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91.
92.
Impact of composition ratio on the structure and optical properties of (1-x)MnFe2O4/(x)ZnMn2O4 nanocomposite 下载免费PDF全文
Zein K. Heiba Mohamed Bakr Mohamed Ali A. Alkathiri Sameh I. Ahmed A A Alhazime 《中国物理 B》2022,31(7):77102-077102
($1-x$)MnFe$_{2}$O$_{4}$ (MFO)/$x$ZnMn$_{2}$O$_{4}$ (ZMO) ($x=0$, 0.2, 0.5, 0.8, and 1.0) nanocomposite samples were prepared using co-precipitation procedure. The phase percentage, cell parameters, and crystallite size of MFO and ZMO phases in each nanocomposite sample were calculated using Rietveld refinement procedure. The x-ray diffraction (XRD) analysis and Fourier-transform infrared spectroscopy techniques established the variation in the lattice parameters of each phase are due to permutation of all cations among the octahedral and tetrahedral sites of MFO and ZMO. The different oxidation states of different ions in all samples were determined using x-ray photoelectron spectroscopy (XPS) technique. The variation in absorbance of the nanocomposite samples with composition parameter ($x$) is dependent on the wavelength region. The optical bandgap of the nanocomposite samples is decreased as the content of ZMO phase increased. The effect of alloying on the refractive index, extinction coefficient, dielectric constant, optical conductivity, and the nonlinear optical behaviors of all samples were studied in detail. The nanocomposite sample $x=0.5$ disclosed upgraded optical parameters with the highest refractive index, optical conductivity, and PL intensity, which nominate it to be functional in various application fields. 相似文献
93.
Mohammed Ahmed Shehab Nikita Sharma Andrea Valsesia Gbor Karacs Ferenc Kristly Tams Kos Anett Katalin Lesk Lilla Nnai Klara Hernadi Zoltn Nmeth 《Molecules (Basel, Switzerland)》2022,27(9)
Nowadays, the use of hybrid structures and multi-component materials is gaining ground in the fields of environmental protection, water treatment and removal of organic pollutants. This study describes promising, cheap and photoactive self-supported hybrid membranes as a possible solution for wastewater treatment applications. In the course of this research work, the photocatalytic performance of titania nanowire (TiO2 NW)-based hybrid membranes in the adsorption and degradation of methylene blue (MB) under UV irradiation was investigated. Characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffractometry (XRD) were used to study the morphology and surface of the as-prepared hybrid membranes. We tested the photocatalytic efficiency of the as-prepared membranes in decomposing methylene blue (MB) under UV light irradiation. The hybrid membranes achieved the removal of MB with a degradation efficiency of 90% in 60 min. The high efficiency can be attributed to the presence of binary components in the membrane that enhanced both the adsorption capability and the photocatalytic ability of the membranes. The results obtained suggest that multicomponent hybrid membranes could be promising candidates for future photocatalysis-based water treatment technologies that also take into account the principles of circular economy. 相似文献
94.
Ashour A. Ahmed Oliver Kühn Rifaat H. Hilal Mohamed F. Shibl 《International journal of quantum chemistry》2013,113(9):1394-1400
Geometry and energetics of low energy conformers of sodium dihydrogen triacetate (SDHTA) and its anion are studied using density functional theory (DFT) at the Becke, Lee‐Yang‐Parr hybrid functional (BLYP) and Becke, three‐parameter, Lee‐Yang‐Parr hybrid functional (B3LYP) levels. For both cases, two structures of comparable energy are found, which have different symmetry with respect to the two hydrogen bonds (HBs). DFT‐based Born–Oppenheimer molecular dynamics simulations are performed for SDHTA, which show that both structures are visited at room temperature conditions. The trajectory analysis further reveals that the two HBs behave anticooperative, that is, on average elongation of one HB is accompanied by a compression of the other one. This is in accord with nuclear magnetic resonance (NMR) experimental studies for a similar counter ion–dihydrogen triacetate complex. © 2012 Wiley Periodicals, Inc. 相似文献
95.
The effect of dissolved oxygen (DO) and agitation rate in open and closed reactors was examined for sulfur-utilizing autotrophic denitrification. The reaction rate constants were determined based on a half-order kinetic model. Declining denitrification rate constants obtained for open reactors those of 8.46, 8.03, and 2.18 for 50 mg NO3 ?-N/L, while 11.12, 9.14, and 0.12 mg1/2/L1/2?h were for 100 mg NO3 ?-N/L at agitation speeds of 0, 100, and 200 rpm. In closed reactors, the ever-increasing denitrification rates were 10.13, 22.56, and 37.03, whereas for the same nitrate concentrations and speeds the rates were 13.17, 15.63, and 26.67 mg1/2/L1/2?h. The rate constants correlated well (r 2 ?=?0.89–0.99) with a half-order kinetic model. In open reactors, high SO4 2?/N ratios (8.02–75.10) while in closed reactors comparatively low SO4 2?/N ratios (6.10–13.39) were obtained. Sulfur oxidation occurred continuously in the presence of DO, resulting in mixed cultures acclimated to sulfur and nitrate. SO4 2? was produced as an end product, which reduced alkalinity and lowered pH over time. Furthermore, DO inhibited sulfur denitrification in open reactors, while agitation in closed reactors increased the rate of denitrification. 相似文献
96.
