Materials Sciences and Applicatio ns, 2011, 2, 1313-1316
doi:10.4236/msa.2011.29178 Published Online September 2011 (http://www.SciRP.org/journal/msa)
1313
Facile Synthesis and Thermal Stability of
Nanocrystalline Molybdenum Carbide
Youjian Chen1, Hong Zhang1, Jinfeng Zhang1, Jianhua Ma1,2*, H on g n an Ye3, Gaojin Qian3, Yi Ye3,
Shuang Zhong3
1College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, China; 2Nanomaterials and Chemistry Key Labo-
ratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, China; 3Oujiang college, Wenzhou Uni-
versity, Wenzhou, China.
Received October 13th, 2011; revised February 9th, 2011; accepted July 12th, 2011.
ABSTRACT
Nanocrystalline molybdenum carbide (Mo 2C) was prepared via one simple route by the reaction of metallic magnesium
powders with molybdenum trioxide and potassium acetate in an autoclave at the condition of 600˚C and 4 h. X-ray
powder diffraction (XR D) pattern indicated that the product was hexagonal α-Mo2C, and the cell constant was a =
3.0091 Å, c = 4.7368 Å. Scanning electron microscopy (SEM) image showed that the sample consisted of particles with
an average size of about 100 nm in diameter. The product was also studied by the thermogravimetric analysis (TGA). It
had good thermal stability and oxidation resistance below 450˚C in air.
Keywords: Molybdenum Carbide, Chemical Synthesis, X-Ray Diffraction, Thermogravimetric Analysis
1. Introduction
Molybdenum carbide, one of the most important com-
pounds among transition metal carbides, due to its prom-
ising physical and chemical properties, such as a high
melting temperature, high hardness, and high resistance
to corrosion and oxidation, high abrasion resistance,
good electrical conductivity. So it is widely used for cut-
ting materials, abrasive, anti-wear and aerospace materi-
als [1-4]. At the same time, Mo2C is used as a kind of
catalyst in various reactions [5-10]; even it is usually
superior to the noble metal catalysts in selectivity, stabil-
ity and resistance to poison, so that Mo2C might be con-
sidered as a cheaper substitute for the noble metal cata-
lysts. Because of the promising properties and extensive
application of Mo2C, it is meaningful to synthesize
nanocrystalline Mo2C, in a simple route at low tempera-
ture and with convenient manipulations.
Traditionally, mixing molybdenum powder with car-
bon black by annealing under argon flow or vacuum at a
temperature between 1400˚C and 1500˚C can produce
Mo2C. Later, Mo2C is synthesised via the reaction of
molybdenum oxide and high specific surface-active car-
bon at the lower reaction temperature [11]. Up to now,
many approaches have been developed for the prepara-
tion of Mo2C. Wang and co-workers [12] have shown
that bulk face-centered-cubic (fcc)-based η-MoC1–x and
hexagonal-close-packed (hcp)-based β-Mo2C have been
prepared using C3H8/H2 by temperature-programmed
reaction method and a rapid heating method. Arceo et al
[13] have reported hexagonal Mo2C have been synthe-
sized by mechanical alloying with a mixture of carbon
and molybdenum powder under argon atmosphere at 25
h, consequently. Norin et al. [14] have deposited single-
phase molybdenum carbide films on sapphire by chemi-
cal vapour deposition using C60 as a carbon source. Yao
[15] has used carbothermal reduction route to produce
the β-Mo2C in the presence of a small amount of H2 at
950˚C. T. Miyao et al. [16] have prepared molybdenum
carbide by nitridation of 12.5 wt％ MoO3/Al2O3 in a
flow of NH3 at 700˚C, followed by carburization in a
flow of 20％ CH4/H2 also at 700˚C for 3 h.
In this paper, we have developed a new convenient
route to synthesize nanocrystalline hexagonal α-Mo2C at
low temperature by the reaction of metallic magnesium
powders with MoO3 and CH3COOK in an autoclave at
600˚C. In this route, MoO3 as molybdenum source is
more stable and safe in operation than other molybdenum
source (e.g. MoCl5) and metallic magnesium powders as
reductant are also more safe and convenient than other
reductants (e.g. metallic sodium). Due to the whole syn-

Facile Synthesis and Thermal Stability of Nanocrystalline Molybdenum Carbide
1314
thesis route which is carried out in the sealed autoclave,
so it can be obtained that all manipulations are rather safe
and convenient, etc.
2. Experimental
In a typical experiment, analytical grade MoO3, analyti-
cal grade CH3COOK and analytical grade metallic mag-
nesium powders were put into a mortar, followed by
mixing these powders thoroughly. Then the mixture was
put into a stainless steel autoclave. After sealing under
argon atmosphere, the autoclave was heated at 600˚C for
10 h, followed by cooling to room temperature in the
furnace. The obtained product from the autoclave was
washed several times with absolute ethanol, dilute HCl
aqueous solution, distilled water to remove the impurities.
