art%3A10.1007%2Fs10853-014-8312-2.pdf
-
Upload
prasad-raikar -
Category
Documents
-
view
1 -
download
0
Transcript of art%3A10.1007%2Fs10853-014-8312-2.pdf
-
A glycerolwater-based nanofluid containing graphene oxidenanosheets
Ali Ijam A. Moradi Golsheikh R. Saidur
P. Ganesan
Received: 1 February 2014 / Accepted: 7 May 2014 / Published online: 23 May 2014
Springer Science+Business Media New York 2014
Abstract Nanofluids are simply the dispersion of nano-
meter-sized particles in different fluids. Graphene oxide
nanosheets (GONs) were prepared by exfoliating the
graphite oxide. The GONs were investigated using Fourier
transform-infrared spectroscopy, Raman spectroscopy,
XRD analysis, high-resolution emission electron micros-
copy, transmission electron microscopy, and UVvisible
spectroscopy. GONs/glycerolwater-based nanofluid was
prepared by the two-step method. The stability of the
nanofluid was investigated with respect to time. Thermal
and electrical conductivity of the prepared nanofluid was
examined with different temperatures (2545 C) andweight fractions (0.020.1 wt%). The nanofluid is found to
be stable for more than 5 months. The results showed an
enhancement in thermal conductivity of about 4.5 % at
25 C with a weight fraction of 0.02 %. The improvementwas up to 11.7 % with a weight fraction of 0.1 wt% at
45 C. The electrical conductivity was increased withincreasing the weight fraction and temperature. The
improvement in electrical conductivity was about 5890 %
at 25 C and 0.1 wt%.
Introduction
The rapid development across all the sectors, such as
industrial, transportation, defense, and space, generate a
numerous amount of heat. A small heat transfer system is
required for many applications like electronic cooling in
computers and microprocessors, engine cooling in the
automobile, cooling in space, etc. The conventional fluids,
such as water, ethylene glycol, glycerol, mineral oil, etc.,
have very low thermal conductivities. A better technique is
continuously being explored to improve the thermal per-
formance of the conventional fluid. Thus, dispersing of
nano-sized particle of highly thermal conductivity to the
base fluid was introduced by Choi and Eastman [1] in
Argonne National Laboratory, which termed as nano-
fluid. Eastman et al. [2] examined the thermal conduc-
tivity of ethylene glycol containing copper nanoparticles. It
was found that the thermal conductivity improved by 40 %
by dispersing 0.3 vol%. Choi et al. [3] found that the
thermal conductivity of poly(a-olefin) oil nanofluid raisedby 160 % by adding CNT with 1 vol%. Assael et al. [4]
inspected the enhancement of the thermal conductivity of
water in the presence of MWNT and sodium dodecyl sul-
fate (SDS) as a surfactant. The enhancement of 38 % was
obtained by dispersing 0.6 vol%.
The discovery of graphene by Novoselov and co-
authors [5] has attracted much attention due to two-
dimensional structure, unique physical and chemical
properties [6]. Graphene is a single atom thick nanosheet
of sp2-bonded packed into a honeycomb lattice. Graphene
has shown unusual mechanical, thermal, and electrical
properties such as very high carrier mobility [6], long-
range ballistic transport at room temperature [7], quantum
confinement in nanoscale ribbons [8], single molecule gas
detection sensitivity [9], and high young modules and
A. Ijam R. Saidur (&) P. GanesanDepartment of Mechanical Engineering, University of Malaya,
50603 Kuala Lumpur, Malaysia
e-mail: [email protected]
A. Moradi Golsheikh
Low Dimensional Materials Research Centre (LDMRC), Physics
Department, Faculty of Science, University of Malaya,
50603 Kuala Lumpur, Malaysia
R. Saidur
UM Power Energy Dedicated Advanced Centre (UMPEDAC),
University of Malaya, Level 4, Wisma R & D,
50603 Kuala Lumpur, Malaysia
123
J Mater Sci (2014) 49:59345944
DOI 10.1007/s10853-014-8312-2
-
fracture strength [5]. The thermal conductivity of graph-
ene near room temperature was about 30005000 W/m K
[10]. Due to superb thermal conduction of graphene, it
became an excellent candidate for the thermal manage-
ment [10]. The thermal conductivity of graphene oxide
ethylene glycol nanofluid was reported for the first time
by Yu et al. [11]. An improvement of 61 % at loading of
5 vol% of graphene oxide nanosheets (GONs) was
obtained in room temperature. Thermal conductivity of
graphene oxide with different based fluids (distilled water,
propyl glycol, and liquid paraffin) was reported [12]. At a
load of 5 vol%, the enhancement of the thermal conduc-
tivity for nanofluid was about 30.2, 62.3, and 76.8 % for
the distilled water, propyl glycol, and liquid paraffin,
respectively. Baby and Ramaprabhu [13] prepared and
study the thermal and electrical conductivity of the ther-
mal exfoliated graphene (TEG) water and ethylene glycol-
based nanofluid with a volume fraction of about
0.0050.056 vol% with temperature range (2550 C).They found that the thermal and electrical conductivity
(TEGwater nanofluid) was enhanced about 64 and
1400 % for a volume fraction 0.056 %. For the ethylene
glycol, an enhancement in thermal conductivity of about
67 % was reported.
