As-prepared Coatings Research Articles

Facile and effective construction of superhydrophobic, multi-functional and durable coatings on steel structure

Nowadays, steel is one of the most significant materials in industry and daily life. Unfortunately, the defects of steel structures such as collapse at high temperature, poor corrosion resistance, and bad surface functionality have severely restricted their further application. Applying functional coatings for steel structures is considered the effective strategy for settling theses disadvantages. Inspired by nature, eco-friendly, superhydrophobic, and multifunctional-integrated coatings were fabricated on steel via one-step spraying strategy in this paper. Along with silicon dioxide (SiO2) nanoparticles and epoxy resin/silicone resin (EP/SR), the coatings are jointly constituted by hydrophobic flame retardants (M-ALHP@ZIF-8) prepared via multi-stage modification. Due to the formation of micro/nano-scaled rough structure with low surface energy, the water contact angle (WCA) and water sliding angle (WSA) of as-prepared coatings can reach 162.4° ± 1.2° and 2.8° ± 0.4°. The water repellency with low water adhesion can endow the surface of steel with excellent self-cleaning, anti-fouling, and long-lasting anti-corrosion ability. Additionally, the superhydrophobic coatings have displayed good mechanical robustness, chemical stability and weather resistance, which can exhibit certain actual values. Accorded with Zn-catalyzed charring effect of flame retardants, as-prepared coatings have possessed outstanding fire protection capacity with the lowest backside temperature of 181 °C after 1 h fire impact tests. Consequently, this work has provided a facile and effective route for synchronously tackling the key challenges of poor fire protection and surface functionality for steel structures, which will be expected to pave the wide pathway for constructing multifunctional coatings in more fields.

Facile and fast construction of biomimetic, waterborne, and superhydrophobic coatings via spraying strategy

Typically, the preparation of superhydrophobic coatings may release a large amount of volatile organic compounds (VOCs), which will be potentially harmful to the environment. In this condition, waterborne coatings have gradually become the main method to replace the traditional organic solvent-based coatings in recent years. Inspired by natural superhydrophobic phenomena, biomimetic, waterborne, and superhydrophobic coatings with multi-functional integration have been prepared via a one-step pneumatic spraying technique in this paper. The coatings were mainly composed of solvent (water), low surface energy substances (polytetrafluoroethylene emulsion (PTFE)), binding agents (waterborne silicone resin (WSR)), rough structure maker (polyphenylene sulfide (PPS) and graphene powder (GP)), and filler dispersion agent (dodecyl phenyl polyoxyethylene (OP-10)). Owing to the formation of hierarchical micro/nano-scaled structure covered with low surface energy, the water contact angle (WCA) and water sliding angle (WSA) values of as-prepared coatings can reach 155.5° ± 1.1° and 9.2° ± 0.3°, respectively. This is feasible for endowing the coatings with rich surface functionalities such as self-cleaning properties, anti-icing ability, anti-corrosion properties, and oil-water separation. Furthermore, the adequate durability and stability of as-prepared coatings have been confirmed by a series of mechanical and chemical damage tests. The super-hydrophobicity can be retained even after 12 m sandpaper abrasion, 24 h continuous UV irradiation and acid/alkali immersion tests. Thus, this article has provided an effective and simplified strategy for preparing multifunction-integrated and waterborne superhydrophobic coatings, which will extend its potential application in many daily life and industrial fields.

One-Step Spraying Strategy for Fabricating Bioinspired, Graphene-Based, and Multifunctional-Integrated Coatings on Structural Steel with Good Water Repellency, Fireproofing, Anticorrosion, and Durability.

