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Publication Open Access Acoustic and psychoacoustic levels from an internal combustion engine fueled by hydrogen vs. gasoline(Elsevier, 2022) Arana Burgui, Miguel; San Martín Murugarren, Ricardo; Urroz Unzueta, José Carlos; Diéguez Elizondo, Pedro; Gandía Pascual, Luis; Zientziak; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaWhereas noise generated by road traffic is an important factor in urban pollution, little attention has been paid to this issue in the field of hydrogen-fueled vehicles. The objective of this study is to analyze the influence of the type of fuel (gasoline or hydrogen) on the sound levels produced by a vehicle with an internal combustion engine. A Volkswagen Polo 1.4 vehicle adapted for its bi-fuel hydrogen-gasoline operation has been used. Tests were carried out with the vehicle when stationary to eliminate rolling and aerodynamic noise. Acoustics and psychoacoustics levels were measured both inside and outside the vehicle. A slight increase in the noise level has only been found outside when using hydrogen as fuel, compared to gasoline. The increase is statistically significant, can be quantified between 1.1 and 1.7 dBA and is mainly due to an intensification of the 500 Hz band. Loudness is also higher outside the vehicle (between 2 and 4 sones) when the fuel is hydrogen. Differences in sharpness and roughness values are lower than the just-noticeable difference (JND) values of the parameters. Higher noise levels produced by hydrogen can be attributed to its higher reactivity compared to gasoline.Publication Open Access ADDISC lumbar disc prosthesis: analytical and FEA testing of novel implants(Elsevier, 2023) Vanaclocha, Amparo; Vanaclocha, Vicente; Atienza, Carlos M.; Jordá Gómez, Pablo; Díaz Jiménez, Cristina; García Lorente, José Antonio; Sáiz Sapena, Nieves; Vanaclocha, Leyre; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2The intact intervertebral disc is a six-freedom degree elastic deformation structure with shock absorption. “Ball-and-socket” TDR do not reproduce these properties inducing zygapophyseal joint overload. Elastomeric TDRs reproduce better normal disc kinematics, but repeated core deformation causes its degeneration. We aimed to create a new TDR (ADDISC) reproducing healthy disc features. We designed TDR, analyzed (Finite Element Analysis), and measured every 500,000 cycles for 10 million cycles of the flexion-extension, lateral bending, and axial rotation cyclic compression bench-testing. In the inlay case, we weighted it and measured its deformation. ADDISC has two semi-spherical articular surfaces, one rotation centre for flexion, another for extension, the third for lateral bending, and a polycarbonate urethane inlay providing shock absorption. The first contact is between PCU and metal surfaces. There is no metal-metal contact up to 2000 N, and CoCr28Mo6 absorbs the load. After 10 million cycles at 1.2–2.0 kN loads, wear 140.96 mg (35.50 mm3 ), but no implant failures. Our TDR has a physiological motion range due to its articular surfaces’ shape and the PCU inlay bumpers, minimizing the facet joint overload. ADDISC mimics healthy disc biomechanics and Instantaneous Rotation Center, absorbs shock, reduces wear, and has excellent long-term endurancePublication Open Access An alternative methodology for the evaluation of photocatalytic activity of polymeric coatings by monitoring dye degradation(MDPI, 2022) Sandúa Fernández, Xabier; Rivero Fuente, Pedro J.; Palacio, José F.; Esparza Gorráiz, Joseba; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2This work provides an alternative method for evaluating the photodegradation behaviour of different types of dyes such as Methylene Blue, Rhodamine B, Congo Red, Metanil Yellow, and Malachite Green. In this methodology, the coating is dyed with the chosen colorant and two beams of light are combined and channelled to a spot on the dyed coating through an optical fibre, the first one from an ultraviolet (UV) source (which is the responsible of activating photocatalysis) and the second one from a Visible light source, which is employed to monitor changes in colour along the time. The photocatalytic coating selected for testing this methodology consists of a mat of electrospun poly (acrylic acid) (PAA) fibres that acts as base film, furtherly coated by using layer-by-layer (LbL) assembly technique for the immobilization of two different photocatalytic metal oxide precursors (TiO2 and Fe2O3) nanoparticles. The morphological characterization of the samples has been implemented by means of scanning electron microscopy (SEM), confocal microscopy, and water contact angle measurements in order to analyse the resultant thickness, roughness, electrospun fibre diameter, and