Adriano F. Feil

Self-Organized TiO2 Nanotube Arrays: Synthesis by Anodization in an Ionic Liquid and Assessment of Photocatalytic Properties

Self-organized TiO(2) nanotube (NT) arrays were produced by anodization in ethylene glycol (EG) electrolytes containing 1-n-butyl-3-methyl-imidazolium tetrafluoroborate (BMI.BF(4)) ionic liquid and water. The morphology of the as-formed NTs was considerably affected by changing the anodization time, voltage, and water and ionic liquid electrolyte concentrations. In general, a nanoporous layer was formed on the top surface of the TiO(2) NTs, except for anodization at 100 V with 1 vol % of BMI.BF(4), where the NTs mouth was revealed. The length and bottom diameter of the NTs as well as the pore diameter of the top layer showed a linear relationship with increased anodization voltage. These TiO(2) NTs were tested as photocatalysts for methyl orange photodegradation and hydrogen evolution from water/methanol solutions by UV light irradiation. The results show that the TiO(2) NTs obtained by anodization in EG/H(2)O/BMI.BF(4) electrolytes are active and efficient for both applications.

Growth of TiO2 nanotube arrays with simultaneous Au nanoparticles impregnation: photocatalysts for hydrogen production

Um novo metodo para a fabricacao de nanotubos (NTs) de TiO 2 organizados e impregnados com nanoparticulas (NPs) de ouro foi desenvolvido, e as propriedades estruturais, morfologicas e opticas dos NTs obtidos foram investigadas. Os arranjos de NTs de TiO 2 foram crescidos pela oxidacao anodica de Ti metalico utilizando solucoes eletroliticas contendo ions fluoreto e NPs de Au. As estruturas resultantes foram caracterizadas por espectrometria de retroespalhamento Rutherford (RBS), difratometria de raios X com incidencia rasante (GIXRD), microscopias eletronicas de transmissao (TEM) e de varredura (SEM) e espectroscopia UV-Vis. Tanto os arranjos de NTs sem Au quanto os impregnados com Au mostraram atividade fotocatalitica boa e estavel na geracao de hidrogenio a partir de misturas agua/metanol. Os nanotubos de TiO 2 contendo Au foram mais ativos na fotogeracao de hidrogenio do que os NTs de TiO 2 sem Au. A novel method for the fabrication of TiO 2 nanotubes (NTs) impregnated with gold nanoparticles (NPs) is reported. TiO 2 NT arrays were grown by anodic oxidation of Ti metal using fluoride electrolytes containing Au NPs. Resulting structures were characterized by Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffractometry (GIXRD), transmission and scanning electron microscopy (SEM and TEM) and UV-Vis spectroscopy. Au-free and Au-impregnated TiO 2 NT arrays showed good and stable photocatalytic activity for hydrogen generation from water/methanol solutions. Au-containing TiO 2 NTs presented higher hydrogen photogeneration activity than Au-free TiO 2 NTs.

The influence of aluminum grain size on alumina nanoporous structure

An approach to control the interpore distances and nanopore diameters of 150-nm-thick thin aluminum films is reported here. The Al thin films were grown by sputtering on p-type silicon substrate and anodized with a conventional anodization process in a phosphoric acid solution. It was found that interpore distance and pore diameter are related to the aluminum grain size and can be controlled by annealing. The grain contours limit the sizes of alumina cells. This mechanism is valid for grain sizes supporting only one alumina cell and consequently only one pore.

Micro and Nano-Texturization of Intermetallic Oxide Alloys by a Single Anodization Step: Preparation of Artificial Self-Cleaning Surfaces

Micro- and nanostructures of Ti-γCu (γ = 0, 30, 50, 70, and 100 wt %) intermetallic alloys were produced through a single anodization step. It was found that the original alloy composition influences the final oxide morphology obtained after anodization which presented formation of a microstructure with nanotubes, nanoparticles or nanopillars on the surface. Pure Ti and Cu oxide metals and their alloys presented hydrophilic or superhydrophilic properties immediately after anodization. When the anodized pure metal and/or Ti-γCu surfaces were functionalized with trimethoxypropylsilane (TPMSi), by dipping and coating with a thin perfluorinated layer, the treated substrates became in all cases superhydrophobic (water contact angles in the range of 152-166°), showing excellent self-cleaning properties with hysteresis below 3°. These results can be explained by a combination of nanomicro morphologies with low surface energy compounds in the topmost monolayers. The decrease in hysteresis was associated with a higher M-OH bond concentration on the anodized surfaces, which allowed for more complete TMPSi coating coverage. This study also indicates that easy and effective fabrication of superhydrophobic surfaces in pure metals and alloys is possible without involving traditional multistep processes.

