Characteristics Of The Hierarchical Porous Tio2 Layer Synthesized On Ti Via Plasma Electrolytic Oxidation: Role Of The Applied Voltage

A tailored porous ceramic layer of TiO2 was in-situ synthesized through Plasma Electrolytic Oxidation (PEO) process, using phosphate-based electrolyte at different applied voltages. The set-up was regulated to carry the process in low (430 V), medium (470 V), and high (510 V) voltages. The effects of applied voltage on the phase arrangement, microstructural, and morphological characteristics of the ceramic layer were then studied using Xray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The results showed that utilizing a relatively medium applied voltage of 470 V (Delta V of 130 V) can lead to a hierarchical TiO2 layer, which not only includes a mixture of both anatase and rutile TiO2 polymorphs but also presents a combined micro/nano-pores morphology. It was also found that while the lowest applied voltage leads to a relatively homogenous layer from morphological and roughness approaches, higher applied voltages may promote heterogeneities of the morphological characteristic. The formation mechanisms and morphological outcomes were finally discussed and graphically illustrated.