Search Results (5,262)

Silicon carbide (SiC) ceramics have gained significant attention in advanced engineering applications because of their superior mechanical properties, resistance to wear and corrosion, and thermal stability. However, the precision machining of these materials is extremely challenging because of their intrinsic hardness and brittleness. Wire Electrical Discharge Machining (WEDM) has become increasingly popular as a viable technique for processing SiC ceramics because of its ability to produce intricate geometries and high-quality surface finishes. In this review paper, a comprehensive overview of WEDM technology applied to SiC ceramics is presented, emphasizing the influence of process parameters, wire materials, and dielectric fluids on cutting efficiency and quality. This research explores recent experimental findings related to Wire Electrical Discharge Machining (WEDM) and highlights the challenges in reducing material damage. It also presents strategies to improve machining performance. Additionally, potential future directions are discussed, providing a roadmap for further research and the application of WEDM in processing silicon carbide (SiC) and its variants, including solid silicon carbide (SSiC) and silicon-infiltrated silicon carbide (SiSiC). Full article

Polytetrafluoroethylene (PTFE) is one of the alternative materials suitable for seawater-lubricated bearings, favored for its excellent corrosion resistance and good self-lubricating properties. As marine equipment develops towards higher load, higher reliability, and longer service life, more stringent requirements are imposed on the wear resistance of bearing materials. However, traditional PTFE materials struggle to meet the performance requirements for long-term stable operation in modern marine environments. To improve the wear resistance of PTFE, this study used alumina (Al₂O₃) particles with three different particle sizes (50 nm, 3 μm, and 80 μm) as fillers and prepared Al₂O₃/PTFE composites via the cold pressing and sintering process. Tribological performance tests were conducted using a ball-on-disk reciprocating friction and wear tester, with Cr12 steel balls as counterparts, under an artificial seawater lubrication environment, applying a normal load of 10 N for 40 min. The microstructure and wear scar morphology were characterized by scanning electron microscopy (SEM), and mechanical properties were measured using a Shore hardness tester. A systematic study was carried out on the microstructure, mechanical properties, friction coefficient, wear rate, and limiting PV value of the composites. The results show that the particle size of Al₂O₃ particles significantly affects the mechanical properties, friction coefficient, wear rate, and limiting PV value of the composites. The 50 nm Al₂O₃/PTFE formed a uniformly spread friction film and transfer film during the friction process, which has better friction and wear reduction performance and load bearing capacity. The 80 μm Al₂O₃ group exhibited poor friction properties despite higher hardness. The nanoscale Al₂O₃ filler was superior in improving the wear resistance, stabilizing the coefficient of friction, and prolonging the service life of the material, and demonstrated good seawater lubrication bearing suitability. This study provides theoretical support and an experimental basis for the design optimization and engineering application of PTFE-based composites in harsh marine environments. Full article

H13 steel, which was used as the material for shield machine cutter rings, required tempering to attain superior mechanical properties. The Cr-rich carbide that precipitated during the tempering process definitely decreased the corrosion resistance of the steel. Here, we added rare earth Yttrium to enhance the corrosion resistance of H13 steel. It was found that the inclusions were modified by adding yttrium in the steel, and the formation of Cr₂₃C₆ at the grain boundaries during tempering was suppressed. Furthermore, SKPFM measurements demonstrated that the surface potential of yttrium-containing inclusion was comparable to that of the surrounding matrix, thereby reducing the pitting susceptibility of H13 steel. Further investigation showed that yttrium decreased the normal stress range at grain boundaries during the tempering process, and effectively prevented C segregation. Thus, the number of Cr-depleted zones was decreased, and grain boundaries with active Cr atoms were increased. These active Cr atoms effectively sealed the ion channels between the matrix and NaCl solution within the Cr-rich oxide layer, thus improving localized corrosion resistance in the NaCl solution. On the other hand, the electrochemical test and SKPFM exhibited that yttrium reduced the potential loss during tempering, minimized the potential degradation of the matrix, and improved the corrosion resistance of H13 steel with yttrium. Accordingly, the corrosion loss of Y-bearing H13 steel was reduced by 46.6%. Full article

