Search Results (1,765)

18CrNiMo7-6 steel is widely used in high-load mechanical components, but its poor surface hardness and corrosion resistance limit its service life. This study performed vacuum solid boriding treatment on 18CrNiMo7-6 steel at 1000 °C for different times and investigated the phase composition, microstructure, hardness, surface morphology, and corrosion resistance of the resulting boride layers. The experimental results showed that the boriding treatment formed a dual-phase boride layer on the steel surface, consisting of an outer FeB layer and an inner Fe₂B layer, both of which increased in thickness with increasing boriding time. The surface hardness was significantly enhanced due to the formation of hard boride phases, exhibiting a gradient distribution that correlates with the microstructural transition from the surface to the substrate. The surface roughness exhibited a progressive increase with boriding time, which was attributed to the volumetric expansion and nodular growth associated with boride formation. Furthermore, the corrosion resistance was remarkably improved after boriding and was further enhanced with longer processing times. This improvement is attributed to the thickening and enhanced continuity of the boride layer over time, which mitigated the potential adverse effects of surface roughness. This study demonstrates that vacuum high-temperature boriding effectively co-enhances the surface hardness and corrosion resistance of alloy steel, providing a viable surface modification strategy for high-load components. Full article

This work investigates the corrosion behavior of 18%Ni high-strength steel (00Ni18Co-8Mo5TiAl, solution-treated at 820 °C for 3 h and aged at 480 °C for 3 h) in NaCl solutions with 1%, 3.5%, and 6% chloride ions, as well as chloride ions’ effect on passive film properties. The corrosion process was systematically studied via chemical immersion tests (GB/T 17897-1999, 144 h, solution-to-sample contact area ratio 20:1) and electrochemical methods, including EIS (frequency range: 100 kHz–0.01 Hz) and Tafel polarization curves (scan rate: 10 mV/min). Passive film evolution was analyzed via Mott–Schottky curves (fixed frequency: 1000 Hz, scanning potential: −1 V to 1 V vs. SCE). Microstructural observations show the steel exhibits pitting corrosion in chloride environments, with corrosion products transforming from loose outer α-FeOOH/γ-FeOOH to dense inner Fe₃O₄/β-FeOOH. These dense products inhibit anodic reactions. Electrochemical results reveal polarization resistance decreases and corrosion current density rises with increasing chloride concentration. Mott–Schottky curves indicate that flat band potential increases from −0.2177 V to −0.1258 V with rising chloride concentration, increasing point defects in the passive film and weakening its self-healing ability. Full article

Furfural extraction oil (FEO) is rich in polycyclic aromatic hydrocarbons (PAHs) and is hard to convert under mild conditions. To address this upgrade challenge, this study proposed a co-aquathermolysis process with corn stalk and a Ni/Mo hydrofining catalyst. Key parameters, including reaction temperature, time, catalyst dosage, and corn stalk dosage, were systematically evaluated for their impact on upgrade performance. Under optimized conditions (oil-to-water mass ratio 2:1, 280 °C, 18 h, 8 wt% catalyst, 8 wt% corn stalk), a viscosity reduction rate of 19.96% was achieved, significantly exceeding the 12.69% rate obtained without corn stalk. Meanwhile, the average molecular weight decreased from 430.0 to 353.3 g·mol⁻¹ and the aromatic ring index declined from 3.049 to 2.593. The H/C ratio increased to 1.568, and the sulfur content decreased to 0.09210%. ¹H NMR analysis revealed that corn stalk promotes long-chain scission and inhibits aromatic condensation, leading to a reduced aromatic carbon fraction. A detailed hydrocarbon composition analysis corroborated the conversion of tricyclic and tetracyclic aromatic hydrocarbons to monocyclic and bicyclic aromatic hydrocarbons. These findings offer valuable insights for the modification of FEO via aquathermolysis and establish biomass utilization as a practical strategy for FEO upgrades. Full article

