Uniform Protective Layer Research Articles

Regulating the Helmholtz plane by trace ionic liquid additive for advanced Al-air battery

Al-air batteries (AABs) are the next generation of alternative energy sources due to their high theoretical energy density, low cost, and environmental friendliness. Researchers have been interested in AABs with stable discharge in alkaline solution, long discharge time, and high conductivity. However, the uncontrolled self-corrosion of the Al anode and the severe hydrogen evolution reaction in alkaline electrolytes have been two major drawbacks hindering the commercial development of AABs. These shortcomings reduce the Al anode's utilization and significantly shorten the battery's service life. Herein, the Helmholtz plane structure was reconstructed using an ionic liquid additive called 1-aminopropyl-3-methylimidazolium bromide (AMIB) to regulate the electrochemical interface between the electrolyte and the Al anode. Electrochemical tests found that when 3 mM AMIB was added, the corrosion inhibition efficiency could reach up to 60 %. Further surface analysis and theoretical calculations showed that AMIB can form a dense and uniform protective layer on the surface of the Al anode substrate, which reduces the anode corrosion, lowers the active centers for hydrogen evolution on the Al surface, and reduces the hydrogen evolution rate. The full-cell studies found that the specific capacity of the cell increased from 1227 to 2564 mAh g−1, the energy density increased from 1546 to 3359 Wh kg−1, and the Al anode utilization increased from 41.2 % to 86.1 % as the AMIB addition to the alkaline electrolyte risen from 0 to 3 mM. This method of electrolyte regulation provides an efficient strategy for the commercial development of AABs.

Extraordinary Corrosion Inhibition of Potassium Stannate and Riboflavin Hybrid Additive on the Al Alloy Anode of Alkaline Al‐Air Batteries

AbstractAl‐air batteries (AABs) are regarded as a promising future alternative energy source due to their supposedly high energy density. The corrosion of AABs resulting from the hydrogen evolution corrosion and self‐corrosion occurring during their use in alkaline solutions represented a significant obstacle to their development, considerably limiting their commercialization. In this study, we examined the corrosion inhibition efficiency of the hybrid anticorrosive agent composed of potassium stannate (K2SO3) and riboflavin (Rib) when used as an addition in the electrolyte of an alkaline AAB. The experimental results demonstrated that the incorporation of the hybrid corrosion inhibitor leads to an anticorrosion inhibition efficiency of 70.2%, an increase in the discharge specific capacity, and specific energy of the entire battery from 913 mAh g−1 and 1023 Wh kg−1 to 2128 mAh g−1 and 2511 Wh kg−1, respectively. The adsorption behavior of the additives on the surface of the Al alloy was studied using surface characterization techniques such as scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS). It revealed that the incorporation of the hybrid additive leads to the formation of a dense and uniform protective layer on the surface of the Al anode during the discharge process. This film effectively prevents direct contact between the alkaline electrolyte and the Al surface, drastically reducing the formation of possible hydrogen interactions between the electrolyte and the anode. Consequently, the hydrogen evolution reaction (HER) is efficiently inhibited, and the overall performance of the AAB is improved. Thus, this electrolyte regulation strategy presents a novel approach to studying high‐efficiency alkaline AABs.

Synthesis of a novel Si-N-S flame retardant and its application on cotton cellulose biomacromolecule

A novel flame retardant containing Si, N, and S elements, ((2-(triethoxysilyl)ethyl)thio)ethan-1-amine hydrochloride (TETEA), was synthesized via a click reaction and characterized using nuclear magnetic resonance spectroscopy (NMR) and fourier transform infrared spectroscopy (FTIR). Subsequently, the flame-retardant cotton fabric was fabricated by sol-gel method. The results indicated that TETEA was successfully loaded on cotton fabric and formed a uniform protective layer on the surface of cotton fabric, exhibiting excellent flame retardancy. The flame-retardant cotton fabric achieved limiting oxygen index (LOI) of 28.3 % and passed vertical combustion test without after-flame or afterglow time at TETEA concentration of 500 g/L. Thermogravimetric analysis revealed that the residual carbon content of the flame-retardant cotton fabric was much higher than that of the control under air and N2 conditions. Besides, the flame-retardant cotton fabric was not ignited in cone calorimeter test with an external heat flux of 35 kW/m2. The peak heat release rate and the total heat release decreased from 133.4 kW/m2 to 25.8 kW/m2 and from 26.46 MJ/m2 to 17.96 MJ/m2, respectively. This phosphorus-free flame retardant offers a simplified synthesis process without adverse environmental impacts, opening up a new avenue for the development environmentally friendly flame retardants compared to traditional alternatives.

