Search Results (182)

Acrylic resin is a polymer with strong crosslinking density and strength, and it is commonly used as a matrix in water-based coatings. Barium europium phosphate (Ba₃Eu(PO₄)₃) is a novel functional filler that is expected to provide anti-corrosive effects to coatings. In this study, Ba₃Eu(PO₄)₃ was prepared by the high-temperature solid-phase method and applied to acrylic anti-corrosion coatings. The influence of the molar ratio of reactants on Ba₃Eu(PO₄)₃ purity was studied. The anti-corrosion performance of the coating was investigated. It was found that, when BaCO₃:Eu₂O₃:(NH₄)H₂PO₄ = 3:0.5:3 and the reaction was carried out at 950 °C for 1000 min, high-purity Ba₃Eu(PO₄)₃ can be obtained, according to XRD and EDS tests. SEM shows that Ba₃Eu(PO₄)₃ has good crystal morphology and a porous morphology. TEM revealed that its structure was intact. When Ba₃Eu(PO₄)₃ was added to a relative resin content of 5 wt%, the anti-corrosion performance of the coating was the best after 168 h, with the lowest Tafel current density of 9.616 μA/cm² and the largest capacitance arc curvature radius. The salt spray resistance test showed that the corrosion resistance of the 5 wt% Ba₃Eu(PO₄)₃ coating was also the best, which is consistent with the results of the electrochemical test. Ba₃Eu(PO₄)₃ as a pigment and filler can effectively improve the anti-corrosion performance of water-based industrial coatings. Full article

The low hardness and insufficient wear resistance of aluminum and its alloys restrict their broader application in various fields. The application of surface protective coatings can effectively enhance the hardness and wear resistance of aluminum and its alloys. This article provides a comprehensive review of the recent research progress of wear-resistant coatings fabricated on aluminum and its alloys. The relevant achievements in the recent research works of preparing wear-resistant coatings by one-step methods (such as anodic oxidation, micro-arc oxidation, cold spraying, plasma spraying, and electrodeposition) and two-step methods (anodic oxidation and physical vapor deposition, micro-arc oxidation and sealing, magnetron sputtering, and plasma nitriding) are mainly introduced. The working principles of each coating preparation method, along with their impacts on the microstructure and tribological performance of the coatings, were systematically examined. Additionally, a comparative analysis was conducted to evaluate the advantages and disadvantages of each coating preparation method. Full article

Breath-actuated nebulizers used in aerosol therapy are vital to children and patients with disabilities and stand out for their ability to accurat ely deliver medication while minimizing waste. Their performance can be measured according to the mass output and droplet size. This study aimed to analyze how the baffle impact surface geometries affect the pressure and flow streamlines inside the nebulizer using computational fluid dynamics (CFD). Computer-aided design models of conical symmetric, conical asymmetric, and arc-shaped baffle designs were analyzed using CFD simulations, with the optimal spray output validated through the differences in mass. Conical baffles exhibited superior pressure distribution and output streamlines at 0.25 cm protrusion, suggesting that the nebulizer spray performance can be enhanced by using such a conical baffle impact surface. This result serves as a valuable reference for future research. Full article

To enhance the surface protection of exposed moving parts made from magnesium alloys, this study focuses on developing high-performance micro-arc composite (MCC) coatings on AZ80 wrought magnesium alloy substrate. AZ80 alloys were fabricated through forging at different temperatures (250 °C, 350 °C, and 450 °C) to investigate the influence of thermal deformation on substrate properties. Subsequently, micro-arc oxidation (MAO) coatings and MCC coatings were applied to the forged alloys. Comprehensive analyses—including microstructural characterization, salt spray corrosion tests, and stress corrosion cracking (SCC) evaluations—were conducted under both static and stress conditions. Among the forging temperatures, 250 °C produced substrates with refined grains and a favorable distribution of β-Mg₁₇Al₁₂ precipitates, resulting in improved baseline corrosion resistance. MAO coatings offered moderate protection, primarily delaying corrosion initiation and crack propagation under stress environments. Building upon this foundation, MCC coatings—fabricated by electrostatic spraying to form an inner-embedded and outer-wrapped structure over the MAO layer—demonstrated significantly superior protective performance. Under both static and stress corrosion scenarios, the MCC coatings effectively suppressed SCC initiation and progression, highlighting their potential for robust surface protection in demanding service environments. Full article

