r.1Jdit-M»|:i.-iJ
! — ADVVVCES IN N'LT^-RAL StziEs'CES NANOSCIENCE VSO SWITCCHNOLOGV
Ad> Na, Sc. N » o „ , . N m o , „ h „ o l 4 , : i H 3 ) 0 3 5 0 1 4 (9pp, dotiai0S»/;(M..-6:(,:V4/3/0350l4
Impact of physical and chemical parameters on the hydroxyapatite nanopowder synthesized by chemical precipitation method
Thi Thu Trang Pham', Thu Phuong Nguyen', Thi Nam Pham', Thi Phuong Vu', Dai Lam IVan^ Hoang Thai'
and Thi Mai Thanh Dinh'
• Inslilute for Tropical Technology, Vietnam Academy of Science and Technology. 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam
E-mail [email protected] and dmihanh@ ill.vast.vn Received 12 December 2012
Accepted for publication 3 June 2013 Published 1 July 2013
Online at stacks.iop.org/ANSN/4/0350l4 Abstract
In this paper, the synthesis of hydroxyapatite (HAp) nanopowder was studied by chemical precipitation method at different values of reaction temperature, settling time, Ca/P ratio, calcination temperature, (NH4)2HP04 addition rate, initial concentration of CaCNO^)! and {NH4)2HP04 Analysis results of properties, morphology, structure of HAp powder from infrared (IR) specira, x-ray diffraction (XRD), energy dispersive x-ray (EDX) spectra and scanning electron microscopy (SEM) indicated that the synthesized HAp powder had cylinder crystal shape with size less than 100 nm, single-phase structure. The vanation ofthe synthesis conditions did not atfect the morphology bul affected the size of HAp crystals.
Keywords: chemical precipitation, nano hydroxyapatite, Ca/P ratio, diameter of crystal Classification number: 4.04
1. Introduction connecring the bone, orthopedic or repairing bone, coaring on metals and alloys for bone splint screw [6-8]. There are many Hydroxyapatite (HAp) wilh compositions of stoichiometnc methods to synthesize HAp such as sol-gel, ultrasonic, spray Caio(P04)6(OH): IS the main inorganic component of natural drying, micro-emulsion, mechano-chemistry, hydrothermal ' bones and teeth (accounts for about 65 wt%, of the bone), and chenucal precipitarion [9-18]. Some methods require It IS widely used in the biomedical field because of high processing temperature, high raw material cost and excellent biocompalibility. high bioactivity. non-toxicity and complex synthesis process. Chemical precipitation method non-inflammatory behavior and non-immunogenic propenies has advantages which include simple equipment, low cost and
• HAp has rapid bone regeneration ability and creates a ability to obtain nanosized HAp powder with large quantity direct bond with the host living bone without intermediate and high purity. All specific applications of HAp depend on connective tissue [1-5]. It is often used in powder form for the main characterisiics such as Ca/P ratio, crystal size and calcium supplement drug, ceramic and composite form for morphology of HAp [19]. Nano HAp has greater specific surface area, smaller particle size, more uniform distribution
1
Contenl from ihis work may be used under ihe terms of than micro HAp, thereby, better resorption and biological the Creative Commons Aiiribuiion .1.0 licence. Any further ^ctivitv Nano HAp promotes the adhesion and proliferation of••'iihuiion nl this work musi mainiain ailnbuiion to the auihoris) and the ' . . , .. •. •
"11^ "f Ihc work, joumal ciiauon and DOI bone cells and increases the accumulation and the deposition 2041-6262/1.1/0.15014+09$.'.1 00 I ^ 2013 Viemam Academv alSL-icncc & I'.'^.hniilogy
Adv Nai. Sci.: Nanosci. Nanolechnol 4(2013)035014
Functional groups . ( c m - ' ) [21]
u(cni"') {experiment)
(OH) 3572 3576
Table 1.
(Poj- 1087 1046 1113 1032
Wave nutnbers foi the functiona (POj-)
962 968
S (OH)
630 628
(po;-) 601 571 602 570
groups
^4
(poj- 474 463
of HAp.
(HOH) 1640 1638
(CO;-) 1450 1420 1461 1391
P - O H 870 874
of bone on the surface of the bioceramic matenal [20].
