查看更多>>摘要：Harnessing the precious metal plasmon effect is a powerful way to enhance the upconversion luminescence of rare-earth materials, so it has received extensive attention from researchers. In this study, a series of AMF@SiO2 @NaYbF4: Er3+ composite structures were constructed with an Au mono-layer film (AMF) as the substrates and SiO2 as the isolation layer to enhance the upconversion emission intensity of a single NaYbF4: 2%Er3+ microdisk. When the size of Au nanoparticles was 72 nm and the thickness of the SiO2 isolation layer was 24 nm, the upconversion emission enhancement factor of the single NaYbF4: 2%Er3+ microdisk reached 6.98 under 980 nm laser excitation, due mainly to the enhancement of the local electromagnetic field. The upconversion luminescence properties of a single NaYbF4: 2%Er3+ microdisk were significantly affected by the size of Au nanoparticles, the density of the AMF substrate, and the thickness of the SiO2 isolation layer. The plasmon-enhanced upconversion luminescence mechanism was studied according to its luminescence properties, dynamic tests, and theoretical simulation. The synergistic effects in the local electromagnetic field, luminescence quenching, and local surface plasmon resonance effect are also discussed. The results of this research provide an invaluable theoretical basis for enhancing the upconversion luminescence of rare-earth materials with the help of AMF substrates.
查看更多>>摘要：In this work, the fundamental processing-structure-property (PSP) relationships that govern laser-based additive manufacturing were investigated with the Ti-6Al-4V alloy. X-ray synchrotron imaging carried out in conjunction with in-situ integrating sphere radiometry enabled real-time energy absorption measurements for a range of melting conditions that varied laser power and velocity. A thermal conduction model that incorporated the in-situ absorption data and final melt pool geometry was used to predict the thermal histories and diffusion distances along the heat-affected zone (HAZ) in the Ti-6Al-4V alloy to provide insight into the solid-state phase transformations that occurred in the unmelted regions adjacent to the melt pool. Resulting microstructural features were quantified using scanning electron microscopy techniques to elucidate changes in solidification behavior. Significant changes to α/β-Ti phase fractions were measured in the unmelted HAZ, across all test cases. Nanoindentation and scanning probe microscopy revealed differences in the hardness, modulus, and Volta potential across the resolidified melt pool, HAZ, and wrought base material. These measurements and simulations can be used to predict how processing changes lead to differences in the as-built performance of titanium parts that are used in aerospace and biomedical applications. This work demonstrates the utility of coupling in-situ absorption data with a conduction-only high speed model, which leads reasonable agreement with the synchrotron imaging measurements and microstructural transformations observed herein.
查看更多>>摘要：The present study successfully synthesized NiCo2S4 nanotubes@NiMn-LDH nanosheets core-shell hybrid structure on Ni foam through a controllable three-step facile hydrothermal method, the NiMn-layered double hydroxides (LDHs) nanosheets with unlike thicknesses adhere to the outer layer of NiCo2S4 nanotubes by adjusting the heating time of hydrothermal reaction. The optimized NiCo2S4@NiMn-LDH electrode was able to transmit a high specific capacity of 822.64 C g?1 (4.36 C cm?2) at a high current density of 50 mA cm?2, and maintained 92.7% of its initial specific capacity after 5000 cycles at a current density of 50 mA cm?2 when 2 M KOH was used as the electrolyte. Furthermore, an asymmetric supercapacitor (ASC) device fabricated with NiCo2S4@NiMn-LDH as the positive electrode and activated carbon (AC) as the negative electrode, and it achieved a maximal energy density of 53.10 W h kg?1 at a power density of 370.82 W kg?1 also maintained 94.3% retention of the initial specific capacitance after 10,000 cycles at a high current density of 20 mA cm?2. With the excellent electrochemical properties, the as-prepared core-shell structured NiCo2S4@NiMn-LDH hybrid arrays have extraordinary application potential in the energy storage field.
