Coatings of aluminium oxide Al2O3 were obtained by micro-arc oxidation under different conditions of
deposition. They were analysed by such methods as: positron annihilation spectroscopy (PAS), Rutherford
backscattering (RBS), X-ray diffraction (XRD) and scanning electron microscopy with microanalysis (SEM
with EDS). Investigated samples showed good adhesion to the substrate, low concentration of nanopores in
the bulk. Content of amorphous phase in the coating was about 20 vol.%, and metastable -Al2O3 - Al2O3
phases about less than 10 vol.%. It was demonstrated that by varying of parameters of deposition, it is possible
to control the physical – mechanical properties of obtained coatings as well as their element composition
and surface morphology.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3491

Drozdenko, Oleksii Oleksandrovych

Kaverina, Alisa Sher Akhmad

Komarov, F.F.

Partyka, J.

Pohrebniak, Oleksandr Dmytrovych

Sobol, O.V.

Tyurin, Yu.N.

Yakuschenko, I.V.

Дрозденко, Алексей Александрович

Дрозденко, Олексій Олександрович

Каверина, Алиса Шер Ахмад

Каверіна, Аліса Шер Ахмад

Погребняк, Александр Дмитриевич

Погребняк, Олександр Дмитрович

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 2, 02NFC32(3pp) (2012) 
 
 
2304-1862/2012/1(2)02NFC32(3) 02NFC32-1  2012 Sumy State University 
Structure, Properties and Element Composition of Alumina Coatings, Obtained by Micro-Arc 
Oxidation Method 
 
A.D. Pogrebnjak1,*, O.V. Sobol2, F.F. Komarov3, A.Sh. Kaverina1,†, Yu.N. Tyurin4, I.V. Yakuschenko1, 
A.A. Drozdenko1, J. Partyka5 
 
1 Sumy State University, 2, Rymsky Korsakov Str., 40007 Sumy, Ukraine 
2 Kharkov Technical University, 21, Frunze Str., 61002 Kharkiv, Ukraine  
3 Belarusian State University, 4, Nezavisimosti Ave., 220030 Minsk, Republic of Belarus 
4 The E.O. Paton electric welding institute of the NAS of Ukraine, 11, Bozhenko Str., 03680 Kyiv-150, Ukraine 
5 Lublin University of Technology, 38A, Nadbystrzyska Str., 20-618 Lublin, Poland 
 
(Received 10 July 2012; published online 06 August 2012) 
 
Coatings of aluminium oxide Al2O3 were obtained by micro-arc oxidation under different conditions of 
deposition. They were analysed by such methods as: positron annihilation spectroscopy (PAS), Rutherford 
backscattering (RBS), X-ray diffraction (XRD) and scanning electron microscopy with microanalysis (SEM 
with EDS). Investigated samples showed good adhesion to the substrate, low concentration of nanopores in 
the bulk. Content of amorphous phase in the coating was about 20 vol.%, and metastable -Al2O3 - Al2O3 
phases about less than 10 vol.%. It was demonstrated that by varying of parameters of deposition, it is pos-
sible to control the physical – mechanical properties of obtained coatings as well as their element composi-
tion and surface morphology. 
 
Keywords: micro-arc oxidation, Al2O3, crystalline and amorphous phase, the annihilation of positrons 
 
  PACS numbers: 61.46. – w, 62.20.Qp, 62.25. – g 
 
 
                                                          
* alexp@i.ua 
† mixifox@mail.ru  
1. DESCRIPTION OF METHOD OF PREPARING 
OF COATINGS 
 
Micro-arc oxidation method of depositing coatings 
features high productivity and cost-effectiveness. 
Obtained coatings have good physical-mechanical 
properties, but often contain pores (from 0.5 to 2 vol.%) 
and uncontrolled impurities from the solution in which 
the oxidation is carried out. The thickness of obtained 
oxide coatings depends on the electric field and can be 5 
– 1000 μm [1, 2]. The physical basis of the method is 
described in works [3-6]. 
Technological parameters of coatings deposition are 
shown in table 1 below. 
 