wettability. The experimental results clearly demonstrate the validity of the methodology to measure the photocatalytic activity in all dyed coatings, although significant differences have been observed depending on the selected dye.Publication Open Access Antibacterial functionalization of PVD coatings on ceramics(MDPI, 2018) Osés Martínez de Zúñiga, Javier; García Fuentes, Gonzalo; Palacio, José F.; García Lorente, José Antonio; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; IngenieríaThe application of surface treatments that incorporate silver or copper as antibacterial elements has become a common practice for a wide variety of medical devices and materials because of their effective activity against nosocomial infections. Ceramic tiles are choice materials for cladding the floors and walls of operation rooms and other hospital spaces. This study is focused on the deposition of biocide physical vapor deposition (PVD) coatings on glazed ceramic tiles. The objective was to provide antibacterial activity to the surfaces without worsening their mechanical properties. Silver and copper-doped chromium nitride (CrN) and titanium nitride (TiN) coatings were deposited on samples of tiles. A complete characterization was carried out in order to determine the composition and structure of the coatings, as well as their topographical and mechanical properties. The distribution of Ag and Cu within the coating was analyzed using glow discharge optical emission spectrometry (GD-OES) and field emission scanning electron microscope (FE-SEM). Roughness, microhardness, and scratch resistance were measured for all of the combinations of coatings and dopants, as well as their wettability. Finally, tests of antibacterial efficacy against Staphylococcus aureus and Escherichia coli were carried out, showing that all of the doped coatings had pronounced biocide activity.Publication Open Access An antibacterial surface coating composed of PAH/SiO2 nanostructurated films by layer by layer(Wiley, 2010) Urrutia Azcona, Aitor; Rivero Fuente, Pedro J.; Ruete Ibarrola, Leyre; Goicoechea Fernández, Javier; Fernández Valdivielso, Carlos; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería; Ingeniaritza; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISCIn this work we propose a novel antibacterial coating composed of SiO2 and the polymer Poly(allylamine hydrochloride) (PAH). The coating was fabricated by the technique Layer-by-Layer (LbL). This technique has already been used in previous works, and it has the advantage that it allows to control the construction of nanosized and well organized multilayer films. Here, the new nanotexturized LbL SiO2 surface acts as antibacterial agent. The fabricated coatings have been tested in bacterial cultures of genus Lactobacillus to observe their antibacterial properties. It has been demonstrated these PAH/SiO2 coating films have a very good antimicrobial behaviour against this type of bacteria.Publication Open Access Antifungal activity of chitosan/poly (ethylene oxide) blend electrospun polymeric fiber mat doped with metallic silver nanoparticles(MDPI, 2023) Murillo Larrey, Leire; Rivero Fuente, Pedro J.; Sandúa Fernández, Xabier; Pérez Garrido, Gumersinda; Palacio, José F.; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Multidisciplinary Research in Applied Biology - IMAB; Institute for Advanced Materials and Mathematics - INAMAT2In this work, the implementation of advanced functional coatings based on the combination of two compatible nanofabrication techniques such as electrospinning and dip-coating technology have been successfully obtained for the design of antifungal surfaces. In a first step, uniform and beadless electrospun nanofibers of both polyethylene oxide (PEO) and polyethylene (PEO)/chitosan (CS) blend samples have been obtained. In a second step, the dip-coating process has been gradually performed in order to ensure an adequate distribution of silver nanoparticles (AgNPs) within the electrospun polymeric matrix (PEO/CS/AgNPs) by using a chemical reduction synthetic process, denoted as in situ synthesis (ISS). Scanning electron microscopy (SEM) has been used to evaluate the surface morphology of the samples, showing an evolution in average fiber diameter from 157 ± 43 nm (PEO), 124 ± 36 nm (PEO/CS) and 330 ± 106 nm (PEO/CS/AgNPs). Atomic force microscopy (AFM) has been used to evaluate the roughness profile of the samples, indicating that the ISS process induced a smooth roughness surface because a change in the average roughness Ra from 84.5 nm (PEO/CS) up to 38.9 nm (PEO/CS/AgNPs) was observed. The presence of AgNPs within the electrospun fiber mat has been corroborated by UV-Vis spectroscopy thanks to their characteristic optical properties (orange film coloration) associated