查看更多>>摘要：Inclusive detection of organic compounds in aqueous solutions is a promising yet challenging approach for photoelectrochemical (PEC) sensors. In this work, the combined factors of crystalline phase change and Ti3+ self-doping were introduced to some fabricated anodic TiO2 nanotubes (ATNTs) to improve their efficacy as potential PEC sensors. Several TiO2 electrodes were effectively fabricated according to the variation of the factors as mentioned above via dual-step anodization process of a Ti foil, followed by high-temperature annealing under a hydrogen reduction atmosphere. As evidenced by XPS and wettability tests, oxygen vacancies were created in the crystalline lattice of TiO2 nanotubes as shallow donors’ levels which boosted the electronic conductivity of ATNTs. This enhancement in the electronic conductivity was endorsed and assessed by photoelectrochemical (PEC) properties performance testing. The PEC performance results indicated that bi-phased (anatase and rutile) Ti3+-ATNTs photo-electrode annealed at 600 °C under hydrogen reduction synergistically prompted the photoelectrochemical activity. In addition, their corresponding photocurrent was 2-fold greater than that of the other fabricated ATNTs photo-electrodes. Most prominently, the bi-phased Ti3+- ATNTs photo-electrode degraded more minor concentrations of organic solutions with a broader linear detection range. This recommends that the bi-phase Ti3+- ATNTs photo-electrode may serve as a robust sensor for the PEC identification of selective organic solutions under solar light irradiation. These designed PEC sensors have demonstrated their promising feasibility and selectivity for glucose, KHP, succinic acid, and malonic acid; hence this suggests their bright future in detecting biomedical samples for clinical diagnosis.
查看更多>>摘要：α phase evolution and tensile fracture behavior of Ti5Al2Sn2Zr4Mo4Cr alloy fabricated by directed energy deposition (DED) were studied. Samples with a different number of layers were fabricated by the same processing parameters. Microstructure evolution was analyzed based on the thermal history calculated through finite element analysis and isothermal transformation kinetics. The results suggested that the samples exhibit various α phase characteristics. Two kinds of starting microstructures at different layers, single β phase and mixed α/β phases can be obtained depending on the deposited layer's temperature and cooling rate. Further evolution of α phase is closely related to the consecutive thermal cycles with different durations and different temperature amplitudes. The in-situ scanning electron microscopy tensile tests were performed in the horizontal (perpendicular to the build direction) and vertical (parallel to the build direction) directions under the as-deposited and heat treatment conditions. The results showed that the cracks and micro-voids usually initiate on the grain boundaries or α/β interface. α phase characteristic plays an important role in deformation behavior. The sample containing fine α laths usually fractured quickly after the first surface crack was observed. The coarse α laths resulted in a larger crack tip plastic zone and delayed the crack propagation.
查看更多>>摘要：Vanadium pentoxide (V2O5) nanostructures were grown on the ITO-coated glass slides using differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry (CA) methods, and utilized as the hole transport layer (HTL) in the construction of bulk heterojunction polymer solar cells (BHJ PSCs). The influences of the deposition time in the mentioned methods were investigated to find the best conditions to achieve the highest electrochemical performance from the deposited layer. The morphology of the electrodeposited nanostructures differed by changing the applied potential regime, and V2O5 nanorods (NRDs) were formed by the CV while V2O5 nanoparticles (NPs) formed using DPV and chronoamperometry. Simple adjustment of the applied potential regime and deposition time led to considerable structural and electrochemical changes of the resulting V2O5. Features of the electrochemically-grown V2O5 were compared with each other and with those of the V2O5 prepared using the hydrothermal method. The best sample in each series was selected in terms of suitable surface conductivity, high optical transparency and appropriate energy levels and applied as HTL in BHJ PSCs. Results revealed that the V2O5 sample prepared using DPV provided considerably better electrical, optical and electrochemical features. PSCs prepared based on this sample exhibited a higher power conversion efficiency (PCE) (~ 48%) and fill factor (~2%) than PSCs prepared based on V2O5 synthesized by the hydrothermal method. This was attributed to the high electroactive surface area (0.26±0.003 cm2), high charge mobility (2.44 × 10-4 cm2. V-1s-1) and excellent conductivity (0.03 mS.cm-1) of V2O5 NPs grown using DPV. The best cell provided an open circuit voltage of about 0.56 V, a short circuit current of 9.42 mA cm2, a fill factor of 65.3% and a power conversion efficiency of 3.40%. PCE of this cell was about 60% higher than that considered for the reference device prepared base on the PEDOT:PSS HTL.
