Apatite formed on the surface of plasma-sprayed wollastonite coating immersed in simulated body fluid

doi:10.1016/S0142-9612(00)00386-0

Biomaterials

Volume 22, Issue 14, 2001, Pages 2007-2012

https://doi.org/10.1016/S0142-9612(00)00386-0 Get rights and content

Abstract

Wollastonite coatings on titanium alloys substrates were prepared by plasma spraying and incubated in simulated body fluids for different periods to investigate the nucleation and growth of apatite on their surface. Surface structural changes of the specimens were analyzed by XRD and IR technologies. SEM and EDS were used to observe surface morphologies and determine the composition of wollastonite coatings before and after immersion in simulated body fluid. The changes in the concentrations of calcium, silicon and phosphorus in the simulated body fluids due to the immersion of the specimens were measured by inductively coupled plasma atomic emission spectroscopy. The results obtained showed that hydroxycarbonate apatite can be formed on the surface of the coating soaked in SBF for 1 day. With longer immersion periods, the coating surface was covered by hydroxycarbonate apatite, which indicated that the wollastonite coating possesses good bioactivity.

Introduction

Wollastonite (CaSiO₃), a common mineral of metamorphosed limestones and similar assemblages [1], is a raw material mainly used for traditional ceramics [2]. In addition, CaSiO₃ ceramics is a candidate material for high-frequency insulator [3]. One of the other possible applications for CaSiO₃ ceramics is as a medical material for artificial bone and dental root because some glasses, glass–ceramic and ceramics which include CaO–SiO₂ components were reported to showed good biocompatibility [4], [5], [6]. Hench [7] and his colleagues discovered that bone could bond chemically to certain glass composition. Ono et al. [8] reported A–W glass–ceramic had higher bioactivity than sintered hydroxyapatite (HA). Some reports [9], [10] pointed out that the rate of HAp formation on the surface of CaSiO₃ ceramics is faster than those of the other biocompatible glass and glass–ceramics in SBF solution.

Plasma spraying is most popular deposition technique due to its process feasibility as well as reasonably high coating bond strength and mechanical property [11]. Several bioactive materials, such as hydroxyapatite (HA) [12], [13] and bioglass (BG) [14], have been coated onto metals and alloys substrates by plasma spraying. Therefore, an interest has been taken in wollastonite (CaSiO₃) as a plasma-sprayed coating for applications in which bioactivity and biocompatibility are desired.

The object of this work was to deposite wollastonite coatings on Ti–6Al–4 V substrate by atmospheric plasma spraying (APS) and investigate microstructure and phase composition of coatings. The bioactivity of the coatings also was evaluated by examining hydroxycarbonate apatite formation on their surface in simulated body fluid (SBF).

Section snippets

Experimental methods

Commercially available wollastonite (CaSiO₃) powder, with a typical size range of 10–60 μm was used. Plasma spraying of the powder was made onto Ti–6Al–4 V substrates with dimensions 20 mm×10 mm×4 mm. An atmosphere plasma spray (APS) system (Sulzer Metco, Switzerland) was applied to fabricate wollastonite coatings under the modified spray parameters. Argon (40 slpm) and hydrogen (12 slpm) were used as primary and auxiliary arc gas, respectively. The feeding rate of powders was about 20 g/min using

Results and discussion

Fig. 1 showed SEM photographs of the surface and cross-sectional microstructure of the as-sprayed wollastonite coatings. From Fig. 1, it can be seen that the coating is characterized by a rough surface, with some partially melted particles (Fig. 1a). Under higher magnification, the structure of the coating appears to be highly melted and a few micro-cracks on the surface of the coating (Fig. 1b). The cross-sectional view of the coating revealed a lamellar structure with some pores and

Conclusions

Wollastonite coatings on titanium alloys substrates were prepared by plasma spraying. The coatings are characterized by a lamellar structure without obvious cracks between coatings and substrate. The crystalline wollastonite which may be preferred orientation and the amorphous phase can be found in the coatings. The hydroxycarbonate apatite (HCA) was formed on the surface of the coatings soaked in SBF for 1 day. With longer immersion periods, the surface of coatings was covered by dense

Acknowledgements

This work is supported by National Basic Research Fund under Grant G1999064706 and Shanghai Science and Technology R & D Fund under Grant 995211020.

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Apatite formed on the surface of plasma-sprayed wollastonite coating immersed in simulated body fluid

Abstract

Introduction

Section snippets

Experimental methods

Results and discussion

Conclusions

Acknowledgements

J Non-Cryst Solids

Biomaterials

Biomaterials

J Non-Cryst Solids

J Non-Cryst Solids

Effect of wollastonite substitute in a semivitreous dinnerware body

J Am Ceram Soc

Fatigue and life time of bioactive glass–ceramic A–W containing Apatite and Wollastonite

J Mater Sci

Apatite coating on ceramics, metals and polymers utilizing a biological process

J Mater Sci Mater Med