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Muthu Kumaran S.,Hh The Rajahs College Autonomous
Materials Science and Engineering A | Year: 2011

Non-destructive diagnosis of nano-scale pre-precipitation and precipitation events can provide valuable support in controlling the thermal treatment for achieving the peak aged or any alternate desired microstructural state. The aim of the present investigation is to study the effect of isothermal ageing on density and hardness of 2024 Al-Cu-Mg alloy, and also to search the ability of measured ultrasonic velocity and attenuation and calculated elastic constants for monitoring the variations in microstructure and precipitation events during ageing. The specimens aged at 463. K for various periods up to 32. h followed by a solution annealed at 766. K for 1. h and water quenched, have been used for the ultrasonic velocity and attenuation measurements and metallurgical studies. The initial sharp acceleration in the hardness and velocities is due to the depletion of Cu from solid solution associated with the formation and growth of Cu-Mg co-cluster (GPB zone) and other intermediate phases. The local maximum at 10. h ageing time is due to the presence of higher volume fraction of precipitates like S′ and S and the minimum at 32. h of ageing time is due to the existence of dissolution and coarsening of S′ and S precipitates by overaged effect. © 2011 Elsevier B.V. Source


Ruby Nirmala L.,Holy Cross College Autonomous | Thomas Joseph Prakash J.,Hh The Rajahs College Autonomous
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

Potassium Chloride (KCl) as an additive is added into zinc thiourea chloride solution in a small amount (1 M%) by the method of slow evaporation solution growth technique at room temperature to get a new crystal. Due to the doping of the impurities on the crystals, remarkable changes in the physical properties were obtained. The grown crystals have been subjected to different instrumentation methods. The incorporation of the amount of potassium and zinc in the crystal lattices has been determined by AAS method. The lattice dimensions have been identified from single crystal X-ray diffraction measurements. The presence of functional group for the grown crystals has been identified by FTIR analysis. The optical, thermal and mechanical behaviors have been assessed by UV-Vis, TG/DTA and Vickers hardness methods respectively. The presence of dislocations of atoms has been identified by etching studies. © 2012 Elsevier B.V. All rights reserved. Source


Balachandran V.,Arignar Anna Government Arts College | Lakshmi A.,Hh The Rajahs College Autonomous | Janaki A.,Government Arts College for Women Autonomous
Journal of Molecular Structure | Year: 2012

In this study, the conformational stability of 2-hydroxy-4-methyl-3- nitropyridine and 2-hydroxy-4-methyl-5-nitropyridine has been analyzed, and vibrational analyses of the same have been carried out by the application of B3LYP/6-311++G basis set based on scaled quantum mechanical (SQM) method. Vibrational analyses of the most stable conformer of 2-hydroxy-4-methyl-3- nitropyridine and 2-hydroxy-4-methyl-5-nitropyridine are conducted by means of infrared absorption and Raman spectroscopy in combination with theoretical (DFT) simulations. The observed and simulated spectra agreed well. Molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that charge transfer occurs in the molecules. Information about the size, shape, charge density distribution, and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential (ESP). © 2012 Elsevier B.V. All rights reserved. Source


Ashok Kumar M.,Hh The Rajahs College Autonomous | Muthukumaran S.,Hh The Rajahs College Autonomous
Journal of Materials Science: Materials in Electronics | Year: 2013

Zn0.96Cu0.04O nanoparticles were synthesized by co-precipitation method using different solvents like ethanol, water and mixer of ethanol and water in 50:50 ratios. Crystalline phases and optical studies of the nanoparticles were studied by X-ray diffraction (XRD) and UV-visible photo-spectrometer. The XRD showed that the prepared nanoparticles have different microstructure without changing a hexagonal wurtzite structure. The calculated average crystalline size was high for ethanol (27.3 nm) due to the presence of more defects and low for water (26 nm) due to the reduction of defects and vacancies. The energy dispersive X-ray analyses confirmed the presence of Cu in ZnO system and the weight percentage is nearly equal to their nominal stoichiometry within the experimental error. The presence of lower Zn and Cu percentage in the sample prepared using ethanol than other solvents was due low reaction rate which was confirmed by XRD spectra. Water solvent has relatively stronger transmittance in the visible region which leads to the industrial applications especially in opto-electronic devices. The average crystalline size is slowly decreased from 27.3 nm (ethanol) to 26 nm (water) whereas energy gap is steadily increased from 3.56 eV (ethanol) to 3.655 eV (water) when water concentration is increased from 0 to 100 % in ethanol. Existence of functional groups and bonding were analyzed by FTIR spectra. The observed blue shift of UV emission from ethanol (349 nm) to water (340 nm) solution and the high IUV/IG ratio in water solution in photoluminescence spectra was due to the decrease of crystalline size and defects/secondary phases. The intensity of blue-green band emission was gradually decreased due to the reduction of defects and vacancies when water concentration is increased from 0 to 100 % in ethanol solution, which was consistent with the XRD observation. © 2013 Springer Science+Business Media New York. Source


Ashok Kumar M.,Hh The Rajahs College Autonomous | Muthukumaran S.,Hh The Rajahs College Autonomous
Journal of Materials Science: Materials in Electronics | Year: 2013

The present work investigates the effect of deposition times on the structural, optical and photoluminescence properties of Cd0.9Zn 0.1S thin films deposited on glass substrate by chemical bath deposition method. The deposition time was varied from 30 to 90 min. The deposited films were uniform and adherent to the glass substrates and amorphous in nature. Structural, optical and photoluminescence properties of Cd 0.9Zn0.1S thin films were studied through X-ray diffraction, energy dispersive X-ray, scanning electron microscopy, UV-Vis absorption, fourier transform infra red spectroscopy and photoluminescence spectroscopy. The average crystal size was increased from ∼1.3 to 2.5 nm with increase in deposition times. The absorption of the films was increased and the absorption peak shifted to lower wavelength side when deposition time increases. The increased energy gap from 2.4 to 2.49 eV with deposition time was due to quantum size effect and better crystallization. The presence of functional groups and chemical bonding were confirmed by FTIR. PL spectra showed two well distinct and strong bands; blue band around 407-415 nm and green band around 537-541 nm due to size effect. © 2013 Springer Science+Business Media New York. Source

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