Nanostructured Coatings Research Articles

Nanostructured Coatings (Ti,Zr)N as a Barrier to Hydrogen Diffusion into Ti0.16Pd (wt.%) Alloy

The results of a study of structure, phase, and chemical compositions of nanostructured (Ti,Zr)N coatings formed by vacuum arc deposition on Ti0.16Pd (wt.%) alloy substrates are reported. The coating composition was varied depending on the quasi-binary system δ—TiN—δ—ZrN. The coatings were formed in two modes: without (mode 1) and with (mode 2) rotation of the substrates in a plasma flow. It was shown that irrespective of the deposition regime, the coatings have a single-phase nanograined (grain size ≤ 20 nm) structure of δ-nitrides TiN, (Ti,Zr)N, and ZrN. It is found out that the coatings deposited in accordance with modes 1 and 2 significantly differ in their microstructure. It is demonstrated that in the case of electrolytic hydrogenation in a physiological saline solution (0.9% NaCl), the barrier properties of the coatings deposited via mode 2 are substantially better than those deposited via mode 1 (irrespective of the chemical coating compositions). In the coatings with a regular columnar structure (mode 1), there is a high concentration of hydrogen homogeneously distributed over the coating thickness. In the coatings formed via mode 2 (without columnar microstructure), a high concentration of hydrogen was observed in the subsurface area only. It is found out that there is no hydrogen diffusion into the substrate of these coating both immediately after hydrogenation and after storing for 430 h at room temperature. It was shown that the highest barrier properties were exhibited by the (Ti,Zr)N coatings with the least correlation of spatial distribution of nanograins and Zr/Ti ≤ 1. The hydrogen absorption in the coating based on zirconium nitride increases by a factor of 2.

STUDY OF VIBRATION PROPERTIES OF CERAMIC-METAL NANOSTRUCTURAL TINCU COATINGS WITH DIFFERENT COPPER CONTENT 7 AND 14 AT. % ON CHROMIUMNICKEL- VANADIUM STEELS

This article studies the vibration properties of chromium-nickel-vanadium steels with ceramic-metal nanostructural coatings TIN-CU with different copper contents of 7 and 14 at. %, and also considers the choice of an alloying element in the form of chromium, nickel, vanadium to increase dissipative properties. The research methodology includes the study of the acoustic and vibration characteristics of the alloys, the mathematical processing of the results. The research results show that the samples under study have higher strength and toughness indicators than their standard counterparts. A high-resolution scanning electron microscope study of the coating structure shows the presence of a nanostructure with layers of different nitride phases noticeably distinguishable in contrast.

Prospective nanostructured coatings for modification of calcium fluoride surfaces

The basic properties of materials can be changed by structuring their volume with various nanoparticles as well as by surface modification. In this study, calcium fluoride (CaF2) is selected as a model matrix for investigating the characteristic surface properties, and its spectral and mechanical properties, as well as the surface wetting of a CaF2 surface modified with carbon nanotubes, are compared with the properties of pure crystals. Laser-oriented deposition and an additional electric field varied in the range of 100–600 V/cm are applied for surface structuring. The experimental results are confirmed by quantum-chemical modeling.

The Influence of a Crystallographically Atypical Pentagonal Nanostructured Coating on the Limiting Stage of Low-Temperature Hydrogen Transport through Pd–Cu Membranes

The Influence of a Crystallographically Atypical Pentagonal Nanostructured Coating on the Limiting Stage of Low-Temperature Hydrogen Transport through Pd–Cu Membranes

Abrasive wear of nanostructured cermet coatings in dry and slurry conditions

Abrasive wear behaviour of WC-Co and Fe/Cu-based nanostructured coatings has been investigated under dry and slurry conditions in this study. The retention of nanostructured coating constituents was confirmed together with the formation of various metallic and ceramic phases. Abrasive wear rate of nanostructured WC-Co coating was one order lower than that of micro-structured coatings in both conditions. Relatively higher abrasion wear resistance of such coatings compare to reference metallic material was because of comparatively smaller debris formation. These debris roll in between the moving surfaces and thus limit the wear of coating materials. Another aspect of higher abrasive wear resistance is homogeneous distribution of hard (WC and Al2O3) particles within relatively soft matrix (Co and FeCu) as revealed by SEM investigation.