To improve the accuracy of gravimetric liquid hydrogen flow standard devices, the self-weight of the weighing tank must be minimized, because the total mass of the liquid hydrogen contained in the tank is far smaller than the structural mass of the tank itself, which severely compromises the sensitivity of gravimetric measurement. In this study, a three-dimensional finite element model of a vacuum-insulated liquid-hydrogen weighing tank was developed in ABAQUS. The inner and outer shells were modeled with 06Cr19Ni10 (304) and 06Cr17Ni12Mo2 (316) austenitic stainless steels, and Polyamide 6 (PA6) was used for the internal support. Three operating stages were considered: evacuation of the annulus (interlayer pressure reduced from 0.1 MPa to 0 MPa), pre-cooling to −253 °C, and pressurization of the inner tank (internal pressure increased from 0.1 MPa to 1 MPa). The equivalent stress and deformation were compared for different materials and wall thicknesses to evaluate structural safety and weight-reduction potential. The proposed configuration (inner shell 1.6 mm and outer shell 1.0 mm) achieves a mass reduction of more than 50% relative to the 3 mm minimum wall thickness commonly adopted for cryogenic vessels, while keeping stresses below the allowable limits. This reduction enables the use of higher-resolution load cells and thereby lowering the measurement uncertainty of the liquid hydrogen flow standard device and providing technical support for lightweight and cost-effective design, with potential applicability to other cryogenic tank systems. Full article

The six platinum group elements (PGE) are among the rarest elements in the upper continental crust of the earth. Higher values of PGE have been detected in the upper mantle and in chondrite meteorites. The PGE are siderophile and chalcophile elements and are divided into the following: (1) the Ir subgroup (IPGE) = Os, Ir, and Ru and (2) the Pd subgroup (PPGE) = Rh, Pt, and Pd. The IPGE are more refractory and less chalcophile than the PPGE. High concentrations of PGE led, in rare cases, to the formation of mineral deposits. The PGE are carried in discrete phases, the platinum group minerals (PGM), and are included as trace elements into the structure of base metal sulphides (BM), such as pentlandite, chalcopyrite, pyrite, and pyrrhotite. Similarly to PGE, the PGM are also divided into two main groups, i.e., IPGM composed of Os, Ir, and Ru and PPGM containing Rh, Pt, and Pd. The PGM occur both in mafic and ultramafic rocks and are mainly hosted in stratiform reefs, sulphide-rich lenses, and placer deposits. Presently, there are only 169 valid PGM that represent about 2.7% of all 6176 minerals discovered so far. However, 496 PGM are listed among the valid species that have not yet been officially accepted, while a further 641 are considered as invalid or discredited species. The main reason for the incomplete characterization of PGM resides in their mode of occurrence, i.e., as grains in composite aggregates of a few microns in size, which makes it difficult to determine their crystallography. Among the PGM officially accepted by the IMA, only 13 (8%) were discovered before 1958, the year when the IMA was established. The highest number of PGM was discovered between 1970 and 1979, and 99 PGM have been accepted from 1980 until now. Of the 169 PGM accepted by the IMA, 44% are named in honour of a person, typically a scientist or geologist, and 31% are named after their discovery localities. The nomenclature of 25% of the PGM is based on their chemical composition and/or their physical properties. PGM have been discovered in 25 countries throughout the world, with 64 from Russia, 17 from Canada and South Africa (each), 15 from China, 12 from the USA, 8 from Brazil, 6 from Japan, 5 from Congo, 3 from Finland and Germany (each), 2 from the Dominican Republic, Greenland, Malaysia, and Papua New Guinea each, and only 1 from Argentine, Australia, Bulgaria, Colombia, Czech Republic, England, Ethiopia, Guyana, Mexico, Serbia, and Tanzania each. Most PGM phases contain Pd (82 phases, 48% of all accepted PGM), followed, in decreasing order of abundances, by those of Pt 35 phases (21%), Rh 23 phases (14%), Ir 18 phases (11%), Ru 7 phases (4%), and Os 4 phases (2%). The six PGE forming the PGM are bonded to other elements such as Fe, Ni, Cu, S, As, Te, Bi, Sb, Se, Sn, Hg, Ag, Zn, Si, Pb, Ge, In, Mo, and O. Thirty-two percent of the 169 valid PGM crystallize in the cubic system, 17% are orthorhombic, 16% hexagonal, 14% tetragonal, 11% trigonal, 3% monoclinic, and only 1% triclinic. Some PGM are members of a solid-solution series, which may be complete or contain a miscibility gap, providing information concerning the chemical and physical environment in which the mineral was formed. The refractory IPGM precipitate principally in primitive, high-temperature, mantle-hosted rocks such as podiform and layered chromitites. Being more chalcophile, PPGE are preferentially collected and concentrated in an immiscible sulphide liquid, and, under appropriate conditions, the PPGM can precipitate in a thermal range of about 900–300 °C in the presence of fluids and a progressive increase of oxygen fugacity (fO₂). Thus, a great number of Pt and Pd minerals have been described in Ni-Cu sulphide deposits. Two main genetic models have been proposed for the formation of PGM nuggets: (1) Detrital PGM represent magmatic grains that were mechanically liberated from their primary source by weathering and erosion with or without minor alteration processes, and (2) PGM reprecipitated in the supergene environment through a complex process that comprises solubility, the leaching of PGE from the primary PGM, and variation in Eh-pH and microbial activity. These two models do not exclude each other, and alluvial deposits may contain contributions from both processes. Full article