to the Localized Surface Plasmon Resonance (LSPR) phenomenon by showing an intense absorption band in the visible region at 436 nm. Energy dispersive X-ray (EDX) profile also indicates the existence of a peak located at 3 keV associated to silver. In addition, after doping the electrospun nanofibers with AgNPs, an important change in the wettability with an intrinsic hydrophobic behavior was observed by showing an evolution in the water contact angle value from 23.4° ± 1.3 (PEO/CS) up to 97.7° ± 5.3 (PEO/CS/AgNPs). The evaluation of the antifungal activity of the nanofibrous mats against Pleurotus ostreatus clearly indicates that the presence of AgNPs in the outer surface of the nanofibers produced an important enhancement in the inhibition zone during mycelium growth as well as a better antifungal efficacy after a longer exposure time. Finally, these fabricated electrospun nanofibrous membranes can offer a wide range of potential uses in fields as diverse as biomedicine (antimicrobial against human or plant pathogen fungi) or even in the design of innovative packaging materials for food preservation.Publication Open Access Chemical and mechanical stability of air annealed cathodic arc evaporated CrAlON coatings(Elsevier, 2018) Almandoz Sánchez, Eluxka; García Fuentes, Gonzalo; Palacio, José F.; Martínez de Bujanda Carasusán, Javier; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; IngenieríaThis study reports the synthesis and characterization of ternary Cr-Al-O and quaternary Cr-Al-O-N coatings deposited by cathodic arc physical vapour deposition, for various nitrogen and oxygen mass flow ratios during the growth process. The composition, microstructure, indentation hardness and modulus of the films have been characterized by scanning electron microscopy, electron probe micro-analysis, X-ray diffraction, and nanoindentation techniques. The evolution of the microstructure and mechanical properties of the coatings after ambient air annealing from 800 °C up to 1100 °C have been investigated. As the oxygen to nitrogen mass flow increases, the as-deposited coatings exhibit lower hardness, higher roughness, lower crystallinity and a more marked columnar structure. At oxygen to nitrogen mass flow ratios bigger than 10/90, the coatings exhibit a stoichiometry of the type (CrAl)2+εO3−ε. Only the coatings with an oxygen to nitrogen mass flow ratio smaller than 10/90 retained nitrogen in their compositions. In all cases, the coatings developed a cubic fcc lattice structure. After annealing at 1100 °C the resulting microstructure showed a clear dependency upon the initial composition of the films. The evolution of the microstructure during the high temperature tests, as well as the analysis of the nanoindentation hardness, composition and thickness also provided valuable information about the combined effects of the thermal stability and the oxidation of the deposited coatings.Publication Open Access Combining radiative cooling and light trapping strategies for improved performance of PERC bifacial silicon solar cells(Elsevier, 2023) Urdiroz Urricelqui, Unai; Itoiz Goñi, Iñigo; Sevilla Moróder, Joaquín; Andueza Unanua, Ángel María; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenThis work investigates the impact of combining light trapping and radiative cooling on bifacial solar panels. While several techniques have been proposed to enhance the efficiency of solar panels, their combination can lead to suboptimal results. By numerically evaluating the light absorption and thermal balance of different panel configurations, we found that each side of the bifacial solar cell can be textured independently with a cross-effect of less than 4%. However, our results also indicate that improving visible light trapping can increase infrared absorption, leading to a heating effect that may offset the benefits of radiative cooling. These findings highlight the importance of balancing the factors that influence solar panel efficiency and provide quantitative insights that guide the development of more effective solar energy systems.Publication Open Access Comparative performance of coke oven gas, hydrogen and methane in a spark ignition engine(Elsevier, 2020) Ortiz Imedio, Rafael; Ortiz, A.; Urroz Unzueta, José Carlos; Diéguez Elizondo, Pedro; Gorri, D.; Gandía Pascual, Luis; Ortiz, I.; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; IngenieríaIn this study, coke oven gas (COG), a by-product of coke manufacture with a high volumetric percentage of H2 and CH4, has been identified as auxiliary support and promising energy source in stationary internal combustion engines. Engine performance (power and thermal efficiency) and emissions (NOx, CO, CO2 and unburned hydrocarbons) of COG, pure H2 and pure CH4 have been studied on