Colloidal Lignin Particles and Epoxies for Bio-Based, Durable, and Multiresistant Nanostructured Coatings.

There is a need for safe and sustainable alternatives in the coating industry. Bio-based coatings are interesting in this perspective. Although various oils and waxes have been used as traditional wood coatings, they often lack sufficient durability. Lignin is an abundant natural polyphenol that can be used to cure epoxies, but its poor water solubility has impeded the use of unmodified lignin in coatings in the past. To address this issue, water-dispersible colloidal lignin particles (CLPs) and an epoxy compound, glycerol diglycidyl ether (GDE), were used to prepare multiprotective bio-based surface coatings. With the GDE/CLP ratios of 0.65 and 0.52 g/g, the cured CLP–GDE films became highly resistant to abrasion and heat. When applied as a coating on wooden substrates, the particulate morphology enabled effective protection against water, stains, and sunlight with very thin layers (less than half the weight of commercial coatings) while retaining the wood’s breathability excellently. Optimal hydrophobicity was reached with a coat weight of 6.9 g(CLP)/m2, resulting in water contact angle values of up to 120°. Due to their spherical shape and chemical structure, the CLPs acted as both a hardener and a particulate component in the coating, which removed the need for an underlying binding polymer matrix. Light interferometry measurements showed that while commercial polymeric film-forming coatings smoothened the substrate noticeably, the particulate morphology retained the substrate’s roughness in lightweight coatings, allowing for a high water contact angle. This work presents new strategies for lignin applications in durable particulate coatings and their advantages compared to both currently used synthetic and bio-based coatings.

One-Step Synthesis of Versatile Antimicrobial Nano-Architected Implant Coatings for Hard and Soft Tissue Healing.

Dental implant failure remains a prevalent problem around the globe. The integration of implants at the interface of soft and hard tissues is complex and susceptible to instability and infections. Modifications to the surface of titanium implants have been developed to improve the performance, yet insufficient integration and biofilm formation remain major problems. Introducing nanostructures on the surface to augment the implant-tissue contact holds promise for facilitated implant integration; however, current coating processes are limited in their versatility or costs. We present a highly modular single-step approach to produce multicomponent porous bioactive nanostructured coatings on implants. Inorganic nanoparticle building blocks with complex compositions and architectures are synthesized in situ and deposited on the implants in a single step using scalable liquid-feed flame spray pyrolysis. We present hybrid coatings based on ceria and bioglass, which render the implant surfaces superhydrophilic, promote cell adhesion, and exhibit antimicrobial properties. By modifications to the bioglass/ceria nanohybrid composition and architecture that prevent biomineralization, the coating can instead be tailored toward soft tissue healing. The one-step synthesis of nano-architected tissue-specific coatings has great potential in dental implantology and beyond.

A universal robust bottom-up approach to engineer Greta-oto-inspired anti-reflective structure

The Greta oto butterfly has transparent wings with extraordinary omnidirectional anti-reflection behavior, owing to unusual nanostructures with random height and pitch/space distribution on its wing surface. The beauty and efficacy of such nanostructures are proven designs but difficult to reproduce en masse. Here, we establish a low-cost bottom-up approach by simply stacking monolayer-aligned agitation-assisted deposition of silver nanowire (AgNW) meshes followed by deposition of various overcoats. Such AgNW meshes provide the template to grow nanostructures, imitating those on the Greta oto’s wings that consist of randomly situated nanocones with controllable mean pitches and heights. The resulting nanostructure enhances anti-reflections in both SiO2/AgNW and VO2/AgNW systems, which showed reduced omnidirectional reflectance up to 33% and 70%, respectively. Furthermore, the VO2/AgNW system exhibits enhanced luminous and infrared transmittance without sacrificing solar modulation. Our robust bottom-up approach provides a simpler alternate non-lithographic way to economically produce controlled biomimetic anti-reflective nanostructured coatings.

