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BOLETIN DE LA SOCIEDAD ESPA Ñ OLA DE
Cerámica y Vidrio
BOL SOC ESP CERÁM VIDR. 2015; 54(1): 37–43
Elaboration biphasic calcium phosphate
nanostructured powders
G.M.L. Dalmônico
a,
*, D.F. Silva
a
, P.F. Franczak
a
, N.H.A. Camargo
a
, and M.A. Rodríguez
b
a
Program Post-Graduation in Science and Materials Engineering, Santa Catarina State University (SC), Joinville, Brazil
b
Instituto de Cerámica y Vidrio (Consejo Superior de Investigaciones Científicas), Madrid, Spain.
* Corresponding author.
E-mail: gidalmonico@gmail.com (G.M.L. Dalmônico).
ARTICLE INFO
History article:
Received 17 December 2014
Accepted 22 January 2015
Keywords:
Synthesis
Calcium Phosphate
Hydroxyapatite
Biphasic
Biomaterial
ABSTRACT
Nanostructured calcium phosphate and biphasic calcium phosphates have been
studied and stand out as biomaterials for bone regeneration. This is due to the fact that
thesebiomaterials present bioactivity and morphological, chemical and crystallographic
similarities to the bone apatite. The aim of the present work has been the synthesis and
characterization of two calcium phosphates with Ca/P=1.5 e 1.67 as molar ratio. These
were synthesized through the chemical wet process. After synthesis, the hydrated calcium
phosphate powders were subsequently calcined at temperatures of 900 ºC/2 h providing
b-calcium phosphate (b-TCP) and hydroxyapatite (HA) powders. These powders were used
to elaborate the biphasic powders in the wt.% ratios HA/b-TCP as follows: 80/20, 20/80,
70/30 and 30/70. The method used for the elaboration of the b-tricalcium phosphate
nanostructured powder, hydroxyapatite and biphasic compositions was the attrition
milling. The nanostructured powders obtained were characterized by the scanning electron
microscopy technique, X-ray diffractometry. Infrared spectroscopy and Specific surface
using BET model.
© 2015 Sociedad Española de Cerámica y Vidrio. Published by Elsevier España, S.L.U.
This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Elaboración de polvos nanoestructurados de fosfatos de calcio bifásicos
RESUMEN
Biocerámicas nanoestructuradas de fosfato de calcio y composiciones bifásicas de fosfato
de calcio son estudiadas como biomateriales para sustitución ósea por presentar similitud
morfológica, química y cristalográfica con la apatita del hueso. Este estudio tiene como
objetivo la síntesis y caracterización de los fosfatos de calcio hidratados con razones
Ca/P = 1,5 y 1,67 molar, estas matrices han sido sintetizadas por solución-precipitación
en vía húmeda. El polvo de fosfato de calcio hidratado se calcino a una temperatura de
900 ºC/2 h para obtener matrices fosfato tricalcico-b (b-TCP) y hidroxiapatita (HAP). Estas
matrices se utilizaron para la preparación de polvos bifásicos compuestos con en % en
Palabras clave:
Síntesis
Fosfato de cálcio
Hidroxiapatita
Bifásicos
Biomateriales
0366-3175/ © 2015 Sociedad Española de Cerámica y Vidrio. Publicado por Elsevier España, S.L.U. Este es un artículo Open Acces distribuido bajo
los términos de la licencia CC BY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/4.0/).
http://dx.doi.org/10.1016/j.bsecv.2015.02.006
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38 BOL SOC ESP CERÁM VIDR. 2015; 54(1): 37–43
The material recovered from the synthesis process after
being dried in a rotary evaporator, presented itself with a
white color and granular form. These were milled in a mortar
and sived on a 100 mm mesh, providing powders of hydrated
calcium phosphates. These were calcined at a temperature
of 900 ºC during 2 h, providing the b-calcium phosphate and
hydroxyapatite nanostructured powders.
