Protective Layer Research Articles

Improving surface finish of laser additively manufactured curvilinear surfaces via electropolishing and electroless coating

Abstract Laser directed energy deposition (LDED) is a very useful additive manufacturing (AM) technique for repairing and manufacturing complex shaped parts compared to traditional manufacturing techniques. However, the inadequate surface quality of the LDED fabricated components limits their direct utilization in different sectors. In addition, improving the surface finish of the curvilinear surfaces (useful for cooling channels and fuel nozzles) is also challenging. Hence, the current study focuses on surface modification of LDED fabricated SS 316L hollow cylindrical samples by combining electropolishing and electroless coating. We have performed electropolishing (two different currents, 8A and 15A) on the as-deposited (AD) sample with and without the application of the grinding process. The electropolishing reduced the roughness of the AD sample from 3.2 µm to 0.85 µm and 0.74 µm for 8A and 15A, respectively. The reduction in roughness was more at a higher current value due to the rapid anodic dissolution of the surface peaks. A further reduction in roughness was observed when grinding was performed before electropolishing. However, grinding resulted in higher material removal from the deposited surfaces and reduction in roughness was also minimal. Hence, only the electropolishing sample was selected for the next step, in which Ni-P electroless coating was performed on the surface to form a protective layer. After electroless coating, the COF and wear rate were reduced by 9.5 % and 25.6 % compared to the AD sample. Delamination and severe plastic deformation were the major wear mechanisms for the AD sample, whereas abrasion was dominant for the coated sample. The current work proposes a combined surface modification approach of electropolishing and electroless coating for the LDED processed components with curvilinear surfaces.

Experimental studies of the strength of reinforced concrete beams with a restored protective layer

The article presents the results of experimental studies to assess the strength of reinforced concrete beams with varying degrees of destruction of the protective layer of the working longitudinal reinforcement, followed by its restoration with a repair mixture. The test results of three series of prototypes, three samples in each series, are presented. Within the series, prototypes were made with the same longitudinal reinforcement, and the samples in each series differed in the degree of destruction of the protective layer of the longitudinal working reinforcement in the transverse bending zone. The samples were tested as freely supported beams loaded in the span by two identical concentrated forces. The results obtained made it possible to evaluate the role of longitudinal reinforcement, depending on the degree of destruction of its protective layer, in ensuring strength, forming a stress-strain state and the nature of destruction of reinforced concrete beams of rectangular cross-section in transverse bending zones.

Precision management of Fusarium fujikuroi in rice through seed coating with an enhanced nanopesticide using a tannic acid-ZnIIformulation.

Seed coating with fungicides is a common practice in controlling seed-borne diseases, but conventional methods often result in high toxicity to plants and soil. In this study, a nanoparticle formulation was successfully developed using the metal-organic framework UiO-66 as a carrier of the fungicide ipconazole (IPC), with a tannic acid (TA)-ZnII coating serving as a protective layer. The IPC@UiO-66-TA-ZnII nanoparticles provided a controlled release, triggered and regulated by environmental factors such as pH and temperature. This formulation efficiently controlled the proliferation of Fusarium fujikuroi spores, with high penetration into both rice roots and fungal mycelia. The product exhibited high antifungal activity, achieving control efficacy rates of 84.09% to 93.10%, low biotoxicity, and promoted rice growth. Compared to the IPC flowable suspension formula, IPC@UiO-66-TA-ZnII improved the physicochemical properties and enzymatic activities in soil. Importantly, it showed potential for mitigating damage to beneficial soil bacteria. This study provides a promising approach for managing plant diseases using nanoscale fungicides in seed treatment.

