Search Results (105)

Mechanical forces, chemical and electrochemical reactions, and environmental variables can all lead to surface degradation of parts. Composite coatings can be applied to these materials to enhance their surface characteristics. Recently, nickel-based composite coatings have gained greater attention because of their remarkable wear resistance. The efficiency, precision, and affordability of this process make it a popular method. In addition, electroplating nickel-based composites offers a more environmentally friendly alternative to traditional dangerous coatings such as hard chrome. Tribological and wear characteristics are highly dependent on several variables, such as particle parameters, deposition energy, fluid dynamics, and bath composition. Mass loss, coefficient of friction, hardness, and roughness are quantitative properties that provide useful information for coating optimization and selection. Under optimized electrodeposition conditions, the Ni-SiC-graphite coatings achieved a 57% reduction in surface roughness (Ra), a 38% increase in microhardness (HV), and a 25% reduction in wear rate (Ws) compared to pure Ni coatings, demonstrating significant improvements in tribological performance. Overall, the incorporation of SiC nanoparticles was found to consistently improve microhardness while graphite or MoS₂ reduces friction. Differences in wear rate among studies appear to result from variations in current density, particle size, or test conditions. Furthermore, researchers run tribology studies and calculate the volume percentage using a variety of techniques, but they fall short in providing a sufficient description of the interface. This work primarily contributes to identifying gaps in tribological research. With this knowledge and a better understanding of electrodeposition parameters, researchers and engineers can improve the lifespan and performance of coatings by tailoring them to specific applications. Full article

The present work aims to synthesize trimetallic catalysts supported on mixed oxides such as Al₂O₃-TiO₂. These mixed oxides have been synthesized via the hydrothermal method, which enables us to determine the favorable textural properties that facilitate the oxide in achieving a high dispersion of the NiMoWS active phase. The synthesis of NiMoW supported on Al₂O₃-TiO₂ with varying morphological characteristics presents a wide range of research opportunities related to catalysts for HDS. The knowledge generated by the proposed parametric studies will be essential in establishing a scientific basis for preparing catalysts with suitable properties in this field. Moreover, this study provides two key contributions to the field of hydrotreating catalysis. First, we demonstrate that hydrothermal synthesis assisted by Triton X-100 enables the formation of Al₂O₃–TiO₂ nanostructures with controlled defect density and Ti distribution, features not attainable through conventional sol–gel or mechanical mixing methods. Second, we show that these defect-rich mixed oxides uniquely modulate the dispersion and electronic structure of NiMoW sulfide phases, revealing a nonlinear dependence of activity on W incorporation. These findings offer new guidelines for the rational design of mixed oxide supports for deep hydrotreating applications. Full article

Metal components (CoMo, NiMo, NiW) supported on hierarchical porous USY zeolite (HPY) were systematically optimized for selective naphthalene hydrocracking to BTX (benzene, toluene, xylene). The hierarchical porosity enhanced mass transport and accessibility to active metal sites, improving reaction selectivity and efficiency. Supported metal sulfides served as hydrogenation sites, crucial for aromatic ring activation and coke suppression. By optimizing the synergy between hydrogenation and cracking functions, the optimized Ni₁W/HPY catalyst achieved complete naphthalene conversion with a BTX yield of 92.5%. The spatial distribution of WO₃ crystallites facilitated functional separation, promoting selective conversion. These findings underscore the importance of metal–acid balance and pore architecture in designing efficient hydrocracking catalysts. Full article

Weathering steel (WS) is widely used in bridge construction due to its high corrosion resistance, durability, and low maintenance requirements. This paper reviews the performance of WS bridges in Canadian climates, focusing on the formation of protective patina, influencing factors, and long-term maintenance strategies. The protective patina, composed of stable iron oxyhydroxides, develops over time under favorable wet–dry cycles but can be disrupted by environmental aggressors such as chlorides, sulfur dioxide, and prolonged moisture exposure. Key alloying elements like Cu, Cr, Ni, and Nb enhance corrosion resistance, while design considerations—such as drainage optimization and avoidance of crevices—are critical for performance. The study highlights the vulnerability of WS bridges to microenvironments, including de-icing salt exposure, coastal humidity, and debris accumulation. Regular inspections and maintenance, such as debris removal, drainage system upkeep, and targeted cleaning, are essential to mitigate corrosion risks. Climate change exacerbates challenges, with rising temperatures, altered precipitation patterns, and ocean acidification accelerating corrosion in coastal regions. Future research directions include optimizing WS compositions with advanced alloys (e.g., rare earth elements) and integrating climate-resilient design practices. This review highlights the need for a holistic approach combining material science, proactive maintenance, and adaptive design to ensure the longevity of WS bridges in evolving environmental conditions. Full article