Therefore, controlling panicle size, morphology and phase composition of HAp is very important for biomedical applications.
In this paper we present some results of HAp nanopowder synthesized by chemical precipitation method and the effects of synthetic conditions, i.e. reaction temperamre, seiriing rime, Ca/P ratio, calcination temperature, (NH4)2HP04 addition rate and reaclant concentration on morphology, structure and particle size.
2. E x p e r i m e n t a l
Hydroxyapatite was synthesized by chemical precipitation method using Ca{NO_i)7 solution at the vanous Ca(N0,i)2 concentrations 0 25, 0.5, 1 M in water. The (NH4)2HPOj concentration was vaned to obtain the Ca/P molar ratio of 1.5, 1,67 and 3.33. Its solution was added dropwise into Ca(N0;t)2 solulion with addition rate of 1, 2 and 5 m l m i n ~ ' , During the process, the pH value of the solulion was maintained at 10 by using the concentrated NH.i solution. The reaction was conducted under a stimng rale of 800 rpm at the different temperatures (25. 40, 60 and 80 C). The obtained precipitate was aged for 2 h followed by settling for 0 , 2 , 15,21 and 24 h.
The .settled precipitate was centrifugally washed at a rate of 4000 rpm, then dried at 80 C for 24 h, calcined al 400 and 800 C for 4 h (Nabertherm N20/H, potential 40 V, frequency 50Hz, power 65kW, cuiTcnl 14A) and ground wilh an agate mortar (2 3 g per 60 mm) to obtain white HAp powder
The charactenstic functional groups of HAp were idenlified by Fourier transform infrared (FTIR) spectroscopy (Nicolet 6700 spectrometer, usmg KBr pellet technique in the r a n g e 4 0 0 0 - 4 0 0 c m ~ ' . with a resolution of 8 c m " ' ) .
The microstructure of HAp powder was characterized by field emission scanning electron microscopy (FE-SEM) combined with energy-dispersive x-ray spectroscopy (EDX) (S4800 of Hitachi, Japan). The phase purity and crystallinity of the HAp powder were analyzed by x-ray diffraction (XRD) (Siemens D5000 Diffractometer, CuK„ radiation ( A = 1,54056A). step angle of 0.030^ scanning rate of 0 042 85 s - ' . and 29 in range of 15-80^ The average crystallite size along c-direction of HAp powder was calculated from (002) reflection in XRD pattern, using Scherrer's equation
0 9X { cos 6*
where D (nm) is crystallite size. A (nm) is the wavelength of Ihe .\-ray radiation (CuK„), 9 (rad) is the diffraction angle and B is the full-width at half-maximum (FWHM) ofthe peak along (002) direction.
4000 3 5 0 0 3 0 0 0 2 5 0 0 2 0 0 0 1500 1000 500
\ \ a \ e n u m b e r ( c i i i ') Figure 1, IR spectra of HAp powder synihesized at pH 10, (NHj)2HP04 addiUon's rate 1 mlmin"', at different lempcraiur' 3 . R e s u l t s a n d d i s c u s s i o n s
3.1. Effect of reaction temperature
The reaction temperature was an important factor that could affect the morphology, the phase structure and the crystallinity ofthe synthesized HAp powder. Figure 1 and table 1 show the FTIR spectra and the bonds of the functional groups of the HAp powder synihesized using Ca(N03)2 and (NH4)2HP04 solulion at the different reaction temperatures. The IR specira of all synihesized samples showed the characteristic peaks corresponding to HAp The absorption bands al wave numbers of 1114, 1025, 962,4, 602.2, 570.7 and 469,6 cm-' were associated with the charactenstic of P04~ group, whereas, the bands at 3575 and 633.6 c m - ' were attributed to OH' group. The absorption band at 874 c m ~ ' was assigned to the P-OH bond. The bands at 3431 and 1637.9cm"' correspond to absorbed water. The absorption of water (al 3431cm-') was quite strong, indicating the presence of a large amount of water in the product. Besides, the bands of CO^" group al 1461 and 1385.6 c m " ' were barely observed, which indicated no significant presence of C0^~ in HAp powder.
