Advanced Materials Research Vol. 1086

Abstract: Single crystals of pure and thiourea substituted L-alanine single crystals were grown successfully by the solution method with slow evaporation technique at room temperature. The effect of dopant on crystal properties has been studied. The solubility of the grown samples was found at various temperatures. Structural characterization of the grown crystals was determined by the single crystal X-ray diffraction (XRD). EDAX studies indicate the presence of thiourea in the doped L-alanine crystals. The functional groups were identified by FTIR spectroscopy. The UV-Vis- NIR spectral studies were carried out to analyze the optical absorption of the grown crystals and found that the absorption is very low in the wavelength region 232-1000nm for both the samples. SEM studies explain the surface morphologies of the grown crystals. Improvement in the SHG efficiency was studied by the Kurtz and Perry method. Thermal analysis has been carried on the grown crystal. Keywords: NLO, XRD, EDAX, UV-Vis-NIR, SEM

Abstract: In this paper we have studied the size and number of atom-pairs dependence normalized per atom pair binding (cohesive) energy and melting temperature of the Aluminium nitride () nanoparticle using simple model approach. It is observed that the per-atom-pair binding (cohesive) energy and melting temperature are a quadratic function of the inverse of the particle size fornano-particle. The per atom-pair binding (cohesive) energy and melting temperature comes near that of their bulk value with increasing the particle size and same as the bulk material when the particle size is above than 100 nm.Keywords Semiconductors; Size effect; Binding energy; Melting temperature; nanoparticle; nanocluster.

Abstract: Graphene oxide (GO) is extracted from graphite oxide synthesized using modified Hummers method. The extracted GO solution is then drop casted onto a p type silicon substrate and dried in hot air oven. The dried solution is annealed at a temperature of about 200 degree Celsius for about one hour to obtain thermally reduced graphene oxide (RGO). Such thermally synthesized RGO usually have a lot of structural defects which can act as a binding site for hydrogen. The binding efficiency of hydrogen to defect centers can be increased by applying electric field to RGO as it changes the carrier concentration (doping) on the surface. This induces more polarization in the hydrogen molecule resulting in strong binding force, thereby increasing its hydrogen storage efficiency. In our experiment we have demonstrated room temperature electric field doping in RGO films by modulating the channel current by changing the back gate voltage which is a precursor for employing RGO in hydrogen storage applications.Keywords Graphene oxide, Reduced graphene oxide, Field effect, Hydrogen storage, and Defects

Abstract: PrCrO₃(PCO) samples were prepared by Citric acid route .The samples were characterized by XRD and SEM. The sample exhibits a single phase orthorhombic structure with Pbnm space group. The temperature dependent and field dependent magnetic measurements were measured in the range of 5K-400K at 100 Oe field and 0 to 5T field at 5K and RT respectively .The temperature dependence of dc magnetic properties show that the ZFC and FC magnetization curves are irreversible strongly and nearly symmetrical below 240K .There appears a novel magnetization behavior with negative magnetization characteristic in ZFC, the diamagnetism like behavior .This behavior exhibits the coexistence of canted anti-ferromagnetic and weak ferromagnetic phase and the existence of competition mechanism below 240K . This behavior can be interpreted from the interaction between Pr³⁺ and Cr³⁺ moments .The field and temperature dependent magnetization indicates the phase transition from canted anti ferromagnetic to paramagnetic occurred below 240K. In the region of higher temperature above 240K, PrCrO₃ behaved as a typical Curie-Weiss paramagnetic.Keywords: Orthochromites ,Multiferroics ,Neel temperature.PACS: 75.85 +t, 75.60 d, 75.50.Ee,75.30 Et,76.30 Kg

Abstract: In this work, pure ZnS and Mn doped ZnS nanoparticles are synthesized by simple chemical precipitation method. The structure of pure zinc sulphide and Mn doped zinc sulphide sample are analyzed by X-ray diffraction technique. The morphological structure of zinc sulphide and Mn²⁺ doped zinc sulphide nanoparticles are studied using scanning electron microscope (SEM). The average particle sizes of pure ZnS nanoparticles are determined to be from 29 nm to 44 nm and Mn doped ZnS nanoparticles are determined to be from 99 nm to 135 nm. The optical properties of pure and Mn doped ZnS nanoparticles have been investigated by photoluminescence (PL) spectroscopy. The emission spectrum of Mn²⁺ doped with ZnS particles of the present study shows blue shift of the yellow-orange emission peak at 590 nm. Nanofluids are prepared for six different concentrations by dispersing pure and Mn²⁺ doped ZnS nanoparticles in de-ionized water. Thermal conductivity studies are carried out for both nanofluid systems and the results are discussed.

