查看更多>>摘要：? 2022 Elsevier B.V.A gradient nanostructured (GNS) surface layer was generated in a dual-phase Cu-Ag alloy by means of surface mechanical grinding treatment at liquid nitrogen temperature. With a decreasing depth in the surface layer, the coarse-grained microstructure of Cu matrix and Ag precipitates gradually converts into a nanolaminated structure of Ag- and Cu-rich phases with simultaneous chemical mixing, and finally forms a homogeneous single-phase supersaturated solid solution (SSS) nanostructure. Accordingly, a dislocation-mediated transportation mechanism was proposed to dominate the chemical mixing of Ag and Cu atoms, i.e., dislocations interacting with solution atoms penetrate the Cu/Ag interface and glide in the neighboring solvent-phase lamella.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, we investigate the influence of grain boundary character on isothermal phase transformation and mechanical properties of selective laser melting (SLM) fabricated Co-Cr-Mo alloy. The grain boundary engineering (GBE) was used to manipulate the isothermal phase transformation and precipitation. The As-SLM Co-Cr-Mo and GBE Co-Cr-Mo alloys were isothermal treatment at 800 ℃ for 6 h in a muffle furnace, followed by air cooling, respectively. It was found that the high density of stacking faults and low-angle boundaries in As-SLM Co-Cr-Mo alloy accelerated the phase transformation of γ-Co to ε-Co and Laves phase precipitation, which improved the tensile strength and drastically deteriorated the ductility. While, the high fraction of twin boundaries in GBE Co-Cr-Mo alloy retard the isothermal phase transformation and improve the resistance to Laves phase precipitation, which nearly maintain the high mechanical performance after the same isothermal treatment. The results of this study can be a guide to fabricate high-performance Co-Cr-Mo alloy according to work conditions.
查看更多>>摘要：? 2022 Elsevier B.V.Laser cladding technology, a promising surface modification method adopted to fabricate a high entropy alloy (HEA) coating on the surface of TC4 titanium alloy, can competently solve the problems of wear, corrosion and fracture of titanium alloy in practical applications. The current study utilized a finite element model to investigate the influence of powder layer thickness and process parameters on the stress field. The effect mechanism of stress on cracks was preliminarily explored based on the simulation results of the stress field. The cracks in the FeCoCrNi HEA coating were classified, and their initiation and propagation mechanism was interpreted. The influence of single-factor and double-factor interactions on the crack rate was evaluated combined with the experimental and simulation results. Linear regression analysis was performed to propose empirical-statistical correlations between the key processing parameters and the crack rate of the FeCoCrNi HEA coating. The results indicated that the interaction between laser power and scanning speed significantly impacts the crack rate of the FeCoCrNi HEA coating. The maximum stress value in the fusion zone at the bottom of the coating demonstrates that crack initiation and propagation are prone to materialize in this zone. This study provides a referenced value on the excellent crack control and the comprehensive properties improvement of the coating in high entropy alloy laser cladding.
查看更多>>摘要：? 2022 Elsevier B.V.We have succeeded in growing α-DyGa3 single crystals by the self-flux method and determined its magnetic structure by neutron powder diffraction. α-DyGa3 crystallizes in the rhombohedral SrSn3-type structure (R3?m, #166, hR48), and the magnetic sublattice is comprised of staggering layers of triangular lattice of Dy. Magnetic ordering occurs below TN ~ 7.2 K with the magnetic propagation vector k = (1/2, 0, 1/2), results in an alternating stripe antiferromagnetic structure in the ab-plane described by the magnetic space group CC2/c (BNS #15.90, origin at (0, 0, 0)). At 3.5 K, the magnetic moment is 5.72(12) μB per Dy3+. The Dy3+ spins are lying in basal plane and perpendicular to the b-axis.
查看更多>>摘要：? 2022 Elsevier B.V.The structure, transport properties, and ΔR/R ultrafast spectra of Bi2TexSe3-x crystals are studied in this work. The lattice parameter c and saturation temperature of resistance increase with increasing Te concentration. There are two electron-phonon coupling processes in Bi2TexSe3-x crystals corresponding to the interactions between two topological surface states and phonons. The electron-phonon coupling of one surface state is dominant at low temperatures (T ≤ 40 K), and the coupling of the second surface state and phonon is significant. With increasing temperature, electron-phonon coupling in bulk Bi2TexSe3?x is enhanced, which weakens electron-phonon coupling of its surface states. A small amount of Te has little effect on the electron-phonon coupling for Bi2Se3 crystals.
查看更多>>摘要：? 2022 Elsevier B.V.The new ZnAl2O4-coated LiFePO4 (ZnAl2O4@LFP) electrode was prepared via polypropylene glycol-assisted sol-gel method and investigated as a cathode material in Li-ion batteries. The pure LFP and ZnAl2O4-coated LFP electrodes were characterized using XRD, HRTEM, FESEM/EDS/mapping and XPS techniques. XRD data affirmed the creation of LFP phase with good crystallinity. TEM revealed that the pure LFP and ZnAl2O4-coated LFP electrodes crystallized with spherical-like shape. However, the ZnAl2O4-coated LFP electrode offered greater crystallite size than that of pure LFP electrode. The typical atomic state of these electrodes was examined through XPS. Additionally, EDS analysis provided an actual evidence for the visualization mapping of each element, signifying the success of coating process on the surface of LFP electrodes. Furthermore, the ZnAl2O4@LFP electrode demonstrated higher charge and discharge capacities ~ 122 and 95 mAhg?1, respectively. The coulombic efficiency of ZnAl2O4@LFP electrode was significantly enhanced from 80% in the 1st cycle to 99.8% in the 8th cycle, indicating excellent stability over the following cycles. Accordingly, the ZnAl2O4 layer played a vital role for improving the structural stability and electrochemical performance of a LFP cathode. Combined with the admirable electrochemical performance of ZnAl2O4@LFP, this will attract the interest for the future development of potential cathode materials.