The biphasic compositions were prepared by attrition mill-
ing, which allows obtaining a better dispersion of phases dur-
ing the blending process. The mixture of the nanostructured
powders also was done an attrition mill, NETZSCH, with a
solid/liquid concentration of 50/50 wt.%in ethyl alcohol, zir-
conium spheres with a diameter of 2.5mm, 540 rpm during 1
hour, as described by Delima et al.
7
Then the colloidal suspen-
sion was dried in a rotary evaporator. The recovered material
followed the same procedure of milling in a mortar and sieved
as described previously.
In order to compare, the nanostructured powders of
b-tricalcium phosphates and hydroyapatite also were pro-
cessed through attrition milling, to evaluate the influence of
this milling process on the physical and morphological char-
acteristics of the two calcium phosphate matrices in relation
to the different biphasic compositions.
The morphological characterization studies were con-
ducted with the help of the Field Emission Scanning Electron
Microscopy (FE-SEM) technique, with a JEOL equipment (JSM-
6701F), using secondary electrons image, with a 8 mm work-
ing distance and electron acceleration voltage of 15 kV.
The x-ray diffractometry was used to identify the pres-
ent phases in the different compositions of nanostructured
powders and granulated biomaterials. The studies were
performed using a Shimadzu X-Ray Diffractometer Lab X
XRD-6000, with an anticathode in a copper tube, wavelength
l=1.54060 Å, using as a parameter a diffraction angle of 2U
with a 2º/min goniometer displacement, 40 kv voltage power,
with a 30 mA current intensity within a scanning angular
range of 15º to 65º.
The Fourier Transform Infrared Spectrometer helped
in the characterization of the nanostructured powders of
b-TCP, HA and biphasics compositions. The equipment used
was the spectrometer Perkin Elmer 100 with diminished
reflectance. The test was conducted in an interval within
4000 to 300 cm
–1
.
The BET model (Brunauer, Emmet e Teller) applied to the
isotherm obtained using the volumetric method was used to
determine the specific surface of the nanostructured powders
Introduction
Recent studies in vivo have demonstrated that calcium phos-
phates micro and nanostructurated and the biphasic composi-
tions of hydroxyapatite/b-calcium phosphate have potential as
biomaterials, in repairing defects and in the reconstruction of
bone tissue.
1-3
The interest in the nanoestructured ceramics
of calcium phosphates is associated to their interconnected
microporous microstructural characteristics, bioactivity, solu-
bility capacity, wetability and capillarity.
1,4
The nanostructured
bioceramics of calcium phosphates also offer new microstruc-
tures and nanostructures with interconnected microporosity
which promote bioactivity and better contact surface with the
adjoining tissues. These characteristics improve the adhesive
and proliferation conditions of osteoblast cells on the Surface
of grains and micropores, promoting the osteointegration and
the formation of a new bone tissue.
1,5
This study approaches the process of synthesis and char-
acterization of two nanostructured calcium phosphates:
b-tricalcium phosphate (b-TCP) and hydroxyapatite (HA),
for the subsequent elaboration of biphasic in wt.% HA/b-
TCP=80/20, 20/80, 70/30, 30/70. The results presented are
related to the morphological characterization of the nano-
structured powders, through the use of the scanning electron
microscopy (SEM) technique. The X-ray diffractometer (XRD)
was used for the crystallographic characterization of the
nanostructured powders. The infrared spectroscopy (FTIR)
helped identifying vibrational bands of the OH
–
and PO
4
3–
groups. Finally the results of the superficial area analysis by
the BET isotherm model will be presented.
Materials and methods
The synthesis was carried out by the reaction of dissolution/
precipitation, method using CaO and a solution of phosphoric
acid necessary for the formation of the different compositions
in the Ca/P ratio molar desired, as described elsewhere.