The XRD specira of the HAp powder synthesized al lh«
various temperatures are shown in figure 2. By comparing the XRD patterns of synthesized samples with the standanJ data in table 2 [22], the characteristic peaks of HAp weit identified and there are no characteristic peaks conesponding to calcium carbonate phases or calcium phosphate phases.
The strongest peak intensity of the HAp sample at 2f* = 31.14" (con-esponding lo 2?^ ^ 31.76' of the standard HAp) was of the (211) crystal plane and the other peak at -" = 25.85 conesponded to the ((K)2) crystal plane, which were the two most characteristic peaks of HAp. Besides, the other
Ad.- Nal- Set Nanoici Nanoiectinol 412013)035014 TTTPliani^to/
T^blc 2. The parameters of 20. {hid) and relative inlensities of HAp.
(002) (211) (112) (300) (202) (310) (222) (213) (0O4) 25.85 31.76 32.16 32.8
NIST 2910a [22] Relal ve intensities 20 0
59 32.13
59 32.85
30 49 41 Expenmental peak Relative intensitie'
'"•<: 'J4'^'WJJ»'^'LW-W'-.
Figure 2. XRD spectra of HAp powder .synthe.sized al pH 10, INH4).HP04 addition's rate 1 ml nun"', al different temperatures.
Table 3. The ciystal diameter of HAp powder synthesized at different temperatures.
Temperature Crystal diameler (°C) (nm)
characteristic peaks with less intensity were of the (112) and (300) crystal plane. The results indicated lhat the synthesized HAp powder had cry.stalline shape and single phase structure The HAp crystal diameter calculated from the Scherrer equafion showed that the crystal diameler increa.sed from 25 lo41nm on increasing the reacrion temperature from 25 lo 80 C (table 3). Increasing the temperature results in fa.ster motion of molecules, so there was an increased chance of iheir colliding with each other, the HAp particles concentrated to form larger particles. At 25 °C, the HAp particle had the
•-mallest diameter.
Figure 3 and table 4 show the SEM images and average panicle si^e of the HAp powder synihesized at the different lemperaiures. The synthesized HAp was of cylinder shape, the crystal size increased with increasing temperature, which was in agreement with the x-ray results. The crystal diameler varied from 14 to 35 nm, the crystal length varied from 29 to 94 nm.
3-2. Effect of settling time
After aging, the HAp suspension was settled in order to Mabilize and develop crystals, so it could strongly affect the
^^yMal size
The IR spectra of HAp samples prepared at 25 C, pH = 10 with various settling limes 0, 2, 15, 21 and 24h are shown in figure 4. By companng these IR results with data in table 1, it was found that the obtained HAp had all characteristic peaks of HAp slandard.
The XRD spectra of HAp powder prepared at different settling times are represented in figure 5. The charactenstic diffraction peaks of HAp are indicated. The results showed that HAp synthesized at different settiing time had crystal structure, single phase. However, HAp crystal diameter decreases when the settling time increases from 0 to 24 h (table 5), and 15 h is the optimal time so lhat HAp crystalhzarion process is stabilized after the aging penod.
The SEM images of HAp powder prepared at settling times from 0 to 24 h are presented in figure 6 Al different settling times, all obtained HAp had a cyUnder shape with a reduced size when settling time increased from 0 to !5 h. if settling time increases continuously up i o 2 l and 24 h, cry.stal size can increase (table 6) Therefore, the suitable time for crystal stability is 15h.
3.3 Effect of Ca/P ratio
The phase diagram of the system Ca0-P2Os-H2O showed that when the Ca/P ratio changed from 3/2 to 10/3, the HAp powder could contain many impunties. depending on reaclani excess of (NH4)2HP04 (ratio of 3/2) or Ca(N0-i)2 (ratio of 10/3). The IR spectra of HAp powder synthesized at three Ca/P ratios are shown in figure 7 By companng these IR results uith data in table 1. it was found thai the obtained HAp had all the charactenstic peaks of HAp In addition, the XRD results indicated the charactenstic diffraction peaks of HAp, and no other phases of calcium phosphate were detected (figure 8). This result is different from those reported in literature Although the same synthetic route was applied, the detailed procedure was different. In this study, we synihesized HAp powder by dropping slowly (NH4)2HP04 solution into Ca(N0.i)2 solution, so the Ca/P ratio did nol affect the purily of the HAp powder, the residual (NH4);HP04 or Ca(N03)2 would be removed by centrifugation. The presence of other phases could only appear when the synthesis process was conducted by dropping simultaneously two solutions of (NH4)2HP04 and Ca(N03)2 into the reactor at thegi\en (\i/P ratio. From XRD spectra, at 20 = 25.85 , according to ihr Schener's equation, the HAp crystal diameter at the Ca/P ratit of 10/6 was 25 nm, smaller than those obtained at t\\o Ca/P ratios of 3/2 and 10/3 (table 7).
