Search Results (3,269)

Among different non-carbon materials, due to their high corrosion resistance and chemical stability, titanium-based compounds, such as TiO₂, TiN, TiC and Ti₃C₂T_x, are potential supports for PEMFC catalysts. In addition to its main function as a support, due to its catalytic properties, TiO₂ is also used as co-catalyst/additive in the catalyst layer. In this work, the use of titanium compounds as catalyst supports and co-catalysts in the membrane electrode assembly of PEMFCs is overviewed and discussed. Full article

Tube boilers are extensively employed in oil and gas refineries, as well as in petroleum, energy, and power generation industries, where they serve critical functions in local steam-generation units and combined-cycle gas turbine (CCGT) plants. However, these boilers are prone to defects arising from waterside corrosion (e.g., thinning of U-bend tubes), fireside corrosion, and material degradation caused by stress or creeping. Among these issues, wall thinning of tube bends is particularly severe, as it results in localized metal loss, reduced structural integrity, and an elevated risk of tube rupture or failure under high-temperature and high-pressure operating conditions. Such failures can significantly compromise boiler safety and efficiency, potentially leading to forced outages, costly unplanned repairs, or catastrophic damage if not detected in time. The current condition-monitoring policy for U-bends relies on scheduled preventive maintenance and unscheduled corrective interventions. In practice, this involves randomly checking approximately 10–20% of the tubes through spot scanning, partial scanning, or full scanning, with repairs typically carried out only after an undetected failure occurs. Such maintenance strategies generally require plant shutdowns, making the process time-consuming, labor-intensive, and ultimately not cost-effective. This paper reviews existing solutions, technologies, and research addressing the problem, and introduces femtosecond laser micromachined fiber optic sensors as a transformative approach for real-time monitoring of wall thickness reduction in U-bend boiler tubes, thereby opening pathways for further research. Full article

This study investigates the hydrogen embrittlement susceptibility of laser melting deposition (LMD)-produced Ti-6Al-4V alloy with different build orientations (0°, 45°, 90°) through electrochemical hydrogen charging, slow strain rate testing, and microstructural characterization. Ti-6Al-4V alloys are widely used in marine and offshore engineering, where cathodic protection and corrosion reactions can generate hydrogen, leading to hydrogen ingress and potential embrittlement. Results show that prolonged hydrogen charging induces hydride formation, α-phase fragmentation, and β-phase dissolution, significantly degrading corrosion resistance and mechanical properties. Hydrogen embrittlement susceptibility exhibits notable anisotropy: elongation reductions for 0°, 45°, and 90° specimens are 40.1%, 40.8%, and 29.4%, respectively. The relatively superior resistance observed in the 90° orientation may be associated with its single-layer structure and more uniform dimple distribution. In contrast, the multilayer interfaces in other orientations are likely to serve as preferential sites for hydrogen accumulation, which may contribute to the increased embrittlement susceptibility. This research reveals the failure mechanism of LMD Ti-6Al-4V in hydrogen environments and supports its application in marine engineering. Full article

Aramid fiber is a high-performance fiber with excellent mechanical properties, heat resistance, and corrosion resistance. Its exceptional shear and fatigue properties make it a promising material for civil engineering applications. This study summarizes the basic properties and current development of aramid fiber, as well as the applications of aramid fiber and its composites in civil engineering, including aramid fiber-reinforced composite (AFRP)-concrete/steel composite structures, AFRP rebars, and AFRP rock anchors. The results indicate that the poor interfacial bonding performance between aramid fibers and the resin matrix is the primary bottleneck restricting the application of AFRP composites in civil engineering. Consequently, developing a continuous surface treatment method suitable for industrial-scale production remains a key challenge for the widespread adoption of these composites. Furthermore, in certain specific working conditions and environments—such as seismic retrofitting of rectangular concrete columns, impact/explosion resistance reinforcement, and rock anchoring—AFRPs show the potential to replace traditional inorganic fiber-reinforced polymer composites. However, systematic investigation into the fundamental mechanical properties and long-term service performance of AFRP is still required prior to their practical application. Full article

