Search Results (100)

Classical thermodynamics omits rigidity, which property distinguishes solids from gases and liquids. By accounting for rigidity (i.e., Young’s elastic modulus, ϒ), we recently amended historical formulae and moreover linked heat capacity, thermal expansivity, and ϒ. Further exploration is motivation by the importance of classical thermodynamics to various applied sciences. Based on heat performing work, we show here, theoretically, that density times sublimation enthalpy divided by the molar mass (ρΔH_sub/M, energy per volume), depends linearly on ϒ (1 GPa = 10⁹ J m⁻³). Data on diverse metals, non-metallic elements, chalcogenides, simple oxides, alkali halides, and fluorides with cubic structures validate this relationship at ambient conditions. Furthermore, data on hcp metals and molecular solids show that ρΔH_sub/M is proportional to ϒ for anisotropic materials. Proportionality constants vary only from 0.1 to 0.7 among these different material types (>100 substances), which shows that the elastic energy reservoir of solids is large. Proportionality constants depend on whether molecules or atoms are sublimated and are somewhat affected by structure. We show that ductility of refractory, high-ϒ metals affect high-temperature determinations of their ΔH_sub. Our results provide information on sublimation processes and subsequent gas phase reactions, while showing that elasticity of solids is the key parameter needed to assessing their energetics. Implications are highlighted. Full article

Hybrid materials based on porous organic polymers (POPs) and metal–organic frameworks (MOFs) are increasing attention for advanced separation processes due to the possibility to combine their properties. POPs provide high surface areas, chemical stability, and tunable porosity, while MOFs contribute a high variety of defined crystalline structures and enhanced separation characteristics. The combination (or hybridization) with PIMs gives rise to mixed-matrix membranes (MMMs) with improved permeability, selectivity, and long-term stability. However, interfacial compatibility remains a key limitation, often addressed through polymer functionalization or controlled dispersion of the MOF phase. MOF/COF hybrids are more used as biochemical sensors with elevated sensitivity, catalytic applications, and wastewater remediation. They are also very well known in the gas sorption and separation field, due to their tunable porosity and high electrical conductivity, which also makes them feasible for energy storage applications. Last but not less important, hybrids with other POPs, such as hyper-crosslinked polymers (HCPs), covalent triazine frameworks (CTFs), or conjugated microporous polymers (CMPs), offer enhanced functionality. MOF/HCP hybrids combine ease of synthesis and chemical robustness with tunable porosity. MOF/CTF hybrids provide superior thermal and chemical stability under harsh conditions, while MOF/CMP hybrids introduce π-conjugation for enhanced conductivity and photocatalytic activity. These and other findings confirm the potential of MOF-POP hybrids as next-generation materials for gas separation and carbon capture applications. Full article

In this study, the CrCuFeNiTiAl₁ equiatomic alloy was used as a base, which was modified by adding graphite in proportions of 0.5, 1.0, 2.5, and 5.0 mol%. The samples were obtained by powder metallurgy and sintering at 1200 °C for 2 h in a furnace with a protective argon atmosphere. Structural characterization was performed by XRD. A microstructural evaluation was conducted by SEM. The best mechanical microhardness and compressive strength results were obtained in the samples with the lowest amounts of graphite (238 μHV and 1000 MPa, respectively). The density values showed that samples with low amounts of graphite had better densification, lower porosity, and finer structural characteristics than those with graphite percentages higher than 1 mol%. The XRD studies determined the formation of a mixture of crystalline structures composed of FCC due to the presence of Cu, Ni, and Al metals; BCC due to Fe and Cr metals; and HCP due to Ti, and the formation of a Cr₇C₃ compound. SEM analysis showed the formation of cracks and porosity due to the formation of carbides. Full article

