ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ
The process of mixed oxide coatings formation on a high-silicon aluminum alloy in a cobalt-containing pyrophosphate electrolyte by the plasma-electrolytic oxidation (PEO) method is studied. It was shown that AL25 chemical composition heterogeneity causes the consumption of a part of the anode curren...
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| Date: | 2020 |
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V.I.Vernadsky Institute of General and Inorganic Chemistry
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Ukrainian Chemistry Journal| _version_ | 1871465403769683968 |
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| author | Sakhnenko, Nikolay Ved’, Maryna Karakurkchi, Ann |
| author_facet | Sakhnenko, Nikolay Ved’, Maryna Karakurkchi, Ann |
| author_institution_txt_mv | [
{
"author": "Nikolay Sakhnenko",
"institution": " National Technical University \"Kharkiv Polytechnic Institute\", Kharkov, Ukraine"
},
{
"author": "Maryna Ved’",
"institution": " National Technical University \"Kharkiv Polytechnic Institute\", Kharkov, Ukraine"
},
{
"author": "Ann Karakurkchi",
"institution": " National Technical University \"Kharkiv Polytechnic Institute\", Kharkov, Ukraine"
}
] |
| author_sort | Sakhnenko, Nikolay |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:42Z |
| description | The process of mixed oxide coatings formation on a high-silicon aluminum alloy in a cobalt-containing pyrophosphate electrolyte by the plasma-electrolytic oxidation (PEO) method is studied. It was shown that AL25 chemical composition heterogeneity causes the consumption of a part of the anode current to homogenize the treated surface, which is reflected in minimizing the content of doping components at the initial processing stage. It was established that the growth of mixed oxides Al2O3·CoxOy relative mass is a function of time with a maximum at 55 minutes. The chemical, phase composition and surface morphology of the formed oxide layer depend on the oxidation time. The catalytic component content in the surface oxides varies from 0.2 to 23.3 at.% with an increase in processing time of 10 to 60 minutes. Maximum cobalt incorporation into the oxide layer occurs at PEO of 35–50 minutes, while the silicon content in the surface layers does not exceed 2 at.%, which is favorable for the catalytic properties. The cobalt oxide, preferably Co3O4, incorporation in the alumina α-Al2O3 matrix is visualized by the blue-violet color steroidal surface structures in the sites of micro-arc discharges. The alumina cobalt oxide mixture layers are characterized by a developed micro-globular surface which consists of spheroid conglomerate with an average size of 1–2 microns. There are some amorphous phases in the structure of mixed oxides due to non-equilibrium PEO conditions. The set of detected factors is a prerequisite for the high catalytic properties of oxide coatings. A promising field of Al2O3·CoxOy systems application is intra-cylinder catalysis in internal combustion engines. |
| doi_str_mv | 10.33609/0041-6045.86.1.2020.12-21 |
| first_indexed | 2025-09-24T17:43:23Z |
| format | Article |
| fulltext |
ФІЗИЧНА ХІМІЯ
12 ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1
UDC 621.35 doi: 10.33609/0041-6045.86.1.2020.12-21
N.D.Sakhnenko, M.V.Ved’*, A.V.Karakurkchi
PECULIARITIES OF COBALT CONTAINING OXIDE COATINGS FORMATION
ON SILUMIN
National Technical University "Kharkiv Polytechnic Institute", 2 Kyrpychova Str., Kharkov, 61002,
Ukraine
*е-mail: vmv@kpi.kharkov.ua
The process of mixed oxide coatings formation on a high-silicon aluminum alloy in a
cobalt-containing pyrophosphate electrolyte by the plasma-electrolytic oxidation (PEO)
method is studied. It was shown that AL25 chemical composition heterogeneity causes
the consumption of a part of the anode current to homogenize the treated surface, which
is reflected in minimizing the content of doping components at the initial processing
stage. It was established that the growth of mixed oxides Al2O3·CoxOy relative mass is a
function of time with a maximum at 55 minutes. The chemical, phase composition and
surface morphology of the formed oxide layer depend on the oxidation time. The catalyt-
ic component content in the surface oxides varies from 0.2 to 23.3 at.% with an increase
in processing time of 10 to 60 minutes. Maximum cobalt incorporation into the oxide
layer occurs at PEO of 35–50 minutes, while the silicon content in the surface layers
does not exceed 2 at.%, which is favorable for the catalytic properties. The cobalt oxide,
preferably Co3O4, incorporation in the alumina α-Al2O3 matrix is visualized by the blue-
violet color steroidal surface structures in the sites of micro-arc discharges. The alumina
cobalt oxide mixture layers are characterized by a developed micro-globular surface
which consists of spheroid conglomerate with an average size of 1–2 microns. There are
some amorphous phases in the structure of mixed oxides due to non-equilibrium PEO
conditions. The set of detected factors is a prerequisite for the high catalytic properties
of oxide coatings. A promising field of Al2O3·CoxOy systems application is intra-
cylinder catalysis in internal combustion engines.
