Bi-layered silane-TiO2/collagen coating to control biodegradation and biointegration of Mg alloys

International audienceMagnesium alloys have shown high potential as biodegradable implants for bone repair applications. However, their fast degradation in physiological media demands tuning their corrosion rate to accompany the natural tissue healing processes. Here, a new bi-layered silane-TiO2/collagen coating efficient in stabilizing and biofunctionalizing the surface of AZ31 and ZE41 Mg alloys is presented. Corrosion tests performed in cell culture medium over 7 weeks showed that the bi-layered coating promotes the formation of a stable layer of Mg(OH)2/MgCO3/CaCO3 that provides effective protection to the alloys at advanced immersion stages. The intrinsic reactivity of each alloy plus formation of transitory calcium phosphate phases, resulted in distinct corrosion behavior in the short term. Cell experiments showed that the bi-layered coating improved osteoblasts and fibroblasts proliferation compared to bare and silane-TiO2-coated alloys. Different responses in terms of cell adhesion could be related to the intrinsic corrosion rate of each alloy and some toxicity from the alloying elements. The results evidenced the complex interplay between alloy nature, coating-alloy combination and cell type. The silane-TiO2/collagen coating showed to be a promising strategy to improve cell response and viability and to control degradation rate of Mg alloys in the long term

Tackling perception and deception in STEM: A critical thinking skill for early-career development

The Universitat Politècnica de Catalunya (UPC), the Instituto Superior Técnico (ISTUniversidade de Lisboa) and the Czech Technical University (CTU) have recently launched the Engine4STEMers project, a joint initiative whose objective, among others, is to guide young graduates in their transition to the job market and motivate them to adopt management and leadership skills early in their careers. In this context, this short paper describes the objectives and contents of a Critical Thinking seminar, currently underway at UPC, which is aimed at motivating young STEM Graduates to develop the principles of a skeptical attitude towards the information and stimuli that we perceive in order to face uncertainty, biased information and hidden agendas. Engine4STEMers needs analysis has revealed the importance of a good understanding of the concepts of perception and deception to develop effective interpersonal skills and, more importantly, to ease decision-making processes in a VUCA (volatile, uncertain, complex and ambiguous) environment.Peer ReviewedObjectius de Desenvolupament Sostenible::4 - Educació de QualitatObjectius de Desenvolupament Sostenible::4 - Educació de Qualitat::4.4 - Per a 2030, augmentar substancialment el nombre de joves i persones adultes que tenen les competències necessàries, en particular tècniques i professionals, per a accedir a l’ocupació, el treball digne i l’emprenedoriaPostprint (published version

Activated Carbons From Winemaking Biowastes for Electrochemical Double-Layer Capacitors

Revalorizing organic biowaste is critical to achieve a full circular economy, where waste is transformed into resources. One of the main strategies is to produce activated carbons and use them as functional materials for electrochemical energy storage. In this study, winemaking wastes, bagasse (BAG), and cluster stalks (CS) were recovered and used in the preparation of activated carbons by a hydrothermal process. Then, they were chemically activated using KOH and investigated for electrochemical capacitor applications. The activation treatment resulted in microporous structures, characterized by a type I isotherm for low partial pressures (P/P), and a type IV for higher pressures, as observed by Brunauer–Emmett–Teller surface analysis, with specific surfaces of 1,861 and 2,662 m·g for BAG and CS, respectively. These microporous structures were also investigated by means of scanning electron microscopy, revealing a high porous degree. Micro-Raman spectroscopy and X-ray photoelectron spectroscopy measurements displayed bands associated to disorder of the structure of the carbonaceous material. The electrochemical performance of the resulting materials was investigated for electrochemical energy storage applications, as supercapacitor electrode, in 1 M KOH aqueous electrolyte. These biowaste-derived materials displayed electrochemical double-layer capacitance, with 129 F·g at 10 A·g in the 0.1 to −1.0 V vs. saturated calomel electrode. For that reason, they are pin-pointed as potential negative electrodes for electrochemical double-layer supercapacitors and hybrid or asymmetric supercapacitors.Authors from Centro de Química Estrutural would like to thank the financial support of Fundação para a Ciência e a Tecnologia (FCT) under project numbers 1801P.00824.1.01, UID/QUI/00100/2019, and UIDB/00100/2020. We acknowledge support for the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)