Protective coatings are essential for extending the service life of components exposed to harsh conditions, such as pipes used in industrial systems, where wear and corrosion remain constant challenges. This study explores the development of a nano-sized TiO₂-reinforced electroless nickel-based ternary (Ni-W-P) alloy and composite coating on API X60 steel, a high-strength carbon steel pipe grade widely used in oil and gas pipelines, using an alkaline hypophosphite-reduced bath. The surface morphology, microstructure, elemental composition, structure, phase evolution, adhesion, and roughness of the coatings were analyzed using optical microscopy, FESEM, EDS, XRD, AFM, cross-cut tape test, and 3D profilometry. The tribological performance was evaluated via Vickers microhardness measurements and reciprocating wear tests conducted under dry conditions at a 5 N load. The TiO₂ nanoparticle-reinforced composite coating achieved a consistent thickness of approximately 24 µm and exhibited enhanced microhardness and reduced coefficient of friction (COF), although the addition of nanoparticles increased surface roughness (S_a). Annealing the electroless composites at 400 °C led to a significant improvement in their tribological properties, primarily owing to the grain growth, phase transformation, and Ni₃P crystallization. XRD analysis revealed phase evolution from an amorphous state to crystalline Ni₃P upon annealing. Both the alloy and composite coatings exhibited excellent adhesion performances. The combined effect of TiO₂ nanoparticles, tungsten, and Ni₃P crystallization greatly improved the wear resistance, with abrasive and adhesive wear identified as the dominant mechanisms, making these coatings well suited for high-wear applications. Full article

Reinforced concrete structures in harsh environments are highly vulnerable to structural damage caused by rebar corrosion. However, there remains a critical shortage of high-performance, environmentally friendly repair materials that integrate both structural restoration and long-term corrosion protection functionalities to address this issue. To meet this demand, this study innovatively developed an eco-friendly, high-performance repair material using lotus leaf extract (LLE)-modified mortar and systematically evaluated its corrosion protection performance and mechanisms under chloride attack conditions. The primary chemical constituents of LLE include alkaloids and flavonoids, rich in polar functional groups such as O–H, N–H, and C–O. The LLE modifier increased the fluidity of fresh cement paste, thereby improving its construction workability. A low dosage of LLE modifier promoted cement hydration. When the LLE dosage was 0.2 wt%, the 7-day and 28-day flexural strengths of the LLE-modified mortar increased by 16.8% and 7.48%, respectively, compared to those of unmodified mortar, while the compressive strengths increased by 30.6% and 14.5%, respectively. The LLE-modified mortar demonstrated significant protection against chloride corrosion, effectively inhibiting rebar corrosion. Electrochemical corrosion results indicated that compared to unmodified mortar, the modified mortar containing 0.5 wt% LLE exhibited an 80% improvement in protection efficiency against chloride corrosion. These results demonstrate that an appropriate dosage of LLE modifier can simultaneously optimize the fundamental properties of mortar and provide excellent chloride corrosion protection. Therefore, LLE-modified mortar shows promising application potential in integrated repair and corrosion protection engineering for reinforced concrete structures. Full article

In industrial production, flue gas heat exchangers are often affected by the low-temperature condensation of industrial flue gas due to the influence of the working environment, resulting in serious ash deposition and corrosion. In order to solve this problem, in this study, we developed an ash deposition and corrosion monitoring system to compare the ash deposition prevention performance and corrosion resistance of different materials, as well as its influence on the heat transfer performance of different materials in the same environment. The following coatings were selected for the experiment (values in parentheses are the concentrations of the added compounds): ND, Q235, 316L, Ni-Cu (0.4 g/L)-P, Ni-P-SiO₂ (40 g/L), Ni-Cu (0.4 g/L)-P-SiO₂ (20 g/L), Ni-Cu (0.4 g/L)-P-SiO₂ (40 g/L), and Ni-Cu (0.4 g/L)-P-SiO₂ (60 g/L). The results show that the Ni-Cu (0.4 g/L)-P-SiO₂ (40 g/L) coating has excellent corrosion resistance, while the Ni-Cu (0.4 g/L)-P-SiO₂ (60 g/L) coating shows excellent antifouling performance. Through the comparative analysis of polarization curves, impedance spectra, and coupled corrosion experiments, the test materials were ranked as follows based on their corrosion resistance: 316L > Ni-Cu-P-SiO₂ (40 g/L) > Ni-Cu-P-SiO₂ (20 g/L) > Ni-P-SiO₂ > Ni-Cu-P-SiO₂ (60 g/L) > Ni-Cu-P > ND > Q235. It was also demonstrated that the new coated pipes were able to reduce the exhaust temperature below the dew point and maximize the recovery of energy from the exhaust gas. The acid–ash coupling mechanism of the coating in the flue gas environment was further analyzed, and an acid–ash coupling model based on Cu and SiO₂ is proposed. This model analyzes the effect of the coating under the acid–ash coupling mechanism. Using coated tubes in heat exchangers helps to recover waste heat from coal-fired boilers, enhance heat exchange efficiency, extend the service life of heat exchangers, and reduce costs. Full article

