Effect of phosphorus-ion implantation on the corrosion resistance and biocompatibility of titanium
Introduction
Titanium is a well-known implant material widely and successfully used in medicine. The primary reason for using titanium in medical applications is its biocompatibility. Examinations of titanium in the solutions simulating physiological fluids have shown that, in this environment, calcium phosphate forms spontaneously on its surface [1], [2]. This probably contributes to the good biocompatibility of titanium. The spontaneously formed calcium phosphate layer is very thin: after 30 days of exposure its thickness is of the order of a few nanometers. Hanawa et al. [3], [4], [5], [6], [7] have shown that the process of formation of the phosphates can be accelerated if the titanium surface is first modified by calcium-ion implantation.
The present authors have found that, at potentials higher than 2.5 V, calcium implanted titanium is subject to pitting corrosion [8]. This was the reason why we thought of implanting phosphorus, which is a constituent of phosphates.
There are only few publications concerned with the phosphorus-ion implantation into the surface of titanium. The available papers discuss how phosphorus-ion implantation affects the structure and chemical composition of the surface layer formed during the implantation [9], [10], [11]. Ferdjani et al. [9] examined the distribution of the phosphorus concentration within a surface layer implanted with a dose of 5×1016 P+/cm2 at a beam energy of 130 keV. The phosphorus atoms appeared to occupy the interstitial sites in this layer. The effect of phosphorus-ion implantation into the surface of titanium upon the chemical composition of the implanted layer was discussed by Baunack et al. [10]. They examined samples implanted with doses of 1×1015–3×1017 P+/cm2 at an energy of 20 keV. They found that, at doses below 1016, phosphorus did not enter in chemical bonds with titanium, whereas at doses equal to, and above 1017 P+/cm2, a new TiP phase appeared. The amount of this TiP phase increased with increasing phosphorus dose.
The effects of the phosphorus-ion beam energy and phosphorus dose on the chemical composition and structure of the implanted surface layers were examined by Wieser et al. [11]. The implantation parameters they used were: 3×1017 P+/cm2 at an ion beam energy of 30 keV, and 5×1017 P+/cm2 with a beam energy of 195 keV. The thickness of the implanted layer was 60 nm at an energy of 30 keV, and 250 nm at an energy of 195 keV. XRD examinations identified no titanium/phosphorus chemical compounds, but indicated that the surface layer became partially amorphous.
No data are available in the literature describing how the phosphorus-ion implantation affects the corrosion resistance of titanium and the precipitation of calcium phosphate on the titanium surface. The aim of the present study was to examine whether the corrosion resistance of titanium can be improved by phosphorous ion implantation.
Section snippets
Materials and methods
The material examined was pure commercial titanium (grade 2). The test specimens in the form of discs 6.2 and 14 mm in diameter and 2 mm thick were polished one side to the mirror finish and then their surfaces were implanted with phosphorus ions at a dose of 1×1017 P+/cm2. The ion energy was 25 keV. The conditions under which the implantation was carried out were so selected that the phosphorus concentration was maximum on the surface. During the implantation, the temperature of the samples did
TEM results
The starting material contained dislocations and a high density of subgrains with blurred-boundaries that occurred within the original grains whose size exceeded 1 μm. This is a characteristic microstructure of the non-recrystallized structure of a metal subjected to plastic deformation (Fig. 1). Fig. 2 shows the diffraction image of a surface layer formed as a result of phosphorus implantation. The blurred rings indicate that the surface layer has become amorphous. By measuring the diameter of
Discussion
The phosphorus-ion implantation has appeared to improve the corrosion resistance of titanium. An increased corrosion resistance of phosphorus implanted titanium placed in SBF was observed after both short-term and long-term exposures. This increase can be attributed to the alterations of the structure and of the chemical composition of the surface layer due to the implantation.
TEM examinations of the microstructure show that, after the implantation, the surface layer becomes amorphous, whereas
Conclusion
Based on the results obtained we can conclude that:
Phosphorous ion implantation with a dose of 1×1017 P+/cm2 results in an amorphisation of the surface layer and the formation of TiP.