Yu et al. [14] reported a high thermal conductivity
improvement of about 86 % for the graphene/water nano-
fluid at 30 C and loading of 5 vol%. The sodium dodecyl-benzenesulfonate (SDBS) was used as a surfactant. Arav-
ind and Ramaprabhu [15] reported the in-situ reduction of
the graphite oxide nanofluid under strong alkaline treat-
ment. The investigation of the thermal and electrical con-
ductivity of the graphene ethylene glycol and water
nanofluid was carried out. The maximum enhancement for
the thermal conductivity was about 94.1 % for the water
and 36.1 % for the ethylene glycol with a loading of
0.14 vol%. Furthermore, the electrical conductivity
improvement was about 190 and 55 % for ethylene glycol
and water, respectively.
In this paper, graphene oxide was prepared by the
chemical method. To the best of our knowledge, there is no
report about the thermal and electrical conductivity for the
graphene oxide glycerolwater mixture nanofluid. The
stability and the effect of temperature and weight fraction
on them were investigated.
Experimental
Preparation of the exfoliated graphite GO
Graphite flakes (code no. 3061) were purchased from
Asbury Graphite Mills, Inc (Asbury, NJ). Sulfuric acid
(H2SO4, 98 %), phosphoric acid (H3PO4, 85 %), potassium
permanganate (KMnO4, 99.9 %), hydrogen peroxide
(H2O2, 30 %), and glycerol (C3H8O3, 86 wt%) were pur-
chased from Merck (Darmstadt, Germany). Hydrogen
chloride (HCl, 37 %) was purchased from Sigma-Aldrich
(St Louis, MO).
Exfoliated graphite oxide has been prepared based on
modified Hummers method [16]. Typically, graphite flakes
were oxidized by mixing H2SO4 and H3PO4 with a ratio 4:1
(v/v) at the room temperature. The graphite and potassium
permanganate were added slowly to the above mixture
solution. Then, the mixtures were left for stirring for 3 days
to complete the oxidation of the graphite. After that, hydro-
gen peroxide was added to stop the reaction. The mixture was
sonicated and washed with HCl and water for several times
until pH became neutral. During the washing and sonication
process, the graphite oxide was exfoliated to GONs. The
product was dried in a vacuum oven overnight at 60 C. Theobtained powder was a loose brown with hydrophilic nature.
Figure 1 shows the chemical exfoliation of graphite oxide.
Nanofluid preparation
Two-step method was used to prepare the nanofluid. First,
based fluid was obtained by mixing glycerol (Gly) with
water with the ratio of 4:1 (w/w) and stirred for 1 h to
ensure the homogenization of the base fluid. Then, the
dried (GO) was added to Gly/water with different mass
fractions of (0.020.1) wt%. The mixture was sonicated
and stirred for 1 h using sonication bath (40 kHz, 280 W).
Figure 2 shows the two-step method for preparing the
nanofluid. This is to confirm the uniform suspension of GO
in (Gly ? water).
Characterization, thermal, and electrical conductivity
measurements
Fourier transforms infrared spectroscopy (FTIR) was used
to examine the functional group on the surface of the GO.
FTIR measurements were carried out using a Perkin
Elmer System series 2000 spectrophotometer (USA) in the
range of 4004000 cm-1. The Raman spectra were gained
with a Renishaw Invia Raman Microscope using a laser
with a wavelength of 514 nm. Power X-ray diffraction
characterization was performed using a PANalytical
XPERT Pro X-ray diffractometer with nickel-filtered
Cu Ka radiation as the X-ray source (k = 1.54056 A).The pattern was recorded in the 2h range of 5 to 60 withstep size of 0.026 and scanning speed of 0.1/s. The UVabsorption spectra were achieved by using Cary 50 Bio
UV/visible spectrophotometer with wavelength of
800200 nm. The morphology of GO was identified by
field emission scanning electron microscopy (FESEM,
Hitachi SU8000). Transmission electron microscopy was
J Mater Sci (2014) 49:59345944 5935
123
-
Fig. 1 Chemical exfoliation of graphite oxide
Fig. 2 An illustration shows the nanofluid preparation and the detail of the experiment set up
5936 J Mater Sci (2014) 49:59345944
123
-
carried out using (TEM, Hitachi HT7700). For TEM
characterization, the graphene oxide was suspended in
absolute ethanol by the aid of sonication. Then, drop the
dispersion on carbon-coated copper grid, and drying it in
air.
