The evolution of TiO 2 nanotubular morphology, synthesized in a mixture of fluorinated ethylene glycol and glycerol electrolyte, was studied as a function of the anodization time. The samples were characterized by FEG-SEM, XRD, XPS, UV-Vis and EIS. The formation of single-or double-walled TiO 2 nanotube structure can be efficiently controlled by the anodization time. For anodization times less than 30 minutes, a compact oxide layer is formed, followed by double-walled nanotube formation up to 120 minutes and single-walled nanotubes up to 240 minutes. XPS analyses show that the samples obtained with short anodization time have a high carbon content and oxygenated surface species compared to the longer-time anodized sample; however, binding energy peaks for Ti 2p remained invariant. The performances of TiO 2 nanotubular photoelectrodes were evaluated in photoelectrochemical water splitting where TiO 2 nanotubes anodized for 120 minutes presented the best performance that was related to their optimal morphology and charge transportation.

Anodizing of ferritic stainless steel has been used for decoration purposes to obtain a barrier effect. The most commonly used electrolyte for this process is INCO (5M H₂SO₄ + 2,5M CrO₃). INCO electrolyte with glycerin addition induces the formation of ordered porous structures, because glycerin reduces the electrolyte conductivity. Ferritic stainless steel was anodized in electrolyte composed by 2M H₂SO₄ with glycerin addition in different concentrations, without chromium oxide addition. It was observed that the addition of 90 v/v% glycerin promoted a reduction in the electrolyte conductivity, which caused an increase in the anodizing potential. The glycerin addition to the electrolyte diminished the oxide dissolution in the electrolytic solution, promoting the formation of an oxide with an ordered porous structure.

Ferritic stainless steels exhibit properties, such as good electrical conductivity, good corrosion resistance and low cost, that are beneficial for their application as interconnects in intermediate temperature solid oxide fuel cells (ITSOFC) that function at temperatures between 600°C and 800°C. However, the stainless steel corrosion resistance is attributed to the amount of Cr, which is an element that forms a chromium oxide (Cr2O3) layer, acts as an oxidation protective barrier at high temperatures, and reduces the interconnector performance due to its low electrical conductivity. In this context, the objective of this work was to obtain spinel coatings from the Fe and Ni metallic alloy thermal conversion on AISI stainless steel 430 substrate produced by electrodeposition. The morphology and microstructure of the spinel films deposited on stainless steel were characterized by SEM, EDS, XRD and adherence analysis. The results obtained showed that the films were adherent, dense and continuous along the AISI stainless steel 430 substrate surface. In addition, the heat treatment procedure effectively produced crystalline spinels ((NiFe)3O4).

No abstract

Estudos vêm sendo desenvolvidos para melhorar a resistência à oxidação em temperaturas elevadas do aço inoxidável ferrítico, os quais têm sido propostos para fabricação de interconectores de células a combustível do tipo óxido sólido de temperatura intermediária (IT-SOFC). Dentre os revestimentos empregados, os revestimentos cerâmicos de óxidos do tipo espinélio têm sido os mais aplicados. Nesse contexto, no presente trabalho foram obtidos revestimentos à base de Mn e Co sobre aço inoxidável ferrítico (AISI 430), utilizando a técnica de dip-coating. Os filmes obtidos foram caracterizados quanto à morfologia por MEV e quanto à composição elementar por EDS. Foi possível obter do revestimento à base de Mn e Co continuo e aderente sobre o substrato metálico.