Traditionally, many coatings were merely concentrated on settling the inherent fire protection problem of steel structures, while surface contamination and corrosion susceptibility should also be considered. Concurrently addressing these problems in fireproof efficiency and surface multifunctionality has become an issue of great significance in further expanding the application value in industrial and daily scenarios. Based on this condition, ecofriendly, graphene-based, and superhydrophobic coatings with multifunctional integration were constructed on steel via a one-step spraying method. The as-prepared coatings mainly consist of epoxy resin (EP), silicone resin (SR), a cyclodextrin-based flame retardant (MCDPM), expandable graphite (EG), and multilayered graphene (MG). The results demonstrate that the water contact angle (WCA) and water sliding angle (WSA) of as-prepared coatings can reach 156.8 ± 1.6 and 5.8 ± 0.7°, respectively, revealing good water repellency and self-cleaning properties. The coatings can also exhibit adequate adaptability for various substrates including wood, polyurethane foam, and cotton fabrics. Besides, good durability and robustness of coatings have been also verified via acid/alkali immersion, outdoor exposure, O2/plasma etching, and linear abrasion tests. Simultaneously, the coatings can exhibit excellent anticorrosion capacity for steel materials via a double barrier effect. Most importantly, the coatings have exhibited the lowest backside temperature (234.5 °C) during fire impact tests, suggesting excellent fireproof and heat insulation performance. This fact can be ascribed to the conjunct action between the physical/chemical charring process of flame retardants and the remarkable thermal stability of graphene. Consequently, this article can be expected to further promote the development and application of multifunctional-integrated coatings for steel structures in more fields.

Biomimetic Slippery Surface with Exclusive Liquid-Repellent and Self-Cleaning Properties for Antifouling.

The nature always offers amazing inspiration, where it is highly desirable to endow coatings on marine equipment with powerful functions. An excellent example is slippery zone of Nepenthes pitcher, which possesses novel liquid-repellent and self-cleaning performance. Therefore, this study presents an efficient fabrication method to prepare a novel coating. The coatings were fabricated by designing biomimetic textures extracted from the lunate bodies of slippery zone on polydimethylsiloxane (PDMS) and then grafting Dictyophora indusiata polysaccharide (DIP) modifier. The as-prepared slippery coatings exhibited outstanding antifouling properties against kinds of daily life pollutants such as Chlorella and coffee. This synergistic strategy was proposed combined with environmentally friendly modifier grafting and heterogeneous microstructure on the surface to broaden new probabilities for manufacturing slippery coatings with incredible protective functionality.

Green and Heavy-Duty Anticorrosion Coatings: Waterborne Epoxy Thermoset Composites Modified through Variation of Zinc Dust Loading and Incorporation of Amine-Capped Aniline Trimer and Graphene Oxide.

In this study, an array of environmentally friendly and heavy-duty anticorrosion composite coatings were prepared. The synthesis involved amine-capped aniline trimer (ACAT) produced by an oxidative coupling reaction and graphene oxide (GO) prepared based on Hummer's method, and later, the waterborne epoxy thermoset composite (WETC) coatings were prepared by thermal ring-opening polymerization of EP 147w, a commercial waterborne epoxy resin, in the presence of ACAT and/or GO with zinc dust (ZD). A synergistic effect was observed by replacing a significant amount of the ZD loading in the WETC by simultaneously incorporating a small amount of ACAT and GO. The electrochemical corrosion measurements of the as-prepared WETC coatings indicated that incorporating 5% w/w ACAT or 0.5% w/w GO separately replaced approximately 30% w/w or 15% w/w of the ZD, respectively. Moreover, the WETC coatings containing 5% w/w ACAT and 0.5% w/w GO simultaneously were found to replace 45% w/w of the ZD. A salt spray test based on ASTM B-117 also showed a consistent trend with the electrochemical results. Incorporating small amounts of ACAT and GO in WETC coatings instead of ZD not only maintains the anticorrosion performance but also enhances adhesion and abrasion resistance, as demonstrated by the adhesion and abrasion tests.