Self-healing polydimethylsiloxane antifouling coatings based on zwitterionic polyethylenimine-functionalized gallium nanodroplets

There is an urgent need to develop effective and eco-friendly nanostructured coatings for marine antifouling to replace traditional coatings, while ensuring they do not lead to environmental hazards. Gallium-based liquid metal (GLM), which has unique antibacterial and non-toxic properties, has potential for applications in antifouling. In this study, GLM nanodroplets modified with zwitterionic polymer (polyethylenimine-quaternized derivative, PEIS) based antifouling agent were prepared successfully via sonication and Michael-addition, which could potentially be incorporated into the polydimethylsiloxane coating (PDMS) as a functional filler. A series of characterization methods, such as infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, have proved the successful modification of GLM nanodroplets with PEIS. The PEIS functionalized GLM nanodroplets exhibit good anti-bacterial properties due to synergistic bactericidal activity of Ga3+ stemming from GLM nanodroplets and the quaternary ammonium group from zwitterionic polymer PEIS. The synergistic anti-bacterial properties of PEIS-GLM nanodroplets and strong surface hydration of zwitterionic polymer PEIS result in remarkable antifouling performance of the filler. Subsequently, through the observation of the cross section, the as-prepared PEIS modified GLM nanodroplets exhibit good dispersibility in the PDMS coating, which also ensures that the PEIS-GLM@PDMS coating has satisfactory antifouling effect (removal of above 90% bacteria and 70% microalgae). Furthermore, the PEIS modified GLM nanodroplets endow the PDMS coating with self-healing properties by reason of the crosslinking of unreacted vinyl in PDMS by exposed GLM initiating polymerization under external mechanical force.

Bioinspired, Highly Adhesive, Nanostructured Polymeric Coatings for Superhydrophobic Fire-Extinguishing Thermal Insulation Foam.

Lightweight polymeric foam is highly attractive as thermal insulation materials for energy-saving buildings but is plagued by its inherent flammability. Fire-retardant coatings are suggested as an effective means to solve this problem. However, most of the existing fire-retardant coatings suffer from poor interfacial adhesion to polymeric foam during use. In nature, snails and tree frogs exhibit strong adhesion to a variety of surfaces by interfacial hydrogen-bonding and mechanical interlocking, respectively. Inspired by their adhesion mechanisms, we herein rationally design fire-retardant polymeric coatings with phase-separated micro/nanostructures via a facile radical copolymerization of hydroxyethyl acrylate (HEA) and sodium vinylsulfonate (VS). The resultant waterborne poly(VS-co-HEA) copolymers exhibit strong interfacial adhesion to rigid polyurethane (PU) foam and other substrates, better than most of the current adhesives because of the combination of interfacial hydrogen-bonding and mechanical interlocking. Besides a superhydrophobic feature, the poly(VS-co-HEA)-coated PU foam can self-extinguish a flame, exhibiting a desired V-0 rating during vertical burning and low heat and smoke release due to its high charring capability, which is superior to its previous counterparts. Moreover, the foam thermal insulation is well-preserved and agrees well with theoretical calculations. This work offers a facile biomimetic strategy for creating advanced adhesive fire-retardant polymeric coatings for many flammable substrates.

Chitosan and Byrsonima crassifolia-based nanostructured coatings: Characterization and effect on tomato preservation during refrigerated storage

Current concerns about the use of synthetic pesticides for preserving horticultural commodities have triggered the search for environmentally friendly packaging. In this regard, this study evaluated the effect of chitosan nanoparticle and chitosan-Byrsonima crassifolia nanoparticle coatings on the postharvest quality of tomato and on the incidence of Pectobacterium carotovorum after 19 days of storage. Thickness and swelling properties as well as the quality and physiological variables, and antimicrobial activity were determined. From the results, confocal laser scanning micrographs showed the interaction between the tomato and the coating containing the rhodamine-labeled chitosan nanoparticles. Changes in chroma and hue angle values as well as for firmness, with an increase in ascorbic acid content and lower CFU (colony-forming units) for the tomatoes coated with chitosan nanoparticles at a concentration of 30% were observed. The weight loss values were less than 13%. There was a decrease in CO2 and ethylene production at the end of the storage period. Chitosan-based nanostructured coating represents an alternative for preserving tomatoes against P. carotovorum.