K e y w o r d s: plasma-electrolytic oxidation, alumina matrix, cobalt oxides, catalytic
activity, intra-cylinder catalysis.
INTRODUCTION. The alloys of alumi-
num with silicon are demanded construction
materials. They are widely used in various
industries: motor engineering and automo-
tive, water and heat supply systems, etc. At
present there is an intensive development of
technologies for improving the operational
properties of metals and alloys by modi-
© N.D.Sakhnenko, M.V.Ved’*, A.V.Karakurkchi, 2020
mailto:vmv@kpi.kharkov.ua
Peculiarities of cobalt containing oxide coatings formation on silumin
ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1 13
fying their surface [1,2]. One of the most
demanded and promising methods is the
plasma-electrolytic oxidation (PEO) of valve
metals, which allows forming oxide coatings
with increased mechanical, corrosion and
catalytic properties [3, 4]. Among the ad-
vantages of PEO should be noted non-
toxicity of used electrolytes, the simplicity
and compactness of the working equipment,
the lack of preliminary surface preparation
stage, the possibility of processing large
mass and complex geometry parts. Changing
the oxidation conditions, the electrolyte
qualitative and quantitative composition, the
dopants nature allows varying the composi-
tion and properties of the formed oxide
layers [5,6].
One of the topical directions of the prac-
tical use of oxide coatings on aluminum and
alloys is catalytic redox processes, in partic-
ular, eco-friendly catalysis [7–10]. For these
purposes compounds of catalytically active
components are introduced in the composi-
tion of highly developed surface layers.
Most often this is achieved by impregnating
(precipitating) a preformed matrix of base
metal oxide in solutions containing salts of
dopants metals followed by heat treatment of
the resulting material [11, 12]. However, this
approach not only complicates and raises the
cost of the technological process, but also
does not allow obtaining systems with sig-
nificant content of the catalytic component
and high adhesion to the substrate.
At the same time, it is promising to de-
velop a PEO technology for the formation of
a highly developed carrier (base metal oxide
matrix) in one process with dopants incorpo-
ration (preferably transition metal oxides)
throughout the processing period due to the
implementation of electrochemical and
thermo-chemical reactions in high-energy
modes [13, 14]. This will provide a longer
service time of the resulting catalytic materi-
al and substantially higher functional proper-
ties.
In previous studies, a rather complicated
mechanism of reactions in working solutions
during the oxidation of valve metals and the
feasibility of using a complex of electrolytes
based on diphosphate for PEO of AL25 alloy
were shown [15, 16]. As catalytically active
components, based on physical and chemical
properties, manganese and cobalt were se-
lected. It was found that the ratio of cobalt
and ligand concentration affects the oxida-
tion process parameters and allows forming
coatings with varying content of the catalyti-
cally active component. For further research,
the composition of the electrolyte was se-
lected, which allows oxide layers enriched in
the catalytically active component to be
formed with a higher surface development
degree [17].
The purpose of this work is to investi-
gate the effect of the oxidation time on the
composition, phase structure and morpholo-
gy of mixed aluminum and cobalt oxide
coatings to select the optimal parameters for
catalytic materials formation.
