Different morphologies of ZnO structures were successfully synthesized in precursor solutions with the pH of 8, 9, 10, 11, and 12 by a sonochemical method at room temperature. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopy. The photocatalytic activities of ZnO samples with different morphologies were evaluated via the degradation of methylene blue (C16H18ClN3S). In this research, the flower-like ZnO sample of densely assembled nanoplates exhibited the highest photodegradation of 64% under UV light irradiation within 300 min. 相似文献
Highly efficient visible-light-driven Ag3PO4/Bi2MoO6 hybrid photocatalysts with different mole ratios of Ag3PO4 were prepared via sonochemical method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that product are cubic Ag3PO4 nanoparticles supported on orthorhombic Bi2MoO6 nanoplates. Under visible light irradiation (>420 nm), the Ag3PO4/Bi2MoO6 photocatalysts displayed the higher photocatalytic activity than pure Bi2MoO6 for the decolorization of rhodamine B (RhB). Among the hybrid photocatalysts, 10% Ag3PO4/Bi2MoO6 exhibited the highest photocatalytic activity for the decolorization of RhB due to the efficient separation of electron–hole pairs. 相似文献
Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites were prepared by transforming Ag+ ions into metallic Ag0 nanoparticles loaded on top of Bi2WO6 nanoplates under visible light irradiation for 1 h. XRD, XPS, SEM and TEM analyses indicated that spherical metallic Ag nanoparticles were uniformly dispersed on top of orthorhombic Bi2WO6 thin nanoplates. Rhodamine B (RhB) was used as a dye model for investigation of photocatalytic performance of Bi2WO6 nanoplates with different weight contents of Ag nanoparticles illuminated by visible radiation. In this research, 10% Ag/Bi2WO6 nanocomposites have the highest photocatalytic activity in the degradation of RhB at 94.21% within 210 min because of the rapid diffusion of electronic charge through the Schottky barrier between metallic Ag nanoparticles and Bi2WO6 thin nanoplates, good electrical conductivity of metallic Ag nanoparticles, inhibited recombination of charge carriers and enhanced photocatalytic activity of Ag/Bi2WO6 nanocomposites. Main active species of the photocatalysis and stability of the photocatalyst were also evaluated.
This article describes experimental investigations of the heat transfer coefficient and pressure drop of R-134a flowing inside
internally grooved tubes. The test tubes are one smooth tube and four grooved tubes. All test tubes are made from type 304
stainless steel, have an inner diameter of 7.1 mm, are 2,000 mm long and are installed horizontally. The test section is uniformly
heated by a DC power supply to create evaporation conditions. The groove depth of all grooved tubes is fixed at 0.2 mm. The
experimental conditions are conducted at saturation temperatures of 20, 25 and 30°C, heat fluxes of 5, 10 and 15 kW/m2, and mass fluxes of 300, 500 and 700 kg/m2 s. The effects of groove pitch, mass flux, heat flux, and saturation temperature on heat transfer coefficient and frictional
pressure drop are discussed. The results illustrate that the grooved tubes have a significant effect on the heat transfer
coefficient and frictional pressure drop augmentations. 相似文献
The uniform BaMoO4 and BaWO4 nanoparticles (NPs) have been successfully synthesized by solution route – the direct precipitation of Ba(NO3)2 and Na2MO4 (M = Mo and W) in ethylene glycol under 24 h stirring. The XRD patterns and SEM images proved that the products were tetragonal structured BaMoO4 and BaWO4 with uniform round nanoparticles. Shape, average particle size and particle-size distribution of products were analyzed by TEM – showing the round nanoparticles with the average size of 31.52 ± 4.65 nm for BaMoO4, and 59.77 ± 9.61 nm for BaWO4. The room temperature photoluminescence (PL) indicated that the products have strong blue emission centered at 441 nm – excited with 280 nm wavelength for BaMoO4 NPs, and strong violet emission centered 378 nm – excited with 344 nm wavelength for BaWO4 NPs. These PL behaviors attributed the existence of intrinsic transitions in the [MO4]2- (M = Mo and W) tetrahedrons of their crystal lattices. 相似文献
Uniform α-MoO3 nanobelts were successfully synthesized by the hydrothermal process at 180°C for 20 h of the acidic solutions with different
pH values of 0–0.75, adjusted using HCl (conc.). XRD and SEM results revealed that the pH of the precursor solutions played
