Search Results (1,655)

The low hardness of copper alloys, which are the substrate material used for continuous casting molds, makes them prone to plastic deformation, wear, and high-temperature oxidation, leading to premature failure and the formation of surface defects on billets. In this work, the microstructure, phase composition, mechanical, and tribological properties of Cr₃C₂–NiCr coatings deposited by high-velocity oxy-fuel (HVOF) spraying onto copper substrates used in molds were investigated. This research was driven by the need to extend the service life of copper molds in continuous steel casting processes. It was established that spraying parameters have a decisive influence on porosity, coating thickness, microhardness, and friction behavior under conditions simulating billet contact with the working surface of the mold. Among the investigated regimes, the coating deposited at a powder feed rate of 11.39 m/s exhibited a dense lamellar structure and the highest level of microhardness. Tribological tests confirmed that this coating exhibited the lowest coefficient of friction, whereas the other coatings were characterized by higher porosity and poorer wear resistance. Thus, the results emphasize the necessity of optimizing spraying parameters to develop highly effective HVOF protective coatings for copper molds operating under extreme thermomechanical loads during steel casting. Full article

Two Ni-AlSi12 coatings were prepared using mechanical alloying (MA) and mechanical alloying followed by laser cladding (LC), respectively. Phase composition and microstructure variations caused by powder weight ratio and laser-specific energy were thoroughly analyzed in this study. Mechanical properties and oxidation behavior are markedly improved by subsequent laser cladding. The MA-LC coating, characterized by high densification and crack-free properties, presents a homogeneous microstructure with refined features. Microhardness testing reveals a marked superiority of the MA-LC coating over the conventional MA coating. The nano-hardness of MA-LC coating is 9.79 GPa, exhibiting that it is 6.84 times the nano-hardness of the MA sample. Owing to metallurgical bonding, the MA-LC coating possesses excellent scratch bonding performance. The MA-LC coating shows favorable oxidation behavior, due to the following three reasons: Firstly, oxygen diffusion can be effectively blocked by the compact Al₂O₃ oxide layer developed on the MA-LC coating surface, which reduces the oxidation velocity. Secondly, the coating’s mean grain dimensions demonstrate an increasing tendency after oxidation, which reduces the grain boundary serving as the oxygen diffusion channel. This enhancement significantly improves the coating’s oxidation resistance. Thirdly, analysis of the coating’s respective kernel average misorientation (KAM) map revealed a significant release of internal stress following 100 h oxidation, which can improve the coating’s resistance to spallation. Full article

Surface coatings have proven highly effective in addressing the critical challenges of friction, wear, and corrosion on steel substrates, which are responsible for over 80% of mechanical failures in industrial applications. Recent research highlights that advanced coatings—such as ceramic carbides/nitrides, high-entropy alloys, and metal-matrix composites—significantly enhance hardness, wear resistance, and environmental durability through mechanisms including protective oxide film formation, solid lubrication, and microstructural refinement. Moreover, these coatings exhibit robust performance under combined tribological-corrosive (tribocorrosion) conditions, where synergistic interactions often accelerate material degradation. Key developments include multilayer and composite architectures that balance hardness with toughness, self-lubricating coatings capable of in situ lubricant release, and active or self-healing systems for sustained corrosion inhibition. Despite these advances, challenges remain in predicting coating lifetime under multifield service conditions and optimizing interfacial adhesion to prevent delamination. Future efforts should prioritize multifunctional coating designs, improved tribocorrosion models, and the integration of sustainable materials and AI-driven process optimization. This review consolidates these insights to support the development of next-generation coatings for extending the service life of steel components across demanding sectors such as marine, aerospace, and energy systems. Full article

Cold-spray additive manufacturing (CSAM) is an emerging solid-state deposition technology that effectively mitigates common defects associated with conventional thermal processes, such as oxidation, phase transformation, and residual stresses. In this study, copper–titanium (Cu-Ti) composite coatings were fabricated via high-pressure CSAM using mixed powders with Ti contents of 3, 6, and 10 wt.%. The influence of Ti content and post-heat treatment (350–400 °C) on the tensile properties of the composites was systematically investigated. The results indicate that the ultimate tensile strength (UTS) remained consistently within the range of 265–285 MPa under all conditions, showing only a mild positive correlation with Ti content. In contrast, ductility was significantly influenced by Ti addition, with elongation decreasing markedly as the Ti content increased. Notably, the composite with 3 wt.% Ti heat-treated at 400 °C exhibited a well-balanced combination of tensile strength (270 MPa) and ductility (20% elongation). These findings demonstrate that CSAM-fabricated Cu-Ti composites possess attractive mechanical properties, which can be tailored through Ti content and heat treatment. Full article