Titanium (Ti) and its alloys have attracted more interest, as they are widely employed as biomaterials due to their great biocompatibility, excellent strength ratio, and lightweight. However, corrosion occurs slowly due to an electrochemical reaction once the Ti material has been placed in the human body, contributing to infection and failure of implants in medical applications. Thus, the corrosion phenomenon has caused great concern in the biomedical field. It is desirable to make the surface modification to provide better corrosion resistance. The fabrication techniques of the coatings fabricated onto Ti and/or Ti alloy surfaces have been reported, including sol–gel, annealing, plasma spraying, plasma immersion ion implantation, physical vapor deposition, chemical vapor deposition, anodization, and micro-arc oxidation. This review first describes the corrosion types, including localized corrosion (both pitting and crevice corrosion), galvanic corrosion, selective leaching, stress corrosion cracking (SCC), corrosion fatigue (CF), and fretting corrosion. In the second part, the effects of corrosion on the human body were discussed, and the primary cause for clinical failure and allergies has been identified as the excessive release of poisonous and dangerous metal ions (Co, Ni, and Ti) from corroded implants into bodily fluids. The inclusion and exclusion criteria during the selection of literature are described in the third section. In the last section, we emphasized the current research progress of Ti alloy (particularly Ti6Al4V alloy) coatings in biomaterials for medical applications involving dental, orthopedic, and cardiovascular implants for anticorrosive applications. However, there are also several problems to explore and address in future studies, such as the release of excessive metal ions, etc. This review will draw attention to both researchers and clinicians, which could help to increase the coatings fabricated onto Ti and/or Ti alloy surfaces for anticorrosive applications in biomaterials for medical applications. Full article

Due to the low hardness of carbon steels, their low resistance to wear, and erosion by cavitation and corrosion, it is necessary to protect the surfaces of parts with layers capable of ensuring the properties listed above. In this paper, we started from the premise that adding tungsten carbide (WC) powders during the electric arc spraying process of stainless steel would lead to obtaining a composite material coating resistant to wear and erosion at high temperatures, with relatively lower manufacturing costs. Thus, our research compared the following two types of coatings: a highly alloyed layer with WC, Cr, and TiC (obtained from 97MXC core wires) and a 60T/WC coating (obtained from a 60T solid-section wire to which WC was added), in terms of microstructure, mechanical properties, dry friction wear, and behaviour at erosion by cavitation (EC). The results of our research demonstrated that although the 60T/WC coating had lower erosion by cavitation behaviour than the 97MXC one, it can still be considered as a relatively good and inexpensive solution for protecting C15 steel parts. Full article

Chitooligosaccharides (COS) exhibits good activity of inducing plant resistance, but the structure–activity relationship is still unclear. In this study, chitin oligosaccharides (CHOS) with a degree of polymerization (DP) of 2~6 were used as raw materials. Three deacetylases (NodB, VcCOD, and ArCE4A) were employed to prepare three different sequence-arranged COSs, namely N-COS, C-COS, and A-COS, and their structures were characterized by infrared spectroscopy, high-performance liquid chromatography, and mass spectrometry. Further studies were conducted on inducing the plant salt resistance of the three different sequence-arranged COSs on wheat seedlings. The results showed a sequence-dependent effect of COS inducing plant salt resistance. Among them, A-COS exhibited the best activity. When sprayed at a concentration of 10 mg/L on wheat seedlings under salt stress for 3 days, the leaf length of the wheat seedlings sprayed with A-COS was recovered, and the wet mass and dry mass were recovered by 20.40% and 6.64%, respectively. Following the enhancement of proline accumulation, the malondialdehyde content decreased by 34.75%, and the Na⁺/K⁺ ratio also exhibited a significant reduction, thereby alleviating salt stress-induced damage. This study was the first to demonstrate the effect of COS with specific sequences on inducing plant salt resistance, providing a theoretical basis for the development of a new generation of efficient COS plant biostimulator. Full article

Annealing and rolling play critical roles in improving the mechanical properties of arc spraying coatings. In this work, we successfully fabricated copper–steel bimetallic sheets (CSBSs) using an arc spray-rolling short process and achieved excellent internal bonding of the copper coating and improved deep-drawing of the CSBSs via annealing and rolling synergistic treatment. The results indicate that the microstructure of the copper coating became dense, and the porosity effectively reduced after annealing–rolling–annealing (ARA) treatment. Tight bonding was also observed between the copper coating and steel substrate. The copper coating had a porosity of less than 0.2%, an average grain size of 3.8 μm, and a micro-hardness of 55 HV_0.05. After tensile testing, the As-sprayed coating generated brittle fractures and delamination. The A-R-A coating also displayed elongated dimples, with the majority oriented along the TD direction, and bonded well with the steel substrate. In addition, the As-sprayed coating fell off directly after deep drawing. In contrast, the A-R-A coating did not exhibit cracks and fall off. The fracture mechanism gradually changed from falling off and cracking, to toughness deformation due to the reduced porosity and tighter grain boundaries, and finally to cooperative deformation due to the metallurgical bonding of the sprayed particles and good interface bonding properties. These findings provide guidance and reference for the practical application of thermal spray additive manufacturing. Full article

