Comparative Study of Magnetization Reversal Process Between Elliptical and Rectangular CoFe Nanomagnets

The magnetization reversal process for elliptical and rectangular permendur (CoFe) nanostructures were compared using micromagnetic simulations. Single domain states were observed in 10 nm thick elliptical and rectangular nanomagnets. The magnetization reversal along the major and minor axis in 60 nm thick elliptical nanomagnets occurred through the formation of double vortex states. In rectangular nanomagnets, it occurred through the formation of single vortex state along 225 nm and double vortex state along 335 nm.     

Spectroscopic studies on Zn-doped CdS nanopowders prepared by simple coprecipitation method

Abstract  

A series of Zn-doped cadmium sulfide (CdS:Zn) nanopowders were prepared by a simple coprecipitation method at room temperature, mixing the stoichiometric amount of reactants in a Milli-Q water solvent. The composition of nanopowders was accurately adjusted by controlling the molar ratio of Cd, Zn acetate in the mixed reactants. Spectroscopic studies on as prepared nanopowders were investigated by using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy, Raman, UV–Vis absorption, Field emission–scanning electron microscope–energy-dispersive X-ray analysis, and photoluminescence. Broad nature of XRD peaks confirms that as prepared powders are in nanosize and cubic structure at room temperature. Doping with Zn in CdS does not lead to any structural phase transformation but introduces a decrease in the lattice constants. Raman spectrum of Zn-doped CdS nanopowders shifts slightly toward higher energy side compared with their pure CdS nanopowders. Exciton–phonon confinement factor (S) varies in between 0.3 and 0.4. At lower wavelength excitation, we observed a broad emission peak maximum centered at 404 nm is attributed to localized band edge emission.     

Low temperature processing of (Zr0.8Sn0.2)TiO4 ceramics with improved Q factor

Polycrystalline (Zr_0.8Sn_0.2)TiO₄ (ZST) ceramics have been synthesized by solid-sate reaction method. The effect of B₂O₃, ZnO-B₂O₃ or 5ZnO-2B₂O₃ glass addition (0.2-1.0 wt.%) on microwave dielectric properties of ZST ceramics are investigated. The increase in average grain size via growth of large grains and dissolution of small grains is explained by Ostwald ripening phenomena. The highest Q × f_o values are found to be 61,500, 48,500 and 51,900 GHz for the ZST dielectric resonators added with B₂O₃, ZnO-B₂O₃ and 5ZnO-2B₂O₃ respectively. The effect of liquid phase sintering on microstructure and microwave dielectric properties of ZST ceramics is discussed.     

Fibrous growth of strontium substituted hydroxyapatite and its drug release

The effect of strontium on the crystallization of helical ribbon of hydroxyapatite (HAp) was investigated by single diffusion technique in silica gel matrix at 27 °C and physiological pH. Fibers of HAp were obtained on addition of strontium. The length of the HAp fibers, were found to decrease as the strontium substitution increases. The presence of strontium ion increased the crystallinity as well as crystallite size of HAp. The strontium substituted HAp (Sr-HAp) has similar stoichiometry to that of biological apatite. Sr-HAp was found to have increased surface area (35%) compared to control. Further, strontium substitution leads to an enhancement of in vitro bioactivity. The cumulative in-vitro amoxicillin drug release in phosphate buffer solution (PBS, pH 7.2) showed a prolonged release profile for Sr-HAp.     

Studies on degradation of reactive textile dyes solution by electrochemical method

The indirect electrochemical degradation of industrial effluents has become an attractive method in recent years. This paper deals with the electrochemical degradation of Novacron Deep Red C-D (NDRCD) and Novacron Orange C-RN (NOCRN) reactive azo dyes from aqueous solution using graphite carbon electrodes. The results indicated that initial pH, current density and supporting electrolytes were played an important role in the degradation of dyes. Electrochemical behavior of reactive azo dyes has been studied with cyclic voltammetry in acidic medium using pencil graphite as working electrode. The potentials selected for the two dyes were in the range +1.0 to -0.4V and +0.5 to -0.2V, respectively. The CV, UV-Vis and chemical oxygen demand (COD) studies were selected to evaluate the degradation efficiency. The maximum colour removal efficiency of 99% and 97% and chemical oxygen demand (COD) removal efficiency of 88% and 82% could be achieved for CDRCD and COCRN, respectively at 7 g L(-1) of NaCl concentration. The LC-MS study revealed the degradation of both the dyes and confirmed that the azo groups and aromatic rings were destroyed. The results revealed the suitability of the present process for the effective degradation of dye effluents.     