Stabilizing Wide‐Bandgap Perovskite with Nanoscale Inorganic Halide Barriers for Next‐Generation Tandem Technology

AbstractWide‐bandgap (WBG) perovskite solar cells (PSCs) play a crucial role in advancing perovskite‐based tandem solar cells. In WBG perovskite films, grain boundary (GB) defects are the main contributors to open‐circuit voltage (VOC) deficits and performance degradation. This report presents an effective strategy for passivating GBs by incorporating an inorganic protective layer and reducing the density of GBs in perovskite films. This is achieved by integrating potassium thiocyanate (KSCN) into I‐Br mixed halide WBG perovskites. It is reported for the first time that the incorporation of KSCN creates band‐shaped barriers along the GBs. In addition, KSCN enlarges the grains of perovskite film. Elemental and structural analyses reveal that these barriers are composed of potassium lead halide. Incorporating KSCN significantly enhances the fill factor and VOC of WBG single‐junction PSCs by reducing trap density. This results in high power conversion efficiencies of 19.22% (bandgap of 1.82 eV), 20.45% (1.78 eV), and 21.54% (1.70 eV) with a C60/bathocuproine electron transport layer, and 18.51% (1.82 eV) with a C60/SnO2. Furthermore, both operational and shelf stabilities are significantly improved due to reduced light‐induced halide segregation. By using inorganic‐halide‐passivated WBG sub‐cells, a monolithic all‐perovskite tandem solar cell with an efficiency of 27.04% is demonstrated.

ZnO doped PAMAM for asphalt improvement as anti-corrosive coatings.

Asphalt is widely used as a coating resin due to its excellent adhesion strength and cost-effectiveness; however, its limited corrosion protection necessitates enhancement. In this study, poly(amidoamine) (PAMAM), combined with zinc oxide (ZnO) nanoparticles, was incorporated into the asphalt matrix to improve its anticorrosive properties. Various ratios of PAMAM-ZnO nanocomposite (1, 2, 4, and 6% by weight) were added to the asphalt binder, with the materials characterized using XRD, ¹H-NMR, and SEM techniques. The 2% PAMAM-ZnO/asphalt ratio exhibited the most significant improvement, achieving a corrosion protection efficiency (η%) of 97.93%, as confirmed by Tafel analysis, and a charge transport resistance (RCT) of 75.91 Ω cm² according to electrochemical impedance spectroscopy (EIS) data. A combination of barrier formation and sacrificial protection drives the corrosion inhibition mechanism. The PAMAM-ZnO nanocomposite forms a highly uniform layer on the carbon steel surface, creating an effective physical barrier that prevents the penetration of corrosive agents, thereby minimizing defects like pinholes. This barrier effect is complemented by the sacrificial protection provided by the ZnO nanoparticles, which are more reactive than the underlying steel and preferentially interact with corrosive ions (e.g., chloride ions). This interaction leads to the formation of stable ZnO corrosion products, which enhance the barrier and reduce the likelihood of corrosion on the steel surface. Additionally, PAMAM facilitates the even distribution and strong adhesion of ZnO within the asphalt matrix, ensuring a durable protective layer. The synergic impact between the polymer barrier and sacrificial ZnO protection results in the exceptional corrosion resistance observed in the 2% PAMAM-ZnO/asphalt formulation, offering a promising approach for advanced anticorrosive coatings.

Supernatant of plant-associated bacteria potency against biofilms formed by foodborne pathogen and food spoilage bacteria.

Food products are often contaminated by pathogens and spoilage bacteria. Most of them can form biofilms, a community of cells embedded in protective extracellular matrix layers resistant to harsh conditions, including antibiotics. Therefore, alternative antibiofilm agents are required to overcome biofilm formation. This study aims to determine and quantify the antibiofilm activity of supernatants from plant-associated bacteria against biofilms of foodborne pathogen and food spoilage bacterium, namely Bacillus cereus and Bacillus subtilis. Plant-associated bacteria (PAB) have shown promising antibiofilm activities against biofilm-forming pathogens in previous studies. Thirteen PAB isolated from Ternate, Indonesia were used in this study. Supernatants of PAB were subjected to antimicrobial activity and quorum quenching detection, both using the well diffusion method. Four supernatants inhibited the growth of B. subtilis, but none affected the growth of B. cereus. Eight supernatants were able to disrupt the quorum sensing system of an indicator bacterium, wild-type Chromobacterium violaceum. Biofilm inhibition and destruction were quantified using 96-well microplates. The highest biofilm inhibition and destruction activities of PAB supernatants against each of B. cereus and B. subtilis biofilms were > 76%, and were later confirmed by light microscope and scanning electron microscope. Brine shrimp lethality assay (BSLA) was conducted and revealed that the selected PAB supernatants were non-toxic. The 16S rRNA gene of PAB were sequenced and they showed similarities to Bacillus, Priestia, and Chryseobacterium. Compounds in the supernatants were determined by GC-MS which revealed contents of fatty acids, ethyl esters, and diketopiperazines. Therefore, PAB supernatants have potential as antibiofilm agents against biofilm formed by Bacillus cereus and Bacillus subtilis.