Differences among SiO2, TiO2, and Ti in the anti-foaming mechanism of chemically bonded silicate coatings

Potassium silicate coating foams seriously at high temperature. SiO2, TiO2 and Ti particles were added to solve this problem. Micro-morphologies, phase composition, mass change kinetics were analyzed, porosity and volatilizable water contents (κ0) of coatings were calculated to reveal the effects of adding SiO2, TiO2, and Ti particles on the foaming behavior of potassium silicate coatings at 500 °C. The higher the κ0, the more severe the foaming becomes. Results shows that addition of fillers improved the anti-foaming resistance due to volume occupier effect. Among them, SiO2 particles did not alter κ0 of the as-prepared coatings due to similar tetrahedral structure with silica, addition of TiO2 particles increased κ0 because titania can form more -Ti-OH groups than silica, Ti particles decrease κ0 because dissolved Ti4+ ions can decrease the number of the pending -Si-OH bonds. Combined with the volume expansion occurred due to the oxidation of Ti particles during heat treatment, potassium silicate coating modified by 30 wt% Ti exhibited the best anti-foaming performance with the lowest porosity, at 1.8%.

Biomimetic construction of green, fire-proof and super-hydrophobic multifunctionality-integrated coatings via one-step spraying method for steel structures

Recently, the exposed shortcomings of steel structures containing collapse at high temperature, severe corrosion phenomenon and susceptibility to pollution have gradually restricted their widespread applications in the significant fields of national economy. Aimed at overcoming these crucial problems, this paper was inspired by the superhydrophobic phenomenon on the surface of lotus leaves that the environmental and multifunction-integrated coatings with concave-convex scale-like micro-nanostructures were fabricated via one-step spraying method. Among the chemical composition of coatings, epoxy resin (EP) and silicone resin (SR) can act as the composite binders with good adhesion and hydrophobicity for attaching the fillers to the substrates. And the fillers composed of cyclodextrin-based flame retardant (MCDPM) and expandable graphite (EG) will exert the bidirectional action in fabricating the rough surface microstructure and enhancing the fire resistance of coatings. The results have revealed that as-prepared coatings exhibit low-adhesion super-hydrophobicity with the water contact angle (WCA) of 153.9° and the water sliding angle (WSA) of 8° that will induce a series of excellent performance in self-cleaning and corrosion resistance. In addition, good chemical stability and environmental durability have been simultaneously achieved for superhydrophobic coatings. Most of all, the exceptional fire protection ability of the designed coatings has been verified. Accompanied by the advanced formation of dense, continuous and high-yield char layers, the backside temperature of coated steel plate has been reduced to 269 °C during 1 h fire burning tests, which is far less than the critical collapse temperature of bare steel structure. Accordingly, compared to EP/SR coatings, the peak heat release rate (PHRR) and total heat release rate (THR) of the EP/SR-3 coatings are decreased by 68.8% and 96.6%, interpreting the intensified fire safety of coated steel structure. And the potential condensed flame-retardant mechanism has been further inferred and illustrated by systematically analyzing the combustion residue. Consequently, this paper has explored a straightforward route to address the issues of multiple defects for steel structures that extend the in-depth application in real-world fields.

Facile fabrication of titanium atomic modification polyimide‑silicone coatings via moisture/thermal dual curing for high temperature protection