The production of green hydrogen via aqueous electrolysis of hydrogen sulfide (H₂S) holds significant potential to address challenges related to sustainable energy generation and environmental protection. The electrocatalytic splitting of water polluted with highly toxic H₂S is attractive for industrial applications because the process: (i) is less power-consuming than direct thermal H₂S decomposition; (ii) achieves high Faradaic efficiencies for hydrogen production; and (iii) yields elemental sulfur as an added-value by-product. This review covers a brief discussion on sulfide-containing water sources and electrochemical methods for hydrogen production from H₂S, specifically Direct, Indirect, and Electrochemical Membrane Reactor (EMR) systems. To become commercially and economically attractive, these approaches require improvements in electrolysis efficiency through the development of low-cost electrode materials that are resistant to sulfur poisoning and corrosion, while possessing high catalytic activity, enhanced stability, and durability. Early research focused on carbon-based materials combined with noble metal oxides, transition metal compounds, and related materials. Since their practical performance is limited, investigations have shifted toward nanostructured electrocatalysts with unique crystal structures and designs, which show significantly improved efficiency for H₂S electrolysis. This review highlights the potential of H₂S electrolysis for hydrogen production, giving special attention to recent advancements in electrode materials. Full article

Diamond-like carbon (DLC) coatings are increasingly explored as a practical route to enhance the surface performance of biomedical implants and tissue engineering scaffolds, particularly when combined with additive manufacturing. Rather than serving only as protective layers, DLC coatings allow for independent tuning of surface properties without modifying the bulk structure, which is especially relevant for complex 3D-printed components. This flexibility is often what makes them attractive for biomedical design. This review is structured around two main application areas: DLC coatings for prosthetic implants and DLC coatings for tissue engineering scaffolds. Within this context, the influence of DLC structure (e.g., sp²/sp³ bonding, hydrogen content, and doping) on mechanical, tribological, and biological behavior is discussed. Particular attention is given to additively manufactured metallic implants and porous scaffolds, where large surface area and internal architectures complicate coating uniformity and adhesion. Reports show that DLC coatings can improve corrosion resistance, reduce wear, and influence biological responses, such as antibacterial activity and cell interactions. Several challenges remain to be solved, especially in achieving uniform coating penetration in porous networks and in ensuring long-term stability under physiological conditions. The combination of additive manufacturing and DLC coatings has been shown to offer the potential to become an enabling technology for next-generation biomedical devices. Full article

Surface protection and functional modification of aircraft-certified aluminum alloys are essential for corrosion resistance, durability, and long-term airworthiness. At the same time, increasingly restrictive environmental regulations motivate the development of alternatives to legacy wet-chemical surface treatments. This study presents an integrated assessment of ultrafast femtosecond laser surface texturing as a surface functionalization approach for Aluminum 6061 alloys within an aerospace manufacturing and sustainability context. Ultrashort-pulse laser processing enables controlled micro- and nano-scale surface topographical modification with limited thermal impact, allowing adjustment of wettability and surface functionality while preserving bulk material integrity. As a dry and contactless process, femtosecond laser treatment eliminates the use of hazardous chemicals, reduces consumable inputs, and generates minimal secondary waste. A streamlined cradle-to-gate life cycle assessment conducted in accordance with ISO 14040/14044 indicates a lower global-warming potential per functional unit compared with conventional surface treatments, including anodization, plasma-assisted coatings, and organic coating systems. Complementary qualitative analyses addressing environmental health and safety, supply-chain risk, and ESG alignment indicate potential advantages related to occupational safety, regulatory compliance, waste management, and end-of-life recyclability. The investigation is performed on planar Aluminum 6061 reference surfaces with a treated area of 25 mm², providing a controlled laboratory-scale basis for analyzing process behavior, functional surface modification, and associated environmental metrics. Within this defined scope, the results support further evaluation of femtosecond laser surface texturing as a surface engineering option for future aerospace manufacturing. Full article

