Search

Herein, the ordered structure of Co-based metallic microwires was modulated by direct current-annealing, thereby improving the tensile mechanical properties. Based on the thermophysical parameters of the metallic microwires, the annealing current intensities of 65 mA, 90 mA and 150 mA were determined by the method of numerical calculation. The experimental results indicated that the ordered structure of the metallic microwires was regulated under the action of Joule heating, and with the rising of the annealing current, the ordered structure increased and the distribution tended to be concentrated. The 90 mA current-annealed metallic microwires have favorable tensile mechanical properties and fracture reliability, with the tensile strength and elongation of 4540.10 MPa and 2.99%, respectively, and the fracture threshold is 1910.90 MPa. Both the as-cast and current-annealed metallic microwires were brittle fractures, and the fractures consisted of shear deformation regions and crack extension regions. The improvement of the mechanical properties of metallic microwires is related to the nano-ordered structure and their distribution. Under the condition of 90 mA current annealing, the uniformly distributed nano-ordered structures were formed in the amorphous matrix of the metallic microwires, which can effectively slow down the expansion of the shear bands and reduce the possibility of crack generation. This study provides process reference and theoretical guidance for the application of Co-based metallic microwires in the field of stress sensors. [ABSTRACT FROM AUTHOR]

Herein, the effect of Ni-doping amount on microstructure, magnetic and mechanical properties of Fe-based metallic microwires was systematically investigated further to reveal the influence mechanism of Ni-doping on the microstructure and properties of metallic microwires. Experimental results indicate that the rotated-dipping Fe-based microwires structure is an amorphous and nanocrystalline biphasic structure; the wire surface is smooth, uniform and continuous, without obvious macro- and micro-defects that have favorable thermal stability; and moreover, the degree of wire structure order increases with an increase in Ni-doping amount. Meanwhile, FeSiBNi2 microwires possess the better softly magnetic properties than the other wires with different Ni-doping, and their main magnetic performance indexes of Ms, Mr, Hc and μm are 174.06 emu/g, 10.82 emu/g, 33.08 Oe and 0.43, respectively. Appropriate Ni-doping amount can effectively improve the tensile strength of Fe-based microwires, and the tensile strength of FeSiBNi3 microwires is the largest of all, reaching 2518 MPa. Weibull statistical analysis also indicates that the fracture reliability of FeSiBNi2 microwires is much better and its fracture threshold value σu is 1488 MPa. However, Fe-based microwires on macroscopic exhibit the brittle fracture feature, and the angle of sideview fracture θ decreases as Ni-doping amount increases, which also reveals the certain plasticity due to a certain amount of nanocrystalline in the microwires structure, also including a huge amount of shear bands in the sideview fracture and a few molten drops in the cross-section fracture. Therefore, Ni-doped Fe-based metallic microwires can be used as the functional integrated materials in practical engineering application as for their unique magnetic and mechanical performances. [ABSTRACT FROM AUTHOR]

The effects of trace Fe-doping on the magnetic and magnetocaloric performances of Gd-based metallic microfibers were systematically and detailedly investigated in this article. Experimental results indicated that the Gd-based microfibers prepared by the rotated-dipping process are uniform and continuous, with typically amorphous structure characteristics and favorable thermal stability. Curie temperature T C of Gd-based amorphous microfibers increases with the rising of Fe content, and the T C of GdAlCoFe3 microfibers is the highest at 128.7 K (relatively increased by 15.3 K than before doping). Among the general magnetic performance indicators, the saturation magnetization M s of GdAlCoFe2 microfibers reaches a peak at 264.04 emu/g. Furthermore, the values of magnetocaloric performance indexes of Gd-based amorphous microfibers increase firstly and then decrease with the rising of Fe-doping amount. When the external magnetic field H ex = 50,000 Oe, the maximum magnetic entropy change -Δ S m max, refrigeration capacity RC and relative cooling power RCP of GdAlCoFe1 microfibers are 10.33 J/kg·K, 748.22 J/kg and 1006.90 J/kg, which increased by 0.07 times, 0.13 times and 0.16 times, respectively than before Fe-doping (namely -Δ S m max = 9.68 J/kg·K, RC = 663.79 J/kg, RCP = 871.73 J/kg). From the perspective of microstructural changes, Fe-doping results in the formation tendency of atomic clusters and nanocrystals in micro-regions, the orderly orientation of atoms appears, and the magnetic anisotropy increases accordingly. In addition, the 3d electron layer of the doped Fe element in Gd-Al-Co-Fe quaternary alloy system enhances the RKKY indirectly exchange coupling interaction and changes the state of magnetic entropy, which in turn leads to an increase in Curie temperature and an improvement in magnetocaloric performance. Since RC and RCP are the main indicators in engineering applications, the GdAlCoFe1 amorphous microfibers can be selected as a low-temperature magnetic refrigeration working medium to provide technical guarantee for the application of magnetic refrigeration technology. In comparison to Fe-doped Gd-based amorphous microfibers, # GdAlCoFe1 microfibers have enhanced magnetocaloric properties by coactions of atomic arrangement ordering transformation (AAOT) and magnetic moment ordering transformation (MMOT). Image 1 • Influence of Fe-doping amounts on the magnetocaloric properties was investigated systematically. • MCE properties of # GdAlCoFe1 amorphous fibers were enhanced effectively. • Interaction mechanism was illustrated from the perspective of atomic arrangement and magnetic moment ordering transformation. [ABSTRACT FROM AUTHOR]

Underwater wireless optical communications (UWOCs) use beam shaping techniques such as the Beer-Lambert (BL) law which describes how light interacts with matter. The BL model ignores the scattering effect of UWOC, while the beam spread function (BSF) can characterize the combined effect of absorption and scattering of UWOC more accurately. The original triple-integral beam spread function (OTI-BSF) involves the Bessel function, which is very time-consuming to calculate. In addition, different seawater environments may require different scattering phase functions (SPFs) to obtain accurate modeling results compared with Henyey-Greenstein SPF (HG-SPF). So far, the BSF-based channel data generation and performance analysis in complex water environments have been time-consuming. We propose a unified simplification of BSF (US-BSF) channel based on the Gaussian mixture model, which is suitable for three commonly used SPFs. From the point of view of time consumption, our proposed US-BSF only requires an order of O(10 -4 ) s to calculate a value on average, while the OTI-BSF requires an order of O(10 2 ) s.