Open Science Journal of Modern Physics 2014; 1(5): 37-43
Published online January 20, 2015 (http://www.openscienceonline.com/journal/osjmp)
Synthesis of multi core-shell nanocomposite of MnFe2O4-multi-walled carbon nanotube based polypyrrole and investigation radar absorbing properties
S. Hossein Hosseini1, *
, N. Arjmand2, M. Shirazi Madani
2
1Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran, Iran
2Department of Chemistry, Faculty of Technical and Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran
Email address
[email protected] (S. H. Hosseini)
To cite this article S. Hossein Hosseini, N. Arjmand, M. Shirazi Madani. Synthesis of Multi Core-Shell Nanocomposite of MnFe2O4-Multi-Walled Carbon
Nanotube Based Polypyrrole and Investigation Radar Absorbing Properties. Open Science Journal of Modern Physics.
Vol. 1, No. 5, 2014, pp. 37-43.
Abstract
The synthesis of multi-walled carbon nanotube of polypyrrole (PPy) composites that functionalized by MnFe2O4
nanoparticles (MWCNTS/MnFe2O4/PPy) were reported. The novel procedure relies on a two-step synthesis method. The
prime step includes synthesis of mono-dispersed MnFe2O4 nanoparticles (NPS) nested on the surface of carboxylated
MWNTS. The second step deals with the newly formed nanocomposite decorated by a PPy layer via in situ polymerization
with multi core-shell structure. SEM and TEM images indicated that the obtained samples have the morphologies of
nanotubes. Further to this the TEM images and selected area electronic diffractions showed that MnFe2O4 NPs and
MWCNT were embedded in PPy. The molecular structure and composition of MWCNTS/MnFe2O4/PPy nanocomposites
were characterized by fourier transform infrared spectra (FTIR) and UV-Vis spectra. The results of XRD confirmed the
formation of MWCNT/MnFe2O4/PPy nanocomposites and hence confirmed ordered structure of NPs. As a multifunctional
material, some physical properties of MWCNT/MnFe2O4/PPy nanocomposites were also investigated. As prepared
conducting ferromagnetic polymer nanocomposites have electrical conductivity of the order of 0.5 S/cm and saturation
magnetization (Ms) value of 0.06 emu/g. Microwave absorbing properties of the nanocomposite were investigated by using
vector network analyzers in the frequency range of 8–16 GHz. The values of the minimum reflection loss were -30 dB in the
frequency of 11.6 GHz for MWCNT/MnFe2O4/PPy core/shell nanocomposite with a thickness of 1.5 mm and 60wt%
MWCNTs/MnFe2O4 as core. These include; electrical conductivity by means of using four probe method and magnetic
property via VSM and AFM techniques.
Keywords
Multi-Walled Carbon Nanotube, MnFe2O4, Polypyrrole, Nanocomposite, Radar Absorbing Materials
1. Introduction
Carbon nanotubes (CNTs) are high aspect ratio allotropes
of carbon. They have unique physical and chemical
characteristics. CNTs walls are not reactive, however, their
fullerene-like tips are known to be rather reactive. In this
view, end functionalization of CNTs is often used to
relatively generate functional groups (e.g., COOH, OH, or
C=O). Like in fullerenes reactivity is activated by curvature
effects. Curvature in nanotubes is much smaller than in
conventional fullerenes. This is owing to the facts that: (a)
the tube diameters are generally larger and, (b) they are
curved in one direction only. Generally nanomaterials enjoy
exceptional properties [1] which make them appropriate for
38 S. Hossein Hosseini et al.: Synthesis of Multi Core-Shell Nanocomposite of MnFe2O4-Multi-Walled Carbon Nanotube Based
Polypyrrole and Investigation Radar Absorbing Properties
many novel applications. Herein, CNTs have very interesting
physicochemical properties such as: ordered structure with
high aspect ratio, Ultra light weight, high mechanical
strength, high electrical conductivity, high thermal
conductivity, metallic or semi-metallic behavior and high
surface area. The combinations of these characteristics make
CNT a unique material with the potential for diverse
applications. A wide range of applications has been
envisaged for CNTs ranging from sensors for the detection of
genetic or other molecular abnormalities, to substrates
cellular growth for tissue regeneration and the use of CNT as
substrates for neuronal growth [2], delivery systems [3] and
radar absorbing materials [4].
Radar absorbing materials can be classified in two broad
categories, either dielectric or magnetic absorbers [5].
Dielectric absorbers depend on the ohmic loss of energy that
can be achieved by loading loss fillers like carbon, graphite,
conducting polymers or metal particles/powder into a
polymeric matrix. Among the dielectric properties can be
cited the dielectric constant and the loss tangent. Magnetic
absorbers depend on the magnetic hysteresis effect, which is
obtained when particles like ferrites are filled into a
polymeric matrix [6,7].
