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Electronic regulation of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is a crucial step towards next-generation optoelectronics and electronics. Here, we demonstrate controllable and selective-area defect engineering in 2D molybdenum disulfide (MoS2) using a focused ion beam with a low-energy gallium ion (Ga+) source. We find that the surface defects of MoS2 can be tuned by the precise control of ion energy and dose. Furthermore, the field-effect transistors based on the monolayer MoS2 show a significant threshold voltage modulation over 70 V after Ga+ irradiation. First-principles calculations reveal that the Ga impurities in the monolayer MoS2 introduce a defect state near the Fermi level, leading to a shallow acceptor level of 0.25 eV above the valence band maximum. This defect engineering strategy enables direct writing of complex pattern at the atomic length scale in a controlled and facile manner, tailoring the electronic properties of 2D TMDCs for novel devices.

The magneto-electro-elastic coupling static problem for a functionally graded piezoelectric-piezomagnetic (FGPEPM) cylinder/spherical shell is studied for various axial/spherical symmetric loads. On the basis of unified basic equations with geometric parameters and the material assumption of exponential inhomogeneous properties, the analytical solutions for the physical quantities of displacement, stress, electric potential, and magnetic potential of the FGPEPM hollow cylinder/spherical shell are obtained. In the numerical discussions, the static response of the FGPEPM cylinder/spherical shell is numerically solved under mechanical load on the inner surface or given an electric/magnetic potential difference between the inner and outer surfaces when the material on the inner surface is assumed to be BaTiO3-CoFeO4. The distribution of radial and circumferential stress and the electric and magnetic potentials under different functionally graded (FG) parameters are presented. The influence of FG parameters on the positive (converse) piezoelectric, positive (converse) piezomagnetic, and positive (converse) magnetoelectric potentials is discussed in detail.

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode is considered to be among the most promising candidates for high-energy-density lithium-ion batteries (LIBs). However, both capacity fading and structural degradation occur during long-term cycling, which extremely limit the commercial applications of NCM811, especially at a high cutoff voltage (>4.3 V). Here, we design a double-shell hybrid nanostructure consisting of a Li2SiO3 coating layer and a cation-mixed layer (Fm3m phase) to improve its electrochemical performance. Consequently, the Si-modified NCM811 electrode shows outstanding cycling stability with a 95.2% capacity retention at 4.3 V after 100 cycles and 87.3% at a 4.5 V high cutoff voltage after 100 cycles. This designed double-shell hybrid nanostructure alleviates side reactions, structural degradation, and internal cracking, effectively enhancing the surface structural stability. This efficient strategy provides a valuable step toward further commercial applications of the LiNi0.8Co0.1Mn0.1O2 cathode and enriches the fundamental understanding of layered cathode materials.

The most abundant rare earth metals in the Earth's crust have received considerable recent attention as efficient electrocatalysts for full water splitting, but it is highly desired to explore a new strategy to improve their catalytic activity. In this communication, we report the development of nanoporous CeO2 nanowire array on Ti mesh (np-CeO2/TM) derived from MnO2–CeO2/TM via an acid etching strategy, and MnO2 acts as a pore-forming agent through selective etching with oxalic acid. As a rare earth metal catalyst, np-CeO2/TM needs an overpotential of 91 mV for the hydrogen evolution reaction (HER) and 279 mV for the oxygen evolution reaction (OER) to drive a current density of 10 mV cm−2 in 1.0 M KOH, 93 mV and 101 mV less than that needed by MnO2–CeO2/TM, respectively. We also demonstrate the use of np-CeO2/TM to make a two-electrode electrolyzer capable of driving 10 mV cm−2 at a cell voltage of 1.57 V.

Currently, there is an urgent demand for Ni-rich cathode materials with excellent electrochemical properties under harsh conditions; however, obtaining such materials is very challenging. Here, we propose an innovative modification strategy that combines gradient phosphate polyanion doping and dual-conductive layer (Li3PO4-PANI) coating. The phosphate polyanion gradient doping can be described as acting in a “support role” to optimize the crystal structure. Moreover, the dual-conductive (Li3PO4-PANI) layers can be described as acting in a “palisade role” to inhibit side reactions and enhance the ionic/electronic conductivity of the NCM cathode. For the NCM cathode, this strategy synergistically achieves three main objectives: enhancement of structure stability, improvement of the ionic/electronic conductivity of the interface, and reduction of residual lithium salts. The modified NCM cathode delivers superior cycling stability, with 81.4% capacity retention after 100 cycles (4.5 V/55 °C), whereas the orig...

