Browsing by Keyword "Surfaces, Coatings and Films"
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Item Antireflective mesoporous silica coatings by optimization of water content in acid-catalyzed sol-gel method for application in glass covers of concentrated photovoltaic modules(2019-01-15) Agustín-Sáenz, Cecilia; Machado, Maider; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOSPorous silica layers with outstanding antireflective properties have been prepared by acid-catalyzed sol-gel process in presence of organic phases as structure directing agents (SDA) and excess water, with the aim of offering a cost-competitive, easy up-scaling and high efficiency process that contributes to reduce current levelized cost of energy (LCOE) of concentrating photovoltaics (CPV). The process has been optimized by controlling the water/alkoxide ratio, which is an important structure-regulating tool, having a strong influence in the structural properties of sol-gel synthesized materials. Hydrolysis of the inorganic precursor has been accomplished in high water/alkoxide conditions and in the presence of SDAs. Evaporation induced self-assembly (EISA) during coating deposition and the scanning of four types of SDAs have permitted to select the coating that fulfilled specific thickness and refractive index values with, in parallel, excellent results on sol stability. The final optimization has produced mesoporous coatings with ∼9 nm mean pore size, leading to an enhancement in transmittance up to 7.4% over bare glass in the 300–1500 nm wavelength range. The transmittance spectra have been used as inputs for the theoretical calculation of the short-circuit current density of a commercially available multijunction solar cell for CPV applications.Item Bone cell adhesion on ion implanted titanium alloys(2005-06-22) Braceras, I.; Onate, J.I.; Goikoetxea, L.; Viviente, J.L.; Alava, J.I.; de Maeztu, M.A.; Tecnalia Research & Innovation; Biomateriales; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSThe authors have previously reported than ion implantation can have a significant effect on osseointegration of an implant, specially when the latter is introduced in areas of poorer bone density. These results indicate that this process is particularly suited for implant devices introduced in elderly patients or in those regions that have a poor quality of bone. The aim of this work is directed to study osteoblast adhesion on Ti alloy surfaces with different ion implantation treatments, so osseoconductive properties of several surfaces can be assessed. Polished discs of Ti–6Al–4V and Ti CP GR1 titanium alloy have been prepared and ion implanted with different species and parameters (dose and energy). Afterwards, the samples have been sterilized by UV light, inoculated with 1.5×105 human bone cells and incubated during 4 h at 37 C and 5% CO2 atmosphere. Then, once fixed and rinsed, image analysis has been used to quantify the number of cells attached to the Ti discs. On a second round of tests, cell proliferation tests have been conducted during 24, 48, 144 and 192 h, respectively. Furthermore, surface analysis techniques (e.g. AFM) have been applied to learn about the qualitative behavior, i.e. morphology, of the attached cells. Cell attachment has shown to be highly sensitive to ion implantation parameters. Although some quantitative differences have been observed, the more significant differences were qualitative. AFM analysis has shown that the star-shaped bone cells attached spread more and occupied larger surfaces like in osseointegration prone surfaces, most probably due to extracellular matrix synthesized around them, while other surfaces showed mainly large and narrow shaped or round shaped bone cells often with great cellular nucleus in the middle of the cells and little extracellular matrix around. So, ion implanted surfaces that facilitate osseointegration have been identified, in terms of initial bone cell attachment quality, where although the number of attached cells were not necessarily always larger, they tended to occupy wider areas with healthier cells.Item Broadband antireflective coating stack based on mesoporous silica by acid-catalyzed sol-gel method for concentrated photovoltaic application(2018-11) Agustín-Sáenz, Cecilia; Sánchez-García, José Ángel; Machado, Maider; Brizuela, Marta; Zubillaga, Oihana; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; INGENIERÍA DE SUPERFICIES; SISTEMAS FOTOVOLTAICOSSilica multi-layer stacks have been designed with the aim to provide broadband antireflective (AR) properties for glass