Composite Coatings Research Articles

Research on cobalt-molybdic sulfide composite coatings deposited by magnetic jet electrodeposition under different magnetic field intensities

Co-MoS2 composite coatings were deposited by the magnetic jet electrodeposition under different magnetic field intensities. The growth orientation and deposition mechanism of Co-MoS2 composite coatings under magnetic jet electrodeposition were analyzed based on the weak adsorption theory of nanocomposite co-deposition. Research showed that the coating topography changed from a blade-like structure to a cellular structure, and the cellular structure became a granular protrusion structure with increase of the magnetic field intensity. Compared with Co-MoS2 composite coating in jet electrodeposition, the orientation of Co shifted from (110) to (101) as the magnetic field intensity increased in magnetic jet electrodeposition. The adhesion, microhardness, adhesion, corrosion and wear resistance of the composite coatings were enhanced, which was attributed to the influence of the magnetic field on the growth orientation of the composite coating and the coordinated lubrication effect in the Co-MoS2 composite coating.

Reinforcing and toughening mechanism of the in-situ metastable nanostructured alumina-titanium oxide composite coating

High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating. Herein, a metastable nanostructured alumina-titanium oxide composite coating with high density and high properties was synthesized by plasma spraying of TiO2-Al composite powder. The main phases of the metastable nanostructured alumina-titanium oxide were γ-Al2O3, TiO and AlTiO2. The coating, as prepared, contains various metastable microstructures, such as fine-grained, intra-/inter-granular, and "self-locking" microstructures. These metastable microstructures are important for the improvement of hardness and toughness of the coating. Compared with other alumina-based composite coatings, the metastable nanostructured alumina-titanium oxide composite coating showed the most impressive overall performance. The reinforcing and toughening mechanism of the metastable alumina-titanium oxide composite coating included fine grain strengthening and self-toughening of the metastable microstructure.

Construction of Polysiloxane Induced Multilevel Bowl-shaped Janus Particles for Fabrication of Photoluminescent, Enhanced, Heat-insulative Poly(styrene-co-butyl acrylate) Latex Coating

Silica-based nanoparticles (SNPs) are highly regarded as advantageous nanofillers for composite coating, owing to their high surface area, robust mechanical properties, chemical stability, and adaptability for surface modification. Recent studies have unveiled the potential photoluminescence of SNPs induced by intrinsic defect sites, eliminating the need for additional fluorescein molecules. However, the inadequate quantum yield and complex preparation processes for generating defect sites within SNPs have constrained their broader applications. Herein, we propose a facile method to prepare Janus silicon-based nanoparticles with a hierarchical bowl-shaped structure (JHSNPs) through the emulsification of methyltriethoxysilane hydrolysis and condensation products, coupled with the capillary force during nanoparticle formation. The distinctive structure enhances the formation of dioxasilyrane (=Si(O2)) and silylene (=Si:) defects, thereby exhibiting strong blue photoluminescence. The JHSNPs then serve as nanofillers for commonly used poly(styrene-co-butyl acrylate) (SA) waterborne coatings, significantly enhancing their mechanical properties, abrasion resistance, and UV radiation resistance compared to the original SA coatings. Moreover, with just a 1% addition of JHSNPs, the composite coating exhibits visible fluorescence intensity, conferring the self-detecting monitoring properties for external scratches. Due to the hierarchical air-entrapping void structure, JHSNPs composite coatings demonstrate excellent thermal isolation performance, with a 22% reduction in thermal conductivity. The design of JHSNPs opens new avenues to expand the versatility of silica-based nanoparticles in composite coatings, especially in the optical, safety, and energy-saving fields.