Figure 9 presents EDX spectra and table 8 introduces the percentages of the elements in the HAp powder synthesized at three Ca/P ratios: 3/2, 10/3 and 10/6. The characteristic peaks con-esponding to Ca, O. P of HAp pow der are indicated In addition, the other peaks corresponding to C and Si were
Adv. Nat. Sei • Nanosci Nanolechnol. 4 (2013) 035014
r
Figures. SEM images of HAp powder synthesized at pH ^ 10, (NHt):HP04 addition's rate Iml/min, vanous temperaOires: (a) 25 °C, (b) 40"C,(c)60"Cand(d)80<"C
Table 5. The crystal diameler of HAp prepared at different settling limes
Figure 4. The IR spectra of HAp prepared at 25 C, pH = i 0 with various seldmg times 0, 2, 15, 21 and 24 h.
• • ' i • * ' ' i i L . '
Figure 5. X-ray spectra of HAp prepared al different .seiriing limes.
Table 4. The average crystal sizes of HAp powder at the vanous lemperaiures
Temperaiure t 0}
25 40 60 80
Average crystal size(nm)
19x29 1 4 x 3 0 .15 X 94 2 8 x 8 0
observed due lo the CO^ infection in the samples and Si impurities in starting matenals.
From the atomic percentages of the elements in HAp samples (table 8), the Ca/P and Ca/P/0 ratios could be
Settling time (h)
HAp crystal diameler (nm)
Table 6. The average crystal of HAp was calculated from SEM images.
Seiriing time (h)
0 2 15 21 24
Average crystal size (nm)
1 9 x 3 3 1 9 x 2 9 1 4 x 3 6 2 3 x 5 4 2 2 x 5 0
calculated (table 9). Comparing with theoretical Ca/P/0 ralio, il can be estimated that all three samples contained excess oxygen, probably due to the presence of adsorbed CO^" in the HAp powder. The experimental Ca/P ratio value of Ihe HAp synthesized al Ca/P ratio of 10/6 was in good agreement with the theoretical value, indicating the similanty of the obtained HAp powder to natural bone ( C a / P = 1.667). For this reason, the Ca/P ralio in the starting material of 10/6 should be chosen.
The average crystal size of the FLAp powder synthesized at various initial Ca/P ratios is presented in figure 10 and table 10.
3.4. Effect of calcination temperature
In order lo invesrigate the effect of treatment temperature, the dried HAp powder samples were heated in air al 400 and 800 C for 4 h. The IR spectra of HAp samples dned al 80 C and then healed at 400 and 800 X are shown in iigure 11.
The peaks al 1631 and 3 4 2 5 c m " ' corresponding to the bending vibration of the H - O - H absorbed in the HAp crysub decreased while the other characteristics peaks of HAp w « nol changed when increasing calcinarion temperature.
The XRD spectra with the characteristic diffraction peaks of HAp confirmed the crystalline shape and single jAa**
purity of the obtained HAp powder (figure 12). Imponanilv.
the amount of CO2 absorbed on Ihe surface of HAp was iW significant.
Tlie data in table 11 shows that the crystal size increased with increasing calcination temperature. According to I'Sj-
Uv Nal Sci:Nanosci Nanolechnol 4(2013| 035014 T T T Pham et al
— ,.4. ^^ M , . - — ^ ^ m
^^^^^^^^^^^^^^H
Figure 6. SEM images of HAp prepared at different setilmg umes: (a) Oh, (b) 2h, (c) 15 h, (dj 21 h, (e) 24h.