The measurement of nanofluids thermal conductiv-
ity was accomplished by KD2 Pro instrument based on
transient hot wire (THW) method. KD2 Pro has three
sensors for measuring different types of materials with
accuracy of 5 %. As suggested by the manufacture
(decagon devices), the KS-1 sensor with length of 6 cm
and 1.3 mm diameter was used for the liquid. In order
to investigate the effect of temperature on the thermal
conductivity of nanofluid, thermal circulating bath
(polyScience) was used to control the temperature. The
nanofluid samples were sealed in glass container and
immersed in thermal bath. The KD2 Pro was cali-
brated daily with glycerin and distilled water before
taking the measurements. The measured value was
0.288 and 0.6 W/m K at 20 C for glycerin and watercorrespondingly, which are in good agreement with the
literature values of 0.285 and 0.602 W/m K,
respectively.
The error of the measurements was less than 1 %. The
manufacture asserted that the sensor has accuracy within
5 %. Minimum of five readings were taken for each
temperature, and the average value was reported. EU-
TECH instruments, Bench conductivity/TDS meter was
used to measure the electrical conductivity of nanofluid.
The meter was calibrated with distilled water and ethyl-
ene glycol. The error of the measurements was less than
5 %. The sample was placed in a water jacket of the
adapter which was connected to the overstated thermal
circulating bath in order to investigate the effect of tem-
perature on the electrical conductivity. Figure 2 shows the
details of the experiment set up. Five measurements were
taken for each temperature, and the average value was
reported.
Results and discussion
FTIR, Raman spectra, and XRD
Figure 3 shows the FTIR spectra for graphite and graphene
oxide, respectively. For the graphite curve, two peaks at
2925 and 2856 cm-1 are corresponding to the asymmetric
and symmetric vibrations of CH2 groups [17]. The peak at
1634 cm-1 is assigned to the presence of a C=C bond in
graphite [18]. For graphene oxide, a very broad band at
3406 cm-1 refers to stretching vibration of OH [19]. The
peak at 1622 cm-1 is ascribed to the contribution from the
vibration of the aromatic C=C group [20]. The peaks at
1733 and 1367 cm-1 are attributed to C=O and CC
stretching vibration of carboxylic group [21]. This result
shows that the function groups are extensively introduced
to the structure of the carbon. The peak at 1225 cm-1
contributed to COC stretching [22]. Furthermore, the
peaks at 1162 and 1040 cm-1 could be assigned to CO
vibration of epoxy or alkoxy group [23]. This confirms the
successful formation of graphene oxide.
Raman spectroscopy is a powerful technique that used
for characterization of the structure of graphitic materials.
The Raman spectrum for graphite displays a highly strong
peak at 1582 cm-1 (G band) and a very weak peak at
1353 cm-1 (D band). The G band refers to the first-order
scattering of the E2g vibration in sp2 carbon atoms. The D
band represents the sp3 hybridization of carbon atoms and
structure defects, which are caused by breathing mode of
the K-point phonons of A1g symmetry [24]. The ratio of D
band to G band intensities (ID/IG) was only 0.02 indicating
that the graphite is highly ordered structure with low
defects [25]. In graphene oxide, the G band was shifted and
broadened to 1608 cm-1; however, the D band became
eminent in 1349 cm-1. The ratio of D band to G band
intensities for graphene oxide (ID/IG = 0.81) was higher
than graphite. This is due to severe oxidation of graphite by
strong acid during the preparation, which causes destruc-
tion of the sp2 character and creation defects in the
graphene sheets (Fig. 4).
The structure of the crystal was examined using XRD.
Figure 5 shows the XRD result for graphite and graphene
oxide. The graphite shows a strong peak at 26.54 associ-ated with (002) reflection of graphite and interlayer spacing
of 0.335 nm estimated by Braggs equation. Moreover, it
demonstrates an extra peak (004) at 2h = 54.6, corre-sponding to an interlayer distance of 0.167 nm. The peak
of (002) has been shifted to 9.21 after oxidation of
Fig. 3 FTIR for graphite and graphene oxide
J Mater Sci (2014) 49:59345944 5937
123
-
graphite. The d-spacing of GO now rises to 0.95 nm. The
increase in interlayer spacing is due to the formation of a
large number of oxygen containing function groups in
between the graphene sheets. Additionally, there is a small
lump close to 18.1 reveals that the graphite was notcompletely oxidized [20].
Morphology, stability, and UVvisible
The morphology of graphene oxide has been inspected by
high-resolution field emission electron microscopy (FE-
SEM) and TEM as shown in Fig. 6ac. The images show a
winkled surface and folds at the edges of the nanosheets.
Furthermore, the TEM image shows the transparent
graphene nanosheets which appeared in style of few layer.
The size of the graphene nanosheets is in the range of
0.52 lm, and few of them are larger than 3 lm. Thestability of the graphene oxide nanofluid is checked by
measuring the thermal conductivity with time for several
days. The stability of the nanofluid is reflected with time
through the constancy in thermal conductivity of it.