6
Calcium carbonate (CaCO
3
), LabMaster, was used with
concentration of 99% of purity, batch number 27404. The cal-
cium carbonate was calcined at 900 ºC during 3 h in order
to obtain CaO. The reagent used was the phosphoric acid,
Nuclear, with 85% concentration. The solution of acid con-
centration was prepared according to the Ca/P=1.5 and 1.67
molar ratio.
peso HA/b-TCP con las siguientes proporciones: 80/20, 20/80, 70/30 y 30/70. Los polvos
nanoestructurados de b-fosfato tricalcico, hidroxiapatita, y las composiciones bifásicas
se prepararon por molienda de atrición en húmedo. Los polvos nanoestructurados así
obtenidos se caracterizaron por microscopía electrónica de barrido, difracción de rayos X
análisis cuantitativo. Espectroscopia infrarroja y se ha determinado la superficie especifica
utilizando el método BET.
© 2015 Sociedad Española de Cerámica y Vidrio. Publicado por Elsevier España, S.L.U.
Este es un artículo Open Acces distribuido bajo los términos de la licencia CC BY-NC-ND
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
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BOL SOC ESP CERÁM VIDR. 2015; 54(1): 37–43 39
of b-TCP, HA, and biphasics compositions (in wt.% HA /TCP-
b): 80/20, 20/80, 70/30, 30/70. The equipment used to measure
the specific surface was the ASAP 2000 from Micromeritics
Instrument.
Results and discussion
During the synthesis process, the pH of the colloidal solu-
tion was monitored for 24 hours from the beginning to the
end of the synthesis. Figure 1 shows the measured curves
of the pH value for the composition Ca/P=1.5 molar (Fig.
1a) and for the composition Ca/P=1.67 (Fig. 1b). Based on
the curves, it was observed that the pH value stabilized
in about 400 min, leading to a final value of pH=5.8 for the
composition Ca/P=1.5 molar ratio and around 6.9 for the
composition Ca/P=1.67.
The results obtained from the morphological characteriza-
tion of the nanostructered powders of hydrated calcium on the
Ca/P=1.5 e 1.67 molar ratio have revealed in their micrographs,
a morphology formed by clusters of nanoparticles, smaller in
size by 50nm respectively for the two compositions Ca/P=1.5
molar e 1.67 molar, as illustrated by Figures 2a and 2b.
The results obtained from the b-tricalcium phosphate
nanostructured powders and hydroxyapatite (Figs. 3a and
3b) have revealed a microporous morphology formed by
aggregated nanoparticles. If the micrographs obtained on the
b-TCP powder are compared to the HA powder, it possible
observe that the b-TCP powder shows nanoparticles bigger to
those found for HA. This observation was also made by other
authors that have obtained b-zr|calcium phosphates from the
calcination of hydrated calcium phosphates. These explain
that the slight coalescence of the crystals of b-TCP is associ-
ated to the Ca/P molar ratio and to the interfacial kinetics
between nanoparticles.
2,6,8-12
The results found for the b-TCP and HA nanostructured
powders after the attrition milling process shows a change
of the nanoparticles surface, generated by the attrition mill,
where there was a reduction in size of the nanoparticles
when compared to the results obtained from the calcination
of nanostructured powders at 900 ºC/2 h (Figs. 4a and 4b).
This superficial change of the nanoparticles has already been
identified by other authors that have used the high energy
method of attrition milling in the development of ceramic
powders.
7,13-15
The morphological characterization obtained from the
biphasics compositions are quite similar morphology as to
those already found for the b-TCP and HA powders after
the attrition milling. In view of this, only the micrographs
obtained from the biphasics compositions 70/30 e 30/70, (Figs.
5a and 5b) are shown in this work.
12
10
8
6
0 500 1000 1500
Time (minutes)
A
pH (TCP)
pH
12
10
8
6
0 500 1000 1500
Time (minutes)
B
pH (HA)
Figure 1 – Measured curves of the pH value over time (a) Ca/
P=1.5, (b) Ca/P=1.67 (molar ratios).