Characterization of the interfacial structure and fracture behavior of in situ synthesized ceramics to reinforce Ni-based composite coatings

This work used the in-situ synthesis of molten-state nitride ceramic phase-reinforced Ni-based alloy coatings, aiming to improve the phase-interface bonding through the interdependent co-solidification between molten droplets. The XRD was used to analyze the physical phases of the composite coatings. The microstructure and phase-interface structure were characterized in detail by combining SEM, TEM, HRTEM, FFT, and SAED techniques. Microhardness tester and microforce microhardness tester were employed to measure the surface hardness and elastic modulus of the composite coatings. The fracture behavior of the composite coatings was characterized by observing the fracture morphology of the coatings using SEM combined with the EDS technique. It was found that the formation mechanisms of interfacial misfit dislocation assistance, lattice distortion, aggregation of stacking faults, and specific growth orientation between the γ-Ni matrix phase and each ceramic phase in NiCrBSi-TiCrN composite coatings improved the lattice matching between the two-phase interface, which resulted in the formation of atomically corresponding coherent lattice relations and stepped interfacial semi-coherent lattice relations, and enhanced the degree of phase-interface bonding. On this basis, the composite coatings with high Cr content further inhibited the expansion of interphase penetration cracks due to the existence of Cr-rich zones at the phase interface, thus exhibiting high fracture toughness. This work provides new opinions on the improvement of phase-interface bonding and composition design of Ni-based composite coatings.

Composite Coating of Oleaster Gum Containing Cuminal Keeps Postharvest Quality of Cherry Tomatoes by Reducing Respiration and Potentiating Antioxidant System.

Exploring the green and affordable protection of perishable cherry tomato fruits during storage, herein, the protective efficacy, and its underpinning mechanisms, of a coating of oleaster gum, alone or incorporated with cuminal, on cherry tomatoes stored at ambient temperature was investigated. The composite coating of oleaster gum with 0.1% cuminal reduced the decay, respiration rate, weight loss, and softening of the fruits and decelerated the decreases in their total soluble solid, titratable acidity, and soluble protein levels, and therefore maintained their marketability. Furthermore, it reduced the accumulation of O2·- and H2O2 in the fruits and mitigated cell membrane lipid oxidation and permeabilization, thereby retarding their senescence. Instrumentally, it elevated the activities of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase and the levels of ascorbic acid and glutathione. This potentiation of the fruits' antioxidant system makes this composite coating a promising approach to keeping the postharvest quality of perishable fruits.

Chloride ion-responsive active protection epoxy composite coatings realized by 2-Mercaptobenzimidazole and 2-Mercaptobenzothiazole intercalated Mg-Al layered double hydroxides

Designing functionalized anti-corrosion fillers for harsh corrosive environments remains a significant challenge in the field of coatings. In this study, corrosion inhibitors 2-Mercaptobenzimidazole (MBI) or 2-Mercaptobenzothiazole (MBT) were intercalated into Mg-Al layered double hydroxides (LDH) using the calcination-rehydration method. For both inhibitors, with the addition of 3 wt% intercalated LDHs, the composite epoxy (EP) coatings exhibited favorable overall properties and anti-corrosion capabilities. The electrochemical impedance spectroscopy (EIS) and localized electrochemical impedance spectroscopy (LEIS) were used to investigate the scratched pure EP, LDH-MBI/EP, and LDH-MBT/EP coatings. The results showed that LDH-MBI/EP and LDH-MBT/EP demonstrated significant ion-responsive behavior and active protection capabilities.

Effect of graphene oxide on CoCrFeNi high-entropy alloy coatings prepared by the electrodeposition method

The performance advantages of high-entropy alloy (HEA) have become a consensus. However, the current preparation methods are mostly focused on thermal processing methods, and the research on the preparation of HEA coatings using electrochemical technology is generally rare. Therefore, in this study, the CoCrFeNi HEA coating was synthesized by electrodeposition technology and the effect of graphene oxide (GO) concentration on the microstructure and tribological property of the HEA coating was further studied. The results showed that during the electrodeposition process, the four atoms of Co, Cr, Fe and Ni were co-deposited to form the HEA coating with a face-centered cubic crystal structure. The introduction of GO did not change the crystal structure of HEA coatings, and GO was also co-deposited with metal atoms to form the HEA-GO composite coating. Meanwhile, GO was distributed in composite coatings in the form of being encapsulated by the metal layer. The addition of GO improved the compactness of HEA coating and reduced the surface roughness. The increase in GO concentration helped to inhibit the formation of the stress-induced cracks on the surface of the composite coating, and significantly enhanced the wear resistance of HEA coating. When the GO concentration was 0.2 g/L, the wear resistance was the best. The wear form of composite coatings was independent of GO and its concentration, and was dominated by abrasive wear.