According to Fig. 7, it can be seen that the thermal
conductivity of all the samples remains constant with time
(14 days). This confirmed that the nanofluid is highly sta-
ble. Figure 6d, e shows the nanofluid just prepared and
after 5 months. The digital photographs of the graphene
oxide with different loadings show that there are no sedi-
mentations observed after 5 months of the prepared nano-
fluid. Additionally, the stability of the nanofluid was
confirmed by UVvisible spectroscopy.
UVvisible spectroscopy is an appropriate procedure to
investigate the stability of nanocolloids quantitatively.
Figure 8 shows the UVvisible spectrum of GO suspended
in Gly/water. The main absorption peak at 230 nm which
refers to the p ? p* transition of aromatic CC. There is asmall shoulder peak around 300 nm assigned to n ? p*transition of C=O bond [18]. The UVvisible was mea-
sured after 5 months and there are no distinguish differ-
ences in intensity between the nanofluid just prepared and
after 5 months. It exhibited a long-term stability due to
hydrophilic nature of the graphene oxide and glycerol
water mixture (Fig. 8).
Thermal conductivity of nanofluid
The thermal conductivity of nanofluid was measured with
the different weight fractions at 30 C as shown in Fig. 9.The results showed that the thermal conductivity was
increased with increasing the loading of the graphene
oxide. Figure 10 shows the effect of temperature on the
thermal conductivity enhancements with different weight
fraction. The thermal conductivity increased with raising
the temperature. It exhibited a nonlinear behavior with
temperature, and the nonlinear behavior was already stated
for the carbon-based nanofluid [2]. The enhancement per-
centage was calculated based on the formula below:
%Enhancment knf koko
100; 1
where knf and ko are the thermal conductivity of nanofluid
and the base fluid, respectively. A maximum enhancement
of 4.5 % was achieved at 25 C with 0.02 wt%. Thehighest improvement in thermal conductivity of Gly
water-based nanofluid is about 11.7 % at 45 C with0.1 wt%.
The enhancement in thermal conductivity was reported
by several researches due to effect of the Brownian motion
of the nanoparticles and the micro-convection caused by
Brownian motion [2628]. On the other hand, the
Fig. 4 Raman spectra for graphite and graphene oxide (GO)
Fig. 5 XRD analysis for graphite and graphene oxide (GO)
5938 J Mater Sci (2014) 49:59345944
123
-
enhancement in thermal conductivity is owing to the per-
colation structure formed by the nanoparticles, which acts
as conducting path [29, 30]. The thermal conductivity and
the stability were compared with other reports based on the
enhancement as explained in Tables 1 and 2. Yu et al. [12,
14] examined the thermal conductivity of the graphene
oxide in distilled water and ethylene glycol with the vol-
ume fraction of 15 %. His results showed that an
improvement was about 30.2 and 61 % with a loading of
5 %. The enhancements were almost constant with respect
to the temperature. It can be seen that the high concen-
tration of the graphene oxide in the base fluid will limit the
effect of the Brownian motion of the nanoparticle induced
by micro-convection. The GONs became nearer to each
other and cause the formation of percolation structure [31].
Unlike, Baby and Ramaprabhu [13] showed a high
improvement (64 %) in thermal conductivity of the water
by dispersing graphene nanosheets with 0.056 vol% at
50 C. Similarly, he prepared nanofluid by dispersingfunctionalized hydrogen exfoliated graphene (f-HEG) in
deionized water [32]. His results claimed that an
enhancement of 75 % was achieved. In both studies, the
enhancements were dependent on the temperature. The
mechanism of the Brownian motion of the nanoparticle
Fig. 6 a FESEM and b, c TEM for graphene oxide nanosheets. Digital photo of the nanofluid d just prepared and e after 5 months
Fig. 7 Thermal conductivity of nanofluid with timeFig. 8 UVvisible spectroscopy of GOGly/water
J Mater Sci (2014) 49:59345944 5939
123
-
caused the raising the thermal conductivity of the nano-
fluid. Gupta et al. [33] examined the thermal conductivity
of the graphene nanosheets nanofluid and a maximum
enhancement of 27 % was obtained. According to his
study, the size of the particle and amount of loading play an
important role in interconnected network formation.