In nuclear power, marine engineering, and other fields, a matching system composed of duplex steel and copper alloy is a common combination for rotating components in a seawater environment. However, this system is susceptible to galvanic corrosion that seriously threatens its service safety and service life, with ZCuAl10Fe5Ni5 being the main component corroded. Additionally, current corrosion research on this system has evident gaps. Specifically, the influence of area ratio on galvanic corrosion remains insufficiently understood, and the action mechanism of Cl⁻ on the ZCuAl10Fe5Ni5-based corrosion product film in seawater, as well as the product evolution path, has not been fully revealed, which restricts the development of targeted protection technologies. This study explores the degradation mechanism of ZCuAl10Fe5Ni5 in a specific high-salinity environment (20,000 mg/L Cl⁻), characteristic of nuclear power plant service conditions. The results show that due to the significant electrode potential difference between the SAF2507 duplex steel and ZCuAl10Fe5Ni5 copper alloy, a stable galvanic couple is formed, with ZCuAl10Fe5Ni5 acting as the anode and undergoing dissolution corrosion. When the area ratio of ZCuAl10Fe5Ni5 (anode) to SAF2507 duplex steel (cathode) is 1:50, a significantly stronger galvanic effect is observed. The high concentration of Cl⁻ in seawater can damage the surface of the ZCuAl10Fe5Ni5-based corrosion product film, leading to intensified local corrosion. The ZCuAl10Fe5Ni5-derived corrosion products have a layered structure mainly comprising a mixed system of Cu-Al-Mg oxides/hydroxides, and the corrosion process is accompanied by selective aluminum depletion corrosion. This study provides insight into the corrosion mechanism and key influencing factors of ZCuAl10Fe5Ni5 in the matching system, as well as a theoretical basis and technical support for the design of compatibility metal materials in a seawater environment and the control of corrosion in ZCuAl10Fe5Ni5. Full article

Models are described for calculating the crack initiation times for Alloy 600 and Type 304 SS in PWR and BWR primary coolant circuits, respectively. In PWRs, initiation is defined in terms of the grain boundary oxidation concept of Scott and Le Calvar, whereas in BWRs, cracks are envisioned to nucleate from corrosion pits. In contrast, in BWRs, we envision cracks to nucleate from corrosion pits, with the difference in the two systems being primarily due to electrochemical factors. Thus, in BWR primary coolant and the absence of hydrogen water chemistry (HWC), the oxidizing conditions due to the radiolytic production of H₂O₂ cause the ECP to be significantly more positive than the critical pitting potential. Accordingly, the nucleation and growth of pits due to passivity breakdown and the establishment of differential aeration between the pit nucleus’s internal and external environments, which results in growth of pits to the critical size necessary to satisfy the Kondo criteria for transition of a pit into a crack, is judged to be a realistic scenario. Contrariwise, in PWR primary coolant, the ECP is so negative [≈−1.0 V_she] due to the large amount of pressurizing H₂ present in the circuit [20–60 cm³(STP)/kg H₂O] that the nucleation and growth of pits is not possible. However, Totsuka and Smialowska found that MA Alloy 600 suffers hydrogen-induced cracking (HIC) at an ECP < −0.85 V_she, demonstrating that, in service with a high hydrogen concentration, brittle fractures will occur. The initiation sites were not identified. The crack initiation models for Alloy 600 in PWRs and Type 304 SS in BWRs reproduce the effects of the following independent variables: applied stress, temperature, cold work, grain boundary segregations, water chemistry, pH, and electrochemical potential. The origins of the observed scatter in experimentally measured crack initiation times are discussed, and the challenges of developing a more general crack initiation model (GCIM) are identified. From a mathematical viewpoint, the most significant challenge arises from the nested distributions involving the many parameters and expressions within the GCIM that are either distributed because of an imprecise definition or because some experimentally determined input parameters are experimentally scattered. Additionally, the evolution of semi-elliptical surface cracks resulting from the electrochemical crack length (ECL) being shorter than the classical mechanical crack length (MCL) must be incorporated if the GCIM is to find utility in the water-cooled nuclear power industry where semi-elliptical surface cracks are normally observed. Full article