This study investigates the potential of biochars derived from agricultural waste biomass for the removal of heavy metal ions from aqueous solutions. Biochars were produced via slow pyrolysis at 793 K using almond shells (AS), walnut shells (WS), pistachio shells (PS), and rice husks (RH) as feedstocks. The physicochemical properties and adsorption performance of the resulting materials were evaluated with respect to Cd(II), Mn(II), Co(II), Ni(II), Zn(II), total Iron (Fe_tot), total Arsenic (As_tot), and total Chromium (Cr_tot) in model solutions. Surface morphology, porosity, and surface chemistry of the biochars were characterized by scanning electron microscopy (SEM), nitrogen adsorption at 77 K (for specific surface area and pore structure), Fourier-transform infrared spectroscopy (FTIR), and determination of the point of zero charge (pH_pzc). Based on their textural properties, biochars derived from WS, PS, and AS were classified as predominantly microporous, while RH-derived biochar exhibited mesoporous characteristics. The highest Brunauer–Emmett–Teller (S_BET) surface area was recorded for PS biochar, while RH biochar showed the lowest. The pistachio shell biochar exhibited the highest specific surface area (440 m²/g), while the rice husk biochar was predominantly mesoporous. Batch adsorption experiments were conducted at 25 °C, with an adsorbent dose of 3 g/L and a contact time of 24 h. The experiments in multicomponent systems revealed removal efficiencies exceeding 87% for all tested metals, with maximum values reaching 99.9% for Cd(II) and 97.5% for Fe_tot. The study highlights strong correlations between physicochemical properties and sorption performance, demonstrating the suitability of these biochars as low-cost sorbents for complex water treatment applications. Full article

This study focuses on researching the influence of Mo on the corrosion mechanism of 1%Ni weathering steel (WS) in simulated marine atmospheric conditions. The Mo element is involved in the reaction, and after hydrolysis, MoO₂ and MoO₃ are produced. The deposition of MoO₂ and MoO₃ occurs in cracks and fissures, rendering the rust layer more uniform and homogeneous. It also furnishes nucleation sites for amorphous oxyhydroxide, which in turn promotes the interweaving of a nanosized oxyhydroxide network. As a result, the rust layer develops into a physical barrier that acquires a protective capacity. Only some of the Mo ions migrate to the vicinity of the Ni element for the hydrolysis reaction, which leads to the difficulty in improving the corrosion rate of the steel with a high Mo content. Hence, the content of Mo element can be controlled within 0.3–0.5% for the 1Ni WS. Full article

Temporal variations in diurnal internal tides (ITs) and near-inertial waves (NIWs) in the southern South China Sea (SCS) are characterized, based on two 13-month moored current observations. Diurnal ITs, dominated by O₁ and K₁, are found to exhibit spring–neap cycles of about 14 days and significant seasonal variations. The incoherent components explain 54% and 56% of the total energy in the diurnal band, which further complicates its temporal variabilities. As for NIWs, wind energy input serves as the primary energy source and three strong events are observed. Tropical cyclone RAI passed through two moorings during the event 1 period, and triggered a peak near-inertial kinetic energy of 19.55 J m⁻³ (18.82 J m⁻³) at two moorings. After generation, the NIWs propagated downward to around 300 m, becoming the most intense event observed at DA2. In contrast, the NIWs response to tropical cyclone NOCK’s passage during event 3 was relatively weaker. The near-inertial KE generated by NOCK was confined to depths shallower than 150 m, with the average near-inertial KE being only 85% (52%) of that during event 1 for two moorings, despite the near-inertial energy input from NOCK being nearly 400% that of RAI. The modulation of background vorticity is considered the primary factor resulting in the difference in intensity of two NIW events. The penetrating depth of NIWs under the modulation of anticyclonic eddies was more than twice that under the cyclonic eddies. Furthermore, the strongest NIWs during event 2 that were observed below 350 m at mooring 2 (183% stronger than average) were also related to a strong anticyclonic eddy. Full article