an important role in the phase, impurities, and morphology of the products. At the pH=0, the perfect α-MoO3 nanobelts with a few tens of microns long were synthesized. By the TEM characterization, orthorhombic MoO3 has a distinctive layered structure along the [010] direction, consisting of distorted MoO6 octahedrons connected by common corners along the [100] direction and common edges along the [001] direction. The electrochemical
measurement showed that the α-MoO3 nanobelts have high specific charge capacity. 相似文献
Orthorhombic Bi2S3 with different morphologies was successfully synthesized by the acid-catalyst hydrothermal reactions of bismuth nitrate (Bi(NO3)3) and thiourea (NH2CSNH2) solutions containing different amounts of hydroxyethyl cellulose (HEC). Phase, morphologies, and optical properties were characterized by X-ray diffraction, selected area electron diffraction, scanning and transmission electron microscopy, and ultraviolet-visible spectroscopy. The products, hydrothermally synthesized in the HEC-free, 0.25 g HEC-added, 0.5 g HEC-added and 1.00 g HEC-added solutions, were respectively proved to be orthorhombic Bi2S3 irregular nanorods, complete urchin-like colonies of regular nanorods, incomplete urchin-like colonies of regular nanorods, and highly crystalline regular nanorods growing along the [001] direction. Tauc band gaps of the orthorhombic Bi2S3 nanorods, synthesized in the HEC-free, 0.25 g HEC-added, and 1.00 g HEC-added solutions were determined to be 3.0, 1.75 and 1.8 eV, respectively. Formation mechanism of orthorhombic Bi2S3 nanorods, synthesized in the HEC-free and HEC-added solutions, was also discussed at great detail. 相似文献
This paper aims to present the exact closed form solutions and postbuckling behavior of the beam under a concentrated moment
within the span length of beam. Two approaches are used in this paper. The nonlinear governing differential equations based
on elastica theory are derived and solved analytically for the exact closed form solutions in terms of elliptic integral of
the first and second kinds. The results are presented in graphical diagram of equilibrium paths, equilibrium configurations
and critical loads. For validation of the results from the first approach, the shooting method is employed to solve a set
of nonlinear differential equations with boundary conditions. The set of nonlinear governing differential equations are integrated
by using Runge–Kutta method fifth order with adaptive step size scheme. The error norms of the end conditions are minimized
within prescribed tolerance (10−5). The results from both approaches are in good agreement. From the results, it is found that the stability of this type of
beam exhibits both stable and unstable configurations. The limit load point existed. The roller support can move through the
hinged support in some cases of β and leads to the more complex of the configuration shapes of the beam. 相似文献
In the present study, the effect of volume concentration (0.05, 0.1 and 0.15 %) and temperature (10–90 °C) on viscosity and surface tension of graphene–water nanofluid has been experimentally measured. The sodium dodecyl benzene sulfonate is used as the surfactant for stable suspension of graphene. The results showed that the viscosity of graphene–water nanofluid increases with an increase in the volume concentration of nanoparticles and decreases with an increase in temperature. An average enhancement of 47.12 % in viscosity has been noted for 0.15 % volume concentration of graphene at 50 °C. The enhancement of the viscosity of the nanofluid at higher volume concentration is due to the higher shear rate. In contrast, the surface tension of the graphene–water nanofluid decreases with an increase in both volume concentration and temperature. A decrement of 18.7 % in surface tension has been noted for the same volume concentration and temperature. The surface tension reduction in nanofluid at higher volume concentrations is due to the adsorption of nanoparticles at the liquid–gas interface because of hydrophobic nature of graphene; and at higher temperatures, is due to the weakening of molecular attractions between fluid molecules and nanoparticles. The viscosity and surface tension showed stronger dependency on volume concentration than temperature. Based on the calculated effectiveness of graphene–water nanofluids, it is suggested that the graphene–water nanofluid is preferable as the better coolant for the real-time heat transfer applications. 相似文献