查看更多>>摘要：The molybdenum disulfide (MoS2) and ZnO composite system have reported as micro-nano photonic crystals in integrated optics. Based on interface engineering, their tunable nonlinear absorption (NLA) and photoelectric characteristics offer a flexible design strategies for saturation absorber and optical limiters. Nevertheless, the mechanism leading to the tunable NLA behavior has not been clearly elucidated, which were attribute to complex charge transfers and carrier regulation characteristics. In this article, MoS2/ZnO heterostructures with excellent nonlinear properties composed of ZnO nanorods (NRs) wrapped with MoS2 nanosheets were prepared by magnetron sputtering (MS) synthesis of MoS2 on highly stacked ZnO NRs. The MoS2/ZnO heterostructures exhibit an interesting brush-like morphology with abundant heterointerfaces base on optimizing sputtering time and temperature, which was beneficial to provide efficient charge transfer pathways. Due to the uneven distribution of the lowest nucleation free energy, MoS2 nanosheets possess a hybrid mode of parallel (C//) and perpendicular orientations (C) on surface of ZnO NRs, which tends to form the bending and vertical growth of layered MoS2 nanosheets. From electron-photon coupling effect, MoS2 nanosheets, ZnO NRs and MoS2/ZnO heterostructures possess favorable saturation absorption (SA), reverse saturation absorption (RSA) and coexisting absorption behavior, respectively. In addition, a changeover from RSA to SA could be realized in MoS2/ZnO heterostructures by increasing the sputtering time. The NLA coefficient of MoS2/ZnO heterostructures are in the order of 10-10 cm/W, which are about 2 times larger than those of the ZnO NRs. Thus, the MoS2/ZnO heterostructures with excellent NLA properties will be promising candidates in optoelectronic devices.(C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A series of new transparent and magnetic barium gallogermanate glasses in the system (x) Gd2O3 - (100-x) [20BaO-15Ga(2)O(3)-65GeO(2)] with x = 0,8,14,18,22 and 25 mol% were synthesized. Their thermal, structural and magnetic properties were characterized. Based on the differential scanning calorimetry results, one determined the composition domain exhibiting the highest thermal stability toward crystallization and provided a detailed experimental fabrication method for the production of optical fibers. The local glass structure investigated using combined Raman and Infrared vibrational spectroscopies shows a progressive depolymerization of the 3D glass germanate network accompanied with an increase of non-bridging oxygens when increasing the Gd2O3 content. The incorporation of gadolinium ions tends to extend the IR transmission window. Thanks to the magnetic susceptibility measurements, the paramagnetic behavior was evidenced, and increases with the Gd3+ content. The combination of the optical, thermal and magnetic properties of Gd2O3 gallogermanate glasses as well as their ability to be shaped into optical fibers make them promising materials for their integration in MIR functional optical components. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：The glass formation, crystallization behavior, phase precipitation, and magnetic properties for a series of melt-spun Mn93-xSixB7 (x = 15, 20, 25, 30) amorphous ribbons were investigated. For x = 15 and 20 amorphous alloys, the crystallization shows one-stage behavior but different precipitated phases. For x = 25 amorphous alloy, a two-stage crystallization behavior occurs, in which the first and second crystallized peaks precipitate the Mn5Si3 and Mn2B, respectively. The broad maximum peak emerges at the temperature-dependent magnetization M(T) curves, indicating the amorphous alloys' spin glass (SG) behavior. Furthermore, the nanocrystalline and amorphous composite structure (NACS) consisting of the single nanocrystalline Mn5Si3 and amorphous phase can be achieved for the amorphous Mn93-xSixB7 alloy with x = 25 by controlling the annealing temperature and duration. The magnetic transitions of the NACS sample significantly differ from the counterpart of its amorphous state. The amorphous alloy undergoes the magnetic phase transition from SG into a paramagnetic state at about 20 K. In comparison, the annealed NACS sample first transforms the SG into a ferromagnetic state at about 15 K and then into a paramagnetic state around 300 K. The difference could attribute to the coupling effect between the nanocrystalline Mn5Si3 with the amorphous phase. (C)& nbsp;2022 Published by Elsevier B.V.
Papynov, E. K.Belov, A. A.Azon, S. A.Buravlev, I. Yu...
