Characterisation of the nanotubular oxide layer formed on the ultrafine-grained titanium

Dragana Ranko Barjaktarević,Marko P Rakin,Veljko R Djokić

doi:10.30544/402

Abstract

Commercially pure titanium (cpTi) and titanium alloys are metallic implant materials usually used in dentistry and orthopaedics. In order to improve implant properties, Ti-based materials may be surface modified by different procedures. One of the most attractive methods is electrochemical anodization, as a method for obtaining nanotubular oxide layer on the material surface, aiming at improving mechanical, biological and corrosion properties of the metallic biomaterials. In the present study, ultrafine-grained titanium (UFG cpTi) was obtained by high pressure torsion (HPT) under a pressure of 4.1 GPa with a rotational speed of 0.2 rpm, up to 5 rotations at room temperature. In order to form homogeneous nanotubular oxide layer on the UFG cpTi, the electrochemical anodization was performed in phosphoric acid containing 0.5 wt. % of NaF electrolyte during anodizing times of 30, 60 and 90 minutes. The characterisation of thus formed nanotubes was performed using the scanning electron microscopy (SEM), while the surface topography was analysed using the atomic force microscopy (AFM). The results show that the electrochemical anodization process leads to an enhanced roughness of the surface. The mechanical behaviour of the UFG cpTi after the electrochemical anodization process is estimated using the nanoindentation technique. Obtained results show that anodized material has lower value of nanohardness than non-anodized material. Moreover, anodized UFG cpTi has lower modulus of elasticity than non-anodized UFG cpTi and the value is close to those observed in bones.

Highlights

Titanium based materials are one of the frequently used metallic biomaterials in dentistry and orthopaedics [1]
The obtained image clearly demonstrates that anodization of titanium in an electrolyte with fluoride ions could lead to the formation of the nanotubular oxide layer
It could be concluded that an anodizing time of 30 minutes was not enough to form nanotubes Fig. 4 (a), while an anodizing time of 90 minutes led to the decomposition of the already formed nanotubular oxide layer Fig. 4 (c)

Summary

Introduction

Titanium based materials are one of the frequently used metallic biomaterials in dentistry and orthopaedics [1]. These materials have become materials of choice due to their favourable characteristics, such as corrosion resistance, osseointegration and biocompatibility in the human body environment [2,3,4]. The disk is subjected to high pressure, while shear strain is induced in the disk by rotation of the anvils in opposite directions [9]. The equation (1) shows that the shear strain value during HPT process is zero in the centre and becomes maximum at the edge of the disk [7]

Methods

Results

Conclusion