A Review of Chromatographic Characterization Techniques for Bio
Micro Structural Characterization of Bio Medical Titanium
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Transcript of Micro Structural Characterization of Bio Medical Titanium
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Microstructural characterization of biomedical titanium
oxide film fabricated by electrochemical method
Han-Jun Oha, Jong-Ho Leeb, Yongsoo Jeongc, Young-Jig Kimd, Choong-Soo Chie,*
aDept. of Materials Science, Hanseo University, Seosan 352-820, South KoreabDept. of Chemistry, Hanseo University, Seosan 352-820, South Korea
cKorea Institute of Machinery and Materials, Changwon 641-010, South KoreadDept. of Metallurgical Engineering, Sungkyunkwan University, Suwon 440-746, South KoreaeSchool of Advanced Materials Engineering, Kookmin University, Seoul 136-702, South Korea
Available online 18 November 2004
Abstract
For an application as biomedical materials of high performance with a good biocompatibility, the anodic TiO2 layer on Ti substrate has
been fabricated by electrochemical method, and the characteristics of anodic titania film have been investigated. X-ray diffraction (XRD)
results indicate that the titania film formed in acidic electrolyte with additives is mainly composed of anatase structure containing rutile. From
the analysis of chemical states of the anodic film using X-ray photoelectron spectroscopy (XPS), phosphorus and sulfur were observed in the
anodic film, which were penetrated from the electrolyte into the oxide layer during anodic process. From the result of biological evaluation in
simulated body fluid (SBF), the anodic TiO2 film was effective for bioactive property.
D 2004 Elsevier B.V. All rights reserved.
Keywords: Anodizing; Titanium oxide; X-ray diffraction; Photoelectron spectroscopy
1. Introduction
In biomedical implants and dental fields, titanium has
been widely utilized for excellent corrosion-resistance and
biocompatibility. However, Ti and its alloys are non-
bioactive after being implanted in bone. Thus, for further
improvement in biocompatibility the various implant sur-
face modifications have been investigated. These surface
modifications have included sandblasting [1], acid etching
[2], combination of sandblasting and acid etching [3], sol
gel technique [46], deposition of Ti coatings using plasmaspraying, and deposition of calcium phosphate or hydrox-
yapatite (HA) coatings [711]. In this study, for the purpose
of improvement in biocompatibility the anodic TiO2 layer
on Ti substrate was fabricated by electrochemical method in
acidic solution, and the characteristics of anodic titania film
has been examined. And the biological evaluation of the
anodic TiO2 films formed in acidic solution was performed
in a simulated body fluid.
2. Experimental
A commercial grade pure titanium (99.6 wt.%) was used
for anodization. The titanium specimens with dimensions of
8100.5 mm were mechanically polished and degreasedin n-hexane for 6 min, and then washed and dried. After the
pretreatment, the titanium oxide films for application ofbiomaterials were prepared by anodizing at a constant
voltage of 180 V in 1.5 M H2SO4, 0.3 M H3PO4 and 0.3 M
H2O2 mixture solution. For the comparison of bioactive test,
the etched titanium without anodization was prepared by
pickling in 30 vol.% nitric acid and 3 vol.% of hydrofluoric
acid. The microstructures of anodic TiO2 film and thickness
were observed using a scanning electron microscope
(JSM5410/EDS). Identification of the phase of anodic
TiO2 films was carried out using an XRD (Philips,
PW1710). The analysis of chemical states by X-ray photo-
0257-8972/$ - see front matterD 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.surfcoat.2004.10.029
* Corresponding author. Tel.: +82 2 910 4666; fax: +82 2 910 4320.
E-mail address: [email protected] (C.-S. Chi).
Surface & Coatings Technology 198 (2005) 247 252
www.elsevier.com/locate/surfcoat
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electron spectroscopy (XPS, PHI 5700) was performed at an
accelerating voltage of 15 kV and current of 30 mA with amagnesium Ka radiation.
After the anodic oxidation, the TiO2 films were soaked in
50 mL of simulated body fluid (SBF) with ion concentration
(Na+: 142, K+: 5.0, Mg2+: 1.5, Ca2+: 1.5, Cl: 147.8,
HCO3: 4.2, HPO42: 1.0, and SO4
2: 0.5 mM) nearly equal
to human blood plasma, which was developed by Kokubo et
al. [12]. The SBF was prepared by dissolving reagent grade
chemicals of NaCl, KCl, NaHCO3, K2HPO4, MgCl2, CaCl2and Na2SO4 into distilled water, and buffered at pH 7.40
with tris (hydroxymethyl) aminomethane and 1 M HCl at 37
8C. After the immersion in a SBF solution at 37 8C in the
normal incubator for 5 days, surface of sample was observed
by SEM.