Black liquor, the side stream from Kraft pulping, is a promising feedstock for the production of renewable fuels via hydrothermal liquefaction (HTL). However, further upgrading of the black liquor HTL oil is required to reduce the oxygen content for fuel use. In this work, the hydrodeoxygenation (HDO) of black liquor HTL oil model compounds was investigated to enhance the understanding of catalyst activity and selectivity under hydrothermal conditions. The study focused on isoeugenol and 4-methylcatechol as model compounds, representing different functionalities in black liquor-derived HTL-oil. Sulfided NiMo catalysts supported on titania, zirconia, activated carbon, and α-alumina were evaluated in batch mode at subcritical and supercritical upgrading using hydrogen gas. The results show that isoeugenol was fully converted in all experiments, while 4-methylcatechol conversion varied depending on the catalyst and reaction conditions. Phenols were obtained as the main products and the maximum degree of deoxygenation achieved was around 40%. This research provides insights into the potential of hydrothermal HDO for upgrading BL-derived biocrudes, emphasising the importance of catalyst selection and reaction conditions in hydrothermal conditions. Full article

This study utilizes COMSOL Multiphysics (version 6.0) to design a planar ultra-broadband optical absorber with a multilayer configuration. The proposed structure consists of seven stacked layers arranged from bottom to top: W (h1, acting as a reflective substrate and transmission blocker), WSe₂ (h2), SiO₂ (h3), Ni (h4), SiO₂ (h5), Mo (h6), and SiO₂ (h7). One key finding of this study is that, when all other layer thicknesses are fixed, variations in the Mo layer thickness systematically induce a redshift in both the short- and long-wavelength cutoff edges. Notably, the long-wavelength cutoff exhibits a larger shift than the short-wavelength edge, resulting in an increased absorption bandwidth where absorptivity remains above 0.900. The second contribution is the demonstration that this planar structure can be readily engineered to achieve ultra-broadband absorption, spanning from the near-ultraviolet and visible region (360 nm) to the mid-infrared (6300 nm). An important characteristic of the proposed design is that the thickness of the h7 SiO₂ layer influences the cutoff wavelength at the short-wavelength edge, while the thickness of the h6 Mo layer governs the cutoff position at the long-wavelength edge. This dual modulation capability allows the proposed optical absorber to flexibly tune both the spectral range and the bandwidth in which absorptivity exceeds 0.900, thereby enabling the realization of a wavelength- and bandwidth-tunable optical absorber. Full article

Alkaline water electrolysis remains one of the leading and most mature technologies for large-scale hydrogen production. Its advantages stem from the use of inexpensive, earth-abundant materials and well-established industrial deployment, yet the technology continues to face challenges, including sluggish hydrogen evolution reaction (HER) kinetics and energy-efficiency limitations compared with acidic electrolysis systems. This review provides a comprehensive overview of the fundamental principles governing alkaline electrolysis, encompassing electrolyte chemistry, electrode materials, electrochemical mechanisms, and the roles of overpotentials, cell resistances, and surface morphology in determining system performance. Key developments in catalytic materials are discussed, highlighting both noble-metal and non-noble-metal electrocatalysts, as well as advanced approaches to surface modification and nanostructuring designed to enhance catalytic activity and long-term stability. Particular emphasis is placed on the emerging strategy of in situ ionic activation, wherein transition-metal ions and oxyanions are introduced directly into the operating electrolyte. These species dynamically interact with electrode surfaces under polarization, inducing real-time surface reconstruction, improving water dissociation kinetics, tuning hydrogen adsorption energies, and extending electrode durability. Results derived from polarization measurements, electrochemical impedance spectroscopy, and surface morphology analyses consistently demonstrate that ionic activators, such as Ni–Co–Mo systems, significantly increase the HER performance through substantial increase in surface roughness and increased intrinsic electrocatalytic activity through synergy of d-metals. By integrating both historical context and recent research findings, this review underscores the potential of ionic activation as a scalable and cost-effective way toward improving the efficiency of alkaline water electrolysis and accelerating progress toward sustainable, large-scale green hydrogen production. Full article