components in concentrated photovoltaic (CPV) application. Silica porous coatings were grown by combining acid-catalyzed sol-gel route and evaporation induced self-assembly (EISA) method with four types of organic/inorganic systems. Sols were prepared using tetraethylorthosilicate (TEOS) as inorganic precursor assembled with two di-block copolymers, one tri-block copolymer and one cationic surfactant as organic templates. Optical properties were characterized by ellipsometry and spectrophotometry while the material structure was analyzed by environmental ellipsometric porosimetry (EEP) and atomic force microscopy (AFM). The concentration of inorganic and organic phases was optimized and a broadband AR bi-layer stack was obtained providing a 7.2% (under the reference AM1.5 solar spectral irradiance) increase in transmittance over bare glass in the wavelength range 300–2000 nm when coated on both sides.Item Characterization of Inconel 718® superalloy fabricated by wire Arc Additive Manufacturing: effect on mechanical properties and machinability: effect on mechanical properties and machinability(2021-09) Alonso, Unai; Veiga, Fernando; Suárez, Alfredo; Gil Del Val, Alain; Tecnalia Research & Innovation; FABRIC_INTELWire and Arc Additive Manufacturing has the potential to become an appropriate technique to produce large complex-shaped metallic parts. However, a post-processing machining operation is necessary to reach the final geometry. In this work, Inconel 718 walls were manufactured in a monitored environment and their microstructure and mechanical properties were characterised. Then, slot milling operations were performed to investigate the influence of cutting speed and machining direction. The conclusions drawn from this article can be used as a guide for a correct definition of strategies and milling parameters. It was observed that at higher cutting speeds a better surface quality and lower torques are obtained. Moreover, the main novelty of this work is that is shows the influence of the anisotropy of WAAM-Inconel 718 on its machinability. Milling along the torch's travel direction offers better dimensional tolerance values with lower cutting torques, being more favourable than machining in the building direction.Item Characterization of nanostructured Ti–B–(N) coatings produced by direct current magnetron sputtering(2007-02-26) López-Cartes, C.; Martínez-Martínez, D.; Sánchez-López, J.C.; Fernández, A.; García-Luis, A.; Brizuela, Marta; Onate, J.I.; TECNOLOGÍAS DE HIDRÓGENO; INGENIERÍA DE SUPERFICIES; Tecnalia Research & InnovationA series of Ti–B–(N) coatings prepared by dc magnetron sputtering using TiB2 targets in Ar/N2 gas mixtures has been chemically and structurally characterized by transmission electron microscopy, X-ray diffraction, electron energy-loss spectroscopy, and X-ray photoelectron spectroscopy. The influence of synthesis parameters such as applied heating power and nitrogen flow on the structure and chemical composition of the coatings has been studied. Independently of the experimental conditions employed during the synthesis, hexagonal TiB2 is the main crystalline phase present in the coatings. The use of N2 leads to the formation of an amorphous mixture of BN/TiN phases, as well as a diminution of the TiB2 crystalline phase. The influence of the composition and structure of the coatings on their hardness is also discussed.Item Chromium-free conversion coatings based on inorganic salts(Zr/Ti/Mn/Mo) for aluminum alloys used in aircraft applications(2015-08-01) Santa Coloma, Patricia; Izagirre, Usoa; Belaustegui, Yolanda; Jorcin, J.B.; Cano, F.J.; Lapeña, N.; Belaustegi, Y.; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; VALORIZACIÓN DE RESIDUOS; MATERIALES PARA CONDICIONES EXTREMAS; SGNovel chromium-free conversion coatings based on Zr/Ti/Mn/Mo compounds were developed at a pilot scale to improve the corrosion resistance of the AA2024-T3 and AA7075-T6 aluminum alloys for aircraft applications. The influence of the presence of Zr and Ti in the Zr/Ti/Mn/Mo conversion bath's formulation on the corrosion resistance of the coated alloys was investigated. The corrosion resistance provided by the conversion coatings was evaluated by salt spray exposure and potentiodynamic sweeps. Optical and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and atomic force microscopy (AFM) operating in the Kelvin Probe mode (SKPFM) were used to provide microstructural information of the coated samples that achieved the best results in the corrosion tests. The salt spray test evidenced the higher corrosion resistance