Facile Fabrication of Highly Efficient Chitosan-Based Multifunctional Coating for Cotton Fabrics with Excellent Flame-Retardant and Antibacterial Properties.

Interest in the development of eco-friendly, sustainable, and convenient bio-based coatings to enhance flame retardancy and antibacterial properties in cotton fabrics is growing. In this work, chitosan was protonated at its amino groups using a method with a high atom economy using an equimolar amount of amino trimethylene phosphonic acid (ATMP), resulting in the fabrication of a single-component chitosan-based multifunctional coating (ATMP-CS), thereby avoiding any additional neutralization or purification steps. Cotton fabrics coated with various loads of ATMP-CS were prepared through a padding-drying-curing process. The morphology, thermal stability, mechanical properties, antibacterial properties, flame-retardant behavior, and flame-retardant mechanism of these fabrics were investigated. The coating exhibited excellent film-forming properties, and it imparted a uniform protective layer onto the surfaces of the cotton fabrics. When the load capacity reached 11.5%, the coated fabrics achieved a limiting oxygen index of 29.7% and successfully passed the VFT test. Moreover, the ATMP-CS coating demonstrated antibacterial rates against Escherichia coli and Staphylococcus aureus reaching 95.1% and 99.9%, respectively. This work presents a straightforward and gentle approach to fabricating colorless, environmentally friendly, and highly efficient fabric coatings that have potential applications in promoting the use of bio-based materials.

Optimization of anodizing conditions and hole sealing treatments for enhanced anti-corrosion properties of magnesium alloys

To enhance the corrosion resistance of magnesium alloys, an anti-corrosion composite film was prepared by combining anodic oxidation and sol-gel technology. Experimental results indicate that after anodization at 17.5V for 3 min, the composite film obtained through sealing with an MPTMS-modified sol exhibited significant improvements in physical properties. The thickness of the film reached 24.3 μm, its hardness was measured at 164.7 HV, and it demonstrated good surface uniformity. Electrochemical impedance spectroscopy revealed that the impedance modulus at low frequency (|Z| at 0.01 Hz) increased by nearly two orders of magnitude. Furthermore, this study thoroughly explores the corrosion protection mechanism of the composite film, highlighting the role of the sol-gel layer in occupying micro-pores and micro-cracks to form a denser and more uniform protective layer. The dual-layer protection provided by the combination of anodic oxidation and sol-gel layers significantly enhances the overall corrosion resistance of the magnesium alloy.

Guiding Zn Uniform Deposition with Polymer Additives for Long-lasting and Highly Utilized Zn Metal Anodes.

The parasitic side reaction on Zn anode is the key issue which hinders the development of aqueous Zn-based energy storage systems on power-grid applications. Here, a polymer additive (PMCNA) engineered by copolymerizing 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-acryloyl glycinamide (NAGA) was employed to regulate the Zn deposition environment for satisfying side reaction inhibition performance during long-term cycling with high Zn utilization. The PMCNA can preferentially adsorb on Zn metal surface to form a uniform protective layer for effective water molecule repelling and side reaction resistance. In addition, the PMCNA can guide Zn nucleation and deposition along 002 plane for further side reaction and dendrite suppression. Consequently, the PMCNA additive can enable the Zn//Zn battery with an ultrahigh depth of discharge (DOD) of 90.0% for over 420 h, the Zn//active carbon (AC) capacitor with long cycling lifespan, and the Zn//PANI battery with Zn utilization of 51.3% at low N/P ratio of 2.6.