Abstract: Ultrasonic parameters of CuO: Diethylamine-Isopropaonol binary nanofluids at six different concentrations have been reported at three different temperatures like 298K, 308K and 318K. The acoustical parameters such as Ultrasonic sound velocity (v), Compressibility (β), Inter molecular free length (Lf), Acoustic impedance (Z) are calculated from experimental data. The variation of these parameters with composition of the mixture helps us in understanding the nature and extent of interaction between particles and the binary liquid mixtures. Keywords Ultrasonic velocity, Compressibility, Acoustic impedance, Inter molecular free length, Nanofluids

Abstract: Ultrasonic velocity and density of salicilaldehyde with iodine in hexane has been measured at 293.15K, 298.15K, 303.15K and 308.15K in different concentration. Ultrasonic velocity has been measured using single frequency interferometer at 2MHz (Model F-81). By using the Ultrasonic velocity (u), density (ρ) and coefficient of viscosity (η) and the other acoustical parameters adiabatic compressibility (κ), free length (L_f), interaction parameter (α), Free volume (V_f) were calculated. The addition of hexane with a mixture leads to a compact structure due to presence of dipolar type interaction. This contributes to the decrease in free volume values and the internal pressure shows an increasing trend. The results have been discussed in terms of solute-solute and solute-solvent interactions between the component and the compatibility of these methods in predicting the interactions in these mixtures has also been discussed.Key Words salicilaldehyde, iodine, hexane, Ultrasonic velocity, molecular interactions.

Abstract: Optical Visualization Techniques are gaining steady ground as a much favored method for observing and recording the physics of complex flows. These methods use a solid particle dispersed into the concerned flow to analyze the fluid motion. The particles are assumed to be of spherical shape (an acceptable relaxation), wherein the diameter is assumed to be constant this means that the particles have a normal distribution of size, with a sharp peak at the given diameter. Scattering of high-frequency laser light by these particles is the basis of image formation which depicts the flow physics. The fluid phase, which is the carrier phase, is required to impart sufficient momentum to the particulate phase for the particles to trace the flow of the fluid. For this reason, the particles are required to be of sizes not greater than 100 microns, in keeping with the increasing density with size. Alumina and Titania (Al₂O₃ and TiO₂) are the most commonly employed seed particles for this purpose. Laser scattering is also dependent on the luminescence prop-erties of the seed particles interactions between particle luminescence and external illumination plays a major role in determining the quality of results. With time, porous particles and artificial materials have found their acceptable places for use in this field. Silica, Glass and Ceramics provide a good balance of density (or weight) and surface area, which is difficult to obtain in metallic particles. The present paper proposes to evaluate the optical response characteristics of dispersed particles vis-a`-vis the operating/flow conditions and the laser systems used. The flow regimes com-monly considered for such studies include turbulence, mixing, reactions, phase changes and so on. Keywords Optical Response; Flow Seeding; Visualization; Multi-phase Flow: Flow Regimes; Particle Dispersion; Laser Diagnostics

Abstract: Scientists at the US Department of Energys Argonne National Laboratory have begun to combine nanoparticles of boric acidknown primarily as a mild antiseptic and eye cleanserwith traditional motor oils in order to improve their lubricity and by doing so increase energy efficiency. In laboratory tests, these new boric acid suspensions have reduced by as much as two-thirds the energy lost through friction as heat. This could result in a four or five percent reduction in fuel consumption. Reducing the size of the particles solved a number of old problems and opened up a number of new possibilities. Boric acid owes its lubricious properties to its unique natural structure. The compound consists of a stack of crystallized layers in which the atoms tightly adhere to each other. However, these layers stack themselves relatively far apart, so that the intermolecular bonds (van der Waals forces) are comparatively weak. When stressed, the compounds layers smear and slide over one another easily, like a strewn deck of playing cards. The strong bonding within each layer prevents direct contact between sliding parts, lowering friction and minimizing wear. In our presentation it is proposed to carry out computational studies on boric acid. Their structural parameters, thermal chemistry, SCF energy and electronic structure would be presented.

Abstract: In irrigation structures, seepage through the body wall and foundation play a major role for the assessment of failures in the structures. To design any kind of structure for the proper irrigation, the effect due to seepage should be considered widely. Many methods have been suggested for the prediction of seepage. Seepage analysis of irrigation structures works mainly on the basis of two dimensional Laplace equation. The Partial Differential Equation Toolbox in MATLAB provides a powerful and flexible environment for the study and solution of partial differential equations in two space dimensions and time. The equations are discretized by the Finite Element Method (FEM). Fluid flow through porous media particularly in the case of irrigation and hydraulic structures like dams and weirs is the focus of the current study and here flaws or cracks which occur in the domain cause variations and need remedial ones to improve or bring back to the original flow pattern. Since flaws in terms of fissures are very small injecting nanomaterial mixed mortar can provide significant improvements and modifications. Here in a rectangular domain the flow is studied throw finite element modeling with and without different sizes and location of flaws. Later these flaws are filled with nanomaterial mortars whose properties are based on test results and the flow is again studied to bring out the changes and improvements. Results are given for different nanomaterial mortars with different flaw sizes.