Design and Optimization of the Antireflective Coating Properties of Silicon Solar Cells by Using Response Surface Methodology

The design and optimization of a nanostructured antireflective coatings for Si solar cells were performed by using response surface methodology (RSM). RSM was employed to investigate the effect on the overall optical performance of silicon solar cells coated with three different nanoparticle materials of titanium dioxide, aluminum oxide, and zinc oxide nanostructures. Central composite design was used for the optimization of the reflectance process and to study the main effects and interactions between the three process variables: nanomaterial type, the radius of nanoparticles, and wavelength of visible light. In this theoretical study, COMSOL Multiphysics was utilized to design the structures by using the wave optics module. The optical properties of the solar cell’s substrate and the three different nanomaterial types were studied. The results indicated that ZnO nanoparticles were the best antireflective coating candidate for Si, as the ZnO nanoparticles produced the lowest reflection values among the three nanomaterial types. The study reveals that the optimum conditions to reach minimum surface reflections for silicon solar cell were established by using ZnO nanoparticles with a radius of ~38 nm. On average, the reflectance reached ~5.5% along the visible spectral range, and approximately zero reflectance in the 550–600 nm range.

Few-layer graphene on nickel enabled sustainable dropwise condensation

Condensation is critical for a wide range of applications such as electrical power generation, distillation, natural gas processing, dehumidification and water harvest, and thermal management. Compared with “filmwise” mode of condensation (FWC) prevailing in industrial-scale systems, dropwise condensation (DWC) can provide an order of magnitude higher heat transfer rate owing to drastically reduced thermal resistance from the formation of discrete and mobile droplets. In the past, promoting DWC by controlling surface wetting has attracted wide attention, but DWC highly relies on non-wetting surfaces and only lasts days under practical conditions due to the poor reliability of coatings. Here, we developed nanostructured graphene coatings on nickel (Ni) substrates that we can control and enhance the nucleation of water droplets on graphene grain boundaries. Surprisingly, this enables DWC even under normal “wetting” conditions. This is contradictory to the widely accepted DWC mechanism. Moreover, the Ni-graphene surface enables exceptional long-term condensation from days to more than 3 years under practical or even more aggressive testing environments.

Improving the Corrosion Resistance of Carbon Steel by Ni–P Nano-Structured Coating

Improving the Corrosion Resistance of Carbon Steel by Ni–P Nano-Structured Coating

Impact of deposition conditions on nanostructured anisotropic silica thin films in multilayer interference coatings

Recent developments of nanostructured coatings have reached a point where extensive investigations within multi-layer systems are necessary for further implementation in novel photonic systems. Although sculptured thin films are explored for decades, no optical and structural measurements have been performed for anisotropic nanostructured multi-layer coatings with different deposition conditions of the dense layer. In this paper, we present extensive morphological analysis on silica nanostructured anisotropic films. Changing the deposition angle from 66° to 84°, indicate the changes in surface filling from 84% to 57%, respectively, while phase retardance has a maximal value of 0.032°/nm at 70° and 72° angles. We also present the investigation of covering such structures with the dense layer at different conditions. As a result, the technology for maintaining initial anisotropic properties is developed for extending spectral difference 1.6 times and phase retardation by 5% in anisotropic multi-layer coatings. Furthermore, we present simulations of growing silica layer using experimental conditions in the Virtual Coater framework resulting in virtual anisotropic films for comparison with measurements. The minimal impact on the anisotropy of porous layer is reached with the deposition of dense layer at 30° angle during constant substrate rotation.

The defining role of ultrasonic on the relaxed GBs and superior thermal stability of copper coatings

The nanostructured Cu coatings were electrodeposited with different vibration, such as vibration-free, agitation and ultrasonic.Ultrasonic could help to refine grains and optimize the comprehensive performance of the coating. The effect of vibration on the thermal stability of pure Cu coatings was investigated with the coatings annealing at 450 °C, 500 °C and 550 °C. Both agitation and ultrasonic can suppress the nanograins coarsening and the effect of ultrasonic was more excellent. Ultrasonic can not only increase the content of nanotwins and triple junctions but also induce the relaxation of GBs. Therefore, the ultrasonic deposited nanograins in the low-energy state exhibit superior thermal stability. The mechanisms of the thermal stability in the electrodeposited coatings were studied from thermodynamics and dynamics. By comparing dislocation density, stacking faults energy and grain boundaries energy, it was proved that the driving force of grain growth in the ultrasonic deposited coating was lowest. Both the methods of isothermal measurements and Kissinger showed that the ultrasonic could increase the activation energy of grain growth to inhibit grain boundary mobility.

