The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites
The influence of mechanochemical treatment of submicrocrystalline sintered corundum on the structure of bioglass composites containing α-Al2O3 and CaO—SiO2—P2O5 glasses was examined in the context of the possibility to form hydroxyapatite after being immersed in the simulated body fluid solution. Me...
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Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України
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irk-123456789-207532011-06-05T12:03:23Z The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites Staniewicz-Brudnik, B. Szarska, S. Gamrat, K. Получение, структура, свойства The influence of mechanochemical treatment of submicrocrystalline sintered corundum on the structure of bioglass composites containing α-Al2O3 and CaO—SiO2—P2O5 glasses was examined in the context of the possibility to form hydroxyapatite after being immersed in the simulated body fluid solution. Measurements of specific surface area and size and X-ray analysis of submicrocrystalline sintered corundum were conducted. Bioglass composites were obtained by placing submicrocrystalline sintered corundum grains in the CaO—SiO2—P2O5 sol system, gelling and sintering at 800 °C. The specimens were examined under a scanning electron microscope before and after immersion in the simulated body fluid solution for 24 and 120 h. Using the VCS algorithm, calculations of thermodynamic stability of compounds occurring in these bioglass composites were carried out, verifying the X-ray analysis. 2008 Article The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites / B. Staniewicz-Brudnik, S. Szarska, K. Gamrat // Сверхтвердые материалы. — 2008. — № 6. — С. 40-48. — Бібліогр.: 16 назв. — англ. 0203-3119 http://dspace.nbuv.gov.ua/handle/123456789/20753 621.9.047.666.792 en Сверхтвердые материалы Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України |
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Получение, структура, свойства Получение, структура, свойства |
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Получение, структура, свойства Получение, структура, свойства Staniewicz-Brudnik, B. Szarska, S. Gamrat, K. The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites Сверхтвердые материалы |
| description |
The influence of mechanochemical treatment of submicrocrystalline sintered corundum on the structure of bioglass composites containing α-Al2O3 and CaO—SiO2—P2O5 glasses was examined in the context of the possibility to form hydroxyapatite after being immersed in the simulated body fluid solution. Measurements of specific surface area and size and X-ray analysis of submicrocrystalline sintered corundum were conducted. Bioglass composites were obtained by placing submicrocrystalline sintered corundum grains in the CaO—SiO2—P2O5 sol system, gelling and sintering at 800 °C. The specimens were examined under a scanning electron microscope before and after immersion in the simulated body fluid solution for 24 and 120 h. Using the VCS algorithm, calculations of thermodynamic stability of compounds occurring in these bioglass composites were carried out, verifying the X-ray analysis. |
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Article |
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Staniewicz-Brudnik, B. Szarska, S. Gamrat, K. |
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Staniewicz-Brudnik, B. Szarska, S. Gamrat, K. |
| author_sort |
Staniewicz-Brudnik, B. |
| title |
The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites |
| title_short |
The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites |
| title_full |
The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites |
| title_fullStr |
The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites |
| title_full_unstemmed |
The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites |
| title_sort |
influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites |
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Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України |
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2008 |
| topic_facet |
Получение, структура, свойства |
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http://dspace.nbuv.gov.ua/handle/123456789/20753 |
| citation_txt |
The influence of mechanochemical treatment of sintered submicrocrystalline corundum substrates on the structure of bioglass composites / B. Staniewicz-Brudnik, S. Szarska, K. Gamrat // Сверхтвердые материалы. — 2008. — № 6. — С. 40-48. — Бібліогр.: 16 назв. — англ. |
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Сверхтвердые материалы |
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2025-07-02T21:16:34Z |
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2025-07-02T21:16:34Z |
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| fulltext |
www.ism.kiev.ua; www.rql.kiev.ua/almaz_j 40
UDC 621.9.047.666.792
B. Staniewicz-Brudnik (Kraków, Poland)
S. Szarska (Wroclaw, Poland)
K. Gamrat (Kraków, Poland)
The influence of mechanochemical treatment
of sintered submicrocrystalline corundum
substrates on the structure
of bioglass composites
The influence of mechanochemical treatment of submicrocrystalline
sintered corundum on the structure of bioglass composites containing α-Al2O3 and
CaO—SiO2—P2O5 glasses was examined in the context of the possibility to form hy-
droxyapatite after being immersed in the simulated body fluid solution. Measurements
of specific surface area and size and X-ray analysis of submicrocrystalline sintered
corundum were conducted. Bioglass composites were obtained by placing submicro-
crystalline sintered corundum grains in the CaO—SiO2—P2O5 sol system, gelling and
sintering at 800 °C. The specimens were examined under a scanning electron micro-
scope before and after immersion in the simulated body fluid solution for 24 and 120 h.