Table 1 – Parameters of the aluminium samples exposed to oxidation 
 
Number of 
samples 
 
Modes of samples’ oxidation with voltage source 
300 V 400 V 500 V 400 V 
el. cur-
rent, А 
time of oxidation, min. 
el. cur-
rent, А 
time of 
oxidation, 
min. 
el. cur-
rent, А 
time of oxi-
dation, min. 
el. cur-
rent, А 
time of 
oxidation, 
min. 
1 2→0 1 1.5→0 30 3→0 1 0.2→0 5 
2 2→0 2 2→0 25 1.5→0 1 0 5 
3 2→0 5 1.5→0 30 3→1 10 0 3 
Number of 
samples 
The square of the sample in 
the electrolyte, in mm 
Thickness of the 
plate before the 
oxidation, in mm 
Thickness of the 
sample after the 
oxidation, in mm 
 
1 13×15 2.82 2.865 
2 8×15 1.45 1.51 
3 10×15 1.45 1.5 
 
2. RESULTS AND DISCUSSION  
 
Fig. 1 shows images of surface of obtained coatings 
(fig. 1, a, c, e) and its cross sections (fig. 1, b, d, f). Im-
ages were made using scanning electron microscope, at 
magnification of 1000 and 500 times. Fig. 2 shows 
fragments of diffraction patterns obtained from sam-
ples with coatings, obtained under different technologi-
cal parameters of deposition. Curve 1 indicates, that 
content of Al2O3 of crystalline phase with hexagonal 
lattice ( -Al2O3) nearly 60 vol.%, with rhombohedral 
lattice (α-Al2O3) about 35 vol.%, and with cubic lattice 
( -Al2O3) less than 3 vol.%. For curve 2 formation of 
amorphous phase (halo in the range of angles of 20-40 
deg.), about 10 vol.% was discovered. Content of Al2O3 
crystalline phase with hexagonal lattice is about 10 
vol.%, with rhombohedral lattice about 60 vol.%, and 
with cubic lattice – nearly 10 vol.%. 
Judging by the curve 3 (halo is at angels of 20-40 
deg.), the coating has great concentration (about 20  
 A.D. POGREBNJAK, O.V. SOBOL, F.F. KOMAROV, ET AL. PROC. NAP 1, 02NFC32 (2012) 
 
 
02NFC32-2 
 
 
Fig. 1 – SEM images of the surface (a), (c), (e) and cross section (b), (d), (f) 
 
vol.%) of amorphous phase, content of Al2O3 crystalline 
phase with hexagonal lattice is nearly 24 vol.%, and with 
rhombohedral lattice about 70 vol.%, and with cubic lat-
tice – almost 6 vol.%. All results are shown in table 2, 
from which follows, than oxygen concentration is about 
60 at.%, but concentration of Al, depending of deposition 
mode is significantly different – for the third mode it is 
nearly 20.5 at.%, for the first and the second mode these 
values are close to 25.5  at.% and 26 at.%. at.%.  
In addition, Mg is present in the coating (about 
11%), Ca (2÷3)%, P (0.5÷3) at.%, and the rest is  related 
elements: Cu from 0.15 to 0.3 % and W 0.01 at.%. If we 
go back to results for phase content (fig. 2), it is possi-
ble to conclude, that such elements as P and Ca in coat-
ing are being part of amorphous phase, from which it is 
difficult to distinguish the contribution of the elements 
in oxide form. At the same time, the concentration of 
Mg is similar for all three modes of deposition. 
 
Table 2 – Appointment of special paragraph styles 
 
Sample 
No/ 
Element 
O Mg Al S(P) Ca Cu W 
3 62 11 20,5 3 3 0.3 0.01 
2 60 11 25,5 0.5 3 0.15 0.01 
1 60 11 26 0.5 2 0.25 0.01 
 STRUCTURE, PROPERTIES AND ELEMENT COMPOSITION OF ALUMINA … PROC. NAP 1, 02NFC32 (2012) 
 