High strength and high ductility concrete (HSHDC) exhibit exceptional compressive strength (up to 90 MPa) and remarkable tensile ductility (ultimate tensile strain reaching 6%), making them highly resilient under impact loading. To elucidate the influence of strain rate and wet–dry cycling of salt spray on the dynamic compressive response of HSHDC, a series of tests was conducted using a 75 mm split Hopkinson pressure bar (SHPB) system on specimens exposed to cyclic corrosion for periods ranging from 0 to 180 days. The alternating seasonal corrosion environment was reproduced by using a programmable walk-in environmental chamber. Subsequently, both uniaxial compression and SHPB tests were employed to evaluate the post-corrosion dynamic compressive properties of HSHDC. Experimental findings reveal that corrosive exposure significantly alters both the static and dynamic compressive mechanical behavior and constitutive characteristics of HSHDC, warranting careful consideration in long-term structural integrity assessments. As corrosion duration increases, the quasi-static and dynamic compressive strengths of HSHDC exhibit an initial enhancement followed by a gradual decline, with stress reaching its peak at 120 days of corrosion under all strain rates. All specimens demonstrated pronounced strain-rate sensitivity, with the dynamic increase factor (DIF) being minimally influenced by the extent of corrosion under dynamic strain rates (112.6–272.0 s⁻¹). Furthermore, the peak energy-consumption capacity of HSHDC was modulated by both the duration of corrosion and the applied strain rate. Full article

Thiosemicarbazones and thiocarbohydrazones are key sulfur-containing organic compounds known for their diverse biological, pharmaceutical, and industrial applications. Beyond their well-established therapeutic potential, their strong chelating ability allows them to form stable complexes with transition metals, enabling uses in catalysis, corrosion inhibition, and dyeing processes. Their structural characteristics and dynamic conformations critically influence both biological activity and industrial performance, making nuclear magnetic resonance (NMR) spectroscopy an indispensable tool for their analysis. This review provides a comprehensive overview of the conformational and functional properties of bioactive thiosemicarbazones and thiocarbohydrazones, with a focus on how experimental NMR techniques are used to investigate their conformational behavior. In addition to experimental findings, available computational data are discussed, offering complementary insights into their structural dynamics. The integration of experimental and theoretical approaches offers a robust framework for predicting the behavior and interactions of these compounds, thereby informing the rational design of novel derivatives with improved functionality. By highlighting key structural features and application contexts, this work addresses a critical gap in the current understanding of these promising agents across both biomedical and industrial domains. Full article

In this work, metal salts of phosphomolybdic acid were prepared and evaluated as catalysts in acetalization reactions of glycerol with furfural. These substrates have a renewable origin and play a crucial role in synthesizing bioadditives, which can enhance the physicochemical properties of fossil fuels and mitigate greenhouse gas emissions. Moreover, the biodiesel industry has generated a surplus of glycerol, and its use as a reactant is welcome from both economic and environmental viewpoints. Keggin heteropolyacid salts are less corrosive than traditional Brønsted acid catalysts and are easier to handle. Herein, metal phosphomolybdates were easily obtained from the acid precursor and metal chloride metathesis. A series of metal phosphomolybdates with the general formulae M₃[PMo₁₂O₄₀]_x n H₂O (M^x+ = Al³⁺, Fe³⁺, Co²⁺, Cu²⁺, Ni²⁺) was prepared and tested as catalysts in furfural glycerol acetalization reactions. Full article

