Functional Coatings Research Articles

Xiuyan jade waste as antibacterial additives for functional coatings

Jade waste is a normal byproduct that makes up much more than the amount of jade extracted. Therefore, recycling jade waste is worth investigating from the point of view of energy conservation. Moreover, it is an environment-friendly material, which is desirable for use in building materials. In this study, Xiuyan jade waste was repurposed as antibacterial additives for building coatings. The powder waste was activated by milling and subsequent annealing. The antibacterial properties of the treated waste were mostly related to the annealing temperatures. Based on the investigations of the phase change and the release of metal ions of a series of samples and their antibacterial activities, the antibacterial mechanism of the treated samples was explored experimentally. The most applicable sample for coatings was finally chosen by considering its pH values and its antibacterial abilities. Antibacterial testing showed that the addition of treated jade waste could enhance the bacterial inhibition rate of building coatings from 60% to 99.9%.

Mechanical Behavior of Hybrid Thin Films Fabricated by Sequential Infiltration Synthesis in Water-Rich Environment.

Sequential infiltration synthesis (SIS) is an emerging technique for fabricating hybrid organic-inorganic materials with nanoscale precision and controlled properties. Central to SIS implementation in applications such as membranes, sensors, and functional coatings is the mechanical properties of hybrid materials in water-rich environments. This work studies the nanocomposite morphology and its effect on the mechanical behavior of SIS-based hybrid thin films of AlOx-PMMA under aqueous environments. Water-supported tensile measurements reveal an unfamiliar behavior dependent on the AlOx content, where the modulus decreases after a single SIS cycle and increases with additional cycles. In contrast, the yield stress constantly decreases as the AlOx content increases. A comparison between water uptake measurements indicates that AlOx induces water uptake from the aqueous environment, implying a "nanoeffect" stemming from AlOx-water interactions. We discuss the two mechanisms that govern the modulus of the hybrid films: softening due to increased water absorption and stiffening as the AlOx volume fraction increases. The decrease in the yield stress with SIS cycles is associated with the limited mobility and extensibility of polymer chains caused by the growth of AlOx clusters. Our study highlights the significance of developing hybrid materials to withstand aqueous or humid conditions which are crucial to their performance and durability.

Effect of Vacancy Defects and Hydroxyl on the Adsorption of Glycine on Mg(0001): A First-Principles Study

Glycine (Gly), as one of the fundamental components of biomolecules, plays a crucial role in functional biomolecular coatings. The presence of structural defects and hydroxyl-containing functional groups in magnesium (Mg) materials, which are commonly used as biomedical materials, significantly affects their biocompatibility and corrosion resistance performance. This study computationally investigates the influence of vacancy defects and hydroxyl groups on the adsorption behavior of Gly on Mg(0001) surfaces. All potential adsorption configurations are considered through first-principles calculations. The findings indicate that stronger chemisorption occurs when Gly is positioned at the edge of the groove, where the surface has a vacancy defect concentration of 1/3. Among the four adsorption locations, the fcc-hollow site is determined to be the most favorable adsorption site for hydroxyl. The adsorption energy of Gly on the Mg(0001) surface containing the hydroxyl (−1.11 eV) is 0.05 eV more than that of on the Mg(0001) surface (−1.16 eV). The adsorption energies, electronic properties, charge transfer, and stable configurations are calculated to evaluate the interaction mechanism between Gly and defective surfaces. Calculated results provide a comprehensive understanding of the interaction mechanism of biomolecules on defective Mg surfaces and also indicate the directions for future experimental research.

Simultaneous Performance and Stability Enhancement in Intermediate Temperature Solid Oxide Fuel Cells by Powder-Atomic Layer Deposited LSCF@ZrO2 Cathodes.