Using the VCS algorithm, calculations of thermodynamic stability of compounds oc-
curring in these bioglass composites were carried out, verifying the X-ray analysis.
Key words: mechanochemical treatment, submicrocrystalline sintered
corundum, bioglass composite, hydroxyapatite, SBF, SEM, VCS algorithm.
Introduction. Current medicine makes use of numerous synthetic
reconstructed biomaterials ranging from simple tissue replacements to complicated
prostheses [1, 2]. Biomaterials can be grouped according to:
— chemical composition (metallic, polymer, ceramic, composite);
— microstructure (dense, macroporous, microporous);
— biocompatibility (biocompatible materials — some metals, resorbable poly-
mers and bioactive materials, inert ceramics; materials with limited biocompatibil-
ity — the majority of metals, alloys, polymers; toxic materials).
On account of the numerous advantages (biocompatibility, a high hardness, a
low wear) ceramic biocomposites play an important role in designing and produc-
ing implants and in tissue engineering as medication media. From the beginning of
the seventies, experimental and clinical examinations regarding tissue reactions to
composite corundum materials have been conducted. Hulbert et al., investigating
porous materials, described the sequence of load transfers after corundum implan-
tation in bone tissue [3]. They were trying to answer the question of whether the
surrounding tissue is permeable to aluminum. Arentowicz et al. [4] used absorption
atomic spectroscopy to measure the content of different elements in the bone sur-
rounding the implant and did not detect aluminum. This is contradictory to the
conclusions of Lewandowska-Szumieł [5], who reported the presence of Al in the
tissue adjacent to the corundum implant. Ogushi et al. [6], when examining the
osteogenic activity of human bone marrow cells on the surface of corundum ce-
ramics in vitro, demonstrated that cells of the bone marrow diversify toward bone
© B. STANIEWICZ-BRUDNIK, S. SZARSKA, K. GAMRAT, 2008
ISSN 0203-3119. Сверхтвердые материалы, 2008, № 6 41
cells (osteoblasts), which leads to mineralization of the bone tissue. Barrere ob-
served and interpreted changes on the surface of corundum and TiO2 after immer-
sion in the simulated body fluid solution (SBF) [7]. There is little information on
an electric charge which arises on surface layers of glassy biocomposites as a result
of reaction with the tissue fluid and electromagnetic radiation. Szarska et al. [8—
10] examined the influence of external factors (deformation, ionizing radiation,
low temperatures) on surface transport processes in bioglassy composites.
Ślósarczyk et al. [11] examined the effect of addition of calcium and magnesium
phosphates as microstructure modifiers of bioactive multifunctional ceramic mate-
rials. The influence of CaO and MgO on physico-mechanical properties of the
corundum biomaterials was studied by Jaegermann et al. [12, 13].
The glasses of the CaO— SiO2—P2O5 are characterized by a much higher bio-
logical activity compared to metals, carbon and oxides, such as corundum, which,
being biologically inert, in turn is far more biocompatible. These glasses have both
appropriate chemical composition and surface activity to enable the physiological
environment to react selectively with some of their constituents to combine the
surface with live tissue.
Below the effect of mechanochemical treatment (high-energy milling) of sin-
tered submicrocrystalline corundum on the microstructure of a biocomposite
formed is discussed.
Experimental Procedures
Input materials. Submicrocrystalline sintered corundum. Submicrocrystalline
sintered corundum grains were supplied by the 3M Company.
This material is sintered α-Al2O3 having an ultradispersed structure obtained by
transforming the sol into the magnesia-modified gel. This results in a specific
structure of short Al2O3 needles separated by microthreads of MgAl2O4. The mate-
rial properties were as follows [14]:
— density — 3.9317 g/cm3;
— microhardness — 17—21 GPa;
— compressive strength — 22 MPa;
— fracture toughness — approx. 4 MPa⋅m1/2;
— Young’s modulus — 362 GPa.
The corundum grains of the input granulation were milled for 5, 10, and 15 h in
a Fritsch Pulverisette 6 planetary ball mill in ethanol using agate balls. The total
mass of the submicrocrystalline sintered corundum grains was 50 g and the ball to
powder ratio was 10:1. This mechanochemical treatment (high-energy milling)
increases the material specific surface area, changes the material structure, generat-
ing dislocations and point defects, which favor microarea reactivity. A small quan-
tity of powder was taken from the mill chamber after milling during 5, 10, and 15 h
to make analyses.