a Volkswagen Polo 1.4 L port-fuel injection spark ignition engine. Experiments have been done at optimal spark advance and wide open throttle, at different speeds (2000–5000 rpm) and various air-fuel ratios (λ) between 1 and 2. The obtained data revealed that COG combines the advantages of pure H2 and pure CH4, widening the λ range of operation from 1 to 2, with very good performance and emissions results comparable to pure gases. Furthermore, it should be highlighted that this approach facilitates the recovery of an industrial waste gas.Publication Open Access A comparative study in the design of TIO2 assisted photocatalytic coatings monitored by controlling hydrophilic behavior and rhodamine b degradation(MDPI, 2023) Sandúa Fernández, Xabier; Rivero Fuente, Pedro J.; Conde, Ana; Esparza Gorráiz, Joseba; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2This work presents a comparative study related to the photocatalytic efficiency associated with wettability measurements and organic dye degradation, as well as other relevant properties (i.e., corrosion resistance, roughness, wettability, and adhesion to a substrate). The photocatalytic precursors are titanium dioxide nanoparticles (TiO2 NPs) which are dispersed onto a polymeric electrospun fiber matrix by using three different deposition techniques such as electrospraying, spraying, and dip-coating, respectively. In this work, the host electrospun matrix is composed of poly(acrylic acid) fibers crosslinked with cyclodextrin (β-CD), which shows a good chemical affinity and stability with the other deposition techniques which are responsible for incorporating the TiO2 NPs. In order to evaluate the efficacy of each coating, the resultant photocatalytic activity has been monitored by two different tests. Firstly, the reduction in the water contact angle is appreciated, and secondly, the degradation of an organic dye (Rhodamine B) is observed under UV irradiation. In addition, the final roughness, adherence, and pitting corrosion potential have also been controlled in order to determine which solution provides the best combination of properties. Finally, the experimental results clearly indicate that the presence of TiO2 NPs deposited by the three techniques is enough to induce a super hydrophilic behavior after UV irradiation. However, there are notable differences in photocatalytic efficiency on the Rhodamine B as a function of the selected deposition technique.Publication Open Access A comparative study in the tribological behavior of DLC coatings deposited by HiPIMS technology with positive pulses(MDPI, 2020) García Lorente, José Antonio; Rivero Fuente, Pedro J.; Barba Areso, Eneko; Fernández, Iván; Santiago, José A.; Palacio, José F.; Fuente, Gonzalo G.; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; IngenieríaDuring the last few decades, diamond-like carbon (DLC) coatings were widely used for tribological applications, being an effective tool for improving the performance and the useful life of different machining tools. Despite its excellent properties, among which stand out a high hardness, a very low friction coefficient, and even an excellent wear resistance, one of the main drawbacks which limits its corresponding industrial applicability is the resultant adhesion in comparison with other commercially available deposition techniques. In this work, it is reported the tribological results of a scratch test, wear resistance, and nanoindentation of ta-C and WC:C DLC coatings deposited by means of a novel high-power impulse magnetron sputtering (HiPIMS) technology with 'positive pulses'. The coatings were deposited on 1.2379 tool steel which is of a high interest due to its great and wide industrial applicability. Finally, experimental results showed a considerable improvement in the tribological properties such as wear resistance and adhesion of both types of DLC coatings. In addition, it was also observed that the role of doping with W enables a significant enhancement on the adhesion for extremely high critical loads in the scratch tests.Publication Open Access A comparative study of multifunctional coatings based on electrospun fibers with incorporated ZnO nanoparticles(MDPI, 2019) Rivero Fuente, Pedro J.; Iribarren Zabalegui, Álvaro; Larumbe Abuin, Silvia; Palacio, José F.; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PRO-UPNA 18 (6107)In this work, polymeric fibers of polystyrene (PS) with incorporated ZnO nanoparticles have been deposited onto an aluminum alloy substrate (6061T6) by using the electrospinning technique. In order to optimize the deposition process, the applied voltage and flow rate have been evaluated in order to obtain micrometric electrospun fibers with a high average roughness and superhydrophobic behavior. Thermogravimetric