Trace elements are essential for organisms, and their involvement in diverse diseases is increasingly recognised. Interest is increasing in veterinary medicine, particularly in relation to canine diseases. However, reference intervals for trace elements in dogs remain scarce. Plasma samples from 140 dogs were analysed by inductively coupled plasma mass spectrometry to determine the levels of 13 trace elements. Reference intervals (µg/L) were established for the following 12 elements: As, 0.417–8.17; Co, 0.039–1.33; Cr, 2.41–13.3; Cu, 296–790; Fe, 846–3643; Hg, 0.235–2.33; Ni, 0.567–9.04; Mn, 1.90–7.28; Mo, 1.43–12.7; Pb, 0.285–2.82; Se, 200–434; and Zn, 415–1095. However, Cd was below the limit of quantification in 77% of the samples. No differences in trace element concentrations were observed in relation to breed or reproductive status. Statistically significant differences were found in relation to sex (Cu, Mo, Zn), age (Co, Cu, Mo, Mn, Se, Zn), and size (Cu, Mo, Se, Zn); however, the magnitude of these effects varied among elements and was generally weak. Nevertheless, these factors should be considered when assessing trace element status. These reference intervals constitute an important resource for both clinical evaluation and future research. Full article

Around eight million people—mainly in cities—die prematurely from pollution-related diseases; thus, studies of urban dust have become increasingly relevant over the last two decades. In this study, an assessment of heavy metal and metalloid contamination in urban dust was conducted in downtown Murcia, Spain. The objectives were to evaluate the level of contamination and the associated health risks, both with a spatially explicit focus. One hundred and twenty-eight urban dust samples were collected, each from a 1-square-meter area, using plastic tools to prevent contamination. The dust was dried and weighed, then acid-digested before analysis via inductively coupled plasma mass spectrometry. Corresponding maps were then generated using a geographic information system. The elements analyzed in the urban dust (with their median concentrations, given in mg/kg) were As (2.14), Bi (14.06), Cd (0.38), Co (1.88), Cr (71.17), Cu (142.60), Fe (13,752), Mn (316.64), Mo (3.90), Ni (21.94), Pb (106.27), Sb (6.54), Se (4.34), Sr (488.08), V (28.05), and Zn (357.33). The sequence of median concentrations for the analyzed elements was Fe > Sr > Zn > Mn > Cu > Pb > Cr > V > Ni > Bi > Sb > Se > Mo > As > Co > Cd. The pollution assessment reveals that the city is moderately polluted. Using local background levels, the elements with median values exceeding the threshold for considerable contamination were As, Cu, Pb, Sb, Se, and Zn. Using the global background level, the elements with median values exceeding the threshold for considerable contamination were Bi, Cu, Mo, Pb, Sb, Se, and Zn. The median value of the sum of the hazard index (1.82) indicates a risk to children’s health. The hazard index revealed that 43% of the sites pose a relative risk to children. In contrast to previous global studies, the present research provides a multi-scale assessment of urban pollution and health risks. Pollution is evaluated by metal, city, zone, and site, while health risks are assessed by metal, city, and site. We recommend a strategy for both local authorities and residents. Full article

The increasing global energy demand and its negative environmental impact created the need for substantial changes in the energy infrastructure. A hydrogen-based infrastructure appears to be the most promising way to secure a clean and safe energy future. Water electrolysis is a method that can be used to generate green hydrogen, but suitable electrocatalysts are required for large-scale applications. This work investigates the electrocatalytic activity of electrodes modified with novel TiO₂ nanotube-based electrocatalysts for water electrolysis. The focus was on the hydrogen evolution reaction (HER), and the electrodes that displayed the highest activity were the ones obtained with the procedure consisting of the growth of TiO₂ nanotubes on a Ti plate by anodization, the subsequent deposition of MoO₂ and Ni(OH)₂, and a thermal treatment performed under different conditions. The results of the HER experiments performed in a strong alkaline environment showed that the electrode obtained via vacuum heat treatment exhibited the lowest overpotential value, of 238 mV at i = −10 mA/cm². Furthermore, the electrode was electrochemically stable, and inter-electrode reproducibility tests revealed only a small variation of the HER overpotential. Full article

