ADOUT THE OPPORTUNITY TO PRODUCE COPPER POWDER
WITH SMALLER PARTICLES SIZE BY ADDITION
SURFACTANT Ф-1 TO SOLUTION
Darintceva A.B., Murashova I.B., Osipova M.L*., Saveliev A.M*., Lebed’*
A.B.,ZaikovYu.P.
The Ural State Technical University,Yekaterinburg, Russia,
620002, Mira st., 19, Electrochemical Department, E-mail: el-chem@mail.ustu.ru
*
PC «Uralelectromed’», V.Pyshma, Russia, E-mail: is_lab@elem.ru
The industry needs for copper powders of different brands. The powder of
brand SA is in popular demand now. It contains the fractions of undersize particles
more in compare with other heavy powders of other brands (for example of GGbrand). It is rather difficult to foresee the yield the powder of certain brand in all the
powder mass because dendrytic deposit puts a lot of operations after electrolysis:
transport from the cell, water rinsing, extraction, drying, miling, screening,
classification [1]. It changes own properties on every of these stages. But still there is
some opportunity to make clear the tendency of powder properties changing in new
conditions of electrolysis.
It has been shown that cathode dendrite crystallysation runs under mixed
control on growth front [2], to be more correct on dendrite tips [3]. The most of
surfactants being carried in solution may be adsorbed on electrode surface and hence
have influence on kinetics of electrode processes. The change of copper exchange
current density and transfer factor in surfactant’s presence will result in another
distribution of overpotential between activation and diffusion its parts. The surfactant
Ф1 is known as the substance with the properties of flocculant. Really it has been
mentioned its some decreasing effect on cathode overpotential (Fig.1)
Current density,A/m2
1800
1200
600
0
0,000
0,100
0,200
0,300
overpotential,V
pure+Ф1
pure
Fig. 1. Potentiodynamic polarysation curves on copper electrode in pure electrolyte
and in the presence of 1 mg/L of Ф1.
The curves have been obtained in solution with 40 g/L of (Cu2+) at 55 0C with the
help of potentiostat IPC Pro at 4 mV/s velocity of potential arising. Transition to
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(Cu2+) concentration of 23 g/L (as it is necessary for powder production of SA brand)
has been performed in accordance with the law of electrochemical kinetics [4]:
1 c
i 0  i 00  cO
ST
(1)
where i 00 - standard exchange current density,  - transfer factor, cO – concentration
of Ox-form,
cST – standard concentration (1000 mole/m3 for metal ions). Because of the large
value of exchange current density in concentrated solution the anode component has
been taken into account in cathode part of cathode current density.

i 
i 
 zF 
 1   zF   
 exp 
ik  ia ,
i  i 0  1 
   exp  
(2)
   1 
RT    i lim 
 RT 

  i lim 
where ik and ia – are cathode and anode kinetic current densities. After devision by ik
and abbreviation i0 in subtrahend it will be obtained after some transforms




zF
i

.
ln B  ln i 0  
 , where B  ln
(3)

i
RT
 zF  
 exp  

1
i lim
 RT  

As a result the following kinetic parameters have been calculated for cathode
processes (table).
Table. Kinetic parameters for cathode processes in solutions of different composition
Pure
solution
with
Cu2+ Solution with Ф1 1mg/L and cCu
2+
concntration
40 g/L
23 g/L
40 g/L
23 g/L
io,A/m2
163,514
111,987
171,314
117,784
0,316
0,323
0,316
0,323