Congestion Management Considering Optimal Placement of Distributed Generator in Deregulated Power System Networks

This article presents an effective methodology for congestion management in deregulated power system networks considering optimal placement of a distributed generator. The novelty of this method is that the optimal placement of a distributed generator in a deregulated power system is decided on the basis of bus impedance matrix (Z_bus ) based contribution factors. The Z_bus -based contribution factors are independent of slack bus location, which complies with the prevailing competitive environment. The congestion management problem formulation comprises the maximization of social welfare function subject to power balance and transmission congestion constraints. The maximization of the social welfare function causes maximization of consumer benefits and minimization of supplier generation cost and distributed generators. The proposed methodology has been simulated on an IEEE 30-bus system, and comparisons of results are presented with and without distributed generators. The results show that the proposed approach gives significant improvement in social welfare and decreases congestion rent with distributed generator placement.     

Bioleaching of lateritic nickel ore by ultrasound

The bioleaching of nickel from lateritic ore of Orissa, India, using a nativeAspergillus niger strain was studied with and without ultrasound. Different parameters, such as spore concentration, amount of dextrose in the medium, pulp densities, and sonication time, were studied for maximizing the extraction of nickel. Enhanced recoveries and reduction in leaching time were demonstrated using ultrasound. The highest amount of nickel, 95 pct, was extracted in 14 days with an inoculum size of 10⁶ spore/mL and 2 pct dextrose in the medium under 30 minutes ultrasonic pretreatment using 43 KHz frequency at 1.5 W/cm² intensity. It was also found that ultrasound assists in selective leaching of nickel over iron.     

Ammoxidation of 3-picoline over V2O5/TiO2 (anatase) system I. Relationship between ammoxidation activity and oxidation state of vanadium

A series of titania (anatase)-supported vanadia catalysts ranging in V₂O₅ content from 0.4 to 9.9 mol% was prepared by wet impregnation technique, characterized by BET surface area measurement and X-ray diffraction, and evaluated for ammoxidation of 3-picoline. The average oxidation number of vanadium in the fresh and used catalysts was determined by titrimetric methods. The ammoxidation activity and the average oxidation number were observed to increase with vanadia loading up to 3.4 mol% in the catalyst which corresponds to a monolayer coverage. The phase transformation of anatase to rutile after the reaction was observed at a V₂O₅ loading of 5.9 mol%. The slow decrease of ammoxidation activity beyond 3.4 mol% V₂O₅ was attributed to the coverage of active monomeric VO_x species on the support by bulk vanadia and by other oxides, and also to compound formation with ammonia.     

Interdiffusion in γ (face-centered cubic) Ni-Cr-X (X=Al, Si, Ge, or Pd) alloys at 900 °C

Interdiffusion in nickel (Ni)-chromium (Cr) (face-centered cubic γ phase) alloys with small additions of aluminum (Al), silicon (Si), germanium (Ge), or palladium (Pd) was investigated using solid-to-solid diffusion couples. Ni-Cr-X alloys having compositions of Ni-22at.% Cr, Ni-21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge, and Ni-22at.%Cr-1.6at.%Pd were manufactured by arc casting. The diffusion couples were assembled in an Invar steel jig, encapsulated in Ar after several hydrogen purges, and annealed at 900 °C in a three-zone tube furnace for 168 h. Experimental concentration profiles were determined from polished cross sections of these couples by using electron probe microanalysis with pure element standards. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion fluxes were examined to determine the average ternary interdiffusion coefficients. The effects of ternary alloying additions on the diffusional behavior of Ni-Cr-X alloys are presented in the light of the diffusional interactions and the formation of a protective Cr₂O₃ scale. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.