Ni-Mo alloy coating has shown exciting potential as a candidate to replace chromium coating. In this paper, Ni-Mo alloy coatings were successfully electrodeposited from a citrate/ammonia bath, and the effect of the bath pH values over a wide range (4–10) on the characteristics and corrosion resistance of Ni-Mo alloy coating was studied in detail. Results show that all the deposited Ni-Mo alloy coatings consist of a crystalline solid-solution Ni(Mo) fcc structure. An increase in bath pH values could facilitate the deposition of Mo, thereby increasing the Mo content and decreasing the crystallite size of Ni-Mo alloy coatings. However, there are subtle gaps between the coarse grains on the surface of the Ni-Mo alloy coating deposited at pH 10. These subtle gaps tend to form between the coarse grains on the surface of the electrodeposited Ni-Mo alloy coating because of the relatively high Mo content, refined grains, and appropriate morphology. The Ni-Mo alloy coating deposited at pH 9 exhibits optimal corrosion resistance, attributed to its lowest corrosion current density i_corr (7.31 × 10⁻⁶ A cm⁻²), the strongest polarization resistance (11.13 kΩ·cm⁻²), and impedance value, which are mainly contributed to by the coating resistance and charge-transfer resistance. Full article

The production of heavy gauge quenched and tempered steel plates requires alloying strategies that ensure adequate hardenability and microstructural uniformity under limited cooling rates. Molybdenum (Mo) and nickel (Ni) are key elements in this context, as they influence both hot-working behavior and phase transformation kinetics. This study investigates the effect of Mo (0.25–0.50 wt%) and Ni (0–1.00 wt%) additions on static recrystallization and transformation behavior using laboratory thermomechanical simulations representative of thick plate rolling conditions. Multipass and double-hit torsion tests were performed to determine the non-recrystallization temperature (Tnr) and quantify softening kinetics, while dilatometry was employed to construct Continuous Cooling Transformation (CCT) diagrams and assess hardenability. Results indicate that Mo significantly increases Tnr and delays recrystallization through a solute drag mechanism, whereas Ni exerts a minor but measurable effect, likely associated with stacking fault energy rather than classical solute drag. Both elements reduce ferrite and bainite transformation temperatures, enhancing hardenability; however, Mo alone cannot suppress ferrite formation at practical cooling rates, requiring combined Mo–Ni additions to achieve fully martensitic microstructures. These findings provide insight into alloy design for thick plate applications and highlight the limitations of existing predictive models for Ni-containing steels. Full article

This paper investigates the applicability of plasma transferred arc (PTA) cladding for extending the service life of biomass shredder tools. The study evaluates the possibility of replacing Hardox 500 steel with a lower-cost structural steel S355J2 whose functional surfaces are modified by PTA cladding. Three commercially available powder fillers were examined: CoCrWNi (PL1), FeCoCrSi (PL2), and NiCrMoFeCuBSi (PL3). The quality and performance of the cladded layers were assessed through hardness measurements, microstructural analysis using SEM and EDX, and tribological testing focused on abrasive and adhesive wear at room temperature. The results showed that the PL1 cladding achieved the highest surface hardness, reaching up to 602 HV0.1, due to the presence of hard carbide phases. In contrast, the PL2 cladding exhibited the best resistance to abrasive wear, demonstrating the lowest mass loss for both as-deposited and machined surfaces. The PL3 cladding showed intermediate performance in terms of wear resistance. Overall, the findings indicate that PTA cladding using an FeCoCrSi-based filler on an S355J2 substrate represents a promising and cost-effective alternative to Hardox 500 for biomass shredder applications. Full article

The dissimilar joining of solid-solution-strengthened superalloys and precipitation-strengthened superalloys enables complementary performance synergy, holding significant application potential in the aerospace industry. This study investigated the transient liquid phase bonding of Hastelloy X and IN738 using a BNi-2 interlayer, focusing on the effects of bonding temperature and time on interfacial microstructure evolution and mechanical properties. The results demonstrated that achieving complete isothermal solidification is paramount for joint properties, a process governed by the synergistic control of bonding temperature and time. At lower temperatures (e.g., 1050 °C), the joint centerline contained an athermal solidification zone (ASZ) rich in hard and brittle Cr-rich (∼15.9 GPa) and Ni-rich borides, which served as the failure initiation site. As the ASZ was progressively eliminated with increasing temperature, a fully isothermal solidified zone (ISZ, ∼52 μm wide) consisting of γ-Ni formed at 1100 °C. Concurrently, Cr-Mo borides (∼9.8 GPa) precipitated within the diffusion-affected zone (DAZ) on the Hastelloy X side, becoming the new potential sites for crack initiation. Prolonging the holding time at 1100 °C not only ensured complete isothermal solidification but also promoted Mo diffusion, which improved the plasticity of the Cr-Mo borides and their interfacial bonding with the γ-Ni matrix (∼5.9 GPa). This synergistic optimization resulted in a significant increase in joint shear strength, achieving a maximum value of 587 MPa under the optimal condition of 1100 °C/40 min. Full article