Guiding Zn Uniform Deposition with Polymer Additives for Long‐lasting and Highly Utilized Zn Metal Anodes

AbstractThe parasitic side reaction on Zn anode is the key issue which hinders the development of aqueous Zn‐based energy storage systems on power‐grid applications. Here, a polymer additive (PMCNA) engineered by copolymerizing 2‐methacryloyloxyethyl phosphorylcholine (MPC) and N‐acryloyl glycinamide (NAGA) was employed to regulate the Zn deposition environment for satisfying side reaction inhibition performance during long‐term cycling with high Zn utilization. The PMCNA can preferentially adsorb on Zn metal surface to form a uniform protective layer for effective water molecule repelling and side reaction resistance. In addition, the PMCNA can guide Zn nucleation and deposition along 002 plane for further side reaction and dendrite suppression. Consequently, the PMCNA additive can enable the Zn//Zn battery with an ultrahigh depth of discharge (DOD) of 90.0 % for over 420 h, the Zn//active carbon (AC) capacitor with long cycling lifespan, and the Zn//PANI battery with Zn utilization of 51.3 % at low N/P ratio of 2.6.

Role of SnO2 Nanoparticles for a Self-Forming Barrier Layer on a Mild Steel Surface in Hydrochloric Acid Medium Containing Piper betle Leaf Extract.

The self-formation of a porous organic thin-film via corrosion inhibitor supports wide applications of carbon steel in industry. Unfortunately, serious damages could be concentrated to the pinhole and/or pore locations in the porous organic film, resulting in the localized corrosion even when an optimal concentration of organic corrosion inhibitors is used. In this work, SnO2 nanoparticles are used for producing the more robust barrier layer via the self-migration of nanoparticles, resulting in a higher corrosion resistance, smooth and uniform protective layer, as well as the existence of SnO2 in the protective layer that could directly affect the high inhibition performance. Therefore, the work suggests a new way to make a more robust thin film that could extend the use of organic corrosion inhibitors.

An integrated surface coating strategy to enhance the electrochemical performance of nickel-rich layered cathodes

High-nickel layered oxides, LiNixCoyMnzO2 (0.6 ≤ x < 1), are promising cathode materials for producing batteries with high energy density and working voltage, while their poor cycling performance severely limits their commercial applications. Herein, an integrated surface coating/doping strategy is developed to significantly improve the structural stability and electrochemical performance of LiNi0.88Co0.06Mn0.06O2. The titanium ions from a thin TiNb2O7 coating layer diffuse inward during the high-temperature sintering process and a uniform protective layer forms on the surface of the secondary particles of the material. This protective layer suppresses side reactions, and the Ti4+ doping increases the thickness of the lithium layer and reduces the lithium/nickel mixing, thereby enhancing the diffusion of lithium ions in bulk electrode. The capacity retention of modified material after 200 cycles at 1 C is greatly improved from 59.8% of the pristine material to 87.2%. First-principles calculations confirm the interaction affinity of the TiNb2O7 coating on the layered LiNi0.88Co0.06Mn0.06O2 with Ti ion migration in the interlayer region. Moreover, the enhanced oxygen release energy and electronic conductivity benefiting from Ti4+ doping promote the cycling stability of the integrated cathode. The surface engineering strategy proposed herein is generally effective for the electrochemical improvement of nickel-rich ternary cathode materials.

Evaluación electroquímica de la degradación de la aleación de Mg-Zn-Ca en la solución fisiológica de Hanks

En el presente trabajo se ha investigado el efecto de los elementos aleantes Zn (0,95% en masa) y Ca (0,15% en masa) en el mecanismo de degradación del Mg. Las superficies del Mg puro y de la aleación Mg-Zn-Ca han sido caracterizadas durante su exposición a la solución fisiológica de Hanks (a 37 °C) hasta siete días, utilizando las técnicas SEM-EDS y XPS. La capa formada en la superficie de la aleación contiene Ca10(PO4)6(OH)2, que puede mejorar la compatibilidad ósea. Las partículas intermetálicas compuestas de la fase Mg2Ca, así como la presencia de Zn, han promovido la formación de una capa protectora más uniforme. Las pruebas de EIS y ruido electroquímico (EN) han indicado que la resistencia a la polarización (Rp) del Mg puro es un orden de magnitud menor y la resistencia al ruido de la corriente (Rn) ≈ 5 veces menor, que los de la aleación de Mg-Zn-Ca. Los valores del índice de picadura (PI) de cada material fueron inferiores a 0,6; lo que sugiere que el ataque de corrosión no está altamente localizado. Al final de las pruebas de inmersión, la concentración de iones de Mg liberados durante la degradación ha sido ≈ 4,5 veces mayor para Mg puro (1,63 ± 0,02 mg·cm−2) que para Mg-Zn-Ca (0,35 ± 0,03 mg·cm−2). En consecuencia, la densidad de corriente de corrosión (jcorr) calculada para el Mg puro fue dos veces mayor (1,33 μA·cm−2) que la de la aleación de Mg ZX10 (0,59 μA·cm−2).