The development of coatings with high thermal resistance and strong adhesion is desirable and challenging. Herein, we firstly reported a novel bismaleimide silicone (PMI-HSi) oligomer as well as the matching titanium-containing phthalate curing agent (PAEs). Subsequently, PMI-HSi and PAEs are semi-cured by a de-ethanolization reaction in humid ambient atmosphere. Resultant prepolymer molecular skeletons comprise acylimine bonds yielding strong hydrogen bonds, benzene rings, and titanium atoms, which facilitates the stability of the prepared coatings in high-temperature conditions. Ultimately, the final coating was successfully obtained via thermal initiated radical polymerization. The DTG results indicated that the residual carbon content of PMI-HSi@PAEs50% is as high as 63.9 %. And the Td5%, Td30% and THRI of PMI-HSi@PAEs50% were separately increased by 142.2 %, 29.2 % and 47.9 % compared with the control group. It is worth noting that PMI-HSi@PAEs50% can remain stable at a high temperature up to 600 °C, and no color changes and cracks appeared on the coating surface. All these results indicate that the as-prepared coatings exhibited excellent high temperature stability. In addition, due to the introduction of PAEs, the adhesion of PMI-HSi@PAEs50% reaches the highest grade of 0 and the hardness reaches 5H. Meanwhile, the reinforcement mechanisms were elucidated in detail. Overall, the as-prepared coating possesses high temperature resistance, strong adhesion, and great hardness, which possesses enormous potential for applications in the field of high-temperature protection.

Assessing the wear properties of plasma electrolytic oxidation TiO2 coatings incorporated ZrO2 nanoparticles on Cp-Ti in simulated body fluid

TiO2 oxide coatings incorporated ZrO2 nanoparticles were prepared on Cp-Ti using the plasma electrolytic oxidation (PEO) process in electrolyte solutions containing dispersed ZrO2 nanoparticles. The coatings’ microstructure, roughness, and composition were characterized using scanning electron microscopy (SEM), roughness profilometry, and X-ray diffractometry (XRD) analyses, respectively. The coatings’ friction and wear characteristics were examined using a ball-on-disk sliding test in a simulated body fluid (SBF) electrolyte. The as-prepared oxide coatings had a rough and porous surface structure, primarily consisting of rutile and/or anatase TiO2, tetragonal ZrO2, and ZrTiO4. ZrO2 nanoparticles were incorporated into the TiO2 coating layers and were found on the surface or in the pores. The wear and friction behavior of the oxide coatings were influenced by the quantity of ZrO2 nanoparticles (1 g/L, 3 g/L, and 5 g/L) in the electrolyte solution. The wear resistance of coatings improved by decreasing the wear rate by about 8 % (from 2.31 × 10−6 mm3/Nm to 2.11 × 10−6 mm3/Nm) when the ZrO2 nanoparticles concentration in the electrolyte solution rose from 1 g/L to 5 g/L, because of the formation of more of harder ZrO2 and ZrTiO4 phases in the coatings.

An ultra-thin nickel electrodeposited stainless steel mesh with superhydrophobic property and high mechanical durability for oil-water separation

Oil pollution has a detrimental impact on our water environment. Therefore, developing a durable and high-flux material for separating oil-water mixture is highly desirable. In this study, we present an innovative approach to prepare superhydrophobic-superoleophilic nickel palmitate stainless steel meshes (SNP-SSM) using a one-step electrodeposition method. This method not only creates rough hierarchical micro/nanostructures on the SSM but also reduces the surface free energy of the SSM. The SNP-SSM demonstrates a water contact angle (CA) of 164.98 ± 2.3° and a roll-off angle (ROA) of 4.78 ± 1.3°, enabling effective, long-term separation of oil-water mixtures by gravity. The oil-water separation efficiency (n-hexadecane/water) reaches 98.3%. Furthermore, in various tests, including knife scratching, tape peeling, sandpaper abrasion, bending, heating, and immersion in various liquids, the SNP-SSM exhibits sufficient mechanical, chemical, and thermodynamic robustness, making it suitable for harsh conditions, the as-prepared coatings effectively inhibited the corrosion of the meshes. This study paves the way for advancing technology in challenging oil-water separation scenarios, encompassing mechanical friction, chemical processes, and high-temperature conditions.

Preparation and Properties of PDMS Surface Coating for Ultra-Low Friction Characteristics.