4000 3500 3000 2500 2000 1500 1000 500 Wavenumber (cm 1 Figure 7. The IR specira of HAp prepared at 25 C, pH = vanous Ca/P raiios: (a) 3/2; (b) 10/6 and {c) 10/3.
Tahit 7. The
DUOS
:rysial diameter of HAp synthesized al differem Ca/P Crystal diameter
(nm) 10/6 10/3
higher heating temperature would lead to an increase in lattice parameters of HAp, so the volume of the hexagon increases and the crystal size changes. In addition, under the effect of lemperalure, the nanocry.stals lend to agglomerate in order lo form the larger crystals Therefore, appropnate calcination lemperature is 80 C
is. Effect of{NHi)2HPOi addition rate
^ adding rate of (NH4):HP04 affects the morphology, yniclurc and size of formed HAp crystals. Namely, according
S_^J>J *'^J',AAv'^"^y>«*A/''V„.AA, j-J-J''^''J'vjj'''' ^''•J*-..-JJ'' A...^v^
5 i « ^
20 30 40 50 60 70 80 29 ItletjrceM
FiRure 8. X-tay .spectra of HAp samples prepared using vanous Ca/P ratios (a) 3/2; (b) 10/6 and Ic) Wf}.
Ca/P 3/2
10/6
10/3
Table 8. Elemenlary a alio Element
Vr weighi 9e atom
% weighi 9/ atom
% weight Vl atom
C 3.44 6 40 3.88 7.20 3,47 6 40
lalyses ir 0 44.3B 6 1 8 2 43.76 60,90 45.13 62.48
H A p samples Sl 0 15 0.12 0.23 0 18 0,19 0 15
P 16.70 1201 16.54 I I 89 16 40 1173
Ca 15 33 1964 35.59 19.83 34.81 l ' ) 2 4
to well-known collision theory, the larger the lNH|i:MP04 adding amount, the greater die frequency of reactant collisions, so larger crystals were created. Figure 13 presents the IR spectra of the samples synthesized with the dropping rales of 1. 2 and S m l m i n " ' In general, all IR spectra of the samples have similar shapes and the specific peaks corresponding to functional groups in the HAp molecule.
Adv. Nat Sci. Nanosci, Nanotechnol. 4 (2013) 035014 3500
3000 a 2500 S 2000
fisoo
Inten
§
500 P
0 p
t Si
c| fl
0 2 Ca
Si
lj h
Ca4 6 8 1 3500 3000 i 2500 5 2000 f 1500 1 1000 500
Ca
P
JJ 1
) 2 I" , 1
1
Ca4 6 8 IC Energy (keV)
(a)
Energy (IceV) (b) 3500
3000 1 2500 g 20Q0 3 1500
•g 1000 500
o
Jl
Ca
P
,
s,
J r a
Energ}' llteV)1
Ca (C)Figure 9. Energy dispersive s-ray spectra of HAp samples synUiesized at Ca/P ratios, (a) 3/2; (b) 10/6 and (c) 10/3.
(a) (b) (c) Figure 10. SEM images of HAp powder synthesized at different initial Ca/P ratios: (a) 3/2, (b) 10/6, (c) 10/3
Table 9. Ca/P and Ca/P/0 ratios m HAp powder theoretical (7^ and experimenlal (£) values
Table 11. Crystal diameter of HAp heated at different temperatuna- Initial Ca/P Ca/P
ratio (7) 1 5
1 67 1-67 3 33
Table 10. SEM based Ca/P ralio 3/2 10/6 10/3
Ca/P {E) 1635 1.667 1.64
Ca/P/0 (7) 10/6/26
Ca/P/0 (£) 10/6 1/315 10/ 6/ 30 7 10/6 1/32 5 calculated HAp average particle size
Average panicle size (nm) (diameler x length)
2 0 x 4 7 19x29 2 1 x 5 9
Calcination temperature (^C)
Crystal diameler of HAp (nm) 80
400 800
Table 12. Crystal diameter of HAp synthesized at different
(NH4)2HP04 addinon rates. ^ _ ^ (NH4)2HP04 addition Crystal diameter of
rate (mlmin"') HAp (nm)
1 2 5 "
2 26 5 27
Figure 14 and table 12 introduce XRD spectra and XRD-calculated crystal diameters, respectively. In general.