In this paper an improved mathematical model of a hydro-pneumatic tensioner (HPT) system for top tensioned riser (TTR) is derived by consideration of friction, mass of piston and piston rod, tension loss in hydraulic oil piping, and compressibility of hydraulic oil. The vertical motion of the riser string is also considered. Subsequently, the proposed detailed model and the conventional simplified model are comparatively studied. Finally, the tension characteristic and performance parameters of the HPT are analyzed based on the proposed model. Results show that the conventional simplified model indeed overestimates the tension of tensioner as it neglects some performance parameters resulting in tension loss. The diameters of piston and piston rod and the initial pressure of high pressure (HP) gas have the most significant influence on the tension of the tensioner. The initial volume of HP gas and the initial pressure of low pressure (LP) gas also have some impact. The influence of the initial volume of LP gas and the inner diameter and length of the piping is relatively small. The research has some reference value for HPT and TTR design.

LiNi0.8Co0.15Al0.05O2 (NCA), a promising ternary cathode material of lithium-ion batteries, has widely attracted attention due to its high energy density and excellent cycling performance. However, the presence of residual alkali (LiOH and Li2CO3) on the surface will accelerate its reaction with HF from LiPF6, resulting in structural degradation and reduced safety. In this work, we develop a new coating material, LiH2PO4, which can effectively optimize the residual alkali on the surface of NCA to remove H2O and CO2 and form a coating layer with excellent ion conductivity. Under this strategy, the coated sample NCA@0.02Li3PO4 (P2-NCA) provides a capacity of 147.8 mAh g−1 at a high rate of 5 C, which is higher than the original sample (126.5 mAh g−1). Impressively, the cycling stabilities of P2-NCA under 0.5 C significantly improved from 85.2% and 81.9% of pristine-NCA cathode to 96.1% and 90.5% at 25 °C and 55 °C, respectively. These satisfied findings indicate that this surface modification method provides a feasible strategy toward improving the performance and applicability of nickel-rich cathode materials.

Magnetic dipole theory has been widely and successfully used to explain the leakage magnetic field signals. Because the model parameter such as magnetic dipole density is not easy to quantify, magnetic dipole theory often needs normalizing in application, which is considered to be unsuitable for quantitatively analyzing the magnetic memory signals with the stress effect. In this paper, the theoretical model of magneto-mechanical coupling magnetic dipole is established, which is suitable for analyzing the stress effect on magnetic signals in magnetic memory testing method. Based on the ferromagnetic theory, the equivalent field under the combined action of the applied load and the magnetic field is determined. And then, the magneto-mechanical analytical model is obtained for the isotropic ferromagnetic material under the weak magnetic field based on the first-order magnetization approximation in the weak magnetization state. Under the assumptions of rectangular and V-shaped magnetic charge distribution for the two-dimensional magnetic signal problem, the theoretical analytical models of the magnetic memory signals from the smooth and cracked specimens, and the analytical models of the magnetic memory signal induced by the rectangular and V-shaped surface defect are established. Based on the analytical solution of the proposed magneto-mechanical magnetic dipole theory, the difference in signal between before and after the failure of the specimen, the signal from the rectangular and V-shaped defect, and other influencing factors and laws of the magnetic signal are analyzed in detail. In particular, the influence of stress, environmental magnetic field, defect morphology and size, lift-off effect, specimen size and other factors on magnetic memory signals can be described based on the analytical solution of magneto-mechanical magnetic dipole models proposed in this paper. The proposed analytical model of magneto-mechanical magnetic dipole in this paper is simple and easy to use, and the present research shows that the proposed analytical solution in this paper can explain some basic experimental phenomena and laws in magnetic memory testing experiments. In addition, the precise magneto-mechanical coupling quantitative model combined with the finite element analysis method is still needed for accurately analyzing the magnetic memory signals in experiment.

The presented work studied the structural response of the hydraulic pneumatic tensioner (HPT) in a TLP-TTR system with failure of the tensioner cylinder. A fully coupled hull-tendon-TTR-tensioner model was established in AQWA to simulate the failure numerically. A specific HPT was modeled by considering 4 cylinders and the real-time stroke of each piston. A set of formulas was proposed to calculate the real-time tension including different components, e.g. Stribeck friction, in the tensioner. A riser array including 6 independent production TTRs and their tensioners was also modeled. The production TTR model was stacked up by different specific riser joints. The hydrodynamic force acting on the hull was obtained by using the 3D potential flow theory. The real-time tensions on different tensioner cylinders were obtained by using an in-house-developed program. Different environmental conditions, including a calm sea, regular waves, and extreme sea states, were considered in the simulations. In the results, the behaviors of different cylinders of the failed tensioner were presented. The results show that when an accidental local failure of the HPT occurs, the tension and stroke responses are still far from the designed-limits to induce a progressive failure.

In order to improve the efficiency of centrifugal pump, based on the bionics principle, established non-smooth surfaces of various groove structure on the centrifugal pump impeller. The internal flow field of it was numerically simulated through RNG k-ε turbulence model. Research the drag reduction characteristics of non-smooth impeller in different groove shape and arrangement. The results showed that the biggest drag reduction rate of centrifugal pump with non-smooth blades is about 6.22%. The blades of non-smooth unit can effectively inhibit the near wall boundary layer flow state, reduce the shear stress on blades wall, reduce the internal fluid turbulent degree of centrifugal pump, so that the fluid flow in centrifugal pump impeller is more stable, improve the efficiency of centrifugal pump.

