The article describes a method for producing semi-finished products from a copper alloy of the Cu–Ni–Cr–Si system for electrical purposes through the radial-shear rolling (RSR). From the Cu–Ni–Cr–Si ...alloy by hot deformation, rods with a diameter of 20 mm were obtained, which were then heat treated with quenching and aging. A detailed analysis of the microstructure and properties (mechanical and electrical) of the obtained samples was carried out after RSR and after heat treatment (HT). After RSR, material hardening occurs due to shear deformations forming a gradient structure with grain sizes varying from 8.22 μm to 15.95 μm between the surface and the center of the rod. The microstructure and mechanical property analysis showed that after heat treatment, the alloy is thermally hardened due to the precipitation of Ni2Si and Cr3Si particles uniformly distributed in the sample volume in the form of fine inclusions with an average size of 0.56–0.65 μm. After heat treatment, the alloy enhanced its mechanical properties (ultimate tensile strength (UTS) ~ 700–750 MPa, yield strength (YS) ~ 557–606 MPa, and elongation between 17 and 22%) and its electrical conductivity of 45.17% IACS from the 30.52% IACS of the RSR material. The improved mechanical properties of the heat-treated material are due to the different strength contributions mainly coming from dislocations and precipitates. The electrical conductivity improvement after the heat treatment is related to the dislocation density reduction and the increase in grain boundary misorientation due to the recrystallization phenomenon giving rise to a lower number of boundaries but with a twinning character. Thus, the RSR method offers a new industrial alternative for the production of semi-finished products from a Cu–Ni–Cr–Si alloy in the form of rods with diameters ranging from 10 to 55 mm.
•Radial shear rolling can produce copper rods of different diameters at an industrial scale.•The thermomechanical process using radial shear rolling gives rise to a heterogeneous material.•Aging treatment after radial shear rolling produces a remarkable combination of strength, ductility, and electrical conductivity.•Dislocations annihilation and grain boundaries misorientation change help to improve the material electrical conductivity.
The review is concerned with correlations between the synergistic effects and structural organization of the surface of bimetallic alloys that are used as active components of catalysts for selective ...hydrogenation of organic compounds and for CO oxidation in hydrogen-rich mixtures. Studies on the preparation of novel highly efficient catalysts using modern theoretical approaches, computer-assisted molecular design and original synthetic procedures are considered. It is shown that introduction of the second metal into the monometallic catalyst and subsequent formation of alloy particles with modified structure of the surface and near-surface layers leads to nonadditive enhancement of catalytic activity and/or selectivity. The bibliography includes 203 references.
Heisenberg-exchange-free nanoskyrmion mosaic Stepanov, E A; Nikolaev, S A; Dutreix, C ...
Journal of physics. Condensed matter,
05/2019, Letnik:
31, Številka:
17
Journal Article
Recenzirano
Odprti dostop
Isotropic Heisenberg exchange naturally appears as the main interaction in magnetism, usually favouring long-range spin-ordered phases. The anisotropic Dzyaloshinskii-Moriya interaction arises from ...relativistic corrections and is a priori much weaker, even though it may sufficiently compete with the isotropic one to yield new spin textures. In this work, we challenge this well-established paradigm, and propose to explore a Heisenberg-exchange-free magnetic world. In this case, the Dzyaloshinskii-Moriya interaction induces magnetic frustration in two dimensions, from which the competition with an external magnetic field results in a new mechanism producing skyrmions of nanoscale size. A single nanoskyrmion can already be stabilized in a few-atom cluster, and may then be used as LEGO® block to build a large magnetic mosaic. The realization of such topological spin nanotextures in sp- and p -electron compounds or in ultracold atomic gases would open a new route toward robust and compact magnetic memories.
Structure, reducibility and catalytic activity in the oxidation of CO were studied for Co-modified ZSM-5 zeolites (Co/Al = 0.1–0.9) prepared via impregnation, solid-state and wet ion exchange. ...According to TEM, XPS, DRIFTS, UV–vis-DRS, H2 -TPR and in situ CO- reduction studies the synthesis method and the Co content affect the surface distribution of Co as Со2+ ions, cationic oxo-complexes and highly dispersed CoxOy species. The oxidation of CO by oxygen was studied at 50–450 °C in pulse and flow regimes at the 2:1 and 1:1 CO:O2 ratios. Co-zeolites prepared by impregnation were the most active in the oxidation of CO. It was proposed that oxo cations CoxOyn+ (n = 1, 2) with Co(III) prevailing in their structure play a crucial role in CO adsorption and catalytic oxidation. The new absorption band at 2215 cm−1 attributed to CO adsorbed on the Co(III) located in oxo cations was found. These oxo-cations contain a mobile oxygen atoms and, thus, can be easily reduced to the catalytically active Сo3+/Сo2+and Сo2+/Сo+ pairs stabilized in zeolites. In contrast to the supported catalysts based on Co3O4, the activity of Co-ZSM-5 increased during the reaction, and the light-off T50 drifted to 120 °C.
Display omitted
•Structure-performance relationship was found for Co-ZSM-5 (Co/Al = 0.1–0.9) prepared by different methods.•Wetness impregnation with cobalt acetate produces mainly Co-oxo cations.•Formation of Co-oxo cations with Со(III) was proved by DRIFTS in situ studies of adsorbed CO.•The most reducible Co(III)xOyn+ cations provides high activity and stability of Co- ZSM- 5 in CO oxidation.