Polydimethylsiloxane (PDMS) has excellent physical-chemical properties and good biocompatibility. Thus, PDMS has been widely applied in biomedical applications. However, the low surface free energy and surface hydrophobicity of PDMS can easily lead to adverse symptoms, such as tissue damage and ulceration, during medical treatment. Therefore, the construction of a hydrophilic low-friction surface on the PDMS surface could be helpful for alleviating patient discomfort and would be of great significance for broadening the application of PDMS in the field of interventional medical catheters. Existing surface modification methods such as hydrogel coatings and chemical grafting suffer from several deficiencies including uncontrollable thickness, surface fragility, and low surface strength. In this study, a hydrophilic surface with ultra-low friction properties was prepared on the surface of PDMS by an ultraviolet light (UV) curing method. The monomer acrylamide (AM) was induced by a photoinitiator to form a coating on the surface of the silicone rubber by in situ polymerization. The surface roughness of the as-prepared coatings was regulated by adding different concentrations of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the monomer solution, and the coating properties were systematically characterized. The results indicated that the roughness and thickness of the as-prepared coatings decreased with increasing AMPS concentration and the as-prepared coatings had good hydrophilicity and low-friction properties. The Coefficient of Friction (CoF) was as low as 0.0075 in the deionized water solution, which was 99.7% lower than that of the unmodified PDMS surface. Moreover, the coating with a lower surface roughness exhibited better low-friction properties. The results reported herein provide new insight into the preparation of hydrophilic, low-friction coatings on polymer surfaces.

A novel sustainable phosphorus-containing heteroatom-based coating for polyamide 6.6 textiles: Enhanced flame retardancy and hydrophilicity

The demand for "green" materials increases due to concerns about the effects of flame-retardant textiles. Using natural plant-base compounds such as phytic acid (PA) and the most abundant green amino polysaccharide chitosan (CS) as effective and durable flame retardants for textiles is essential for creating sustainable and ecological textile products. This study aims to develop a novel, eco-friendly, phosphorus- and nitrogen-containing flame retardant known as ammonium phytate (AP), intending to improve the flame retardant properties of polyamide 6.6 (PA6.6) textiles. UV-induced grafting with 2-acrylamide-2-methylpropane sulfonic acid (AMPS) increases the surface functional groups of PA6.6 fabrics. Later, the surface-modified fabrics were coated with phosphorus-containing heteroatom-based components, namely, sulfur, nitrogen, silicon, and boron, onto a single flame retardant system via layer-by-layer (LBL) deposition of positively charged chitosan/boron drop (3-aminopropyl) triethoxysilane/silicon dioxide (CS/BAPTES/SiO2) sole solution and negatively charged AP solution to enhance superior hydrophilic and durable flame retardant performance. According to the data, a weight pick-up of 56.5% is attributable to only 4 BLs. However, all the flame-retardant-coated fabrics can completely stop the melting-dripping tendency and achieve B-3 to B-2 ratings after the UL-94 vertical burning test. In addition, the LOI values of treated fabrics increase from 18.5% to 23.5% compared to a pure sample. The AMPS grafted with a 4BL-deposited fabric sample exhibits a maximum decrease in peak heat release rate (PHRR) of more than 54%. Moreover, the thermogravimetric analysis (TGA) test reveals a significant increase in thermal stability and char yield. Additionally, the as-prepared phosphorus-containing heteroatom-based coatings impart a water contact angle value of approximately 0⁰ within 2 s, demonstrating that the treated fabrics exhibit superior hydrophilic performance. Moreover, using AMPS-grafted and only 2-BL-deposited treatments improves coating stability in washing and imparts durable flame retardancy that can resist up to 20 washing cycles. It is proposed that the sustainable phosphorus-containing heteroatom-based coating may be a potentially effective replacement for existing durable flame retardants routinely used in textile finishing operations.