Composites based on the AlSi12 aluminum alloy reinforced with Saffil^TM fibers (Composite I) and with both Saffil^TM fibers and nickel-coated graphite flakes (Composite II) were developed using the squeeze casting method in the fabrication process. The objective of this work was to evaluate the influence of the employed reinforcements on the mechanical properties and corrosion behavior of the obtained materials. To achieve this, investigations were conducted, including SEM analysis, flexural strength testing, Brinell hardness testing, linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Corrosion measurements were performed in a 3.5% NaCl solution at room temperature. Mechanical investigations revealed a significant increase in flexural strength and hardness for Composite I compared to the plain matrix alloy. In contrast, Composite II’s flexural strength was reduced by the weakening effect of graphite flakes. Performance under bending improved by 46% for Composite I and 25% for Composite II compared to the AlSi12. The corrosion resistance of the tested materials followed the order AlSi12 > Composite I > Composite II. The LSV and EIS results indicate that the explanation for this may be differences in the properties of the protective oxide/hydroxide layer. Furthermore, SEM images showed a weak bond between nickel and graphite. Full article

This study employed atmospheric plasma spraying (APS) technology to successfully fabricate CoCrFeNiMo high-entropy alloy (HEA) coatings under varying spraying currents and systematically investigated the effects of the spraying current on the microstructure, mechanical properties, and tribological behavior of the coatings. Results showed that the material composition remained consistent across different current levels, primarily consisting of face-centered cubic (FCC) solid solution phases, FeCr₂O₄ spinel phases, and Cr-rich FCC1 phases. The FCC matrix was dispersed with spherical Cr oxide particles smaller than 30 nm in diameter, which significantly enhanced the strength of the coatings. As spraying current increased, both porosity and microhardness exhibited a non-monotonic trend—initial optimization followed by deterioration. At 500 A spraying current, the coating achieved optimal performance, with the lowest porosity (0.42%) and highest microhardness (569.8 HV). Correspondingly, this condition also yielded the best wear resistance, with stable friction coefficients and wear rates reaching 0.49 and 6.91 × 10⁻⁵ mm³/N m, respectively. Abrasion surface analysis revealed that excessively low or high currents triggered distinct wear mechanisms leading to reduced wear resistance. Full article

Yttrium oxide (Y₂O₃) is a crucial protective material for the inner walls of semiconductor etching chambers. This study employed Suspension Plasma Spray (SPS) technology to deposit Y₂O₃ coatings on AISI 304 stainless steel substrates. A water ring guide cover, which injects deionized water toward the center of the plasma flame at the torch outlet, was installed. The critical parameter ratio between the water ring flow rate and the suspension feed rate was investigated, with a specific focus on its influence on the coating’s microstructure and mechanical properties. The findings reveal that this parameter exhibits a significant positive correlation with porosity, with the coefficient of determination R² for their linear fit reaching 0.91236. When the water ring flow rate ratio was reduced to 79.66%, the porosity decreased to 0.946%, while the primary composition of the coating remained unchanged. Bond strength tests demonstrated that the adhesion strength of the coating exhibits an upward trend with increasing proportion of water ring flow. The adhesion strength reached its maximum value of 27.02 MPa when the water ring flow rate proportion was increased to 85.45%. Roughness exhibits a non-monotonic variation trend within the ratio range, attaining its optimal minimum value at the lower end of the ratio, indicating complex interrelationships among process characteristics. This work concludes that a low water ring flow rate ratio is essential for fabricating dense, well-adhered, and smooth Y₂O₃ coatings via SPS, providing a critical guideline for process optimization for applications such as semiconductor protection. Full article