 
02NFC32-3 
20 30 40 50 60 70
0
2000
4000
6000
8000
10000
(2
2
0
)
A
l 2
O
3
(4
4
0
)
A
l 2
O
3
(3
0
8
)
A
l 2
O
3
(1
1
6
)
A
l 2
O
3
(0
2
4
)
A
l 2
O
3
(0
0
6
)
A
l 2
O
3
(1
1
0
)
A
l 2
O
3
(1
0
4
)
A
l 2
O
3
(0
1
2
)
A
l 2
O
3
(2
1
4
)
A
l 2
O
3
(1
0
4
)
A
l 2
O
3
(1
1
3
)
A
l 2
O
3
(2
0
0
)
A
l 2
O
3
(2
2
0
)A
l
(2
0
0
)A
l
(1
1
1
)A
l
galo
(0
0
3
)
A
l 2
O
3
(1
0
0
)
A
l 2
O
3
3
2
I,
 a
.u
.
2 deg
1
Fig. 2 – Fragments of diffraction patterns of samples 
 
 
Fig. 3 – The dependence curves indentation depth vs. load on 
sample  
Results of research of mechanical properties of ob-
tained coatings showed the increase of hardness and 
elastic modulus. Fig. 3 shows the dependence curve of 
indentation depth on the load for different regimes of 
deposition. Letters M, N, L, U, E indicate the points, 
where the load was applied. 
It was decided to use method of positrons’ annihila-
tion to determine the size of nanopores. It is known, 
that in ceramic coatings Al2O3, which have ion bonds, 
formation of Ps (atom of positronium) is possible [5]. 
This atom can be localized in nanovoids. Moreover, 
using the data obtained by this method, we can esti-
mate the size of pores. For this purpose we used the set 
up for measuring lifetime of positrons (Na22 (β, γ)) at 
University of Halle, with a time resolution of 180 – 280 
ps. Measurements were carried out under room tem-
perature in air.  
We investigated three series of samples. By calcu-
lating obtained positron lifetime spectras we got the 
bulk positron lifetimes less then 200 ps. According to 
experimental works [6-8] it means that there is no for-
mation of Ps atom (which lifetime is much longer, 
about 400 ps and more). Results of these studies 
showed, that our coatings have small amount of na-
nopores and the size of nanopores varies in range from 
100 nm to 10 m. 
 
 
 
REFERENCES 
 
1. A.L. Yerokhin, X. Nie, A. Leyland, A. Metthews,  
S.J. Dowey, Surf. Coat. Tech. 122 No 2–3, 73 (1999). 
2. A.D.Pogrebnjak, Yu.N. Tyurin, Tech. Phys. 49 No8, 1064 
(2004). 
3. Yu.N. Tuyrin, A.D. Pogrebnjak, Surf. Coat. Tech. 142-144, 
293 (2001). 
4. Yu.N.Tuyrin, A.D. Pogrebnjak, Tech. Phys. 47 No11, 1463 
(2002). 
5. H.J. Zhang, Z.Q. Chen, S.J. Wang, J. Chem. Phys. 136, 
034701 (2012). 
6. H.-E. Schafer, phys. status solidi (a) 102, 47 (1987). 
7. C.H. Shek, T.S. Gu, G.M. Lin, J.K.L. Lai, Appl. Phys. A 66, 
413 (1997). 
8. G. Moya, J. Kansy, A.Si. Ahmed, et al., phys. status solidi 
(a) 198(1), 215 (2003). 
 


Structure, Properties and Element Composition of Alumina Coatings, Obtained by Micro-Arc Oxidation Method

