Ultrastrong Terahertz Emission from InN Nanopyramids on Single Crystal ZnO Substrates

The creation of high efficiency and room temperature terahertz (THz) emitters has long been expected in both scientific and industrial communities. Despite the recent progress in THz source such as quantum cascade lasers, high efficiency THz emitters capable of operating at room temperature are still elusive. Indium nitride (InN), a narrow bandgap semiconductor, has emerged as a promising THz emitter due to its unique electronic properties. However, the efficiency of InN THz emitters reported up to now is still far from theoretically predicted because of inadequately engineered electrical conduction and radiative coupling. In this study, the authors report a novel, high performance THz emitting structure consisting of nanoengineered InN micro/nanopyramid arrays on a single crystal zinc oxide (ZnO) substrate. With improved electronic conduction from Zn diffusion induced doping and enhanced radiation coupling benefiting from uniquely structured geometry, the InN nanopyramids yielded THz emission intensity is close to an order of magnitude stronger than that of p-type indium arsenide (InAs). These findings prove that InN is a promising THz material and of wide importance in material science, optical engineering sectors, etc

Synthesis of New Bis(3-hydroxy-4-pyridinone) Ligands as Chelating Agents for Uranyl Complexation

Five new bis(3-hydroxy-4-pyridinone) tetradentate chelators were synthesized in this study. The structures of these tetradentate chelators were characterized by 1H-NMR, 13C-NMR, FT-IR, UV-vis, and mass spectral analyses. The binding abilities of these tetradentate chelators for uranyl ion at pH 7.4 were also determined by UV spectrophotometry in aqueous media. Results showed that the efficiencies of these chelating agents are dependent on the linker length. Ligand 4b is the best chelator and suitable for further studies

Synthesis of TiO2/Pd and TiO2/PdO Hollow Spheres and Their Visible Light Photocatalytic Activity

A series of TiO2, TiO2/Pd, and TiO2/PdO hollow sphere photocatalysts was successfully prepared via a combination of hydrothermal, sol-immobilization, and calcination methods. The structure and optical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Telleranalysis, Barrett-Joyner-Halenda measurement, and UV-Vis diffuse reflectance spectroscopy. The photocatalysis efficiencies of all samples were evaluated through the photocatalytic degradation of rhodamine B under visible light irradiation. Results indicated that TiO2/PdO demonstrated a higher photocatalytic activity (the photocatalytic degradation efficiency could reach up to 100% within 40 min) than the other samples and could maintain a stable photocatalytic degradation efficiency for at least four cycles. Finally, after using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species for the effectiveness of the TiO2/PdO photocatalyst

First-Principles Calculations on Structural Property and Anisotropic Elasticity of γ1-Ti4Nb3Al9 under Pressure

The effect of pressure on the structural property and anisotropic elasticity of γ 1 -Ti 4 Nb 3 Al 9 phase has been investigated in this paper by using first-principles calculations. The obtained bulk properties at zero pressure are in good agreement with the previous data. The structural property and elastic constants under pressures up to 40 GPa have been obtained. According to the elastic stability conditions under isotropic pressure, the phase is found to be mechanically stable under pressures up to 37.3 GPa. From the obtained elastic constants, the elastic moduli, anisotropic factors and acoustic velocities under different pressures have also been obtained successfully together with minimum thermal conductivities and Debye temperature. It is shown that the ductility of the phase is improved and its anisotropy and Debye temperature are enhanced with increasing the pressure

Synthesis of a tetrazine-based catecholamide derivative and its evaluation as a chelating agent for removal of Cd(II), Co(II), and Cu(II)