Enhanced Storage Resistance of Mulberries Using Laminated Cellulose Nanocrystals/Chitosan Composite Coatings

Enhanced Storage Resistance of Mulberries Using Laminated Cellulose Nanocrystals/Chitosan Composite Coatings

Microstructural Characterization, Mechanical Performance, and Anti-Corrosive Response of Zinc Multifaceted Coating on Mild Steel

Zinc has attracted significant attention in research due to its cost-effective use as an electrodeposited material, effectively protecting various types of steel from corrosion and wear. However, despite its advantages, zinc has limitations in fully guarding steel against corrosion. Recent studies propose that blending zinc with other metals during the coating process can proficiently shield mild steel from deterioration. The motivation for this study stems from recognizing the restrictions of zinc electrodeposition and the limited exploration of zinc multi-facet composite coatings for mild steel. In this study, the electrodeposition technique was employed to apply a coating to mild steel using zinc and nanoparticles of calcium oxide (CaO) and manganese oxide (MnO2). The coating bath's chemical composition included mass variations of 0-12 g/L for CaO and MnO2, along with 10 g/L each of boric acid, thiourea, and Na2SO4, and 15 g/L of K2SO4 and ZnSO4. The coating process occurred over a twenty-minute period, with a pH of 4.8, voltage set at 3.2V, current density at 1 A/cm2, temperature at 47°C, and stirring rate at 200 rpm. Results obtained from the coated mild steel demonstrated that Zn-6CaO-6MnO2 exhibited the greatest coating thickness at 0.2308 mm, and it showcased impressive corrosion resistance at 2.0618 mm/year. The Zn-CaO-MnO2 coating displayed a substantial deposit of crystallites in its microstructure, assisted by the presence of manganese, contributing to a smoother surface texture.

Mechanism Insights in Anticorrosion Performance of Waterborne Epoxy Coatings Reinforced by PEI-Functionalized Boron Nitride Nanosheets.

Functionalized hexagonal boron nitride nanosheets (BNNSs) have arisen as compelling anticorrosive additives, yet the precise mechanism of their corrosion resistance enhancement in coatings remains unclear. Here, polyethylenimine functionalized BNNSs (PEI-BNNSs) with approximately 6-11 layers were prepared through a "one-step" method. Then, the PEI-BNNSs/Waterborne epoxy (WEP) composite coatings were incorporated via the waterborne latex blending method for the anticorrosion of the Q235 substrate. The impedance modulus (|Z|f = 0.01 Hz) of 0.5 wt % PEI-BNNSs/WEP composite coating soaked in 3.5 wt % NaCl solution for 35 days increased by 4 orders of magnitude compared to pure WEP coating, exhibiting exceptional long-term resistance against corrosion. The positron annihilation lifetime spectroscopy and corrosion product analysis demonstrated that the reinforced anticorrosion capabilities are not solely ascribed to the "tortuous path effect" arising from BNNSs impermeability. These mechanisms also encompass the reduction in free volume fraction and radius of the free volume cavities within the composite coating brought about by the PEI molecules. Additionally, the increase in coating adhesion, promoted by PEI, plays an important role in augmenting the barrier properties against corrosive agents. This study provided a full comprehension of the role played by functionalized BNNSs in fortifying the anticorrosion attributes of WEP coatings.

The effects of in-situ synthesized TiC on the performance improvement of nickel-based composite coatings for rail repair

With the increase in train speed and axle weight, the quality and service life of the rail (U71Mn steel) are more demanding. Aiming at the excellent properties of nickel/nickel-based alloys and ceramic materials, this paper prepares TiC/Ni45 composite coatings for rail repair by in-situ synthesis of ceramic phases using laser cladding technology. The effects of in-situ synthesized TiC on the physical phase, microstructure, microhardness and wear resistance were investigated and discussed in detail. The results show that the reaction of in-situ synthesized TiC can proceed positively, and the microstructure of the cladding layer mainly consists of the segregation of Cr, TiC particles, and substrate phase. With the increase of nickel-coated graphite and titanium powder, the average microhardness value of the cladding layer increased, and the average friction coefficient and wear volume decreased. When the mass fraction of (Ti + C) reaches 15 wt%, the average friction coefficient of the cladding layer reaches the minimum value. When the mass fraction reaches 20 wt%, the average microhardness of the cladding layer reaches 2.65 times that of the substrate, and the wear mechanism is transformed from mainly adhesive wear to abrasive, oxidative, and fatigue wear.

