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Item type:Publication, Effect of polyalcohols on the anticorrosive behaviour of alkyd coatings prepared with drying oils(Elsevier, 2020-08-01)Alkyd paints contain resins derived from vegetable oils. Alkyd resins have regained their importance since they are mostly composed of bio-based constituents recovered from biofuels production and agro-industrial waste. The anticorrosive performance of medium alkyd paints modified with Sacha inchi and linseed oils, and different ratios of glycerol and pentaerythritol, were compared by accelerated corrosion tests (Salt Fog and Sulphur Dioxide tests). This study focuses on comparing the effect of polyalcohol and oil type on physicochemical properties of resin solutions and cured films, and consequently, on the anticorrosive behaviour of paints prepared with the resins under study. Results showed that the mixture of pentaerythritol and Sacha inchi oil improves alkyd resin properties and enhance the anticorrosive performance of alkyd paints in accelerated weathering tests. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Development of the phase composition and the properties of Ti2AlC and Ti3AlC2 MAX-phase thin films – A multilayer approach towards high phase purity(Elsevier, 2020-09-15)MAX phase thin films have been synthesized by thermal treatment of a Ti-Al-C multilayer system. The preparation of the multilayer system was carried out via magnetron sputtering. Based on the thickness ratio among the individual nanoscale monolayers (Ti, Al, C), the resulting MAX phase stoichiometry can be controlled. This paper describes the synthesis of both Ti2AlC and Ti3AlC2 MAX phases from the same precursor multilayer system which is composed of a sequence of Ti/Al/C pure elemental single layers with thicknesses of 14, 6, and 3.5 nm, respectively. This sequence is repeated 22 times with a total thickness of around 500 nm. Rapid thermal treatment tests were performed to study the phase development. The Ti2AlC MAX phase forms in a temperature range below 850 °C, whereas the Ti3AlC2 MAX phase starts to form at temperatures above 850 °C and reaches its highest phase purity at 950 °C. The thin film structures were studied by X-ray diffraction and Raman spectroscopy. Furthermore, the electrical and mechanical properties were investigated to gain more insights regarding the phase transformation and their influence on the thin film properties. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Selective metallization of polymers: surface activation of polybutylene terephthalate (PBT) assisted by picosecond laser pulses(Wiley, 2021-11-09)The selective metallization of nonconductive polymer materials has broad applications in the fields of integrated circuit technology and metallized patterns. This work discusses a methodology to pattern metal tracks on polybutylene terephthalate substrates. The process consists of three steps: 1) surface patterning with picosecond laser pulses (1030 nm) in air, 2) Pd seeding via treatment in PdCl2 solution, and 3) selective metallization via electroless copper deposition. Picosecond laser irradiation promotes not only surface roughening but also chemical modification to enable Pd seeding as the polymer surface acquires the ability to reduce Pd(II)‐chloride species to metallic Pd. The laser parameters, as well as the PdCl2 concentration and seeding temperature, have an influence on the polymer surface morphology, the concentration and distribution of metallic Pd, and the copper layer properties. Homogeneous copper layers with well‐defined geometries, good coating‐substrate adhesion, and high electrical conductivity can be obtained. This is ascribed to the synergistic effect of the chemical surface activation and roughness development (from 0.13 to ≈1.6 μm). As the patterning and surface activation are performed in air, directly on the as‐received polymer substrate, this methodology shows great potential for metallization of electronic devices with 3D complex geometries. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrodeposition of cuprous oxide on a porous copper framework for an improved photoelectrochemical performance(Springer, 2021-07-01)Photoelectrochemical (PEC) water splitting can be an efficient and economically feasible alternative for hydrogen production if easily processed photoelectrodes made of inexpensive and abundant materials are employed. Here, we present the preparation of porous Cu2O photocathodes with good PEC performance using solely inexpensive electrodeposition methods. Firstly, porous Cu structures with delicate pore networks were deposited on flat Cu substrates employing hydrogen-bubble-assisted Cu deposition. In a second electrodeposition step, the porous Cu structures were mechanically reinforced and subsequently detached from the substrates to obtain free-standing porous frameworks. In a third and final step, photoactive Cu2O films were electrodeposited. The PEC water splitting performance in 0.5 M Na2SO4 (pH ∼6) shows that these photocathodes have photocurrents of up to −2.25 mA cm−2 at 0 V versus RHE while maintaining a low dark current. In contrast, the Cu2O deposited on a flat Cu sample showed photocurrents only up to −1.25 mA cm−2. This performance increase results from the significantly higher reactive surface area while maintaining a thin and homogeneous Cu2O layer with small grain sizes and therefore higher hole concentrations as determined by Mott-Schottky analysis. The free-standing porous Cu2O samples show a direct optical transmittance of 23% (λ = 400–800 nm) and can therefore be used in tandem structures with a photoanode in full PEC cells. Graphical [Figure not available: see fulltext.] - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting(IOP