Xu, introduced phenylamine groups (–C6H4–NH2) the
monomers of polyaniline on the surface of MWNTs
(designated as p-MWNTs) by using an effective chemical
route and HCl doped PANI was chemically grafted onto
phenylamine groups containing MWNTs by in situ oxidation
polymerization [8]. Lee and coworkers reported a new
strategy for the synthesis of hybrid nanocomposites
consisting of MWCNTs functionalized with PANI
(MWCNTs-f-PANI) and noble metal (Au and Ag)
nanoparticles. The synthesized hybrid composites possessed
high conductivity [9]. In the other work, Zhang showed that a
microwave hydrothermal strategy has been employed to
functionalize acid-treated CNTs with a thorn like
organometallic, the methyl orange–iron (III) chloride (MO–
FeCl3) complex. This complex could serve as both
morphology guiding agent and oxidant, thereby polypyrrole
nanoparticles could be attached directionally on CNTs by the
polymerization of pyrrole in the absence of extra oxidants
[10]. In the preceding works, we have synthesized some of
conducting and magnetic nanocomposites and investigated
the corresponding applications [11-14].
In this paper, we reported a facile method to prepare
MWCNTs/MnFe2O4 NPs/PPy composite nanotubes in two
steps. The first step deals with the synthesis of nearly mono
dispersed MnFe2O4 NPs on the surface of MWCNTs by in
situ method to achieve fine morphology without MnFe2O4
NPs aggregates even at a high weight ratio of MnFe2O4 NPs.
The second step includes decorating the nanocomposites with
PPy via in situ polymerization with multi core-shell structure.
TEM images showed that the MWCNTs/MnFe2O4 NPs
nanotubes were coated with a thin PPy layer.
2. Experimental
2.1. Materials
Functionalized MWCNT (diameters: 10-20 nm, purity:
95%) used in this work were purchased from neutrino. port.
Co, (China). Other reagents were analytical grade and used
without further purification including FeCl3.6H2O,
MnCl2.2H2O, NaOH and pyrrole (Py) monomer that was
distilled under reduced pressure and stored below 0°C before
use. Dodecylbenzenesulfonic acid (DBSA) was of industrial
grade.
2.2. In Situ Synthesis of MWCNTs/MnFe2O4
Nanotubes
50 mg of functionalized MWCNTS were dissolved in 30
ml aqueous alcohol by ultrasonic irradiation for 30 min. Then
added 150 ml of NaOH aqueous solution and mixture was
sonicated for 30 min. The sample was filtered, washed with
enough distilled water and dried. The obtained powder mixed
with 50 ml (0.5 M) of FeCl3.6H2O and 50 ml (0.25 M)
MnCl2.2H2O and sonicated in an ultrasonic bath for 30 min.
The mixture was stirred vigorously for 1 h using a
mechanical stirrer (2000 rpm). Subsequently 200 ml (1M) of
the NaOH aqueous solution syringed rapidly into reaction
container while continue stirring for 2 h. The whole process
proceeded under N2 atmosphere. The reaction mixture was
then centrifuged, washed with distilled water and dried at
50°C for 24 h.
2.3. Synthesis of MWCNTS/MnFe2O4/PPy
Nanocomposite
300 mg of MWCN/MnFe2O4nanocomposite were
dissolved in 15 ml of NaOH (0.5 M) aqueous solution and
pH value was adjusted to 8-9 by adding distilled water and it
was stirred homogeneously for 30 min. Then 1.62 g
FeCl3.6H2O dissolved in 20 ml of distilled water and added
to the reaction mixture. Subsequently 0.2 ml of the Py
monomer and 0.5 ml DBSA was syringed into reaction
container. The reaction mixture was stirred at room
temperature using magnetic stirrer for 24 h. Finally mixture
was filtered, washed with distilled water and dried at room
temperature.
3. Results and Discussion
This work describes a novel route for preparing novel
MWCNTs/MnFe2O4 and MWCNTs/MnFe2O4/PPy
conducting magnetic core shell nanoparticles (Figures 1 and
2), by pursuing a combination of two step procedure
including; single step co-precipitation method and in-situ
polymerization. Morphology, conductivity, X-ray diffraction
(XRD) characterizations, magnetic and microwave
absorption properties of nanocomposites were investigated in
this communication.
Open Science Journal of Modern Physics 2014; 1(5): 37-43 39
Figure 1. Schematic for route synthesis of MWCNTs/MnFe2O4
Figure 2. Schematic for route synthesis of MWCNTs/MnFe2O4/PPy nanotube
3.1. XRD Patterns of MWCNTs/MnFe2O4
The XRD pattern of the as-prepared MWCNTs/MnFe2O4
is shown in Figure 3. The analysis of the results indicates that
the product is composed of a single phase: cubic MnFe2O4
(JCPDS card no 00-002-0896) and MWCNTs (JCPDS card
no 049-1719). The diffractions 2θ =32.94, 35.50, 45.20,
55.50, 64.21, 66.11° and 2θ =23.18, 38.60
° could be ascribed
to the reflections of MnFe2O4 and MWCNTs, respectively.