Dual-responsive nanoparticles for enhanced drug delivery in breast Cancer chemotherapy.

Drug delivery efficiency often affects chemotherapy outcome due to dense collagen barrier in tumor environment. Here, we report a nanoparticle capable of pH and glutathione dual-responsive drug delivery to enhance the efficacy of breast cancer chemotherapy. Maleiminated polyethylene glycol and polylactide block copolymer were synthesized as a core material, doxorubicin was encapsulated into the nanoparticle by self-assembly. Thiocollagenase and maleimide were connected on the nanoparticle surface by click chemistry, and further coated with chondroitin sulfate as a protective layer to form dual-responsive doxorubicin nanoparticle. The results showed that the nanoparticle had the ability to penetrate deep tumor tissue, to target on CD44 of cancer cell, and to release doxorubicin in cancer cell in response to pH and glutathione signals, demonstrating superior anticancer efficacy in breast cancer-bearing mice. In conclusion, the dual-responsive nanoparticle could be used as a drug carrier to enhance drug delivery in breast cancer chemotherapy.

Assessment of the self-healing capacity of PVA fiber-reinforced composites by chloride permeability and stiffness recovery

This paper investigates the intrinsic ability of PVA fiber-reinforced cementitious composites to re-establish the durability properties of the uncracked state. Comparative chloride penetration tests are used as a direct measure to quantify the effect of self-healing on the chloride penetration resistance after cracking. Two different composites with cement to fly ash ratios of 1:1.5 and 1:2.0 were studied under the influence of healing periods of up to 28 days. After inducing cracks between 100 and 120 μm, samples were exposed to chlorides for 72 h and the resulting chloride penetration depth was compared to the unhealed state. Based on this procedure, a durability recovery index was proposed to quantify the material’s ability to re-establish its function as a protective layer after cracking. Results show that after 14 days of self-healing, chloride penetration through cracks was reduced between 81% and 99%. An extended healing period of 28 days leads to further reduction of the penetration depth to 84%–100%, indicating that most of the reaction takes place within the first 14 days of healing. While the stiffness recovery analysis showed that increasing cement content by 20% correlated with the formation of stronger healing products, no significant difference was found regarding crack closure.

Implementing federated learning over VPN-based wireless backhaul networks for healthcare systems

Federated learning (FL) is a popular method where edge devices work together to train machine learning models. This study introduces an efficient network for analyzing healthcare records. It uses VPN technology and applies a federated learning approach over a wireless backhaul network. The study compares different wireless backhaul channels, including terahertz (THz), E/V band (mmWave), and microwave, for their effectiveness. We looked closely at a suggested FL network that uses VPN technology over awireless backhaul network. We compared it with the standard method and found that using the FedAvg algorithm with Terahertz (THz) for communication gave the best accuracy. The time it took to reach a conclusion improved a lot, going from 55 seconds to an impressive 38 seconds. This emphasizes how having a faster communication link makes FL networks work much better. Furthermore, a three-step plan was executed to boost security, adopting a multi-layered method to safeguard the FL network and its confidential data. The first step involves integrating a private network into the current telecom infrastructure, establishing an initial layer of security. To enhance security further, licensed frequency channels are introduced, providing an extra layer of protection. The highest level of security is achieved by combining a private network with licensed frequency channels, complemented by an additional layer of security through VPN-based measures. This comprehensive strategy ensures the application of strong security protocols.

The Study of the Etching Resistance of YOF Coating Deposited by Atmospheric Plasma Spraying in HBr/O2 Plasma

Yttrium oxyfluoride (YOF) coatings with different oxygen content were prepared using atmospheric plasma spraying (APS) technology. The etching resistance of the coatings in HBr/O2 plasma was investigated. Shifts in diffraction peaks of the X-ray diffraction, along with XPS analysis conducted before and after etching, demonstrated that Br ions could replace O and F ions and fill the oxygen vacancies after exposure to HBr/O2 plasma, which is supported by the first-principles calculations. Br ions formed a protective layer on the surface of the YOF coating, slowing down further etching by Br ions. By adjusting the oxygen mass fraction in YOF powder, the oxygen vacancy concentration and Br ion filling were regulated to enhance etching resistance. YOF coatings with 6% oxygen content exhibited improved etching resistance compared to YOF coatings with 3% and 9% oxygen content. This improvement was primarily due to the increased Br ion concentration. These findings provide a new approach for developing coatings with enhanced etching resistance.