Employing porous structures is essential in high-performance electrochemical energy devices. However, obtaining uniform functional coatings on high-tortuosity structures can be challenging, even with specialized processes such as atomic layer deposition (ALD). Herein, a novel method for achieving a porous composite electrode for solid oxide fuel cells by coating La0.6 Sr0.4 Co0.2 Fe0.8 O3 -δ (LSCF) powders with ZrO2 using a powder ALD process is presented. Unlike conventional ALD, powder ALD can be used to fabricate extremely uniform coatings on porous electrodes with a thickness of tens of micrometers. The powder ALD ZrO2 coating is found to effectively suppress chemical degradation of the LSCF electrodes. The cell with the powder ALD coated cathode shows a 2.2 times higher maximum power density and 60% lower thermal degradation in activation resistance than the bare LSCF cathode cell at 700-750 °C. The result demonstrated in this study is expected to have significant implications for high-performance and durable electrodes in energy conversion/storage devices.

Mathematical methods in studying temperature-time conditions of the friction surfacing in the manufacture of functionally organized steel-aluminum compositions

A mathematical model for studying temperature and time conditions of the process of friction surfacing in the manufacture of functionally organized steel-aluminum compositions has been developed and validated. Bars made of pure aluminum grade ER1100 were used as the consumable rod material during friction surfacing. The substrate in the form of a rectangular plate was made of high-quality steel 20. The geometric model of the object when modeling the process of friction surfacing in the ANSYS 2021R2 software package was specified in the form of a rod and a substrate. The initial data for calculating temperature-time conditions of the friction surfacing process are: geometric parameters of the simulation object; characteristics of thermal loads of the heating source which depend on the technological parameters of the surfacing mode (the speed of axial rotation of the rod, axial pressure, boundary conditions of the simulation object for the temperature problem), and auxiliary parameters that determine the order of calculations. The thermal power arising at the point of physical contact between the rotating consumable rod and the substrate was considered a parameter of the source thermal load. The calculation of heat propagation for the friction surfacing process was carried out according to a scheme with a normally circular source located on the substrate surface. The calculation scheme directly reflects the main feature of the friction surfacing process: the introduction of heat due to friction between the rotating consumable rod and the substrate. It is shown that taking into account the boundary conditions and geometric features of the 3D model provide a satisfactory convergence of developed mathematical model and ensure the uncertainty of no more than 5 % in determining the heating temperature of the substrate when forming functional aluminum coatings, as well as composite materials on their base when surfacing them on the surface of steel substrates.

A functional coating with mechanoluminescent properties for sensing cavitation erosion and early warning of protection failure

Protective materials coated on the surface of fluid machinery are often used to slow down the damage caused by cavitation. Once the protective material fails, there is no real-time monitoring to predict, which will directly threaten the safe operation of the equipment. In this work, we designed a functional SrAl2O4: Eu2+, Dy3+ coating by atmospheric plasma spraying (APS), which can sense the impact of bubble implosion and realize the early warning of the failure of anti-cavitation erosion polyurethane (PU) coating. It is found that the luminescent properties of the functional coatings are easily affected by lattice defects, amorphous phase and valence state of europium ions. The functional coating is more sensitive to the perception of micro-jets and shock waves after vacuum thermal reduction treatment, and can distinguish the difference in stress by the brightness of the light. More importantly, when the surface polyurethane coating is removed by cavitation erosion (CE) down to 0.1 mm, this functional coating emits light to warn the polyurethane coating of impending failure. Therefore, this work provided a solution for sensing CE and predicting when the protection would fail.

Trajectories of titanium powder particles of diffferent size in a plasma flow

The study focused on analyzing the trajectories of powder particles within a plasma flow, a process utilized for applying functional coatings and producing powders. An overview of contemporary scientific research dedicated to modeling these processes is presented. The primary objective of this study was to ascertain how the particle size of the powder, used as a raw material, influences the path of particles within a vertically directed plasma flow. We examined three sizes of titanium powder: 1 μm, 50 μm and 100 μm. These sizes were chosen based on production practices for the considered processes and the particle size distribution of the powder material used in full-scale experiments, employing specialized CAMSIZER-XT equipment. Our study reveals the significant impact of powder particle size on various parameters, including the opening angle, length, and width of the illuminated section of the plasma torch, as well as the distance traveled by particles entrained by the plasma flow from the plasma head. To investigate these effects, we conducted computer simulations, followed by validation through full-scale experiments for each case. Specifically, we employed the MAK-10 laboratory plasma facility at the Institute of Metallurgy, Ural Branch, Russian Academy of Sciences, which is designed for powder production and functional coatings. In order to ensure the reliability of our measurements, we performed statistical data processing of the full-scale experiment results using scatter plots and determination of their average values. The comparative analysis of results from both natural and computer experiments demonstrated a satisfactory level of convergence. This comparative analysis of three particle sizes of powder enabled us to formulate practical recommendations for enhancing equipment and process technology in the context of the considered procedures. Furthermore, our article introduces a computer model capable of predicting the dimensions of the reactor (the chamber for receiving powder materials), the optimal shape of components within the plasma facility, and the positioning of the substrate on which functional coatings are applied. This model can be applied to address similar problems within the scope of this study, facilitating the control of coating application processes and powder production.