analysis (TGA) has also been employed in order to corroborate the amount of ZnO incorporated into the electrospun fibers, whereas differential scanning calorimetry (DSC) has been performed in order to determine the glass transition temperature (Tg) of the polymeric electrospun fibers. In addition, a specific thermal treatment (Tg + 20 °C) of the synthesized electrospun fibers has been evaluated in the resultant corrosion resistance. A comparative study with previously reported results corresponding to polyvinyl chloride (PVC) fibers is carried out along this paper to show the changes in behavior due to the different compositions and fiber diameters. The coating has produced an important reduction of the corrosion current of the aluminum substrate in two orders of magnitude, showing also an important enhancement against pitting corrosion resistance. Finally, this deposition technique can be used as an innovative way for the design of both superhydrophobic and anticorrosive surfaces in one unique step over metallic substrates with arbitrary geometry.Publication Open Access Comparative study of supported Ni and Co catalysts prepared using the All-in-One method in the hydrogenation of CO2: effects of using (Poly)Vinyl Alcohol (PVA) as an additive(MDPI, 2024) Navarrete Rodríguez, Luisa Fernanda; Atienza Martínez, María; Reyero Zaragoza, Inés; Urroz Unzueta, José Carlos; Amorrortu, Oihana; Sanz Iturralde, Oihane; Montes, Mario; Garcés, Siby I.; Bimbela Serrano, Fernando; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; IngeniaritzaTwo series of Ni and Co catalysts supported onto La-Al2O3 were prepared and the CO2 hydrogenation reactions investigated. The catalytic performance was evaluated in terms of the evolution with the reaction temperature of the CO2 conversion and product (CH4 and CO) yields, as well as specific activities (TOF) and apparent activation energies. CH4 was the favored product over both metals while the TOF for CH4 formation was about three times higher for Ni than Co at 240–265 °C. Metallic particle size effects were found, with the TOF for CH4 formation decreasing over both Ni and Co as the mean metallic size decreased. In contrast, the TOF for CO formation tended to increase at a decreasing particle size for the catalysts with the smallest Ni particle sizes. The apparent activation energies for Ni and Co were very similar and significantly decreased to values of 73–79 kJ/mol when the metallic dispersion increased. The catalysts were prepared using the all-in-one method, resulting in (poly)vinyl alcohol (PVA) being a key additive that allowed us to enhance the dispersion of Ni and Co to give very effective catalysts. This comparative study joins the few existing ones in the literature in which catalysts based on these metals operated under strictly the same reaction conditions.Publication Open Access Comparative study of the metallurgical quality of primary and secondary AlSI10MnMg aluminium alloys(MDPI, 2021) Bakedano, Asier; Niklas, Andrea; Fernández‐Calvo, Ana Isabel; Plata, Gorka; Lozares, Jokin; Berlanga Labari, Carlos; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; IngenieríaThe use of secondary aluminium is increasingly being promoted in the automotive industry for environmental reasons. The purpose of this study was to demonstrate that it is possible to obtain a recycled AlSi10MnMg(Fe) aluminium alloy with equal metallurgical quality to that of a primary AlSi10MnMg alloy when an adequate melt treatment is applied. The melt treatment consisted of deoxidation, degassing and skimming in accordance with the detailed procedure described in this article. The metallurgical qualities of one primary and two secondary alloys were assessed using thermal analysis, the density index test, the macroinclusion test and the microinclusion level test before and after melt treatment. The thermal analysis allowed us to compare the variables of the solidification cooling curve (Al primary temperature and its undercooling; Al‐Si eutectic temperature and its predictive modification rate). The density index test was used to evaluate the hydrogen gas content in the melt. The macroinclusion test was used to evaluate the melt cleanliness, while the microinclusion level test was used to perform the inclusion identification and quantification analyses. This study showed the feasibility of manufacturing structural components using 100% recycled secondary aluminium alloy through V‐ HPDC technology.Publication Open Access Comparative study of tribomechanical properties of HiPIMS with positive pulses DLC coatings on different tools steels(MDPI, 2021) Claver Alba, Adrián; Jiménez-Piqué, Emilio; Palacio, José F.; Almandoz Sánchez, Eluxka; Fernández de Ara, Jonathan; Fernández, Iván; Santiago, José A.; Barba Areso, Eneko; García