of the coated samples compared to the bare surfaces for both alloys. The potentiodynamic tests showed that the corrosion current density decreased for coated AA7075-T6 and AA2024-T3 alloys, which indicated an obvious improvement of the corrosion resistance with all the processes for both alloys. Although the corrosion resistance of the coated samples appeared to be higher for the alloy AA7075-T6 than for the alloy AA2024-T3, both alloys achieved the best corrosion protection with the coatings deposited from conversion bath formulations containing no titanium salts. The microscopy analysis on the coated AA7075-T6 samples revealed that a local deposition of Zr compounds and, possibly, an oxidation process occurred in the vicinity of the alloy's intermetallic particles. The amount of the Zr deposits at these locations increased with coating's formulations without Ti, which provided the best corrosion resistance. The Cr-free conversion coatings developed in this study for the AA7075-T6 and AA2024-T3 alloys do not meet yet the strict requirements of the aircraft industry. However, they significantly improved the corrosion performance with respect to the bare alloys and could be a good starting point for further studies and optimization.Item Composite material incorporating protective coatings for photovoltaic cell encapsulation(2022-09-15) Yurrita, Naiara; Aizpurua, Jon; Cambarau, Werther; Imbuluzqueta, Gorka; Hernández, Juan M.; Cano, Francisco J.; Huerta, Irene; Rico, Elena; Caño, Teodosio del; Wölper, Sarah; Haacke, Florian; Zubillaga, Oihana; Tecnalia Research & Innovation; SISTEMAS FOTOVOLTAICOS; SGPhotovoltaic modules consisting of one back-contact cell were manufactured by vacuum resin infusion process using glass reinforced epoxy composite as encapsulant where the cells are embedded. Incorporation of three coatings onto the composite surface was studied with the aim to improve the electrical performance stability of the modules under ultraviolet (UV), thermal cycling and damp-heat environmental weathering. Photovoltaic and aging performance were examined through the short-circuit current density values and colour change of the composite. Decrease in the initial photovoltaic performance of the modules was caused by the coating deposition. The highest drop in the initial values was observed for the varnish type coating, showing a decrease of 2.6% in short-circuit current. Regarding the performance stability, the decrease was more pronounced in the damp-heat test, presenting the varnish type coating the minimum loss of 1.4% in short-circuit current and a variation of 87% in b* chromatic parameter after 1000 h exposure at 85 °C and 85% relative humidity. The study concluded that the protective coating should be selected to provide the composite modules with an optimal trade-off between the initial electrical performance and the desired stability, with further research work targeted to improve moisture barrier properties.Item Composite material with enhanced ultraviolet performance stability for photovoltaic modules(2019-09-15) Imbuluzqueta, Gorka; Yurrita, Naiara; Aizpurua, Jon; Cano, Francisco J.; Zubillaga, Oihana; SISTEMAS FOTOVOLTAICOS; SGThe present work aims encapsulating photovoltaic cells in glass reinforced epoxy composite by vacuum resin infusion, incorporating additives directed to enhance the performance stability of the manufactured photovoltaic modules under ultraviolet (UV) exposure. UV absorber (UVA) and hindered amine light stabilizer (HALS) additives were incorporated in the resin system in different content. Photovoltaic performance and stability under UV radiation exposure were studied through external quantum efficiency (EQE) spectra, chromatic coordinates and short-circuit current values. Decrease in current values and increase in yellowness were observed in the presence of UVA and HALS. However, an enhanced performance stability was observed when additives are incorporated, improving the stability when increasing the additive amount. The most stable module, with cells embedded in 2% additive containing composite, showed a 2.7% short-circuit current loss after UV aging exposure.Item Corrosion preserving high density plasma treatment of precipitation hardening stainless steel(2018-12-15) Braceras, Iñigo; Ibáñez, Iñigo; Domínguez-Meister, Santiago; Urgebain, Aiala; Sánchez-García, Jose Angel; Larrañaga, Aitor; Garmendia, Iñaki; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; MATERIALES PARA CONDICIONES EXTREMASSpecialty alloys such as precipitation hardening stainless steels are routinely used in