Measurements of specific surface area were made with a Micrometric ASAP
2010 apparatus using the physical adsorption of nitrogen method at 77 K. Analysis
of the size composition was made in Micromeritics Sedigraph 5.100 X-ray Ana-
lyzer using 0.5 % sodium pyrophosphate solution as a sedimentation liquid. X-ray
examination of cubitron after milling was conducted in a Philips diffractometer
with a cobalt source in 2θ range of 10—90°. SEM examinations of the milled sub-
microcrystalline sintered corundum as well as of the bioglass composites were
carried out under a Jeol 64 LV scanning microscope in a low vacuum.
The CaO—SiO2—P2O5 glass system, the gel. The chemical composition of the
glass system is given in Table 1.
www.ism.kiev.ua; www.rql.kiev.ua/almaz_j 42
Table 1. Glass composition, mol%
SiO2 CaO P2O5
58 33 9
To prepare the solutions for immersion of corundum grains, the following con-
stituents were employed:
— tetraethoxysilane (TEOS) Si(OC2H5)4;
— triethyl phosphite (TEP) OP (C2H5)3;
— calcium nitrate tetrahydrate Ca(NO3)2*4H2O;
— water (H2O) as a catalyst of hydrolysis.
The order in which the chemicals were added and times of mixing [2, 3] are
shown in Fig. 1. The basic composition of hydrolysate with the addition of
Ca(NO3)2*4H2O and OP (C2H5)3 was stirred with a magnetic stirrer.
2n HNO
3
H
2
O
TEOS
OP(C
2
H
5
O)
3
Ca(NO
3
)
2
4H
2
O
Solution
Wet gel
60 min
60 min
Fig. 1. The scheme of preparing input materials for bioglass composite syntesis by Jones.
Simulated body fluid. SBF is a synthetically produced physiologic saline solu-
tion imitating natural plasma, in which a balance is maintained between concentra-
tion of H+ and OH– ions, with the pH being approximately 7.3 (Table 2) [5]. Action
of the SBF solution on bioactive gel leads to the formation of hydroxyapatite,
which facilitates the formation of a permanent bond with the bone.
ISSN 0203-3119. Сверхтвердые материалы, 2008, № 6 43
Table 2. Ion concentration, mM, in the human body blood plasma (NBF)
and simulated body fluid (SBF)
Na+ K+ Ca+
Mg2+ Cl– HCO3
– HPO4
– SO4
2–
NBF 142.0 5.0 2.5 1.5 103.0 27.0 1.0 0.5
SBF 142.0 5.0 2.5 1.5 147.0 4.2 1.0 0.5
The biocomposite. As-received and milled corundum grains were added to the
hydrolysate in the ratio 1 : 0.028 and left under ambient conditions to be gelled,
which occurred after 7 to 14 days depending on the quantity of water used. The
gels were heater-dried at 60 °C for three days and then heated in an electric furnace
at 800 °C for 2 h. During the heat treatment the remaining water (in the form of
steam [4]) and gaseous organic compounds (principally CO2) were removed. Clo-
sure of xerogel pores also occurred. Biocomposite samples were immersed in SBF
at 37 °C, held there for 24 and 120 h, and then examined under the scanning elec-
tron microscope. Thermodynamic calculations of the phase equilibria were based
on the VCS algorithm.
Results and discussion. The specific surface area (SBET) of submicrocrystalline
sintered corundum grains grew by a factor of two, from 5.17 to 10.95 m2/g, as a
result of the mechanochemical treatment (Table 3, Fig. 2). This effect is illustrated
Table 3. Results of size analysis and specific surface area
of submicrocrystalline sintered corundum after milling
Milling time, h Fraction
15 10 5
Below 20 μm 100.0 100.0 100.0
15 μm 99.6 100.0 95.1
10 μm 97.1 97.2 81.3
8 μm 94.9 94.1 71.5
6 μm 91.1 87.2 59.7
5 μm 87.1 81.1 52.7
4 μm 80.2 72.0 44.4
3 μm 69.0 59.5 35.2
2 μm 53.0 44.5 26.1
1.5 μm 43.9 36.2 21.4
1.0 μm 33.1 26.8 15.7
0.8 μm 27.8 22.1 12.8
0.6 μm 20.9 16.6 9.5
0.5 μm 16.4 13.4 7.6
0.4 μm 11.2 9.8 5.7
0.3 μm 4.8 5.6 3.1
Median, μm 1.83 2.35 4.66
Mode, μm 2.82 3.61 8.68
Grain surface area, m2/g (by Stoke’s) 1.509 1. 286 0.870
Specific surface area SBET, m2/g 10.95 8.74 5.17
www.ism.kiev.ua; www.rql.kiev.ua/almaz_j 44
in the size distribution plots (population curves): multimodal, curves 1 (5-hour
milling) and 3 (15-hour milling), and monomodal, curve 2 (10-hour milling), and
of mode and median values. After 5-hour milling the three dominant populations
were: below 0.5, between 0.5 and 1.5, and between 1.5 and 20 μm. After 10 h the
dominant population was between 0.3 and 10 μm, and after 15-hours milling, there
were two dominant populations: 0.3—1 and 1—15 μm, respectively. The largest
effect of milling was observed after 10 h, since after 15-hour milling agglomeration
of the smallest grains was evident.