Bio-based polyurethane nanocomposite thin coatings from two comparable POSS with eight same vertex groups for controlled release urea

Nanocomposite modification has attracted much attention in improving properties of bio-based polymer coating material for coated fertilizer. Herein two comparable polyhedral oligomeric silsesquioxanes (POSS), with eight poly(ethylene glycol) (PEG) and octaphenyl groups attached to the cage, respectively, were successfully incorporated into thin castor oil-based polyurethane coatings via in-situ polymerization on the urea surface. The nanostructure coatings are environmentally friendly, easy to prepare, and property-tunable. The results show that the vertex group of POSS had a pronounced influence on dispersion level and interaction between polyurethane and POSS that well-tuned the release pattern and period of coated urea, even at the coating rate as low as of 2 wt%. The liquid POSS with long and flexible PEG groups had better compatibility and dispersibility in polyurethane matrix than the solid POSS with rigid octaphenyl groups, as evidenced by SEM/EDS. The unique properties were resulted from the different extents of physical crosslinkings. This modification of bio-based polyurethane coating with POSS provided an alternative method of regulating and controlling the properties of coated fertilizer.

Antibacterial Surfaces, Thin Films, and Nanostructured Coatings

Antibacterial surfaces can play a key role in a great number of everyday applications, spanning from biomedical purposes (medical devices, protection equipment, surgery tools, human implants, etc [...]

Photocatalytic TiO2-based coatings for environmental applications

This review intends to provide a representative survey of nanostructured TiO2 coatings obtained by means of different deposition techniques, either starting from pre-formed TiO2 based nanostructures or directly synthetizing the nanostructured photocatalysts in situ on a surface, from suitable precursors. In particular, some among the most recent reports regarding a range of conventional as well as emergent techniques to obtain nanostructured TiO2 based coatings, are presented, discussing their characteristics and advantages, in the light of the experimental conditions and the supporting substrates. Selected examples of commercially available nanostructured TiO2 based products and real applications of nanostructured TiO2 based coatings for water and air remediation, self-cleaning, cultural heritage protection and bactericidal inactivation are described, including a very topical example of microbial inactivation represented by a TiO2 nanostructured coating against the spreading of SARS-CoV-2 on surfaces. Overall, the current coating technologies seems to be mature enough to hold a significant promise in view of the real scale applications of nanostructured TiO2 in environmental field.

Dense nanostructured YSZ coating prepared by low-pressure suspension plasma spraying: Atmosphere control and deposition mechanism

Suspension plasma spraying (SPS) has attracted more and more attention in terms of the preparation of nanostructured ceramic coatings. However, due to the low mass of the nanopowder , it is challenging to prepare high-density coatings through SPS, and this largely limits its application in the areas such as electrolytes of solid oxides fuel cell (SOFC) and environmental barrier coatings. In this article, a novel suspension spraying technology – low-pressure suspension plasma spraying (LPSPS) – was used to prepare a high-density, nanostructured coating. The results revealed that the environment atmosphere (inert atmosphere versus oxidative atmosphere) played a critical role in the microstructure of the coating. The deposition mechanisms of the coatings in both atmospheres were proposed, and a high-density nanostructured yttria-stabilized zirconia (YSZ) coating was successfully prepared by atmosphere control, based on these deposition mechanisms. • A novel suspension spraying technique—low-pressure suspension plasma spraying was used to prepare dense nanostructured YSZ coating. • In the inert atmosphere, a number of carbons were produced in the plasma jet due to the ethanol pyrolysis, resulting in poor adhesion and mechanical properties of the coating • In the oxidative atmosphere, due to ethanol combustion, the plasma jet exhibited a better heating capacity for powders, resulting in improved quality of the coating. • A high-density YSZ coating was successfully prepared with a high-enthalpy plasma jet in the oxidative atmosphere