The microstructure evolution and fracture behavior of Mg-2.7Al-0.8Zn (AZ31B) reinforced with 1 vol% nano silicon-carbide particle (NN-SiCp) and 4 vol% submicron SiCp (SuM-SiCp) during room ...temperature tensile test were investigated. The tensile failure mechanism of composite in the strain range of 0.8–2.4% were determined using the dislocation studies and microcrack analysis. The addition of double sized SiCp resulted in the extensive accumulation of dislocation near the interface between SiCp and matrix, and the dislocation density is increased as the increase of strain. The formation of high density dislocation zone was identified as one of the main causes of strength enhancement. Some microcracks can be found in the interface between SuM-SiCp and matrix, which show that the high stress concentration exists in the SuM-SiCp/Mg interface due to the particle size and polygonal morphology. However, the bonding interfaces of NN-SiCp/Mg were still continuous, and no microcracks were present around NN-SiCp. As a result of non-deforming SuM-SiCp resisting the crack-propagation, an appreciable crack blunting effect is generated, which contributes to the overall strengthening effect of double sized SiCp/Mg composite.
•The deformation/fracture behavior of the magnesium (Mg) matrix composites with nano- and submicron SiCp was investigated.•Interaction between double sized particles and dislocations under tensile deformation was determined.•Strengthening mechanisms of double sized SiCp on tensile properties of composite were determined.
Monolayer oxygen-containing yttrium hydride (YHx:O) and tungsten oxide (WO3) films show photochromic properties and have many potential energy-saving applications. YHx:O/WO3 composite films have ...better solar energy regulation properties than their monolayers because of the photochromic synergistic effects between the YHx:O and WO3 thin films. However, the reversion of these films to their initial transparent state is slow at room temperature, which limits their use in energy-saving windows. In this work, we developed a photo-thermochromic optical switching method that reversibly changes YHx:O/WO3 films between their transparent and infrared (IR) absorption states smoothly. The YHx:O/WO3 composite films were prepared by DC magnetron sputtering, and the reversible optical switching properties and photochromic mechanism were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The composite films changed from their transparent state to their absorption state under illumination within 10 min, and returned to their transparent state when they were heated at 60–100 °C for 5 min. Compared with the single-layer YHx:O film, the YHx:O/WO3 composite films had a high color change rate and high solar transmittance (ΔTsol = 50.46%). We speculate that the mobile H in the YHx:O layer diffuses to the WO3 layer after illumination, converting WO3 to a tungsten bronze structure, increasing the IR absorption of the composite films. The diffusion of H in the YHx:O and WO3 layers was reversible and had good switching repeatability, and FTIR spectroscopy confirmed that H moved reversibly in films and played an important role in the photochromic process.
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•YHx:O/WO3/SiAlOx composite film was prepared by using magnetron sputtering methods.•Use photochromic and thermochromic methods to firstly realize reversible and steady switching of composite films.•Photo-response and optical modulation of YHx:O/WO3/SiAlOx composite film were improved compare to YHx:O single film.•The reversible diffusion of hydrogen was confirmed during the switching process under illumination.
•The influence of solute elements and chlorine adsorption on the anodic behavior of Mg (0001) surface is investigated based on work function change and local electrode potential shift.•Li, Al, Mn, ...Zn, Fe, Ni, Cu, Y, and Zr are considered as solute atoms in this work.•Cl adsorbate will destabilize Mg atoms on the surface by weakening the metal bonds.•Strong hybridization between Mg and solute atom orbitals will raise the local electrode potential.
Solute atoms and Cl adsorbate at Mg(0001) surface may change the work function and local electrode potential and further influence the anodic behavior of Mg matrix. Display omitted
The influences of solute atoms (Li, Al, Mn, Zn, Fe, Ni, Cu, Y, Zr) and Cl adsorption on the anodic corrosion performance on Mg (0001) surface have been investigated based on first-principles calculations, which might be useful for the design of corrosion-resistant Mg alloys. Work function and local electrode potential shift are chosen as descriptors since they quantify the barrier for charge transfer and anodic stability. We found that at 25% surface doping rate, Y decreased the work function of Mg, while the impact of remaining doping elements on the work function of Mg was trivial due to the small surface dipole moment change. The adsorption of Cl destabilized the Mg atoms at surface by weakening the bonding between surface Mg atoms. We find that a stronger hybridization of d orbits of alloying elements (e.g. Zr) with the orbits of Mg can greatly increase the local electrode potential,which even overbalances the negative effect introduced by Cl adsorbates and hence improves the corrosion resistance of Mg alloys.