EXPERIMENT AND DISCUSSION OF
THE RESULTS. Oxide coatings were formed
on rectangular samples of cast aluminum al-
loy AK12M2MgN (AL25). The chemical
composition of silumin, wt. %: Si, 11.5–
13.0; Cu, 1.5–3.0; Ni, 0.8–1.3; Mg, 0.8–1.3;
Mn, 0.3–0.6; Fe < 0.8; Zn < 0.5; Ti < 0.2; Pb
< 0.1; Sn < 0.02; Cr < 0.2. Working area for
the formation of oxide coatings was 0.2 dm2.
The surface of samples for coatings applica-
N.D.Sakhnenko, M.V.Ved’, A.V.Karakurkchi
14 ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1
tion was prepared by grinding with subse-
quent degreasing, washed with water, and
dried at 30 °C. The samples were oxidized in
an electrolyte of the composition, mol/dm3:
0.4 K4P2O7 and 0.1 CoSO4. PEO was con-
ducted in the galvanostatic mode at a current
density of 3–5 A/dm2 using an industrial sta-
bilized power source B5-50 (Ukraine), an
electrolytic cell with forced cooling and stir-
ring, an ammeter and a voltmeter. Coatings
were formed under cooling and mixing the
electrolyte and controlling the process pa-
rameters. The temperature of the working
solutions was maintained in the range of 20–
25 °C. The sparking voltage US was 115–
120 V, the formation voltage was controlled
to be UF = 140–160 V.
The chemical composition of the coat-
ings was determined by an energy-dispersive
spectrometer INCA Energy 350. The surface
morphology of the coatings was studied us-
ing a scanning electron microscope ZEISS
EVO 40 XVP. X-ray diffraction analysis
was performed on an X-ray diffractometer
DRON-2 in monochromatic CoKα radiation
(λ = 1,7902 A). The phase identification was
performed by comparing the interplane spac-
ing (d, A) and the relative intensities of the
experimental curve with the data of the
PCPDFWIN electronic file system.
The catalytic properties of the oxide sys-
tems were studied in the oxidation of car-
bon (II) oxide to carbon (IV) oxide. The
studies were conducted on a laboratory
bench in a tubular flow reactor made of sili-
ca glass with a coaxially wound heating coil.
The initial mixture of air and carbon (II) ox-
ide with a concentration of 1.0 vol. % was
fed to a reactor with a volume of 1.5·10–2
dm3 at a rate of 1.5 dm3/h. The reactor tem-
perature was gradually increased from 20 to
450 °C at a rate of 1°C/s. The CO concentra-
tion at the inlet and outlet of the reactor was
recorded using Dozor signaling-analyzing
devices. The catalytic activity was evaluated
by the following parameters: the initial tem-
perature of the oxidation process (the igni-
tion temperature, Ti) and the conversion ex-
tent (X, %). The extent of conversion was
calculated by the following equation:
%,100
) СО(
) СО() СО(
i
fi ⋅
−
=
c
ccX
where с(СО)i and с(СО)f are the initial and
final concentrations of carbon (II) oxide, %.
The studies demonstrate that the chron-
ograms of operating voltage (formation
curves) and voltage change (trend) during
oxidizing silumin in the electrolyte 0.4
mol/dm3 K4P2O7, 0.1 mol/dm3 CoSO4 at dif-
ferent current densities have a classic form
(fig. 1) consisting of characteristic regions
[18, 19]. The first prespark region I
(fig. 1, a) corresponds to the formation of
silumin components in the oxides phase and
voltage increases linearly with time. In the
second prespark region II, the change in the
operating voltage is influenced by the oppo-
site processes of growth and destruction of
oxide layers, which affects the reduction in
dU/dt. Moreover, with increase in current
density, the formation rate exceeds the disso-
lution rate and dU/dt is higher (fig. 1, b).