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 2, 02NFC32(3pp) (2012)   2304-1862/2012/1(2)02NFC32(3) 02NFC32-1  2012 Sumy State University Structure, Properties and Element Composition of Alumina Coatings, Obtained by Micro-Arc Oxidation Method  A.D. Pogrebnjak1,*, O.V. Sobol2, F.F. Komarov3, A.Sh. Kaverina1,†, Yu.N. Tyurin4, I.V. Yakuschenko1, A.A. Drozdenko1, J. Partyka5  1 Sumy State University, 2, Rymsky Korsakov Str., 40007 Sumy, Ukraine 2 Kharkov Technical University, 21, Frunze Str., 61002 Kharkiv, Ukraine  3 Belarusian State University, 4, Nezavisimosti Ave., 220030 Minsk, Republic of Belarus 4 The E.O. Paton electric welding institute of the NAS of Ukraine, 11, Bozhenko Str., 03680 Kyiv-150, Ukraine 5 Lublin University of Technology, 38A, Nadbystrzyska Str., 20-618 Lublin, Poland  (Received 10 July 2012; published online 06 August 2012)  Coatings of aluminium oxide Al2O3 were obtained by micro-arc oxidation under different conditions of deposition. They were analysed by such methods as: positron annihilation spectroscopy (PAS), Rutherford backscattering (RBS), X-ray diffraction (XRD) and scanning electron microscopy with microanalysis (SEM with EDS). Investigated samples showed good adhesion to the substrate, low concentration of nanopores in the bulk. Content of amorphous phase in the coating was about 20 vol.%, and metastable -Al2O3 - Al2O3 phases about less than 10 vol.%. It was demonstrated that by varying of parameters of deposition, it is pos-sible to control the physical – mechanical properties of obtained coatings as well as their element composi-tion and surface morphology.  Keywords: micro-arc oxidation, Al2O3, crystalline and amorphous phase, the annihilation of positrons    PACS numbers: 61.46. – w, 62.20.Qp, 62.25. – g                                                             * alexp@i.ua † mixifox@mail.ru  1. DESCRIPTION OF METHOD OF PREPARING OF COATINGS  Micro-arc oxidation method of depositing coatings features high productivity and cost-effectiveness. Obtained coatings have good physical-mechanical properties, but often contain pores (from 0.5 to 2 vol.%) and uncontrolled impurities from the solution in which the oxidation is carried out. The thickness of obtained oxide coatings depends on the electric field and can be 5 – 1000 μm [1, 2]. The physical basis of the method is described in works [3-6]. Technological parameters of coatings deposition are shown in table 1 below.  Table 1 – Parameters of the aluminium samples exposed to oxidation  Number of samples  Modes of samples’ oxidation with voltage source 300 V 400 V 500 V 400 V el. cur-rent, А time of oxidation, min. el. cur-rent, А time of oxidation, min. el. cur-rent, А time of oxi-dation, min. el. cur-rent, А time of oxidation, min. 1 2→0 1 1.5→0 30 3→0 1 0.2→0 5 2 2→0 2 2→0 25 1.5→0 1 0 5 3 2→0 5 1.5→0 30 3→1 10 0 3 Number of samples The square of the sample in the electrolyte, in mm Thickness of the plate before the oxidation, in mm Thickness of the sample after the oxidation, in mm  1 13×15 2.82 2.865 2 8×15 1.45 1.51 3 10×15 1.45 1.5  2. RESULTS AND DISCUSSION   Fig. 1 shows images of surface of obtained coatings (fig. 1, a, c, e) and its cross sections (fig. 1, b, d, f). Im-ages were made using scanning electron microscope, at magnification of 1000 and 500 times. Fig. 2 shows fragments of diffraction patterns obtained from sam-ples with coatings, obtained under different technologi-cal parameters of deposition. Curve 1 indicates, that content of Al2O3 of crystalline phase with hexagonal lattice ( -Al2O3) nearly 60 vol.%, with rhombohedral lattice (α-Al2O3) about 35 vol.%, and with cubic lattice ( -Al2O3) less than 3 vol.%. For curve 2 formation of amorphous phase (halo in the range of angles of 20-40 deg.), about 10 vol.% was discovered. Content of Al2O3 crystalline phase with hexagonal lattice is about 10 vol.%, with rhombohedral lattice about 60 vol.%, and with cubic lattice – nearly 10 vol.