Breaking Activity‐Durability Inverse Relationship via Electrode Engineering by Utilizing β‐MnO2/RuO2 Heterostructures for Efficient Seawater Electrolysis

AbstractSignificant efforts are underway to enhance the efficiency of water electrolysis for sustainable hydrogen production. Approaches that were explored are the design of an efficient anode, engineering of electrolytes, and application of diffusion protective layer over the catalyst to protect it from corrosive reactions. Here we are exploring the engineering of electrode fabrication to enhance the efficacy of anode catalysts by ensuring that the materials are carefully selected. β‐MnO2 has been used to develop a cost‐effective method for electrode fabrication that establish a Schottky junction at heterostructure interface. This method transforms commercial RuO2, which is considered to be less active and stable, highly selective for chlorine oxidative reactions, into a highly active, stable, and OER‐selective in alkaline medium and surrogate seawater. With the help of thorough electrochemical techniques, we found that this engineering significantly improves the effective electrochemical surface area, and higher kinetics and conversion per unit site, profoundly affecting the charge transfer mechanism and optimizing the adsorption of OER intermediates, resulting in much‐increased mass activity. It is observed that the selectivity of the OER was enhanced due to the Lewis acid repercussions of β‐MnO2.

Polymeric Ionic Liquid-Enabled In Situ Protection of Li Anodes for High-Performance Li-O2 Batteries.

Redox mediators (RMs) have shown promise in enhancing Li-O2 battery cycling stability by reducing overpotential. However, their application is hindered by the shuttle effect, leading to RM loss and Li anode corrosion. Here, we introduce a polyionic liquid, poly (1-Butyl-3-vinylimidazolium bis(trifluoromethanesulfonylimine)) ([PBVIm]- TFSI) as an additive, showcasing a novel Li anode protection strategy for LiI-mediated Li-O2 batteries. [PBVIm]+ cations migrate to the Li anode, forming a protective cationic shield that promotes uniform Li+ deposition. The addition of [PBVIm]-TFSI enhances the cycling stability, achieving 105 cycles at 200 mA·g-1, compared to the cell with LiI which exhibited 38 cycles under the same conditions. Synchrotron X-ray tomography reveals the evolution of this protective layer, providing insights into its formation mechanism, in conjunction with XPS analysis. Our findings offer a new approach to Li anode protection in Li-O2 batteries, emphasizing the critical role of interfacial engineering for battery performance.

Polyethylene Glycol-Protected Zinc Microwall Arrays for Stable Zinc Anodes.

Aqueous zinc-ion batteries promise good commercial application prospects due to their environmental benignity and easy assembly under atmospheric conditions, positioning them as a viable alternative to lithium-ion batteries. However, some inherent issues, such as chaotic zinc dendrite growth and inevitable side reactions, challenge the commercialization progress. In this work, we imprint highly ordered zinc microwall arrays to regulate the electric field toward uniform Zn deposition. Afterward, coating a polyethylene glycol protection layer on the zinc microwalls aims to passivate the surface defects that rise unintentionally by mechanical imprinting. Polyethylene glycol can also boost oriented Zn deposition along the (002) plane and inhibit hydrogen gas production, further enhancing the stability of such three-dimensional (3D) hybrid anodes. Compared to the messy electric field near the polyethylene glycol-protected Zn foil, the uniform electric field provided by these 3D hybrid anodes can regulate the Zn deposition behaviors, enabling a longer lifespan and thus certifying the necessity of adding 3D microstructures. Additionally, 3D microstructures can offer a larger surface area than that of the planar Zn foil, providing more reaction sites and higher specific capacity. In this case, the 3D hybrid electrode exhibits a good initial capacity of approximately 120 mA h/g at a current density of 5 A/g and a nice retention of more than 80% after 800 cycles. The proposed scheme paves the way for a long-term stable 3D zinc anode solution with promising application prospects.

