Search results for "MATTER"
showing 10 items of 16762 documents
EBSD, XRD and SRS characterization of a casting Al-7wt%Si alloy processed by equal channel angular extrusion: Dislocation density evaluation
2019
Abstract Aluminum‑silicon (Al Si) alloys of high silicon contents are composite materials; they are used whenever high casting properties are required. They are slightly ductile below 8wt%Si. An increase in ductility can be obtained by refining Si-crystals in elaboration or by a further hot working. In the present work, an Al-7wt%Si alloy was processed by Equal Channel Angular Extrusion (ECAE) at temperatures 20 °C and 160 °C up to three passes. The die was formed by two cylindrical channels with characteristic angles Φ = 110° and Ψ = 0. EBSD, X ray diffraction (XRD) and Strain Rate Sensitivity (SRS) were used to characterize the microstructure and the mechanical properties. High levels of …
Influence of spray trajectories on characteristics of cold-sprayed copper deposits
2021
Abstract Industrial robots are widely used in cold spray (CS) as well as thermal spray to produce various coatings by precisely controlling kinematic parameters during the process. However, the robot trajectory and its effect on the characteristics of CS deposits are important, but not fully studied. This article introduces four typical spray trajectories, including zigzag path, cross path, parallel path, and spiral path, to elaborate thick CS Cu deposits, and characterizes the corresponding Cu deposits, respectively. The experimental results revealed that the spray trajectories have a major influence on the associated thermal history and the residual stress distribution. However, no signif…
Effect of surface finishing on the oxidation behaviour of a ferritic stainless steel
2017
Abstract The corrosion behaviour and the oxidation mechanism of a ferritic stainless steel, K41X (AISI 441), were evaluated at 800 °C in water vapour hydrogen enriched atmosphere. Mirror polished samples were compared to as-rolled K41X material. Two different oxidation behaviours were observed depending on the surface finishing: a protective double (Cr,Mn) 3 O 4 /Cr 2 O 3 scale formed on the polished samples whereas external Fe 3 O 4 and (Cr,Fe) 2 O 3 oxides grew on the raw steel. Moreover, isotopic marker experiments combined with SIMS analyses revealed different growth mechanisms. The influence of surface finishing on the corrosion products and growth mechanisms was apprehended by means o…
Tuning the electronic and magnetic properties of 2D g-GaN by H adsorption: An ab-initio study
2019
Abstract We have theoretically studied the structural, electronic and magnetic properties of the hydrogen adsorption on a honeycomb gallium-nitride two-dimensional monolayer (2D g-GaN). Results indicate that the band gap energy can be systematically tuned by the hydrogen coverage on the 2D g-GaN in the diluted limit. In addition, a total magnetic moment can be induced in the 2D g-GaN by hydrogen adsorption due to s-p interaction and band structure effects. Although hydrogen adsorption on top of nitrogen atoms shows the most stable energy in the 2D g-GaN, the most stable ferromagnetism -with a nonzero magnetic moment-is obtained when hydrogen is adsorbed on top of Ga atoms. These results ind…
Zn-substituted iron oxide nanoparticles from thermal decomposition and their thermally treated derivatives for magnetic solid-phase extraction
2020
Abstract Controlled thermal decomposition of zinc and iron acetylacetonates in the presence of oleic acid and oleylamine provided surfactant-capped magnetic nanoparticles with narrow size distribution and the mean diameter of ≈15 nm. The combined study by XRD, XRF and Mossbauer spectroscopy revealed three important features of the as-prepared nanoparticles. First, the actual ratio of Zn:Fe was considerably lower in the product compared to the initial ratio of metal precursors (0.14 vs. 0.50). Second, a pure stoichiometric Zn-doped magnetite system, specifically of the composition Zn0.37Fe2.63O4, with no signatures of oxidation to maghemite was formed. Third, Zn2+ ions were distributed at bo…
Mechanical properties of macroscopic magnetocrystals
2019
Abstract We studied experimentally and by numerical simulations the mechanical response of arrays of macroscopic magnetic spheres when an external stress is applied. First, the tensile strength of single chains and ribbons was analyzed. Then, simple cubic (cP), hexagonal (Hx) and hybrid (cP-Hx) structures, called here magnetocrystals , were assembled and subjected to tensile stress, bending stress and torsion until failure was reached. Atomistic crystalline structures are isotropic, but in the case of magnetocrystals, even when geometric isotropy is obeyed, dipolar magnetic interactions introduce a physical anisotropy which modifies, in a non-usual manner, the structures response to the kin…
Magneto-optical properties of two-layer film systems based on Fe and Cr
2020
The results of the investigation of two-layer Fe/Cr systems using the magneto-optical Kerr effect (MOKE) are presented in this paper. The samples were obtained by thermal evaporation in a vacuum with a thickness of individual layers from 2 nm to 50 nm. It was found that the presence of the Cr layer significantly affects the values of the coercivity and the Kerr angle. At a substrate temperature of 450 K, the value of the coercivity is almost half that of the same sample obtained at room temperature of the substrate. In addition, the influence of the order of deposition of layers, as well as the effect of a thin gold protective layer on the parameters measured by the Kerr method, is shown. …
The effect of magnetocrystalline anisotropy on the domain structure of patterned Fe2CrSi Heusler alloy thin films
2013
The effects of magnetic anisotropy on domain structures in half-metallic Heusler alloy Fe2CrSi thin film elements were investigated using high resolution x-ray magnetic circular dichroism photoemission electron microscopy. The transition of the dominating contribution from the magnetocrystalline anisotropy to the shape anisotropy is observed in square-shaped elements when reducing the size below 2.0–2.5 μm. In particular, we identify in disk-shaped Heusler elements the vortex state as the ground state. The shape-anisotropy dominated, well-defined magnetization configuration shows the potential of the Fe2CrSi Heusler alloy for applications in vortex-core- or domain-wall-devices, where the hi…
Neutron diffraction study of microstructural and magnetic effects in fine particle NiO powders
2016
Nickel oxide powders with grain sizes ranging from 100 to 1500 nm have been studied by high-resolution neutron diffraction. We have found that the atomic structure, the antiferromagnetic ordering, and the value of the nickel magnetic moments inherent in the bulk material of NiO are still preserved and are nearly independent of the average size of the grains. The sizes of the coherently scattering atomic and magnetic domains were estimated independently owing to a complete separation of the nuclear and magnetic peaks in the neutron diffraction patterns. It is shown that the finite-size and surface disorder effects in particles at the submicron scale have a more pronounced influence on the ma…
Recent progress in understanding the persistent luminescence in SrAl 2 O 4 :Eu,Dy
2019
Ever since the discovery of SrAl2O4:Eu,Dy persistent afterglow material, that can intensively glow up to 20 h, the mechanism of long-lasting luminescence has been a popular area of research. The re...