Sr-doped LaFeO3 thin coatings for protection of ferritic stainless steel interconnects in solid oxide cells: A study on Cr-barrier and electrical properties

A high-temperature conversion process in molten carbonate baths was applied to produce thin Sr-doped LaFeO3 perovskite coatings on the surface of a K41 steel for interconnect applications in Solid Oxide Cells. Two conversion coatings with identical structure and phase composition, but slightly different thickness were produced in nitrate-accelerated baths containing the nitrate additive at two concentration levels. The as-prepared coatings consisted of a dual-layered perovskite-spinel structure with a top sub-micrometric Sr-doped LaFeO3 layer grown onto a micron-range thick inner Fe-Cr spinel oxide layer. Both coatings showed high protection against oxidation and chromia scale formation at 700°C. Further, excellent Area Specific Resistance (ASR) behavior was found for both coatings at 700°C, although an optimal balance of ASR and Cr-diffusion barrier properties was achieved with the coating produced in the lower nitrate content bath (N-02 coating). The causes for the enhanced barrier properties of the N-02 coating were ascribed not to a different coating thickness, but rather to the evolution of the pristine dual-layer into a more impervious three-layer structure during oxidation aging at 700°C. The evolved structure was formed by decomposition of the pristine sub-coating Fe-Cr spinel into two new spinel sublayers: an outer ferrite and an inner chromite layer, whereas the top thin-film perovskite layer remained essentially unaltered. Partial change in the Fe oxidation state and other possible causes involved in the observed decomposition of the pristine Fe-Cr spinel layer during the thermal aging are analyzed and discussed. Measurements of ASR activation energy indicated that the contact resistance behavior of the thin perovskite coatings was dominated by the internal spinel layer conductivity.

In Situ Growth of High-Performance ZnAl-Layered Double Hydroxides/Al2O3 Composite Coatings on Aluminum Alloy

In this research, high-performance ZnAl-layered double hydroxides (ZnAl-LDHs) with different Zn2+ concentrations were prepared on the surface of an anodized 1060 aluminum alloy using the in situ growth method, and the influence of Zn2+ concentration on corrosion resistance and tribological behavior was further explored. The surface morphology, element distribution, phase composition, and mechanical performance of ZnAl-LDHs/anodic aluminum oxide (AAO) composite coatings were tested and analyzed. Subsequently, the investigation of the anti-corrosion properties and tribological behavior of as-prepared composite coatings and AAO were conducted experimentally. The results show that with the increase in Zn2+ concentration, the thickness and bonding strength of the coatings gradually increase, and the hardness progressively decreases. The ZnAl-LDHs/AAO composite coating with a Zn2+ concentration of 0.3 mol/L exhibits the best anti-corrosion ability, which has the minimum corrosion current density of 2.435 × 10−9 A/cm2. This can be attributed to the uniform and compact ZnAl-LDH films where the porous structure of the AAO is well sealed. Moreover, the excellent friction-reduction and anti-wear properties of ZnAl-LDHs/AAO composite coatings with larger Zn2+ concentrations are verified using a ball-on-disc rotating wear tester under dry wear. A reasonable mechanism for improving tribological properties of resulting ZnAl-LDHs/AAO composite coatings is proposed.

One-step spraying route to construct a bio-inspired, robust, multi-functional and superhydrophobic coatings with corrosion resistance, self-cleaning and anti-icing properties

Aimed at getting rid of the complicated preparation procedure, multi-functional superhydrophobic coatings inspired by natural plants have been successfully constructed on different matrix via a facile and effective spraying technology in this paper. The innovation of this paper lies in directly employing the unmodified fillers to establish the superhydrophobic coatings system with high performance. The results have revealed that the water contact angle (WCA) and water sliding angle (WSA) of as-prepared coatings can reach 155.4° and 8°, confirming the superhydrophobicity with low surface adhesion is achieved. And the potential superhydrophobic mechanism can be ascribed to the enrichment of low surface energy components on the homogeneous and rough grain structure of as-prepared coatings. Simultaneously, as-prepared coatings have exhibited the good self-cleaning property, anti-fouling property, and anti-icing property. Surprisingly, the mechanical stability of superhydrophobic coatings can be maintained after 50 cycles during the friction experiments. And the oil-water separation ability for the coated metal meshes was also obtained with high separation efficiency of 95%. Moreover, the anti-corrosion ability was also systematically investigated and its potential anti-corrosion mechanism of superhydrophobic coatings is primarily deduced. Therefore, the multifunctional and robust superhydrophobic coatings with biomimetic structure were established via a simple strategy, which is expected to be applied in field of metal corrosion and protection and multi-functional surface material in the future.