Finally the product was washed three times with absolute
ethanol to remove water. The final product was vacuum-
dried at 60˚C for 8 h. Black powders were obtained.
The obtained sample was analyzed by powder X-ray
diffraction (XRD) on a Bruker D8 Advance X-ray pow-
der diffractometer using Cu K-α radiation (wavelength λ
= 1.54178 Å). The operating voltagewas 40 kV. 2 theta
angles were from 20˚ to 90˚. The morphology of the
sample was observed from a JEOL JSM-6700F scanning
electron microscope, the operating voltage was 10 kV.
The thermogravimetric analysis was performed on a
thermal analyzer (Model: Q600) below 900˚C in air at a
rate of 5˚C·min–1 to study its thermal stability and oxida-
tion behavior.
3. Results and Discussion
Figure 1 shows the XRD patterns of the as-prepared
samples and Mo2C (JCPDS Card no. 35-0787). Pattern (a)
shows the sample prepared under the condition of 600˚C
and 10 h, there are eight obvious diffraction peaks in the
pattern in Figure 1(a). And all these diffraction peaks ((1
0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0), (1 0 3), (1 1 2), (2 0 1))
at different d-space can be indexed as hexagonal α-Mo2C.
The refinement gives the cell constants (a = 3.0091 Å, c
= 4.7368 Å), which is consistent with the value reported
in the literature (a = 3.0124 Å, c = 4.7352 Å) (JCPDS
card no. 35-0787). No evidences of crystal impurities
such as molybdenum, molybdenum trioxide, other mo-
lybdenum carbides, can be found in this XRD pattern.
The morphology of the prepared Mo2C sample was
investigated by field emission scanning electron micros-
copy. The SEM image of the as-prepared Mo2C sample
is shown in Figure 2. In this figure, the samples show
that it consists of particles with an average diameter of
100 nm. These particles exhibit slightly agglomerated par-
ticle morphology due to the ultrafine size of the sample.
In order to investigate the thermal stability and the
20 30 40 50 60 7080 90
2Theta/Degree
(a)
(b)
(a) 600 oC 4h
(b) Mo2C JCP DS C ard no.35-0787
Intensity/A.U
Figure 1. XRD patterns of the (a) as-prepared sample and
(b) Mo2C (JCPDS Card no. 35-0787).
Figure 2. SEM image of the as-prepared sample prepared
under the reaction condition of 600˚C and 4 h.
oxidation resistance of the as-prepared Mo2C powder
by the thermogravimetric analysis (TGA), which was
carried out at temperatures below 900˚C under flowing
air in Figure 3. In the figure, we can find that the weight
of the product has not changed significantly below 350˚C.
A slight weight loss indicates that the sample might ad-
sorb a little water on the surface. However, an obvious
weight loss step occurred in the temperature range of
about 350˚C to 450˚C, which may be attributed to oxida-
tion of the graphite to form CO2 [17]. In this stage, the
sample Mo2C is very stable. The Mo2C sample begines to
oxidize at the temperature about 450˚C, indicating that
the sample is oxidized to form molybdenum trioxide and
carbon dioxide. The sample can be oxidized thoroughly
at 550˚C. Therefore, the weight gain remains almost con-
stant on the TGA curve when the temperature ranges of
about 550˚C to 720˚C. When the temperature exceeds
720˚C, the curve of the as-prepared Mo2C sample has
suddenly declined, which is attributed to molybdenum

Facile Synthesis and Thermal Stability of Nanocrystalline Molybdenum Carbide1315
0100 200 300 400 500 600 700 800 900
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Weight/%
Temperature/ oC
Figure 3. TGA curve of the as-prepared Mo2C sample in
flow ing air.
trioxide evaporated at this high temperature (about
740˚C). In a word, because of the ultrafine particles, the
sample can be oxidized thoroughly at about 550˚C. But
the sample has good thermal stability below 450˚C.
4. Conclusions
In summary, nanocrystalline molybdenum carbide (Mo2C)
powder has been prepared via a simple thermal route by
the reaction of metallic magnesium powders with mo-
lybdenum trioxide and potassium acetate in an autoclave
at 600˚C for 4 h. The product crystalline structure is
hexagonal. It consists of particles with an average size of
100 nm. The product has good thermal stability and oxi-
dation resistance below 450˚C.
5. Acknowledgements
This work was supported by Innovation and Promotion
of science-technology project of Zhejiang Province and
Department of Education of Zhejiang Province of China
under Grant No. 20070546.
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