Cleavage of C-C bonds is crucial for hydrogen production via aqueous phase reforming of biomass-derived oxygenates. In this study, the hydrogen production performance and C-C bond cleavage capacity of Ni-W/AC catalysts with varying W/Ni ratios are evaluated using ethylene glycol as a model compound. A series of APR experiments conducted suggests that Ni-0.2W/AC catalyst exhibits the highest C₁/C₂₊ ratio of 15.87 and achieves a hydrogen yield of 47.76%. The enhanced Ni-W bimetallic interactions, which significantly improve the efficiency of C-C bond cleavage and increase catalyst activity by promoting active site dispersion, are confirmed by detailed characterization techniques. Further analysis of product distribution provides insights into the reaction pathways of ethylene glycol and the reaction mechanism for ethanol during aqueous phase reforming. All the results indicate that this catalytic reforming method effectively facilitates C-C bond cleavage and hydrogen production, contributing to a better understanding of APR mechanisms for biomass-derived oxygenates. Full article

Environmental legislation has focused its attention on improving air quality. In this context, the presence of sulfur compounds in fuels, such as diesel and gasoline, is undesirable. When sulfur is combusted, compounds are emitted as SO_x (SO₂ and SO₃) into the atmosphere, causing acid rain and respiratory diseases. For this reason, environmental norms have been established to reduce the sulfur content of fuels. Sulfur (mainly as alkylbenzothiophenes, dibenzothiophenes and alkyldibenzothiophenes) is removed in refineries through a process called hydrodesulfurization (HDS). HDS is performed at an industrial level with the use of NiMo, CoMo or NiW catalysts supported on alumina. Unsupported MoS₂ (bulk) catalysts have recently attracted attention due to their high activity and selectivity in HDS. In this study, bulk NiMo catalyst precursors were synthesized using solvothermal methods with varying pH and solvothermal synthesis time. The precursors and catalysts were characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS) microanalysis, X-ray diffraction (XRD), textural properties using liquid nitrogen physisorption at 77 K, Raman spectroscopy and high-resolution transmission electron microscopy (HTREM). The results indicate that the morphology of the NiMoO₄ precursors synthesized in an ethanol/water mixture varies, forming “grains,” “flakes” or “rods,” depending on the dwell time and synthesis conditions. The catalytic activity results show that the bulk NiMo catalyst synthesized at 2 h presented higher selectivity and catalytic activity in the HDS of 4,6-DMDBT when compared to a supported reference catalyst (NiMo/γ-Al₂O₃). Full article

It is difficult for traditional weathering steel (WS) to form a protective rust layer to withstand the chloride ions and high humidity. Hence, there is an urgent need to develop a new type of low-cost WS with excellent corrosion resistance in the containing NaCl environment. This study aims to determine the influence of Cu on the corrosion mechanism of 1%Ni WS in simulated containing NaCl atmospheric environments. By increasing the Cu content (0.15–0.55%), the corrosion resistance of WS is enhanced. The increasing Cu content promotes the formation of a stable and compact rust layer, significantly enriching the proportion of α-FeOOH to equip the rust layer with a physical barrier. The formation of CuO deposits in the holes and cracks make the rust layer more compact and uniform. The increased Cu content promotes the formation of CuFeO₂ and increases the content of NiFe₂O₄. The formation of CuFeO₂ and NiFe₂O₄ then equips the rust layer with a chemical barrier. Hence, the addition of Cu could enhance the resistance of 1%Ni WS to containing NaCl atmospheric environments. Full article

This study investigated the development and optimization of sol–gel synthesized Ni/ZrO₂-Al₂O₃ catalysts, aiming to enhance the decomposition efficiency of CF₄, a potent greenhouse gas. The research focused on improving catalytic performance at temperatures below 700 °C by incorporating zirconium and tungsten as co-catalysts. Comprehensive characterization techniques including XRD, BET, FTIR, and XPS were employed to elucidate the structural and chemical properties contributing to the catalyst’s activity and durability. Various synthesis ratios, heat treatment temperatures, and co-catalyst addition positions were explored to identify the optimal conditions for CF₄ decomposition. The catalyst composition with 7.5 wt% ZrO₂ and 3 wt% WO₃ on Al₂O₃ (3W-S3) achieved over 99% CF₄ decomposition efficiency at 550 °C. The study revealed that the appropriate incorporation of ZrO₂ enhanced the specific surface area and prevented sintering, while the addition of tungsten further improved the distribution of active sites. These findings offer valuable insights into the design of more efficient catalysts for environmental applications, particularly in mitigating emissions from semiconductor manufacturing processes. Full article

