Production of Iron Disulfide Nanoparticles by Hydrothermal Process

Int. J. Nanosci. Nanotechnol., Vol. 6, No. 4, Dec. 2010, pp. 231-235
Production of Iron Disulfide Nanoparticles by Hydrothermal Process
S. Mohammadkhani, M. Aghaziarati
Faculty of Chemistry and Chemical Engineering, Malek Ashtar University of Technology, Lavizan,
Tehran, I. R. Iran
(*) Corresponding author: maziarati@mut.ac.ir
(Received: 05 Oct. 2010 and Accepted: 28 Nov. 2010)
Abstract:
In this research, a single-stage low-temperature hydrothermal synthesis route was successfully developed
for preparation of Iron Disulfide. The prepared powder was characterized by X-ray diffraction (XRD) and
scanning electron microscopy (SEM). These analyses showed that nanoparticles were well crystallized, pyrite
was the main product and the shape of crystals was nanorod. Also, the influences of reaction temperature and
iron source on the formation of the target compound were investigated.
Keywords: Iron Disulfide, nanoparticles, hydrothermal process, Pyrite
1. INTRODUCTION
Iron Disulfide (FeS2) is a semiconductor with
a suitable energy band gap (Eg≈0.95 eV) and
a very high optical absorption coefficient (α≈
5×105 cm-1 for λ<750 nm) which is two orders of
magnitude higher than that of crystalline silicon
[1, 2]. Therefore, Iron Disulfide has been receiving
growing attention because of its promising potential
for application as an optoelectronic or photovoltaic
material. Furthermore, FeS2 as an appealing cathode
material for thermal batteries, demonstrates plenty
of unique features, such as very high capacity, low
environmental impact (nontoxic elements with
respect to Fe and S), and affordable cost (abundant
and cheap).
Several methods have been applied for preparation
of Iron Disulfide, such as: thermal sulfuration
[3–7]; mechanical milling [8–12], wet chemical
route [13] and solvothermal process [14–18]. In the
last few years, attention has been shifted towards
the synthesis of one-dimensional nanostructure
materials because of their fundamental importance
as well as wide range of potential applications in
nanodevices. Therefore, it is necessary to design a
low-temperature synthesis route for solving these
problems. Recently, the hydrothermal process by
attractive traits, for instance, simple operation and
low temperature has opened a fruitful route for
synthesis of advanced inorganic materials such as
Iron Disulfide.
In previous studies, reaction system was a small
impeller-free reservoir. While in this research, a
reactor equipped with impeller was used. Also, this
paper discusses the effects of reaction temperature
and iron source on formation of FeS2 powder.
2. EXPERIMENTAL
All reagents were of analytical grade and were used
without further purification. In a typical process,
Na2S2O3 (13.16 g), either FeSO4.7H2O (23.15 g) or
Fe(NO3)3.9H2O (33.63 g) were used as the starting
materials. Iron and sulfur sources were separately
231
y using Debby--Sherrer equaation.
dissolved in deionized water and stirred with
magnetic stirrer. After their complete dissolution,
they were mixed and transferred into a stainless
steel autoclave with 2 litter capacity and filled
with distilled water up to 40% of the total volume.
The autoclave was sealed and maintained at a
temperature in the range of 130–180˚C for a period
of 2 to 8 h. It was then cooled to room temperature
naturally. The precipitates were filtered and washed
with distilled water and then Carbon disulfide to
remove the residual impurities. After being dried at
80˚C for 4 h, the black powders were collected for
characterization.
a
b
2
The obtained samples were characterized by SEM
and XRD to determine the structure and composition,
respectively. SEM images were taken by a VEGA\\
TESCAN scanning electron microscope. The XRD
analysis was carried out by an X-ray diffractometer.
3. RESULTS AND DISCUSSION
3.1. Effect of reaction temperature
c
In order to study effect of reaction temperature,
the process was performed at various temperatures
for 6 hr by using FeSO4.7H2O and Na2S2O3 as the
initial materials. Figure 1 shows the SEM images
of synthesized powder at different temperatures.
It is observed that particles are in nanorod-like
morphologies at all temperatures. Moreover,
this figure indicates that increasing the reaction
temperature will reduce the particles size.
FeS2 can be crystallized not only as a cubic pyrite
structure but also as an orthorhombic metastable
marcasite structure which is detrimental to
photovoltaic applications because of its low band gap
(Eg = 0.34 eV). Therefore, it is better to perform the
process at a temperature in which FeS2 is produced
without or with small amount of marcasite.