Templated Growth of Pd Nanoparticles Using Sputtering Deposition Process and Its Catalytic Activities

A simple method based on sputtering deposition of Pd onto mesoporous SiO2 (SBA-15) was employed to produce supported Pd nanoparticles (NPs) that can be used as hydrogenation catalysts. The use of sputtering deposition eliminates contaminants and avoids additional drawbacks of traditional chemical methods applied to prepare heterogeneous supported metal catalysts. A mechanical resonant stirrer was used to revolve the SBA-15 powder and ensure homogeneous distribution of the Pd NPs over the support. The SBA-15 pores act as templates for Pd NPs and drive nanostructure growth. Consequently, the NPs obtained have the same diameter as that of the SBA-15 channels (~5 nm) and elongated particles are formed as sputtering deposition increases. The SBA-15 supported Pd NPs (Pd NPs/SBA-15) were tested in a probe hydrogenation of cyclohexene reaction to evaluate the catalytic activity of the Pd NPs. Turnover frequency (TOF) of 2000 min-1 were achieved with the lower Pd NPs concentration (0.15 wt%) catalyst.

ESTUDO DA RELAÇÃO ENTRE A PROFUNDIDADE DE PENETRAÇÃO E A ESPESSURA TOTAL DE REVESTIMENTOS EM TESTES INSTRUMENTADOS DE DUREZA

Ligas de Cu – Zn (latao) sao largamente aplicadas na industria metalurgica, pois apresentam propriedades como: alta resistencia e ductilidade para trabalhos a frio. Uma das principais aplicacoes para filmes finos de Cu – Zn e a fabricacao de pos de alta qualidade para a producao de micro espelhos. Assim, e importante avaliar de forma apropriada as propriedades de filmes de latao, bem como sua relacao com seus parâmetros de deposicao. A avaliacao das propriedades mecânicas de filmes e atualmente realizada atraves de testes instrumentados de dureza. Entretanto muitos pesquisadores afirmam que as penetracoes nao devem exceder o valor de 10 % da espessura total do filme, pois o substrato pode influenciar de forma significativa na medida. O objetivo deste trabalho e avaliar a influencia do substrato na medida de dureza, usando testes instrumentados de dureza. Amostras de filmes da liga Cu – Zn com diferentes espessuras t foram depositados sobre vidro e Si (111) pela tecnica de magnetron sputtering. O valor t para cada revestimento foi medido utilizando um microscopio eletronico da varredura (MEV). As propriedades mecânicas foram avaliadas atraves de testes instrumentados de dureza realizando penetracoes de diferentes profundidades (h%) em relacao a espessura do filme (t). Como resultado final e apresentado a relacao entre os valores de dureza medidos e a profundidade indentada de acordo com valor de espessura total do filme.

INFLUÊNCIA DOS PARÂMETROS DE DEPOSIÇÃO NA PROTEÇÃO CONTRA CORROSÃO DE TiN DEPOSITADOS POR BIASED MAGNETRON SPUTTERING

Filmes finos de nitreto de titânio (TiN) foram depositados sobre substratos de silicio (111) e aco ABNT 1020 atraves da tecnica de magnetron sputtering reativo variando a razao Ar/N 2 de 11 ate 13. Polarizacao de substratos (Bias Voltage) foi utilizada a fim de analisar a dinâmica do processo de formacao dos filmes e o comportamento dos mesmos frente a ataques corrosivos. A estrutura cristalina das amostras de TiN foi analisada por XRD e a estequiometria por NRA. Os testes de resistencia a corrosao foram realizados pela tecnica de Voltametria Ciclica, mantendo constante a velocidade de varredura em 10 mV.s -1 em uma solucao tampao com pH 5,6. Os resultados sao discutidos em funcao dos parâmetros de deposicao dos filmes finos, mostrando uma forte dependencia da dinâmica dos ataques corrosivos com o tipo de polarizacao aplicada.