ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 4, pp. 405−411. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © N.S. Nikolaeva, V.V. Ivanov, A.A. Shubin, 2014, published in Zhurnal Prikladnoi Khimii, 2014, Vol. 87, No. 4, pp. 409−415.
INORGANIC SYNTHESIS AND INDUSTRIAL
Synthesis of Ag/ZnO Mixture
for Powdered Contact Materials
N. S. Nikolaeva, V. V. Ivanov, and A. A. Shubin
Siberian Federal University, Svobodnyi pr. 79/10, Krasnoyarsk, 660041 Russia
Received February 19, 2014
Abstract—The processes of a ultrafine Ag/ZnO mixture produced by coprecipitation from salt solutions were
investigated. The coprecipitation in AgNO
system was analyzed in the presence of surfactants,
considering the pH value and a solution composition contribution. The optimal coprecipitation conditions were
precipitating agent excess of ~20%, providing a pH value of ~10, with subsequent thermal decomposition
of the mixture at about 700 K. A thermal analysis of the precursor mixtures were carried out. The phase composition,
dispersity and morphology of the precipitates were determined before and after a thermal treatment. The size
decrease of the precipitated particles, as well as dispersity and distribution uniformity increase of the oxide
inclusions in the target composite matrix is due to the presence of surfactants in solutions.
The severe difﬁ culty in development of functional
composite materials is encountered in achieving the most
homogeneous distribution of components over the volume
of a system and their highest dispersity. The Ag/ZnO
material is used for switching contacts in low-voltage (up
to 1000 V) contactors (up to 1000 A) [1, 2]. In addition
to the dispersive reinforcement of the metallic matrix,
oxide incorporations in this composite serve to extinguish
the interruption arc, which provides the longevity and
operation reliability of electric apparatus. The size of the
oxide particles and its distribution in the silver matrix
predetermine the diffusion processes in thermal treatment,
microstructure, and physical and service properties of the
Ag/ZnO composite .
Contact materials are manufactured using the conven-
tional methods of powder metallurgy . However, these
methods have disadvantages associated with difﬁ culties
in obtaining the desired microstructure and functional
properties. The powder mixture has been produced by
mechanical mixing of powders, internal oxidation of
an alloy, and physicochemical homogenization [5, 6].
Among the wide variety of techniques used in practice to
create functional materials of this type, attention is still
attracted by the co-precipitation method, successfully
employed in the technology of the composite (Ag/15CdO)
. This method is attractive as regards the homogeneity
of the oxide dispersion and controlled microstructural
perfection in the uniform ﬁ neness by varying the pre-
cipitation parameters and surfactant additives.
The method has been used to obtain the Ag/ZnO com-
posite under consideration [8, 9]. However, the synthesis
of Ag/ZnO powder via coprecipitation have not been
studied in detail and the effect of the main factors has
not been considered. In this context, a study of this kind
seems to be topical.
In this study, the processes for making ultrafine
Ag/ZnO mixture for contact materials, based on the co-
precipitation method were examined. As the composition
was taken the 92Ag/8ZnO.
Chemical reagents were chemically pure
[GOST (State Standard) 1277–75],
O (GOST 5106–77), Na