In high-altitude corrosive environments, weathering steel is widely applied due to its excellent corrosion resistance. However, the welded joint regions, where the chemical composition and microstructure undergo changes, are susceptible to the corrosion-induced degradation of mechanical properties. This study investigates the corrosion–mechanical synergistic degradation behavior of a 16 mm thick Q500 qENH base metal and its V-type and Y-type welded joint specimens. Periodic immersion corrosion tests were conducted to simulate plateau atmospheric conditions, followed by mechanical performance evaluations. Corrosion metrics—including corrosion rate, cross-sectional loss, penetration depth, and corrosion progression speed—were analyzed in relation to mechanical indicators such as the fracture location, yield load, ultimate load, yield strength, and tensile strength at varying exposure durations. The results indicate that the corrosion process exhibits distinct layering, with a two-stage characteristic of rapid initial corrosion followed by slower progression. Welded joints consistently exhibit higher corrosion rates than the base metal, with the rate difference evolving nonlinearly in an “increase–decrease–stabilization” trend. After corrosion, the mechanical performance degradation of welded joint specimens is more severe than that of base metal specimens. Full article

To enhance the safe service performance of corrosion-resistant tank steel, it is of significant importance to develop novel materials characterized by both high strength-toughness and a low yield ratio. In this study, four experimental steels with a gradient of Mo content (0, 0.15 wt%, 0.30 wt%, and 0.60 wt% Mo) were prepared via thermomechanical controlled processing. The influence of Mo on the microstructural evolution and mechanical properties of the base metal was systematically investigated. The results revealed that when the Mo content was ≤0.15 wt%, the primary constituents of the matrix microstructure were polygonal ferrite, acicular ferrite, and granular bainitic ferrite. As the Mo content increased to 0.30 wt% and beyond, lath bainitic ferrite (LBF) emerged within the microstructure, and the size of the hard martensite/austenite constituents exhibited a refinement trend with increasing Mo content. Elevated Mo content enhanced the strength of the base metal, while the impact toughness initially increased and subsequently decreased. The equivalent grain size defined by misorientation tolerance angles of 2–6° contributed most significantly to the yield strength, as evidenced by its higher Hall–Petch fitting coefficient. The improvement in impact toughness was primarily attributed to the refinement of M/A constituents, which reduced crack initiation susceptibility, and the high density of high-angle grain boundaries (HAGBs) provided by the acicular ferrite. Conversely, the degradation in toughness was directly correlated with the coarsening of HAGB size and the reduction in HAGB density induced by the formation of LBF. Full article

Ice accretion on critical transportation infrastructure presents serious operational risks and economic challenges, highlighting the need for sustainable anti-icing solutions. This study develops a strong PDMS-based composite coating on aluminum by incorporating carbon nanotubes (CNTs) and carbon powder, effectively merging passive superhydrophobicity with photothermal capabilities. We systematically assess how different ratios of CNTs to carbon powder (3:1, 1:1, 1:3) influence surface morphology, wettability, anti-icing performance, mechanical durability, and corrosion resistance. The morphological analysis shows the formation of hierarchical micro/nano-structures, with the optimal 1:3 ratio (designated as P13) resulting in dense, porous agglomerates of intertwined CNTs and carbon powder. P13 demonstrates high-performing superhydrophobicity, with a contact angle of 139.7° and a sliding angle of 9.4°, alongside a significantly extended freezing delay of 180 s at −20 °C. This performance is attributed to reduced water–surface interaction and inhibited ice nucleation. Mechanical abrasion tests indicate remarkable durability, as P13 retains a contact angle of 132.5° and consistent anti-icing properties after enduring 100 abrasion cycles. Electrochemical analysis reveals exceptional corrosion resistance, particularly for P13, which achieves a notable 99.66% corrosion inhibition efficiency by creating a highly tortuous diffusion barrier that protects against corrosive agents. This multifunctional coating effectively utilizes the photothermal properties of CNTs, the affordability of carbon powder, the low surface energy of PDMS, and the thermal conductivity of aluminum, presenting a robust and high-performance solution for anti-icing applications in challenging environments. Full article