Lorente, José Antonio; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; IngenieríaDiamond-like carbon (DLC) coatings are very interesting due to their extraordinary properties; their excellent wear resistance, very low friction coefficient, great hardness, high elastic modulus or biocompatibility can be highlighted, as can their multifunctionality. Because of this, over recent decades they have been widely used in tribological applications, improving the performance and the useful life of machining tools in an effective way. However, these coatings have a disadvantage compared to other coatings deposited by commercially available techniques-their resultant adhesion is worse than that of other techniques and limits their industrial applications. In this work, tribological results of a scratch test, wear resistance and nanoindentation of tetrahedral amorphous carbon (ta-C) and tungsten carbide:carbon (WC:C) DLC coatings deposited by means of novel highpower impulse magnetron sputtering (HiPIMS) technology with positive pulses are reported. The coatings were deposited in three different tools steels: K360, vanadis 4 and vancron. These tools' steels are very interesting because of their great and wide industrial applicability. Experimental results showed excellent tribological properties, such as resistance to wear or adhesion, in the two types of DLC coatings.Publication Open Access Complex selective manipulations of thermomagnetic programmable matter(Springer Nature, 2022) Irisarri Erviti, Josu; Ezcurdia Aguirre, Íñigo Fermín; Sandúa Fernández, Xabier; Galarreta Rodríguez, Itziar; Pérez de Landazábal Berganzo, José Ignacio; Marzo Pérez, Asier; Ciencias; Zientziak; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISCProgrammable matter can change its shape, stiffness or other physical properties upon command. Previous work has shown contactless optically controlled matter or magnetic actuation, but the former is limited in strength and the latter in spatial resolution. Here, we show an unprecedented level of control combining light patterns and magnetic fields. A mixture of thermoplastic and ferromagnetic powder is heated up at specific locations that become malleable and are attracted by magnetic fields. These heated areas solidify on cool down, and the process can be repeated. We show complex control of 3D slabs, 2D sheets, and 1D filaments with applications in tactile displays and object manipulation. Due to the low transition temperature and the possibility of using microwave heating, the compound can be manipulated in air, water, or inside biological tissue having the potential to revolutionize biomedical devices, robotics or display technologies.Publication Open Access A comprehensive study on hot corrosion resistance of NiCoCrAlYTa and NiCrAl thermal-sprayed coatings for CSP applications(Elsevier, 2023) Aristu Ojer, Daniel; Berlanga Labari, Carlos; Alberro, Mikel; Rández Diago, Xabier; Fernández, Ángel G.; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2The new generation of concentrated solar power (CSP) plants could be able to work at temperatures up 650 °C and carbonates molten salts are one of the main candidates to be used as thermal energy storage (TES) materials. Molten salt corrosion has been defined as one of the main issues and the technology demands more resistance alloys and innovative coatings. In this study, the assessment of hot corrosion resistance for NiCoCrAlYTa and NiCrAl thermal-sprayed coatings has been undertaken, tested on a ternary eutectic mixture (Li2CO3-Na2CO3-K2CO3) at a temperature of 650 °C. Electrochemical impedance spectroscopy and linear polarization resistance tests were used to evaluate the behaviour of the coatings but the obtained results reveal high values of corrosion rates accompanied by the formation of cracks. This unsatisfactory performance of the coatings, analysed by scanning electron microscopy and x-ray diffraction, can be attributed to a combination of different factors such as porosity, internal material stresses and thermal diffusion phenomena. As a result, it is concluded that further research is necessary to explore new coating application techniques.Publication Open Access Design of photocatalytic functional coatings based on the immobilization of metal oxide particles by the combination of electrospinning and layer-by-layer deposition techniques(MDPI, 2022) Sandúa Fernández, Xabier; Rivero Fuente, Pedro J.; Esparza Gorráiz, Joseba; Palacio, José F.; Conde, Ana; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Gobierno de Navarra / Nafarroako GobernuaThis work reports the design and characterization of functional photocatalytic coatings based on the combination of two different deposition techniques. In a first step, a poly(acrylic