2008 Volume 58 Issue 11 Pages 593-598
Electrodeposition of HAp on a porous electrode of sintered titanium spheres has been studied. It took place only at the outer surfaces, but not at the inside of the porous electrode if the maximum size of spheres was 150 μm or lower. It is caused by the intricate fine structure of the electrodes composed of micro-sized titanium particles, which prevents the uniform current flow at the entire titanium surface. However, by applying pretreatments on titanium spheres electrode, deposition of HAp was remarkably improved in the following order; anodic film formation at 10 V<anodic breakdown film at 110 V<alkali treatment in NaOH. This is explicable by the addition of uniform resistance to titanium sphere surfaces at both outside and inside of the electrode, which originates from roughly structured oxide layers. As a result, uniform current flow followed by uniform hydrogen gas evolution at the entire titanium surface was induced. Furthermore, when electrolysis was performed under ultrasonic wave in addition to the oxide layer formation, electrodeposition of HAp at the inside of the electrode was dramatically improved to fulfill the space among titanium spheres. The vibration of ultrasonic wave acted an important roll to activate the evolved hydrogen gas to enhance ion migration and convection of the electrolyte. Thus, high controllability of HAp deposition on porous titanium could be attained.