The other peaks related to Fe2O3. The XRD peak with a
maximum at 2θ =32.94° may be ascribed to the diffraction
peak of MnFe2O4. The average size of the MnFe2O4
crystalline calculated using the scherrer’s formula is about
38.18 nm.
Figure 3. The XRD pattern of MWCNTs/ MnFe2O4
3.2. Analysis of the Magnetic Properties
MWCNTs/MnFe2O4/PPy
a
b
40 S. Hossein Hosseini et al.: Synthesis of Multi Core-Shell Nanocomposite of MnFe2O4-Multi-Walled Carbon Nanotube Based
Polypyrrole and Investigation Radar Absorbing Properties
c
Figure 4. The VSM curve of a) MnFe2O4, b) MWCNTs/MnFe2O4 and c)
MWCNTs/MnFe2O4/PPy
The magnetic properties of the MWCNTs/MnFe2O4/PPy
nanocomposites were investigated by vibrating sample
magnetometer (VSM). Figure 4(a-c) show clear saturation
between -10≤H≤10 kOe, magnetization curves measured at
room temperature for 4a) MnFe2O4, 4b) MWCNTs/MnFe2O4
and 4c) MWCNTs/MnFe2O4/PPy. Figure 4a shows clear
saturation magnetization (Ms) about 60emu/g. The values of
remnant magnetization (Mr) and the coercivity field (Hc) for
MnFe2O4 nanocomposite were reported approximately
18emu/g and 140Oe, respectively. The lack of hysteresis
loops indicates that the super paramagnetic nature of the
MWCNTs/MnFe2O4 NPs is specified by a MS=1.6 emu/g and
Mr is 0.6 emu/g and HC is 65Oe, Figure 4b. This indicates
that the MWCNTs core and MnFe2O4 first shell contact
intimately. Ms, Mr and Hc decreased by increasing MWCNT.
Figure 4c shows clear magnetic properties of
MWCNTs/MnFe2O4/PPy nanocomposite. In this Figure, Ms,
Mr and Hc for the MWCNTs/MnFe2O4/PPy nanocomposite
were measured 0.06, 0.005 emu/g and 200 Oe. The changes
in Ms and the Hc can be attributed to the existence of
MnFe2O4 NPs on the surface of MWCNTs, which can be
resulted in the polar interaction at the interface of two phases.
The magnetization curve of the sample shows weak
ferromagnetic behavior, with slender hysteresis. Magnetic
properties of nanocomposites containing magnetite or ferrite
particles are believed to be highly dependent on the sample
shape, crystallinity, and the value of magnetic particles, so
that they can be adjusted to obtain optimum magnetic
property.
3.3. FTIR Spectra
Figure5(a-c) shows the characteristic peaks of a) MnFe2O4,
b) MWCNTs/MnFe2O4 and c) MWCNTs/MnFe2O4/PPy
nanocomposites. In spectrum (Figure5a), the IR bands at
578.13 and 400 cm-1
were assigned to stretching vibrations of
the Mn-O and Fe-O bonds, respectively. The OH stretching,
carbonyl stretching vibration, C-C-O and Mn-O stretching in
modified MWCNTs/MnFe2O4 were attributed at 3430, 1639,
1124 and 577 cm-1
, respectively. It was showed in Figure 5b.
In this spectrum, the peak at 570.22 cm-1
is attributed to
stretching vibration of the Mn-O bond. It can be seen that one
absorption peak is corresponding to the characteristic peak at
the end of the nanotube’s rings (707 cm
-1) resembling the =C-
H out-of-plane deformation vibration. In Figure 5c shows the
characteristic peaks of MWCNTs/MnFe2O4/PPy
nanocomposites. The strong peaks at 580 and 1037 cm-1
typical signal could be attributed to Mn-O and C-N
vibrational stretching. Peaks at 1161 and 1292 cm-1
are
attributed to the C-H in-plane vibration, whereas peak 668
cm-1
is attributed to the C-H out-plane bend. The peaks at
1541 and 1400 cm-1
are attributed to the characteristic C=C
stretching of the pyrrole ring. The MWCNTs/MnFe2O4/PPy
can be clearly showed the characteristic peaks for Mn,
MWCNTs and PPy. The peaks of vibrational stretching for
C=O, C-H and N-H groups were showed at1653, 2918 and
3428 cm-1
. The =C-H out-of-plane deformation vibration for
the nanotube’s rings shows in 815 cm
-1, too.
a
Open Science Journal of Modern Physics 2014; 1(5): 37-43 41
b
c
Figure 5. FTIR spectra of a) MnFe2O4, b) MWCNTs/MnFe2O4 and c) MWCNTs/MnFe2O4/PPy nanocomposite
3.4. Morphology of MWCNTs/MnFe2O4 and
MWCNTs/MnFe2O4/PPy
The SEM images of resulting MWCNTs,
MWCNTs/MnFe2O4 and MWCNTs/MnFe2O4/PPy are
referred in Figure 6(a-c). A typical nanostructure MWCNTs
that is a spaghetti-like morphology is depicted in Figure 6a.
