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A Yolk-Shell-Structured FePO 4 Cathode for High-Rate and Long-Cycling Sodium-Ion Batteries
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Activating Single‐Atom Ni Site via First‐Shell Si Modulation Boosts Oxygen Reduction Reaction
Abstract Atomically dispersed nitrogen‐coordinated 3d transition‐metal site on carbon support (M‐NC) are promising alternatives to Pt group metal‐based catalysts toward oxygen reduction reaction (ORR). However, despite the excellent activities of most of M‐NC catalysts, such as Fe‐NC, Co‐NC et al., their durability is far from satisfactory due to Fenton reaction. Herein, this work reports a novel Si‐doped Ni‐NC catalyst (Ni‐SiNC) that possesses high activity and excellent stability. X‐ray absorption fine structure and aberration‐corrected transmission electron microscopy uncover that the single‐atom Ni site is coordinated with one Si atom and three N atoms, constructing Ni‐Si 1 N 3 moiety. The Ni‐SiNC catalyst exhibits a half‐wave potential (E 1/2 ) of 0.866 V versus RHE, with a distinguished long‐term durability in alkaline media of only 10 mV negative shift in E 1/2 after 35 000 cycles, which is also validated in Zn‐air battery. Density functional theory calculations reveal that the Ni‐Si 1 N 3 moiety facilitates ORR kinetics through optimizing the adsorption of intermediates.
libwfa: Wavefunction analysis tools for excited and open‐shell electronic states
Abstract An open‐source software library for wavefunction analysis, libwfa, provides a comprehensive and flexible toolbox for post‐processing excited‐state calculations, featuring a hierarchy of interconnected visual and quantitative analysis methods. These tools afford compact graphical representations of various excited‐state processes, provide detailed insight into electronic structure, and are suitable for automated processing of large data sets. The analysis is based on reduced quantities, such as state and transition density matrices (DMs), and allows one to distill simple molecular orbital pictures of physical phenomena from intricate correlated wavefunctions. The implemented descriptors provide a rigorous link between many‐body wavefunctions and intuitive physical and chemical models, for example, exciton binding, double excitations, orbital relaxation, and polyradical character. A broad range of quantum‐chemical methods is interfaced with libwfa via a uniform interface layer in the form of DMs. This contribution reviews the structure of libwfa and highlights its capabilities by several representative use cases. This article is categorized under: Software > Quantum Chemistry Theoretical and Physical Chemistry > Spectroscopy
Measurements of L-shell X-ray emission lines of neonlike europium on an electron beam ion trap
We report a measurement of the two X–ray transitions that proceed from the (1 s 2 2 s 2 2 p 5 1/2 3 d 3/2 ) J = 1 and (1 s 2 2 s 1/2 2 p 6 3 p 1/2 ) J = 1 upper levels to the (1 s 2 2 s 2 2 p 6 ) J = 0 ground level in neonlike Eu 53+ ( Z = 63), that is, near the previously documented avoided crossing of the two upper levels at Z = 68. The measurement was carried out using the calorimeter spectrometer on the Livermore EBIT–I electron beam ion trap. Here, it affirms the trends set by the neighboring neonlike ions both in terms of the relative intensity of the two lines and in terms of the magnitude of disagreement with theoretical energy level predictions.
All-order celestial OPE from on-shell recursion
We determine tree level, all-order celestial operator product expansions (OPEs) of gluons and gravitons in the maximally helicity violating (MHV) sector. We start by obtaining the all-order collinear expansions of MHV amplitudes using the inverse soft recursion relations that they satisfy. These collinear expansions are recast as celestial OPE expansions in bases of momentum as well as boost eigenstates. This shows that inverse soft recursion for MHV amplitudes is dual to OPE recursion in celestial conformal field theory.