The third section (fig. 1, III) corresponds
to the transition of the PEO process to the
sparking mode due to the phase oxides
breakdown. Not only electrochemical, but
also thermochemical reactions occur in the
spark zone, associated with water
thermolysis and with the participation of
Peculiarities of cobalt containing oxide coatings formation on silumin
ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1 15
electrolyte components. The sparking
a
b
Fig. 1. Formation curves (a) and voltage trend
(b) at oxidation current density, A/dm2: (1) 3,
(2) 5, (3) 10.
voltage increases with increasing current
density, and it is at this stage that the proba-
bility of dopants inclusion in the aluminum
oxide matrix increases. The time of sparking
decreases from 6 to 1 min with increase in
current density i over the studied interval.
Sparking voltage in all cases is 120–125 V.
Sparking intensity in the oxidation process is
quite high. Region IV of formation curves is
associated with sparking to microarc regime
transition. The final formation voltage de-
pends on the initial current density of PEO.
For i = 3–5 А/dm2 UF is 160–170 V and en-
ables conducting the process of PEO treat-
ment within 15 min or longer. At the current
density of 10 A/dm2 UF does not exceed
160 V. The oxidation process rapidly goes
through all stages and from the 4th minute
enters the arc mode. In this case, PEO of the
alloy after 8 min is impractical; the formed
coating is destroyed under the influence of
arc discharges.
Figure 2 shows the morphology and
chemical composition of the silumin surface
oxidized at a current density of 3 A/dm2 in
different regions of the formation curve
(time of oxidation). Due the local dissolution
of alloying components in regions I and II
particularly silicon content in surface layers
is reduced by 3–4 at.% in comparison with
its percentage in silumin. The transition from
the juvenile surface to the developed alumi-
na structure with a large number of irregular
shaped inclusions (Fig. 2 a) is observed. At
this stage, there is almost no incorporation of
additional components into the oxide layer.
The sparking initiation (luminescence) is
visualized by the appearance of a small
sparks that evenly cover the surface to be
treated, which characterizes the beginning of
electrolyte components incorporation into
the surface layers (fig. 2, b). On SEM imag-
es, it is possible to identify a significant
number of crater-like small apertures with
fused edges. The content of silicon in the
surface layer is reduced by almost two
N.D.Sakhnenko, M.V.Ved’, A.V.Karakurkchi
16 ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1
a b c
Fig. 2. Morphology and chemical composition of the surface , at.% : a – prespark (regions I and II),
Al – 33.5, O – 56.0, Si – 10.5; b – sparking (region III) Al – 33.5, O – 56.7, Si – 6.5, Co – 3.3, c –
microarc (region IV), Al – 33.3, O – 55.2, Si – 2.5, Co – 9.0; magnification × 500.
times and is not more than 5 at.%. In this
case, the content of cobalt gradually increas-
es to 3.3 at.%.
Under the conditions of constant current
density, the oxidation process almost instan-
taneously goes into the micro-arc mode:
there is an enlargement of sparks with de-
crease in their number, the burning of micro-
arc discharges occurs at the corners (projec-
tions) of the specimen and is accompanied
by a characteristic cracking due to the "col-
lapse" of gas vapors in micro-discharge
channels. In places of burning sparks appear
spheroid islands of characteristic blue-violet
color, typical for the incorporation of cobalt.
During processing, the number of such is-
land structures significantly increases, they
are combined, agglomerated and form mosa-
ic structures (fig. 2, c).
The mixed cobalt oxides formation is al-
so evidenced by the chemical composition
analysis at different sites of the sample sur-
face. The spheroids and agglomerated struc-
tures exhibit a range of 5.0–23.3 at.% (Co),
on the valley of the sample cobalt percentage
is about 14.5 at.%. For the silicon content
there is a reverse dependence: on the hills Si
does not exceed 2.0 at.%, and on the valley
it is 5.0 at.% throughout the processing peri-
od.
The influence of current density is suffi-
ciently evident in the change of surface mor-
phology of oxide coatings obtained during
15 min. (fig. 3).
In the PEO process, cobalt incorporation
into oxide layers occurs in the form of drop-
shaped and spherical inclusions of blue-
purple color (fig. 3, a). With increase in oxi-
dation current density from 3 to 5 A/dm2,
their number increases, they form mosaic
structures and evenly cover the entire sample
surface (fig. 3, b). The resulting ceramic-like
coating has high adhesion to the substrate.