X-ray radiography of the input material revealed the presence of alpha,
gamma, and kappa phases of Al2O3, Al12Mg17 and MgAl2O4. Additionally, quartz
(SiO2) appeared during milling, originating from agate balls. The polymorphic
changes from α-Al2O3 to κ-Al2O3 as a result of mechanochemical treatment were
observed.
Calculations of crystal sizes according to the Scherer equation showed reduc-
tion of sizes (Table 4) from 128.9 to 71.7 nm, which was also confirmed by scan-
ning electron microscopy (Figs. 3, 4). Samples of bioglass composites (after gel-
ling and heat treatment) exhibited a macroscopically visible gradient structure
(Fig. 5). For composites with unmilled grains, two layers were clearly visible: a
lower layer, which was blue and contained grains of the submicrocrystalline sin-
tered corundum, and an upper layer, which was white and constituted the bioglass
(Figs. 6, 7).
100 μm
Fig. 3. SEM image of submicrocrystalline
sintered corundum, 100×.
10 μm
Fig. 4. SEM image of submicrocrystalline
sintered corundum after 15-hour milling,
2500×.
100 10 1
Equivalent spherical diameter, μm
0
10
20
30
40
50
60
70
80
90
100
1
2
3
m
as
s
%
Fig. 2. The effect of the milling time (5 (1), 10(2), 15 (3) h) on the grain size reduction–
population curves.
ISSN 0203-3119. Сверхтвердые материалы, 2008, № 6 45
Table 4. X-ray identification of α-Al2O3 before and after milling
Milling time, h Before milling
5 10 15
Al2O3 (corundum) Al2O3 (corundum) Al2O3 (corundum) Al2O3 (corundum)
γ-Al2O3 γ-Al2O3 γ-Al2O3 γ-Al2O3
Θ-Al2O3 Θ-Al2O3 Θ-Al2O3 Θ-Al2O3
κ-Al2O3 κ-Al2O3 κ-Al2O3
Al12Mg17 Al12Mg17 Al12Mg17 Al12Mg17
MgAl2O4 MgAl2O4 MgAl2O4 MgAl2O4
SiO2 (quartz) SiO2 (quartz) SiO2 (quartz)
Crystal size of α-Al2O3, nm
138.3 128.9 85.9 71.7
100 μm
Fig. 5. SEM image of the CaO—SiO2—P2O5
bioglass.
Fig. 6. Photograph of the bioglass composite
with the unmilled submicrocrystalline sintered
corundum.
500 μm
a
500 μm
b
Fig. 7. SEM image of the bioglass composite with the submicrocrystalline sintered corundum
(unmilled), a top (a) and a pit (b) of the sample.
Scanning electron microscopy showed that the finer the submicrocrystalline co-
rundum, the more uniform was the composite (Figs. 8, 9). A biocomposite sample
of unmilled grains in the lower part (defined as the surface) contained principally
Al, O and traces of Ca, P and Si. In the upper layer calcium, phosphorous, silicon,
traces of aluminum and carbon, which confirmed the possibility of forming calcites
were visible. The “upper side” of all the composites showed the clearly defined
crackins, the main reason for which was an increase in the capillary pressure of the
liquid in gel pores and an increase in the surface tension of the liquid—steam sys-
tem. As the capillary pressure gradient developed in the sample volume due to the
www.ism.kiev.ua; www.rql.kiev.ua/almaz_j 46
limited transport of liquid accumulated in pores, the unequal stress distribution
resulted in cracking the material.
Fig. 8. Photograph of the bioglass composite with the submicrocrystalline sintered corundum
after 10-hour milling.
5 μm
a
5 μm
b
Fig. 9. SEM image of the bioglass composite with the submicrocrystalline sintered corundum
(after 10-hour milling), a pit (a) and a top (b) of the sample.