Micro-structures and dry sliding wear properties of novel AlCrFeNiMo0.5-x(WC) high entropy alloy-ceramic composite coatings

Based on the problems of micro defects (cracks, pores, etc.), uneven distribution of strengthening particles, and poor bonding between strengthening particles and metal matrix in practical engineering applications, the new AlCrFeNiMo0.5-x(WC) (x = 0, 5, 15, 30 wt%) composite coatings have been designed, and further prepared using laser cladding. Their micro-structures, micro-hardness and dry sliding wear properties were deeply explored. They exhibited the dendritic morphologies and consisted of BCC1, BCC2, and carbide phases. The AlCrFeNiMo0.5-30 wt%(WC) coating had the highest hardness (772 HV), which was approximately 5 times that of Q235 steel substrate. With the increase of WC content, dry sliding wear properties showed an increasing trend, that is, AlCrFeNiMo0.5-30 wt%(WC) coating had the lowest friction coefficient (0.50) and wear rate (9.23 × 10−6 mm3/(N · m)), exhibiting excellent tribological properties, which was attributed to the coupling effect of hard carbide and ductile BCC phases. It would be a promising wear-resistant coating material under dry sliding environment. This study not only has significant theoretical significance for understanding the failure patterns and performance evolution of new high entropy alloy/WC composite coating materials in dry sliding environments, but also demonstrates important value for expanding the application of new high entropy alloy/WC composite coating materials in practical engineering.

Sideritis raeseri-Modified Coatings on Ti-6Al-4V as a Carrier for Controlled Delivery Systems of Active Substances.

The search for the ideal metallic material for an implant is still a difficult challenge for scientists due to the phenomenon of corrosion and the consequent disruption of the implant structure. Prevention is the application of coatings that protect the implant, activate the tissues for faster regeneration, and also prevent inflammation through antibacterial and antiviral effects. The present study focuses on the selection of components for a Ti-6Al-4V alloy coating. These days, researchers are taking an intense interest in extracts of natural origin. It was decided to take a look at Sideritis raeseri, which contains vitamins and valuable elements and is rich in polyphenols, as well as antioxidants. The composition of coatings based on a PEG polymer reinforced with brushite and the S. raeseri extract with the proteins L-carnosine, fibroin, or sericin was developed. The samples were subjected to detailed physiochemical analysis, including potentiometry and electrical conductivity analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and UV-VIS spectroscopy. The study demonstrated that polyphenols were successfully released from the coatings during incubation in vitro. The osteointegration process can be supported by a number of factors, such as the release of polyphenols from implant coatings to prevent bacterial, viral, and fungal infections. Subjecting the samples to 14 days of incubation demonstrated their interactions with the incubation fluids, an ion exchange between the medium and the materials. An analysis of the surface morphology exhibited the presence of brushite crystals and their increased number after incubation, indicating the bioactivity of the formed coatings.

Effect of B addition on the microstructure and tribological properties of laser cladding FeCoCrNiCu composite coatings

