Modular UV Curing Sol-Gel Coating for Invisible, Levelling and Easy to Clean Multi-Layer Systems.

Current methods for the hardening step of functional coatings over different materials imply the use of high temperatures, high energy consumption or long periods of time, which have repercussions on the speed and cost of the product. We report here a simple and low-cost methodology for the functionalization of low-cost stainless steel, which is modular, depending on the functionality pursued: a levelling layer for smoothing the surface of the material, an "easy to clean" property, or both of them. This research is based on sol-gel coatings cured under UV light without requiring high thermal hardening processes, making it applicable to plastics and other sensible materials and possessing high chemical and thermal stability. The film ensures lower processing costs and higher rates of hardening if adequate medium-pressure lamps are employed. This formulation is also well-defined for scaling up the process, so it is possible to perform a continuous coating in large areas by employing mild processing conditions (low temperature, atmospheric pressure). In addition, the sol-gel solution was fully characterized and studied in order to guarantee a long service life before deposition, with a focus on industrial applications in the domestic sector.

Mechanical Performance of AlCrSiN and AlTiSiN Coatings on Inconel and Steel Substrates after Thermal Treatments.

The objective of this study was to explore the mechanical properties of AlCrSiN and AlTiSiN coatings deposited on Inconel and steel substrates after thermal treatments of 500 °C and 800 °C. Nanoindentation was used to measure the hardness and elastic modulus of the coatings, and microindentation was used for observing the contact damage with Hertzian contact loadings. Microscratch and Mercedes tests were used to evaluate the adhesive strength between coating and substrate with both progressive and static loads, respectively. The surface damage was inspected by optical microscopy and scanning electron microscopy (SEM). Focus ion beams (FIB) were used to mill the cross-sections in order to detect the extent and mode of failure. The results show that AlCrSiN coatings and Inconel substrates exhibit better mechanical performance, even after thermal treatments.

Antibacterial Activity of Photocatalytic Metal Oxide Thin Films Deposited by Layer-by-Layer Self-Assembly.

This paper reports the use of the Layer-by-Layer self-assembly (LbL) as an efficient technique for the fabrication of thin-films with antibacterial activity. The LbL coatings are composed of a positive polyelectrolyte such as Poly(allylamine hydrochloride) (PAH) and an anionic polyelectrolyte such as Poly(sodium 4-styrene sulfonate) solution (PSS). In addition, these polyelectrolytes can be also used as an adequate encapsulating agent of specific metal oxide precursors such as titanium dioxide (TiO2) and iron oxide (Fe2O3) nanoparticles, making possible the fabrication of hybrid thin films composed of organic polymeric chains related to the polyelectrolytes and inorganic structure associated to the metal oxide nanoparticles. Four different LbL coatings have been fabricated and a comparative study about the resultant topographical, optical and wettability properties is presented by using light interferometry, atomic force microscopy (AFM), UV-Vis spectroscopy and water contact angle (WCA) measurements. In addition, X-ray fluorescence (XRF) has been also employed in order to corroborate the presence of metal oxide precursors inside the polymeric chains of the polyelectrolytes. Finally, the antibacterial tests have demonstrated that LbL coatings composed of metal oxide nanoparticles produce an enhancement in the efficacy and antibacterial activity.

Quasi-one-dimensional K-O chain in PTCDA thin films: evidence from first-principles calculations.

Using density functional theory calculations we have found that K atoms in a PTCDA (3,4:9,10-perylenetetracarboxylic dianhydride) crystal form a quasi-one-dimensional (1D) K-O chain interacting with carboxylic oxygen of the terminal anhydride groups of PTCDA. The K-K distance in the chain (3.72 Angstrom) is commensurate to the periodicity of the organic semiconductor. We obtain that the K-O structure is stabilized by charge transfer from K to PTCDA molecules, forming prevalently ionic bonds: the electronic density of the chemistry induced gap states is essentially delocalized on the perylene core of PTCDA, while potassium appears spoiled of its charge. Band dispersion along the direction of molecular stack is evaluated to be 0.2 eV in pure PTCDA crystal and 0.5 eV in the K-doped system, confirming that the interaction occurs between different molecular planes.

Propriedades estatísticas de parâmetros obtidos de sinais de ultra-som Doppler / Statistical properties of parameters extracted from doppler ultrasound waveforms

A variabilidade, distribuiçäo e variaçäo longitudinal de 13 parâmetros obtidos a partir da forma de onda de velocidade de fluxo sanguíneo, medida com ultra-som Doppler na artéria femoral, foram estudados em 9 registros de longa duraçäo obtidos em 7 pacientes. Os sinais foram gravados em fita magnética, juntamente com o eletrocardiograma, e analisados em um computador digital. O processamento desses dados forneceu o coeficiente de variaçäo para cada um dos índices estudados e os graus de liberdade por ponto, extraídos a partir da funçäo de autocorrelaçäo. A influência da frequência cardíaca na variabilidade de cada um dos parâmetros foi também verificada através de técnicas de correlaçäo cruzada. Como resultado final säo fornecidos os dados necessários para o dimensionamento correto de amostras para estimaçäo de cada um dos 13 parâmetros em estudos clínicos