Magnesium (Mg)-air battery, which is an important category of metal-air batteries, has been considered as the promising energy storage in various areas as a primary battery. However, low utilization ...efficiency due to the serious hydrogen evolution of the Mg anode impairs its discharge performance. Herein, we successfully achieve a high-energy-capacity Mg-air battery that reaches record-breaking 2134 ± 88 mAh g−1 and 2279 ± 55 mAh g−1 with magnetron-sputtered Mg50Al50 and Mg30Al70 anodes in a traditional NaCl electrolyte. The superior high capacity of this new battery can be attributed to the suppression of hydrogen evolution without inhibiting the discharge process of the anode.
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•Mg50Al50 and Mg30Al70 alloy anodes were magnetron-sputtered for a Mg-air battery.•The primary batteries with the anodes had record-breaking high specific capacity.•The passive films of the anodes effectively inhibited anodic hydrogen evolution.•The supersaturated Al in the anodes improved the capacity and reduced the activity.
The refined theory and the decomposed theorem of plates are converted into the refined theory and decomposed theorem of the axisymmetric circular cylinder. The refined theory provides the solutions ...of the axisymmetric circular cylinder without ad hoc assumptions. Expressions are obtained for all the displacements and stress components in terms of the axis displacement, and its derivatives by using Bessel’s Function and axisymmetric general solutions. On the basis of the refined theory developed in the present paper, solutions are obtained for a circular cylinder with homogeneous and non-homogenous boundary conditions, respectively. For the circular cylinder with homogeneous boundary conditions, the refined theory provides exact solutions that satisfy all of the governing equations. The exact solutions can be decomposed into two parts: the 2-orders equation and the transcendental equation. In the case of non-homogenous boundary conditions, the approximate governing equations are accurate up to the 2-order terms with respect to the radius of the circular cylinder.
Graphitic carbon nitride (g-C
N
) fundamental photophysical processes exhibit a high frequency of charge trapping due to physicochemical defects. In this study, a copper phosphide (Cu
P) and g-C
N
...hybrid was synthesized via a facile phosphorization method. Cu
P, as an electron acceptor, efficiently captures the photogenerated electrons and drastically improved the charge separation rate to cause a significantly enhanced photocatalytic performance. Moreover, the robust and intimate chemical interactions between Cu
P and g-C
N
offers a rectified charge-transfer channel that can lead to a higher H
evolution rate (HRE, 277.2 μmol h
g
) for this hybrid that is up to 370 times greater than that achieved from using bare g-C
N
(HRE, 0.75 μmol h
g
) with a quantum efficiency of 3.74% under visible light irradiation (λ = 420 nm). To better determine the photophysical characteristics of the Cu
P-induced charge antitrapping behavior, ultrafast time-resolved spectroscopy measurements were used to investigate the charge carriers' dynamics from femtosecond to nanosecond time domains. The experimental results clearly revealed that Cu
P can effectively enhance charge transfer and suppress photoelectron-hole recombination.