Novel attempts for the assembly of tannic-based coatings in ethanol media

Tannic acid (TA) based coatings possessed attracted significant increasing attention in super extensive applications. An anhydrous and predictable TA-based coating synthesis process is desirable. The objective of this study was to develop a new method to fabricate TA-based coating in absolute alcohol. TA polymerization (pTA) caotings with modification efficiency up to 22.69% were synthesized by mixing TA and sodium ethoxide in absolute alcohol under various reaction times. Moreover, the anhydrous method also applicable to synthesis process of metal-TA (M−TA) coatings generated by chelation between TA and metal ions during self-assembly process. A series of M−TA using Ce and Cu as model were synthesized under different metal ions feeding ratios. The as-prepared TA coatings exhibited good waterproof and cation dye adsorption capabilities.

Enhancing corrosion resistance of the CaCO3/MgO coating via ultrasound-assisted chemical conversion with addition of ethylenediamine tetra-acetic acid (EDTA) on AZ41 Mg alloy

In order to enhance the corrosion resistance of the AZ41 Mg alloy used as concrete formwork, a bilayer CaCO3/MgO coating was fabricated on the surface of AZ41 Mg alloy with addition of Ca-EDTA in the chemical conversion solutions. Effect of different Ca-EDTA concentrations on the surface morphology of as-prepared CaCO3/MgO coating and corrosion resistance in simulated concrete pore solutions with 3.5 wt% NaCl were investigated. SEM, XPS and XRD were combined to investigate the morphology and composition of the coatings. Electrochemical methods and immersion tests were used to assess the anticorrosion performance of the as-prepared coatings. Results show that an integrated bilayer CaCO3/MgO coating can be prepared on AZ41 Mg alloy by the addition of Ca-EDTA. Electrochemical tests reveal that the CaCO3/MgO coating prepared at 0.01 M Ca-EDTA possesses the best corrosion resistance at varying concentrations of Ca-EDTA. Ca-EDTA accelerates the release of Mg2+ and further affects both nucleation and growth of CaCO3 particles. Appropriate addition of Ca-EDTA can simultaneously preserve the stability of CaCO3 and enhance coating density.

Construction of Cr coatings with different columnar structure on Zircaloy-4 alloys to optimize the high-temperature steam oxidation behavior for accident tolerant fuel claddings

To optimize the oxidation behavior of chromium-coated Zircaloy-4 alloys under 1200 °C high-temperature steam for accident tolerant fuel (ATF) claddings, Cr coatings with different columnar structure are constructed by changing bias voltage using high power impulse magnetron sputtering and corresponding microstructure, mechanical and high-temperature steam oxidation properties are studied systematically. With the bias voltage increase from 0 V to − 150 V, the microstructure of Cr coatings changes from porous columnar structure to compact columnar structure. Especial for bias voltage is − 90 V, the tiny compact grains uniform distribute on the surface micrographs and optimal compact columnar structure are observed on the cross-section micrographs. The hardness and elastic modulus of as-prepared Cr coatings increase firstly and then decrease, the hardness of Cr coatings with optimal compact columnar structure is 8.65 GPa, which is elevated ∼2.28 times than Cr coatings with porous columnar structure. 1200 °C high-temperature steam oxidation test results show an interesting phenomenon that the thickness of Cr layer reduces initial and then increase with the exposure time prolong from 1 h to 4 h. The main steam oxidation mechanism, in the early oxidation stage, is formation the compact Cr2O3 oxide layer. Then, with the exposure time extend, the reduction reaction plays the significant part for steam oxidation mechanism, which is consumption of outmost Cr2O3 oxide layer and formation of subsurface Cr layer. The construction of Cr coatings with compact columnar structure and relevant oxidation mechanism are expected to offer a new idea for improving 1200 °C steam oxidation resistance of chromium-coated Zircaloy-4 alloys.