Functional Surface Coating to Enhance the Stability of LiNi0.6Mn0.2Co0.2O2

Parasitic reactions are responsible for continuous performance loss during the normal operation and storage of lithium-ion batteries, particularly for those using nickel-rich cathode materials. Among many contributors, residual Li2CO3 on the surface of nickel-rich cathodes plays a detrimental role in promoting parasitic reactions, and hence accelerates the performance loss of those cathode materials. In this work, a wet impregnation process was utilized to convert the detrimental Li2CO3 and LiOH impurities into a beneficial functional surface coating comprising phosphates. Specifically, hydro-phosphates were used as the functional surface modification agents to mitigate the detrimental effect of surface residuals. The best electrochemical performance was achieved by modifying LiNi0.6Mn0.2Co0.2O2 with a diluted dihydro-phosphate solution (pKa = 7.2), while the metal cation had a negligible impact on the electrochemical performance. This work provides a cheap and simple method for enabling the high performance of nickel-rich cathodes.

AIEgen orthopalladated hybrid polymers for efficient inactivation of the total coliforms in urban wastewater

Monitorable AIE polymers with a bioactive pattern are employed in advanced biomedical applications such as functional coatings, theranostic probes, and implants. After the global COVID-19 pandemic, interest in developing surfaces with superior antimicrobial, antiproliferative, and antiviral activities dramatically increased. Many formulations for biocide surfaces are based on hybrid organic/inorganic materials. Palladium (II) complexes display relevant activity against common bacteria, even higher when compared to their uncoordinated ligands. This article reports the design and synthesis of two series of orthopalladated polymers obtained by grafting a cyclopalladated fragment on two different O, N chelating Schiff base polymers. Different grafting percentages were examined and compared for each organic polymer. The fluorescence emission in the solid state was explored on organic matrixes and grafted polymers. DFT analysis provided a rationale for the role of the coordination core. The antibacterial response of the two series of hybrid polymers was tested against the total coliform group of untreated urban wastewater, revealing excellent inactivation ability.

Microstructural Analysis and Electrochemical Behavior of Functional Gradient Coating Hydroxyapatite/Tricalcium Phosphate on Ti-6Al-4 V by Plasma Spraying Method

Microstructural Analysis and Electrochemical Behavior of Functional Gradient Coating Hydroxyapatite/Tricalcium Phosphate on Ti-6Al-4 V by Plasma Spraying Method

3D Xanthium-like of Ni-Co-Zn ternary alloys as superhydrophobic coatings toward porous Ti surface for its anti-icing performances