The interface morphology plays an important role in the mechanical properties of laminated metal composites (LMCs). In this study, binary LMCs with different crystallographic characteristics, namely Fe/Al (BCC/FCC), Ni/Al (FCC/FCC), and Mg/Al (HCP/FCC), were fabricated through the hierarchical roll-bonding process. The influence of interface morphology on the mechanical properties of the binary LMCs was investigated systematically. The results show that the strength–hardness coefficient (R) decreases with increasing interface morphology factor (α) for the LMCs, indicating that the strengthening effect of LMCs decreases with increased curvature of the interface. The experimental results reveal that α increases with the increase in rolling deformation (thickness reduction) for the LMCs, which is consistent with the finite element simulation results. The dependence of mechanical properties on interface morphology is mainly related to the microstructural inhomogeneity caused by localized deformation in the harder layer, including the formation of shear bands and variations in grain morphology, size, and orientation, which can lead to stress concentration in the necking zone. Full article

The cobalt crystalline islands (Co_cryst) were electrochemically deposited onto a glassy carbon (GC) support and then modified by a facile spontaneous deposition of platinum. The electrocatalytic activity of the resulting Co_cryst-Pt core-shell catalyst was evaluated for the oxygen reduction reaction (ORR) in an alkaline medium. The XRD characterization of the Co_cryst-Pt islands revealed that the cobalt core had a hexagonal close-packed (hcp) crystalline structure, and that the platinum shell exhibited a crystalline structure with a preferential (111) orientation. SEM images showed that the average lateral size of the Co_cryst islands was 1.17 μm, which increased to 1.32 μm after adding platinum. The XPS analysis indicated that the outer layer of the bulk metallic Co_cryst islands was fully oxidized. During the spontaneous deposition of platinum, the outer Co(OH)₂ layer was dissolved, leaving the cobalt core in a metallic state, while the platinum shell remained only partially oxidized. The high electrochemically active surface area of the Co_cryst-Pt/GC electrode, along with a suitable crystalline structure of the Co_cryst-Pt islands, contributes to enhancing its ORR activity by providing a greater number of surface active sites for oxygen adsorption and subsequent reduction. The ORR on the Co_cryst-Pt catalyst occurs via a four-electron reaction pathway, with onset and half-wave potentials of 1.07 V and 0.87 V, respectively, which exceed those of polycrystalline platinum and a commercial benchmark Pt/C. Full article

The mechanical response of monolithic CuZr metallic glass (MG) and MG/Cu composite substrates under high-velocity impact was investigated using molecular dynamics simulations, with variations in impact velocity and initial temperature. Higher impact velocities resulted in deeper penetration and increased plastic deformation, with the monolithic MG exhibiting greater energy absorption and slightly more extensive projectile fragmentation. The MG/Cu composite displayed enhanced plastic deformation, attributed to the higher stiffness of the crystalline Cu phase, which promoted plasticity in the amorphous matrix. Temperature effects were more pronounced in the composite, where elevated temperatures enhanced strain localization and atomic mobility in the glassy phase. This was supported by a decrease in dislocation density and the population of hexagonal close-packed (HCP) atoms with increasing temperature, indicating a shift in plastic activity toward the amorphous matrix. These findings provide insights into the interplay between impact velocity, temperature, and material composition, contributing to a deeper understanding of MG-based composite behavior under extreme loading conditions. Full article

The original Glancing Angle Deposition (GLAD) technique was developed using the evaporation process, i.e., in high vacuum, with a nearly punctual source, and with the substrate aligned with the source axis. In this specific case, the substrate tilt angle can be assumed to be equal to the impinging incidence angle of evaporated atoms. With the sputtering process, the deposition pressure is higher, sources are larger, and substrates are not intrinsically aligned with the source. As a result, deviations from the growth models applied for evaporation are reported, and the substrate tilt angle is no longer relevant for describing the impinging atomic flux. To control the inclined nanostructure of metallic films, a relevant description of the atomic flux is required, applicable across all deposition configurations. In this work, transport simulation is used to determine the resultant incidence angle, a unique criterion relevant to each specific deposition condition. The different representations of the flux are described and discussed, and some typical examples of the resultant angles are presented. Ten elements are investigated: three hcp transition metals (Ti, Zr, and Hf), six bcc transition metals (V, Nb, Ta, Cr, Mo, and W), and one fcc post-transition metal (Al). Full article