Wire arc additive manufacturing (WAAM) is an efficient, low-cost technique for fabricating large-scale metallic components and, in particular, functionally graded materials (FGMs). This review focuses on the fabrication of 316L stainless steel–Inconel 625 FGMs by arc-based WAAM processes, examining Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW) in terms of their microstructural outcomes, compositional control strategies, residual stress development and mechanical performance. A critical finding emerging from the reviewed literature is that direct compositional interfaces between 316L and Inconel 625 can yield superior tensile strength and ductility and lower residual stresses compared to smooth gradient strategies, owing to the formation of detrimental secondary phases such as δ-phase, Laves phase and MC carbides at intermediate iron–nickel compositions encountered only during graded builds. The potential of Submerged Arc Additive Manufacturing (SAAM) as a future high-deposition-rate alternative for large-scale FGM fabrication is also discussed. Key challenges, including dilution control, Laves phase formation, residual stress management and the corrosion characterization of the graded region, are identified, together with priority research directions for advancing the industrial adoption of arc-based FGM components. Full article

In marine service environments, material surfaces inevitably suffer from wear damage, which can compromise the integrity of protective coatings and further affect their corrosion resistance. Therefore, investigating the post-wear corrosion resistance of coatings is of great significance. In this work, single-layer CrN coatings, CrAlN coatings, and CrN/CrAlN multilayer coatings were deposited on stainless-steel substrates by arc ion plating, and the microstructure, tribological properties, and corrosion behavior before and after wear were systematically investigated. Wear tests were performed under applied loads of 2.5 N and 5 N. The corrosion behavior in the unworn condition and the post-wear corrosion resistance condition was evaluated in a 3.5 wt.% NaCl solution. The results showed that all coatings exhibited a face-centered cubic (FCC) structure, while the CrN/CrAlN multilayer coating possessed the smallest average grain size (13.47 nm). Under applied loads of 2.5 N and 5 N, the CrN/CrAlN multilayer coating exhibited the lowest wear rate, indicating the best wear resistance. In the unworn condition, the CrN/CrAlN multilayer coating showed the lowest corrosion current density (2.74 × 10⁻¹⁰ A/cm²) and the most positive corrosion potential (0.025 V), demonstrating the best corrosion resistance. After wear under a load of 5 N, the CrN/CrAlN multilayer coating retained a low corrosion current density (3.35 × 10⁻¹⁰ A/cm²), in contrast to the marked increases observed for the single-layer coatings. The enhanced performance is considered to be mainly associated with the periodic heterogeneous interfaces in the multilayer structure, which help suppress crack propagation and prolong the penetration path of corrosive media. Full article

Additive manufacturing (AM) using powder bed fusion (PBF) has been the predominant printing method used over the last decade. The capability of this approach to produce complex parts with high precision has attracted the attention of major industries as a potential tool for replacing traditional manufacturing technologies. 15-5 PH stainless steel is one of the alloys being studied as a candidate for PBF processes. Its superior strength and corrosion resistance have made it a highly attractive option in numerous industries, including the automotive, nuclear, and petrochemical industries. To enhance the properties of 15-5 PH stainless-steel AM parts following printing, one can use a thermal treatment such as age hardening. However, very little research exists regarding the functional properties of AM parts made from this alloy after heat treatment. This study aims to evaluate the effect of H1150M age hardening heat treatment following printing on the properties of 15-5 PH steel, particularly regarding its mechanical properties and environmental behavior. The microstructure was studied using both optical and electron microscopy, along with X-ray diffraction (XRD) analysis. The mechanical properties were examined by tensile testing and fracture toughness assessment. Corrosion behavior was analyzed in terms of potentiodynamic polarization and using impedance spectroscopy. The results obtained have shown that over-aging caused by H1150M heat treatment has a detrimental effect on the mechanical and environmental behavior of the tested alloy. This was primarily attributed to the formation of an austenitic phase within the inherent martensitic matrix, the generation of brittle phases (mainly carbonitrides of Cr and Nb) and a reduction in grain size. Full article