acid) + β-Cyclodextrin (denoted as PAA+ β-CD) electrospun fiber mat was deposited by using the electrospinning technique followed by a thermal treatment in order to provide an enhancement in the resultant adhesion and mechanical resistance. In a second step, a layer-by-layer (LbL) assembly process was performed in order to immobilize the metal oxide particles onto the previously electrospun fiber mat. In this context, titanium dioxide (TiO2 ) was used as the main photocatalytic element, acting as the cationic element in the multilayer LbL structure. In addition, two different metal oxides, such as tungsten oxide (WO3 ) and iron oxide (Fe2O3 ), were added into PAA anionic polyelectrolyte solution with the objective of optimizing the photocatalytic efficiency of the coating. All of the coatings were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images, showing an increase in the original fiber diameter and a decrease in roughness of the mats because of the LbL second step. The variation in the wettability properties from a superhydrophilic surface to a less wettable surface as a function of the incorporation of the metal oxides was also observed by means of water contact angle (WCA) measurements. With the aim of analyzing the photocatalytic efficiency of the samples, degradation of methyl blue (MB) azo-dye was studied, showing an almost complete discoloration of the dye in the irradiated area. This study reports a novel combination method of two deposition techniques in order to obtain a functional, homogeneous and efficient photocatalytic coating.Publication Open Access Designing multifunctional protective PVC electrospun fibers with tunable properties(MDPI, 2020) Rivero Fuente, Pedro J.; Rosagaray Burdaspar, Iker; Fuertes Bonel, Juan Pablo; Palacio, José F.; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA1929In this work, the electrospinning technique is used for the fabrication of electrospun functional fibers with desired properties in order to show a superhydrophobic behavior. With the aim to obtain a coating with the best properties, a design of experiments (DoE) has been performed by controlling several inputs operating parameters, such as applied voltage, flow rate, and precursor polymeric concentration. In this work, the reference substrate to be coated is the aluminum alloy (60661T6), whereas the polymeric precursor is the polyvinyl chloride (PVC) which presents an intrinsic hydrophobic nature. Finally, in order to evaluate the coating morphology for the better performance, the following parameters-such as fiber diameter, surface roughness (Ra, Rq), optical properties, corrosion behavior, and wettability-have been deeply analyzed. To sum up, this is the first time that DoE has been used for the optimization of superhydrophobic or anticorrosive surfaces by using PVC precursor for the prediction of an adequate surface morphology as a function of the input operational parameters derived from electrospinning process with the aim to validate better performance.Publication Open Access Diffuse irradiance on tilted planes in urban environments: evaluation of models modified with sky and circumsolar view factors(Elsevier, 2021) García Ruiz, Ignacio; Blas Corral, María Ángeles de; Hernández Salueña, Begoña; Sáenz Gamasa, Carlos; Torres Escribano, José Luis; Ingeniaritza; Zientziak; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; CienciasNumerous studies have analyzed existing irradiance models for estimating sky diffuse irradiance on tilted planes. However, few have evaluated the suitability of these models for estimating irradiance in obstructed environments, specifically considering the effects of obstacles. In this study, three irradiance models —one of them with five variants— for estimating diffuse irradiance on tilted planes located in urban environments were evaluated. All models have been adapted to consider the effect of an urban canyon on the diffuse irradiance received on a tilted plane through the sky view factor and the circumsolar view factor. All the models were evaluated against the diffuse irradiance values obtained by the ISO 15469:2004(E)/CIE S 011/E:2003 angular distribution model. Therefore, it was necessary to determine the standard sky type corresponding to each record of the measurements performed by a sky scanner at the radiometric station of UPNA (Spain). A total of 4,864 scenarios were considered to occur from the combination of different orientations and inclinations of the plane, and different orientations and aspect ratios of the urban canyon. The results revealed that the Perez model considering a 35° half-angle circumsolar region has the best performance, followed by the Perez model considering a 45° half-angle circumsolar region.
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