Preparation of NiAl2O4/SiO2 and Co2+-Doped NiAl2O4/SiO2 Nanocomposites by the Sol–Gel Route

NiAl₂O₄/SiO₂ and Co²⁺-doped NiAl₂O₄/SiO₂ nanocomposite materials of compositions 5% NiO – 6% Al₂O₃– 89% SiO₂ and 0.2% CoO – 4.8% NiO – 6% Al₂O₃– 89% SiO₂, respectively, were prepared by a sol–gel process. NiAl₂O₄ and cobalt-doped NiAl₂O₄ nanocrystals were grown in a SiO₂ amorphous matrix at around 1073 K by heating the dried gels from 333 to 1173 K at the rate of 1 K/min. The formations of NiAl₂O₄ and cobalt-doped NiAl₂O₄ nanocrystals in SiO₂ amorphous matrix were confirmed through X-ray powder diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter, transmission electron microscopy (TEM), and optical absorption spectroscopy techniques. The TEM images revealed the uniform distribution of NiAl₂O₄ and cobalt-doped NiAl₂O₄ nanocrystals in the amorphous SiO₂ matrix and the size was found to be ∼5–8 nm.     

Mean Flow and Turbulence Structure in Vertical Slot Fishways

This paper presents the results of an experimental study on the mean and turbulence structures of flow in a vertical slot fishway with slopes of 5.06 and 10.52%. Two flow patterns existed in the fishway and for each one, two flow regions were formed in the pools: a jet flow region and a recirculating flow region. The mean kinetic energy decays rapidly in the jet region and the dissipation rate in most of the areas in the pool is less than 200?W/m3. For the jet flow, the nondimensional mean velocity profile across the jet agrees very well with that of a plane turbulent jet in the central part of the jet with some scatter near its boundaries. Its maximum velocity decays faster compared to a plane turbulent jet in a large stagnant ambient. The jet presents different turbulence structure for the two flow patterns and for each pattern, the turbulence characteristics appear different between the left and right halves of the jet. However, the turbulence characteristics show some similarity for each case. The normalized energy dissipation rate shows some similarity and has a maximum value on the center of the jet. The results are believed to provide useful insight on the turbulence characteristics of flow in vertical slot fishways and can be used to verify numerical models and also for guidance in the design of fishways in the future.     

Preparation, characterization and electrical conductivity studies of nanocrystalline La doped BaMoO4

Different compositions of scheelite type nanocrystalline La doped BaMoO₄ [Ba_1−xLa_xMoO_4+x/2, where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5] samples were prepared by acrylamide assisted sol-gel combustion process. Dried gels prepared at 60 °C were heated at different temperatures and characterized using TG/DTA, XRD, FTIR and SEM-EDX techniques. From XRD patterns, crystalline phases for La doped BaMoO₄ samples were confirmed and their average crystallite sizes were calculated using Scherrer's formula and it was found to be less than 80 nm. Structure and thermal behavior of scheelite type nanocrystalline La doped BaMoO₄ samples were identified respectively using FTIR and TG/DTA measurements. Microstructure and existence of O, La, Ba and Mo elements in the La doped BaMoO₄ samples were obtained from SEM-EDX and HRTEMtechniques. The ‘d’ spacing values were obtained for different (h k l) planes and were well matched with the standard BaMoO₄. (h k l) values for different directions of planes were assigned for the observed HRTEM images and were matched with standard BaMoO₄. Grain and grain boundary conductivities were evaluated by analyzing the impedance data, using the Winfit software, measured at different temperatures.     

Dimensional changes of alginate dental impression materials

The weight loss and corresponding dimensional changes of two dental alginate impression materials have been studied. The weight loss kinetics indicate this to be a diffusion controlled process, but with a boundary condition at the surface of the concentration decreasing exponentially with time. This is in marked contrast to most desorption processes, where the surface concentration becomes instantaneously zero. The appropriate theory has been developed for an exponential boundary condition, and its predictions compared with experimental data; the agreement was satisfactory. The diffusion coefficients for two thicknesses of the same material were not identical as predicted by theory; the possible reasons for this are discussed.     

Flow Field in a Rectangular Basin with a Line Inlet and a Circular Outlet

An experimental study was conducted to investigate the flow field in a rectangular basin with a line inlet and a circular outlet. The basin has a length about four times of the water depth and the outlet level was varied in the study. The flow field in the basin can be characterized into three zones: the wall jet zone with an induced recirculation eddy, the outlet zone in the vicinity of the outlet, and the transition zone in between the two zones. The spreading of the wall jet was found to significantly exceed that of a classical wall jet. In the transition zone, the wall jet separated from the basin bed due to the adverse pressure gradient created by the jet impingement on the outlet wall. Upstream of the outlet, a special three-dimensional balloon-like flow pattern was observed. Within a distance of three times of the outlet diameter, potential flow theory predicts well the measured velocity.     