2
ilim ,A/m
1644
945,587
1632
938,4
Alteration the cathode kinetic parameters leads to change the structural characteristics
of dendrite deposit [4].These characteristics may be estimated as a result of simulation
in terms of dendrttic tip radii (rtip) distribution. The simulation of dendrite
crystallization is based on consideration this process as consisting of two electrode
reactions, one of which takes place under diffusion control (copper deposition) while
another (hydrogen evolution) runs on all electrode surface under control of charge
transfer. Four differential equations have been posed for description the crystallization
of dendrite deposit (for dendrite length y, curvature radii of its tips rtip, metal kinetic
current density ik , hydrogen current density iH). The initial conditions are calculated
on the base of charge balance and on principle of electrode equipotentiality.
Simulteneous equations have been decided computationally in mathematical packet
by Runge-Kutta method. The received correlations y(t), rtip(t), ik(t) and iH(t) open the
opportunity to describe the growth dendrite dynamics as well as the deposit structural
change. The latter is described as the distribution the deposit accordingly to dendrite
tip radii (rtip).
Search for initial conditions for differential system decision has led to
different results for initial densities of dendrite-nuclei. There has been nucleated
more nuclei with less curvature radii rtip in solution with Ф1 addition. It is very likely
due to surface activity of flocculant Ф1.So the dynamics of dendrites growth have
proved to be different too. (fig.2)
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12
50
8
25
0
0,00
4
0
0,25
0,50
0,75
1,00
0,35
0,8
0,28
0,6
0,21
0,4
0,14
0,2
0,07
0
0,00
0
relative time=t/tgrowth
itip(pure)
rB*10^5,m(pure)
1
Potential,V,(nhe)
16
75
Current efficiency
20
Tip radii*10^5,m
current
densities,A/m2
100
0,25
0,5
0,75
1
relative time = t/tgrowth
itip(+Ф1)
rB(+Ф1)
Cef
Cef(+Ф1)
-E,B
-E,B(+Ф1)
Fig.2. Dendrite tip radii changings and Fig.3. Potential dynamics and current
current densities on them during electrolysis. efficiencies in pure solution and in Ф1
presence.
The dendrites with less tip curvature radii develop through all the period of their
growth in solution with Ф1 addition. It calls for more quick their lengthening, higher
current densities on the tips, quick increasing of growth front square and as a
consequence the higher current efficiency (fig.3). Quick development of dendrites
means the larger effective diameter of electrode with the deposit and decreasing of
current density on growth front. These appearances are accompanied with potential
shift to more positive region (fig.3).
The received information constitutes the base for calculation the structural
characteristics of friable deposit after electrolysis: for example distribution the deposit
in terms of dendrite tip radii. Certainly it is not just the same as the results of grainsize classification but still it gives information about future results of mechanical
powder treatment. So let us divide all the region of radii changing on some parts and
find the charge quantity for radii alteration from rj to rj+1 (Fig. 4).
Fig.4. Current on growth front and dendrites tip radii during electrolysis in pure
electrolyte (a) and in the presence of Ф1 (b).
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The area under the proper curve IM, t on the circuit between moments corresponding
radii rj and r j+1 represents such the charge quantity with t in real scale. Therefore its
quotient to all the area under the curve IM(t) is the share of the powder with dendrite
radii 0,5( rj + r j+1 ). (fig.5)
The less tip radii of dendrites are accompanied by higher density of tips displacement
on unit of growth front area. In turn, it means the more fork of dendrite side branches
which provides them high stability of ready-made product. Simulated tip dendrite
radii distribution has shown that distribution maximum shifts substantially to
production of finer powder deposit in Ф-1 flocculant presence. The results of
distribution analysis testifies that surfactant Ф1 may be rather useful for production
the powder with the particles of less size in compare with the powder of GG brand.
Some practice of that direction took place in industrial conditions of PC
«Uralelectromed’».
0,35
Tip share with rtipj
0,28
0,21
0,14
0,07
0
-12
-11
-10
-9
-8
-ln(rB)
pure
with Ф1
Fig. 5. Distribution the dendrite deposit in relation tо rtip in pure solution
and in presence of Ф1- surfactant.
Сommercial testing took place with electrolyte containing surfactant-analog of Ф-1. It
showed that the yield of powder SA brand increased to 76-86% in compare with
routine 66% without flocculant.
The test lasted for 22 days. Powder properties were measured periodically.
The bulk density compiled from 1,4 to 1,92 g/ sm3 for the powder taken off the
cathode rod in electrolyte with 3,5 mg/L of flocculant and 1,4 to 1,85 g/ sm3 when
flocculant content was from raised to 5,0 mg/L. It wasn’t fixed the raised yield of
cathode scrap.
LITERATURE
1. Nichiporenko O.X., Pomosov A.V., Naboychenho S.S. The powders of copper and
of its alloys (in Russian). Metullurgiya, Moscow, 1988
2. Despic A.A., Popov K.I. Тhe Modern Aspects of Electrochemistry N.Y.: PlenumPress 1972 V.7 P.199-313.
3. Murashova I.B., Pomosov A.V., Potapov O.A. // Powder metallurgy and ceramics,
1991, March, P.5.
4. Murashova I.B., Burchanova N.G. //Electrochimiya (Rus) 2001 V.37 #7 P.871877.
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