Synergistic Long-Term Protection of Inorganic and Polymer Hybrid Coatings for Free-Dendrite Zinc Anodes.

Constructing an artificial solid electrolyte interface protective layer on the surface of the zinc anode is an effective strategy for addressing dendrite growth, passivation, and the hydrogen evolution reaction in aqueous zinc-ion batteries. This study introduces a robust interlayer composed of a polyvinyl butyral matrix decorated with SiO2 particles (PS). Adsorption of water by Si-OH on the surface of SiO2 leads to excellent hydrophilicity and accelerates the desolvation of ions. A highly stable and hydrophilic PS coating enhances ion migration and possesses ultralong protection ability, ensuring uniform ion deposition and a lower nucleation barrier. Anodes protected by the PS coating achieve long-term cycling stability of >4000 h at 2 mA cm-2 in symmetric cells. The assembled PS-Zn//NH4V4O10 full cells exhibit superior electrochemical performance, demonstrating their potential for practical applications in rechargeable zinc batteries.

Advanced bioengineering strategies broaden the therapeutic landscape for corneal failure

The cornea acts as the eye foremost protective layer and is essential for its focusing power. Corneal blindness may arise from physical trauma or conditions like dystrophies, keratitis, keratoconus, or ulceration. While conventional treatments involve medical therapies and donor allografts—sometimes supplemented with keratoprostheses—these options are not suitable for all corneal defects. Consequently, the development of bioartificial corneal tissue has emerged as a critical research area, aiming to address the global shortage of human cornea donors. Bioengineered corneas hold considerable promise as substitutes, with the potential to replace either specific layers or the entire thickness of damaged corneas. This review first delves into the structural anatomy of the human cornea, identifying key attributes necessary for successful corneal tissue bioengineering. It then examines various corneal pathologies, current treatments, and their limitations. Finally, the review outlines the primary approaches in corneal tissue engineering, exploring cell-free, cell-based, and scaffold-based options as three emerging strategies to address corneal failure.

Oriented and Continuous Phase Epitaxy Enabled by A Highly Dendrite‐Resistant Plane Toward Super‐High Areal Capacity Zinc Metal Batteries

AbstractUnstable Zn metal anodes with dendrites/side reactions are becoming the main obstacle to the practical application of zinc‐based aqueous batteries. Epitaxial growth has been considered to be an effective strategy for solving these issues, especially for inducing the (002) plane growth. Nonetheless, the (002)‐textured Zn is difficult to achieve highly stable Zn anode under high capacity resulting from its large lattice distortion. Herein, the Cu single atom anchored polymeric carbon nitride (Cu@PCN) is synthesized by a facile thermal polymerization method. Serving as multifunctional protective layer on Zn surface, the Cu@PCN can provide massive nucleation sites at a nano‐level and uniformize the electron distribution through coordination engineering. Optimizing the coordination structures of single Cu and N atoms within the carbon matrix enables a redistribution for electric field and regulates ion flux. More importantly, this coordination strategy with single atoms is first reported to customize oriented and continuous phase epitaxy along highly dendrite‐resistant Zn(101) plane by reducing (101) surface energy. This pattern of oriented dense deposition leads to stable and reversible Zn plating/stripping is achieved, which delivers an extended cycling life of 550 h at 10 A cm−2, 20 mAh cm−2. The practical full cell also displays stable performance for 1200 cycles.

Thermo-optical analysis of a nanocone based solar absorber for thermophotovoltaic applications

Abstract We investigate the optical and thermal response of a 2D photonic crystal absorber composed of tungsten nanocones, with complete and truncated shapes used in a solar thermophotovoltaic (STPV) system. We explain how the absorption and temperature of the structure are affected by the presence of a protection layer, lens and an emitter. The total efficiency and contribution of thermal emittance of complete nanocone arrays are compared with truncated absorbers. Based on our results, the efficiency of a non-protected nanocone hits 67% at 400 sunlight and the temperature reaches 1350 K. By adding a silica layer on the absorber, the efficiency slightly reduces to 61%. In addition, we observed a reduction in the efficiency of all studied absorbers at higher sunlight concentration factors. Our results also indicate that the thickness of a silica layer on the tungsten substrate does not have a noticeable change in the efficiency. Finally, the deformation of the structure due to surface diffusion is studied. This study paves the way toward a multi-physical analysis of photonic crystal absorbers in STPV systems.