In this study, we have prepared Ni-W/Cr₃C₂ composite electrodeposits through the diffuse reinforcement mechanism of chromium carbide nanoparticles. These electrodeposits exhibit excellent corrosion resistance and are designed to effectively protect the structural materials of pipe columns under the harsh CO₂ corrosion environments faced by carbon sequestration and utilization technologies. A systematic investigation was conducted into the micro-morphology, profile undulation, phase composition, and surface chemical state of the electrodeposits. Furthermore, the corrosion-resistant behavior of Ni-W/Cr₃C₂ composite electrodeposits was investigated in simulated corrosive environments (i.e., brine solution containing 3.5 wt% NaCl and CO₂-saturated brine). We then evaluated their corrosion response under the aforementioned conditions using electrochemical methods. In addition, the EIS of electrodeposited coatings revealed that the dense oxide film layer formed on the surface of the deposits, which acted as a primary barrier against corrosion, playing a pivotal role in maintaining the overall corrosion resistance of the material. Full article

Researchers are developing innovative electrode materials with high energy and power densities worldwide for effectual energy storage systems. Transition metal dichalcogenides (TMDs) are arranged in two dimensions (2D) and have shown great promise as materials for photoelectrochemical activity and supercapacitor batteries. This study reports on the fabrication of WS₂@NiCoS and WS₂@NiCoS@ZnS hybrid nano-architectures through a simple hydrothermal approach. Because of the strong interfacial contact between the two materials, the resultant hierarchical hybrids have tunable porosity nanopetal decorated morphologies, rich exposed active edge sites, and high intrinsic activity. The specific capacities of the hybrid supercapacitors built using WS₂@NiCoS and WS₂@NiCoS@ZnS electrodes are 784.38 C g⁻¹ and 1211.58 C g⁻¹ or 2019.3 F g⁻¹, respectively, when performed at 2 A g⁻¹ using a three-electrode setup. Furthermore, an asymmetric device (WS₂@NiCoS@ZnS//AC) shows a high specific capacity of 190.5 C g⁻¹, an energy density of 49.47 Wh kg^−1, and a power density of 1212.30 W kg⁻¹. Regarding the photoelectrochemical activity, the WS₂@NiCoS@ZnS catalyst exhibits noteworthy characteristics. Our findings pave the way for further in-depth research into the use of composite materials doped with WS₂ as systematic energy-generating devices of the future. Full article

This study presents a novel approach to enhancing the performance of Ni-W-SiC coatings through magnetic field-assisted electrodeposition, with a specific focus on the influence of magnetic field orientation. The coatings were evaluated for their structure, surface topology, roughness, corrosion resistance, and wear resistance. The results indicated that the perpendicular magnetic orientation of the coating, obtained at a magnetic field value equal to 0.3 T (S1), showed the largest content of SiC, with a minimal grain size of Ni-W, measuring 84.7 nm with smooth, fine, and dense surface architecture. The S1 coating’s surface roughness, as revealed by AFM images, was 24.46 nm, significantly less than that of the coatings produced with 0 T (S0) and 0.3 T (S2) magnetic inductions. XRD results revealed that the Ni-W grains’ predominant growth direction shifted from the planar direction of (200) to the (111) direction, due to the application of a magnetic field oriented perpendicularly. In addition, the S1 coating had an outstanding corrosion resistance. Furthermore, S1, among all coatings, had the highest value of hardness, along with the lowest coefficient of friction and higher wear resistance. This work sets the stage for future advancements in surface engineering, demonstrating the potential of magnetic field orientation as a tool for material enhancement. Full article

Near-inertial waves (NIWs), a special form of internal waves with a frequency close to the local Coriolis frequency, are ubiquitous in the ocean. NIWs play a crucial role in ocean mixing, influencing energy transport, climate change, and biogeochemistry. This manuscript briefly reviews the generation and propagation of NIWS in the oceans. NIWs are primarily generated at the surface by wind forcing or through the water column by nonlinear wave-wave interaction. Especially at critical latitudes where the tidal frequency is equal to twice the local inertial frequency, NIWs can be generated by a specific subclass of triadic resonance, parametric subharmonic instability (PSI). There are also other mechanisms, including lee wave and spontaneous generation. NIWs can propagate horizontally for hundreds of kilometers from their generating region and radiate energy far away from their origin. NIWs also penetrate deep into the ocean, affecting nutrient and oxygen redistribution through altering mixing. NIW propagation is influenced by factors such as mesoscale eddies, background flow, and topography. This review also discussed some recent observational evidence of interactions between NIWs from different origins, suggesting a complicated nonlinear interaction and energy cascading. Despite the long research history, there are still many areas of NIWs that are not well defined. Full article