Metal nitride coatings have been considered as a promising approach to improve the performance of metal bipolar plates for proton exchange membrane fuel cells (PEMFCs). In this study, NbN_x coatings with three different ratios of N₂/Ar (1:2, 1:1 and 3:1) were prepared on TC4 alloy substrates using the double glow plasma alloying technology. The NbN_x coatings are homogeneous and dense, and the phase of the coating transforms from hexagonal β-Nb₂N to δ′-NbN phase as the nitrogen content increases. All coatings demonstrate high protective efficiency, with the coating (N₂/Ar ratio of 3:1) displaying the lowest current density of 8.92 × 10⁻⁶ A/cm² at a working voltage of 0.6 V. The EIS results also show that this coating has the best corrosion resistance. Notably, it also presents the lowest interfacial contact resistance of 7.29 mΩ·cm² at 1.5 MPa and good hydrophobicity. More importantly, this study provides a new idea and method for corrosion-resistant coatings of metal bipolar plates for PEMFC applications. Full article

The long-term durability of steel structures in contact with soil remains a critical challenge due to the complex and aggressive nature of many soil environments. This study presents a thorough evaluation of the corrosion resistance and microstructural evolution of Magnelis^® ZM430-coated steel exposed to highly aggressive, heterogeneous soils. Gravimetric analysis revealed that the Magnelis^® ZM430 coating exhibits low corrosion rates and enhanced initial barrier properties, even under severe soil conditions. Although the literature frequently reports that Zn–Al–Mg coatings outperform conventional hot-dip galvanized coatings, our results highlight that this superiority is not universal and may be limited under highly aggressive, heterogeneous soils. Microstructural characterization by optical microscopy, SEM/EDS, and XRD demonstrated that the as-received coating consists of a homogeneous layer with well-distributed Zn-, MgZn₂-, and Al-rich phases. Upon soil exposure, corrosion preferentially initiates in the Mg- and Al-rich interdendritic and eutectic regions, leading to selective phase depletion and localized breakdown of the protective layer. Despite these localized vulnerabilities, the overall performance of Magnelis^® ZM430 remains superior, especially during the early stages of exposure. While no direct comparisons were performed in this work, our findings align with previous literature reporting superior performance of Zn–Al–Mg coatings compared to conventional hot-dip galvanized coatings in similar environments. Importantly, the integration of precise corrosion rate data with detailed soil characterization enables accurate prediction of coating service life, allowing for optimized coating thickness selection and proactive maintenance planning. These findings underscore the value of combining advanced Zn–Al–Mg coatings with site-specific environmental assessment to ensure the long-term integrity of buried steel infrastructure. Full article

Current research on foamed lightweight soil primarily focuses on mechanical properties and durability, with few studies addressing its hydraulic characteristics and internal pore structure in road reconstruction applications. However, the material’s high porosity and low bulk density may significantly alter its mechanical properties and durability under prolonged rainwater exposure, highlighting the importance of investigating its hydraulic characteristics and internal foam structure. Based on the analysis of water absorption and bulk density in phosphogypsum-based foamed lightweight soil, this study further discusses the material’s softening coefficient and internal pore structure through systematic data comparison. Experimental results demonstrate that the unconfined compressive strength (UCS) of both dry and water-soaked specimens increases linearly with dry density. Notably, soaked specimens with 0.5 g/cm³ dry density achieve compliant 7-day UCS values while displaying a steeper strength increase compared to dry specimens. A dry density of 0.64 g/cm³ ensures a softening coefficient exceeding 0.75, confirming the material’s suitability for humid environments. The material contains predominantly small pores (90% ≤ 0.2 mm diameter), with improved bubble distribution at the edges and higher upper porosity. Spherical pores (roundness 0.5–1) enhance mechanical properties, while phosphogypsum (optimal 10% dosage) effectively improves both strength and workability but requires corrosion control due to its hydration products. Full article