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Preparation and Optical Properties of Nickel Nanoparticles
Implanted Carbon Membranes
Disha Harinkhere1,a), K. K. Choudhary2 and Netram Kaurav1,b)
1Department of Physics, Holkar Science College, A-B Road, Indore
452001, India 2Army Cadet College, Indian Military Academy,
Dehradun - 248007 (UK), India.
a)Corresponding author:[email protected];
b)[email protected]
Abstract: Through dip coating method monodisperse nickel
nanoparticles assisted carbon membrane was prepared on porous
alumina disc support. The coating solution was prepared by blending
of thermally stable polymer polyphenylene oxide (PPO) and thermally
labile polymer polyvinylpyrrolidone (PVP) followed by addition of
nickel nanoparticles. Size of nanoparticles, surface porosity,
average pore size, element composition and optical properties of
the membrane were investigated by means of different techniques
such as XRD, FE-SEM, EDS and UV-Visible spectrometer Incorporation
of nano-sized nickel in polymer matrix causes increase in pore size
from 0.022 μm to 0.076 μm as well as porosity and decrease in
optical band gap from 5.44 eV to 5.09 eV of membrane.
Keywords: Nickel nanoparticles, Carbon membrane, Surface
morphology, Optical band gap.
INTRODUCTION
Porous inorganic membranes are used for separating suspensions,
mixtures and aerosols. They leave organic molecules, particles,
dissolved salts or even gases and liquids on one side and transfer
purified gases and liquids to the other. Thus, the membrane is a
semipermeable barrier that separates purified and concentrated
streams out of a mixture. Membrane has been used in a range of
industrial fields such as osmosis studies, uranium separation, fuel
cells, gas separation, food and beverage sectors, water and waste
water treatment, cosmetics and biotechnology [1].
Carbon membrane is one type of porous inorganic membrane which
offers advantages over polymeric membranes especially in terms of
selectivity as well as thermal and chemical stability [2].
Carbonization of a suitable polymeric membrane precursor under
controlled conditions produces carbon membrane. Blending of two
polymers with different thermal properties such as PPO/PVP,
PEI/PVP, PAN/PVP, polymide/PVP create a wide range of pore size
distribution (ultramicropore, micropore, macropore) and enhanced
gas permeability of membrane [3-7].
In 1962 Loeb and Sourirajan [8] proposed the idea of dividing a
membrane into a skin and a porous substructure, for polymer
membranes, boosted the development of a new generation of ceramic
membranes. In this new anisotropic membrane, the support layer
gives the mechanical strength and uninterrupted flux and the skin
layer determines the separation. As well as morphology of membrane
is key factor in membrane separation processes. The morphology of
membranes is closely related to the membranes’ pores. Pore size and
size distribution, interconnectivity and density (i.e. the number
of pores per unit area) are the physical parameters that affect
flux and separation efficiency.
Membrane characterization can be divided into physical and
chemical aspects. Generally we can say, the physical
characteristics of a membrane describe its morphology, mechanical
strength, pore structure and charge [9].On the other hand, chemical
characteristics depict membrane surface layer and its composition,
and are more appropriate for predicting a membrane’s behaviour
under different feeds and clearing up why the membrane works
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well (or not). Chemical characteristics facilitate us study the
complexity of the membrane surface and a number of micrometres into
the membrane depth. Physical features usually cover the whole
membrane structure from feed to permeate.
The topical membrane morphology involves mixed matrix membrane
which consists of two phases one is bulk phase and the other is
disperse phase such as metal, activated carbon, silica, zeolites or
nano-size particles. Addition of inorganic fillers results in
superior separation characteristics. Size of this inorganic filler
has influence on morphology as well as on the separation
performance of membrane. Smaller particle size provides more
interfacial area between bulk and disperse phase [10]. Use of
organic particles in nano range as the fillers offer advantages in
the preparation of the mixed matrix membrane [11].