In the present study, the based fluid thermal conductivity
did not display much enhancement with respect to tem-
perature. The size of the GO sheets was claimed to be from
0.5 to 2 lm, and the concentration was from 0.02 to0.1 wt%. It was larger than size of the graphene nanosheets
obtained in Gupta and smaller than Yu. In our opinion, the
enhancement in the thermal conductivity of the base fluid
because of two reasons. First, the larger size of GONs will
be near each other, and form interconnects network like
chain structure subsequent percolation theory. Second, the
random motion of the smaller size of the nanosheets will
cause Brownian motion. As a result, the micro-convection
produced by Brownian motion will enhance the thermal
conductivity with an increase in temperature. This result
has a good agreement with previous report [33]. It was
suggested by Jang and Choi [27] that the random motion of
the nanoparticles (Brownian motion) will increase, and the
viscosity of the base fluid will decrease due to the raising
the temperature. The micro-convection happened because
the Brownian motion of nanoparticle, which results in
increased the thermal conductivity. The pure glycerol is
highly viscous but in this study the glycerol contains about
14 % water. Moreover, it was mixed with water, and the
viscosity decreased. However, Tadjarodi and Zabihi [34]
measured the thermal conductivity of the mSiO2glycerol
nanofluid. Their results showed that there is no obvious
effect on the thermal conductivity while increasing the
temperature. The fact is that the suspension was converted
to gel-like form because of the high concentration, which
reduces the effect of Brownian motion. In addition, the
thermal conductivity enchantment was lower than other
reports [13, 32, 33, 35]. The graphite flakes were treated by
strong acid which can cause defects on the structure of the
graphite oxide sheets. The graphene oxide was prepared by
exfoliating the graphite oxide by using sonication. The
sonication process has a bad impact, which can cause
breaking the large sheets of the graphene oxide. It was
confirm earlier by Raman spectra which shows that the
graphene oxide contains higher defects than the graphite
flakes. These defects have a great effect on the thermal
conductivity of the graphene oxide.
Meanwhile other researchers [3638] reported a very
high thermal conductivity improvement because of the
presence of the nanoparticles which formed on the surface
of the graphene nanosheets.
Electrical conductivity of nanofluid
The effect of weight fraction and temperature on the
electrical conductivity of the graphene oxide nanofluid has
been examined as shown in Figs. 11 and 12. The results
showed that the electrical conductivity increased with
increasing the weight fraction. For example, the electrical
conductivity of the base fluid at 25 C is 0.32 lS/cm.However, the electrical conductivity has been increased to
19.17 lS/cm when the weight fraction increased to 0.1 %.Furthermore, the electrical conductivity improved when the
temperature rose. The temperature and weight fraction
have a positive effect on the electrical conductivity of the
nanofluid. The maximum enhancement for electrical con-
ductivity was computed based on the below formula:
Fig. 9 Effect of the loading on the thermal conductivity
Fig. 10 Effect of temperature on the thermal conductivityenhancements
5940 J Mater Sci (2014) 49:59345944
123
-
%Enhancment r roro
100; 2
where r is the electrical conductivity of the nanofluid andro is electrical conductivity of the based fluid. A max-imum enhancement of about 5890 % was achieved at
25 C with 0.1 %. Baby and Ramaprabhu [13] examinedthe electrical conductivity of the graphene/DI water. His
results showed an enhancement of 1400 % was achieved at
25 C. Table 3 summaries the previous studies on electri-cal conductivity of nanofluid. The electrical double-layer
(EDL) characteristics, weight fraction, ionic concentra-
tions, and other physicochemical properties are the factors
that significantly change the electrical conductivity of
colloidal nanosuspensions in a liquid [40]. An enhance-
ment in electrical conductivity with respect to the base
fluid is resulted from the related EDL interactions and the
net charge effect of the solid [41, 42]. When GONs
dispersed in polar solvent (Gly ? water), electric charges
develop on the surfaces/surrounding of the particle. This is
because of the development of the charged diffuse layer
when ions of charge opposite to that of the particle surface
are attached.
This charged diffuse layer, which is known as EDL [41], can
be characterized using j-1 (Debye length) parameter. Conse-quently, conduction mechanisms through the suspension are
enhanced. In addition, the presence of uniformly dispersed
nanoparticles increases the electrophoretic mobility. There-
fore, the effective electrical conductivity of the nanofluid sus-
pension increases [40]. The availability of conducting
pathways increases in the solution as the particle volume
fraction increases and as a result the overall electrical con-
ductivity of the solution increases. An increase in temperature
has a positive effect on the enhancement in the electrical con-
ductivity of the nanoparticle suspension [40] (i.e., j-1 (i.e.,EDL thickness) increases) according to DLVO theory [41].