critical applications requiring high strength and corrosion resistance, e.g. in aeronautics, in ground transportation and the biomedical field. Nonetheless, their tribological properties remain poor, while the application of surface treatments results in loss of corrosion resistance. Therefore, typically a not fully satisfactory compromise must be adopted. In the present work, the improvement of tribological features, without loss of corrosion resistance, of the 1.4545 (15-5PH) steel has been explored with the use of high density plasmas. The work has focused on long cylindrical geometries, close to those of real applications. The microstructure and composition of the treated surfaces were studied and the corresponding corrosion resistance stablished. The characteristics of the high density plasmas as well as the sample disposition were key factors in the outcomes, which ranged from fully corroded to corrosion resistant surfaces. Results also showed in certain cases the high density plasmas causing surface cracks followed by local corrosion. Additionally tribological studies demonstrated improvement in wear resistance, and electrical contact resistance (ECR) was found to be a good indicator of the wear phenomena occurring along the tests. An equivalent electric circuit is proposed. Actually ECR could be a useful and simple way of monitoring the surface status and assist in assuring safe and dependable operational lives of the components. In conclusion, treatment conditions of cylindrical 1.4545 (15-5PH) have been defined, which provide with an improved tribological performance, preserving corrosion resistance, with ECR a useful performance monitoring parameter.Item Corrosion testing device for in-situ corrosion characterization in operational molten salts storage tanks: A516 Gr70 carbon steel performance under molten salts exposure: A516 Gr70 carbon steel performance under molten salts exposure(2016-12-01) Ruiz-Cabañas, F. Javier; Prieto, Cristina; Osuna, Rafael; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASConcentrated solar power (CSP) generation is becoming a very important player within the renewable energy sector thanks to increased introduction of these facilities into the conventional electricity market. CSP plants become dispatchable when integrating thermal energy storage (TES) systems which allow electricity production at any time of the year. Sensible TES using nitrate salts mixtures as storage fluid are the most extended arrangement for commercial CSP facilities. In addition to storage time, dimensions, thermal-mechanical requirements, among others, corrosion compatibility between high temperature nitrate salts, and structural materials is a key factor to take into consideration for the final storage system design. Many scientific contributions have been developed regarding metallic alloys corrosion performance in nitrate salts at laboratory scale. Accordingly, lack of technical background is identified about nitrates corrosion in relevant operation conditions. Therefore, a corrosion testing device (CTD) was designed to evaluate corrosion behavior of structural materials inside high temperature nitrate salts storage tanks in operation. Furthermore, A516 Gr70 carbon steel was evaluated at different exposures times by using the CTD in the TES-PS10 pilot plant. Results reported within this study show the feasibility of the CTD to be used at commercial scale allowing corrosion preventive maintenance practices and materials selection optimization. Moreover, A516 Gr70 carbon steel displayed an excellent corrosion performance after nitrate salts exposure being recommended for long time service under continuous and intermittent exposure to nitrate salts. In addition to low corrosion rates, carbon steel generated protective and well adhered iron oxide layers without significant localized phenomena. Finally, negligible susceptibility to crevice and stress corrosion cracking (SCC) phenomena is showed by carbon steel under test conditions.Item Design of Corrosion Protective and Antistatic Hybrid Sol-Gel Coatings on 6XXX AlMgSi Alloys for Aerospace Application(2020-04-30) Agustín-Sáenz, Cecilia; Santa Coloma, Patricia; Fernández-Carretero, Francisco J.; Brusciotti, Fabiola; Brizuela, Marta; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; TECNOLOGÍAS DE HIDRÓGENO; INGENIERÍA DE SUPERFICIESAn inorganic–organic coating based on glycidyl-functionalized silica and zirconia was synthesized by sol-gel technology to protect three types of AlMgSi (6XXX series) alloys against corrosion in aerospace applications. Different