The high-entropy alloy coatings of FeCoCrNiCuBx (x = 0, 0.1, 0.3, 0.5, x values are molar ratios) were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and surface energy of the FeCoCrNiCuBx coatings were investigated, and the tribological property and wear mechanism of the composite coatings at room temperature (RT) and 600 ℃(HT) were analyzed. The FeCoCrNiCu coating consists of a single FCC-type solid solution. When x = 0.3, 0.5, the composite coatings appear the Cr2B phase. The x = 0.5 (B5) coating has the lowest surface energy (27.45mN/m), which is one of the reasons it has excellent tribological properties. The tribological properties of FeCoCrNiCuBx composite coatings were improved at both RT and HT. The B5 coating has excellent tribology at both RT and HT. At RT, the wear resistance of the B5 coating (wear rate is 8.54 ×10−5 mm3/N∙m, coefficient of friction (COF) is 0.51) was improved by 54.79%, 50.89%, and 12.86% compared with x = 0(HEA), x = 0.1(B1), and x = 0.3(B3), respectively, the COF reduced by 42.69%, 41.39%, 22.73%. At HT the wear resistance of the B5 coating (wear rate is 6.69 ×10−5 mm3/N∙m, COF is 0.24) was increased by 71.53%, 52.91%, and 49.42% compared to HEA, B1, and B3, respectively, the COF reduced by 29.41%, 25.00%, 17.24%. The wear mechanisms of coatings that add B element at RT are abrasive wear and fatigue wear, and at HT are mainly oxidative wear, moderate abrasive wear and fatigue wear.B2O3 melts at HT to form a low-viscosity liquid that forms a lubricating film that isolates the contact surfaces and reduces direct contact and adhesion. This is the main reason for the excellent friction properties of B5 coating at HT.

Nanoarchitectonics of Bactericidal Coatings Based on CaCO3-Nanosilver Hybrids.

Antimicrobial coatings provide protection against microbes colonization on surfaces. This can prevent the stabilization and proliferation of microorganisms. The ever-increasing levels of microbial resistance to antimicrobials are urging the development of alternative types of compounds that are potent across broad spectra of microorganisms and target different pathways. This will help to slow down the development of resistance and ideally halt it. The development of composite antimicrobial coatings (CACs) that can host and protect various antimicrobial agents and release them on demand is an approach to address this urgent need. In this work, new CACs based on microsized hybrids of calcium carbonate (CaCO3) and silver nanoparticles (AgNPs) were designed using a drop-casting technique. Polyvinylpyrrolidone and mucin were used as additives. The CaCO3/AgNPs hybrids contributed to endowing colloidal stability to the AgNPs and controlling their release, thereby ensuring the antibacterial activity of the coatings. Moreover, the additives PVP and mucin served as a matrix to (i) control the distribution of the hybrids, (ii) ensure mechanical integrity, and (iii) prevent the undesired release of AgNPs. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) techniques were used to characterize the 15 μm thick CAC. The antibacterial activity was determined against Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa, three bacteria responsible for many healthcare infections. Antibacterial performance of the hybrids was demonstrated at concentrations between 15 and 30 μg/cm2. Unloaded CaCO3 also presented bactericidal properties against MRSA. In vitro cytotoxicity tests demonstrated that the hybrids at bactericidal concentrations did not affect human dermal fibroblasts and human mesenchymal stem cell viability. In conclusion, this work presents a simple approach for the design and testing of advanced multicomponent and functional antimicrobial coatings that can protect active agents and release them on demand.

Effects of plasma spraying process on microstructure and mechanical properties of Cr2AlC/410 composite coatings

To investigate the influences of Cr2AlC mass fraction and supersonic plasma spraying process on the microstructure and mechanical properties of Cr2AlC reinforced 410 stainless steel composite coatings, the coatings containing different mass fractions of Cr2AlC were prepared and investigated. The composite coating exhibited low porosity and high adhesion strength. The addition of Cr2AlC significantly enhanced the hardness of the composite coatings through particle strengthening. However, when the mass fraction of Cr2AlC was 20%, the aggregation of Cr2AlC resulted in a strong decrease in the coating preparation efficiency, as well as a decline in adhesion strength. In the supersonic plasma spraying process, the Ar flow rate mainly influenced the flight velocity of the particles, while the H2 flow rate and the current mainly affected the temperature of the plasma torch. Consequently, all of them influenced the melting degree of particles and the quality of the coating. The lowest porosity and the highest hardness and adhesion strength could be obtained when the Ar flow rate is 125 L/min, the H2 flow rate is 25 L/min, and the current is 385 A.