Electric arc furnace oxidizing slag (EAFOS) represents 80% of the electric arc furnace slag generated. Recently, EAFOS has been utilized as high value-added functional aggregate in a growing number of cases for the construction of air-cooling technology that turns EAFOS into fine aggregate-sized particles by spraying it into the air using high-pressure compressed air. Ladle furnace slag (LFS) is a product of the reduction process, accounting for approximately 20% of the steel slag enerated; however, LFS is predominantly landfilled without being utilized. This is mainly because LFS changes into sludge as it is turned into powder during water spray cooling. Therefore, in this study, spherical particles cooled at room temperature were fabricated as fine aggregates using LFS by applying atomization technology that uses high-pressure air in the molten state for the value-added utilization of LFS. Various experiments were performed to examine whether this aggregate can be used as a construction material. The experimental results showed that the air-cooled LFS (ALFS) fine aggregate generated from two different processes met the physical and chemical properties of the fine aggregate required for concrete despite its slightly lower spherical ratio compared to EAFOS aggregate. The volumetric stability experiment results also showed that ALFS fine aggregate is more stable than river sand and standard sand. In addition, the autoclave test results revealed that the mortar produced using ALFS fine aggregate was more stable for expansion than that of comparison groups. These results confirm the applicability of ALFS as an aggregate for construction. However, because the pop-out phenomenon caused by MgO was observed on the surface of some specimens, further research is required for improvement. Full article

The incorporation of a homogeneously distributed nanocrystalline phase in Fe-based amorphous coatings is widely acknowledged to enhance wear resistance across various applications. In this study, FeCrMoWBRE amorphous/nanocrystalline composite coatings were fabricated on 45# steel substrates using high-velocity arc spraying (HVAS). The coatings were produced under varying spraying voltages, currents, and distances, following the Taguchi experimental design methodology. The microstructure, mechanical properties, and wear resistance of the coatings were systematically analyzed, with a particular focus on the relationship between nanocrystalline/amorphous phase content and key performance metrics, including microhardness, adhesive strength, and wear rate. A positive correlation was observed between the nanocrystalline phase content and both mechanical properties and wear resistance. The coating with optimized nanocrystalline phase content of 21.4% exhibits the lowest wear rate of 1.39 × 10⁻⁷ mm³·N⁻¹·m⁻¹ under a 100 N load and oil lubrication. These findings underscore the critical role of controlling the nanocrystalline phase content in Fe-based amorphous/nanocrystalline composite coatings to maximize wear resistance under oil-lubricated conditions. Full article

Intermetallic compounds from the Fe-Al system are attracting increasing attention due to their outstanding properties, including excellent mechanical performance, low density, corrosion, and oxidation resistance, as well as resistance to sulfidation, carburization, and wear at elevated temperatures. These unique characteristics make Fe-Al intermetallics promising candidates for high-temperature and harsh environmental applications. However, challenges such as brittleness and low plasticity have hindered their broader use. By exploring the impact of spray conditions on coating properties, this study contributes to enhancing the performance and functionality of Fe-Al coatings in industrial applications, where durability and resistance to extreme conditions are essential. This article presents the results of research on the production of composite coatings from the Fe-Al system with in situ fabricated intermetallic phases. For this purpose, arc spraying in an inert gas was used. The coating manufacturing process was carried out by simultaneously melting two different electrode filler wires, aluminum and steel, in a stream of argon. The obtained coatings were subjected to tests of roughness, adhesion to the substrate, and microstructure. It was shown that both the roughness and adhesion to the substrate of coatings sprayed in air are higher than those sprayed in argon. The increase in roughness results from the greater oxidation of coatings sprayed in air, while better adhesion is the result of the formation of coatings at a higher temperature. Metallographic studies have shown that during the spraying process, the in situ synthesis of intermetallic phases occurred. The results showed the local occurrence of intermetallic phases from the Fe-Al system. Among the two dominant phases, i.e., Al and the Fe alloy, there are also the following phases: FeAl₃, FeAl₂, and Fe₂Al₅. Furthermore, in layers sprayed in an inert atmosphere, the share of oxides is small. Full article

