Preparation and characterization of rod-shaped MnO2 crystal

Article abstract of DOI:10.1016/j.ssc.2004.10.003

Rod-shaped MnO₂ crystal was synthesized by a new route, the sample was a multicrystal with the mixture of α- and γ-MnO ₂. From TEM results, it could be seen that the sample has a length of 250-350 nm and a diameter of 15-25 nm. The ratio of length to the diameter could reach more than 15:1. In the preparation process, the KMnO₄ was used as oxidant and MnCl₂ was the manganese source. The polyethylene glycol (PG) was added as the dispersant and the high molecular weight polyacrylamide (PAM) was introduced at the same time. When the reaction finished, the product was treated with steam for 3 h and then the rodshaped MnO₂ crystal was obtained. The crystal was characterized by X-ray diffraction (XRD), electron diffraction (ED), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM).

Full text of DOI:10.1016/j.ssc.2004.10.003

Solid State Communications 133 (2005) 121–123
www.elsevier.com/locate/ssc
Preparation and characterization of rod-shaped MnO crystal
2
*
Chen Ye , Zhang Mi Lin, Jing Xiao Yan
School of Chemical Engineering, Harbin Engineering University, No. 145 Nantong Street, Nangang District,
Harbin Hei Longjiang 150001, China
Received 19 May 2004; accepted 5 October 2004 by T.T.M. Palstra
Available online 14 October 2004
Abstract
Rod-shaped MnO
2
2
crystal was synthesized by a new route, the sample was a multicrystal with the mixture of a- and g-MnO .
From TEM results, it could be seen that the sample has a length of 250–350 nm and a diameter of 15–25 nm. The ratio of length
to the diameter could reach more than 15:1. In the preparation process, the KMnO was used as oxidant and MnCl was the
4
2
manganese source. The polyethylene glycol (PG) was added as the dispersant and the high molecular weight polyacrylamide
PAM) was introduced at the same time. When the reaction finished, the product was treated with steam for 3 h and then the rod-
shaped MnO crystal was obtained. The crystal was characterized by X-ray diffraction (XRD), electron diffraction (ED),
(
2
transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and scanning electron
microscopy (SEM).
q 2004 Elsevier Ltd. All rights reserved.
PACS: 81.05
Keywords: A. Crystal; A. Nanostructure; C. Transmission electron microscopy; D. Chemical synthesis; D. X-ray diffraction
1
. Introduction
mixture of several phases at low temperature (500 8C) and
Mn would be obtained at high temperature (800 8C).
Furthermore if MnO was prepared by some common
2 3
O
Tetravalent manganese oxide (MnO
2
) is one of the most
2
promising material in many technological applications [1–
]. For its high positive electrode potential and relative low
molecular weight, MnO successfully act as the electrode in
high energy density lithium batteries [4] and supercapacitors
5]. So many researches have focused on the preparation and
characterization of MnO [6–8]. However, electrochemical
methods, the particles with irregular shapes would be
obtained [12]. Recently though some routes were used to
3
synthesize single phased MnO
required strict conditions. Rossouw et al. [12] synthesized a-
MnO phase by sulfuric acid treatment of Li MnO and later
Muraoka et al. [13] have reported that a-MnO was prepared
by starting from the hollandite-type (NH Mn 16, the
residual precursors are confined to obtain high purity and
well crystalline MnO . Xiong et.al. [14] prepared g-MnO
2
, they are often limited by the
2
[
2
2
3
2
2
4
)
x
8
O
properties of nanostructured crystalline MnO
depend on its dimensionality, powder morophology, crystal-
line structure and bulk density [6]. MnO is known to exist a
wide variety of crystal structure forms, e.g. a-, b-, g-, 3- and
d-MnO [9–11]. When MnO was obtained by thermal
treatment of some manganese precursors, it is often the
2
strongly
2
2
2
by a hydrothermal chemical reaction of a coordination
polymer in NaOH solution, but the selection of appropriate
coordination polymer precursors is a crucial problem.
2
2
2
In this paper the rod-shaped MnO crystal was
synthesized by a novel way and demonstrated by the results
of XRD and TEM. During the process, MnO was obtained
2
*
Corresponding author. Tel.: C86 451 82519613; fax: C86 451
2533026.
E-mail address: chenye@vip.0451.com (C. Ye).
8
by redox between KMnO and MnCl under high viscosity.
4
2
The method has not been reported yet.
0038-1098/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ssc.2004.10.003