查看更多>>摘要：In this work, the Ni(Co)MoO4 (NMO-Co) hybrid materials with nanoneedle and nanosheet structure were prepared on nickel foam (NF) by the hydrothermal method for high-stability supercapacitors. The effect of Co presence on the structure and electrochemical properties of NMO-Co was investigated. As the molar of Cobalt increased, more nanoneedles grew on the surface of NiMoO4/NF. The combination of the Ni-doped CoMoO4 nanoneedles and Co-doped NiMoO4 nanosheets was irregularly arranged on the surface of NF, which emerged an improvement of the cycling performance. When the molar ratio of Co: Ni: Mo was 0.5: 1: 1, the capacitance retention of the hybrid electrode was 80.1% after 10,000 cycles at 10 A g?1, while the pure NiMoO4 electrode was 53.1%. Moreover, an asymmetric supercapacitor device displayed high energy density and power density. The maximum energy density and power density could reach 55.71 Wh kg?1 and 14,999 W kg?1, respectively. The hybrid electrode's good electrochemical performance is due to the combination of mutual doping of Ni and Co with a mixed morphology.
查看更多>>摘要：Unique structured electrodes with abundant surface area is imperative for developing high-performance supercapacitors. Herein, hollow hierarchical Ni3S2 @Co9S8 (NiS@CoS) nanotubes are rationally designed by a one-pot strategy, which demonstrate a substantial high active area. Accordingly, NiS@CoS nanotubes have exhibited promising electrochemical energy storage characteristics with high areal specific capacitance (9.79 F cm?2 at 2 mA cm?2) and excellent cycling stability (80.8% retention after 10000 at 20 mA cm?2). Furthermore, the hybrid supercapacitor (HSC) is designed with the NiS@CoS and active carbon (AC) as positive and negative electrodes, respectively. Remarkably, the HSC achieves ultrahigh energy density of 0.63 mWh cm?2 at a power density of 1.66 mW cm?2 (and 0.37 mWh cm?2 at 21.76 mW cm?2). This work offers a simple and effective approach to fabricate low-cost transition metal sulfides with great prospects in practical energy storage applications.
查看更多>>摘要：In this work, Polyquaternium-7 (M550) was utilized as the intermediate layer to strengthen the interface interaction between hexanitrohexaazaisowurtzitane (CL-20) and graphene oxide (GO), and then CL-20/M550-GO (CMG) was prepared through electrostatic self-assembly. The surface morphology and component of CMG were determined, which proved that CL-20 was covered with M550-GO. The thermal measurement showed that the coating of M550-GO can increase the transformation temperature of the crystal form of CL-20. The impact sensitivity and friction sensitivity of CMG was measured by the BAM method, and the results were 35 J and 288 N, respectively. To our best knowledge, this is the best desensitizing effect of CL-20. Meanwhile, the composite presented good compatibility with 3,3-Diazide methyl oxetane and tetrahydrofuran copolyester (PBT) and toluene diisocyanate (TDI), which indicates the potential application of this strategy in a cross-linked propellant system. Excluding the influence of the content and crystal form on the mechanical sensitivity, M550 was ensured to be responsible for the improved desensitizing effect by enhancing the interface interaction between CL-20 and GO. In brief, this work provides an effective strategy to equilibrium between safety and energy properties of the explosive.
查看更多>>摘要：Extending the lifetime of drilling bits primarily requires an in-depth understanding of the material's behavior from which they are made. Metal matrix composite coatings (MMCs) are mostly used to cover these industrial components to increase their efficiency and protect them from corrosion and wear. For the drilling bits, the best combination of characteristics can be assured through the design of an efficient multiphase metal matrix composite coating. Among these materials, nickel-based composites have been recently raised as alternatives to chromium and cobalt-based ones. This paper aims to unravel the underlying relationships between the microstructure and the mechanical indentation behavior and electrochemical response of thermally sprayed nickel-based composite coating. For that, a nickel-based composite coating is characterized. This coating was separately obtained after flame spraying of NiFeCrBSi feedstock wires by using acetylene as a fuel. The coatings were deposited in air on X18 carbon steel substrates. Our results reveal that the matrix of the coating mainly contains Ni-γ dendrites. The interdendritic space of the coating is filled withγ-Cr2.4W0.6Si eutectic. In this coating, The Ni- γ phase that represents a eutectic constituent is depleted in iron. The morphology of carbides differs from one precipitate to another. The indentation behavior differs depending on the elasto-plastic behavior of the present phases and the presence of voids. Moreover, the EIS curves proved that the increase in ion concentration augments the charge transfer at the coating/electrolyte interface and accelerates corrosion. In the sulfuric solutions, the coatings form a thin and compact passive film layer that makes the charge transfer permanently constant at high ion concentrations (35 g/l).
NSTL
Elsevier