This figure represents a typical SEM image of pure
MWCNTs with an average diameter of 30-50 nm. Figure 6b
exhibits the surface morphology of the MnFe2O4/MWCNTs
core-shell nanocomposite in which the MWCNTs outer
surfaces are decorated by MnFe2O4. From Figure 6c the
nanofiber size of MWCNTs/MnFe2O4/PPy is determined in
the range 50-700 nm with rod morphology.
a
42 S. Hossein Hosseini et al.: Synthesis of Multi Core-Shell Nanocomposite of MnFe2O4-Multi-Walled Carbon Nanotube Based
Polypyrrole and Investigation Radar Absorbing Properties
b
c
Figure 6. SEM images of (a) pure MWCNTs, (b) MWCNTs/MnFe2O4, and (c)
MWCNTs/MnFe2O4
3.5. Conductivity
Electrically conductivity of samples at room temperature
was measured by four probe method. When the PPy was re-
doped by DBSA, the conductivity was improved from 10 to
45 S/cm, suggesting that doping H+ increased conductivity of
PPy. The conductivity of MWCNT was decreased from 88 to
5 S/cm by addition of MnFe2O4. Then electrical
conductivities were increased by addition of PPy as final
shell in nanocomposites. The conductivities of
MWCNTs/MnFe2O4/PPy nanocomposites are 0.5, 0.04 and
0.0034 S/cm for 20, 40 and 60 wt% MWCNTs/MnFe2O4 as
core, respectively.
3.6. Investigation of Radar Absorbing
Properties
Nanocomposites were prepared by in situ polymerization
of PPy with MnFe2O4/MWCNTs as multi core-shell structure.
Then, the mixture was pasted on metal plate with the area of
40mm×40mm as the test plate by dip coating method. The
radar absorbing properties of the nanocomposite with the
coating thickness of 1.5 mm were investigated by using a HP
8720B vector network analyzer and standard horn antennas
in anechoic chamber in the frequency range of 8–16 GHz.
For the confirmation of microwave absorption capability
of MWCNTs/MnFe2O4/PPy nanocomposites, the reflection
loss (RL) was measured in 8–16 GHz, which is revealed in
Figure 7. This Figure shows the microwave absorption
behavior of the MWCNTs/MnFe2O4/PPy nanocomposite in
different weight ratios. For MWCNTs/MnFe2O4/PPy
nanocomposites, the RL values were obtained less than -25
dB in the frequency of 10.8 GHz, -30 dB in the frequency of
11.6 GHz and -20 dB in the frequency of 14 GHz for 20, 40
and 60wt% MWCNTs/MnFe2O4 as core, respectively. The
MWCNTs/MnFe2O4/PPy nanocomposites (weight ratio: 40%)
exhibits good absorption property at 1.5 mm. The minimum
RL value reaches -30 dB at 11.6 GHz. In the other weight
ratios (20 and 60 wt%).
Figure 7. Reflection loss of frequency of MWCNTs/MnFe2O4/PPy
nanocomposites for a) 20, b) 40 and c) 60wt% MWCNTs/MnFe2O4 as core.
4. Conclusions
In summary, we have described a facile chemical approach
to synthesize magnetic and conductive multi core-shell
nanocomposite of MnFe2O4/MWCNTs with PPy.
The conducting MWCNTs/MnFe2O4 nanocomposite can
be fabricated by in situ polymerization of pyrrole. SEM
images confirmed the core-shell nanostructure and the
attachment of MnFe2O4 NPs on the surface of MWCNTs.
FTIR and XRD spectra were used to characterize the
molecular structure of nanocomposite. The magnetization
measurements proved that the samples are conductive and
have a super paramagnetic behavior. The results may be used
for super capacitors and actuators. For
MnFe2O4/MWCNTs/PPy multi core–shell nanocomposite
with the coating thickness of 1.5 mm, the minimum RL
values less than -30 dB were obtained in the frequency of X-
band. The introduction of PPy improved the absorbing
properties, which was due to the dielectric loss of PPy. Such
strong absorption is attributed to better electromagnetic
matching due to the existence of PPy and the special
core/shell structure. Therefore, the prepared composites have
potential applications in EMI shielding.
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