3. Results and discussion
3.1. Characteristics of anodic TiO2 film
To obtain the anodic TiO2 layer an anodic constant
current of 35 mA/cm2 was applied on titanium surface, and
then the anodic potential was increased slowly. When the
anodizing potential reached a value of 180 V, anodizingprocess was carried out at a constant potential of 180 V.
During anodizing process the variations of surface mor-
phology of titanium is exhibited in Fig. 1. At the early stage
of anodization the anodic TiO2 layer was uniform and less
porous than that of anodic film formed at higher potentials.
At higher potential than 90 V the anodizing process was led
to increased gas evolution and also frequent sparking
phenomena. At the same time, anodic pore cell structure
began to nucleate at the surface, and the irregular arrays of
cell structure have gradually changed to regular morphol-
ogy. Under constant potential of 180 V the pore cell size
increased with the anodic time The anodic titanium oxide
film formed by electrochemical method at 180 V for 30 min
in 1.5 M H2SO4, 0.3 M H3PO4 and 0.3 M H2O2 mixture
solution is shown in Fig. 2a. The analyses of pore
distribution were performed using Image analyzer (Image
Proplus, Media Cybernetics), and thickness was observed
using SEM, and the results are shown in Fig. 2b.
Fig. 2a shows the variation of pore diameters of TiO2 cell
structure with anodic time. At an early stage of anodization
the diameters of the pores are smaller and distributions are
Fig. 1. Surface morphologies of anodic TiO2 films with anodizing time at 180 V in 1.5 M H2SO4, 0.3 M H3PO4 and 0.3 M H2O2 mixture solution.
Fig. 2. Electron micrograph of cross sectioned TiO2 film (a) and the relationship between average pore diameter and anodic film thickness with anodizing time
at 180 V in 1.5 M H2SO4, 0.3 M H3PO4 and 0.3 M H2O2 mixture solution (b).
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more scattered. As can be seen in Fig. 2a, the growth of pore
diameter of cell structure with anodic time increases rapidly
in the beginning stage of anodizing, which indicates average
pore diameter of 0.32 Am for 5 min, 0.56 Am for 30 min,
and then growth of pore diameter increases linearly.
Therefore the cell structure on anodic oxide film revealed
a normal frequency distribution by gradual growth of earlygenerated micropores, and the thickness of TiO2 film
increased linearly with anodic time. The pore diameter
and layer thickness of anodic TiO2 increase with anodic
time, and the anodic film thickness is dependent on anodic
time with a rate of 3.15102 Am/min at 180 V.Fig. 3 shows the X-ray diffraction (XRD) patterns of the
anodic titania film with anodic time. The anatase phase with
rutile revealed in XRD results in early stage of anodization.
And titanium peak observed in pattern is due to the titanium
substrate. As the anodic reaction increased, the X-ray peak
intensities of anatase gradually increased, and the crystalline
phase of anodic films was predominantly anatase. It is wellknown that the TiO2 has three crystal structures such as
anatase, rutile and brookite, and the anatase TiO2 is more
reactive than the rutile [13]. Fig. 4 shows XPS wide scan
spectrum of an anodic TiO2 layer formed at 180 V for 30
min. From the analysis of narrow scan of XPS spectrum, the
chemical states of O-1s, P-2p, S-2p, and Ti-2p were
identified in the forms of P2O5, SO42, TiO2 (anatase,
rutile), Ti2O3. Therefore, during anodization in the electro-
lyte of H2SO4, H3PO4 and H2O2 mixture solution, it is
found that P and S were incorporated into the anodic oxide
layer. And also it can be described that P migrates inward
across the TiO2 layer in the initial stage of anodization, and
S in the later stage of it. Fig. 5 shows depth profile of anodic
titania obtained from the XPS analysis. In Fig. 5, the
phosphorus is infiltrated throughout the oxide films, while
sulfur is detected in oxide films close to the electrolyte/
oxide interface. This suggests that during anodization the
inward diffusion of phosphorus or phosphate ion in
electrolyte to the oxide/electrolyte interface is dominant
rather than that of sulfur.