Figure 2 – SEM micrographs obtained from the hydrated calcium phosphate powders, (a) Ca/P=1.5 molar and (b) Ca/P=1.67
molar.
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40 BOL SOC ESP CERÁM VIDR. 2015; 54(1): 37–43
Figure 3 – SEM micrographs obtained on the powder of (a) b-TCP and (b) hydroxyapatite.
Figure 4 – SEM micrographs obtained on the powder (a) b-TCP after attrition milling and (b) HA after attrition milling.
Figure 5 – SEM micrographs obtained over biphasic powder (a) 70/30 and (b) 30/70 wt.% after attrition milling.
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BOL SOC ESP CERÁM VIDR. 2015; 54(1): 37–43 41
The X-ray diffractometry of the hydrated nanostructured
calcium phosphates (Figs. 6a and 6b), shows the presence
of low crystalline apatite (Ca
3
(PO
4
)
2
.H
2
O) typical hydrated
calcium phosphate phase, obtained by the wet process
(Ca
3
(PO
4
)
2
.H
2
O), for the two compositions Ca/P=1.5 and 1.67
(molar ratio). This result has also been identified by other
authors that have used the wet method for the synthesis of
calcium phosphates.
2,6,16
The diffractograms of the powders after the calcination at
a temperature of 900 ºC/2 h (Figs. 7a and 7b) shows the pres-
ence of b-TCP in the rhomboedral crystalline system with
main diffraction plan [021] for the composition Ca/P=1.5 and
the HA stoichiometric phase in the hexagonal system with
main diffraction plan [211] for the matrix Ca/P=1.67 molar.
The diffractograms obtained from the powders of the com-
position b-TCP and HA after attrition milling (Figs. 8a and 8b),
show the same crystalline structures as previously observed
for the composition b-TCP e HA before the attrition milling
process (Figs. 7a and 7b).
A slight reduction in the intensity of the phases of the
most intense peaks was observed if compared to the diffrac-
tograms for the composition b-TCP and HA, before and after
the attrition milling process, as shown in Figures 7a-7b, 8a-8b
and previously explained.
The results obtained from the x-ray diffractometry on the
biphasics powders show the presence of representative peaks
from the b-TCP and HA phases for all the biphasic powder
compositions, where only a slight variation in the intensities
of the peaks between the compositions, which is related to
the presence of the concentration of phases in % in each two
phase powder composition.
The results obtained by the infrared spectrometry (FTIR)
over the nanostructured powders b-TCP and HA are shown in
Figures 9a and 9b. The spectra shown the vibrational bands
corresponding to PO
4
3–
around 1090 cm
–1
, 1020 cm
–1
, 940 cm
–1
,
600 cm
–1
, 560 cm
–1
, 420 cm
–1
, referring to the OH
–
groups, over
the spectrogram obtained from HA in around 3560 cm
–1
, 1740
cm
–1
and 630 cm
–1
, indicating that the nanostructured powder
is formed by HA as observed in the DFR charts represented
and identified by other authors.
17-20
The results obtained over the two phase nanostructured
powders have revealed in their FTIR spectra the same vibra-
tional bands of the PO
4
3–
e OH
–
(Fig. 9c) groups. These have
already been observed for the b-TCP e HA powders. These
results indicate that the two phase powders are really com-
posed by b-TCP e HA, as also observed in the results obtained
by the X-ray diffractometry (Figs. 7a and 7b).