Tannic Acid-Loaded Hydroxyapatite Carriers for Corrosion Protection of Polyolefin-Coated Carbon Steel

In this study, pH-sensitive hydroxyapatite particles loaded with tannic acid were incorporated in polyolefin-based coatings for the corrosion protection of carbon steel. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were used to characterize the hydroxyapatite particles loaded with tannic acid (Tannic-HAP). Electrochemical impedance spectroscopy (EIS) was employed to study the protective performance of the reference and modified polyolefin coatings. The results suggest that modified coatings showed improved corrosion performance compared to the unmodified coatings. The combination of tannic acid and hydroxyapatite contributed to a more effective protection of coated carbon steel

Electrochemical performance of MnOx·center dot nH(2)O@Ni composite foam electrodes for energy storage in KOH media

Nanostructured porous MnO2, especially its hydrated amorphous and low crystalline form (MnO2·nH2O), has been one of the most promising material considered for charge storage applications, due to electrochemical similarities with RuO2 and its relative low cost. However, the intrinsic poor conductivity of MnO2 combined with the presence of structural water, which provides high ionic but low electronic conductivity, is a great hindrance for wider application. An effective approach to overcome this drawback involves the deposition of thin MnO2 layers on porous, high surface area metallic scaffolds. The present work addresses this route and provides novel insights thanks to the combination of MnOx·nH2O with custom-made Ni foams, fabricated via one-step electrodeposition using the dynamic hydrogen bubble template (DHBT). The porous Ni foams provide a scaffold with a 3D architecture with optimized pore size and surface. The composite electrode was fabricated by anodic deposition of MnOx·nH2O on the 3D Ni foams. The electrochemical behaviour was tested in 1 M KOH, since there are very few studies addressing the electrochemical behaviour of MnOx·nH2O in alkaline media for electrochemical supercapacitors applications. In addition, thermal treatment (150–250 °C) was performed to evaluate the effect of hydration on the material properties. The results revealed that the as-obtained composites are highly stable, displaying much higher specific capacitances with 73–90% (depending on the mass load) capacitance retention compared to their de-hydrated counterparts. The charge-discharge processes were found to be highly reversible throughout 5000 cycles, maintaining almost 100% columbic efficiency. In conclusion, the MnOx·nH2O@Ni composite electrodes showed a very stable pseudocapacitive behaviour and exceptional cycling performance in 1 M KOH, being therefore a promising alternative charge storage electrode for electrochemical supercapacitors.info:eu-repo/semantics/publishedVersio

Tannic Acid-Loaded Hydroxyapatite Carriers for Corrosion Protection of Polyolefin-Coated Carbon Steel

In this study, pH-sensitive hydroxyapatite particles loaded with tannic acid were incorporated in polyolefin-based coatings for the corrosion protection of carbon steel. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were used to characterize the hydroxyapatite particles loaded with tannic acid (Tannic-HAP). Electrochemical impedance spectroscopy (EIS) was employed to study the protective performance of the reference and modified polyolefin coatings. The results suggest that modified coatings showed improved corrosion performance compared to the unmodified coatings. The combination of tannic acid and hydroxyapatite contributed to a more effective protection of coated carbon steel.This publication was made possible by NPRP13S-0120-200116 from the Qatar National Research Fund (a member of the Qatar Foundation). The authors from Centro de Química Estrutural acknowledge the financial support of Fundação para a Ciência e Tecnologia (UIDB/00100/2021, LA/P/0056/2020, and UIDP/00100/2021). Statements made herein are solely the responsibility of the authors. The authors acknowledge Dow Chemical Company (Bernhard Kainz, Global Application Development Leader Metal Packaging Coatings, Dow Coating Materials) for providing polyolefin CANVERA 1110 coating formulation; Voestalpine AG for providing carbon steel; Marta Alves (Instituto Superior Técnico) for conducting the XRD tests; Mário Vale (Instituto Superior Técnico) for performing TG/DTG studies.Scopu

