•Barrier properties of thin sol-gel coatings were improved with clay nanoparticles.•Self-healing effect was achieved with addition of Ce(III) ions in sol-gel films.•Clay nanoparticles and the cerium ...salt enhance corrosion protection of the mild steel.
The development of a new environment-friendly anticorrosive coating for mild steel substrate is afforded in this work. The combined use of cerium, as a self-healing agent, and clay nanoparticles, as improvers of the barrier properties, was considered to the development of new anticorrosive sol-gel coatings. Nanostructured hybrid films were synthesized by the sol–gel route from tetraethoxysilane (TEOS) and 3-glicidoxipropyl-trimetoxisilano (GPTMS) using laminar nanoclays (Laponite Na+0.7Si8Mg5.5Li0.3H4O24-0.7) to improve mechanical and barrier properties, and Ce(NO3)3•6H2O as a supplier of Ce(III) to provide an inhibiting effect in the event of coating failure. Carbon steel plates, AISI 1010, were used as substrates. Prior to the application of the coating, samples were treated with a phosphoric acid 2% v/v in order to improve coating adherence.
In order to evaluate cerium effect, electrochemical behaviour of films containing Laponite and cerium salts (TGL-Ce) were compared with films containing only Laponite (TGL) by means of potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) measurements using a 0.35wt% NaCl solution. Microstructural characterization and surface analysis of substrates and sol-gel coatings were performed by optical microscopy and by XPS techniques. The use of nanoclays allowed to achieve a significant improvement of the anticorrosive behaviour of the cerium doped coating at the same time that enhances the physical integrity of the coatings under immersion tests.
The use of green-soluble inhibitors in the corrosive medium as alternatives to traditional inhibitors has increased due to the toxicity of the commonly used substances. These novel substances are ...selected owing to their low cost, ease of application as well as maintenance, and low environmental risk. This work aims to evaluate ethanolic-water extracts from post-harvest soybean (Glycine max) by-products as corrosion inhibitors for mild steel in an aggressive medium of sodium chloride. Soybean extracts were obtained by percolation at a controlled flow rate and temperature. To evaluate the anticorrosive efficiency, polarization curves of AISI 1030 steel were carried out at 1 and 7 days of immersion with different concentrations of the soybean extract. Weight loss measurements were carried out alongside potentiodynamic measurements. The steel samples were analyzed by scanning electron microscopy. The soybean extracts obtained reduced the corrosion rate of the steel, showing an efficiency of 30% at day 1. The inhibition efficiency increased up to 80% after 7 days of incubation with 2000 ppm of the extract. A Langmuir adsorption model was fitted to weight loss measurements. K
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and ΔG
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obtained from the model were characteristic of physisorption. The corrosion potential was shifted toward more negative values, classifying the ethanolic-water soybean extract as a cathodic inhibitor. The steel surface for the samples incubated with 2000 ppm of soybean extract was greatly improved showing significantly fewer agglomeration of corrosion products. Soybean leaves are a promising by-product useful to produce ethanolic-water extracts to be used as green corrosion inhibitors.
One strategy for minimising corrosive attack on carbon steel involves the application of hybrid coatings rich in rare earths, on the basis of their low toxicity and environmental sustainability. ...Tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) were each used here as precursors, together with various quantities of colloidal silica suspension, to improve barrier properties of the coatings. Ce(NO3)3·6H2O was added as a source of Ce(III) for further inhibition of corrosion. The corrosion resistance of each kind of sample was evaluated using potentiodynamic polarisation measurements and electrochemical impedance spectroscopy (EIS) in 0.35wt.% NaCl solution. The electrochemical behaviour at various immersion times was modelled by equivalent circuits to demonstrate the effect of silica nanoparticle loading on corrosion. Additional testing was performed under harsh conditions of salt spray chamber. The microstructure and composition of sol–gel coatings were characterised by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS), focused-ion beam SEM/EDS analysis, X-ray photoelectron spectroscopy and confocal microscopy.
•Hybrid coatings containing silica nanoparticles and cerium ions were applied on carbon steel.•At higher content of nanoparticles, both thickness and barrier effect enhance.•Bi layer coatings with silica nanoparticles and cerium ions offer the best combination for protection.