Oxidation of samples at 10 А/dm2 leads to
cobalt incorporation in the form of volumi-
nous islet structures (fig. 3, c). Given a quite
rapid transition of PEO to the arc mode,
there is a tendency to these inclusions
Peculiarities of cobalt containing oxide coatings formation on silumin
ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1 17
a b c
Fig. 3. Surface morphology of Al2O3·CoOx coatings, obtained at different current densities, А/dm2:
(a)3; (b)5; (c)10; magnification ×500.
peeling off from the substrate.
The results of the X-ray diffraction anal-
ysis exhibit difference between the silumin
samples oxidized in a pyrophosphate solu-
tion and in an electrolyte with cobalt sulfate
addition (fig. 4).
There are lines associated only with
α-Al2O3 and Si on XRD patterns of samples
treated in a cobalt-free solution. And the
shape of XRD patterns for mixed oxide sys-
tems substantially changes which confirms
the incorporation of Co3O4 oxides into the
alumina matrix. The intensity of the cobalt
oxide lines depends on the quantitative com-
position of the surface layer. The X-ray dif-
fraction pattern also revealed a wide halo at
angles of 2θ ~ 10–30° reflecting amorphous
structure.
Testing the oxide system in the model
reaction of carbon (II) oxide conversion to
CO2 showed (table) that their activity (both
ignition and complete conversion (Tc) tem-
perature) is similar to platinum catalyst and
is much better than the parameters of
alumina.
Pilot tests of mixed oxides deposited on
the surface of the combustion chambers pis-
ton of an ICE, showed that the coating of
Al2O3·CoOx allows ones to reduce NOx
emissions by 10 % and CO ones by 15–18 %
in forced diesel engine operating modes.
This is due to the lower the ignition tempera-
ture of the air-fuel mixture on the surface of
Al│Al2O3·CoOx catalyst composed of mixed
oxides with developed surface.
The heterogeneity of the chemical com-
position and a significant amount of doping
components in silumin in comparison with
pure aluminum result in differences in the
technological parameters of PEO [20]. This
is due to the consumption of a certain
amount of anode current at the initial oxida-
tion stage to homogenize the alloy surface.
The higher the operating current the faster
the alloy components oxidize from the sur-
face in the alkaline environment in the pres-
ence of pyrophosphate. The surface becomes
chemically homogeneous and phase alumina
N.D.Sakhnenko, M.V.Ved’, A.V.Karakurkchi
18 ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1
is formed. The latter serves as a matrix for
the incorporation of catalytically active co-
balt in the sparking region of PEO. The re-
flection of this is a change in the chemical
composition and morphology of the surface
of the sample in different sections of the
voltage chronogram.
Considering the competing processes of
formation and dissolution of phase oxide at
Fig. 4. XRD patterns for oxidized silumin and
mixed oxide coatings. The composition is
similar to fig. 2, b.
T a b l e 1
Characteristics of CO conversion to CO2
Material Metal,
at.% Ti, K Tc, K
Pt 100 490 570
Al|Al2O3 30.8 595 670
Al|Al2O3·
CoOx
8.7 505 580
the initial oxidation stage, the actual growth
of the mass of the oxide layer is observed
only in the micro-arc mode with a gradual
increase and a maximum of 55 minutes of
processing. The optimal time interval, based
on the results obtained, is the oxidation of
AL25 within 30–55 minutes. In the studied
conditions, the micro-arc PEO regime is
maintained quite long, which leads to a uni-
form increase in the thickness of the oxide
layer with increasing processing time.
It is noticeable that the change in the
chemical composition of the formed oxide
coatings can be traced in the change in the
morphology of the surface layers in the vari-
ation of the time of PEO treatment. The in-
corporation of cobalt into the surface layers
substantially changes their morphology and
causes the formation of bulk structures with
a high specific surface. With increase in the
processing time from 15 to 20 minutes, the
morphology of the samples surface varies
from the characteristic alumina barrier struc-
ture to a highly developed mosaic one if co-
balt is incorporated in the alumina matrix.
