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Master's Dissertation
DOI
10.11606/D.85.2018.tde-15062018-105555
Document
Author
Full name
Edvan Almeida de Souza Filho
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2017
Supervisor
Committee
Pillis, Marina Fuser (President)
Antunes, Renato Altobelli
Araújo, Edval Gonçalves de
Title in Portuguese
Caracterização de filmes de TiO2, N:TiO2 e TiO2/N:TiO2 obtidos por deposição química de organometálicos em fase vapor
Keywords in Portuguese
dopagem
filmes
MOCVD
multicamada
TiO2
Abstract in Portuguese
Filmes finos de TiO2 e N:TiO2, e multicamadas TiO2/N:TiO2 foram crescidos sobre substratos de aço AISI 316 e Si(100), por meio da técnica de deposição química de organometálicos em fase vapor (MOCVD). Foram produzidos filmes com diferentes espessuras, nas temperaturas de 400 e 500°C. Os filmes foram caracterizados utilizando-se técnicas de difração de raios X (DRX), espectroscopia de fotoelétrons excitados por raios x (XPS) e microscopia eletrônica de varredura (MEV). A resistência à corrosão foi avaliada por meio de testes de polarização potenciodinâmica em eletrólito 3,5%p NaCl. Filmes não dopados, crescidos a 400°C, apresentaram TiO2 anatase, enquanto que os crescidos a 500°C apresentaram a fase rutilo, além de anatase. Nos filmes dopados com nitrogênio (7,29 e 8,29 at% a 400 e 500°C, respectivamente), em ambas as temperaturas, houve a formação de TiO2 anatase, bem como de fases contendo nitrogênio. Os filmes de TiO2 crescidos a 400°C ofereceram melhor proteção contra a corrosão que os crescidos a 500°C. Filmes crescidos a 500°C apresentaram estrutura colunar, que representa alto nível de porosidade, enquanto que os filmes crescidos a 400°C apresentaram estrutura mais densa. A dopagem não foi eficiente para proteger o substrato contra corrosão, provavelmente devido à formação das fases contendo nitrogênio. Os resultados para os testes com filmes compostos por multicamadas sugerem que aqueles com mais interfaces apresentam melhor resistência à corrosão. O processo de corrosão das amostras se inicia na superfície do filme, que está em contato com o meio agressivo, originando pites, que permitem ao meio corrosivo acessar o substrato metálico. O metal é atacado e dissolvido sob o filme, e resulta na delaminação do filme.
Title in English
Characterization of TiO2, N:TiO2 and TiO2/N:TiO2 films obtained by metallorganic chemical vapor deposition
Keywords in English
doping
films
MOCVD
multilayered
TiO2
Abstract in English
TiO2 and N-doped TiO2 (N:TiO2) thin films, and TiO2/N:TiO2 multilayered films were grown on AISI 316 steel substrates, and Si (100) by using metallorganic chemical vapor deposition (MOCVD) technique. The growth of the films was carried out at 400 and 500°C, and films with different thicknesses and structures were obtained. Titanium dioxide films were produced by using only titanium isopropoxide IV as both titanium and oxygen sources. In order to obtain N:TiO2 films, NH3 was also added to the system. The films were characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) The corrosion resistance was evaluated by potentiodynamic polarization tests in a 3.5wt% NaCl electrolyte. TiO2 undoped films, grown at 400°C, presented anatase, while those grown at 500°C showed the rutile phase, besides anatase. For nitrogendoped films (7.29 and 8.29 at% at 400 and 500°C, respectively), at both temperatures, TiO2 anatase was formed, as well as nitrogen-containing phases. TiO2 films grown at 400°C provided better protection against corrosion than those grown at 500°C. Films grown at 500°C showed a columnar structure, which represents a high level of porosity, while the films grown at 400°C presented a denser structure. Doping was not efficient to protect the substrate against corrosion, probably due to the formation of nitrogen containing phases. The corrosion results for tests with multilayered films suggest that those with more interfaces present better resistance to corrosion. The corrosion of the samples starts at the surface of the films, which is in contact with the aggressive medium, causing pitting in this film, which allows the corrosive medium to reach the metallic substrate. The metal is attacked and dissolved under the film, and results in film delamination.
 
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Publishing Date
2018-10-10
 
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