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101.
《International Journal of Hydrogen Energy》2019,44(29):15262-15277
Fundamental insight into the physics of buoyant gas dispersion from realistic flow geometries is necessary to accurately predict flow structures associated with hydrogen outflow from accidental leaks and the associated flammability envelope. Using helium as an experimental proxy, turbulent buoyant jets issuing from high-aspect-ratio slots on the side wall of a circular tube were studied experimentally applying simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques. Two slots with an aspect ratio of 10 were considered in this study. The effects of buoyancy, asymmetry, jet densities and Reynolds numbers on the resulting flow structure were studied in both vertical and horizontal orientations. Significant discrepancies were found between the evolution of current realistic jets issuing from curved surfaces and conventional high-aspect-ratio jets originating from flat surfaces. These realistic pipeline leak-representative jets were found to deflect along the jet streamwise axis. It was found that increases in aspect ratio caused a reduction in the angle of deflection, jet centreline decay rates and the lateral growth of both velocity and scalar fields compared to their non-planar round jet counterparts, most notably in the far field. 相似文献
102.
In this study, graphene oxide (GO) was synthesized from graphite powders via Hummers’ method. Polyamide 1212 (PA1212)/GO composites were prepared via a two-step melt compounding process. First, GO concentrates were prepared via solution coagulation. In this method, a GO solution was mixed with an ethanol-soluble polyamide solution. The resulting product was melt-compounded with a PA1212 matrix. This method enabled GO nanosheets to be well-dispersed in a PA1212 matrix. GO, which functioned as a nucleation template, exhibited heterogeneous nucleation effect in the PA1212 matrix because of its large specific surface area. The mechanical properties of the oriented PA1212/GO composites improved efficiently compared with those of pure PA1212. Crystal orientation degree and crystallinity in the composites increased slightly when GO was added after drawing. The composites’ reinforcing effect was mainly attributed to GO nanosheet alignment. These nanonsheets functioned as the nuclei to reinforce the entire oriented crystals. 相似文献
103.
2,5-Bis(n-methylphenyl)-1,3,4-oxadiazole with (n = 2,3,4), denoted n-MPOX, have been investigated by using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) methods, to evaluate the electrochemical behavior of brass in simulated cooling water system. The PP study revealed that oxadiazole inhibited both cathodic and anodic reactions, indicating a mixed type control of inhibition. It was shown that, 3-MPOX as well as 4-MPOX, were the best inhibitors and the inhibition efficiency followed the sequence: 3-MPOX ⩾ 4-MPOX ≫ 2-MPOX. The interference between non-oxidizing biocide CTAB and 3-MPOX and 4-MPOX against corrosion and biocorrosion has also been studied. 相似文献
104.
《Journal of power sources》2005,145(2):237-242
Ceria based solid solutions are promising ceramic electrolytes for SOFC which will be able to function at intermediate temperatures. In accordance with common trends to decrease the production and operating costs of new generation of SOFC materials the reaction based on metathetical pathway is described, whereby solid solution powders of rare earth doped ceria in the nanoscale range were obtained at room temperature. By simple hand mixing of reactants the reaction was enhanced, propagating afterwards by itself. Nanometric ceria powders doped with Y or Nd, as well as co doped with both cations were synthesized. Composition of Ce1 − xMexO2 − y ranged from x = 0–0.25. The reaction course is described in detail and the properties of the obtained powders are presented. 相似文献
105.
Stabilization of the metastable FCC phase has been achieved after 10 h milled Co powder sintering at 1400 °C. Phase identification of the Co powders was performed by the X-ray diffraction analysis, while the microstructural analyses were performed by scanning electron microscopy. Phase transformation on the metal was traced by the differential scanning calorimetry. 相似文献
106.
《Journal of the European Ceramic Society》2007,27(13-15):3629-3632
Pure, 140, 500, and 2500 ppm MgO-doped Al2O3 specimens were sintered at 1700 °C in a vacuum with and without pre-sintering heat treatment (HT) at 800 °C for 50 h in air. Pre-sintering HT improved the transmittance in the visible (400–700 nm) range significantly. This enhanced transmittance was explained in terms of the removal of residual pores and the homogenization of the microstructure due to the lowering of the boundary mobility as a result of the MgO addition and the suppression of local densification through a pre-coarsening step. 相似文献
107.
《中国稀土学报(英文版)》2019,37(10):1047-1052
In the present work, anisotropic Nd_2 Fe_(14) B/Sm_2 Co_(17) hybrid-bonded magnets were prepared with different Nd-Fe-B contents. It is found that the particle distributions and ratios between the two magnetic phases have important roles in the magnetic properties, microstructures and thermal stability of the magnets. With increase of Nd-Fe-B content, the saturation magnetization of the anisotropic hybrid magnet increases significantly, however, coercivity decreases, and the demagnetization curves show magnetically single-phase behavior. The anisotropic Nd_2 Fe_(14) B/Sm_2 Co_(17) hybrid-bonded magnets exhibit a maximum energy product and remanence of 14.15 MGOe and 99.53 A·m~2/kg, respectively, when the NdFe-B content is 70 wt% at room temperature. Furthermore, the hybrid magnets also have better thermal stability at elevated temperatures due to the interaction between the two magnetic particles. 相似文献
108.
《Polymer》2014,55(26):6717-6724
The aim of the present study is the preparation and characterization of microgel particles which are, contrary to other microgels, thermoresponsive as well as biocompatible. Hence, monodisperse p-MeO2MA-co-OEGMA microgel particles were synthesized by precipitation polymerization. Swelling/deswelling behavior and the structure of poly(ethylene glycol) (PEG) based microgel particles were investigated. A combination of dynamic light scattering (DLS) and small angle neutron scattering (SANS) was used. Particle size and the volume phase transition temperature (VPTT) are adjustable by changing the amount of comonomer. SANS measurements indicate an inhomogeneous structure of the PEG microgels in the swollen state. At temperatures above the VPTT a compact structure was observed. An increase of the comonomer content leads to a densely packed core and a fuzzy shell in the swollen state. Additionally, nanodomains inside the polymer network were observed in the temperature range around the volume phase transition (VPT). Due to this heterogeneous structure in the swollen state two correlation lengths of the network fluctuations were observed. 相似文献
109.
110.
Herein, the Zr-MOF UiO-66-NH2 was synthesized in a facile method. When the as-synthesized UiO-66-NH2 is served as an adsorbent for 2,4,6-trinitrophenol (PA), styphnic acid (TNR), 2,4-dinitrophenol (2,4-DNP), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (2,4-DNT) in water, the absorption capacities are 0.0225, 0.024, 0.0296, 0.0005, and 0.002 g/g, respectively. This suggests that UiO-66-NH2 is an excellent adsorbent for PA, TNR, and 2,4-DNP and is promising material for the removal of PA, TNR, and 2,4-DNP from wastewater. The excellent adsorption performance is attributed to the hydrogen-bond interactions between UiO-66-NH2 and these explosives. 相似文献