Figure 2 shows the XRD patterns of FeS2 prepared
by Na2S2O3 (13.16 g) and FeSO4.7H2O (23.15 g) at
C and (c) 180
Fig. 1. SEM
S
images of prepared FeS
F 2 at (a) 1300C, (b) 150C
0 Cand 180˚C after 6 hrs of reaction. The peaks
150
of pyrite and marcasite are seen in XRD patterns.
Figure 1: SEM images of prepared FeS2 at
However, intensities of marcasite’s peaks have
(a) 130˚C, (b) 150˚C and (c) 180˚C
decreased at higher temperature. In other words,
232
Mohammadkhani and Aghaziarati
d
C and (c) 1800 C
Fig. 1. SEM images of prepared FeS
F 2 at (a) 1300C, (b) 150C
Fig. 2. XRD patteerns of preparred FeS2 at (aa)150 C and ((b)180C for 6h (p:pyrite, m:marcasite))
3.2. Effect of iron source
Fe (NO3)3.9H2O was used
u
instead of
o FeSO4.7H2O to investiigate the effeect of iron souurce. Fig. 3 sshows
XRD patterns of FeS2 prepared by Na
N 2S2O3 (13.16 g) and Fee (NO3)3.9H2O (33.63 g) aat 160C afterr 6 hrs
of reaction
n. XRD patteerns reveal th
hat the preparred product ccontains pyritte and sulfur. This figure sshows
that sulfurr is the majorr product. Fu
urthermore, weight
w
of prodduct was mucch less than thhat of the preevious
case (FeSO
O4.7H2O as irron source).
Fig. 4 ind
dicates SEM images of FeeS2 prepared by Na2S2O3 (13.16 g) annd Fe (NO3)3..9H2O (33.633 g) at
160C aftter 6 hrs of reaction.
r
It deemonstrates that
t
obtained
3 d particles aree microparticcle with 2-3 μm in
(p:pyrite,
Fig.
XRD
ofofprepar
red FeS
and
((b)180C
fora 6h
m:marcasite)
)
Figure
XRDpatte
patterns
prepared
FeS2itt2atseems
at(aa)150
(a)150
and
(b)180˚C
6h
(p:pyrite,
m:marcasite)
length
and
d2.2:
400-500
nm
m erns
in diameter.
Therefore,
thatC
F
Fe˚C
(NO
suita
able
iron sour
rce.
3)3.9H
2 O isn't for
3.2. Effect of iron source
Fe (NO3)3.9H2O was used
u
instead of
o FeSO4.7H2O to investiigate the effeect of iron souurce. Fig. 3 sshows
XRD patterns of FeS2 prepared by Na
N 2S2O3 (13.16 g) and Fee (NO3)3.9H2O (33.63 g) aat 160C afterr 6 hrs
of reaction
n. XRD patteerns reveal th
hat the preparred product ccontains pyritte and sulfur. This figure sshows
that sulfurr is the majorr product. Fu
urthermore, weight
w
of prodduct was mucch less than thhat of the preevious
case (FeSO
O4.7H2O as irron source).
Fig. 4 ind
dicates SEM images of FeeS2 prepared by Na2S2O3 (13.16 g) annd Fe (NO3)3..9H2O (33.633 g) at
160C aftter 6 hrs of reaction.
r
It deemonstrates that
t
obtainedd particles aree microparticcle with 2-3 μm in
length and
d 400-500 nm
m in diameter. Therefore, itt seems that F
Fe (NO3)3.9H2O isn't a suitaable iron sourrce.
Fig
g. 3. XRD pattterns of prepared FeS2 by Fe (NO3)3.9H
H2O at 160C for 6h (p:pyrrite,s:sulfur)
Figure 3: XRD patterns of prepared FeS2 by Fe (NO3)3.9H2O at 160˚C for 6h (p:pyrite,s:sulfur)
International Journal of Nanoscience and Nanotechnology
4
233
it seems that Fe(NO3)3.9H2O isn’t a suitable iron
source.
5. CONCLUSIONS
Pyrite was successfully synthesized by hydrothermal
method using FeSO4.7H2O or Fe(NO3)3.9H2O and
Na2S2O3 as raw materials in temperature range of
130–180˚C. It was found that higher temperatures
produce pyrite with better quality (smaller size
and higher purity). Also, it was shown that
Fe(NO3)3.9H2O shouldn’t use as the iron source.
Ultimately, results indicated that in optimum
condition (temperature=180˚C, using FeSO4.7H2O
and Na2S2O3) FeS2 was obtained as nanorod with
the lowest amount of marcasite.
Fig. 4.. SEM imagess of prepared FeS2 by Fe (N
NO3)3.9H2O at 160C for 66h
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Figure 4: SEM images of prepared FeS2 by
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