Epoxy resin coatings are widely employed for steel protection owing to their excellent adhesion, chemical stability, mechanical strength, and barrier properties. However, conventional bisphenol A-based resins and organic solvents may pose risks to reproductive, developmental, and immune systems, as well as contribute to atmospheric pollution. This mini-review critically evaluates recent advancements in fully waterborne bio-based epoxy nanocomposites as sustainable alternatives, with particular emphasis on their enhanced antibacterial and corrosion-resistant performance in tropical marine environments. A central focus is the role of chitosan-grafted graphene oxide (Chi-GO) as a multifunctional nanofiller that significantly enhances both antibacterial efficacy and barrier capabilities. For instance, coatings reinforced with Chi-GO exhibit up to two orders of magnitude lower corrosion current density than pristine epoxy coatings, and achieve over 95% bacterial inhibition against Escherichia coli and Staphylococcus aureus at a 1 wt.% loading. The review summarizes key synthesis methods, functional modification techniques, and commonly adopted evaluation approaches. Emerging research further underscores environmental performance metrics, including reduced volatile organic compound (VOC) emissions and improved life-cycle assessments. By integrating bio-based polymer matrices with Chi-GO, these composite systems present a promising pathway toward environmentally benign and durable protective coatings. Nevertheless, critical challenges concerning scalability and long-term stability under real-world operating conditions remain insufficiently addressed. Future research should emphasize scalable manufacturing strategies, such as roll-to-roll processing, and conduct extended tropical exposure testing (e.g., salt spray tests beyond 2000 h). Additionally, developing comprehensive life-cycle assessment (LCA) frameworks will be crucial for sustainable industrial implementation. Full article

Titanium alloys are widely used in orthopedic and dental implants, yet their limited bioactivity and bacterial resistance remain critical challenges. This study aimed to enhance the surface performance of a Ti-13Zr-13Nb alloy through the formation of a porous oxide layer and the application of a bioactive, drug-loaded coating. Porous oxide layers composed of Ti, Zr, and Nb oxides with fluoride incorporation were fabricated using a novel anodizing process. The fluoride-assisted electrochemical mechanism controlling oxide growth was elucidated through SEM and EDS analyses. The anodized surface exhibited reduced microhardness, beneficial for minimizing stress-shielding effects. Subsequently, chitosan–tetracycline composite coatings were produced via EPD and compared with dip-coating method. Characterization by ATR-FTIR, optical microscopy, SEM, and UV-VIS spectroscopy confirmed the formation of uniform, adherent, and moderately porous coatings with sustained drug release when produced by EPD, while dip-coated layers were less homogeneous and released the drug faster. Microhardness testing revealed improved mechanical integrity of EPD coatings. The developed chitosan–tetracycline–oxide layer system provides tunable nano/microgram-scale drug release and enhanced surface functionality, offering promising perspectives for acute and medium-term regenerative and antibacterial biomedical applications. Full article

Antimony oxychloride compounds represent a distinct class of inorganic materials that combine structural features characteristic of both oxides and halides. Their compositional flexibility and anisotropic properties make them promising candidates for use in photocatalytic systems, optoelectronic devices, flame-retardant coatings, and energy storage technologies. This review provides an overview of the structural characteristics and synthesis strategies associated with key members of the Sb_xO_yCl_z family, including SbOCl, Sb₄O₅Cl₂, and Sb₈O₁₁Cl₂. Emphasis is placed on how synthesis parameters—such as temperature, pH, and precursor composition—govern phase formation, morphology, and resulting properties. Recent advances in composite engineering, controlled doping, and surface modification are discussed as effective routes to overcome limitations such as low conductivity and chemical instability. The broader significance of antimony as a strategic element is also addressed in the context of global resource availability and its role in sustainable technologies. Overall, these materials provide a versatile platform for the design of multifunctional systems tailored to meet future demands in materials science and applied engineering. Full article

Objective: The Ti6Al4V titanium alloy is widely used for dental implants because of its excellent mechanical properties, corrosion resistance, and biocompatibility. However, its bioinert surface limits both osseointegration and resistance to bacterial colonization. Methods: To address these challenges, this study develops a composite coating based on calcium phosphate (CaP) and silver (Ag), reinforced with zirconium oxide (ZrO₂). The coating was deposited on Ti6Al4V using an immersion technique to improve the surface properties of the alloy. Electrochemical analyses (OCP, EIS, and potentiodynamic polarization) were performed in simulated physiological conditions to evaluate the corrosion behavior, while SEM/EDS was used to characterize the surface morphology and composition. Results: The Ag- and Zr-containing CaP coatings significantly improved the corrosion resistance of Ti6Al4V compared with uncoated and CaP-coated samples. Conclusions: This approach provides a promising strategy to enhance the electrochemical stability and long-term durability of titanium dental implants, thereby contributing to their reliable performance in the oral environment. Full article