Highly ordered mesoporous silica and halloysite nanotubes loaded with diethylenetriamine DETA for smart anti corrosion coatings

The development of nanoscience and technology has devoted significant attention to conducting studies on hollow particles. Among the available materials, mesoporous silica nanoparticles have recently gained attention as potential nanocontainers due to their high stability, large surface area, controllable pore diameter and easy surface functionalization as they can store and release organic or inorganic molecules of different sizes and functionalities. The aim of this work is to study the use of mesoporous silica as a potential reservoir for corrosion inhibitor for active corrosion protection of carbon steel and using epoxy encapsulated halloysite nanotubes for the self healing process of the epoxy based coatings. The synthesized mesoporous silica particles were characterized by using XRD, FTIR and SEM. Mesoporous silica particles loaded with diethylenetriamine (DETA) were embedded into the epoxy polymer along with the halloysite nanotubes (HNTs) encapsulated with epoxy monomer and amine immobilized in mesoporous silica with a weight ratio of 5 wt% of mesoporous silica. Kinetics of release of corrosion inhibitor was evaluated by electrochemical impedance (EIS) measurements in 3.5 wt% NaCl solution. The EIS analysis confirms that the release of inhibitor during the corrosion process has significantly improved the anticorrosion properties when compared to the epoxy coated sample without any corrosion inhibitor. The self healing phenomenon in the scratched epoxy coated sample was monitored by SEM during different time intervals. The SEM results showed that that the epoxy pre-polymer was slowly released into the crack.Upon release, the epoxy pre-polymer came into contact with the amine immobilized in mesoporous silica and cross-linked to heal the scratch over the sample surface. This study suggests that these novel coatings may have some potential applications in the oil and gas industry.qscienc

Pseudocapacitive response of hydrothermally grown MoS2 crumpled nanosheet on carbon fiber

Crumpled MoS2 nanosheets were synthesized directly on carbon fiber paper (CFP) through hydrothermal procedure. Molybdenum sulfide precursor was first produced in the solution and then introduced into the autoclave. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed the uniform growth of crumpled nanosheets on the CFP that were assigned to MoS2 according to X-ray photo electron spectroscopy (XPS) and Raman spectroscopy results. Electrochemical measurements of the as deposited MoS2 crumpled nanosheets performed in 1 M Na2SO4 evidenced a specific capacitance of 249 F g−1 at 2 A g−1 and the good rate capability by retaining 41.3% of initial capacitance at 10 A g−1. Electrochemical Impedance spectroscopy measurements showed very low charge transfer resistance and very short relaxation time accounting for the pseudocapacitive rectangular cyclic voltammetry (CV) and high rate capability.info:eu-repo/semantics/acceptedVersio

Hybrid microcapsules reinforced smart coatings for corrosion protection in oil and gas industry

Corrosion is one of the critical causes of material loss in metal components. This research is focused on the synthesis, and electrochemical properties of polyelectrolyte layered microcapsules (PMCs) reinforced smart polymeric coating for corrosion protection of steel substrates. For this purpose, monolayer urea-formaldehyde microcapsules encapsulated with linalyl acetate (MLMCs) was synthesized by Insitu polymerization. In the next step, phenylthiourea (PTU) was loaded between the layers of polyelectrolytes; polyethylenimine (PEI) & sulfonated polyether ether ketone (SPEEK) on the surface of MLMCs using layer by layer technique. The MLMCs are sensitive to mechanical stress while the PTU in PMCs is triggered by pH stimulus. The newly designed PMCs has linalyl acetate in the core and PTU in the polyelectrolyte layers. Furthermore, 6 wt.% of both MLMCs and PMCs are dispersed in the epoxy resin and applied on the clean steel substrate. Performance comparison showed that the epoxy resin reinforced with PMCs demonstrate enhanced thermal, self-healing and electrochemical properties. This improved performance can be attributed to the efficient release of the self-healing agent and corrosion inhibitor from the PMCs. Conclusively, the epoxy coatings modified with PMCs can be a novel organic coating for the corrosion protection of oil and gas industries