Marine biofouling is a major global concern affecting the marine industry, the environment, and public health. The accumulation of organisms on submerged surfaces causes significant economic losses, including increased fuel consumption, higher pollutant emissions, and accelerated corrosion. Antifouling (AF) coatings with biocides are widely used to prevent this problem. However, many conventional biocides have been banned due to toxicity, creating an urgent need for environmentally friendly alternatives. In previous studies, we synthesized a gallic acid derivative and three flavonoids that showed AF activity against the settlement of mussel larvae (Mytilus galloprovincialis) together with low ecotoxicity. In the present work, to further assess their potential in marine coatings and exploit the advantages of nanocarriers in protecting and prolonging bioactive effects, these compounds were loaded into halloysite nanotubes (HNTs) and incorporated into epoxy coatings. Coatings containing the same AF compounds in free form were also prepared for comparison. HNTs were characterized by scanning electron microscopy (SEM), and compound loading was quantified by thermogravimetric (TG) analysis. The resulting composites were analyzed by SEM and dynamic water contact angle measurements. Laboratory bioassays with M. galloprovincialis larvae showed that coatings containing HNT-loaded synthetic compounds generally reduced larval settlement more effectively than the corresponding coatings containing the same compounds directly dispersed in the epoxy matrix, with values below 20% after both 15 and 40 h of exposure for the best-performing formulation. These findings highlight the novelty of the proposed HNT-based delivery strategy for nature-inspired synthetic antifoulants and support its potential for the development of effective and environmentally safer AF coatings. Full article

The precipitation characteristics and grain-boundary structure of Al–Cu–Mg alloys strongly affect their corrosion behavior, whereas the roles of Si and Ag microalloying in low Cu/Mg ratio systems are not yet fully understood. In this work, the effects of Si and Ag additions on age-hardening response, precipitation characteristics, and corrosion performance were systematically investigated by combining transmission electron microscopy with electrochemical and corrosion measurements. Si addition significantly accelerated the age-hardening kinetics, enabling the alloy to reach a hardness of 147 HV after only 6 h of aging, whereas the base alloy required 24 h to reach a similar level. This accelerated response was accompanied by refined S-phase precipitation and a markedly narrowed precipitation-free zone along grain boundaries. Further Ag addition introduced coherent Ω precipitates and a more complex multi-phase precipitation structure, which increased microstructural heterogeneity. As a result, the Al–Cu–Mg–Si alloy exhibited the lowest corrosion current density and the shallowest corrosion depth, whereas the Al–Cu–Mg–Si–Ag alloy showed deteriorated corrosion resistance. These results indicate that Si microalloying alone can simultaneously accelerate aging and improve corrosion resistance, while further Ag addition enhances precipitation complexity and strengthening potential but increases susceptibility to localized corrosion. Full article

This study reports that titanium nanoparticles can be used as a surface coating to enhance the corrosion resistance of 316 stainless steel. It specifically examines the influence of the deposition temperature (T_dep) on the coating’s structural and morphological properties, including corrosion behavior. TiO₂ nanoparticles were thoughtfully deposited on steel substrates at temperatures of 300, 400, and 500 °C using a horizontal hot-wall tubular reactor. This equipment was expertly engineered at the CIDETEQ laboratory through the metal–organic chemical vapor deposition (MOCVD) concept. Titanium isopropoxide [Ti(OC₃H₇)₄] was used as the precursor for the coating synthesis. Structural analysis was conducted using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Corrosion performance was evaluated under accelerated conditions in 0.5 M H₂SO₄ using potentiodynamic anodic polarization (AP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The corrosion test indicates that increasing T_dep significantly differentiates the coating morphology and improves corrosion resistance. AP revealed that the pitting potential (E_pit) shifted to more positive values, ranging from +1.4 to +1.5 V. CV voltammograms indicated that coated samples had lower passive current densities (I_p ≈ 10⁴ to 10⁵ A/cm²) than the bare substrate. EIS analysis demonstrated that the coating deposited at 500 °C processed the most favorable electrochemical performance, resisting corrosion for over 28 days. This coating achieved the highest electrical resistance (297 kΩ·cm²) and the lowest capacitance (2.7 μF/cm²), attributed to the formation of a crystalline anatase phase composed of pyramidal-like nanoparticle agglomerates (~40 nm). The dense packing structure effectively blocks charge-transfer pathways, restricting electron and ion transfer. Finally, MOCVD-based chemical surface modification with TiO₂ nanoparticles is considered an innovative method to improve the corrosion resistance of stainless steel, thereby prolonging its durability under accelerated sulfuric acid exposure. Full article