XRD pattems of the HAp samples had the same shapes and had only the charactenstics peaks of the HAp molecule. From this table, it was found that while (NH4)2HP04 adding rate
increased five times, the crystal diameter did not increase significantly, only from 25 lo 27 nm.
To confirm the XRD results, the morphology of HAp powder was further analyzed by SEM images. Figure 15 ai"
table 13 present the SEM images and SEM-based calculawl
Adv NaL Sci.: Nanosci Nanolechnol 4 (20131035014 T T T Ptiam c( al
4000 3500 3000 2500 2000 1500 1000 500 Wavenumber (cm I
Figure 11. The IR spectra of HAp samples calcmcd ai differcnl lemperaiures.
« H A p
ijjJJ'i ^UAA^*^'" ^U—wW^'-V
^'^KJ^J^^' V' ^^'i\^'^^'A...^^,^K^M^,
iSJliJ'iLKvJi;';^^
20 30 40 50 60 70 i 26 (degrees)
Figure 12. X-ray specira of HAp samples calcined al different lemperaiures
Table 13. Calculated average particle size from SEM images.
(NH4)2HP04 addilion Average parlicle rale (ml min"') size (nm)
19x29 19x40 19x42 lalilt J4. The crystal diameler of HAp synihesized al vanous
"N'O.t. conceniralions.
('i>iii.cnlralioii of HAp crystal C.iiNOj; iMi diameler(nm) 0.25
0.5 1
iverage crystal sizes HAp crystal had a cylinder shape
•^'tli Ihe same diameter of about 19 nm. However, when '!*iH4l.HP04 adding rale increased, crystal length increased
4000 3500 3000 2500 2000 1S00 1000 500 Figure 13, IR specira of HAp powder synihesized al differem (NHj|;HPOj addilion's rates I. 2 and 5 ml min '.
;;ii'i,A'i'i''vJv^'''i^''-A*'v^^'*w^\
50 60 70 80
Figure 14. X-ra\ specira i.l HAp p.mdcr s> nihcM/c.l al dilkTci (NHaiiHPII, .iddiiumsrales 1, 2 and 5 ml mm ' Table IS. The average crystal size were calculated from SEM images al different miUal conceniralions of CalNOO: solution
Concentration of Average crystal Ca(NO.,);(M) sizeinm) 0.25 18x31 0.5 19 X 29
I 18x4,')
from 29 to 42 nm. These results allowed to conclude that the increase in (NH4)2HP04 adding rate could lead to increasing HAp crystal length
3.6. Effect of reactant concent rcUion
Figure 16 presents ihe IR spectra of ihe HAp powder obtained at various initial concentrations of Ca(.N03)i solution It could be found thai the IR spectra ofthe HAp samples had the same shapes and Ihe characteristic peaks ofthe functional groups nl HAp are shown.
Figure 17 and table 14 demonstrate the XRD spectra and the crystal diameter, respectively, of HAp samples synthesized at different reactant conceniralions. From the XRD spectra, il was found lhat ihe synihesized HAp had a crystal shape
,\cl^ N M Sd. Nar
\'- : I . •; .
•HAp
0.5M
20 30 40 50 60 70 80 28 (decrees)
Figure 17. X-ray spectra of the HAp samples synthesized al different inilial concentraUons of Ca(N03)2 solulion: 0.25,0,5 and Figure 15. SEM images of HAp samples synihesized at vanous
(NRij.HPOj addnion rate: (a) 1 ml min"', (b) 2 ml mm"' and (c) 5 m l m i n " ' .
4000 3500 3000 2500 2000 1500 Wavenumber (cm')
Figure 16. IR specira i<( the HAp .samples s\ nihcsized at different initial concenlraUons of Ca(NOi); solution 0,25. 0 5 and 1 M.
Figure 18. SEM images of the samples at different initial concentrations of Ca{N0,)2 soluUon, (a) 0.25 M, (b) 0.5 M and (c)
and single phase structure. The crystal diameter was in a range from 19 to 25 nm, XRD analyses also demonstrate a weak effect of reaclani concentralion (in the above-mentioned range) on the HAp crystal diameter.