122
C. Ye et al. / Solid State Communications 133 (2005) 121–123
2
. Experiment
The potassium permanganate (KMnO
4
), Manganous
chloride (MnCl ), polyethylene glycol (PG, MWZ6000),
2
polyacrylamide (PAM, MWO14,000,000) are obtained
guaranteed as analysis pure grade and used without further
purification and treatment.
2
.1. Preparation of MnO
2
In a typical experiment some starting solution, such as
aqueous solution KMnO (0.5 m/l), MnCl (2 m/l), PG
1 w/w%) and PAM (0.1 w/w%), were prepared prior to use.
4
2
(
A 150 ml KMnO and 10 ml PG solutions were taken and
4
the PH value was adjusted to 6–8 in a flask. Then the PAM
was introduced to control the viscosity of the mixed solution
reach to 40–50 MPa s at 65 8C. The stoichiometric amount
2
Fig. 1. XRD pattern of rod-shaped MnO crystal.
2
of MnCl was added slowly into the system under strong
average length of 250–350 nm and a diameter of 15–25 nm.
The ratio of length to diameter could reach more than 15:1.
Fig. 4 shows the electron diffraction pattern. The pattern
stirring. The obtained solution was aged for 12 h. After that,
the precipitation was filtered and washed carefully by hot
de-ionized water. The precipitation was filtered again and
treated by steam for 3 h. Finally it was dried in vacuum at
2
accounts for a stronger crystalline of the rod-shaped MnO ,
it also could be seen that the MnO is not a single phase
2
8
2
0 8C and the black powder MnO was obtained.
which is consistent with the result of XRD.
2
The HRTEM micrograph of MnO is exhibited in Fig. 5.
2
.2. Characterization
The result reveals that the rod-liked structure of the sample
is indeed partially crystalline, obvious amorphous domain
are also shown. The d-spacing between the crystal fringes is
measured in corresponding magnified inset, determined
X-ray powder diffraction data was collected on RIGAKU
D/Max-IIIA diffractometer using Cu K radiation at wave-
a
length 1.54178 nm (30 kV, 20 mA). The diffractograms
were obtained in the 2q range of 10–708 with divergence and
scatter slits of 18. The step interval was 0.18 and the scans
speed was 0.1 8/s. High resolution transmission electron
˚
values in the range of 7.0–7.5 A. These results are
completely in agreement with the corresponding XRD-
determined interlayer d-spacing (Fig. 1) for MnO2.
microscopy (HRTEM) of MnO was studied by a JEM-2010
2
microscope, operating at an acceleration voltage of 200 kV.
The electron diffraction (ED) patterns were also measured
by the electron microscope. Scanning electron microscopy
(
(
SEM) was carried out with a JSM-6700F microscope
JEOL, Japan) operated at 10 keV.
3
. Results and discussion
Fig. 1 shows the X-ray powder diffraction pattern of rod-
2
shaped MnO . It could be obviously found that the sample is
composed of two phase of MnO2 which are a-MnO2
(
(
JCPDS 44-0141) as the most part and a few g-MnO
JCPDS 14-0644). The diffraction peaks at 12.4, 17.7, 28.4,
2
3
5
7.2, 49.8, 59.8 and 69.3 are assigned to a-MnO and 41.8,
2
6.0, 65.1 to g-MnO . All peaks in the pattern can be
2
attributed to various reflections. In this figure, only those
peaks with strong intensities are marked with different
reflection planes. The d-spacing values are also marked.
2
Figs. 2 and 3 are the SEM and TEM images of MnO . In
Fig. 2 it could be seen that the sample is composed of rod-
liked and anomalistic particles. From Fig. 3 it could be seen
obviously that the crystal is the rod type. The crystal has the
Fig. 2. SEM image of MnO crystal.
2

C. Ye et al. / Solid State Communications 133 (2005) 121–123
123
Fig. 3. TEM image of MnO
. Conclusion
A new route to prepare rod-shaped MnO
2
crystal.
4
Fig. 5. HRTEM morphology of MnO
2
crystal.
2
is reported for
Acknowledgements
the first time in the article. The MnO crystal is supposed to
2
prepare under high viscosity. The sample was shown as rod-
shaped multicrystal by XRD and TEM. Though further
research should be taken to clarify the formation mechan-
ism, this material undoubtedly has a prosperous foreground.
The authors thank the Hei Long Jiang province Natural
Science Foundation for financial support (NO. B01).
References
[
[
1] M.M. Thackeray, M.H. Rossouw, A. de Kock, J. Power
Sources 43 (1993) 289.
2] B. Ayaz, A.T. DeVol, Nucl. Instrum. Methods Phys. Res.,
Sect. A 505 (2003) 458.
[
[
3] J.Q. Li, P.J. Xiao, J. Eur. Ceram. Soc. 21 (2001) 659.
4] Y. Chabre, J. Pannetier, J. Prog. Solid State Chem. 23 (1995)
1
.
[
[
5] H.S. Kim, B.N. Popov, J. Electrochem. Soc. 150 (2003) D56.
6] S. Bach, J.P. Pereira-Ramos, P.N. Baffier, Electrochim. Acta
3
6 (1991) 1595.
[
[
7] J. Hunter, J. Solid State Chem. 39 (1981) 142.
8] S. Bach, M. Henry, N. Baffier, J. Livage, J. Solid State Chem.
8
8 (1990) 325.
[
9] M.M. Thackeray, Prog. Solid State Chem. 25 (1997) 1.
[
10] X.D. Sun, C.L. Mai, Y. Wang, Inorg. Chem. Commun. 5
2002) 747.
(
[
[
11] F.A. Al-Sagheer, M.I. Zaki, Colloid Surf., A 173 (2000) 193.
12] S.L. Brock, N. Duan, T.Z. Rong, Chem. Mater. 10 (1998)
2
619; M.H. Rossouw, D.C. Liles, M.M. Thackeray, Mater.
Res. Bull. 27 (1992) 221.
[
13] Y. Muraoka, H. Chiba, T. Atou, J. Solid State Chem. 144
(
1999) 136.
2
Fig. 4. ED pattern of MnO crystal.
[14] Y. Xiong, Y. Xie, Z. Li, C. Wu, Chem. Eur. J. 9 (2003) 1645.