Studies in experimental systems have identified a multitude of mutational mechanisms including DNA replication infidelity and DNA damage followed by inefficient repair or replicative bypass. However, ...the relative contributions of these mechanisms to human germline mutation remain unknown. Here, we show that error-prone damage bypass on the lagging strand plays a major role in human mutagenesis. Transcription-coupled DNA repair removes lesions on the transcribed strand; lesions on the non-transcribed strand are preferentially converted into mutations. In human polymorphism we detect a striking similarity between mutation types predominant on the non-transcribed strand and on the strand lagging during replication. Moreover, damage-induced mutations in cancers accumulate asymmetrically with respect to the direction of replication, suggesting that DNA lesions are resolved asymmetrically. We experimentally demonstrate that replication delay greatly attenuates the mutagenic effect of ultraviolet irradiation, confirming that replication converts DNA damage into mutations. We estimate that at least 10% of human mutations arise due to DNA damage.
The influence of a degree of strain by rotary forging, as well as post-deformation annealing on the structure and mechanical properties of a clad aluminum alloy/copper bimetallic material was ...studied. Rotary forging of the initial bimetallic billet was carried out step by step from a diameter of 20.1 mm to a diameter of 2.4 mm. Rotary forging of the aluminum alloy/copper bimetallic material to a diameter of 5.3 mm leads to the formation of a mixed fine-grained and nanocrystalline oriented structure in an aluminum shell and to a decrease in the average grain size by 4.5 times and to an increase in the density of crystalline defects in a copper core. A reduction in the aluminum alloy/copper bimetallic material diameter to 2.4 mm (with intermediate annealing) leads to the formation of a fine-grained elongated grain-subgrain oriented structure in the aluminum shell and to the formation of a mixed cellular and subgrain structure in a copper core. Rotary forging leads to a significant increase in the strength of the aluminum alloy/copper bimetallic material and to a decrease in ductility. The optimal combination of increased strength and satisfactory ductility provides post-deformation annealing.
Graphic Abstract
We present theoretical studies of the intrinsic spin-orbit torque (SOT) in a single-domain ferromagnetic layer with Rashba spin-orbit coupling (SOC) using the nonequilibrium Green's function ...formalism for a tight-binding Hamiltonian. We find that, in the case of a small electric field, the intrinsic SOT to first order in SOC has only the field-like torque symmetry and can be interpreted as the longitudinal spin current induced by the charge current and Rashba field. We analyze the results in terms of the material-related parameters of the electronic structure, such as the band filling, bandwidth, exchange splitting, and the Rashba SOC strength. On the basis of these numerical and analytical results, we discuss the magnitude and sign of SOT. Our results suggest that the different sign of SOT in identical ferromagnets with different supporting layers, e.g., Co/Pt and Co/Ta, can be attributed to electrostatic doping of the ferromagnetic layer by the support.
Posttranslational modifications in fibrinogen resulting from induced oxidation or oxidative stress in the organism can have deleterious influence on optimal functioning of fibrinogen, causing a ...disturbance in assembly and properties of fibrin. The protective mechanism supporting the ability of fibrinogen to function in ROS-generating environment remains completely unexplored. The effects of very low and moderately low HOCl/−OCl concentrations on fibrinogen oxidative modifications, the fibrin network structure as well as the kinetics of both fibrinogen-to-fibrin conversion and fibrin hydrolysis have been explored in the current study. As opposed to 25 Μm, HOCl/−OCl, 10 μM HOCl/−OCl did not affect the functional activity of fibrinogen. It is shown for the first time that a number of Met residues, AαMet476, AαMet517, AαMet584, BβMet367, γMet264, and γMet94, identified in 10 μM HOCl/–OCl fibrinogen by the HPLC-MS/MS method, operate as ROS scavengers, performing an important antioxidant function. In turn, this indicates that the fibrinogen structure is adapted to the detrimental action of ROS. The results obtained in our study provide evidence for a protective mechanism responsible for maintaining the structure and functioning of fibrinogen molecules in the bloodstream under conditions of mild and moderate oxidative stress.
•Fibrinogen treated with 10 μM HOCl/−OCl did not lose the functional activity.•Methionines in fibrinogen were the main target for 10 μM HOCl/−OCl.•Some of Met residues in the fibrinogen structure operate as endogenous antioxidants.•The fibrinogen structure is supposed to be adapted to the action of ROS.
The structural inhomogeneities of silicon films embedded within W/Si multilayer mirrors were studied by X‐ray reflection, grazing‐incidence small‐angle X‐ray scattering (GISAXS) and X‐ray ...photoelectron spectroscopy (XPS). In the diffuse scattering spectra, evidence of laterally and vertically ordered in‐layer inhomogeneities was consistently observed. In particular, specific substructures resonant in nature (named here `ridges') were detected. The properties of the ridges were similar to the roughness determined by quasi‐Bragg peaks of scattering, which required a high interlayer correlation of particles. The XPS showed the nanocrystalline nature of the Si particles in the amorphous matrix. The geometric characteristics and in‐layer and inter‐layer correlations of the nanoparticles were determined. In GISAXS imaging, the unusual splitting of the waists between the Bragg sheets into filament structures was observed, whose physical nature cannot yet be explained.
The nature of the observed bulk inhomogeneities in the silicon layers in W/Si multilayers is established. In the diffuse scattering spectra, specific substructures, which are clearly resonant in nature, are observed. The physical nature of some of them is not established.
PDF
