Investigation of the growth mechanism of porous TiO2 films prepared by galvanostatic anodization

• Grant number: 08/00180-0
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: August 01, 2008
• End date: October 31, 2011
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Ernesto Chaves Pereira de Souza
• Grantee: Mariana de Souza Sikora
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 03/09933-8 - Center for Excellence in Electrochemically Synthesized Nanostructures, AP.PRNX.TEM

Abstract

In this work the experimental and theoretical aspects of the growth of titanium dioxide obtained by galvanostatic anodization were studied. The films were prepared by galvanostatic anodization of titanium, where the curve of voltage versus charge was investigated. In the initial growth there is an abrupt increase of the voltage, followed by a change in slope of the curve. In this region the voltage reaches a steady state characterized by oscillations around a mean value that are often associated with the phenomenon of film's breakdown, microdischarges (sparks) are also observed on the electrode surface. The experimental study began with the "system scanning" in which we used the factorial design in order to associate the experimental variables with the responses (electrochemical, morphologicaland microstructural). After this first study, we investigated the influence of applied charge on the system, keeping constant the other experimental conditions. In this investigation, we analyzed the influence of charge on the microstructure, morphology and also in the photoactivity of the films. The results revealed that the photoactivity in influenced by both the microstructure and morphology. However, the microstructure seems to be more important for films obtained after the breakdown region, where the morphology remains constant. One possible explanation for these results is that the region of grain boundary acts as a recombination center of e-/h+ pairs. In addition to these studies, the TiO2 doping was carried out with niobium. The physicochemical properties of thedoped films were compared with pure films and it was observed that doping promotes an increase in the rate of crystallization of the films even when small amounts of dopants are introduced into the oxide. An applied study was conducted in order to apply the titanium anodization as a water heater system. The results of this investigation have shown that the titanium anodization provides greater eciency and heating rate when it is compared with comercial resistances. Finally, based on experimental results, we developed a model for the growth of titanium oxide films prepared electrochemically. This semi-empirical model was developed from the "current burst model". The first stage consisted in the numerical simulation of the dissipation of the heat generated by a spark event in three ways (electrolyte, metal and oxide) using the finite elements method. The simulation result have shown that the thermal dissipation extends over an area of up to 400 nm and the spark is able to fuse locally all the solid phases. Thus, the description of the oscillating system was made through its three main elements: the local oscillation mechanism (breakdown), desynchronization mechanism dissolution) and lateral synchronization orinteraction (promoted by the flow of material). (AU)

Scientific publications

(6)

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

LIMA, A. S.; ROCHA, R. D. C.; PEREIRA, E. C.; SIKORA, M. DE S.. Photodegradation of Ciprofloxacin antibiotic over TiO2 grown by PEO: ecotoxicity response in Lactuca sativa L. and Lemna minor. INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY, MAR 2021. (13/07296-2, 17/11986-5, 14/50249-8, 08/00180-0)

FLORINDO, JOAO B.; SIKORA, MARIANA S.; PEREIRA, ERNESTO C.; BRUNO, ODEMIR M.. Multiscale Fractal Descriptors Applied to Nanoscale Images. Journal of Superconductivity and Novel Magnetism, v. 26, n. 7, p. 2479-2484, JUL 2013. (08/00180-0, 11/01523-1)

SIKORA, M. S.; CARSTENSEN, J.; FOELL, H.; PEREIRA, E. C.. Theoretical Calculation of the Local Heating Effect on the Crystallization of TiO2 Prepared by Sparking Anodization. CURRENT NANOSCIENCE, v. 11, n. 3, p. 263-270, 2015. (08/00180-0)

SIKORA, MARIANA DE SOUZA; ROSARIO, ADRIANE VIANA; PEREIRA, ERNESTO CHAVES; PAIVA-SANTOS, CARLOS O.. Influence of the morphology and microstructure on the photocatalytic properties of titanium oxide films obtained by sparking anodization in H3PO4. Electrochimica Acta, v. 56, n. 9, p. 3122-3127, MAR 30 2011. (08/00180-0)

FLORINDO, JOAO B.; SIKORA, MARIANA S.; PEREIRA, ERNESTO C.; BRUNO, ODEMIR M.. Characterization of nanostructured material images using fractal descriptors. PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS, v. 392, n. 7, p. 1694-1701, APR 1 2013. (08/00180-0, 11/01523-1)

LIMA, A. S.; ROCHA, R. D. C.; PEREIRA, E. C.; SIKORA, M. DE S.. Photodegradation of Ciprofloxacin antibiotic over TiO2 grown by PEO: ecotoxicity response in Lactuca sativa L. and Lemna minor. INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY, v. 19, n. 4, p. 10-pg., 2021-03-09. (17/11986-5, 14/50249-8, 13/07296-2, 08/00180-0)