parameters such as the solid content, the organic/inorganic ratio of the sols and the deposition conditions were studied with the aim to achieve a tradeoff between the corrosion protection, antistatic performance and low vacuum-induced outgassing. Those parameters directly influence the thickness and the density of the coatings, and therefore the barrier effect against corrosion and the contact electrical resistance, which are affected in opposite ways. To obtain a low contact electrical resistance, silver nanowires (NW) with a high aspect ratio were loaded in the sol-gel matrix with the aim to create a conductive path through the hybrid coating with a low concentration of NWs. The coatings were adapted for AA6063, AA6061 and AA6082, and they all showed an outstanding anti-corrosion performance in different artificial weathering tests, whereas electrochemical impedance spectroscopy permitted the identification of the most critical parameters affecting water uptake. An antistatic performance was demonstrated by the low contact electrical resistance of the coated AA6061 and AA6063 alloys, although the incorporation of NWs showed a detrimental effect on the corrosion protection compared with the unloaded coatingItem Development of Beta Titanium Alloys by Spark Plasma Sintering(2017) Lagos, M.A.; Amigo, A.; Vicente, A.; Agote, Iñigo; EXTREMATBeta titanium alloys have attracted considerable attention especially for orthopedic implants applications owing to their unique combination of low elastic modulus, superior bio-corrosion resistance and excellent biocompatibility. However, the PM production of these alloys is difficult due to the significant amount of refractory metals (Ta, Mo, Zr, Nb, etc). This work presents a processing route combining mechanical mixing of elemental powders (pre-alloying) and Spark Plasma Sintering in order to obtain fully dense materials with homogeneous microstructure. Two different compositions (TiMo and TiNb) with high amount of alloying elements were developed. The alloys were sintered at temperatures between 1100 and 1250ºC. The phases were evaluated by X-ray diffraction and diffraction of backscattered electrons, appreciating its mechanical properties by micro-hardness and bending tests. A transformation to Beta Titanium is obtained predominantly with a small grain size, and micro-hardness in the order of forged materials.Item Effect of addition of silica- and amine functionalized silica-nanoparticles on the microstructure of calcium silicate hydrate (C-S-H) gel(2015-07-05) Monasterio, Manuel; Gaitero, Juan J.; Erkizia, Edurne; Guerrero Bustos, Ana M.; Miccio, Luis A.; Dolado, Jorge S.; Cerveny, Silvina; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNIn this work we study the influence of adding nano-silica (SiO2, Nyasil™) and aminopropyl (-(CH2)3-NH2,) functionalized silica nanoparticles (Stoga) during the synthesis of calcium-silicate-hydrate (C-S-H gel). Characterization by solid state 29Si NMR and ATR-FTIR spectroscopy showed that the addition of both particle types increases the average length of the silicate chains in C-S-H gel being this effect slightly more important in the case of Stoga particles. In addition, 13C NMR and XPS confirmed that the aminopropyl chain remains in the final product cleaved to silicon atoms at the end of the silicate chain of C-S-H gel whereas XRD measurements showed that this result in an increment in the basal distance compared with ordinary CSH. In addition, the dynamics of water within the pores of C-S-H gel was analyzed by broadband dielectric spectroscopy. We observed that water confined in C-S-H formed with the addition of nanoparticles is faster than that in plain C-S-H which can be related to a different porous structure in these materials.Item Effect of Different Nanoparticles on Mechanical Properties and Curing Behavior of Thermoset Polyurethane Adhesives(2014-10-03) Rodriguez, R.; Perez, B.; Florez, S.; POLIMEROSThree different kinds of nanoparticles (nano-Al2O3, nano-SiO2, and nano-CaCO3) were incorporated into a thermoset polyurethane adhesive. The influence of the type of nanoparticle and concentration on nanoadhesives mechanical, rheological properties, and dispersion degree was analyzed. It was found that as nanoparticle concentration increases tensile strength and Young’s modulus increases. However, there was a maximum concentration from which mechanical properties were reduced. Nanoadhesive mechanical properties were controlled by nanoparticles specific surface area, hardness, and surface treatment. In addition, it was found that the addition