Since some membrane materials such as Al2O3, TiO2 and ZrO2 were
oxides that could withstand harsh environments. As well as Ni
nanoparticles as fillers provide some advantages in preparation of
MMM’s or hybrid carbon membrane. Nickel is commonly used as
hydrogenation catalyst. Therefore in present work an anisotropic
carbon membrane has been prepared from polymeric membrane or
precursors at optimum conditions by using Al2O3 as porous support
in order to investigate the effect of substantial nickel
nanoparticles on the surface morphology as well as on the optical
properties of PVP/PPO blended carbon membrane.
EXPERIMENTAL
Materials
Porous alumina disk support with average pore size 0.14
micrometer and diameter of 23 mm was purchased from HI-Tech
Ceramics. Pure precursor materials of poly
(2,6-dimethyl-1,4-phenyleneoxide) powder, polyvinylpyrrolidone
(PVP, average molecular weight:40,000g/mol) powder,
Trioctylphosphene, Tech., 90%, Nickel(II) Acetylacetonate, 95%,
Olaylamine, Tech.,70% and ethanol were purchased from Sigma Aldrich
Co. The solvent chloroform was purchased from Merck.
Membranes preparation
Firstly nickel NPs were prepared by the thermal decomposition
method [12]. Fixed ratios of the polymer precursors with nano-sized
nickel were added to chloroform and stirred for 24 h to form
homogeneous casting solutions. Then the macroporous alumina disks
support was dip coated in coating solution for 15 s for 4 times to
acquire polymeric film of uniform thickness followed by drying of
all membranes for 24 h. Then to get rid of surplus solvent
resulting polymer membranes were pyrolyzed in a heating furnace at
240 ◦C for 6 h. Subsequent to remedial, the membranes were
pyrolyzed at 700 ◦C for 1 h. After attainment of room temperature,
the resultant carbon membranes were taken out from the furnace.
Characterizations
X-ray diffraction (D8 Advance X-ray Diffractometer, XRD) was
employ to verify the purity of the nickel particles. The
morphologies of the prepared membranes were investigated by field
emission scanning electron microscope (FESEM) instrument model JEOL
JSM-6500F. As well, X-ray spectroscopy (EDS or EDX) Oxford
instrument INCA, X-sight 7557 gave an elemental map of membrane
surface that combines topographical information with elemental
analysis and the optical properties were determined through Varian
Cary 100 Bio UV-Vis spectroscopy.
RESULTS AND DISCUSSIONS
Characterization of the nickel nanoparticles and the
membranes
The XRD spectra for nickel nanoparticles have shown in figure 1.
It is clear that three characteristic peaks for nickel (2θ=44.3,
51.6, 76.2), corresponding to Miller indices (111), (200) and (220)
are observed. The average particle size determined 8.9nm using
these peaks FWHM in the Debye-Scherrer relation. This relation can
be written as:
-
=
(1) Where D is the mean size of crystallites in nm, K is
crystallite shape factor a good approximation is 0.9, λ is the
X-ray wavelength (λ=1.54 Å for CuKα), β is the full width at
half the maximum (FWHM) in radians of the X-ray diffraction peak
and θ is the Braggs' angle in radian.
20 40 60 80 100
Inte
nsity
(a.u
.)
2
(111)
(200)
(220)
FIGURE 1.XRD pattern of the nickel nanoparticles
TABLE 1. Preparation of membranes with fixed proportion of
polymer blend (PPO/PVP) and Ni NP’s in chloroform:
Membrane
PPO Polymer
PVP Polymer
Ni NP’s
Concentration (wt%)
Weight(g) Concentration (wt%)
Weight(g) Concentration (wt%)
Weight(g)
PPO/PVP 7.5 1.5 2.5 0.5 - -
PPO/PVP/Ni 6.5 1.3 2.5 0.5 1 0.2 Figure 2(a) and 2(c) depicts
FE-SEM images of the prepared carbon membrane while the figure 2(b)
and 2(d) is
treated images of adjoining figures. These images were treated
by the public domain images processing and analysis program NIH
Image [13]. It has been analysed that PPO/PVP Carbon membrane is
0.344% porous and the average pore size is 0.022 μm whereas Ni NP’s
assisted Carbon is 0.498% porous and the average pore size is 0.076
μm. This study showed that PPO/PVP Carbon membrane has smaller pore
size than PPO/PVP/Ni carbon membrane. This may be due to different
polymeric concentration in casting solution. As listed in table 1
that 1wt% nickel added instead of PPO polymer in PPO/PVP/Ni
membrane while total weight% of solvents is fixed to 10 wt% in
solution. Some articles have been showed effect of polymeric
concentration on membrane morphology. Ismail et al. prepared
polyetherimide hollow fiber membranes and observed that as the
polymer concentration increased the mean pore size, surface
porosity and void fraction of membranes decreased [14].