Figure 18 and table 15 show the SEM images and average cry.stal size of HAp calculated from the SEM images The reactant concentration had no effect on the morphology
of HAp powder. As for the SEM resuhs, il could be found that A c k n o w l e d g m e n t the HAp crystals had cyhnder shape with the crystal diameler
varying from 18 to 19 nm and the crystal length varying from 29 lo 45 nm
structure, cylinder shape with size less than 100 nm, Ca/P ratio of 1,67, corresponding lo the ratio in the natural bones and teeth. Although preliminary, these results make HAp powder an interesting alternative for bone replacement and other biomedical applications such as calcium food supplement.
Funding of this work was provided by Vietnam Ministry of Science and Technology project (grant No 49/2012/HD-NDT).
4. Conclusion
HAp powder was synihesized by chemical precipitation method using calcium nitrate, diammonium phosphate solution as reactants, and ammonia as adjusting agent ( p H ^ 10). The obtained results showed that the synthetic conditions were important in controlling the quality, shape and size of the HAp powder The HAp powders had single-phase crystal
and Cahmh A :<*'>>>
References
[1] Cengiz B, Gokce Y, Yildiz N Colloids. Sutf A. 322 29
[2] Jadalannagari S, More S, Kowshik M and Ramanan S R 2011 Mater Sci Eng C 31 1534
[3] Wang P, Caihong. Gong H, Jiang X, Wang H and Li K 2010 Powder Technol. 203 315
Adv Nat. Sci: Nanosci Nanotechnol 4(2013|035014 TTTPhani«o/
(4] Falhi M H. Hamfi A and Mortazavi V 2008 J. .Matir Process IH] Zhang X and Vecchio K S lOOlJ.Crysi CroiuA 308 133 Technol. 202 536 [15] Mobasherpour 1, Heshajin M S, Kazemzadeh .\ and Zakeri M (5J Kusiini E and Sontang M 2012 Radial. Phys. Chem. 2007 J. Alloys Compounds 430 330
81 118 [161 Gouvenia D S, Bressiani A H A and Bressiani J C 2006 Mater.
[6] Haberko K, Bucko M M, Brzezinska-Miecznik J. Pyda A and Sn. Forum 530-531 593
Zarehski J 2006 J. Eur. Ceram. Soc. 26 537 [17] Liu C, Huang Y. Shen W and Cui J 2001 Biomateriah 11 301 [7] Garcia C. Garcia C and PaucarC 2012/«org. Chem. Commun. [18] Hien V D, Quoc Huong D and Ngoc Bich P T 2007 VietnamJ
20 90 Chem. 45 21 (in Vietnamese)
[8] Quoc Huong D and Ngoc Bich P T 2007 Vietnam J. Chem. [19] Swain S K. Dorozhkin S V and Sarkar D 2012 Maier Sa Eng.
45 147 (in Vietnamese) C 32 1237
|9] Kumar A R and Kalainathan S 2010 Physica B 405 2799 [20] Kalita S J and.Verma S 2010 Maier Sci. Eng C 30 295 [101 GopiD, Indira J, Kavitha L, Sekar M and Mudali U K 2012 [21] Fuenies G, Hernandez Y, Campos Y, Lopez N. Rojas M L.
Speclrochim. Acta A 93 131 Peon E. Alnurall A and Delgado J A 2008 Latin Am Appl.
[11] Wang A-J, Lu Y-P, Zhu T-F, Li S-T and Ma X-L 2009 Powder Res. 38 105-12
Technol. 191 1 [22] Wallers R L 2008 Calcium Hydroxyapatite (Certificate of [12) lanidilokkul S, Tanlhapanichakoon W and Anahsis. Standard Reference Material 2910a)
Boonamnuayvittaya V 2007 Colloids. Surf A 296 149 (Gaiihersburg, MD- Insiimte of Standards and Technology.
[13] Nasiri-Tabrizi B. Honarmandi P, Ebrahimi-Kahrizsangi R and NIST Measurement Ser\'ices Division National) Honarmandi P 2009 Mater Uu 63 543 www.nisl.gov/snn