<p>The synthesis and structural characterization of a tetrazine-based catecholamide (CAM) ligand, <i>N,N′</i>-bis(<i>N″</i>-(aminoethyl)-2,3-bis(hydroxy)benzamide)-1,2,4,5-tetrazine-3,6-diamine (<b>5</b>), were investigated. All compounds were characterized by ¹H NMR spectroscopy, ¹³C NMR spectroscopy, and FTIR spectroscopy. The protonation equilibria of <b>5</b> and complexation capacities (log <i>β</i>_pqr) of Cd²⁺, Co²⁺, and Cu²⁺ complexes of <b>5</b> were evaluated through potentiometric titration and spectrophotometric titration, respectively. Species independent pM value (=−log [M]_free) was used to compare metal affinities with the final sequence Cu²⁺ > Cd²⁺ > Co²⁺. Results show that <b>5</b> has potential for heavy metal removal.</p

Synthesis and Characterization of Random Block Hydroxyl-Terminated Polyfluoroether-Based Polyurethane Elastomers with Fluorine-Containing Side Chains

Polype ntafluoropropane glycidyl ether (PPFEE), a new random block hydroxyl-terminated polyfluoroether, was synthesized successfully by cationic ring-opening polymerization of 2-(2,2,3,3,3-pentafluoropropoxymethyl) oxirane, and its molecular structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectrometry, and gel permeation chromatography. The PPFEE-based polyurethane elastomers featuring fluorine in their side chains were prepared using PPFEE as soft segments, polyisocyanate polyaryl polymethylene isocyanate as hard segments, and dibutyltin dilaurate as catalysts under different curing conditions. The microphase separation, mechanical performance, and thermal behavior of the elastomers were investigated by differential scanning calorimetry, uniaxial tensile test, and thermal gravimetric analysis, respectively. Based on the results, the percentage of hard segments dissolved into the soft segments of elastomers was opposite to the change in breaking strength. The PPFEE-based polyurethane elastomer cured with 20 wt% PAPI at the curing temperature of 50 °C displayed the maximum tensile elongation of 2.26 MPa with an elongation at break of nearly 150%. The increased contents of PAPI can effectively strengthen the tensile strength, and the maximum tensile elongation was 3.04 MPa with an elongation at break of nearly 90% when the content of PAPI was 26 wt%. In addition, the PPFEE-based polyurethane elastomers exhibited excellent resistance to thermal decomposition and a sharp weight loss temperature at around 371 °C. All the results demonstrated that the PPFEE may be a potential polymeric binder as one of the ingredients applied to future propellant formulations

Synthesis, Characterization, Thermal Stability and Sensitivity Properties of New Energetic Polymers—PVTNP-g-GAPs Crosslinked Polymers

A series of energetic polymers, poly(vinyl 2,4,6-trinitrophenylacetal)-g-polyglycidylazides (PVTNP-g-GAPs), were synthesized via cross-linking reactions of PVTNP with three different molecular weight GAPs using toluene diisocyanate as the cross-linking agent. The structures of these energetic polymers were characterized by ultraviolet visible spectra (UV–Vis), attenuated total reflectance-Fourier transform-infrared spectroscopy (ATR-FTIR), and nuclear magnetic resonance spectrometry (NMR). The glass-transition temperatures of these energetic polymers were measured with differential scanning calorimetry (DSC) method, and the results showed that all the measured energetic polymers have two distinct glass-transition temperatures. The thermal decomposition behaviors of these energetic polymers were evaluated by differential thermal analysis (DTA), thermogravimetric analysis (TGA) and thermogravimetric analysis tandem infrared spectrum (TGA-IR). The results indicated that all the measured energetic polymers have excellent resistance to thermal decomposition up to 200 °C, and the initial thermal decomposition was attributed to the breakdown of azide group. Moreover, the sensitivity properties of these energetic polymers were measured with the national military standard methods and their compatibilities with the main energetic components of 2,4,6-trinitrotoluene (TNT)-based melt-cast explosive were evaluated by using the DTA method. The results indicate that these energetic polymers have feasible mechanical sensitivities and can be safely used with TNT, cyclotetramethylene tetranitramine (HMX), 1,1-diamino-2,2-dinitroethene (FOX-7), 3-nitro-1,2,4-triazol-5-one (NTO) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)