Table 1 Thermal conductivity of graphene materials nanofluid and their enhancements
Researcher Base fluid Material Synthesis method Loading TC
(%)
Yu et al. [11] Ethylene glycol GONs Modified Hummers
method
15 vol% 61
Yu et al. [12] Distilled water GONs Modified Hummers
method
15 vol% 30.2
Baby and Ramaprabhu
[13]
Water GNs Hummers method 0.0050.056 vol% 64
Baby and Ramaprabhu
[13]
Ethylene glycol GNs Hummers method 0.0050.05 vol% 67
Yu et al. [14] Ethylene glycol GNs Modified Hummers
method
15 vol% 86
Baby and Ramaprabhu
[36]
Deionized water HEG coated with Ag
nanoparticles
Hummers method 0.0050.05 vol% 86
Ethylene glycol HEG coated with Ag
nanoparticles
Hummers method 0.010.07 vol% 14
Baby and Ramaprabhu
[37]
Deionized water HEG coated with CuO
nanoparticles
Hummers method 0.0050.05 vol% 90
Ethylene glycol HEG coated with CuO
nanoparticles
Hummers method 0.010.07 vol% 23
Baby and Ramaprabhu
[32]
Deionized water f-HEG Hummers method 0.0050.05 vol% 75
Ethylene glycol f-HEG Hummers method 0.050.08 vol% 5
Gupta et al. [33] water GNs Hummers method 0.010.2 vol% 27
Aravind and Ramaprabhu
[15]
Deionized water GNs Hummers method 0.0090.14 vol% 94.3
Ethylene glycol GNs Hummers method 0.0080.14 vol% 36.1
Aravind and Ramaprabhu
[38]
Deionized water GNs wrapped MWNT Hummers method 0.0110.04 vol% 97.5
Ethylene glycol GNs wrapped MWNT Hummers method 0.0110.04 vol% 24
Kole and Dey [39] Distilled water/ethylene
glycol
f-HEG Hummers method 0.0410.395 vol% 17
Ghzatloo et al. [35] Deionized water FG CVD method 0.010.05 % 13.5
Present study Gly/water GONs Modified Hummers
method
0.020.1 wt% 11.7
J Mater Sci (2014) 49:59345944 5941
123
-
Conclusion
In this study, the graphene oxide nanosheets (GONs) has
been prepared by using chemical method. The stability of
the GONs/glycerolwater nanofluid was investigated. The
effect of concentration and temperature on the thermal and
electrical conductivity has been examined. The following
conclusion can be gained:
(1) The thermal conductivity of the nanofluid remained
almost constant within 14 days. It reflects the high
Table 2 The stability ofgraphene materials nanofluid
with different base fluid
Researcher Base fluid TC
measurement
Temperature
(C)Stability
Yu et al. [11] Ethylene glycol THW 1060 More than 2 months
Yu et al. [12] Distilled water THW 1060 Long-term stability
Yu et al. [14] Ethylene glycol THW 1060 Stable
Baby and
Ramaprabhu [13]
Water KD2 Pro 2550 N/A
Baby and
Ramaprabhu [36]
Deionized water KD2 Pro 2570 No visible settling of HEG/Ag
after 2 months
Ethylene glycol KD2 Pro 2570 No visible settling of HEG/Ag
after 2 months
Baby and
Ramaprabhu [37]
Water KD2 Pro 2550 N/A
Ethylene glycol KD2 Pro 2550 N/A
Baby and
Ramaprabhu [32]
Deionized water KD2 Pro 2550 No sedimentation was
observed after 2 months
Ethylene glycol KD2 Pro 2550 No sedimentation was
observed after 2 months
Gupta et al. [33] Water THW 20 Stable for more than 6 months
Aravind and
Ramaprabhu [15]
Deionized water KD2 Pro 2550 Stable more than 1 month
Ethylene glycol KD2 Pro 2550 Stable more than 1 month
Aravind and
Ramaprabhu [38]
Deionized water KD2 Pro 2550 Stable for more than 6 months
Ethylene glycol KD2 Pro 2550 Good stability
Kole and Dey [39] Distilled water/
Ethylene glycol
THW 1070 Stable for more than 5 months
Ghzatloo et al. [35] Deionized water KD2 Pro 1050 Long-term stability
Present study Gly/water KD2 Pro 2545 Stable more than 5 months
Fig. 11 Electrical conductivity versus weight fractionFig. 12 Electrical conductivity of nanofluid with the temperature
5942 J Mater Sci (2014) 49:59345944
123
-
stability of the nanofluid. UVvisible was confirmed
the stability of the nanofluid after 5 months.
(2) The thermal conductivity of the Glywater was
increased by suspending the GONs. The thermal
conductivity increased with raising the temperature
in a nonlinear manner.
(3) An improvement of 4.5 % in thermal conductivity
for GONs/Glywater nanofluid was gained at 25 Cwith a weight fraction of 0.02 %. In addition, the
thermal conductivity enhanced up to 11.7 % at
45 C with a weight fraction of 0.1 wt%.(4) The electrical conductivity increased linearly with
increasing the temperature and weight fraction. A
maximum enhancement of 5890 % in electrical
conductivity at 25 C and 0.1 % weight fractionwas obtained.
Acknowledgements The first author would like to thank Mr.Mohammed Ijam for his kind support and valuable discussion. This
work was supported by the High Impact Research Grant (HIRG)
Scheme (UM-MOHE) Project No. UM.C/HIR/MOHE/ENG/40.
References
1. Choi SU, Eastman J (1995) Enhancing thermal conductivity of
fluids with nanoparticles. Argonne National Lab., Argonne
2. Eastman JA, Choi SUS, Li S, Yu W, Thompson LJ (2001)
Anomalously increased effective thermal conductivities of eth-
ylene glycol-based nanofluids containing copper nanoparticles.