Salmonella Dublin (S. Dublin) and Salmonella Typhimurium (S. Typhimurium) are commonly linked to bovine salmonellosis. S. Dublin is, however, considered a bovine-adapted serovar for primarily infecting and thriving in cattle. Using S. Typhimurium (a generalist serovar) as a benchmark, this study investigates genomic factors contributing to S. Dublin’s adaptation to cattle hosts in the U.S. A total of 1337 S. Dublin and 787 S. Typhimurium whole-genome sequences from bovine sources were analyzed with CARD (version 4.0.0), ARG-NOTT (version 6), and AMRfinderPlus (version 4.0.3) for antimicrobial resistance (AMR) genes; VFDB and AMRfinderPlus for virulence genes; AMRFinderPlus for stress genes; and Plasmidfinder for plasmids. Existing clonal groups among isolates of the two serovars were also investigated using the Hierarchical Clustering of Core Genome Multi-Locus Sequence Typing (HierCC-cgMLST) model. The results revealed minimal genomic variation among S. Dublin isolates. Comparatively, the IncX1 plasmid was somewhat exclusively identified in S. Dublin isolates and each carried an average of four plasmids (p-value < 0.05). Furthermore, S. Dublin isolates exhibited a higher prevalence of AMR genes against key antimicrobials, including aminoglycosides, beta-lactams, tetracyclines, and sulfonamides, commonly used in U.S. cattle production. Additionally, Type VI secretion system genes tssJKLM and hcp2/tssD2, essential for colonization, were found exclusively in S. Dublin isolates with over 50% of these isolates possessing genes that confer resistance to heavy metal stressors, like mercury. These findings suggest that S. Dublin’s adaptation to bovine hosts in the U.S. is supported by a conserved genetic makeup enriched with AMR genes, virulence factors, and stress-related genes, enabling it to colonize and persist in the bovine gut. Full article

This work aims to explore the influence of crystal phase engineering on the photocatalytic hydrogen evolution activity of Ru/C₃N₄ systems. By precisely tuning the combination of Ru precursors and reducing solvents, we successfully synthesized Ru co-catalysts with distinct crystal phases (hcp and fcc) and integrated them with C₃N₄. The photocatalytic hydrogen evolution experiments demonstrated that hcp-Ru/C₃N₄ achieved a significantly higher hydrogen evolution rate (24.23 μmol h⁻¹) compared to fcc-Ru/C₃N₄ (7.44 μmol h⁻¹), with activity reaching approximately 42% of Pt/C₃N₄ under the same conditions. Photocurrent and electrochemical impedance spectroscopy analyses revealed that hcp-Ru/C₃N₄ exhibited superior charge separation and transfer efficiency. Moreover, Gibbs free energy calculations indicated that the hydrogen adsorption energy of hcp-Ru (ΔG_H* = −0.14 eV) was closer to optimal compared to fcc-Ru (−0.32 eV), enhancing the hydrogen generation process. These findings highlight that crystal-phase engineering plays a critical role in tuning the electronic structure and catalytic properties of Ru-based systems, offering insights for the design of highly efficient noble metal catalysts for photocatalysis. Full article