Cellulose Nanocrystals Chiral Nematic Coating with Reversible Multiple-Stimuli-Responsive Coloration

Due to their unique chiral nematic structure and special optical property, cellulose nanocrystals (CNCs) have drawn enormous attention. However, the inherent brittleness and rigidity limit their application in coatings or free-standing films. In this work, we designed and fabricated a novel iridescent coating with multiple-stimuli-responsive coloration through photochemical cross-linking with CNCs, poly(ethylene glycol) diacrylate (PEGDA), and erythritol. The as-prepared coatings exhibited improved mechanical strength because of the introduction of covalent organic frameworks and the internal hydrogen-bonding interaction of CNCs, cross-linked PEGDA networks, and erythritol that provided efficient energy dissipation. Interestingly, the CNC coating was able to distinguish similar organic liquids, including the skeletal isomers (1-propanol/2-propanol), halogenated hydrocarbons (chloroform/dichloromethane), and homologous compounds (methanol/ethanol), quickly by the change in surface color when immersed in various organic solvents. In addition, the CNC coating exhibited reversible humidity sensitivity with wide color changes from cyan to yellow-green, salmon pink, red, and colorless under 30–98% air relative humidity (RH). Based on the reversible discoloration of CNC coating, the anti-counterfeiting performance on CNC coating was presented, and the handwriting of saline solution appeared reversibly when stimulated with ethanol. Thus, the reversible allochroic CNC-based coating platform with multiple-stimuli-responsiveness has the potential to be developed as solvent sensors, test papers, and encryption tools.

Design of highly anti-corrosive electroless plated Ni–P/modified halloysite nanotubes nanocomposite coating

Halloysite nanotubes (HNTs) and their modifications with either NH2 (HNT-NH2) or NH2/Polypyrrole (HNT–NH2–PPy) were electroless-deposited into the NiP matrix for the first time to form NiP/HNT, NiP/HNT-NH2 and NiP/HNT–NH2–PPy nanocomposite coatings. The as-prepared nanocomposite coatings were heat-treated at 400 °C for 1 h. The transformation in microstructure, nanoindentation, Vicker's micro-hardness, surface morphology, and anti-corrosive properties of all prepared composite coatings were compared to the HNT-free (NiP) coating. Incorporating HNTs in the NiP coating made an appreciable enhancement in the hardness and corrosion resistance. Using the electrochemical impedance spectroscopy technique (EIS), the NiP/HNT-NH2 and NiP/HNT–NH2–PPy coatings showed more significant levels of enhancement in anticorrosion performance, offering about 16.5% and 25.4%, respectively, an increase in the inhibition efficiency of unmodified one (NiP/HNT), reached to 73 and 82%. Moreover, the modified HNT coatings revealed slightly high levels of betterment in microhardness, about 9% and 5.4% for HNT modification with NH2 and NH2-PPy, respectively. In addition, the heat treatment extra improved the hardness and the corrosion resistance of all HNTs nanocomposite coatings compared to HNT-free coating. Furthermore, the heat-treated NiP/HNT has the highest protection efficiency reached to about 95%, based on the polarization measurements. This momentous improvement in the hardness and electrochemical properties reflects the effect of adding the pristine and the modified HNTs into the NiP matrix, resulting in the development of high-performance NiP/HNT-NH2 and NiP/HNT–NH2–PPy composite coatings facilitating their use in various industries.