Dielectric Investigation of NaLiS Nanoparticles Loaded on Alginate Polymer Matrix Synthesized by Single Pot Microwave Irradiation

Sodium lithium sulfide (NaLiS) nanocomposite have been successfully synthesized by using microwave-irradiation (MWI) method. The study suggested that the application of microwave heating is to produce homogeneous and fine NaLiS nanocomposite which were achieved by using the precursors of lithium acetate and thioacetamide in the presence of sodium alginate biopolymer. FTIR is used to identify the structural coordination and functional groups of the prepared nanocomposite. The structural property of NaLiS particles was investigated by XRD. The surface morphology and elemental composition of synthesized material was confirmed by SEM and EDX analyses. The optical property was studied by using UV–Vis spectrophotometer. Thermal stability of as prepared sample was studied by TGA/DTG analysis. Electrical transport studies of the prepared nanocomposite have been analyzed for various temperatures. NaLiS nanocomposite has ionic conductivity of ~?10^?7 S cm^?1 at 35 °C which is six orders of magnitude higher than that of micro sized bulk Li₂S (~?10^?13 S cm^?1).     

Sol–gel synthesis and characterization of Li2O–As2O5–SiO2 glassy system

The ternary 10% Li₂O + 90% (xAs₂O₅ + (1 − x) SiO₂) (x = 0.025, 0.05, 0.075 and 0.1) (LAS) glassy system with different compositions were prepared using sol–gel technique. All the prepared samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry techniques. The observed peak-free XRD patterns confirm the amorphous phase of the prepared LAS compounds. Structural coordination of LAS glassy samples was confirmed by Fourier transform infrared spectroscopy. Thermal behavior of the glassy samples was characterized by differential scanning calorimetry. Bulk conductivity of all the LAS glassy samples was calculated by analyzing the impedance data measured at different temperatures. Activation energy (E_a) is evaluated from the log σT vs. 1000/T plot and it is found to be 0.837 eV.     

High-performance nickel sulfide modified electrode material from single-source precursor for energy storage application

High-performance energy storage electrode materials are emerging demand in near future for the construction of supercapacitor with high energy and power densities. Herein, Nickel (II) Diethyldithiocarbamate was used as single-source precursor for Nickel Sulfide (Ni₉S₈) two-dimensional (2D) nanosheets (NSs) preparation and hexadecylamine as shape directing agent via simple solvothermal method. The orthorhombic structure of Ni₉S₈ NSs was confirmed by X-ray diffraction (XRD) pattern. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that as-prepared Ni₉S₈ nanoparticles possess sheet-like morphology. Besides, the thermal stability of Ni(DTC)₂ complex was studied by Thermogravimetric/Derivative Thermogravimetric (TG/DTG) with differential scanning calorimetric (DSC) analysis. The electrochemical properties of Ni₉S₈ NSs was studied using galvanostatic charge–discharge (GCD) and cyclic voltammetry (CV) techniques. From the charge–discharge study of Ni₉S₈ NSs, a high specific capacitance of 281 Fg^?1 was obtained at a current density of 1 Ag^?1 and up to 82% retentivity was achieved after 5000 cycles. Thus, the prepared Ni₉S₈ NSs could be the one of the attractive potential active electrode materials for the application of supercapacitor.

     

Computational and Experimental Study of Surcharged Flow at a 90° Combining Sewer Junction

Combining sewer junctions with a lateral inflow at 90° angle are commonly used in our sewer systems. A computational fluid dynamics (CFD) model based on Ansys CFX 10.0 was established to simulate fully surcharged flow at a 90° combining sewer junction. The model was carefully assessed by comparing its results with the measurements of detailed physical experiments. Good agreement was obtained between results of the computational model and of the laboratory experiments. The computational model was proved to be capable of simulating surcharged combining junction flow in the aspects of water depth, energy losses, velocity distributions, and turbulence. The verified CFD model was also used to investigate air entrainment and effects of the size of the junction chamber on the flow. Such CFD models can be used to optimize the design of sewer junctions and will also be useful in studying sediment transport at sewer junctions.     

Investigation of electrochemical behaviour and annealing effect on zinc cobaltite nanoparticles as working electrode material for energy storage device

Journal of Materials Science: Materials in Electronics - Spherical-shaped zinc cobaltite (ZnCo2O4) nanostructures have been formed by a simple sol–gel method using citric acid as a chelating...