Ahmed A. Kassem 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(S7-S8):365-374
Abstract A series of carbohydrate-containing copolyhyrazides having ether bonds were prepared by low temperature solution polycondensation. 2,3,4,5-tetra-O-acetyl galactaroyl dichloride was polycondensed with hydroquinone-1,4-diacetic acid dihydrazide (1), 2-bromo-,2-chloro, 2-nirohydroquinone-1,4-diacetic acid dihydrazide (2, 3 and 4, respectively) and isophthaloyl dihydrazide (5) in dimethylformamide and produced copolyhydrazides (6-10), respectively. Copoly {1-[2-(2,3,4,5-tetra-O-acetyl-galacto-tetritoldi-1,4-yl)-5-(1,3,4-oxadiazol-di-2,5-yl]-3-[2-(1,3,4-oxadiazole-di-2,5-yl)-benzene]}(11)wassynthesizedbydehydrative cyclisation of the polymer(10) using thionyl chloride. Also, polymer (10), under de-O-acetylation in methanolic ammonia, gave the de-O-acetylated polymer (12). All the present new polymers were characterized by elemental analysis and i.r. and 1H-NMR spectroscopy. Their solubility, viscosity and physical properties are studied. 相似文献
97.
This review reports a broad overview of the synthetic procedures of 1,8-naphthyridines, dibenzo[b,g][1,8]naphthyridine, dibenzo[c,f][1,8]naphthyridine, 1,8-naphthyridine-3-carboxylic acid, 1,8-naphthyridine-3-carboxamide, and 1,8-naphthyridine-3-carbohydrazide compounds and their reactions. The physical properties, spectral data, and biological importance of naphthyridines are discussed. 相似文献
98.
Nageh K. Allam Ahmed Abdel Nazeer Elsayed A. Ashour 《Journal of Solid State Electrochemistry》2012,16(1):353-360
One of the major challenges in material design is the achievement of reasonable operational efficiency through understanding
the factors affecting the material’s performance particularly strength and service lifetime characteristics. In this work,
the electrochemical behavior of 72Cu–28Zn α-brass alloy in Na2MoO4-containing electrolytes was investigated using potentiodynamic polarization and electrochemical frequency modulation techniques
complemented with scanning electron microscopy. Also, stress corrosion cracking behavior of the alloy under both open-circuit
potential and anodic applied potentials, using the slow strain rate technique, was evaluated. The results drawn from the different
techniques are comparable. 相似文献
99.
New bis(β-difunctional) compounds could be prepared in good yields. Their utility as intermediates in the synthesis of novel bis(heterocycles) were also investigated. 相似文献
100.
Jukka J. Remes Ahmed Abou Elseoud Esa Ollila Marianne Haapea Tuomo Starck Juha Nikkinen Osmo Tervonen Olli Silven 《Magnetic resonance imaging》2013,31(8):1338-1348
Subject-level resting-state fMRI (RS-fMRI) spatial independent component analysis (sICA) may provide new ways to analyze the data when performed in the sliding time window. However, whether principal component analysis (PCA) and voxel-wise variance normalization (VN) are applicable pre-processing procedures in the sliding-window context, as they are for regular sICA, has not been addressed so far. Also model order selection requires further studies concerning sliding-window sICA. In this paper we have addressed these concerns. First, we compared PCA-retained subspaces concerning overlapping parts of consecutive temporal windows to answer whether in-window PCA and VN can confound comparisons between sICA analyses in consecutive windows. Second, we compared the PCA subspaces between windowed and full data to assess expected comparability between windowed and full-data sICA results. Third, temporal evolution of dimensionality estimates in RS-fMRI data sets was monitored to identify potential challenges in model order selection in a sliding-window sICA context. Our results illustrate that in-window VN can be safely used, in-window PCA is applicable with most window widths and that comparisons between windowed and full data should not be performed from a subspace similarity point of view. In addition, our studies on dimensionality estimates demonstrated that there are sustained, periodic and very case-specific changes in signal-to-noise ratio within RS-fMRI data sets. Consequently, dimensionality estimation is needed for well-founded model order determination in the sliding-window case. The observed periodic changes correspond to a frequency band of ≤ 0.1 Hz, which is commonly associated with brain activity in RS-fMRI and become on average most pronounced at window widths of 80 and 60 time points (144 and 108 s, respectively). Wider windows provided only slightly better comparability between consecutive windows, and 60 time point or shorter windows also provided the best comparability with full-data results. Further studies are needed to determine the cause for dimensionality variations. 相似文献