This work studies the synthesis and characterization of hybrid organic–inorganic coatings based on silica to improve the corrosion resistance of carbon steel. Hybrid organic–inorganic silica sol–gel ...coatings were obtained by dipping in an organically modified silica sol synthesized through hydrolysis and condensation of 3-glicidoxipropyl-trimetoxisilano (GPTMS) and tetraethoxysilane (TEOS) in acidic catalysis. The coatings were doped with a cerium salt (Ce(NO3)3·6H2O) and loaded with silica nanoparticles in order to improve both barrier effect and the anticorrosive behavior of the coatings by the inhibitory effect of cerium. Prior to the application of the coating, some samples were treated with a phosphoric acid 2% v/v in order to improve coating adherence. A two layered coating was applied onto AISI 1010 carbon steel, the outer containing with a cerium salt and the inner one with silica nanoparticles without the cerium salt, producing homogeneous and cracks-free films. Raman spectroscopy was used to characterize the compounds present in the surface of steel after pretreatment with phosphoric acid. Microstructural characterization of coatings was performed by means of scanning electron microscopy (SEM).
The evolution with time of the protective properties of films was studied by electrochemical impedance spectroscopy (EIS), providing quantitative information of the role of the pre-treatment. Electrochemical behavior in each stage of the corrosion processes was modeled by equivalent circuits. Additionally, films adhesion was evaluated by nano-scratch demonstrating that the phosphate treatment improves adhesion of the hybrid coating.
► Continuous coatings were obtained onto carbon steel by sol gel using TEOS and GPTMS. ► Corrosion resistance is improved by applying the phosphoric acid prior to coating. ► Coating adhesion is enhanced when phosphoric treatment is performed.
Degradation of carbon steel has always been a concern. The use of coatings is especially recommended in aggressive atmospheres at moderate temperatures. Ceramic films can be used to improve the ...resistance against high temperature oxidation and corrosion of metals. Amid the different options, a sol-gel process provides a low cost, simple and non-hazardous method for processing ceramic coating with controllable composition and microstructure.
This work evaluates the electrochemical behaviour of carbon steel coated by sol-gel method. Hybrid organic–inorganic silica sol-gel coatings were obtained by dip coating of planar samples in an organically modified silica sol made from hydrolysis and polycondensation of tetra-orthosilicate (TEOS) and methyltriethoxisilane (MTES) by acidic catalysis. Coatings free of defects were obtained at a sintering temperature of 400 °C. The coated samples were inspected by optical and electron microscopy and coating thickness was measured by using a Talystep surface roughness tester. Electrochemical evaluation was made by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. A comparison of the corrosion resistance of the coated metal with the uncoated one is presented. The measurements show the improvement of the corrosion resistance of the coated carbon steel.
Sol–gel organic–inorganic hybrid coatings are being increasingly used to protect metal surfaces. The presence of non-hydrolysable groups in their structure can lead to the formation of coatings with ...properties intermediate between glasses and organic polymers. Crack-free, homogeneous and adherent hybrid silica sol–gel coatings around 1 μm thick were obtained by dip-coating on glass and Austempered Ductile Iron (ADI). Homogeneous multilayer coatings up to 4 μm were obtained on glass substrates, but not on ADI substrates since coating cracked after the densification of a second layer. The hardness of the coating on ADI substrates was slightly higher than that of as received ADI. Preliminary electrochemical impedance polarization spectroscopy (EIS), potentiodynamic polarization and polarization resistance tests in NaCl solution have shown an improvement of corrosion resistance of ADI.
Owing to increasing interest of coatings applied on low alloy steel and galvanised metal plates and their applications, this work presents the study of the process requirements to be fulfilled in ...order to coat these metals with an hybrid silica coatings containing Zn particles. The main idea was to combine the “barrier” effect of the hybrid silica coatings with the “active protection” effect of the zinc particles inside the coatings. Sol–gel parameters, Zn particles content and suspension stability have been studied. EMPHOS ES 21, an electrostatic dispersant, has been used to obtain stabilised suspensions. Thick, adherent and crack-free coatings containing 10% Zn particles were prepared by dip-coating on carbon steel and Al/Zn coated carbon steel substrates. The applied coating seems to improve corrosion protection of the two metal substrates, and this effect is more noticeable in the case of the Al/Zn system because of the combination of the complementary corrosion protection properties of both coatings.