Appl Phys Lett 78:718720
3. Murshed SMS, Leong KC, Yang C (2005) Enhanced thermal
conductivity of TiO2-water based nanofluids. Int J Therm Sci
44:367373
4. Assael MJ, Chen CF, Metaxa I, Wakeham WA (2004) Thermal
conductivity of suspensions of carbon nanotubes in water. Int J
Thermophys 25:971985
5. Geim AK, Novoselov KS (2007) The rise of graphene. Nat Mater
6:183191
6. Novoselov K, Geim AK, Morozov S, Jiang D, Grigorieva MKI,
Dubonos S, Firsov A (2005) Two-dimensional gas of massless
Dirac fermions in graphene. Nature 438:197200
7. Berger C, Song Z, Li X, Wu X, Brown N, Naud C, Mayou D, Li
T, Hass J, Marchenkov AN, Conrad EH, First PN, de Heer WA
(2006) Electronic confinement and coherence in patterned epi-
taxial graphene. Science 312:11911196
8. Chen Z, Lin Y-M, Rooks MJ, Avouris P (2007) Graphene nano-
ribbon electronics. Phys E 40:228232
9. Schedin F, Geim AK, Morozov SV, Hill EW, Blake P, Katsnel-
son MI, Novoselov KS (2007) Detection of individual gas mol-
ecules adsorbed on graphene. Nat Mater 6:652655
10. Balandin AA, Ghosh S, Bao W, Calizo I, Teweldebrhan D, Miao
F, Lau CN (2008) Superior thermal conductivity of single-layer
graphene. Nano Lett 8:902907
11. Yu W, Xie H, Bao D (2010) Enhanced thermal conductivities of
nanofluids containing graphene oxide nanosheets. Nanotechnol-
ogy 21:055705 (7 pp)
12. Yu W, Xie H, Chen W (2010) Experimental investigation on
thermal conductivity of nanofluids containing graphene oxide
nanosheets. J Appl Phys 107:094317 (6 pp)
13. Baby TT, Ramaprabhu S (2010) Investigation of thermal and
electrical conductivity of graphene based nanofluids. J Appl Phys
108:124308 (6 pp)
14. Yu W, Xie H, Wang X, Wang X (2011) Significant thermal
conductivity enhancement for nanofluids containing graphene
nanosheets. Phys Lett A 375:13231328
15. Aravind SSJ, Ramaprabhu S (2011) Surfactant free graphene
nanosheets based nanofluids by in situ reduction of alkaline
graphite oxide suspensions. J Appl Phys 110:124326 (5 pp)
16. Ming HN (2010) Simple room-temperature preparation of high-
yield large-area graphene oxide. Int J Nanomed 6:34433448
17. Khanra P, Kuila T, Bae SH, Kim NH, Lee JH (2012) Electro-
chemically exfoliated graphene using 9-anthracene carboxylic
Table 3 Electrical conductivityof different nanofluid and their
enhancements
Researcher Base fluid Material Temperature
(C)EC
enhancement
Baby and Ramaprabhu
[13]
Water GNs 2550 1400 %
Ethylene glycol GNs 2550 220 %
Baby and Ramaprabhu
[37]
Deionized water HEG/CuO 2550 N/A
Ethylene glycol HEG/CuO 2550 N/A
Baby and Ramaprabhu
[32]
Deionized water f-HEG 2550 N/A
Ethylene glycol f-HEG 2550 N/A
Aravind and
Ramaprabhu [15]
Deionized water GNs 2550 55 %
Ethylene glycol GNs 2550 190 %
Aravind and
Ramaprabhu [38]
Deionized water GNs wrapped
MWNT
2550 N/A
Kole and Dey [39] Distilled water/Ethylene
glycol
GNs 1070 8620 %
Minea and Luciu [43] Distilled water Al2O3 2570 390.11 %
Ganguly et al. [40] Water Al2O3 2445 2127 %
White et al. [44] Propylene glycol ZnO 25 100-fold
Wong and Kurma [45] Water Al2O3 250 3457.1 %
Present study Gly/water GONs 2545 5890 %
J Mater Sci (2014) 49:59345944 5943
123
-
acid for supercapacitor application. J Mater Chem
22:2440324410
18. Khanra P, Kuila T, Kim NH, Bae SH, Yu D-s, Lee JH (2012)
Simultaneous bio-functionalization and reduction of graphene
oxide by bakers yeast. Chem Eng J 183:526533
19. Moradi Golsheikh A, Huang NM, Lim HN, Zakaria R, Yin C-Y
(2013) One-step electrodeposition synthesis of silver-nano-
particle-decorated graphene on indiumtin-oxide for enzymeless
hydrogen peroxide detection. Carbon 62:405412
20. Van Khai T, Na HG, Kwak DS, Kwon YJ, Ham H, Shim KB,
Kim HW (2012) Significant enhancement of blue emission and
electrical conductivity of N-doped graphene. J Mater Chem
22:1799218003
21. Kaniyoor A, Baby TT, Ramaprabhu S (2010) Graphene synthesis
via hydrogen induced low temperature exfoliation of graphite
oxide. J Mater Chem 20:84678469
22. Cheng C, Nie S, Li S, Peng H, Yang H, Ma L, Sun S, Zhao C
(2013) Biopolymer functionalized reduced graphene oxide with
enhanced biocompatibility via mussel inspired coatings/anchors.