In this work, we investigate the problem of multisatellite resource allocation for expected long-term performance optimization with a dynamic task network model, where communication tasks generated ...by task satellites are expected to be transmitted by resource satellites in the application layer, and the set of tasks changes with satellite orbital motions. The features of the tasks include priority, execution duration, visible time, etc. Since the feature information has a high dimension and changes with time, the scheduling problem is formulated as a dynamic combinatorial optimization problem and a receding-horizon task scheduling algorithm based on the event-triggered deep reinforcement learning is proposed. A residual-fully connected network is designed to extract the features of the complex task network model, and a deep double Q-learning iteration with the experience replay memory mechanism is employed to change the allocation strategy by evaluated rewards adaptively. An event-triggered strategy is then proposed to handle urgent tasks online. Numerical simulations show the performance improvement of the proposed algorithm. For the scenario of 50 task satellites and ten resource satellites, the proposed algorithm achieves 4.1%, 5.9%, and 11.4% higher reward scores than the static deep reinforcement learning algorithm, the data-driven parallel scheduling algorithm, and the improved genetic algorithm, respectively. The computation time of the proposed algorithm is only 34.7% and 21.3% of that of the latter two algorithms, and is similar to that of the static deep reinforcement learning algorithm.
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•N,S-CS/CN achieved the high H2O2 activity in acid, neutral and alkaline conditions.•The carbon-based heterostructures could effectively avoid the charge recombination.•The ...synergistic effect of S- and N-site was conducive to H2O2 production.
Photoelectrocatalytic (PEC) H2O2 synthesis from water and oxygen is a prospective approach for the manufacture of solar fuels and value-added versatile chemicals. However, the development of the efficient photocathode remains a formidable challenge because of the inferior selectivity and yield of H2O2 derived from the multiple electron transfers affected by pH conditions. Herein, we report a metal-free carbon-based heterostructure material with N, S co-doping, where binary heteroatom-doped carbon sphere (N,S-CS) is loaded on carbon nitride (C3N4) polymer, achieving an efficient synthesis of H2O2 in a wide pH range. DFT calculations and experimental results uncover that S- and N-site can suppress the O-O cleavage and facilitate the *OOH formation through their subtle microenvironment, mediating the superior 2e- oxygen reduction selectivity to H2O2 in acids and alkalis, respectively. This work provides a cost-effective strategy for designing an efficient photocathode for H2O2 production in a wide pH environment.
The serious safety issues caused by uncontrollable lithium (Li) dendrite growth, especially at high current densities, seriously hamper the rapid charging of Li metal‐based batteries. Here, the ...construction of Al–Li alloy/LiCl‐based Li anode (ALA/Li anode) is reported by displacement and alloying reaction between an AlCl3‐ionic liquid and a Li foil. This layer not only has high ion‐conductivity and good electron resistivity but also much improved mechanical strength (776 MPa) as well as good flexibility compared to a common solid electrolyte interphase layer (585 MPa). The high mechanical strength of the Al–Li alloy interlayer effectively eliminates volume expansion and dendrite growth in Li metal batteries, so that the ALA/Li anode achieves superior cycling for 1600 h (2.0 mA cm−2) and 1000 cycles at an ultrahigh current density (20 mA cm−2) without dendrite formation in symmetric batteries. In lithium–sulfur batteries, the dense alloy layer prevents direct contact between polysulfides and Li metal, inhibiting the shuttle effect and electrolyte decomposition. Long cycling performance is achieved even at a high current density (4 C) and a low electrolyte/sulfur (6.0 µL mg−1). This easy fabrication process provides a strategy to realize reliable safety during the rapid charging of Li‐metal batteries.
The universal Al–Li alloy‐based layer is demonstrated to be highly effective for stabilizing the lithium metal anode at an ultrahigh current density. The high strength layer not only inhibits the growth of lithium dendrites but also prevents the parasitic reactions of Li with the liquid electrolyte and polysulfides.
The difference effect and hydrogen evolution behavior of pure Mg in alkaline NH
4
+
containing solutions are systematically investigated. The Mg electrode exhibits a positive difference effect, ...rather the traditional negative difference effect, with the anomalous hydrogen evolution in the alkaline 0.1 M (NH
4
)
2
SO
4
, 0.1 M NH
4
HCO
3
and 0.05 M (NH
4
)
2
CO
3
solutions. This is primarily attributed to the corrosion product film dissolution effect of NH
4
+
and the formation of the black corrosion products. The hydrogen evolution kinetics with the difference effects are deduced and explained by the prevailing incomplete film Mg
+
mechanism and enhanced catalytic activity mechanism.
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