World Journal of Engineering
THERMOSTIMULATED SYNTHESIS
OF MoO3 AND WXMo1-XO3
NANO- AND MICROSCALE
PARTICLES AND THEIR
APPLICATION FOR DEPOSITION OF
Ni-OXIDE COMPOSITES
T.V. Sviridova1, L.I. Stepanova2, D.V. Sviridov 1
1
Chemistry Department of Belarusian State
University, e-mail: sviridov@bsu.by
2
Institute for Physico- Chemical Problems of Belarusian State University, e-mail: stepanovali@bsu.by
Leningradskaya str., 14, Minsk, 2200030, Belarus
One of the challenges of modern synthetic
chemistry is elaboration of effective approaches to
preparation of nano- and microparticles, in
particular, oxide and oxide-hydroxide nano- and
micro-phases. The considerable progress in this
direction was attained in recent years through using
thermostimulated polymerization of oxo-acids,
which opens the possibility of obtaining wide range
of metastable compounds and permits one to exert
an effective control over the characteristics of
resultant crystals.
Here we demonstrate the possibility of
synthesis of nanometer- and micron-sized particles
of molybdenum trioxide and molybdenum-tungsten
mixed oxides in aqueous medium and discuss their
applicability for electrochemical deposition of
metal-matrix composites with different tribological
properties. These studies evidenced that the change
of synthetic conditions is a powerful tool for
controlling the polycondensation process that in its
turn allows regulation of structural characteristics
and relative stability of precursors of growing oxide
phase.
In the case of molybdic acid, which exhibit
low rate of oxolation and rather long induction
period of solid phase growth, it is possible to
“freeze” MoO3 nuclei at different stages of growing
and ripening by changing the concentration of
mature solution and to perform there growing and
recrystallization at further synthetic steps. As a
result, a wide range of molybdenum trioxide
particles of different structure and dispersity can be
produced including spherical nanoparticles, needles
or perfect prisms of hexagonal MoO3(fig. 1).
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Fig. 1 SEM images of MoO3
particles of different shapes: (a) nanosized
spherolites, (b) micron-sized prisms, (c)
micron-sized needles
Particles of mixed oxide WxMo1-xO3
can similarly be obtained using the process of
two-step thermostimulated polycondensation.
The solid product of the reaction is not a
mechanical mixture of tungsten and
molybdenum oxides, with Mo:W ratio in the
mixed oxide and in the precursor being the
same.
The XRD analysis has revealed that
solid solutions are formed, the lattice
parameters being close to those of the
prevailing oxide. When percentages of
World Journal of Engineering
molybdenum and tungsten in the precursor are
Being added to a nickel plating bath,
approximately the same, the product of the reaction
both MoO3 and WxMo1-xO3 particles cois a mixed oxide with the composition W0.4Mo0.6O3.
deposit with nickel yielding composite
Thus synthesized particles of mixed oxide are
coatings. Pronounced redox activity inherent
spindle-shaped (fig. 2) and their size is determined
in MoO3 and WxMo1-xO3 creates favorable
by composition of precursor and exhibits increase
condition for electrochemical codeposition
as the molybdenum content in the reaction product
with nickel and provides rapid and effective
increases
overgrowing of incorporated particles by
matrix metal. The oxide loading varies within
1-12 wt. % being dependent on the oxide
concentration in the electrolyte, particle size
and plating conditions. At high concentrations
of oxide in the plating bath the deposition rate
exhibits decrease, whereas at modest
concentrations (0.1-3.0 g/l) the rate of
composite growth is not affected by the
presence of the oxide particles in the plating
solution.
Wear resistance of the composite coatings
obtained through embedment of MoO3 and
WxMo1-xO3 particles in the nickel matrix even
in rather low incorporation degree (1-4 wt. %)
exceeds wear resistance of bare nickel
coatings by 7-10 times. Metal-oxide
composite coatings of antifrictional or
frictional types (with friction coefficient
 0.15 and  0.4, respectively) can be
deposited depending on the size of the
particles, their morphology and concentration
in the plating bath. The distinctive feature of
Ni-MoO3 (WxMo1-xO3) composites is the fact
that they preserve the antifriction properties
and stability at the enhanced temperatures (up
to 500 oC) and remains stable under
conditions of oxidation wearing.
Acknowledgements: This work was
supported by Basic Research Foundation of
Belarus.
References
1. Stepanova L.I., Mozolevskaya T.V.,
Bodrykh T.I., Sviridov V.V. Composite Films
Nickel-Ultradispersed Oxide of Molybdenum
or Tungsten Electrochemical Forming in
Water Solutions // Reports of Belorussian
National Academy of Sciences. 2002. № 2.
P. 5-11 (in Russ).
2. Sviridova T.V., Stepanova L.I.,
Fig. 2 TEM images of WxMo1-xO3
Sviridov D.V. Nano- and Microcrystals of
particles of different shapes: (a) aggregates of
Molybdenum Trioxide and Metal-Matrix
nanoneedles, (b) submicron-sized and (c) micronComposites on Their Basis In: “Molybdenum:
sized spindle-like crystalites, synthesized by
Characteristics, Production and Applications”.
thermoinduced polycondensation of tungsticNY: Nova Science Publisher Inc., 2011.
molybdic acid used as the precursor.
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