Table 1 shows the results of the specific surface on the
calcium phosphates nanostructured powders after attrition
milling b-TCP, HA and bihasic compositions: in wt.% HA/
b-TCP=80/20, 20/80, 70/30, 30/70. The results show higher
values for the HA matrix, getting to 11.6 m
2
/g. The presence
of a larger concentration of the matrix b-TCP in the biphasic
compositions was observed, which lead to a slight reduction
200
150
100
50
20 30 40 50 60
2Ɵ
A
+ Ca
3
(PO
4
)
2
H
2
O
I (CPS)
200
150
100
50
20 30 40 50 60
2Ɵ
B
+ Ca
3
(PO
4
)
2
H
2
O
Figure 6 – Diffractometer X-ray chart obtained on the
hydrated calcium phosphate powders Ca/P=1.5 (a) and 1.67
molar (b).
800
600
400
200
0
20 30 40 50 60 20 30 40 50 60
2Ɵ
A
[021]
TCP-β
I (CPS)
2Ɵ
B
[211]
HA
Figure 7 – X-ray diffractometer recorder chart obtained on
the powder of the compositions b-TCP (a) and HA (b).
800
600
400
200
0
800
600
400
200
0
20 30 40 50 60
2Ɵ
20 30 40 50 60
2Ɵ
A
[021]
TCP-β
ATRITOR
ATRITOR
B
HA
Figure 8 – X-ray diffractometer recorder chart obtained over
powders of the matrix b-TCP (a) and HA (b) after attrition
milling.
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42 BOL SOC ESP CERÁM VIDR. 2015; 54(1): 37–43
80
40
0
80
40
0
80
40
0
3500 3000 2500 2000 1500 1000 500
3500 3000 2500 2000 1500 1000 500
Wavenumber (cm
-1
)
A
TCP
T (%)
B
C
HA
70/30
Figure 9 – FTIR spectograms obtained on the matrix b-TCP
(a), (b) hydroxyapatite and biphasics compositions (c) 70/30%.
of the specific surface for these compositions, if these results
are associated to the matrix HA. This small variation in the
specific surface between the compositions can be explained
by the slight variation of the morphological characteristics,
previously observed throught the micrographs represented
by Figures 3 a and 3b, where there is a thin morphology of
nanoparticles for the HA matrix.
Conclusion
The development of nanostrutured calcium phosphates pow-
ders is a current research topic and has generated new per-
spectives in the development of biomaterials for bone tissue
replacements. These new biomaterials can be used in ortho-
pedics, in traumatology and dentistry, as a matrix element in
filling defects and regeneration of bone tissue.
The literature shows that the developments of b-tricalcium
phosphates hydroxyapatite nanostructured powders and
biphasics compositions have two basic targets: improve physi-
cal characteristics as open porosity, superficial area of grains
and microporosity, and biomaterial solubility.
Morphological characterization has shown that the matrix
HA has a morphology that is more refined than the matrix
b-TCP. It has been observed that this fine morphology of the
HA matrix has also influenced the values of the superficial
area obtained by BET, showing slightly superior superficial
area, for the compositions with a larger concentration of the
HA. These fine morphologies found can be a potential in the
development of biomaterials for bone replacement and leads
to innovative results in the microstructural level of micropo-
rosity and of surface grains and microporos.
The physical characterization has revealed that the nano-
structured powders are formed basically by crystalline HA
and b-TCP phases. This result has shown that the nanostruc-
tured powders are formed by the constituent parts of the
bone tissue. This will allow the development of microporos
biomaterials with differentiated characteristics of superfi-
cial area of grain and microporous in relation to conventional
biomaterials, which could generate an innovation in the near
future in surgical procedures for bone tissue repairing and
reconstitution. The results obtained by BET show that the
nanostructured powders offer nanometric morphologies with
a superficial area that promises wettability, adherence and
cellular proliferation in these surfaces.
The results found in this work are encouraging and show
that the calcium phosphates nanostructured powders can
offer biomaterials with close architectures as to those of the
bone structure, which can be a differential among the bio-
materials of bone tissue replacement and repairing in a near
future for biomedical applications.
Acknowledgments
The financial support of the Higher Education Personnel
Training Coordination (CAPES-BRASIL) and Institute Ceramic
and Glass (MAT2013-48426-C2-1R).
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