Facile synthesis of rice shaped CuO nanostructures for battery application

The oxides of transition metals are an important class of semiconductors, which have applications in electronics, magnetic storage media, solar applications and catalysis. Among them, CuO has attracted much attention due to its widespread applications. In this paper, a facile synthesis of rice shaped CuO nanostructures have been prepared by reflux method for battery application using Copper nitrate and ammonia as precursors. Samples were prepared at three different reaction timings namely 6, 12 and 24 h. The as-prepared samples were calcinated at 400 °C to ensure the formation of copper oxide. The final products were subjected to X-ray diffraction, scanning electron microscopy, FT-IR and UV–Vis spectroscopy in order to study the effect of reaction time on the properties of the prepared copper oxide nanostructures. It is found that at controlled reaction time rice shaped CuO nanostructures are obtained. Cyclic voltammogram was recorded to understand the electrocatalytic behaviors of the rice shaped CuO sample prepared under optimized condition.     

Phenomena of reverse momentum pulse and fluid leak after poison injection in the shut down system of PHWR

The primary function of the shut down system in a nuclear reactor is to terminate any reactivity transient occurring in the core during its entire design life. Normally there is more than one system, which are independent and diverse in its mode of operation. They consist of quick acting mechanisms like dropping of safety rods by gravity, poison injection, etc. Typically in liquid poison injection system wherein high flow velocities are involved, there is significant fluid structure interaction associated with cyclic shock transients in the system. One such phenomenon has been captured and analyzed to understand the dynamics involved in the loop. The trends of loop pressure and vibration indicated presence of more than two pressure transients after complete injection of poison. The first transient arrived after 1.44 s and the second after 0.75 s. The reverse pressure pulses that manifested in the loop as a result of fast injection of fluid has been mathematically characterized by solving basic fluid balance equations. Possibility of ball lifting due to momentum pulse is also discussed.     

Caulerpa lentillifera inhibits protein-tyrosine phosphatase 1B and protects pancreatic beta cell via its insulin mimetic effect

Food Science and Biotechnology - The aim of this study was to determine whether Caulerpa lentillifea extract (CLE) can protect pancreatic beta cells and enhance insulin signaling in adipocytes. We...     

Electric Fields Obviate Constrained Sintering

The phenomenon of constrained sintering, where large rigid inclusions of alumina have been shown to significantly reduce the rate of sintering of titania [Bordia and Raj (1988) J. Am. Ceram. Soc. 71, 302–310], is shown to subside nearly completely during flash sintering carried out under modest electrical fields. The result is explained by a different mechanism for volumetric and shear deformation under electric fields. It is proposed that vacancy and interstitials generated within the grains migrate to grain boundaries and pores to produce both volumetric and shear strain at equal rates, since, in this way, the diffusion distance for both modes of deformation becomes the same. In conventional sintering, where transport occurs from one interface to another, the diffusion distance for shear is twice as far as for densification, which retards sintering should it become controlled by shear deformation, as seen in constrained sintering.     

Chemical formation,characterization and properties of polycarbazole

Polycarbazole (PCz) was synthesized by chemical polymerization of carbazole in acetonitrile medium using ammonium persulfate as oxidant. The selection of solvent, concentration of the monomer, composition of the solvent, polymerization time, temperature, and pH were optimized to obtain better quality and yield of the polycarbazole. The synthesized polycarbazole was characterized by various techniques such as UV–Visible, FTIR, ¹H‐NMR, ¹³C‐NMR, COSY, NOESY, and XRD spectroscopy. The solubility of the polycarbazole was tested in various solvents. The thermodynamic stability of the polycarbazole was examined by DSC and TGA‐DTA analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Limits to the Stability of the Amorphous Nature of Polymer‐Derived HfSiCNO Compounds