This is due to a growth of the oxide layer
thickness and an increase in the cobalt con-
tent in the sparking mode. PEO treatment for
30–55 minutes leads to the consolidation of
the formed ceramic-like coatings and the
formation of the structure of bulk spheroids.
With increase in processing time of up to 60
minutes, the surface of the coating becomes
almost uniform due to the "healing" of the
protrusions and defects, as well as the inclu-
sion of a significant amount of phosphates in
the surface layers. The obtained results are
in full accordance with the kinetic laws and
allow us to determine the rational time of
PEO for the application of oxide coatings of
a given composition and morphology.
The peculiarities of the phase structure
of obtained oxide coatings in combination
Peculiarities of cobalt containing oxide coatings formation on silumin
ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1 19
with a developed surface and a high cobalt
content are a prerequisite for their high cata-
lytic properties. The catalytic activity of
mixed oxide systems can be attributed to
several factors. Firstly, it is a high affinity of
non-stoichiometric cobalt oxides to oxygen
and the corresponding decrease in the activa-
tion energy of O=O double bond breakdown.
Secondly, the developed micro globular sur-
face of oxide systems is characterized by a
large number of catalytic centers and pro-
vides an increase in the number of elemen-
tary collisions and interactions.
CONCLUSIONS. Al2O3·Co3O4 mixed
oxide coatings with a cobalt content of up to
23.3 at.% were obtained on a high-silicon
aluminum alloy AL25 by one-stage plasma-
electrolytic oxidation in a cobalt-containing
pyrohosphate electrolyte. It has been estab-
lished that the surface concentration of Si in
mixed coatings is two to three times lower
than that in the processed alloy. The ratio of
cobalt and oxygen in the coatings is non-
stoichiometric; the content of cobalt in
mixed oxides increases with increasing cur-
rent density and operating time. With in-
crease in the cobalt content the surface mor-
phology varies from uniformly rough to mi-
cro-globular with relatively large spheroids.
The resulting oxide systems have a devel-
oped surface with a large number of catalytic
centers, consisting of spheroids and toroidal
structures that alternate between themselves.
The application of Al2O3·Co3O4 coatings on-
to the surface of combustion chambers helps
to save fuel and improves the ecological
characteristics of internal combustion en-
gines, which can therefore be recommended
for use in gas neutralization systems and in-
cylinder catalysts for ICE.
ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ
ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА
СИЛУМІНІ
М.Д.Сахненко, М.В.Ведь*, Г.В.Каракуркчі
Національний технічний університет
"Харківський політехнічний інститут", вул.
Кирпичова, 2, Харків, 61002, Україна
*е-mail: vmv@kpi.kharkov.ua
Вивчено процес формування змішаних
оксидних покриттів на висококремністому
алюмінієвому сплаві у кобальтвмісних піро-
фосфатних електролітах методом плазмо-
електролітичного окислення (ПЕО). Показа-
но, що гетерогенність хімічного складу АЛ25
обумовлює необхідність витрати частини
анодного струму на гомогенізацію поверхні,
що відбивається в мінімізації змісту легую-
чих компонентів на початковій стадії оброб-
ки. Встановлено, що зростання відносної ма-
си змішаних оксидів Al2O3·CoxOy є функцією
часу з максимумом, що припадає на 55 хв.
