查看更多>>摘要：Here, we present the results of the synthesis of a complex hydride previously described as Mg2(Fe, Cr, Ni)Hx formed during the reactive ball milling process of AISI 316 L stainless steel (316 L SS) and magnesium hydride under hydrogen pressure. The evolution of powder morphology and phase composition with milling time is presented. The reaction of magnesium hydride with 316 L steel was found to proceed faster than in case of the reaction of reference mixture containing pure iron. Obtained material was found to possess cubic K2PtCl6-structure with slightly different lattice parameter as compared to Mg2FeH6. The hydrogen content of the obtained samples was found to be around 4 wt%. The mixture that resulted from the decomposition of this synthesized sample was able to absorb around 1% of hydrogen even at ? 50 ℃ via the formation of magnesium hydride.
查看更多>>摘要：The wide bandgap and low photocatalytic efficiency are acknowledged as the main problems of the photocatalytic activities of TiO2. Herein, an effective strategy combing defect engineering and heteroatom doping is developed to expand the region covering visible light response and construct the active surface. A plasma-induced carbon doping (PICD) method is adopted to achieve a binary core-shell structure containing outer defect-layer shell of oxygen vacancy and inside crystalline anatase TiO2 core (~ 5 nm). The outstanding photocatalytic activity for visible-light-driven degradation of RhB and MO originates from narrowed bandgap (~ 2.30 eV) and improved photo-induced charge separation. Moreover, the excellent stability towards RhB degradation (100%) after 4 recycles exhibits the great potential applicability. RhB removal efficiency could reach to 100% even in the wide pH range from 3 to 11. Furthermore, the synergy effect by outside oxygen-vacancies layer and interstitial carbon doping enhanced the photoelectrochemical (PEC) performances significantly. This PICD technology can induce carbon doping and defect layer with active cites, which opens up a new way to design novel visible-light-responsive photocatalysis.
查看更多>>摘要：In order to overcome the defects of the layered double hydroxide (LDH) with poor electrical conductivity and the limited active sites, in this paper, an advanced three-dimensional (3D) NiFe-LDH/rGO@NF composite material was designed and prepared by reducing graphene oxide (rGO) flakes on nickel foam (NF) and growing NiFe-LDH nanosheets in-situ. Excitingly, the 3D NiFe-LDH/rGO@NF composites exhibited excellent electrocatalytic performance. By analyzing the microstructure and electrochemical properties of NiFe-LDH/rGO@NF, the synergistic effect of 3D-NF and 2D-rGO on oxygen evolution reaction (OER) and electrocatalysis performance in 3D NiFe-LDH/rGO@NF was explored. The results show that the composite structure composed of 2D rGO and 3D NF is synergistic with each other. On the one hand, this composite structure can very effectively increase the specific surface area to inhibit agglomeration and expose abundant active sites of LDH. On the other hand, both rGO and NF can enhance the electrical conductivity of NiFe-LDH and improve the transportability of electrons and ions due to the excellent electrical conductivity. Additionally, the 3D NiFe-LDH/rGO@NF exhibits excellent OER catalytic performance, with an overpotential of 277 mV at 50 mA/cm2 and a Tafel slope of 59.9 mV/dec.
查看更多>>摘要：Multi-shell polyhedral clusters appear as building blocks in the crystal structures of quasicrystals and cage compounds. The multi-shell clusters in these materials are expected to provide characteristic features in the thermal, electronic, and magnetic properties, which still remain to be clarified. To shed light on this issue, we studied the electrical transport, heat capacity, and magnetic properties of Pt0.19Cd0.81 single crystals. Specific heat measurements and ab initio calculations of phonon modes revealed that the optical modes consist of extremely low-energy T2 triplet branches at as low as ~30 K and a highly dense continuum above ~50 K. The latter can account for a crossover behavior in the temperature dependence of the electrical resistivity. In the magnetic susceptibility, an anomalously large diamagnetic contribution attributable to the electrons’ orbital motion was observed. Possible origins, including the flow of ring currents in the multi-shell clusters and interband effects near possible Dirac points, are discussed.
查看更多>>摘要：There is a keen interest in developing discontinuously reinforced titanium matrix composites (DRTMCs) as lightweight structural materials for aerospace and automotive industries. However, a long-standing problem for these materials is the conflict between strength and ductility. To address this challenge, a novel Ti-Mo-Si composite with network microstructure is successfully fabricated by spark plasma sintering and hot rolled in the β region (900 °C) with different statin rate. We find that a thickness reduction of 20% is optimal for improving the strengthening efficiency and corresponding ductility. However, with the reduction of thickness in the hot rolling process, the strength increases while the ductility decreases, which is mainly because of the spheriodiation of α-Ti and reinforcements, as well as the strengthening of the interface between reinforcement and matrix. In addition, the composite after hot rolling follows fractured reinforcement and dimple mechanisms at small thickness reduction, while it obeys a quasi-cleavage fracture mechanism with significant thickness reduction.
