Femtosecond Dynamics of a Polariton Bosonic Cascade at Room Temperature.

Whispering gallery modes in a microwire are characterized by a nearly equidistant energy spectrum. In the strong exciton-photon coupling regime, this system represents a bosonic cascade: a ladder of discrete energy levels that sustains stimulated transitions between neighboring steps. Here, by using a femtosecond angle-resolved spectroscopic imaging technique, the ultrafast dynamics of polaritons in a bosonic cascade based on a one-dimensional ZnO whispering gallery microcavity are explicitly visualized. Clear ladder-form build-up processes from higher to lower energy branches of the polariton condensates are observed, which are well reproduced by modeling using rate equations. Remarkably, a pronounced superbunching feature, which could serve as solid evidence for bosonic cascades, is demonstrated by the measured second-order time correlation factor. In addition, the nonlinear polariton parametric scattering dynamics on a time scale of hundreds of femtoseconds are revealed. Our understandings pave the way toward ultrafast coherent control of polaritons at room temperature.

Titanium-Based Metasurfaces for Optoelectronics.

We report on the fabrication method that enables the development of transparent conductive metasurfaces capable of the resonant absorption of light in specific frequency bands. The approach is based on embedding linear sp-carbon chains and metallic nanoparticles in a porous matrix of titanium dioxide (TiO2). We develop a blading technique for the formation of a periodical grating of TiO2 microtubes at the macroscale. The method allowed us to maintain the periodicity of an array of microtubes with an accuracy of ±5%. Tuning the diameter of the tubes and the concentration of metallic nanoparticles, we achieved the regime of strong resonant absorption of the fabricated complex metasurface in the visible range. Computer simulations helped revealthe regime of TE/TM-polarized laser pumping that allowed for the most efficient transformation of light energy into electric current flow. In the studied structures, the sp-carbon clusters embedded inside transparent titanium dioxide tubes play the role of atomic wires. The interplay between efficient conductivity through carbon wires and the plasmon-enhanced absorption of light allows the design of photodiode structures based on periodical metasurfaces and characterized by highly selective optical sensitivity.

Deformation Behavior, a Flow Stress Model Considering the Contribution of Strain and Processing Maps in the Isothermal Compression of a Near-α Ti-3.3Al-1.5Zr-1.2Mo-0.6Ni Titanium Alloy.

In the present study, isothermal compression tests are conducted for a near-α Ti-3.3Al-1.5Zr-1.2Mo-0.6Ni titanium alloy at deformation temperatures ranging from 1073 K to 1293 K and strain rates ranging from 0.01 s-1 to 10 s-1 on a Gleeble-3500 thermomechanical compressor. The results show that, in the initial stage of the compression, the flow stress rapidly increases to a peak value because of elastic deformation, and then the alloy enters the plastic deformation stage and the flow stress slowly decreases with the increase in strain and tends to gradually stabilize. In the plastic deformation stage, the flow stress significantly decreases with the increase in the deformation temperature and the decrease in strain rate. A flow stress model considering the contribution of the strain is established, and the relative error between the calculated and the experimental values is 3.72%. The flow stress model has higher precision and can efficiently predict the flow behavior in the isothermal compression of the alloy. Furthermore, the processing map of the Ti-3.3Al-1.5Zr-1.2Mo-0.6Ni alloy is drawn. Based on the processing map, the influence of process parameters on power dissipation efficiency and stability parameters is analyzed, and the optimized hot working process parameters are pointed out.

Fabrication of Ultra-Fine-Grained W-TiC Alloys by a Simple Ball-Milling and Hydrogen Reduction Method.

In this paper, a simple method to fulfill the ideal microstructural design of particle reinforced tungsten (W) alloys with promising mechanical properties is presented. W-0.5 wt.% TiC powders with core-shell (TiC/W) structure are prepared by ball-milling and controlled hydrogen reduction processes. TEM observation demonstrates that the nano TiC particles are well coated by tungsten. The W-TiC powders are sintered by spark plasma sintering (SPS) under 1600 °C. The sintered microstructures are characterized by FESEM and TEM. It is found that the W-0.5TiC alloys obtain an ultra-fine-sized tungsten grain of approximately 0.7 µm. The TiC particles with the original nano sizes are uniformly distributed both in tungsten grain interiors and at tungsten grain boundaries with a high number density. No large agglomerates of TiC particles are detected in the microstructure. The average diameter of the TiC particles in the tungsten matrix is approximately 47.1 nm. The mechanical tests of W-0.5 TiC alloy show a significantly high microhardness and bending fracture strength of 785 Hv0.2 and 1132.7 MPa, respectively, which are higher than the values obtained in previous works. These results indicate that the methods used in our work are very promising to fabricate particle-dispersion-strengthened tungsten-based alloys with high performances.

Strongly coupling of amorphous/crystalline reduced FeOOH/α-Ni(OH)2 heterostructure for extremely efficient water oxidation at ultra-high current density.