Super-hydrophobic surface has attracted great interests as functional coatings in spacecraft wings and wind-turbine fans. With the ever-increasing demands of durability and low cost, the scopes for industrial application of hydrophobic coatings have been restricted. Herein we proposed an innovative and simple approach for electroplating Ni0.12Co0.88-xZnx (x = 0–0.36) coatings toward porous Ti substrate. Featuring as 3D Xanthium-like spherical textures, the Ni-Co-Zn ternary alloy coatings were achieved by optimizing the Zn2+ concentration and complexing agent (Na3Cit) in bath. Results validated that its crystal size was refined into ∼300 nm, leading into pinning growth through hole-hole linked porous channel of Ti substrate to increase interfacial strength. Based on the wettability tests, it depicted the water-droplet contact angle (WCA) value of 126.3° attached with sliding angle (SA) of 17.5° for coating samples after being exposed in air for 14 days. Further studies of different ageing treatments on micro structural evolution and super-hydrophobic characteristics were well explored. Through artificial ageing at 200 °C, its attained super-hydrophobic surfaces shorted than 7 days, showing the maximal WCA value up to 153.2° and SA ≤ 7.8° for Ni0.12Co0.88-xZnx (x = 0.24) samples, which was mainly contributed to the self-assembly of multi-tentacles ZnO dendrites. Meanwhile the anti-icing behaviors were compared and featured as peach blossom at −10 °C for all the samples. The icing-delay time of water droplets on coating samples was >1425 s, which was 20 times longer than that of porous Ti substrate. Similarly, it was higher than 90 % for its self-cleaning efficiency based on salt pollutants. Besides the mechanical durability of tested samples against the abrasion-resistant tests and water impact-resistance tests were studied. Results implied that good durability was achieved for Ni-Co-Zn superhydrophobic coatings, but sanded surfaces within a serious decrease of WCA was obtained after a continuous testing for 30 min by abrasion-resistant tests because of the partial destruction of Xanthium-like spherical textures. With the respect to reconstructing of multi-tentacles ZnO dendrites onto the Ni-Co-Zn coatings in air, it was the bio-inspired strategies for self-healing super hydrophobic metal coatings used in warship surfaces, etc.

Probiotic and synbiotic edible coatings: Effects on Lacticaseibacillus casei viability and general quality of minimally processed fruit during storage

This study assessed the effects of sodium alginate (ALG) edible coatings added with Lacticaseibacillus casei 01 (Lc-01) and/or fructooligosaccharides (FOS) on the chemical composition (sugars, organic acids and volatile compounds), quality parameters (firmness, weight loss, color, pH, titratable acidity-TA, total soluble solids-TSS and enzymatic activity), sensory properties, and probiotic survival (during simulated gastrointestinal exposure and storage) of minimally processed mango and melon during refrigerated storage (5 °C, 12 days). The surface characteristics of the coatings were also evaluated. Coatings added with Lc-01 and/or FOS were able to maintain the quality of mango and melon, delaying the increase in TSS, pH, and sugar content (glucose and fructose), and the decrease of organic acids, resulting in a reduction in weight loss and greater firmness. The effect was more pronounced for mangos. ALG-SYN (ALG, FOS, and Lc-01) coating performed better, with decreased enzyme activity, delay in color development, a higher concentration of volatile compounds, and more adequate sensory properties (flavor, texture, and appearance). Lc-01 counts remained >6 log CFU/g during storage and after in vitro digestion. Functional edible coatings can be used as an alternative to extending the shelf life of minimally processed mango and melon.

Click chemistry of PMHS for fabrication of robust, transparent and hydrophobic silicone resin coating on wood substrate at room temperature

Based on click chemistry of poly(methylhydrogen)siloxane (PMHS), an environment-friendly method was proposed for in-situ fabrication of robust, transparent, UV-resistant and hydrophobic silicone resin coating (SRC) at room temperature by simply brushing a mixture of PMHS, tetramethyltetravinyl cyclotetrasiloxane (V4), and Karstedt catalyst on wood surface. The mechanism for click chemistry of PMHS and the continuous curing characteristic of SRC was discussed based on the characterization of SRC by FTIR and XPS. The effects of the mass ratio of PMHS to V4 and curing time on the properties of SRC and the modified wood were investigated. Results showed that SRC with the mass ratio of PMHS to V4 of 5:1 possessed the best mechanical stability, and the mechanical stability increased with curing time and temperature. SRC improved significantly the hydrophobicity and water-repellency of wood by increasing the water contact angle from 27.2° to 123.1° and decreasing the water absorption rate from 103 % to 16 %. SRCs showed excellent transparency with an average transmittance of 92.3 % at 400–1100 nm. The UV resistance of SRC was 6 times higher than that of varnish coating. The click chemistry of PMHS will find great application in rapid fabrication of functional coatings on wood surface by using PMHS and any vinylated reagent or micro-/nano-particles.