Traditional Fe-based materials are limited for Cr(VI) remediation due to low reactivity, oxidation, and aggregation. Although chitosan coatings improve stability, they hinder efficient liquid-solid separation. To overcome this, a novel phosphorus-modified magnetic chitosan adsorbent (PCC/Fe₃O₄) was synthesized using Fe₃O₄ as the core and tetrakis hydroxymethyl phosphonium sulfate (THPS) as a cross-linking agent. The composite exhibited a high surface area (20.67 m²/g) and superparamagnetism, enabling easy magnetic recovery. PCC/Fe₃O₄ demonstrated superior Cr(VI) removal capabilities compared to unmodified chitosan and raw Fe₃O₄, achieving a saturated adsorption capacity of 23.6 mg/g under the selected conditions (pH 6, initial Cr(VI) concentration of 1 mg/L), which were chosen to balance adsorption efficiency, adsorbent stability, and environmental relevance. The main removal mechanism includes electrostatic attraction, redox reaction, and ligand exchange. PCC/Fe₃O₄ maintained 86% efficiency after 5 d aging and >90% efficiency after five cycles, demonstrating excellent stability and reusability and strong potential for practical environmental remediation. Full article

Graphene oxide (GO) was prepared by a waterless synthesis route to generate GO sheets, which were then applied to coat calcined oyster shell with fertilizer (OSF) pellets, resulting in the creation of an OSF-GO particle. The GO sheets (ID/IG = 0.86) were characterized by Raman spectroscopy, which showed that the GO-coated OSF pellet features a compact coating approximately 13.68 μm thick. SEM and AFM analyses revealed that the GO sheets displayed a monolayer configuration with a crinkled topography (about 0.91 nm). The EDS analysis confirmed that the core was primarily composed of Ca, K, P, O, N, and C elements. The hydroponic experiment results showed that a GO concentration of 80 mg/L significantly enhanced plant height, stem thickness, and root length in loose-leaf lettuce, while higher concentrations induced oxidative stress. In pot experiments, the OSF-GO composite effectively raised the soil pH from 5.38 to 6.41 and improved nutrient availability. OSF-GO composite functions effectively as both a soil conditioner and slow-release fertilizer (SRF), simultaneously remediating degraded soils and optimizing nutrient delivery. Full article

Nickel–tungsten carbide (Ni/WC) multi-pass fused cladding layers with different cerium (IV) oxide (CeO₂) contents were applied to Cr12MoV cold work tool steel surfaces using the coaxial powder feeding method for laser cladding. Scanning electron microscopy, energy spectrum analysis, X-ray diffraction, and wear experiments were conducted to study how adding CeO₂ to change the properties of WC-reinforced Ni-base composite coatings in turn alters the microstructure and properties of Cr12MoV cold work tool steel. The results show that laser cladding is effective when the process parameters are as follows: a power of 1500 W, a 24 mm defocusing distance, a 6 mm/s scanning speed, a 5 mm spot diameter, and a powder delivery of 0.1 g/s. Laser-fused cladding coatings are mainly composed of dendrites, crystalline cells, strips, and bulk microstructures. The addition of CeO₂ is effective at improving the microstructure and morphology of the coating—the size and distribution of the reinforcing phase change very significantly, and the shape changes from irregular and lumpy to spherical. With a 2% CeO₂ content, the enhanced phase, now spherical and white, is more diffusely distributed in the tissue. The maximum microhardness of the composite-coated specimen after the addition of CeO₂ is about 986 HV, which is approximately 20% higher than the hardness of the composite coating with no CeO₂ added. Full article

This study investigates the fabrication of anodic aluminum oxide (AAO)/Al bilayer films using a two-step aluminum anodization process and explores the perception and prediction of structural colors through these films. A composite AAO film with an AAO/Ni/Al structure was fabricated by electroplating an AAO/Al bilayer film with an AAO/Al structure. The fabricated composite AAO film was used to produce structural colors through changes in optical characteristics caused by Ni nanoplugs. Constructive-interference wavelengths resulting from variations in the pore diameter and interpore distance of AAO/Al bilayer films and composite AAO films were predicted using the Bragg–Snell law, with a maximum error margin of 9%. Additionally, the composite AAO film exhibited RGB colors within the predicted constructive-interference wavelength range. These results demonstrate that structural colors can be reliably predicted by estimating the constructive-interference wavelengths of composite AAO films. The approach provides a practical design rule for target colors in AAO-based coatings under normal incidence. The key advance is a single closed-form rule that links D_t, D_int, D_P, and D_ni to λ_{_peak} at normal incidence, enabling forward and inverse color design without numerical optimization. Full article