1Cr18Ni9Ti and Monel composite metal coatings with five different spraying distances were prepared by arc spraying technology. The density, hardness, friction, and wear properties and acid corrosion rate of the coatings with different spraying distances were studied by X-ray diffraction, scanning electron microscopy, Rockwell hardness test, and friction and wear test. Research shows that the spraying distance has a significant effect on the density, hardness, porosity, friction, and wear properties and corrosion rate of the coating. When the spraying distance is 250 mm, the coating has the maximum density and hardness, the minimum porosity and corrosion rate, and the minimum friction coefficient and wear volume. Cu3.8ni and cr0.19fe0.7ni0.11 compounds in the coating have significant effects on the friction, wear, and hardness of the coating. The results show that too-high or too-low spraying distance will lead to pores and large particle agglomeration in the coating, which will affect the surface physical properties of the coating. Full article

This paper presents the initial results of the synthesis of β-Ga₂O₃ luminescent ceramics via plasma gas-thermal spraying synthesis, where low-temperature plasma of an argon and nitrogen mixture was employed. A direct current electric arc generator of high-enthalpy plasma jet with a self-aligning arc length and an expanding channel of an output electrode served as a plasma source. The feedstock material consisted of a polydisperse powder of monocrystalline β-Ga₂O₃ with particle sizes ranging from 5 to 50 μm. The study presents the results of both theoretical and experimental studies on the heating rate and average temperature of gallium oxide particles in a plasma jet. The results of computational modelling of the synthesis process of β-Ga₂O₃ via plasma gas-thermal spraying are shown. The obtained ceramic samples were characterized using scanning electron microscopy and X-ray diffraction analysis. Our results indicate that the synthesis process yielded ceramics with a layered texture. The stoichiometric composition of ceramics exhibited a shift towards gallium-rich content. X-ray diffraction data demonstrated a reduction in the lattice parameters and unit cell volume of β-Ga₂O₃ ceramic structure. Radioluminescence spectra of β-Ga₂O₃ ceramics revealed an intensive emission band with a maximum at ~360 nm and non-exponential decay. The synthesized β-Ga₂O₃ ceramics possess potential applications in scintillation detectors. Full article

Wire arc additive manufacturing (WAAM) with a special arc mode of cold metal transfer pulse advanced (CMT-PADV) is an ideal additive manufacturing process for fabricating aerospace components, primarily high-strength aluminum alloys, offering advantages such as high deposition rates and low cost. However, the numerical simulation of the CMT-PADV WAAM process has not been researched until now. In this study, we first developed a three-dimensional fluid dynamics model for the CMT-PADV WAAM of 7075 aluminum alloy, aiming at analyzing the droplet transition and molten pool flow. The results indicate that, under the CMT-PADV mode, droplet transition follows a mixed transition mode, combining short-circuiting and spray transition. The Direct Current Electrode Positive period of the arc accelerates droplet spray transition, significantly increasing molten pool flow. In contrast, the Direct Current Electrode Negative period of the arc predominantly features droplet short-circuiting transition with low heat input and a weak impact on the molten pool. The periodic switching of the current polarity of CMT-PADV mode results in periodic variations in molten pool size and volume, reducing heat input while maintaining high deposition quality. The revelation of this mechanism provides process-based guidance for low-defect, high-performance manufacturing of critical components. Full article

To improve the adhesion strength of polymer functional films, corona treatment is required. Corona rollers are key components for corona treatment, which are used in high-voltage electric fields for a long time. In this work, in order to improve electrical insulation, arc resistance, wear resistance, and chemical stability, a coating is usually sprayed on the surface of the corona roller. Al₂O₃/h-BN composite coatings are prepared on the surface substrate of a corona roller (20 steel) by atmospheric plasma spraying (APS) technology. Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) analysis showed that the Al₂O₃/h-BN composite coating had a layered structure and compactness. Two kinds of Al₂O₃/h-BN composite coatings are prepared under different APS process parameters; the porosities of A coating and B coating are 6.04% and 4.75%, the microhardnesses are 781 ± 0.5 Hv and 840.5 ± 0.5 Hv, and the adhesion strengths are 22.0 MPa and 22.3 MPa, respectively. The A and B volume resistivity of the coatings are 9.29 × 10¹⁰ Ω·cm and 3.55 × 10¹⁰ Ω·cm, respectively. The volume resistivity and porosity of the coatings are negatively correlated, and they decrease with the increase in spraying current. But for both coatings, volume resistivity is greater than 1 × 10¹⁰ Ω cm. These results indicate that the Al₂O₃/h-BN composite coatings, as a new type of electrode roller coating, satisfy the use requirement. Al₂O₃/h-BN composite coatings can become the potential for ceramic coatings that have good mechanics and insulation performance. Full article