High-entropy alloys are novel metallic materials distinguished by very special mechanical and chemical properties that are superior to classical alloys, attracting high global interest for the study and development thereof for different applications. This work presents the creation and characterisation of an FeMoTaTiZr high-entropy alloy composed of chemical constituents with relatively low biotoxicity for human use, suitable for medical tools such as surgical scissors, blades, or other cutting tools. The alloy microstructure is dendritic in an as-cast state. The chemical composition of the FeMoTaTiZr alloy micro-zone revealed that the dendrites especially contain Mo and Ta, while the inter-dendritic matrix contains a mixture of Ti, Fe, and Zr. The structural characterisation of the alloy, carried out via X-ray diffraction, shows that the main phases formed in the FeMoTaTiZr matrix are fcc (Ti₇Zr₃)_0.2 and hcp Ti₂Fe after annealing at 900 °C for 2 h, followed by water quenching. After a second heat treatment performed at 900 °C for 15 h in an argon atmosphere followed by argon flow quenching, the homogeneity of the alloy was improved, and a new compound like Fe_3.2Mo_2.1, Mo_0.93Zr_0.07, and Zr(MoO₄)₂ appeared. The microhardness increased over 6% after this heat treatment, from 694 to 800 HV_0.5, but after the second annealing and quenching, the hardness decreased to 730 HV_0.5. Additionally, a Lactate Dehydrogenase (LDH) cytotoxicity assay was performed. Mesenchymal stem cells proliferated on the new FeMoTaTiZr alloy to a confluence of 80–90% within 10 days of analysis in wells where the cells were cultured on and in the presence of the alloy. When using normal human fibroblasts (NHF), both in wells with cells cultured on metal alloys and in those without alloys, an increase in LDH activity was observed. Therefore, it can be considered that certain cytolysis phenomena (cytotoxicity) occurred because of the more intense proliferation of this cell line due to the overcrowding of the culture surface with cells. Full article

Epitaxial growth can be used to guide the controllable growth of one metal on the surface of another substrate by matching the interface lattice, thus improving the dendrite tendency of metal growth. The atomic arrangement of the Cu (111) crystal plane of the FCC structure is similar to that of the Zn (0002) crystal plane of the HCP structure, which is theoretically expected to promote the heterogeneous epitaxial nucleation growth of metal zinc under low strain. In this paper, the molecular dynamics method is used to simulate the atomic process of zinc film growth on the Cu (111) surface. It is found that the behavior of zinc-adsorbed atoms on the substrate surface conforms to the epitaxial growth mode. The close-packed structure grown along the (0002) direction of the layered clusters is tiled on the Cu (111) surface, forming a highly ordered low-lattice-mismatch interface. When a large area of layered zinc clusters cover the substrate, the growth mode will change from heteroepitaxial growth to homoepitaxial growth of Zn atoms on the zinc film, forming a lamellar distribution composed of FCC and HCP structure grains. Polycrystalline zinc film with a planar structure with a (0002) surface preferred a crystal plane. The increase in incident energy is helpful in improving the quality of zinc films, while the deposition rate, corresponding to the deposition temperature and electrolyte ion concentration, has no significant effect on the surface morphology and crystal structure of single metal films. In summary, the atomic arrangement of the Cu (111) surface has a strong guiding effect on the atomic ordered arrangement in the zinc film crystal, which is suitable for the epitaxial deposition of the substrate to induce the ordered growth of the Zn (0002) crystal plane. Full article

After the thermal-mechanical processing of Mg alloys, extensive 30°⟨0001⟩ grain boundaries (GBs) are present in the recrystallized structure, which strongly affects the mechanical properties via interactions with lattice dislocations. In this work, we systematically investigate how the 30°⟨0001⟩ GBs influence the slip transmission during plastic deformation. We reveal that basal dislocations can be transmuted into its neighboring grain and continue gliding on the basal plane. The prismatic dislocation can transmit the GB remaining on the same Burgers vector. However, a mobile pyramidal $⟨c+a⟩$ dislocation can be absorbed at GBs, initiating the formation of new grain. These findings provide a comprehensive understanding on GB-dislocation interaction in hexagonal close-packed (HCP) metals. Full article

