Electrochemical and Mechanical Characterization of TiO 2 Nanotubes Obtained by Anodic Oxidation at High Voltage
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Electrochemical and Mechanical Characterization of TiO2 Nanotubes Obtained by Anodic Oxidation at High Voltage S. Mejía Sintillo1, C. Cuevas Arteaga1, R. Ma. Melgoza1 and P. Mijailova Nacheva2 1
Centro de Investigación en Ingeniería y Ciencias Aplicadas, Facultad de Ciencias Químicas e Ingeniería, Universidad Autónoma del Estado de Morelos. Av. Universidad 1001. 2 Instituto Mexicano de Tecnología del Agua-Postgrado en Ingeniería Ambiental UNAM-Campus IMTA. Blvd. Paseo Cuauhnáhuac 8532, Col. Progreso, C.P. 62550 Jiutepec, Mor., México. ABSTRACT The array of the TiO2 nanotubular films, also called one-dimensional nanostructures is carried out by electrochemical anodization tests, for which, titanium sheets were used with a high purity (99.7% and 0.25 mm thickness) in a solution of deionized water and glycerol (50:50 vol.%) + 0.27M NH4F applying a voltage of 20V. Electrochemical tests were performed at an anodization time of 2:30 hours and 3:30 hours. For the tests mirror polished foils and unpolished foils with flat surfaces to achieve better uniform arrays during the anodic growth of nanotubes were used. After anodizing, samples were observed in the scanning electron microscope (SEM) to determine the geometry and morphology of the films. Also, potentiodynamic polarization curves were performed for samples crystallized at 600 °C and 450 °C (polished and unpolished) to determine the electrochemical stability of the films, which were presented at two aqueous solutions: 1M of Na2SO4 (pH= 6.7) and 1M Na2SO4 + H2SO4 (pH= 3.2). Mechanical characterization was also performed by nanoindentation technique through the application of loading/unloaings of: (1, 2.5, 5, 10 mN). Chemical characterization was performed using XRD analysis, with the aim to determine the crystalline phases formed in the films crystallized at 450 °C and 600 °C. The electrochemical characterization showed that the TiO2 nanotubular film obtained by mirror polished and crystallized at 600 °C showed better electrochemical stability. Nanoindentation tests showed deformation curves, and the parameters such as hardness, Vickers hardness, elastic modulus and the maximum penetration depth were determined as mechanical parameters. INTRODUCTION Technological and scientific developments in many parts of the world have given guidelines for studying and creating new devices in different areas of science such as the nanotechnology [1]. Since nanostructured arrangements were discovered through electrochemical anodization, several layers of metal oxides formed on the surface have been of great interest for scientific study. The nanoscale metal oxides such as Al2O3, SiO2 and TiO2 have similar properties, being biocompatible materials for human beings. TiO2 and the porous silicon function as n-type semiconductors, because these oxides have free electrons in excess. It has been found that TiO2 nanotubular structure has application in semiconductor devices, photovoltaic cells and gas sensors, this is because the functional properties and morphology, which are formed on the
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