Publishing Ltd, 2021-05-13)The photoelectrochemical (PEC) properties of sputtered aluminum doped hydrogenated amorphous silicon carbide thin films grown on p-type crystalline silicon substrates were investigated in 1 M H 2 S O 4 solution under chopped light illumination. Optical and structural properties of the top absorber layer were systematically assessed after post-deposition isochronical annealing treatments. Samples exhibited a noticeable improvement of the opto-electronic properties after thermal treatments. In addition, an abrupt enhancement of the photocurrent was observed reaching a saturation value of 17 mA cm −2 at −1.75 V vs. Ag/AgCl (3.5 M KCl). In this research we propose that this enhancement effect is associated to a charge transfer kinetic mechanism influenced by surface states and the p-type substrate. The latter most likely due to the space charge region extending beyond the absorber layer reaching the substrate. Current density-potential and electrochemical impedance spectroscopy measurements in dark revealed a reduction of the S i O 2 native layer at cathodic potentials higher than −1 V vs. Ag/AgCl (3.5 M KCl), which contributes to the high charge transfer kinetic of the system. We believe that these results will contribute to understand the substrate influence in the PEC performance of top absorber layers in multilayer structures for solar water splitting. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Tribological and mechanical performance of Ti2AlC and Ti3AlC2 thin films(John Wiley and Sons Inc, 2022-10-01)Mn+1AXn (MAX) phases are novel structural and functional materials with a layered crystal structure. Their unique properties such as good machinability, high electrical conductivity, low friction, and corrosion resistance are appealing for many engineering applications. Herein, Ti2AlC and Ti3AlC2 MAX thin films are synthesized by magnetron sputtering and subsequent thermal annealing. A multilayer approach is used to deposit single-element nanolayers of titanium, aluminum, and carbon onto silicon substrates with a double-layer-diffusion barrier of SiO2 and SixNy. Ti2AlC and Ti3AlC2 thin films (thickness ≈500 nm) are formed via rapid thermal annealing and verified by X-Ray diffraction. Nanoindentation tests show hardness values of about 11.6 and 5.3 GPa for Ti2AlC and Ti3AlC2, respectively. The tribological behavior of the Ti2AlC and Ti3AlC2 thin films against AISI 52100 steel balls under dry sliding conditions is studied using ball-on-flat tribometry. The resulting coefficient of friction (CoF) for Ti2AlC and Ti3AlC2 ranges between 0.21–0.42 and 0.64–0.91, respectively. The better tribological behavior observed for Ti2AlC thin films is ascribed to its smaller grain size, reduced surface roughness, and higher hardness. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Localized surface states influence in the photoelectrocatalytic performance of Al doped a-SiC:H based photocathodes(Elsevier Ltd, 2022-06-01)In this work we evaluate the role of a-SiC:H(p)/SiO2 localized surface states (SS) in the Photoelectrochemical Water Splitting reaction. The analysis was carried out in three steps. First, retrieving the a-SiC:H(p) SS, energy distribution and density, by Electrochemical Impedance Spectroscopy techniques. Second, relating these results with direct measurements over the a-SiC:H(p)/SiO2 surface using X-ray Photoelectron spectroscopy. Finally, assessing the SS influence in the photo-induced hydrogen reduction by testing the a-SiC:H(p) photocathode with Linear Sweep Voltammetry. The whole analysis was done after subjecting the a-SiC:H(p) surface to different annealing treatments, i.e. 600 °C and 700 °C, necessary to obtain the required ohmic contacts. We believe that the participation of SS in an indirect electron charge transfer to the electrolyte, is kinetically feasible to take place in an a-SiC:H surface with relatively low SS density, ∼0.3×1012 cm-2. Whilst higher SS densities, in the range of ∼1.48×1014 cm-2, would trigger undesired charge carrier recombination. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Influence of deposition geometry on MAX phase formation in Ti–Al–C multilayer thin films(RELX Group (Netherlands), 2026-01-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Alkyds with Artistic Applications Based on Drying Oils, Multifunctional Polyalcohols and Different Polybasic Acids(John Wiley and Sons Inc, 2023-04-20)Today's requirements in the art field have challenged researchers to create artistic paintings with attractive appearance and long-term color stability. Alkyd-based art mediums have become an important group in the art field, because of their similar characteristics to traditional oils and exceptional drying properties. In this work, high solid alkyd-based art mediums have been synthesized by the monoglyceride and acidolysis processes. Multifunctional polyols and high unsaturated fatty acid sources were compared and used for alkyd synthesis. The use of a non-traditional oil of Peruvian origin is proposed. Resins have been characterized according to their physicochemical (acid number, viscosity, color and density) and drying properties. Drying tendencies were verified with the use of quartz crystal microbalance. Also, the behavior of the art mediums mixed with commercial oil paintings and a dry pigment, have also been evaluated. Results indicate that resins containing the polyol with the highest functionality are more viscous and have fewer tendencies to yellowing, while non-traditional Peruvian oil is the best option for creating light-colored art mediums. Alkyd mediums prepared by the monoglyceride method gave to oil paintings better characteristics and drying behavior on canvas.