Due to limited slip systems activated at room temperature, the plastic deformation of Mg and its alloys without any preheating of initial billets is significantly limited. To overcome those issues, new methods of severe plastic deformation are discovered and developed. One such example is extrusion with an oscillating die, called KoBo. This method, due to the oscillations of reversible die located at the end of extruded, introduces material into the plastic flow, and thus, enables deformation without preheating of the initial billets of metals that are hard to deform. Such solution is important from an industrial point of view and may lead to serious savings and reduction in carbon dioxide emission to the atmosphere. Therefore, this paper focuses on the possibility of KoBo extrusion of hcp-structured Mg alloys with different chemical compositions and includes comparison of their corrosion resistance using short-term electrochemical tests. In order to have a broad view of the problem presented, we compared the electrochemical behavior of the following groups of Mg materials: pure Mg, Mg-Al-Zn, Mg-Li, and Mg-Y-RE. It was stated that the KoBo method performed at room temperature improves the corrosion resistance of pure Mg when compared to the initial billet and the alloys which belong to the Mg-Al-Zn, Mg-Li, and Mg-Y-RE series. The presented study shows that different corrosion trends are observed for traditionally deformed alloys, and they significantly vary from nascent developments, such as KoBo extrusion. Therefore, it is crucial to widely study those methods because it may be a path leading to long-lasting solution to the formability limitations of Mg-based metallic systems. Full article

Platinum is widely used as a reduction promoter in transition metal heterogeneous catalysts, while its effects on the catalyst’s properties and CO hydrogenation behavior remain unclear. In this study, an improvement in the reducibility of platinum-promoted catalysts is observed. Notably, platinum suppresses the aggregation of cobalt nanoparticles (CoNPs) during catalyst preparation, as evidenced by STEM/TEM and XRD analyses, which reveal the presence of smaller CoNPs and weakened cobalt diffraction in platinum-promoted catalysts. In addition, platinum also promotes the formation of more active hexagonal close-packed (hcp) cobalt but inhibits metal-support interaction (MSI). Therefore, the cobalt-time yield (CTY) for CO hydrogenation in the promoted catalyst is strongly improved, and, furthermore, its intrinsic activity (turnover frequency, TOF) is also slightly increased. However, the product distribution seems unchanged except for the CO₂ for the platinum-promoted catalysts. Full article

For shaft parts, 45 steel has been widely used due to its favorable mechanical properties and low cost. However, the relatively low wear resistance of 45 steel limits its application. In this work, high-entropy alloy of FeCrCoMnSi_x (x = 0, 0.3, 0.6, 0.9, 1) coatings were prepared on the surface of a 45 steel substrate using laser cladding technology to improve the wear performance of 45 steel. The effect of the Si element on the microstructure and tribological property of these coatings is investigated. The results show that the structure of FeCrCoMn coatings is mainly an FCC + HCP dual-phase solid solution, grown in equiaxial crystals. When a small amount of Si (x = 0.3) is added, the BCC phase is generated in the coating; meanwhile, the microstructure is transformed into the divorced eutectic character. When the content of Si is x = 0.6, the eutectic structure is promoted, and the microstructure is refined and becomes denser. When the content of Si increases to x = 0.9 and 1.0, the metal silicate phase containing Mn and Cr is formed due to the precipitation of supersaturated solid solution. At the same time, the microstructure is transformed into dendritic crystals due to the composition super-cooling effect by the excessive Si element, inducing serious element segregation. The hardness of FeCrCoMnSi_x high-entropy alloy coatings increases to 425.8 HV when the Si content is 0.6 under the synergistic effect of the solid-solution and dense eutectic structure. The friction and wear analysis shows that the friction and wear mechanisms of the coating are mainly abrasive wear and oxidative wear. The coefficient of friction and the wear rate of the FeCrCoMnSi_x high-entropy alloy coating decreases to 0.202 and 4.06 × 10⁻⁵ mm³/N·m, respectively, when the content of Si is 0.6 due to the dense microstructure and high hardness. The above studies prove that the presence of Si in the FeCrCoMnSi_0.6 high-entropy alloy coating induces a refined eutectic microstructure and improves the coating’s anti-wear properties by increasing hardness and decreasing the coefficient of friction. Full article