Fabrication of a novel hydrophobic anti-corrosion film based on Eu2O3/stearic acid on steel surface; Experimental and detailed computer modeling studies

Metal's corrosion is an important parameter affecting the steel lifetime. Nowadays, because of the widespread industrial applications of mild steel, the corrosion protection of this material has become a challenging item. The modification of the metal surface (i.e., mild steel, MS) via thin hydrophobic layers is one of the most efficient/promising protocols for the improvement of the metal's anti-corrosion properties.In this work, the MS sample surface was treated by a novel thin-film based on the europium (Eu) oxide. Using stearic acid (STA) and palmitic acid (PAA) molecules, a hydrophobic layer was constructed on the Eu-treated sample. The EDS and GIXRD tests were utilized for the analysis of the elemental/phase compositions of the treated and untreated samples. The FE-SEM and AFM tests were used for studying the surface morphology and topography of the treated and untreated samples. The corrosion protection durability of the coated metals was checked via electrochemical approaches, i.e., EIS and potentiodynamic polarization. The EDS/Mapping analysis demonstrated that the europium conversion coating (EuCC) was successfully deposited on the MS surface. Besides, a high concentration of the Eu-containing compounds in the GIXRD patterns proved the sufficient Eu-based conversion coating formation on the sample. The contact angle (CA) measurements displayed that after surface modification with the hydrophobic layer, the CA was drastically improved by about 40%. The FE-SEM micrographs ensured the precipitation of a uniform protective layer without obvious cracks on the MS surface. The Tafel curves illustrated that the EuCC-STA could diminish the steel corrosion by mixed anodic and cathodic inhibition mechanisms. The EIS reports evidence that the existence of the EuCC-STA hydrophobic film could diminish about 66% of corrosion activities during 24 h of iron exposure to the harsh 3.5% chloride media.

Scaffold-structured polymer binders for long-term cycle performance of stabilized lithium-powder electrodes

ABSTRACT Effects of soluble polyimide (PI) binders on large-sized Li anodes (width = 21.5 cm; thickness = 40 μm) prepared using Li-metal powder (LiMP) have been investigated. PI binders form a uniform protective layer on exposed Li-powder-coated surfaces, thereby resulting in formation of scaffold-structured LiMP-based anodes. Uniform PI surface films favor realization of Li plating on Li-metal surfaces by forming a smooth surface structure, and the three-dimensional insulating PI matrix functions as a buffer layer that absorbs volume change. Moreover, PI binders facilitate enhanced cohesion between LiMP particles. The above-described triple action of PI binders significantly reduces Li dendrites. Consequently, PI-containing LiMP-based metal anodes demonstrate enhanced electrochemical performance compared to both polymeric binders and bare Li-metal foils. Results obtained in this study reveal that LiMP-based anodes containing PI binders exhibit 89% (98.2 mAh g–1) discharge-capacity retention during the 200th cycle, whereas bare Li-metal foil demonstrates sudden degeneration during the 65th cycle. Furthermore, PI containing LiMP-based anodes exhibit improved rate capability compared to other polymeric binders considered in this study.

Electrostatic spraying of chitosan coating with different deacetylation degree for strawberry preservation

This study used electrostatic spraying (ES) system as an efficient technique for strawberry preservation with chitosan (CH) coating. The effects of CH deacetylation degree (DD, 81.0, 88.1 and 95.2%) on the qualities (weight loss, pH, total soluble solids (TSS), firmness, flavonoids content, malondialdehyde (MDA) content and superoxide dismutase (SOD) activity and mold growth) of strawberry during cold storage were investigated. Results showed that CH coating by ES formed more continuous and uniform protective layer compared with conventional spraying (CS). CH coating effectively enhanced the overall quality and extended shelf life of strawberry at least 2 days. CH coating with 81.0% and 88.1% DD were more effective in reducing weight loss of strawberry, and CH coating with 88.1% DD could better maintain TSS content, while CH coating with 95.2% DD delayed the decline in flavonoids more obviously. However, DD had no significant impact on pH, firmness, SOD activity, MDA and mold growth of coated samples. The evaluation criteria indicated CH coating with 88.1% DD had better preservation performance with the highest synthetic value (6.17) during storage. These findings suggest that CH coating especially with 88.1% DD by ES, as a safe, cheap and efficient technique, has great potential for industrial application of fruit preservation.