3.2. Effect of electrolytes
The anodic oxide films on titanium are formed by
anodization in electrolyte, for which anodic reaction in
combination with electrical-field driven metal and oxygen
ion diffusion lead to the formation of an oxide film at the
anode surface, which can be written as:
Ti4ox 4H2OaqfTiOH4ox 2H2
fTiO2xOH2x 2 xH2O
In these reactions the structure and morphology of anodicoxides can be varied by controlling the process parameters,
such as electrolyte composition. To observe the effects of
electrolytes on the microstructure of anodic TiO2 film, the
anodization was performed at 180 V for 30 min in various
electrolyte solutions. The electrolytes were 1.5 M H2SO4solution, 1.5 M H2SO4/0.3 M H2O2 mixture, 1.5 M H2SO4/
0.3 M H3PO4 mixture, and 1.5 M H2SO4/0.3 M H3PO4/0.3
M H2O2 mixture solution.
Fig. 3. X-ray diffraction pattern of the TiO2 film with anodizing time.
Fig. 4. XPS spectrum of anodic TiO2 formed at 180 V for 30 min in 1.5 M
H2SO4, 0.3 M H3PO4 and 0.3 M H2O2 mixture solution.
Fig. 5. Depth profile of anodic TiO2 film formed at 180 V for 30 min.
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Fig. 6 shows microstructures of anodic titania prepared
at 180 V for 30 min in various solution. The anodic TiO2films formed in 1.5 M H2SO4 solution and 1.5 M H2SO4/
0.3 M H2O2 mixture represent smaller cell structures than
those formed in 1.5 M H2SO4/0.3 M H3PO4 mixture and
1.5 M H2SO4/0.3 M H3PO4/0.3 M H2O2 mixture.
However, considerable changes in the surface morphologyare not seen only with addition of hydrogen peroxide as
additive.
From the results of thickness measurement the average
thickness of anodic titania film formed in 1.5 M H2SO4was 2.5 Am, 2.8 Am for H2SO4/H2O2 mixture, 3.2 Am for
H2SO4/H3PO4, and 3.6 Am for H2SO4/H3PO4/H2O2mixture. These results indicate that due to the addition of
hydrogen peroxide, the film thickness increases slightly by
about 12%, but for addition of phosphoric acid, the
thickness increased significantly. In general, during anod-
ization for valve metal the oxidation takes place at metal/
oxide interface; on the other hand, oxide surface/electrolyteinterface dissolves in acid electrolyte. Therefore surface
morphology and layer thickness can be strongly associated
with electrolyte. In aluminum anodization for fabrication
of nanopore arrays in anodic alumina, Li et al. [1416]
showed that anodic alumina surface with larger cell
structure was observed by using phosphoric acid solution
rather than sulfuric acid as electrolyte. However, for an
addition of hydrogen peroxide, oxide layer can be more
grown without substantial change in morphology, due to
migration of oxygen containing ions from H2O2 in
electrolyte. The chemical reaction of the titanium surface
with peroxides has been proposed by Tengvall et al. [17].
From the results of Fig. 6 and thickness measurements we
therefore assume that differences in the morphology and
thickness of anodic films are concerned mostly with the
addition of phosphoric acid, and for the addition of
hydrogen peroxide the anodic film thickness was affected
slightly.
Fig. 6. SEM images showing surface oxide morphology formed at 180 V for 30 min in 1.5 M H2SO4 solution (a), 1.5 M H2SO4/0.3 M H2O2 mixture (b), 1.5 M
H2SO4/0.3 M H3PO4 mixture (c), and 1.5 M H2SO4/0.3 M H3PO4/0.3 M H2O2 mixture solution (d).
Fig. 7. XRD patterns of anodic TiO2 film thickness formed at 180 V for 30
min in 1.5 M H2SO4 solution (a), 1.5 M H2SO4/0.3 M H2O2 mixture (b),
1.5 M H2SO4/0.3 M H3PO4 mixture (c), and 1.5 M H2SO4/0.3 M H3PO4/
0.3 M H2O2 mixture solution (d).
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Fig. 7 shows the X-ray diffraction patterns of the anodic
titania film formed at 180 V for 30 min in various solutions.
The phase of the titania films was basically anatase, and the
rutile was also observed together with titanium peaks from
the substrate. And it is exhibited that crystalline phase of the
anodic oxide was dependent on the electrolytic compositions,
especially for the film in Fig. 7d, indicating that anatase
structure was predominant. The biological evaluation of these
anodic TiO2 films formed in 1.5 M H2SO4/0.3 M H3PO4/0.3
M H2O2 mixture solution was performed in a simulated body
fluid. After the immersion in a SBF solution at 37 8C in 5
days, the surface of anodic film was observed by SEM with
energy dispersive spectroscopy analysis (EDS).