The Magnetic Properties of the Spin-1 Ising Fullerene Cage with a Core-Shell Structure
Magnetic properties of Ising-type endohedral fullerene (IEF), which are formed by an atom encapsulated inside a diluted magnetic spherical cage, have been investigated theoretically as a function of its system parameters, and magnetism calculations by using effective field theory (EFT) were performed. Theoretical studies have been carried out to understand the effect on magnetic behaviors by the diluted magnetic surface, crystal field, and exchange couplings. The results display the first second-order phase transitions and tricritical point. The reentrant phenomena have been observed within a certain parameter range.
Influence of Melt-Pouring Temperature and Composition of Primary Coating of Shell Mold on Tensile Strength and Creep Resistance of Ni-Based Superalloy
Eight investment castings of Inconel 713C superalloy were fabricated, varying in the melt-pouring temperature, from 1400 to 1520 °C, and CoAl{sub 2}O{sub 4} inoculant content, 0 or 5 wt.%, in the primary coat. Their influence on grain size on tensile and creep properties was investigated. The best combination of yield stress (815 MPa) and elongation (A{sub 4} = 7.65%) at ambient temperature was obtained in surface-modified castings poured from 1520 °C. The longest time to rupture was for the unmodified castings (76.8 h) poured from 1520 °C, while for the modified variant, the time to rupture was lower around, 7.4 h, which was still a satisfactory value. During tensile testing, microcracks were formed in large eutectic γ′, carbides and borides, due to the accumulation of stress at interfaces with the matrix. During creep, N-type rafting of γ′ precipitates and phase transformation MC + γ → γ′ + M{sub 23}C{sub 6} took place.
The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Castings
In the investment casting process, the building of ceramic layers around the wax pattern is the main time-consuming stage. Increasing their number ensures sufficient mechanical properties, but also lengthens the whole process, including drying time and preheating of the mold. Four molds for casting Ni-based superalloy IN713C were strengthened by glass fibers, included in the slurry, and metal powder, of Al, Cu, Fe or Ni, in the coverage. Castings were subjected to microstructural investigations in order to find out if the new design can be promising for the manufacture of jet engine components. Bend tests revealed that the green strengths of all new molds were higher, at least 3.65 MPa, than that of the unmodified molds, 3.0 MPa. Optical microscopy revealed that the composition of a mold had a strong influence on stereological parameters of equiaxed IN713C grains. Microstructural observation and hardness measurements of castings revealed differences in the volume fraction of strengthening phases, porosity and hardness. The microstructure due to the complex chemical composition of IN713C consisted of several phases including ternary eutectics as a consequence of L → γ + Ni{sub 7}Zr{sub 2} + (Nb, Zr)C.
Magnetic Behavior of Ni/NiO Core–Shell Nanoparticles under Electromagnetic Waves for Oil–Water Interfacial Tension Reduction
The increasing demand for oil and gas has led to a hope of developing more efficient recovery methods. It is well known that nanoparticles adsorbed at the oil–water interface, but there is no consensus that has been reached on whether magnetic nanoparticles under electromagnetic waves affect the interfacial tension. In this paper, nickel/nickel oxide nanoparticles have been synthesized using sol–gel auto combustion method. The product was characterized using x-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, Fourier transforms infrared spectroscopy and vibrating sample magnetometer. The results show the Ni/NiO phases and the ferromagnetic nature of the sample. The Ni/NiO nanofluids were prepared to investigate the effect on oil–water interfacial tension in enhanced oil recovery under electromagnetic waves using an inverted pendant drop method. The results show a significant decrease in interfacial tension under electromagnetic waves of frequency 2.2 kHz at low wt.% of Ni/NiO and at room temperature. The decrease in the interfacial tension has been observed by increasing the temperature to 90 °C using temperature controller. The decrease in the interfacial tension could be due to the interaction of oscillating B-field of waves and magnetic domains of adsorbing nanoparticles at the oil–water interface which disturbed the oil–water interface.
Effects of local thinning defects and stepped thickness for free vibration of cylindrical shells using a symplectic exact solution approach
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Core–shell carbon fiber@Co1.5Mn1.5O4 mesoporous spinel electrode for high performance symmetrical supercapacitors
Not Available