Corrosion inhibition of iron surfaces with phosphatidic acid

Abstract Preventing the corrosion of iron in inaccessible structures requires a coating method that reaches all surface areas and creates a uniform protective layer. An ages old practice to protect iron artefacts is to coat them with animal fat, that is, a mixture of lipids. This “method” is accidentally ingenious: some natural phospholipids found in animal fat have the potential to form a tightly packed self-assembled monolayer on metal oxide surfaces, similar to the surfactant monolayers that have attracted increasing attention lately. Thus, the most primitive corrosion prevention method may point at a way to coat complex iron structures in an industrial environment. Here the ability of phosphatidic acid, a natural lipid, to coat and protect iron surfaces was examined. Iron coated quartz crystal microbalance (QCM) sensors were used for the experiments, to monitor the deposition of the lipid as well as the acidic corrosion (dissolution) of iron in situ, in real time. The sensors were coated by self-assembled monolayers of di-myristoyl phosphatidic acid using the liposome deposition method. In this process, 50-100 nm vesicles formed by the lipid are delivered in an aqueous solution and spontaneously coat the iron surfaces upon contact. QCM and ellipsometry measurements confirmed that continuous bilayer and monolayer surface coatings can be achieved by this method. QCM measurements also confirmed that the layers were corrosion resistant in 0.01M acetic acid solution that would dissolve the thin iron layer in minutes in the absence of the protective coating. XPS results suggested a chemisorption-based mechanism of phosphatidic acid attachment to the iron surface. Hence, liposome deposition of phosphatidic acid offers a suitable solution to coat iron surfaces in inaccessible structures in situ.

Corrosion of 85-5-5-5 bronze in natural and synthetic acid rain

In order to investigate the decay of bronzes exposed to acid wet depositions, a comparative study has been performed by following the corrosion behaviour of different sets of bronze specimens exposed either to natural rain or to a similar solution, without organic compounds, artificially reproduced in laboratory. The as cast G85 bronze specimens were exposed to aggressive solutions for different periods through a wet-dry technique. The pH trend of the solutions and the amount of metals transferred into the solutions were periodically monitored. OM, SEM, XRD, RAMAN analyses and ac electrochemical measurements were performed on the artificially weathered specimens. Preliminary results, showing the difference between the ageing in natural and synthetic rain, suggest the influence of the organic components on the corrosion process. In particular, the growth of a more uniform protective layer of corrosion products on the metal surface exposed to the natural rain could be attributed to these components.

High Temperature Oxidation of Carbon/SiC/B4C Composite in Different Atmospheres

High temperature oxidation tests of carbon/SiC/B4C composite made from mixed powders of coke (51.2 wt%), SiC (38.8 wt%) and B4C (10 wt%) were carried out in different atmospheres of dry air, dry oxygen and wet air at temperature range from 600 to 1400°C. The oxidation had three different behaviours depending on the oxidation temperature ranges of below 700°C, 800-1000°C and above about 1100°C. Below about 700°C oxidation was relatively suppressed due to probably B2O3 liquid phaseformed from B4C. At about 800-1000°C protective B2O3 layer vaporized easily, and dense and homogeneous protective oxide layer was difficult to form on the surface, and then active oxidation proceeded in dry oxygen atmosphere. Particularly in wet air condition oxidation became much more active at this temperature range and oxidation proceeded deeply into inner part of the sample, because denseprotective layer could not be formed. While above about 1100°C dense and uniform protective layer formed o thesurface and protected further oxidation. The protective oxide layer formed at about 1200°C was suggested to be SiO2 rich phase and was known remarkably stable for oxidation even in wet air at about 900°C.