So that crystallization of hydroxyapatite could occur on the biocomposite sur-
face, certain conditions had to be satisfied:
— the solution in direct contact with the biocomposite surface should be satu-
rated with calcium ions in relation to hydroxyapatite; in the case of glass, the
source of calcium ions was the glass phase;
— surface charge should be negative, silica gel, which forms on the biocompo-
site surface, possesses such a charge;
— in the surface layer there should be areas favorable for nucleation of hy-
droxyapatite; hydroxyl groups are such places;
— crystallization of hydroxyapatite on the material surface is only possible
when Si—OH groups are present in the surface layer. This in turn is possible when
the heat treatment temperature does not exceed 900 °C;
— crystallization of hydroxyapatite, which favors maintenance of sterile condi-
tions in the process of making the samples.
Various combinations of calcium and phosphorus oxides provide a large variety
of calcium phosphates, which can be classified according to the type of the phos-
phate anion: ortho-(PO −3
4 ), meta-(PO −
3 ), pyro-(P2O −4
7 ), and poly-(PO3) −n
n . In the
Ca(OH)2—H3PO4—H2O ternary system [8] there are eleven known non-ion-
substituted calcium orthophosphates with the Ca/P molar ratio within 0.5—2.0.
Molar ratios indicate: 1.0 — dicalcium phosphate dehydrate; 1.2—2.2 — amor-
phous calcium phosphate; 1.5—1.67 — calcium deficient hydroxyapatite, and 1.67
— hydroxyapatite [15].
ISSN 0203-3119. Сверхтвердые материалы, 2008, № 6 47
SEM observations demonstrated
that a 24-hour immersion in SBF
resulted in the formation of calcites
and various types of calcium phos-
phate (Ca/P molar ratio ≤ 1). After a
5-day immersion, on the surfaces of
biocomposites containing unmilled
and milled for 10 h cubitron grains,
hydroxyapatite appeared, as was
evidenced by the Ca/P molar ratio
of 1.5—1.7 in selected points (Fig.
10) In the remaining samples, most
probably, calcium phosphate crys-
tallized on the biocomposite sur-
face.
The chemical stability of bonds
between submicrocrystalline sin-
tered corundum and components of
the CaO—SiO2—P2O5 glass system
was examined by calculating the
thermodynamic potential by the
VCS algorithm method which con-
siders the stability of all reaction
products [16]. Calculation of equi-
librium was conducted for glass
composites at 310 K (37 °C) at
atmospheric pressure. Molar ratios
of components were adopted as
their actual values. The method
used was of minimization of the
thermodynamic potential of the
whole mixture. Such calculations do
not require specifying the reactions
and their number, through which
the system reaches equilibrium; it
only requires specifying the sub-
stances, which could exist in the
reaction, but did not. Out of 46
possible reaction products, only
Al2O3, Al2SiO5, Ca3(PO4)2 and
CaAl2Si2O8 turned out to be ther-
modynamically stable. The pres-
ence of them was confirmed by X-
ray analysis (Table 4).
Conclusions
Based on the investigation carried out so far the following can be concluded:
The degree of size reduction of submicrocrystalline sintered corundum has a
significant influence on the uniformity of bioglass composites.
Mechanochemical treatment (high-energy milling) for 5, 10 and 15 hours
changed the chemical composition of submicrocrystalline sintered corundum.
Some of α-Al2O3 grains after 10-hour milling are transformed to kappa Al2O3 (from
20 μm
1 2 3
a
b
Fig. 10. SEM image of the bioglass composite with
the unmilled submicrocrystalline sintered corun-
dum, five days in the SBF solution, 1000×.
www.ism.kiev.ua; www.rql.kiev.ua/almaz_j 48
1 to 6 vol%). Further milling did not change the submicrocrystalline sintered co-
rundum.
Gradient bioglass composites can be produced by immersing corundum grains
in the sol of CaO—SiO2—P2O5 glass system, gelling and sintering at 800 °C. But
the finer the submicrocrystalline sintered corundum grains, the more homogenous
the composite.
Calculations of the thermodynamic stability of bioglass composites based on
the VCS algorithm showed that only four compounds (Al2O3, Al2SiO5, Ca3(PO4)2,
CaAl2Si2O8) out of 46 possibilities were stable. The presence of them was con-
firmed by the X-ray analysis.
Immersion of samples of bioglass composites in the SBF solution for 24 h
caused the appearance of calcites. After immersing the samples in the SBF solution
for 5 days hydroxyapatite appeared on composite samples of two types. Those
were unmilled grains of submicrocrystalline sintered corundum and samples milled
for 10 h. The latter were of Ca/P molar ratios of 1.5, 1.7, 1.6, 1.7 at different points
on the surface.
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Institute of Advanced Manufacturing Technology Received 11.04.08
Institute of Physics, Wroclaw University of Technology
Institute of Chemistry, Kraców University of Technology
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