%. Judging by the curve 3 (halo is at angels of 20-40 deg.), the coating has great concentration (about 20   A.D. POGREBNJAK, O.V. SOBOL, F.F. KOMAROV, ET AL. PROC. NAP 1, 02NFC32 (2012)   02NFC32-2   Fig. 1 – SEM images of the surface (a), (c), (e) and cross section (b), (d), (f)  vol.%) of amorphous phase, content of Al2O3 crystalline phase with hexagonal lattice is nearly 24 vol.%, and with rhombohedral lattice about 70 vol.%, and with cubic lat-tice – almost 6 vol.%. All results are shown in table 2, from which follows, than oxygen concentration is about 60 at.%, but concentration of Al, depending of deposition mode is significantly different – for the third mode it is nearly 20.5 at.%, for the first and the second mode these values are close to 25.5  at.% and 26 at.%. at.%.  In addition, Mg is present in the coating (about 11%), Ca (2÷3)%, P (0.5÷3) at.%, and the rest is  related elements: Cu from 0.15 to 0.3 % and W 0.01 at.%. If we go back to results for phase content (fig. 2), it is possi-ble to conclude, that such elements as P and Ca in coat-ing are being part of amorphous phase, from which it is difficult to distinguish the contribution of the elements in oxide form. At the same time, the concentration of Mg is similar for all three modes of deposition.  Table 2 – Appointment of special paragraph styles  Sample No/ Element O Mg Al S(P) Ca Cu W 3 62 11 20,5 3 3 0.3 0.01 2 60 11 25,5 0.5 3 0.15 0.01 1 60 11 26 0.5 2 0.25 0.01  STRUCTURE, PROPERTIES AND ELEMENT COMPOSITION OF ALUMINA … PROC. NAP 1, 02NFC32 (2012)   02NFC32-3 20 30 40 50 60 700200040006000800010000(220)Al 2O3(440)Al 2O3(308)Al 2O3(116)Al 2O3(024)Al 2O3(006)Al 2O3(110)Al 2O3(104)Al 2O3(012)Al 2O3(214)Al 2O3(104)Al 2O3(113)Al 2O3(200)Al 2O3(220)Al(200)Al(111)Algalo(003)Al 2O3(100)Al 2O332I, a.u.2 deg1Fig. 2 – Fragments of diffraction patterns of samples   Fig. 3 – The dependence curves indentation depth vs. load on sample  Results of research of mechanical properties of ob-tained coatings showed the increase of hardness and elastic modulus. Fig. 3 shows the dependence curve of indentation depth on the load for different regimes of deposition. Letters M, N, L, U, E indicate the points, where the load was applied. It was decided to use method of positrons’ annihila-tion to determine the size of nanopores. It is known, that in ceramic coatings Al2O3, which have ion bonds, formation of Ps (atom of positronium) is possible [5]. This atom can be localized in nanovoids. Moreover, using the data obtained by this method, we can esti-mate the size of pores. For this purpose we used the set up for measuring lifetime of positrons (Na22 (β, γ)) at University of Halle, with a time resolution of 180 – 280 ps. Measurements were carried out under room tem-perature in air.  We investigated three series of samples. By calcu-lating obtained positron lifetime spectras we got the bulk positron lifetimes less then 200 ps. According to experimental works [6-8] it means that there is no for-mation of Ps atom (which lifetime is much longer, about 400 ps and more). Results of these studies showed, that our coatings have small amount of na-nopores and the size of nanopores varies in range from 100 nm to 10 m.    REFERENCES  1. A.L. Yerokhin, X. Nie, A. Leyland, A. Metthews,  S.J. Dowey, Surf. Coat. Tech. 122 No 2–3, 73 (1999). 2. A.D.Pogrebnjak, Yu.N. Tyurin, Tech. Phys. 49 No8, 1064 (2004). 3. Yu.N. Tuyrin, A.D. Pogrebnjak, Surf. Coat. Tech. 142-144, 293 (2001). 4. Yu.N.Tuyrin, A.D. Pogrebnjak, Tech. Phys. 47 No11, 1463 (2002). 5. H.J. Zhang, Z.Q. Chen, S.J. Wang, J. Chem. Phys. 136, 034701 (2012). 6. H.-E. Schafer, phys. status solidi (a) 102, 47 (1987). 7. C.H. Shek, T.S. Gu, G.M. Lin, J.K.L. Lai, Appl. Phys. A 66, 413 (1997). 8. G. Moya, J. Kansy, A.Si. Ahmed, et al., phys. status solidi (a) 198(1), 215 (2003).  

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Structure, Properties and Element Composition of Alumina Coatings, Obtained by Micro-Arc Oxidation Method

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