite under various
external pressure in the range of 0.03~0.15 MPa, and
when it under the fixed voltage (5 V) decreases rapidly
as the pressure increases. The samples with different
electrical conductance have differen t pressure sensitivity.
The stability of electrical properties and pressure sensi-
Copyright © 2013 SciRes. OJM
Copyright © 2013 SciRes. OJM
tivity of composites is considerably increased by rein-
forcement of the CNT composite structure by impregna-
tion with binding polymer.
3. Acknowledgements
The work was carried out under the support of Ministry
of Education of Kazakhstan, grants GF 1106 and GF
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