12页
查看更多>>摘要：An effective sorption material for the immobilization of cobalt radionuclides into highly safe and reliable solid-state matrices is proposed. The resulting silicate sorbent CaSiO3 had an amorphous mesoporous structure (ABET 53 m2/g) and a sorption capacity Co ions of 3.32 mmol/g. The physico-chemical characteristics of the CaCoSi2O6 sample obtained after Co2+ ions sorption were studied using XRD, N2 and Ar adsorption-desorption, SEM-EDX and TG/DTA methods. Solid-state silicate matrices characterized by high density values (2.86-3.16 g/cm3), compressive strength (150-637 MPa) and Vickers microhardness (1.80-5.25 GPa) were obtained by spark plasma sintering (SPS). The sample obtained at 1000 degrees C had the lowest values of Co2+ ions leaching (RCo ~10-7 g/(cm2xday)) and diffusion coefficient (De 1.73 x10-17 cm2/s) from silicate matrices. Thus, the obtained CaCoSi2O6 silicate matrices saturated with Co ions comply with the regulatory requirements of GOST R 50926-96 and ANSI/ANS 16.1 for 60Co immobilization. (c) 2022 Elsevier B.V. All rights reserved.
Moghaddam, Ahmad OstovariMikhailov, DmitryFereidonnejad, RaheleShaburova, Nataliya...
8页
查看更多>>摘要：High entropy intermetallic compounds (HEICs) are the most recent poster child of high entropy materials (HEMs), which provide a new paradigm to develop novel materials with potentially unusual properties. Here, FeNiCrV-TiNb, (Ni1/5-Co1/5-Fe1/5-Cu1/5-Mn1/5)3(Al1/2-Ti1/2), and (Fe1/5Ni1/5Co1/5Cr1/5Mn1/5)(Mo1/2Cr1/2) HEICs were fabricated by melting technique. The as-cast FeNiCrV-TiNb exhibited C14 Laves structure with varying chemical composition, which probably consists of two sub-lattices with slightly different lattice parameters. (Fe0.2Ni0.2Co0.2Cr0.2Mn0.2)(Mo0.5Cr0.5) crystalized into a single sigma-phase and revealed a homogenous microstructure with negligible segregation. A two-phase B2 +D03 structure with clear segregation of Cu, Fe, and Mn was obtained for (Ni0.2Co0.2Fe0.2Cu0.2Mn0.2)3(Al0.5Ti0.5) HEIC. The microhardness values were 915 Hv, 593 Hv, and 1051 Hv for FeNiCrV-TiNb, (Ni0.2Co0.2Fe0.2Cu0.2Mn0.2)3(Al0.5Ti0.5) and (Fe0.2Ni0.2Co0.2Cr0.2Mn0.2)(Mo0.5Cr0.5) HEICs, respectively. The last one is the highest value reported for an as-cast metallic HEM. (Ni0.2Co0.2Fe0.2Cu0.2Mn0.2)3(Al0.5Ti0.5) exhibited a soft magnetic behavior with a saturation magnetization of 27.7 emu/g and coercivity of ~ 311 Oe at 300 K, while FeNiCrV-TiNb and (Fe0.2Ni0.2Co0.2Cr0.2Mn0.2)(Mo0.5Cr0.5) showed an approximately linear dependency of magnetization vs. magnetic field. Finally, two modified parameters are introduced to expedite the discovery of new singlephase HEICs.
查看更多>>摘要：High-temperature deformation behaviors of a nonequiatomic novel AlNbTi3VZr1.5 refractory high entropy alloy were studied. Hot compression tests were carried out at different temperatures ranging from 1100 to 1250 celcius and various strain rates from 0.001 to 1 s(-1). The true stress-true strain curves indicated obvious sharp drops in the flow stress after reaching peak stress. This may be caused by either dislocation unlocking from a substitutional solute atmosphere or destroying short-range ordered structures. Flow stress analysis was investigated by introducing the Arrhenius constitutive relation. The apparent activation energy (Q) for high-temperature deformation was calculated to be 228.1 kJ/mol. The processing maps show that the best processing window was determined at 1200-1250 ?degrees C and 10-0.75 to 1 s(-1). Detailed microstructure evolution characterization with EBSD analysis shows that the occurrence of discontinuous dynamic recrystallization along grain boundaries is the main softening mechanism of the AlNbTi3VZr1.5 RHEA during the hot compression deformation. The size and volume percentage of dynamically recrystallized grains increase as the Z parameter decreases. (C)& nbsp;2022 Published by Elsevier B.V.
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