Хімічний, фазовий склад і морфологія повер-
хні утворюваного оксидного шару залежать
від часу окислення. Вміст каталітичного
компонента в поверхневих оксидах зміню-
ється від 0,2 до 23,3 %ат. при збільшенні ча-
су обробки від 10 до 60 хвилин. Максималь-
не включення кобальту в шар оксиду відбу-
вається при ПЕО 35–50 хвилин, в той час як
вміст кремнію в поверхневих шарах не пере-
вищує 2 %ат., що сприятливо для каталітич-
них властивостей. Включення оксиду коба-
льту Co3O4 у матрицю α-Al2O3 візуалізується
стероїдними поверхневими структурами си-
ньо-фіолетового кольору, які переважають у
місцях мікродугових розрядів. Шар змішано-
го оксиду алюмінію і оксидів кобальту хара-
ктеризується розвиненою мікроглобулярную
поверхнею, що складається з конгломератів
сфероїдів із середнім розміром 1-2 мкм. У
mailto:vmv@kpi.kharkov.ua
N.D.Sakhnenko, M.V.Ved’, A.V.Karakurkchi
20 ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1
структурі змішаних оксидів присутні аморф-
ні фази через нерівноважні умови ПЕО. Су-
купність описаних факторів – передумова
високих каталітичних властивостей оксидних
покриттів. Перспективною сферою застосу-
вання систем Al2O3·CoxOy є внутрішньоцилі-
ндровий каталіз у двигунах внутрішнього
згорання.
К л ю ч о в і с л о в а: плазмо-електролітичне
оксидування, матриця оксиду алюмінію, ок-
сиди кобальту, каталітична активність, внут-
рішньо-циліндровий каталіз.
ОСОБЕННОСТИ ФОРМИРОВАНИЯ КО-
БАЛЬТ - СОДЕРЖАЩИХ ОКСИДНЫХ ПО-
КРЫТИЙ НА СИЛУМИНЕ
Н.Д.Сахненко, М.В.Ведь*, А.В.Каракуркчи
Национальный технический университет
"Харьковский политехнический институт",
ул. Кирпичова, 2, Харьков, 61002, Украина
*е-mail: vmv@kpi.kharkov.ua
Изучен процесс формирования сме-
шанных оксидных покрытий на алюминие-
вом сплаве АЛ25 в кобальтсодержащем пи-
рофосфатном электролите методом ПЭО.
Показано, что гетерогенность химического
состава АЛ25 обусловливает необходимость
затраты части анодного тока на гомогениза-
цию поверхности на начальной стадии обра-
ботки. Установлено, что рост относительной
массы смешанных оксидов Al2O3·CoxOy явля-
ется функцией времени с максимумом, при-
ходящимся на 55 мин. Химический, фазовый
состав и морфология поверхности сформиро-
ванных оксидных слоев зависят от времени
ПЭО. Содержание Со в поверхностных слоях
изменяется от 0,2 до 23,3 % ат. при увеличе-
нии времени обработки с 10 до 60 мин. Слой
смешанных оксидов Al2O3·CoxOy характери-
зуется развитой микроглобулярной поверх-
ностью. В структуре смешанных оксидов
присутствуют аморфные фазы из-за неравно-
весных условий ПЭО. Совокупность описан-
ных факторов является предпосылкой высо-
ких каталитических свойств оксидных по-
крытий. Перспективная область их примене-
ния – внутрицилиндровый катализ в двигате-
лях внутреннего сгорания.
К л ю ч е в ы е с л о в а: плазменно-электро-
литическое оксидирование, матрица оксида
алюминия, оксиды кобальта, каталитическая
активность, внутрицилиндровый катализ.