Substituting silicon by transition metals in polymer‐derived ceramics (PDCs) holds the potential for a new class of polymer‐derived ceramics for ultrahigh‐temperature structural applications. We present experiments that show that the solid solubility of HfO₂ extends to Hf/Si ratio of <0.22. The materials are synthesized from (miscible) organic precursors. Similar to silicon‐based materials they remain amorphous after pyrolysis at 1000°C. Small‐angle X‐ray scattering and Raman spectra remain essentially unaltered. It is postulated that Hf, like Si, forms mixed‐bond tetrahedra with C, O, and N. The difference in the enthalpy of Hf‐based, and Si‐centered tetrahedra is calculated using single‐bond energies, reinforcing the feasibility of substituting Si with Hf or with Zr atoms. Such polymer‐based HfSiCNO compounds made directly from liquid organics, by a simple manufacturing process, may also be relevant to nanoscale dielectrics with low leakage electric charge in microelectronics applications.     

Sizing Cracks in Power Plant Components Using Array Based Ultrasonic Techniques

New techniques developed using the array transducer, to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components are discussed. Three studies are reported here including (a) Optimal beam steering angle for focused and unfocused inspection using phased array method for bottom-surface crack sizing. (b) A front wall correction algorithm for sizing of near-through-wall crack-like defects. (c) A small aperture technique for sizing of near-through-wall crack-like defects. A Finite Difference Time Domain (FDTD) based simulation was used to study and verify the experimental observations. The application of time domain scheme relative arrival time technique (RATT), to measure the size of the near-through wall crack-like defects for the leak before break (LBB) criterion, was also investigated and found to be insufficient. A conventional SAFT algorithm was used for improving the sizing using the small aperture technique.     

Use of cellular confinement for improved railway performance on soft subgrades

Due to extensive right-of-way, railroads are inevitably subject to poor subgrade conditions and interrupted service for significant maintenance due to excessive deformations and loss of track geometry. Geocell confinement presents itself as a possible solution for improving performance of ballasted railroad embankments over weak subgrade. To investigate the efficacy of geocell confinement on ballasted railway embankments, a set of well-instrumented, large-scale cyclic plate loading tests and numerical simulations were performed on geocell-confined ballast overlaying a weak subgrade material. The agreement of results from tests and simulations served as a basis for simulating practical track geometry and performance for various geocell configurations and subgrades using three-dimensional (3D) finite element (FE) analyses. The study showed that geocell reinforcement significantly decreased track settlement, decreased subgrade deformations with lower and uniform distribution of vertical stresses on subgrade and inhibited lateral deformation and serviceability under cyclic loading. These results demonstrate that geocell confinement can be an effective alternative to subsurface improvement or shorter maintenance cycles, particularly on weak subgrades.     

Convective heat transfer enhancement techniques of heat exchanger tubes: a review

Heat exchangers are widely used in almost all industrial activities. Turbulent promoters used in heat exchanger tubes are an effective way of enhancing the performance. This paper summarises various investigations using twisted tapes, wire coil ribs, baffles, and swirl flow generators. The main objective of this paper is to review various studies, in which different obstacle roughness elements are used to enhance the rate of heat transfer in the heat exchanger tubes. It has been found that a lot of experimental and analytical studies reported in the literature. On the basis of correlations developed by various investigators an attempt has been made to compare the thermal hydraulic performance of obstacles in heat exchanger tubes. In this work, a comparative study is also carried out to select the best obstacle roughness shapes for higher heat transfer rate and low pressure drop losses.     

A Novel In Situ Method for Producing a Dispersion of a Ceramic Phase into Copper That Remains Stable at 0.9T M

We apply an in situ approach, whereby a polymer is incorporated into copper and evolves within the metal into the ceramic phase, to create a dispersion of hard particles in a metal. All constituents for the ceramic phase are contained within the organic polymer. The temperature for this polymer to ceramic conversion lies in the 1073 K to 1273 K (800 °C to 1000 °C) range. The process produces a nanoscale dispersion of the ceramic, which leads to high microhardness that remains unaltered at temperatures up to 1223 K (950 °C) (0.9T _M). Apparently, the introduction of the ceramic phase leads to the retention of copper crystallite size of a few hundred nm, despite exposure to heat treatments at these very high temperatures. We call these materials polymer-derived metal-matrix composites.