For the comparison of biocompatibility, etched titanium
specimen prepared in HNO3/HF mixture was performed in
SBF. Fig. 8 shows the morphologies of etched titanium
and anodic TiO2 surface after immersion in SBF for 5
days. These results suggest that the particles were
precipitated on the surface of anodic film in SBF, but
no apparent changes appeared on the surface of the etched
titanium, as can be seen in Fig. 8b and d, respectively.
From the result of EDS analysis, as shown in Fig. 9, the
precipitated particles on the surface of anodic film is
revealed as Ca-rich compounds, which will be steadily
converted to hydroxyapatite crystalline phase that is
similar in composition and structure to bone apatite. The
anodic TiO2 film formed by electrochemical method has a
porous and relatively rough morphology, and composes of
anatase and rutile structure. From the results in Figs. 8
and 9, it is clearly suggested that these microporous
Fig. 8. SEM photographs of specimens soaked in SBF for 5 days. Morphologies of pure titanium surface etched in HF/HNO 3 (a) and (b), anodized in 1.5 M
H2SO4/0.3 M H3PO4/0.3 M H2O2 mixture solution (c) and (d). Original magnification, 1000 (a), 10,000 (b), 1000 (c), 10,000 (d).
Fig. 9. SEM micrograph and line profiles for precipitation particles on surface of anodic layer soaked in SBF for 5 days. The precipitated particles indicates Ca-
rich compound by EDS analysis.
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surface features and titanium oxide structure are all
effective for biocompatibility.
4. Conclusions
The anodic titanium oxide film for biomedical appli-cations was synthesized by anodic oxidation in acid
solution, and the surface characteristics of anodic TiO2layer has been evaluated. The major structure of anodic
TiO2 film was revealed to anatase, and surface morphol-
ogy exhibited a porous cell structure. For the effects of
electrolytes on the microstructure of anodic TiO2 film, the
differences in the morphology and thickness of anodic
films concerned mostly with the addition of phosphoric
acid. And for the addition of hydrogen peroxide the
anodic film thickness was affected slightly. The compo-
nent elements of the electrolyte, P and S, were found in
the oxide layer, which were incorporated from theelectrolyte into the oxide. From the result of biological
evaluation in simulated body fluid, the TiO2 anodic film
was effective for bioactive property.
Acknowledgments
This work has been supported by the Kookmin University.
References
[1] A. Wennerberg, T. Albrektsson, B. Andersson, Int. J. Oral Maxillofac.
Implants 11 (1996) 38.
[2] P.R. Klokkevold, R.D. Nishimura, M. Adachi, A. Caputo, Clin. Oral
Implants Res. 8 (1997) 442.
[3] D. Buser, T. Nydegger, T. Oxland, D.L. Cochran, R.K. Schenk, H.P.
Hirt, D. Snetivy, L.-P. Nolte, J. Biomed. Mater. Res. 45 (1999) 75.
[4] W. Weng, S. Zhang, K. Cheng, H. Qu, P. Du, G. Shen, J. Yuan, G.
Han, Surf. Coat. Technol. 167 (2003) 292.
[5] W. Weng, J.L. Baptista, Biomaterials 19 (1998) 125.
[6] Q. Chen, F. Miyaji, T. Kokubo, T. Nakamura, Biomaterials 20 (1999)
1127.
[7] P. Ducheyne, Q. Qiu, Biomaterials 20 (1999) 2287.
[8] A. Nakahira, K. Eguchi, J. Ceram Process. Res. 2 (2001) 108.
[9] E. Kontonasaki, T. Zorba, L. Papadopoulou, E. Pavlidou, X.
Chatzistavrou, K. Paraskevopoulos, P. Koidis, Cryst. Res. Technol.
37 (2002) 1165.
[10] L.L. Hench, J. Am. Ceram. Soc. 74 (1991) 1487.
[11] D.C. Clupper, L.L. Hench, J. Mater. Sci., Mater. Med. 12 (2001) 917.
[12] K. Hata, T. Kokubo, T. Nakamura, T. Yamamuro, J. Am. Ceram. Soc.
78 (1995) 1049.
[13] M.A. Fox, M.T. Dulay, Chem. Rev. 93 (1993) 54.
[14] A.P. Li, F. Mueller, A. Birner, K. Nielsch, U. Goesele, J. Appl. Phys.
84 (1998) 6023.
[15] A.P. Li, F. Mueller, U. Goesele, Electrochem. Solid-State Lett. 3
(2000) 131.
[16] O. Jessensky, F. Mueller, U. Goesele, Appl. Phys. Lett. 72 (1998)
1173.
[17] P. Tengvall, I. Lundstrom, L. Sjoqvist, H. Elwing, LM. Bjursten,
Biomaterials 10 (1989) 166.
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