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Received 12.06.2019
N.D.Sakhnenko, M.V.Ved’, A.V.Karakurkchi
20 ISSN 0041-6045. УКР . ХІМ . ЖУРН ., 2020, т . 86, No 1
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| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-118 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:01:29Z |
| publishDate | 2020 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/25/3be9c9769f981412374b5cf16b083e25.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-1182026-07-22T08:23:42Z PECULIARITIES OF COBALT CONTAINING OXIDE COATINGS FORMATION ON SILUMIN ОСОБЕННОСТИ ФОРМИРОВАНИЯ КОБАЛЬТ - СОДЕРЖАЩИХ ОКСИДНЫХ ПОКРЫТИЙ НА СИЛУМИНЕ ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ Sakhnenko, Nikolay Ved’, Maryna Karakurkchi, Ann plasma-electrolytic oxidation, alumina matrix, cobalt oxides, catalytic activity, intra-cylinder catalysis. плазменно-электролитическое оксидирование, матрица оксида алюминия, оксиды кобальта, каталитическая активность, внутрицилиндровый катализ. плазмо-електролітичне оксидування, матриця оксиду алюмінію, оксиди кобальту, каталітична активність, внутрішньоциліндровий каталіз. The process of mixed oxide coatings formation on a high-silicon aluminum alloy in a cobalt-containing pyrophosphate electrolyte by the plasma-electrolytic oxidation (PEO) method is studied. It was shown that AL25 chemical composition heterogeneity causes the consumption of a part of the anode current to homogenize the treated surface, which is reflected in minimizing the content of doping components at the initial processing stage. It was established that the growth of mixed oxides Al2O3·CoxOy relative mass is a function of time with a maximum at 55 minutes. The chemical, phase composition and surface morphology of the formed oxide layer depend on the oxidation time. The catalytic component content in the surface oxides varies from 0.2 to 23.3 at.% with an increase in processing time of 10 to 60 minutes. Maximum cobalt incorporation into the oxide layer occurs at PEO of 35–50 minutes, while the silicon content in the surface layers does not exceed 2 at.%, which is favorable for the catalytic properties. The cobalt oxide, preferably Co3O4, incorporation in the alumina α-Al2O3 matrix is visualized by the blue-violet color steroidal surface structures in the sites of micro-arc discharges. The alumina cobalt oxide mixture layers are characterized by a developed micro-globular surface which consists of spheroid conglomerate with an average size of 1–2 microns. There are some amorphous phases in the structure of mixed oxides due to non-equilibrium PEO conditions. The set of detected factors is a prerequisite for the high catalytic properties of oxide coatings. A promising field of Al2O3·CoxOy systems application is intra-cylinder catalysis in internal combustion engines. V.I.Vernadsky Institute of General and Inorganic Chemistry 2020-02-05 Article Article Physical chemistry Физическая xимия Фізична xімія application/pdf https://ucj.org.ua/index.php/journal/article/view/118 10.33609/0041-6045.86.1.2020.12-21 Ukrainian Chemistry Journal; Vol. 86 No. 1 (2020): Ukrainian Chemistry Journal; 12-21 Украинский химический журнал; ##issue.vol## 86 ##issue.no## 1 (2020): Украинский химический журнал; 12-21 Український хімічний журнал; Том 86 № 1 (2020): Український хімічний журнал; 12-21 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/118/75 Copyright (c) 2020 Nikolay Sakhnenko, Maryna Ved’, Ann Karakurkchi https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | плазмо-електролітичне оксидування матриця оксиду алюмінію оксиди кобальту каталітична активність внутрішньоциліндровий каталіз. Sakhnenko, Nikolay Ved’, Maryna Karakurkchi, Ann ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ |
| title | ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ |
| title_alt | PECULIARITIES OF COBALT CONTAINING OXIDE COATINGS FORMATION ON SILUMIN ОСОБЕННОСТИ ФОРМИРОВАНИЯ КОБАЛЬТ - СОДЕРЖАЩИХ ОКСИДНЫХ ПОКРЫТИЙ НА СИЛУМИНЕ |
| title_full | ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ |
| title_fullStr | ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ |
| title_full_unstemmed | ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ |
| title_short | ОСОБЛИВОСТІ ФОРМУВАННЯ КОБАЛЬТ ВМІСНИХ ОКСИДНИХ ПОКРИТТІВ НА СИЛУМІНІ |
| title_sort | особливості формування кобальт вмісних оксидних покриттів на силуміні |
| topic | плазмо-електролітичне оксидування матриця оксиду алюмінію оксиди кобальту каталітична активність внутрішньоциліндровий каталіз. |
| topic_facet | plasma-electrolytic oxidation alumina matrix cobalt oxides catalytic activity intra-cylinder catalysis. плазменно-электролитическое оксидирование матрица оксида алюминия оксиды кобальта каталитическая активность внутрицилиндровый катализ. плазмо-електролітичне оксидування матриця оксиду алюмінію оксиди кобальту каталітична активність внутрішньоциліндровий каталіз. |
| url | https://ucj.org.ua/index.php/journal/article/view/118 |
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