查看更多>>摘要：Separation of Fe-containing intermetallics is an effective method to decrease Fe content in Al-Si alloys. The three-dimensional (3D) morphology and stability of Fe-containing intermetallics are important parameters affecting their separation efficiency. Combined with experiments and first-principles calculations, the variation of 3D morphology, stability, electronic structure and mechanical properties of α-AlFeMnSi are studied with the evolution of Fe/Mn atomic ratio. The experimental results show that the 3D morphology of α-AlFeMnSi transforms from Chinese character to regular polyhedron with the increment of Mn/Fe atomic ratio and all α-AlFeMnSi phases have cubic crystal structure. The calculated mixing enthalpies indicate that all α-AlFeMnSi phases are stable in thermodynamics due to the negative values. The electronic structure and Mulliken population calculations show that the variation of Mn/Fe ratio results in the overall change of chemical bondings of Si-Mn, Si-Fe, Al-Mn and Al-Fe, which leading to the evolution of stability and mechanical properties of α-AlFeMnSi phases. The calculated results of mechanical properties demonstrate that the Young's modulus and hardness of α-AlFeMnSi phases are improved with the increment of Mn/Fe atomic ratio, which is also validated by nano-indentation measurements. These results provide the componential guidance about designing easy-separable Fe-containing intermetallics and try to explain physical mechanism of property evolution of α-AlFeMnSi phase.
查看更多>>摘要：The stable structure of symmetrically Sc/Y-substituted hexahydride Sc0.5Y0.5H6 under high pressures is theoretically reported herein to superconduct with maximum Tc of 127 K, as supported by analyses of the electronic band structure, Fermi surface topologies, phonon dispersion, and the Eliashberg spectral function. We also expatiate on an alternative approach in describing the nature of Tc under pressures, i.e. the bandwidth function as an approximation of the spectral function (α2F) for Sc0.5Y0.5H6. Being a special case, the bandwidth function is derived from an analytic solution for the α2F function given constraints arising from the characteristics of the function itself. The consistency between the DFT-obtained α2F function and that of the proposed model suggests the dominant role played by the cutoff frequency for the optical modes in affecting Tc.
查看更多>>摘要：As a kind of bulk solid waste in iron and steel industry, titanium-bearing blast furnace slag (Ti-BFS) poses a serious threat to the environment, its disposal and reuse has been a hot and difficult spot. In this study, a new and high efficient hydrotalcite-like photocatalytic material (denoted CeTL) was prepared from Ti-BFS, and applied to the visible light catalytic degradation of antibiotics in water environment. The results showed that the degradation rate of tetracycline (TC) by the optimized CeTL reached 92.8% after 90 min of illumination. Dissolved organic matter with molecular weight 1–3 kDa was the most inhibiting to degradation rate. The introduction of Ce contributed to the nanopore structure and increased the specific surface area (302.58 m2/g), and effectively promoted the development of active surface oxygen and oxygen vacancies in the lattice, thus reducing the excited energy of photoelectron and expanding the spectral response range. Moreover, Ce acted as a medium to transfer photoelectrons, which successfully separates the reducing photoelectron in conduction band (CB) and the oxidized hole in valence band (VB), and generated·O2? and·OH with O2 and OH?, respectively. These active species attacked TC molecules adsorbed on CeTL surface, degraded them into small molecules, and improved the antibacterial activity of CeTL. The good adsorption capacity and the enhanced visible light catalysis of CeTL synergistic realized the efficient removal of TC. This work enriched the research system of comprehensive utilization of Ti-BFS, and provided a new strategy for the preparation of efficient applied photocatalysts and the recycling of resources.
查看更多>>摘要：In this study, TiC and B4C reinforced Inconel 718 (IN718) metal matrix composites (MMCs) have been fabricated using selective laser melting (SLM). The experiments were carried out with varying reinforcement contents (0–30%, in vol%) and laser scanning speeds (500–800 mm/s). A good interfacial bonding between TiC particles and IN718 matrix was observed at all the scanning speeds, whereas B4C/IN718 composites exhibited micro-cracks. Thermal modeling predicted the generation of much higher average von Mises stresses at the interfaces (avg.vmss). The defects in the composites and associated mechanisms were analyzed using a combination of scanning electron microscopy (SEM) and X-ray tomography (XRT). While decrease in the scanning speed decreased the extent of formation of fusion and balling defects, it was found to increase the keyhole porosity. Increasing the scanning speed and TiC content decreased and increased the micro-hardness of the composites, respectively. IN718–30 vol% TiC composite, fabricated using 500 mm/s, was found to exhibit the highest hardness of 619 ± 32.2 HV. The wear resistance first increased as the TiC content was increased to 20 vol%. Further increase in the TiC content to 30 vol% resulted in a decrease in the wear resistance due to higher degree of three-body abrasive wear.
查看更多>>摘要：Considerable efforts have been devoted to design effective anode material for metal-ion batteries. Heterostructures obtained by vertically stacking two-dimensional (2D) monolayers are being considered as alternatives. Here, a hybrid Van der Waals heterostructure with penta-graphene and penta-BN2 (PG/P-BN2) has been investigated for application as an anode material. First-principles calculations indicate that the PG/P-BN2 heterostructure is energetically and thermally stable. The electronic structures of the pristine and ionized heterostructures suggest their metallic properties, which presages good electrical conductivity for the anode material. The metal ions (Li and Na) are found to have low diffusion barriers and low average open-circuit voltages on the PG/P-BN2 heterostructure. The theoretical specific capacities of the PG/P-BN2 heterostructure for the both metal ions reach up to 1054.35 mA·h·g?1, being superior to those of the previously reported 2D anode materials. These results provide innovative advantages at the complex 2D heterostructures and will propel further development of efficient anode materials for superior alkali metal-ion batteries.
NSTL
Elsevier