of nanoparticles accelerates nanoadhesives curing rate.Item Effects of ion implantation on nano-topographic properties(2007-08-05) Braceras, I.; Briz, N.; García, F.; Muñoz, R.; Viviente, J.L.; Onate, J.I.; INGENIERÍA DE SUPERFICIES; SG; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Tecnalia Research & InnovationIt is well known that surface properties at nano-scale are determinant in a number of applications, such as sensors, biomedical and optical devices. Nevertheless, relations between surface treatment parameters and their effects on topography at the nano-scale, surface energy or light reflectivity are often poorly understood. In this study, a non fluorescent glass material (Knittel) was selected and subjected to ion implantation treatments with different parameters and species, including Ar, Ne, C, N, CO and NH2. The resulting surface topography at the nano-scale was studied by Atomic Force Microscopy (AFM) and the surface energy was evaluated with the contact angle method. Additionally, the modifications induced on optical properties, i.e. reflection, were evaluated with two different wavelength lasers. The results showed remarkable differences in surface nano-topographies and contact angles (from 15° to 70°) that were obtained. Furthermore, the effects of ion implantation parameters had also very significant consequences on background noise effects, of great importance for optical properties. It was found that the best implantation treatment corresponded to N2 + ions implanted to a dose of 3×1017 ions/cm2 at an energy of 30 keV. This treatment resulted in a adequate contact angle, producing a nano-textured surface with potential features for a good attachment and orientation of deposited bio-molecules, and a very low background fluorescence, hence allowing a high degree of scanning sensitivity, for application on DNA microarrays. The study has shown that ion implantation represents a powerful tool for modifying key properties on surfaces that play an important role in the response elicited on living tissue and bio-molecules, which is notoriously relevant for the application as bio-sensors.Item Effects of laser-textured on rake face in turning PCD tools for Ti6Al4V(2021-11-01) Fernández-Lucio, P.; Villarón-Osorno, I.; Pereira Neto, O.; Ukar, E.; López de Lacalle, L.N.; Gil del Val, A.; FABRIC_INTELThe demand inherent to the aeronautical industry in terms of productivity and quality requirements leads to develop new cutting tools. Hence, PCD tools meet the requirements in productivity while machining low machinability aeronautical alloys such as Ti6Al4V. Tool chipbreakers play a considerable role in terms of tool life. However, due to the extreme conditions (temperature and pressure) required to manufacture PCD tools, any complex geometry on tool rake faces is not viable, so chipbreakers are not possible, except for those external to inserts. This work proposes a groove-type laser engraved chipbreaker design and a manufacturing methodology, with experimental validation on turning a Ti6Al4V workpiece. The so-manufactured chipbreakers achieve titanium alloy chip fragmentation, making easy chip removal from the cutting zone. A set of experiments involving various laser parameters to characterize the PCD depth and surface integrity and experimental validation for those chipbreakers designs were carried out in finishing cutting conditions. The optimum parameters for the engraving of PCD were found, obtaining satisfactory breakage of titanium chips. Chip length was always below 17.29 mm.Item Electrical contact resistance and tribological behaviors of self-lubricated dielectric coating under different conditions(2020-03) Echeverrigaray, F.G.; de Mello, S.R.S.; Leidens, L.M.; Boeira, C.D.; Michels, A.F.; Braceras, I.; Figueroa, C.A.; INGENIERÍA DE SUPERFICIESIn this study, the electro-tribological performance of hydrogenated amorphous carbon coatings against bearing steel in different experimental conditions was continuously monitored by means of coefficient of friction (CoF) and electrical contact resistance (ECR). The influence of tribosystem variables such as humidity, velocity and lifetime on frictional and electrical response were also compared with specific wear energy calculation method. The main findings of both tribological and electrical behaviors include the dissipated energy and the micro-slip dielectric failures that can be linked to the properties of self-lubricating layers, which depend also on the working media. In this framework, the electro-tribological evaluation provides an electrical monitoring tool