Experimental Complex for Spectral Diagnostics of Particle Flow Temperature during Gas-Thermal Spraying

The paper presents an instrumental diagnostic complex developed by the authors. The compact LR1 spectrometer for spectral diagnostics of particle temperature of two-phase flow is an integral part of the complex, as well as the calibration tool with the reference emitter. Additionally, a special emitter consisting of miniature light bulbs attached closely to each other was used in test experiments. This special emitter served as a simulation model of particle thermal radiation of gas-thermal flow used for spraying of functional coatings on technical products. The program-controlled adjustment of current flow through bulbs interconnected in different configurations yields a variety of simulated test histograms of the temperature distribution of the bulbs that correspond to actual particle temperature distribution histograms. The emitter with light bulbs has been used as a simulation model to confirm the validity of the physical and mathematical model of the integral (total) spectrum of particle thermal radiation for the proposed experimental spectrum registration method employing the LR1 spectrometer.

Antifungal Activity of Chitosan/Poly(Ethylene Oxide) Blend Electrospun Polymeric Fiber Mat Doped with Metallic Silver Nanoparticles.

In this work, the implementation of advanced functional coatings based on the combination of two compatible nanofabrication techniques such as electrospinning and dip-coating technology have been successfully obtained for the design of antifungal surfaces. In a first step, uniform and beadless electrospun nanofibers of both polyethylene oxide (PEO) and polyethylene (PEO)/chitosan (CS) blend samples have been obtained. In a second step, the dip-coating process has been gradually performed in order to ensure an adequate distribution of silver nanoparticles (AgNPs) within the electrospun polymeric matrix (PEO/CS/AgNPs) by using a chemical reduction synthetic process, denoted as in situ synthesis (ISS). Scanning electron microscopy (SEM) has been used to evaluate the surface morphology of the samples, showing an evolution in average fiber diameter from 157 ± 43 nm (PEO), 124 ± 36 nm (PEO/CS) and 330 ± 106 nm (PEO/CS/AgNPs). Atomic force microscopy (AFM) has been used to evaluate the roughness profile of the samples, indicating that the ISS process induced a smooth roughness surface because a change in the average roughness Ra from 84.5 nm (PEO/CS) up to 38.9 nm (PEO/CS/AgNPs) was observed. The presence of AgNPs within the electrospun fiber mat has been corroborated by UV-Vis spectroscopy thanks to their characteristic optical properties (orange film coloration) associated to the Localized Surface Plasmon Resonance (LSPR) phenomenon by showing an intense absorption band in the visible region at 436 nm. Energy dispersive X-ray (EDX) profile also indicates the existence of a peak located at 3 keV associated to silver. In addition, after doping the electrospun nanofibers with AgNPs, an important change in the wettability with an intrinsic hydrophobic behavior was observed by showing an evolution in the water contact angle value from 23.4° ± 1.3 (PEO/CS) up to 97.7° ± 5.3 (PEO/CS/AgNPs). The evaluation of the antifungal activity of the nanofibrous mats against Pleurotus ostreatus clearly indicates that the presence of AgNPs in the outer surface of the nanofibers produced an important enhancement in the inhibition zone during mycelium growth as well as a better antifungal efficacy after a longer exposure time. Finally, these fabricated electrospun nanofibrous membranes can offer a wide range of potential uses in fields as diverse as biomedicine (antimicrobial against human or plant pathogen fungi) or even in the design of innovative packaging materials for food preservation.

Do Functional Coatings Work for Solar Panel Dust Mitigation?

Do Functional Coatings Work for Solar Panel Dust Mitigation?

