Journal of Alloys and Compounds 502 (2010) 338–340
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Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Carbothermal reduction method for Fe
3
O
4
powder synthesis
Hua Wang
a
, Ping Hu
a
, De’an Pan
a
, Jianjun Tian
a
, Shengen Zhang
a,∗
, Alex A. Volinsky
b
a
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
b
Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA
article info
Article history:
Received 16 November 2009
Received in revised form 26 February 2010
Accepted 1 March 2010
Available online 6 March 2010
Keywords:
Carbothermal reduction
Fe3O4
Glucose
Fe2O3
abstract
This paper describes controlled synthesis of Fe
3
O
4
powder via carbothermal reduction method using
pure Fe
2
O
3
powder and glucose mixture as starting materials. Pure Fe
3
O
4
powders were produced when
glucose mole fraction was greater than 1/24. However, below 1/24 glucose mole fraction, only mixed
Fe
3
O
4
and Fe
2
O
3
powders were obtained. Glucose is the source of carbon and CO gas, both of react with
Fe
2
O
3
to form Fe
3
O
4
. At 1/24 glucose mole fraction the lowest carbon content in reaction products was
0.018%, which increased with the glucose mole fraction. Possible carbothermal reduction mechanisms
and Fe
3
O
4
powder magnetic properties were investigated. The carbothermal reduction method for Fe
3
O
4
synthesis has merits; it is not dangerous, controllable, and is suitable for large batch production, leading
to novel applications of Fe
3
O
4
powders.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
Magnetite (Fe
3
O
4
) with a cubic inverse spinel structure has
exhibited unique electric and magnetic properties based on the
transfer of electrons between Fe
2+
and Fe
3+
in the octahedral sites.
The study of Fe
3
O
4
has attracted intensive attention over the past
decades due to the potential applications in magnetic sensors
[1], high density magnetic recording media [2], printing ink [3],
ferrofluid [4], magnetic resonance imaging [5], catalysts [6] and
especially biomedical field [7,8], etc. Fe
3
O
4
powders, which are
non-toxic, have been extensively investigated. There have been
several methods reported to synthesize Fe
3
O
4
powders, including
co-precipitation [9], oxidation of Fe(OH)
2
by H
2
O
2
[10], microemul-
sion [11], hydrothermal synthesis [12], and sol–gel method [13],
etc.
The carbothermal reduction method is well known and widely
used in the industry to directly reduce iron [14]. The carbothermal
reduction route provides a general method for preparing ceramic
powders such as TiCN and AlN [15,16], but until now it has not
been utilized to prepare Fe
3
O
4
powders. In this study, we success-
fully synthesized Fe
3
O
4
powders from Fe
2
O
3
powder and glucose
mixture as starting materials using the carbothermal reduction
method. In addition, possible formation mechanisms and the prod-
uct magnetic properties were investigated.
∗
Corresponding author. Tel.: +86 10 6233 3375; fax: +86 10 6233 3375.
E-mail address: zhangshengen@mater.ustb.edu.cn (S. Zhang).
2. Experimental procedure
Fe2O3 powder was prepared by conventional spontaneous combustion method
using ferric nitrate (Fe(NO3)3·9H2O) and citric acid (C6H8O7·H2O) as raw materials.
Ferric nitrate (115.42 g) and citric acid (60.09 g) were dissolved in deionized water
(176 g), and the solution pH value was adjusted to 7.0 using NH3·H2O. The solution
was heated to 60
◦
C and continuously stirred using magnetic agitation. After 4 h,
the solution became a homogeneous yellow sol. Then the sol was dried at 120
◦
C
in the oven for 12 h and became a brown dry gel. Dry gel was ignited in air and
spontaneously combusted, producing loose, brown and very fine Fe2O3 powder,
identified as powder 1.
Glucose was mixed with powder 1. This mixture was labeled as powder 2.
Powder 2 with glucose mole fraction, P, 1/24, 1/18, 1/6 and 1/2 were used in experi-
ments. After drying, 1 g of powder 2 was heated to 650
◦
C for 2 h in the tube furnace
with argon atmosphere. After cooling to room temperature, the final products were
obtained and marked as powder 3.
X-ray powder diffraction (XRD) patterns were recorded using Philips APD-10
X-ray diffractometer with CuK radiation ( = 1.54187 Å). Samples carbon content
was measured using a Carbon/Sulfur analyzer (CS/444, LECO, USA). The magnetic
measurements were carried out in a vibrating sample magnetometer (LDJ 9600, LDJ
Electronics, USA).
3. Results and discussion
Dry gel spontaneous combustion can be described using the
following chemical reaction [17]:
Fe(NO
3
)
3
·9H
2
O + C
6
H
8
O
7
·H
2
O + NH
3
·H
2
O
→ Fe
2
O
3
+ CO
X
+ NO
X
+ H
2
O (1)
Fig. 1 shows an XRD pattern of the spontaneous combustion
product (powder 1), which exhibits good agreement with the stan-
dard Fe
2
O
3
powder pattern of JCPDS: 33-0664. This indicates that
the product consists of pure Fe
2
O
3
powder, as no obvious crystalline
impurity phases could be detected.
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.03.001