Rare Metals

The exchange coupling at the ferromagnetic/antiferromagnetic (FM/AFM) interface is influenced by both the magnetic structure and the crystalline micro-structure. Co/FeMn/Co thin films with 0.4 nm Pt spacer layer inserted into the Co/FeMn and FeMn/Co interface respectively were deposited by means of magnetron sputtering. The two interfaces upon and beneath the FeMn layer show distinct behaviors before and after the Pt spacer inserted. There is a remarkable shrink of the interfacial uncompensated spins within the FeMn bottom interfacial monolayers, whereas a relaxation of the pinning strength of the FeMn interfacial spins along the out-of-plane direction occurs at the top interface. XRD analysis indicates the Pt layer upon the FeMn layer forms an fcc (002) texture, implying the magnetic discrepancy between the top and bottom FeMn interfaces has crystalline structural origins.

Monodispersed spherical Ru powders are essential for fabricating high-performance Ru sputtering targets, which have applications in very-large-scale integration circuits and magnetic recording devices. However, the synthesis of such powders remains a major challenge. Here, we reported the synthesis of monodispersed spherical Ru powders through controlling the molar ratio of SO42− to Ru3+ in urea homogeneous precipitation solution and the annealing conditions. Without the addition of (NH4)2SO4 into the reaction solution, only gel-like precipitation particles were obtained. Once introducing (NH4)2SO4 into the reaction solution and controlling the molar ratio of SO42− to Ru3+ between 0.50 and 1.00, monodispersed spherical precursor powders were obtained. The nucleation and growth of monodispersed spherical precursor particles in solution were found to conform to LaMer’s model. Through controlled annealing at 450 °C in a hydrogen atmosphere, the obtained metallic Ru powder with an average particle size of 135 nm inherited the spherical morphology and excellent dispersity from the monodispersed spherical precursor powders. These results and findings would deepen the understanding of the preparation of monodispersed Ru and Ru-like powders.

Rare metals play an important role in development of superalloys. Over the last two decades, the application of the rare metals in superalloys has achieved progress significantly. They present multi-beneficial effects for strengthening the matrix and the γ′ phase, increasing the lattice misfit, cleaning the grain boundary, improving the carbides and eutectics, refining the grain, stabilizing the oxidation film, etc., so that the elevated temperature rupture life and elevated temperature oxidation resistance are improved significantly, leading to a broad application in the superalloys. In order to meet the higher demand for better superalloys in the future, more intensive research is necessary on the effects of the rare metals on the superalloy, and especially on the combination effect of various rare metals and mutual influence among them. Utilization of the computational materials science and combinatorial high throughput experiment will be of importance in application of rare metals in superalloys.

In this study, an electrochemical impedimetric sensor was established for imidacloprid (IMI) detection based on WO3/MoS2 and molecular imprinted polymer (MIP) composite. MIP layer was prepared on electrode surface by electropolymerization of o-phenylenediamine (o–PD) in the presence of IMI template, which ensured the specific recognization toward IMI. The electrochemical properties of fluorine-doped Tin oxide (FTO)/WO3/MoS2/MIP electrode were studied via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The prepared sensor exhibits low detection limit (0.1 μmol·L−1) with a wide concentration range from 0.5 to 70.0 μmol·L−1. Moreover, this sensor shows high recoveries in real sample testing, revealing good application prospect.

A systematic microstructure-oriented magnetic property investigation for Al/CoCrFeNi nanocrystalline high-entropy alloys composite (nc-HEAC) is presented. In the initial state, the Al/CoCrFeNi nc-HEAC is composed of face-centered cubic (FCC)-Al, FCC-CoCrFeNi and hexagonal close-packed (HCP)-CoNi phases. High energy synchrotron radiation X-ray diffraction and high-resolution transmission electron microscopy were used to reveal the relationship between microstructure evolution and magnetic mechanism of Al/CoCrFeNi nc-HEAC during heat treatment. At low-temperature annealing stage, the magnetic properties are mainly contributed by the HCP-CoNi phase. With the increase of temperature, the diffusion-induced phase transition process including the transformation of AlCoCrFeNi HEA from FCC to BCC structure and the growth of B2 phase plays a dominant role in the magnetic properties. It was found that the magnetic properties can be effectively regulated through the control of the thermal diffusion process. The nano dual-phase thermal diffusion-induced phase transition behavior of nanocomposites prepared based on laser-IGC technology provides guidance for the diffusion process and microstructure evolution of two phases in composites.

This study focuses on the effects of different cold-drawing deformations and aging treatments of solid solution A286 superalloy. The grain configuration, texture, precipitates and tensile strength of A286 superalloy after different deformations and aging treatments were investigated by optical microscopy (OM), field emission scanning electron microscopy (FESEM), electron back-scattered diffraction (EBSD) and mechanical testing machine. The grain size and configuration of A286 alloy can hardly be changed during aging process. The initially equiaxial and twinned crystals are obvious when deformation is less than 30%, while the grain boundaries become blurry and slip bands appear after 35% deformation or more. γ′ phase and Cr-rich carbide are the precipitates of A286 alloy. For each deformation, γ′ phase plays a major role during aging and its amount increases gradually when the aging temperature changes from 650 to 680 °C, and a maximum tensile strength appears when following two-stage aging. With deformation increasing, the amounts of γ′ phase and Cr-rich carbide increase in varying degrees. Meanwhile, the <111> wire textures become more obvious, the tensile strength is enhanced and the kernel average misorientation (KAM) increases gradually; the higher KAM of crystal lattices diffuses from the grain boundary to the matrix gradually.