ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 10, pp. 1605!1608. + Pleiades Publishing, Inc., 2006.
Original Russian Text + I.I. Obraztsova, G.Yu. Simenyuk, N.K. Eremenko, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 10,
AND CORROSION PROTECTION OF METALS
Effect of the Nature of a Reducing Agent on Properties
of Ultradisperse Copper Powders
I. I. Obraztsova, G. Yu. Simenyuk, and N. K. Eremenko
Kemerovo Branch, Institute of Solid-State Chemistry and Mechanochemistry, Siberian Division,
Russian Academy of Sciences, Kemerovo, Russia
Received March 29, 2006
Abstract-Ultradisperse copper powders were produced by reduction of copper sulfate with glycerol,
L-ascorbic acid, sodium hypophosphite, glucose, and hydrazine. The influence exerted by the nature of
a reducing agent on the size-related parameters and physicochemical properties of the powders was studied.
One of the main current issues of modern science
and technology is production of electrically conduct-
ing ultradisperse powders (UDPs) of copper. Numer-
ous methods for synthesis of copper UDPs are known,
which enable wide variation of their dispersity and
properties. However, the problem of synthesis of cop-
per UDPs with controlled particle size distribution,
which can be used to create materials with nearly
metallic electrical conductivity, remains topical. Com-
posite materials of this kind find wide application in
electronics for development of electrically conducting
glues and pastes used in low-temperature soldering of
device elements and in assembly of integrated circuits
and flexible printed-circuit boards.
Previously, methods for synthesis of copper UDPs
by reduction of copper sulfide with glycerol have been
developed and patented [1, 2]. It was shown in 
that chemical modification of copper UDPs makes
it possible to obtain from these UDPs formulations
possessing increased stability (of epoxy type, more
than 10 years; of novolac type, more than 6 years) and
low electrical resistivity (10
It has been shown that it is preferable to carry out
reduction of various copper salts with sodium hypo-
phosphite and hypophosphorous acid in the water3
hexanol system, rather than in an aqueous medium .
This is so because hexanol adsorbed on the surface of
UDPs leads to an increase in their stability and elec-
trical conductivity by blocking the surface of copper
particles and thereby preventing their oxidation by
atmospheric oxygen. It was also demonstrated that
additional treatment of copper UDPs with formic acid
makes them more stable and electrically conducting.
The present communication reports the results ob-
tained in an experimental study of copper sulfide re-
duction with various reducing agents. The influence
exerted by the nature of the reducing agent on the dis-
persity, stability, and electrical conductivity of copper
powders is analyzed.
Five different reducing agents were chosen for
copper by analysis of published data. These are glyc-
erol, L-ascorbic acid, sodium hypophosphite, D-glu-
cose, and hydrazine.
The results obtained in reduction of copper salts
with sodium hypophosphite have been described in
sufficient detail [13 4]. The reduction with glycerol
was carried out by the procedure described in .
The reaction of copper sulfate with sodium hypophos-
phite was performed by the method reported in .
The procedure used to reduce copper salts with ascor-
bic acid was described in .
The reduction with glucose was carried out in
an alkaline medium by the technique reported in .
Copper sulfate and glucose were dissolved in separate
vessels. A minor amount of an alkali (NaOH, KOH)
was introduced into the glucose solution to bring
the solution pH to 839. The copper sulfate solution
was heated to 80390oC. Then the glucose solution
was gradually poured in the copper sulfate solution
under permanent agitation and the mixture heated to
80390oC. A red precipitate was formed in 40350 min.
The precipitate was separated from the solution, treated
with formic acid to remove copper oxides, and stored
in a 0.05% solution of stearic acid in ethanol.