Development of Fe-Ni-based electrocatalysts with high efficiency and stability remains a foremost challenge in the research for oxygen evolution reaction (OER) under high-current-density. Herein, a fast reduction strategy is developed for synthesis of strongly coupled crystalline α-Ni(OH)2 with amorphous reduced FeOOH (r-FeOOH) heterostructure grown on Ni foam (r-FeOOH/α-Ni(OH)2/NF). The obtained r-FeOOH/α-Ni(OH)2 with particle sizes around ~ 10 nm is coated orderly on the 3D NF surface in this hybrid. Benefitting from the strong coupling effects between r-FeOOH and α-Ni(OH)2, low potentials of 1.62 and 1.66 V at ultra-high current densities of 1,000 and 1,500 mA cm-2, as well as a robust stability over 10 h at 1,500 mA cm-2 in alkaline electrolyte are achieved in 3D r-FeOOH/α-Ni(OH)2/NF. Such a high OER performance is almost the best among all previously reported Fe-Ni-based OER electrocatalysts. Experimental results revealed that the NiOOH species is the real OER active phase in the 3D r-FeOOH/α-Ni(OH)2/NF. Further, bifunctional 3D r-FeOOH/α-Ni(OH)2 in alkaline electrolyzer delivers low cell voltages of 2.32 and 2.78 V to attain 500 and 1,000 mA cm-2 toward the overall-water-splitting, surpassing the benchmark Pt/C-Ir/C/NF system.

[Study on extraction and purification process of total ginsenosides from Radix Ginseng].

OBJECTIVE: To optimize the technological parameters of the extraction and purification process of total ginsenosides from Radix Ginseng. METHODS: With the contents of ginsenoside Rg1, ginsenoside Re and ginsenoside Rb1, the orthogonal design was adopted to optimize the extraction process. The purification process was studied by optimizing the elutive ratio of total ginsenosides as the marker. HPLC and spectrophotometer were employed for the study. RESULTS: The optimum conditions were as follows:Using 8 times volume of 75% ethanol extracting for 120 minutes and 2 times, the extraction temperature was 85 degrees C. AB-8 macroporous resin was selected, and the eluant was 4 BV 70% ethanol. CONCLUSION: The optimal conditions of extracting and purifying the total ginsenosides from Radix Ginseng is feasible.

Nitrogen-Doped Carbon-Encased Bimetallic Selenide for High-Performance Water Electrolysis.

Demand of highly efficient earth-abundant transition metal-based electrocatalysts to replace noble metal materials for boosting oxygen evolution reaction (OER) is rapidly growing. Herein, an electrochemically exfoliated graphite (EG) foil supported bimetallic selenide encased in N-doped carbon (EG/(Co, Ni)Se2-NC) hybrid is developed and synthesized by a vapor-phase hydrothermal strategy and subsequent selenization process. The as-prepared EG/(Co, Ni)Se2-NC hybrid exhibits a core-shell structure where the particle diameter of (Co, Ni)Se2 core is about 70 nm and the thickness of N-doped carbon shell is approximately 5 nm. Benefitting from the synergistic effects between the combination of highly active Co species and improved electron transfer from Ni species, and N-doped carbon, the EG/(Co, Ni)Se2-NC hybrid shows remarkable electrocatalytic activity toward OER with a comparatively low overpotential of 258 mV at an current density of 10 mA cm-2 and a small Tafel slope of 73.3 mV dec-1. The excellent OER catalysis performance of EG/(Co, Ni)Se2-NC hybrid is much better than that of commercial Ir/C (343 mV at 10 mA cm-2 and 98.1 mV dec-1), and even almost the best among all previously reported binary CoNi selenide-based OER electrocatalysts. Furthermore, in situ electrochemical Raman spectroscopy combined with ex situ X-ray photoelectron spectroscopy analysis indicates that the superb OER catalysis activity can be attributed to the highly active Co-OOH species and modified electron transfer process from Ni element.

Strongly Coupled 3D N-Doped MoO2/Ni3S2 Hybrid for High Current Density Hydrogen Evolution Electrocatalysis and Biomass Upgrading.

Developing noble metal-free electrocatalysts toward hydrogen evolution reaction (HER) that can work well at ultrahigh current density are crucial components in renewable energy technologies. Herein, we have reported a strongly coupled 3D hybrid electrocatalyst, which consists of N-doped MoO2 with Ni3S2 grown on Ni foam (N-MoO2/Ni3S2 NF) through an annealing treatment, followed by a thermal ammonia reaction. This N-MoO2/Ni3S2 with a particle size of ∼50 nm was evenly grown on the Ni substrate in this 3D hybrid system. Benefiting from the strong coupling effect, the N-MoO2/Ni3S2 NF exhibited a high HER performance in basic media, with a small value of the Tafel slope (76 mV dec-1) and a low potential of 517 mV at 1000 mA cm-2, which was superior to that of Pt/C (631 mV at 1000 mA cm-2). Experimental results revealed that constructing a coupling interface between N-MoO2 and Ni3S2 facilitated the absorption and dissociation of water molecules, consequently boosting the HER activity. Additionally, the 3D N-MoO2/Ni3S2 NF hybrid could act as a bifunctional electrode for both anode (biomass upgrading) and cathode (HER), which only required a lower potential of 2.08 V at 100 mA cm-2 as compared to the overall water splitting (2.25 V) and achieved a high biomass conversion ratio of over 90%. Moreover, substituting oxygen evolution reaction by urea oxidation reaction also can assist energy-saving hydrogen evolution for 3D N-MoO2/Ni3S2 NF.