Predictive Modeling and Adsorption Behavior, Kinetics, and Thermodynamic Studies of <i>Anthocleista grandiflora </i>Leaf Extract for Corrosion Inhibition of Carbon Steel in Seawater

This study investigates the corrosion inhibition performance of Anthocleista grandiflora leaf (AGL) extract on carbon steel in seawater, considering the effects of temperature, immersion time, and inhibitor concentration. Predictive modeling, adsorption behavior, and the kinetics and thermodynamics of the inhibition process were examined. The weight loss technique,characterization techniques combined with response surface methodology (RSM), revealed that the AGL extract follows the Langmuir adsorption model, exhibiting physical adsorption with ΔG values between −16.24 to −15.49kJ/mol, indicating spontaneous and endothermic inhibition. The thermodynamic parameters entropy (−198.87 to −52.58 J/mol), enthalpy (20.42 to 53.42 kJ/mol), and activation energy (13.68 to 56.32 kJ/mol further support this. The corrosion reaction follows first-order kinetics, with the half-life decreasing as the rate constant and extract concentration increase.The SEM images revealed that the AGL extract formed a protective surface layer on the mild steel, effectively preventing pitting. This protective effect became more pronounced as the concentration of the extract increased. RSM optimization identified optimal conditions for maximum inhibition efficiency (98.70%) and corrosion rate (0.058 mm/y) at 800 ppm, 303 K, and 45 days, with a prediction accuracy of 95%, making it suitable for application in the oil and gas industry.

Effective Stabilization of Organic Cathodes Through Formation of a Protective Solid Electrolyte Interface Layer via Reduction.

2,5-Dihydroxy-1,4-benzoquinone (DHBQ) is a promising cathode material, but its high solubility in electrolytes leads to rapid capacity degradation. This study investigates the dilithium salt of DHBQ, Li2DHBQ, as a cathode material for lithium-ion batteries (LIBs). Despite minimal solubility, Li2DHBQ cathodes suffer rapid capacity decay due to severe morphological damage within the voltage range of 1.5-3.0 V. To stabilize morphology, we promoted a protective solid electrolyte interphase (SEI) layer on Li2DHBQ particles by lowering the discharge cutoff voltage. Cycling the battery with a 0.5 V discharge cutoff voltage achieved an optimal SEI layer, significantly improving Li2DHBQ's morphological stability. Consequently, the battery maintained 170 mAh g-1 with a low decay rate of 0.16% within a voltage range of 0.5-3.0 V after 200 cycles at 500 mA g-1. Furthermore, initial cycling at a 0.5 V discharge cutoff for 20 cycles to form an SEI layer, followed by cycling at a normal 1.5 V discharge cutoff, retained a higher capacity of 187 mAh g⁻¹ after 200 cycles. This study demonstrates the effectiveness of forming a cathode SEI layer at low discharge voltages as a new approach to stabilizing organic cathode materials.

Porous V2CTx MXene as a High Stability Zinc Anode Protective Coating.

Aqueous Zn batteries exhibit significant research potential owing to their environmental friendliness and high energy density. Nevertheless, the formation of dendrites on the zinc anode and the sluggish diffusion kinetics of zinc ions adversely affect the cycle life of zinc ion batteries. In this study, we employ porous V2CTx (MVMX) as a protective layer for the zinc anode. The uniform porous structure of MVMX promotes active site exposure and facilitates the transport of zinc ions. Remarkably, the Zn@Ti half-cell demonstrated an average CE of 99.7% in 1500 cycles. Furthermore, the Zn-Zn symmetric battery exhibited stable cycling for 1600 h at current densities of 5 mA cm-2 and 1 mAh cm-2. Additionally, the MVMX@Zn||V2O5 full cell exhibited a capacity of 198 mAh g-1 and retained a capacity of 124.75 mAh g-1 after 5000 cycles at 1 A g-1, demonstrating the potential of employing alternative MXenes for fabricating stable zinc anodes.