Preparation and Properties of Environmentally Friendly, Hydrophobic, Corrosion-Resistant, Multifunctional Composite Coatings

With the continuous exploitation of the marine resources, the equipment should meet the marine complex working environment. In this study, a type of environmentally friendly coating was prepared. Based on low surface energy environmental protection and anti-fouling, a film forming material with water-based epoxy-modified silicone resin emulsion was prepared. And industrial fillers were added to give it both inorganic and organic properties. Meanwhile, various contents of graphene oxide (GO) were added in the coating system. The coating properties were comprehensively analyzed, and the optimal GO content was obtained as 0.1 wt. %. The composite coating was studied by seawater immersion experiments, and the failure process of the coating in was proposed. The composite coating prepared in the present study has both environmental protection and hydrophobic anti-fouling characteristics, and its comprehensive performance is excellent through various performance evaluations, i.e., it meets the requirements of long-term coating, environmental friendliness and anti-fouling and corrosion resistance.

Photothermal superhydrophobic composite coatings based on n-tetradecane@CaCO3/TiN microcapsules for anti-/deicing

Ice accumulation on equipment and building surfaces is a scientific and modern engineering problem to be solved urgently. Compared to the energy-intensive and expensive active anti-/deicing approaches, passive energy-free technology based on advanced materials and surface engineering has received more attention. Herein, we successfully encapsulated n-tetradecane in calcium carbonate shell by in situ precipitation method, and the microcapsules reveal good energy-storage capability (99.9 %), latent heat (108.1 J g−1), and long-term durability. Combining the microcapsule with low-cost titanium nitride and low-surface-energy PDMS (polydimethylsiloxane) materials, the multifunctional superhydrophobic composite coating has been successfully prepared. The composite coating surface possesses strong absorption in UV–vis-NIR bands with high photothermal conversion and storage capability. The results indicate that the composite coating successfully prolongs the icing time compared to traditional photothermal superhydrophobic surfaces, and accelerates the melting of ice droplets under light illumination, which demonstrates great potential in both anti-icing and deicing applications.

Nanocrystalline Y2O3-modified metal matrix composite coatings with improved resistance to thermocyclic oxidation and V2O5-induced type II hot corrosion

Incorporating reactive elements (RE) into turbine coatings is a well-established surface treatment. However, suboptimal RE concentrations can lead to compromised strength, heightened brittleness, and reduced adhesion. In contrast, RE oxides offer advantages of avoiding these detrimental effects, counteracting corrosion phenomena induced by V2O5 compounds and enhancing oxidation resistance. A notable challenge lies in optimizing RE oxide particle incorporation and understanding the influence of particles in coating microstructures. This study focuses on developing NiAl and Ni-Cr-Al type metal matrix composite (MMC) coatings on Inconel 617 (IN617), containing up to 11 vol% of Yttria (Y2O3) nanoparticles. Y2O3 nanoparticles and Ni were co-electrodeposited on IN617 followed by either pack aluminizing or a two-step chromizing and aluminizing process. An even distribution of Y2O3 nanoparticles was observed throughout the entire 100 μm coating thickness, leading to significant grain refinement in the sub-micron to nano range in both coating types. Y2O3-strengthened coatings were subjected to oxidation at 1100 °C and hot corrosion at 700 °C and were compared to their Y2O3-free counterparts. Present at grain boundaries, Y2O3 markedly enhanced the oxidation and corrosion resistance by reducing interdiffusion, improving the oxide scale adherence and binding V2O5, highlighting the potential of this method for advanced turbine blade coatings.

Effects of graphene-based corrosion inhibition materials on the microstructure and corrosion resistance of Ni-based coating on Mg-Li alloys

Two kinds of layered double hydroxides inhibition materials were synthesized on graphene oxide, and applied to strengthen the Ni-based coating on Mg-Li alloy. The composition and release properties of corrosion inhibition materials were studied. The formation of passivated film and the corrosion resistance mechanism of coating were summarized. The results show that two kinds of corrosion inhibition materials had good release properties. The addition of corrosion inhibition materials was helpful to form Ni-based composite coatings with fine and dense cell clusters, which strengthened the corrosion resistance of the coating, especially for a long time.