Preparation of nanosized porous oxide layers on titanium by asymmetric AC electrolysis in sulfuric acid
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Research Letter
Preparation of nanosized porous oxide layers on titanium by asymmetric AC electrolysis in sulfuric acid Noriyuki Y. Iwata , and Shin-ichi Tanaka, Department of Materials Science and Engineering, National Institute of Technology, Kurume College, 1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan Yuriko Fukushima, Advanced Engineering School, National Institute of Technology, Kurume College, 1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan Gregory Jerkiewicz, Department of Chemistry, Queen’s University, 90 Bader Lane, Kingston, ON. K7L 3N6, Canada Address all correspondence to N.Y. Iwata at [email protected] (Received 31 May 2018; accepted 17 December 2018)
Abstract The formation of nanosized porous oxide layers on titanium (Ti) by asymmetric alternating current anodizing in sulfuric acid has been studied using electrochemical techniques. In order to prevent spark discharge at Ti electrode upon its anodization in 1.0 M H2SO4 solution, the magnitude of the cathodic current is reduced using a special electrical circuit consisting of a variable resistor and two diodes. The unique surface treatment approach gives rise to the formation of nanosized porous layer in a very short period of time and without spark discharge. The surface of porous layers thus obtained has in vitro apatite-forming ability.
Introduction Titanium (Ti) and its alloys have been widely used as biomedical materials and have found numerous applications as artificial bones and as various types of biocompatible implants due to their highly beneficial chemical, physical, mechanical, and physiological properties. Especially, their chemical resistance upon contact with fluids and tissue encountered in the human body make them suitable implant materials because they meet numerous selection criteria. Moreover, Ti being a light metal possesses required properties, such as good ductility, high tensile modulus, fatigue strength, as well as an elastic modulus comparable with that of the human bones. An appropriate surface treatment is required to enhance the bonebonding capacity of Ti implants.[1–14] For instance, apatite surface layers are often used in Ti implants to provide their bioinert surfaces with bioactive materials, such as apatite or metaphosphate-containing glass-ceramics. These layers (also referred to as coatings) are typically prepared using plasma spraying at very elevated temperatures,[4,5] although the process is known to alter the crystal structure of the metal or alloy, bringing about diminished biocorrosion resistance, cracking the surface layer, as well as introducing other structural defects. Alternative methods of preparing coatings and finetuning their interfacial properties are laser deposition,[6] solgel dipping,[7,8] electrophoresis,[9,10] or soaking in an alkaline solution,[11–14] etc. In the case of Ti-based materials, biocompatibility improvement can be achieved by applying many different surface treatment techniques. However, electrochemical surface treatment
methods offer some advantages, such as relative simplicit
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