EDX Analysis:
As shown in figure 3(a) and 3(b), EDX analysis indicates the
presence of nickel element the polymeric layer. Table 2 shows the
analysis results of membrane. Content of nickel is around 10.7
wt%.
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TABLE 2. Element composition of Nickel nanoparticles assisted
Carbon Membranes formed by the polymeric solution containing 1 wt%
Ni np’s analyzed by EDX
Element Weight % Atomic % Al 57.2 49.2 O 32.1 46.6 Ni 10.7
4.2
Total 100 100
FIGURE 2(a). Original image with of membrane surface with
no disperse phase FIGURE 2(b). Treated image of membrane
surface
FIGURE 2(c). Original image of membrane surface with disperse
phase
FIGURE 2(d). Treated image of membrane surface
Optical properties of the membranes
Figure 4(a) and figure 4(b) show reflection and absorption
spectra respectively. Reflection spectra display that alumina disc
(without coating) and PVP/PPO membrane have almost same
reflectivity while PPO/PVP/Ni membrane is less reflective. In UV
region reflection is increasing quickly as in visible region slowly
for alumina disc and membranes. Whereas in absorption spectra,
Alumina disc and PPO/PVP membrane are less absorptive although
nickel assisted membrane is more absorptive. That is presence of
nickel in membrane influences the optical
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behaviour of the membrane. Optical band gap was determined using
Kubelka–Munk function. This function can be written as:
( ) = ( ) = (2)
Where R is reflectance of the material, K molar absorption
coefficient and S is scattering factor. As shown in figure 5
optical band gap for PPO/PVP membrane is 5.44 eV whereas for
PPO/PVP/Ni membrane 5.09 eV. This analysis showed that due to
presence of nickel there is drop off in band gap of membrane this
may be due to incorporation of nickel in polymer membrane formulate
conduction chain.
FIGURE 3(a).Original image of membrane surface with disperse
phase
FIGURE 3(b).EDX result
200 400 600 800 1000 120010
20
30
40
50
60
70
80
90
100
110
Wavelength (nm)
R%
Baseline Alumina disc PPO/PVP PPO/PVP/Ni
200 400 600 800 1000 12000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Abs
orba
nce
Wavelength (nm)
Alumina disc PPO/PVP PPO/PVP/Ni
FIGURE 4(a) Reflection Spectra FIGURE 4(b) Absorption
spectra
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1 2 3 4 5 6 70
102030405060708090
100110120
(F(R
)hv)
^2
Energy (eV)
PPO/PVP PPO/PVP/Ni
FIGURE 5 Band Gap Calculations Of Membranes Using DRS Data
CONCLUSION
Carbon membranes were prepared on porous alumina disc support by
dip coating in polymeric solution. Surface study showed that nickel
assisted membrane has larger pore size as well as more porous than
PPO/PVP membrane due to change in polymer concentration in casting
solution. Also the investigation of optical properties revealed
that due to the addition of nickel in polymeric matrix there is
decrease in optical band gap from 5.44 eV to 5.09 eV of
membrane.
ACKNOWLEDGMENTS
The financial support from the UGC-DAE Consortium for Scientific
Research, Indore under the CRS projects is thankfully
acknowledged.
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INTRODUCTIONEXPERIMENTALMaterialsMembranes
preparationCharacterizations
RESULTS AND DISCUSSIONSCharacterization of the nickel
nanoparticles and the membranesEDX Analysis:Optical properties of
the membranes
//CONCLUSIONACKNOWLEDGMENTSREFERENCES