查看更多>>摘要：? 2022 Elsevier B.V.Preparing low-cost and multifunctional phosphor is an important and challenging job. In this paper, a high-purity self-activated LiGaSiO4 phosphor has been successfully synthesized by the high-temperature solid-state method, which can emit near-infrared light peaking at 697 nm. The reversible thermochromic phenomenon can be observed by heat-treating LiGaSiO4 compounds in different atmospheres. The luminescent mechanism and thermochromic phenomenon are studied in detail by photoluminescence spectrum, electron paramagnetic resonance and the first principle calculations. The results show that oxygen vacancies in LiGaSiO4 compounds play an important role in the near-infrared luminescence process. Based on this luminescent mechanism, a series of LiGaSi(1-x)GexO4 (x = 0.2, 0.4, 0.6, 0.8, 1.0) self-activated phosphors have been fabricated and the corresponding luminescent modulation has been inferred. The results indicate that thermochromic LiGaSi(1-x)GexO4 phosphors can be used as special anti-counterfeiting and bio-imaging materials.
查看更多>>摘要：? 2022 Elsevier B.V.Acyclovir (ACV), despite its good properties may be harmful to the body. So, its monitoring is important. In this work, a novel silver nanoparticles/cadmium sulfide nanowires/reduced graphene oxide nanocomposite (Ag NPs/CdS NWs/RG) was successfully prepared and used as an excellent modifier for the electrochemical detection of ACV. The formation of nanocomposite was approved through different techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and EIS. The Ag NPs/CdS NWs/RG modified glassy carbon electrode (GCE) was used for monitoring ACV by differential pulse adsorptive anodic stripping voltammetry (DPAASV) method. The fabricated sensor presented a good linearity in the ranges of 10 nM-4 μM and 4–40 μM, with an outstanding detection limit of 3.3 nM. The fabricated sensor offered satisfactory performance in the quantitative detection of ACV in blood serum, tablet, and topical cream samples.
查看更多>>摘要：? 2022 Elsevier B.V.Molybdate materials have proved to be potential anode because of their superior specific capacity, stable three-dimensional framework structure and fast lithium-ion transport ability. However, the low-temperature properties and electrochemical reaction mechanism still lack in-depth research. Here, two molybdate materials, LiCr(MoO4)2/C and Li3Cr(MoO4)3/C, are synthesized by a sample ball-milling assisted high-temperature solid state method and studied as anode materials for lithium-ion batteries (LIBs) at room temperature and low temperature. Between 0.01 V and 3.00 V, LiCr(MoO4)2/C and Li3Cr(MoO4)3/C exhibit high specific capacities of 1158 and 1077 mA h·g?1 at 50 mA·g?1 at 25 °C, respectively. LiCr(MoO4)2/C delivers a high specific capacity of 352 mA h·g?1 at a high current density of 5000 mA·g?1. After 500 cycles, LiCr(MoO4)2/C and Li3Cr(MoO4)3/C both retain reversible capacities over 600 mA h·g?1 at 250 mA·g?1. Even at low temperature of 0 °C, ? 10 °C, ? 20 °C, Li3Cr(MoO4)3/C still delivers high capacities of 1061, 891 and 742 mA h·g?1, respectively. Ex-situ X-ray diffraction (XRD) is conducted to study the electrochemical reaction mechanism. Moreover, low-temperature cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests are used to explore the limitations of low-temperature performance. This work provides low-temperature anode material for LIBs and deepens the understanding of low-temperature performance.
查看更多>>摘要：? 2022 Elsevier B.V.Introducing heterogeneous interfaces by constructing laminated structure is a promising avenue to achieve the controllable strengthening behavior of high entropy alloys. In this work, the microstructural evolution and mechanical properties of magnetron sputtered Ni/Fe50Mn30Co10Ni10 nanolaminates with equal layer thickness h ranging from 5 to 150 nm were investigated systematically. With reducing h, the nanoindentation hardness of Ni/FeMnCoNi nanolaminates firstly increased and subsequently decreased, emerging a maximum value at the critical h of ~25 nm due to the transformation of constraining barrier for dislocation slipping from the heterogeneous interfaces to columnar grain boundaries. Microstructural observation demonstrated that the interfacial structure of Ni/FeMnCoNi transformed from incoherent to completely coherent at h below ~25 nm, and both the constituent layers made comparable contribution to the plastic deformation of Ni/FeMnCoNi nanolaminates. The strong h-dependent mechanical behavior could be rationalized in terms of the co-deformation of constituent layers and the structural evolution of Ni/FeMnCoNi interface. Additionally, the strengthening mechanisms were discussed based on the confined slip of dislocation within the constituent layers and columnar grains.
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