We report the discovery of two intermediate-mass transiting brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of P ...= 6.55604 0.00016 days, a mass of Mb = 64.1 1.9 , and a radius of Rb = 0.75 0.02 . Its host star, TOI-569, has a mass of M = 1.21 0.05 , a radius of R = 1.47 0.03 , dex, and an effective temperature of Teff = 5768 110 K. TOI-1406b has an orbital period of P = 10.57415 0.00063 days, a mass of Mb = 46.0 2.7 , and a radius of Rb = 0.86 0.03 . The host star for this BD has a mass of M = 1.18 0.09 , a radius of R = 1.35 0.03 , dex, and an effective temperature of Teff = 6290 100 K. Both BDs are in circular orbits around their host stars and are older than 3 Gyr based on stellar isochrone models of the stars. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of 40-50 and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b). Both BDs have reliable ages from stellar isochrones, in addition to their well-constrained masses and radii, making them particularly valuable as tests for substellar isochrones in the BD mass-radius diagram.
Due to the rapid emergence of antibiotic-resistant bacteria, there is a growing need to discover new antibiotics. To address this challenge, we trained a deep neural network capable of predicting ...molecules with antibacterial activity. We performed predictions on multiple chemical libraries and discovered a molecule from the Drug Repurposing Hub—halicin—that is structurally divergent from conventional antibiotics and displays bactericidal activity against a wide phylogenetic spectrum of pathogens including Mycobacterium tuberculosis and carbapenem-resistant Enterobacteriaceae. Halicin also effectively treated Clostridioides difficile and pan-resistant Acinetobacter baumannii infections in murine models. Additionally, from a discrete set of 23 empirically tested predictions from >107 million molecules curated from the ZINC15 database, our model identified eight antibacterial compounds that are structurally distant from known antibiotics. This work highlights the utility of deep learning approaches to expand our antibiotic arsenal through the discovery of structurally distinct antibacterial molecules.
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•A deep learning model is trained to predict antibiotics based on structure•Halicin is predicted as an antibacterial molecule from the Drug Repurposing Hub•Halicin shows broad-spectrum antibiotic activities in mice•More antibiotics with distinct structures are predicted from the ZINC15 database
A trained deep neural network predicts antibiotic activity in molecules that are structurally different from known antibiotics, among which Halicin exhibits efficacy against broad-spectrum bacterial infections in mice.
We report on the confirmation of a transiting giant planet around the relatively hot (Teff = 6801 ± 76 K) star HD 2685, whose transit signal was detected in Sector 1 data of NASA’s TESS mission. We ...confirmed the planetary nature of the transit signal using Doppler velocimetric measurements with CHIRON, CORALIE, and FEROS, as well as using photometric data obtained with the Chilean-Hungarian Automated Telescope and the Las Cumbres Observatory. From the joint analysis of photometry and radial velocities, we derived the following parameters for HD 2685 b: P = 4.12688 −0.00004+0.00005 $^{+0.00005}_{-0.00004}$ −0.00004+0.00005 days, e = 0.091 −0.047+0.039 $^{+0.039}_{-0.047}$−0.047+0.039 , MP = 1.17 ± 0.12 MJ, and RP =1.44 ± 0.05 RJ. This system is a typical example of an inflated transiting hot Jupiter in a low-eccentricity orbit. Based on the apparent visual magnitude (V = 9.6 mag) of the host star, this is one of the brightest known stars hosting a transiting hot Jupiter, and it is a good example of the upcoming systems that will be detected by TESS during the two-year primary mission. This is also an excellent target for future ground- and space-based atmospheric characterization as well as a good candidate for measuring the projected spin-orbit misalignment angle through the Rossiter–McLaughlin effect.
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