Achieving a highly stabilized surface structure is the key to successfully enhancing the cycling stability of LiNi0.8Co0.1Mn0.1O2 (NCM) cathode material for Li-ion batteries at high cut-off voltage (4.5 V). In this work, we report a highly surface-stabilized NCM material via a high-valent titanium ion (Ti4+)-induced nanostructured hybrid surface with a core-shell structure. Consequently, the Ti-modified LiNi0.8Co0.1Mn0.1O2 cathode provides an excellent cycling stability with 92.3% capacity retention (100 cycles, 0.5C, 2.7–4.5 V). This proposed hybrid core-shell nanostructure prominently mitigates the surface structural degradations, continuous microcracking and parasitic reactions, effectively improving the surface structural stability. This efficient strategy provides a step towards further commercial application of the LiNi0.8Co0.1Mn0.1O2 material and can be extended to other layered cathode materials.

In order to design a single mode 980 nm vertical cavity surface emitting laser (VCSEL), a 2 μm output aperture is designed to guarantee the single mode output. The effects of different mesa sizes on the lattice temperature, the output power and the voltage are simulated under the condition of continuous working at room temperature, to obtain the optimum process parameters of mesa. It is obtained by results of the crosslight simulation software that the sizes of mesa radius are between 9.5 to 12.5 μm, which cannot only obtain the maximum output power, but also improve the heat dissipation of the device.

Phase constitution and microstructure of the Mg-5Sn-xSi-2Sr (x=0, 1, 2) alloys were analyzed by X-ray diffractometer, optical microscope and scanning electron microscope with an energy dispersive spectrometer. The tensile properties of the alloys were tested by electronic universal testing machine, and the fracture surfaces of the alloys were observed with scanning electron microscope. The results show that the microstructure of the Mg-5Sn-2Sr alloy consists of α-Mg, MgSnSr and Mg2Sn phases. The addition of Si element can promote the formation of Mg2Si phase on the grain boundary, and the content of Mg2Si phase increases with increasing the Si element. Mg2Si is a strengthening phase, which can effectively prevent grain boundary sliding and dislocation motion, and thus, the mechanical properties of the alloys were obviously enhanced. The mechanical properties of Mg-5Sn-2Si-2Sr alloy are better than other alloys, the tensile strength, yield strength, elongation and hardness are 147MPa, 110MPa, 5.0% and 47HB respectively.

An effective synthetic strategy is demonstrated for preparing highly ordered crystallized mesoporous TiO(2) by introducing rare earth in the synthesis process; the obtained product exhibits near-infrared photocatalytic activity.

SnO(2) nanorods with specific growth directions, [101] or [001], were fabricated on α-Fe(2)O(3) substrates via a simple hydrothermal method. The growth behavior of SnO(2) nanorods is facet-selective. Both {11 ̅20} and {10 ̅10} facets of α-Fe(2)O(3) are favorable to direct the growth of SnO(2) nanorods. The correlation between the crystallographic orientation of SnO(2) and the facets of α-Fe(2)O(3) is characterized by TEM observations and investigated on the basis of the interfacial lattice compatibility. Furthermore, the distribution and coordination of oxygen atoms at the interface of α-Fe(2)O(3)-SnO(2) heterostructure are analyzed, which reveals that only slight deviations from their original equilibrium positions are allowed for the formation of heterogeneous interface. And this lower energy activated interfacial construction is beneficial to the feasibility and stability of heterostructures.

This article reports a facile and controllable two-step method to construct TiO2–Pt@SiO2 nanocomposites. TiO2 nanoparticles (NPs), with small size and high surface energy, were synthesized by a solvothermal reaction process. The TiO2–Pt@SiO2 nanocomposites were fabricated by a reverse micro-emulsion method. SiO2 shell coated NPs were adopted for further photocatalytic reaction. Because of their small size and high surface energy, TiO2@SiO2 and TiO2–Pt@SiO2 nanocomposites show higher photocatalytic activity than commercial Degussa P25. Compared with TiO2@SiO2, TiO2–Pt@SiO2nanocomposites have improved photocatalytic activity due to the Pt induced spatial separation of electrons and holes. The silica shells not only maintain the structure of the nanocomposites but also prevent their aggregation during the photocatalytic reactions, which is highly important for the good durability of the photocatalyst. This strategy is simple, albeit efficient, and can be extended to the synthesis of other composites of noble metals. It has opened a new window for the construction of hetero-nanocomposites with high activity and durability, which would serve as excellent models in catalytic systems of both theoretical and practical interest.