Facile fabricated transparent anti-smudge coating with high hardness and excellent flexibility from MTQ and branched silicone resins

The demand for high-transparent functional coatings with glass-like hardness, polymer-like flexibility, and anti-smudge properties has increased significantly, especially for foldable touchscreens. However, it is challenging to achieve all the required properties in a coating because the realization of these properties may conflict with each other. In this study, we present a facile method for preparing a special organic-inorganic hybrid coating by utilizing epoxy MTQ silicone resins and amine-terminated hyperbranched polysiloxane (HPSi). The chemical structure of the MTQ resin was fine-tuned to obtain the optimal M/T/Q ratio, and a novel HPSi with rich crosslinking sites and excellent flexibility was prepared as the curing agent. The resulting hybrid network imparted the coating with exceptional hardness (pencil hardness, 7–9H) and excellent flexibility (<2 mm bend diameter). In addition, by modifying the MTQ resin with fluorosilane, the surface energy of the coating was reduced to 14.8 ± 0.4 mJ/m2 and its anti-smudge and self-cleaning properties were improved without sacrificing the transparency of the coating (99.4 % at 550 nm). Notablely, even after 1000 cycles of steel wool abrasion, these coatings still maintain their outstanding performance. This study provides a promising strategy for the development of hard, flexible, and anti-smudge coatings suitable for foldable displays and other related fields.

Study of stress-driven cracking behavior and competitive crack growth in functionally graded thermal barrier coatings

Thermal barrier coatings' (TBCs) stability and toughness are essential for insulating aero-engine parts. However, during service, the thickness of thermally grown oxide (TGO) will have an impact on the growth of internal vertical and horizontal cracks as well as the cracking and spalling of the coating, which may ultimately fail as a result of the aforementioned factors. The competitive growth of vertical and horizontal fractures in three functional gradient thermal barrier coatings (FG-TBCs) created with varied gradient index P magnitudes is investigated in this study. Gaining a thorough grasp of how competitive growth affects coating failure under various compositional and gradient structural parameters is the goal. Additionally, this work explores the effects of various TGO thicknesses on early crack expansion as well as the stress characteristics within the FG-TBCs. The research takes into account how crack growth changes the stress condition as well as the implications of crack extension rate, route, and form on coating failure. Our results show that the stress step phenomena in the FG-TBCs occurs in various places for various P values. The expansion of cracks in the top coat (TC) is fueled by this stress phase. Furthermore, a greater vertical crack extension length is obtained with a higher P value, with further expansion being prevented by horizontal cracks along the extension path. Notably, thicker TGO coatings change the direction and rate of expansion of cracks, both vertical and horizontal.

Research Status of Aluminum Base Coating on Titanium Alloy

At present, in the aviation industry, titanium alloy is mainly used to manufacture parts such as compressor discs, blades, and the casings of aircraft engines. When titanium alloys are in service, high temperature is generated due to high-speed running friction, which requires them to have high-temperature oxidation resistance and friction resistance. If they are used in an environment with salt corrosion, titanium alloys will face thermal corrosion, which limits their wider practical applications. At present, there are many methods to protect titanium alloys. This paper mainly includes alumina-based coatings and some preparation methods. The characteristics and functional mechanisms of three functional coatings for the service environment, namely highly temperature-resistant alumina-based coating, thermal corrosion-resistant alumina-based coating, and wear-resistant alumina-based coating, are summarized. Finally, the development direction of composite coatings of titanium and titanium alloys for a complex service environment is suggested.

ε-Polylysine and soybean protein isolate form nanoscale to microscale electrostatic complexes in solution: properties, interactions and as antimicrobial edible coatings on citrus

A feasible approach to enhance the antimicrobial efficacy of ε-polylysine (PL) in applications is to form delivery complexes with delicate structures and good dispersion properties. This work aims to study the multiscale structures, properties and interactions, and edible coating applications of the electrostatic complex formed by PL and soy protein isolate (SPI). When the mass ratio of SPI to PL (SE) was between 5 and 15, especially 11, microscale solid-liquid phase separation occurred in the system due to the small absolute zeta potential. When the SE was in the range of 15–20, the system formed a stable nanoscale suspension, the average particle size and zeta potential were 191 nm and −20 mV, respectively. The physicochemical properties of the complexes were investigated including the colloidal properties, spectroscopy and interactions analysis, viscosity, contact angle, and antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Penicillium expansum. Finally, the in vivo application on citrus demonstrated that the nanoscale PL/SPI electrostatic complex (SE = 20) as functional coatings has both barrier and antimicrobial activities. The study provides a novel application strategy for PL and nanoscale electrostatic complexes as postharvest coatings.