Abstract The main problem in metal oxidation is the spalling and de-cohesion of the oxide layer, which results in delamination due to strong compressive stress gradient through the layer. Present paper proposes the use of a modified process named Asymmetric Bipolar Pulsed Plasma (ABiPPS) for plasma-oxidation treatment of low carbon steel AISI-1006 samples. Results show that the ABiPPS process ensures high plasma stability and enables the growth of uniform oxide layers (with thickness up to 6 µm) on metal surfaces. Plasma generated through bipolar asymmetric voltage pulses provides better control on surface bombardment through interspersed jets of ions and electrons, during the oxidation process. The control of intermittent ions and electrons bombardment (through voltage peaks up to 1.5 kV and period about 1µs), during plasma oxidation, make it possible to improve the adhesion between the oxide layer and the substrate, moreover the control of crystalline phases, such as hematite and magnetite.

Abstract This contribution reports on an experimental polishing procedure, that is comprised of early grinding in Al2O3 slurries and late polishing in colloidal silica, which is used for preparing the nitrided region of a plasma nitrided austenitic stainless steel, for crystallographic analysis via electron backscatter diffraction (EBSD). The suitability of the polished surfaces for conducting EBSD characterization was assessed through an analysis of both the surface roughness (appraised by atomic force microscopy) and the quality of the Kikuchi diffraction patterns. We observed that as-nitrided virgin surfaces were not suitable for EBSD characterization, due to intense surface roughening, which was induced by the nitriding process itself. At the subsurface region, exposed by on-top mechanical polishing, the flatter nature of the polished surfaces allowed the acquisition of EBSD patterns with enough quality for microtexture analysis. A resolution of 100 nm in the total removed layer was attainable via careful control of the polishing parameters. Close parallelism between the polished and original surfaces was verified.

Resumo Filmes de TiO2 dopados com Nb podem associar propriedades como TCO (transparent conductive oxide) e super-hidrofilicidade, quando ativados por luz UV. Filmes metálicos de Ti-Nb foram depositados sobre substrato de vidro via triodo magnétron sputtering e posteriormente os filmes foram oxidados em atmosfera ambiente a 600 °C durante 1,0 h em condições similares àquelas usadas no tratamento térmico de vidros. Medidas de rugosidade, cristalização, composição química e molhabilidade foram realizadas através das técnicas de microscopia de força atômica, difração de raios X, fluorescência de raios X e ângulo de contato, respectivamente. Os resultados mostraram que os filmes foram completamente oxidados, tornando-se visualmente transparentes à luz visível com cristalização da fase rutilo-TiO2. Após irradiação com luz UV, os filmes TiO2:Nb apresentaram rugosidade em escala nanométrica podendo ser classificados como super-hidrofílicos, com valores de ângulo de contato similares àqueles de filmes de TiO2 puros, preservando características de filmes autolimpantes.

Abstract Niobium doped TiO2 films can combine properties of TCO (transparent conductive oxide) with superhydrophilicity activated by UV radiation. Ti-Nb metal films were deposited on a glass substrate through triode magnetron sputtering. Afterward, the Ti-Nb metallic films were oxidized at 600 °C during 1.0 h in air atmosphere, with similar parameters of those used in glass heat-treatment. Measurements of roughness, crystallization, chemical composition, and wettability were carried out through atomic force microscopy, X-ray diffraction, X-ray fluorescence, and contact angle, respectively. Results showed that all films were crystallized as rutile-TiO2 phase and were transparent in visible range. TiO2:Nb films showed nanometer roughness that can be classified as superhydrophilic, after activation with UV light. The contact angle values were similar to those of pure TiO2 films, that is, the TiO2:Nb films preserved the self-cleaning properties.

UNS S31603 stainless steel (SS) substrates were covered by reactive magnetron-sputtering with protective SS coatings of the same steel specification. A mechanical characterization study (through nano-, micro- and macro-hardness tests) of samples obtained under two different sputtering conditions and varying the N2 gas flow rate was carried out. This contribution aimed at appraising the effects of varying the nitrogen flow rate on hardness, elastic modulus, and susceptibility to indentation-induced crack formation of the coated SSs. Nitrogen-free samples displayed body-centered cubic (BCC) films with 9.0-9.4 GPa hardness and 203-206 GPa elastic modulus, while their susceptibility to indentation-induced cracking varied between superior and moderated among the two sets of sputtering conditions studied. Samples alloyed with 4-6 N at-% displayed a predominantly face-centered cubic (FCC) structure, 9.4 GPa hardness, 196-218 GPa elastic modulus, and superior resistance to crack formation. Samples with 11.5-22.0 N at-% were fully composed of the FCC structure, displayed 12.4-15.2 GPa hardness, 188-193 GPa elastic modulus, and moderated resistance to indentation-induced crack formation. Samples with 47.0 N at-% displayed FCC compound nitride structure, for which hardness and elastic modulus were 8.1 GPa and 139 GPa, respectively. These samples displayed low resistance to crack formation.

Neste trabalho foi desenvolvido um sensor com propriedades inteligentes, baseado em polímeros escova (poli-ácido acrílico) modificado com nanopartículas de ouro. Este novo material demonstrou propriedades comutáveis que podem discriminar diferentes pHs. O eletrodo foi caracterizado por voltametria cíclica (CV), espectroscopia de impedância eletroquímica (EIS) e ressonância plasmônica de superfície localizada (LSPR).

In this work, a sensor was built up with smart material based on polymer brush and gold nanoparticles. The modified electrode functionalized with polyacrylic acid (PAA) tethered to indium tin oxide (ITO) and covered with gold nanoparticle (ITO/PAA/Au) demonstrated switchable interfacial properties discriminating different pHs. The switchable electrochemical and plasmonic process was characterized by cyclic voltammetry (CV), electrochemistry impedance spectroscopy (EIS), and localized surface plasmon resonance (LSPR).