J Mater Chem B 1:265275
23. Pham VH, Cuong TV, Hur SH, Oh E, Kim EJ, Shin EW, Chung
JS (2011) Chemical functionalization of graphene sheets by
solvothermal reduction of a graphene oxide suspension in N-
methyl-2-pyrrolidone. J Mater Chem 21:33713377
24. Ferrari AC, Robertson J (2000) Interpretation of Raman spectra
of disordered and amorphous carbon. Phys Rev B 61:07541413
25. Seo J-M, Jeon I-Y, Baek J-B (2013) Mechanochemically driven
solid-state DielsAlder reaction of graphite into graphene nano-
platelets. Chem Sci 4:42734277
26. Prasher R, Bhattacharya P, Phelan PE (2005) Thermal conduc-
tivity of nanoscale colloidal solutions (nanofluids). Phys Rev Lett
94:025901 (4 pp)
27. Jang SP, Choi SUS (2004) Role of Brownian motion in the
enhanced thermal conductivity of nanofluids. Appl Phys Lett
84:43164318
28. Shima PD, Philip J, Raj B (2009) Role of microconvection
induced by Brownian motion of nanoparticles in the enhanced
thermal conductivity of stable nanofluids. Appl Phys Lett
94:223101 (3 pp)
29. John P, Shima PD, Baldev R (2008) Evidence for enhanced
thermal conduction through percolating structures in nanofluids.
Nanotechnology 19:305706 (7 pp)
30. Sastry NNV, Avijit B, Sundararajan T, Sarit KD (2008) Pre-
dicting the effective thermal conductivity of carbon nanotube
based nanofluids. Nanotechnology 19:055704 (8 pp)
31. Wang B, Hao J, Li H (2013) Remarkable improvements in the
stability and thermal conductivity of graphite/ethylene glycol
nanofluids caused by a graphene oxide percolation structure.
Dalton Trans 42:58665873
32. Baby TT, Ramaprabhu S (2011) Enhanced convective heat
transfer using graphene dispersed nanofluids. Nanoscale Res Lett
6:289 (9 pp)
33. Gupta SS, Manoj Siva V, Krishnan S, Sreeprasad TS, Singh PK,
Pradeep T, Das SK (2011) Thermal conductivity enhancement of
nanofluids containing graphene nanosheets. J Appl Phys
110:084302 (6 pp)
34. Tadjarodi A, Zabihi F (2013) Thermal conductivity studies of
novel nanofluids based on metallic silver decorated mesoporous
silica nanoparticles. Mater Res Bull 48:41504156
35. Ghozatloo A, Shariaty-Niasar M, Rashidi AM (2013) Preparation
of nanofluids from functionalized graphene by new alkaline
method and study on the thermal conductivity and stability. Int
Commun Heat Mass 42:8994
36. Baby TT, Ramaprabhu S (2011) Synthesis and nanofluid appli-
cation of silver nanoparticles decorated graphene. J Mater Chem
21:97029709
37. Baby TT, Ramaprabhu S (2011) Synthesis and transport prop-
erties of metal oxide decorated graphene dispersed nanofluids.
J Phys Chem C 115:85278533
38. Aravind SSJ, Ramaprabhu S (2013) Graphene-multiwalled car-
bon nanotube-based nanofluids for improved heat dissipation.
RSC Adv 3:41994206
39. Kole M, Dey TK (2013) Investigation of thermal conductivity,
viscosity, and electrical conductivity of graphene based nanofl-
uids. J Appl Phys 113:084307 (8 pp)
40. Ganguly S, Sikdar S, Basu S (2009) Experimental investigation
of the effective electrical conductivity of aluminum oxide nano-
fluids. Powder Technol 196:326330
41. Hunter RJ (1981) Zeta potential in colloid science: principles and
applications. Academic Press, London
42. Lyklema J (2005) Fundamentals of interface and colloid science:
soft colloids. Elsevier, Amsterdam
43. Minea A, Luciu R (2012) Investigations on electrical conduc-
tivity of stabilized water based Al2O3 nanofluids. Microfluid
Nanofluid 13:977985
44. White SB, Shih AJ-M, Pipe KP (2011) Investigation of the
electrical conductivity of propylene glycol-based ZnO nanofluids.
Nanoscale Res Lett 6:346 (5 pp)
45. Wong K-FV, Kurma T (2008) Transport properties of alumina
nanofluids. Nanotechnology 19:345702 (8 pp)
5944 J Mater Sci (2014) 49:59345944
123
A glycerol--water-based nanofluid containing graphene oxide nanosheetsAbstractIntroductionExperimentalPreparation of the exfoliated graphite GONanofluid preparationCharacterization, thermal, and electrical conductivity measurements
Results and discussionFTIR, Raman spectra, and XRDMorphology, stability, and UV--visibleThermal conductivity of nanofluidElectrical conductivity of nanofluid
ConclusionAcknowledgementsReferences