for coating premature wear detection in real time.Item Electro-tribological properties of diamond like carbon coatings(2019-06-07) Braceras, Iñigo; Ibáñez, Iñigo; Dominguez-Meister, Santiago; Velasco, Xabier; Brizuela, Marta; Garmendia, Iñaki; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIESDiamond like carbon (DLC) coatings typically present good self-lubricating tribological properties that could be of interest in sliding dielectric contacts in multiple electrical applications. In this work electro-tribological studies have been performed on several DLC coatings against aluminum in different humidity conditions, in which the coefficients of friction (CoFs) and electrical contact resistance (ECR) were continuously monitored. Results show that CoF and ECR data can be linked to the properties of the coatings (thickness, finishing, microstructure, residual stresses, and wettability) and the degradation modes of their tribological and electrical properties. Therefore, electro-tribological data can provide valuable information about the performance of dielectric coatings, the reasons behind it, and assist in the development of the coatings. ECR also shows potential for on-line monitoring of coated parts in operation.Item Enhanced photostability and sensing performance of graphene quantum dots encapsulated in electrospun polyacrylonitrile nanofibrous filtering membranes(2018-06-01) Ruiz, Virginia; Pérez-Marquez, Ana; Maudes, Jon; Grande, Hans-Jürgen; Murillo, Nieves; Tecnalia Research & Innovation; PRINTEXWe report a method to encapsulate graphene quantum dots (GQD) in polyacrylonitrile (PAN) nanofibrous membranes to manufacture robust filtering membranes by electrospinning. GQD-PAN membranes with different nanofiber diameter were prepared tuning the electrospinning parameters, all exhibiting the characteristic fluorescence fingerprint of the GQD probes. The photoluminescence (PL) stability of GQD embedded in the PAN fibers was significantly enhanced with respect to that of water dispersed GQD luminescent probes. The PL of GQD-PAN filtering membranes showed remarkable time stability, both stored dry and immersed in phosphate buffer solutions (PBS), as well as exposed to continuous light irradiation. However, the PL intensity of GQD-PAN membranes was irreversibly quenched by highly oxidant free chlorine solutions. Thus, electrospun GQD-PAN membranes exhibited excellent performance as turn-off fluorescence sensing platforms for free chlorine detection in PBS 0.1 M pH 7. The analytical performance of GQD-PAN membranes was comparable to that of GQD solutions with optimal concentrations, displaying a fast (no need of incubation time) and linear response to chlorine concentration in the 10–600 μM range, a low detection limit of 2 μM, high sensitivity, reproducibility and selectivity. Moreover, the sensing performance of the membranes was very stable after being immersed in PBS for months, outperforming the stability of GQD solutions.Item Evaluation of Anticorrosion Coatings for Offshore Wind Turbine Monopiles for an Optimized and Time-Efficient Coating Application(2022-03-14) Marinova, Nevena; Urbegain, Aiala; Benguria, Pablo; Travé, Andreu; Caracena, Raúl; MATERIALES PARA CONDICIONES EXTREMASOffshore corrosion is a critical issue for metallic offshore structures. In this study, we investigated the corrosion protection of 12 coating systems for offshore monopiles in atmospheric, splash, and submerged zones, and we compared their performance under accelerated laboratory testing according to ISO 12944 with real field exposure. The results showed that the aging of the coatings did not accelerate at the same rate in all coatings. Furthermore, we observed that for some types of laboratory tests, the results are not representative of real field exposure as the laboratory test is much less aggressive than the real offshore conditions. This observation confirms that the field exposure data provide valuable information in order to properly assess the corrosion protection of coatings and thus the expected lifetime of the offshore structure. Additionally, we analyzed the rate-determining steps involved in the application of the coating onto the entire monopile and quantified the possibility of achieving a more time efficient coating process. Our results contribute to a better understanding of the issues related to testing and qualification of corrosion protection coatings for offshore structures and provide useful insights for the selection of coating solutions at the industrial level.
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