Phosphorous ion implantation with a dose of 1×1017 P+/cm2 increases the corrosion resistance after short-term as well as long-term exposures.
The phosphate layers formed on the titanium surface during the exposure do not affect the corrosion resistance.
The biocompatibility of phosphorus-ion implanted titanium was
Acknowledgments
The authors acknowledge the support of the State Committee for Scientific Research though the Grant No. 7T08C 024 13.
References (31)
- et al.
Auger electron spectroscopic studies of the interface between hiuman tissue and implants of titanium and stainless steel
J Colloid Interface Sci
(1986) - et al.
Calcium phosphate naturally formed on titanium in electrolyte solution
Biomaterials
(1991) - et al.
Characterization of surface film formed on titanium in electrolyte using XPS
App Surf Sci
(1992) - et al.
X-ray photoelectron spectroscopy of calcium-ion-implanted titanium
J Electron Spectrosc Relat Phenom
(1993) - et al.
Effect of calcium-ion implantation on the corrosion resistance and biocompatibility of titanium
Biomaterials
(2001) - et al.
Phosphorus implantation in titaniumapplication to calibration analysis
J Alloys Compounds
(1991) - et al.
Modification of titanium by ion implantation of calcium and/or phosphorus
Surf Coat Technol
(1999) - et al.
Electrochemical impedance spectroscopy study of the passive oxide film on titanium for implant application
Electrochim Acta
(1996) Ion-implantation and irradiation studies using amorphous metals
Nucl Instrum Methods
(1981)Amorphization Of metallic systems by ion beams
Mater Sci Eng
(1985)
Microstructural and corrosive interactions in phosphorus ion implanted 304L stainless steel—II. Alterations in corrosion resistance by implantation
Corros Sci
Some experimental studies on metal implantation
Nucl Instrum Methods
Hydration and preferential molecular adsorption on titanium in vitro
Biomaterials
Characterization of calcium phosphates precipitated from simulated body fluid of different buffering capacities
Biomaterials
Cited by (70)
A comprehensive review on surface post-treatments for freeform surfaces of bio-implants
2023, Journal of Materials Research and TechnologyElectroless deposition of NiMoP coating on Q235B steel and its corrosion resistance in simulated concrete pore solution
2023, International Journal of Electrochemical ScienceOsteogenic trace element doped ceramic coating for bioimplant applications
2023, Advanced Ceramic Coatings for Biomedical ApplicationsObtaining and characterization of PEO layers prepared on CP-Ti in sodium dihydrogen phosphate dihydrate acidic electrolyte solution
2019, Surface and Coatings TechnologyCitation Excerpt :The assessment of the surface chemistry was done based on the XPS transitions of interest, confirming the existence of Ti oxidation states. Thus, Ti2p core-level spectra were fitted with three components located at 455.5 eV, 457.2 eV and 458.7 eV corresponding to Ti2+, Ti3+ and Ti4+ species, respectively, being in excellent agreement with literature data [24,25]. The deconvolution of P2p photoemission spectra showed the presence of phosphates and phosphites and consisted of four contributions at 128.1 eV, 129.6 eV, 131.7 eV and 133.2 eV, which were ascribed to metal phosphides [24,25], elemental phosphorus [24], PC bonds [26] and phosphate [25] respectively, well consistent with previous reports.
Tribology of materials for biomedical applications
2019, Mechanical Behaviour of BiomaterialsEffect of deposition temperature on the mechanical, corrosive and tribological properties of mullite coatings
2018, Ceramics InternationalCitation Excerpt :However, low hardness (≤ 300 Hv), high coefficient of friction and poor wear-resistance severely limit the application of titanium alloys. To overcome the limitation, tremendous efforts were expended in surface modification of titanium alloys via an appropriate surface engineering technology, including thermal oxidation [4], physical vapor deposition [5], ion implantation [6], diffusive gas [7], and plasma spraying [8]. Among them, plasma spraying is well known for its high-deposition rate and economy [3].