S. Agilan

Influence of the Cd/S Molar Ratio on the Optical and Structural Properties of Nanocrystalline CdS Thin Films

Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentration onto glass substrates by sol-gel spin coating method. The crystalline nature of the films has been observed to be strongly dependent on thiourea concentration and annealing temperature. The CdS films are found to be nanocrystalline in nature with hexagonal structure. The grain size is found to be in the range of 7.6 to 11.5 nm depending on the thiourea concentration and annealing temperature. The high resolution transmission electron microscopy (HRTEM) results of the CdS films prepared using cadmium to thiourea molar ratio of 0.3:0.3 indicate the formation of nanocrystalline CdS with grain size of 5 nm. Fourier transform infrared (FTIR) analysis shows the absorption bands corresponding to Cd and S. The optical study carried out to determine the band gap of the nanostructured CdS thin films shows a strong blue shift. The band gap energy has been observed to lie in the range of 3.97 to 3.62 eV following closely the quantum confinement dependence of energy on crystallite radius. The dependence of band gap of the CdS films on the annealing temperature and thiourea concentration has also been studied. The photoluminescence (PL) spectra display two main emission peaks corresponding to the blue and green emissions of CdS.

Natural dye sensitized TiO2 nanorods assembly of broccoli shape based solar cells

TiO2 nanorods based thin films with rutile phase have been synthesized using template free low temperature hydrothermal method. The scanning electron microscope images showed that the prepared TiO2 samples were made of TiO2 nanorods and the nanorods had arranged by itself to form a broccoli like shape. The X-ray diffraction studies revealed that the prepared TiO2 samples exhibit rutile phase. The grown TiO2 nanorods had been sensitized using the flowers of Sesbania (S) grandiflora, leaves of Camellia (C) sinensis and roots of Rubia (R) tinctorum. Dye sensitized solar cells had been fabricated using the natural dye sensitized TiO2 nanorods based thin film photoelectrode and the open circuit voltage and short circuit current density were found to lie in the range of 0.45-0.6 V and 5.6-6.4 mA/cm(2) respectively. The photovoltaic performance of all the fabricated natural dye sensitized TiO2 solar cells indicate that natural dyes have the potential to be used as effective sensitizer in dye sensitized solar cells.

Synthesis and Characterization of Selenium Nanowires

Selenium nanowires have been grown by chemical method. The effect of annealing on the properties of the prepared selenium nanowires has been studied. The X-ray diffraction studies indicated the formation of selenium with trigonal phase, and no secondary phase was observed. The composition analysis results show that selenium is present in the sample. HRTEM images reveal that selenium nanowires have diameter ranging from 30–50 nm and length of 1-2 𝜇m. The diameter and length of nanowires have been found to increase with increase in annealing temperature.

Effect of Chromium and Cobalt Addition on Structural, Optical and Magnetic Properties of NiO Nanoparticles

Abstract Nanocrystalline nickel oxide (NiO), chromium and cobalt doped NiO nanoparticles have been prepared successfully by chemical precipitation method. NiO, Cr and Co-doped NiO nanoparticles have been characterised using various analytical techniques such as X-ray diffraction, FESEM, HRTEM, UV absorption and M-H curves. The average grain size of NiO, Cr and Co-doped NiO nanoparticles are 10.33 nm, 9.54 nm and 8.70 nm respectively. The UV absorbance study shows a strong absorption edge at 314.96 nm, 308.64 nm and 305.37 nm respectively. The band gap values of NiO, Cr and Co-doped NiO nanoparticles are 3.936 eV, 4.017 eV and 4.060 eV. The incorporation of chromium and cobalt into NiO nanoparticles have strongly influenced the magnetic behaviour and the material got converted from super paramagnetic to ferromagnetic material.

Preparation and Characterization of Copper Dendrite Like Structure by Chemical Method

Abstract Copper particles are prepared at room temperature using a simple chemical method. The method used is capable of giving high yields. In this method sodium borohydride is used as a reducing agent and poly vinly pyrrolidone (PVP) as a capping reagent. The prepared copper particles are characterized by X-ray diffraction method and Energy dispersive x-ray analysis (EDX). The scanning electron microscopy (SEM) images show the formation of dendrite like structures. The transmission electron microscope (TEM) studies also conform the formation of dendrite structures.

Microstructure and Phase Transformation Behaviour of Co–Ni–Al Alloy by Spark Plasma Sintering

The CoNiAl alloys are prepared by using the spark plasma sintering (SPS) technique. The present study investigates the crystalline structure , Phase analyses, Physical and mechanical properties of the stoichiometric Co38Ni35Al27 alloys. The significant control over the magnetic and structural transformation temperature and high ductility of CoNiAl makes it a potential high-temperature Ferromagnetic shape memory alloy (FSMA). The test specimens were prepared at SPS temperature of 1000 °C at a sintering pressure of 50 MPa. The microstructural identification and the phase analyses of the mechanically alloyed powders and the SPS sintered specimens were investigated using optical microscopy, scanning electron microscopy and X-ray diffraction. The room temperature XRD results revealed that the sintered samples have body centred cubic β phase. A comparison of the room temperature XRD results for alloy powders and that of the sintered alloys has been studied. From the SEM images, we observe that the sintered alloys have martensitic twin variants. Also in the optical microscope, we observe the martensitic variants in the β phase structure. From the thermal studies, we analysed the phase transformation behaviour of the sample from β’ martensite to β martensite at 120°.

Investigation on the Structural and Optical Properties of Nanocrystalline TiO2 Thin Films

Nanocrystalline TiO2 thin films were prepared by sol-gel dip coating method. The structural investigations were carried out using x-ray diffraction technique. Anatase TiO2 thin films with tetragonal phase were obtained and the grain size was observed to lie in the range of 21-25 nm. Analysis on the surface topography of prepared films have been carried out using atomic force microscopy (AFM). The band gap energy is calculated from the absorption spectra of TiO2 films and is found to lie in the range 3.3 to 3.7 eV.

Solvothermal synthesis of TiO2/CNT composites and its physical and chemical properties

Anatase TiO2/CNT composites of different CNT ratio were prepared by solvothermal method. The X-ray diffraction analysis result showed that the sample has characteristic peaks of anatase TiO2. CNT incorporated TiO2 showed less peak intensity when compared to bare TiO2. The grain size was calculated using the Scherrer equation and it is found to be ∼ 2.38 and 2.46 nm for pure TiO2 and 5% CNT/TiO2 composites respectively. Optical properties were studied using UV-visible diffuse reflectance analysis and photo luminescence analysis respectively. UV analysis reveals the shift in absorption peaks towards the visible region for composites when compared to bare TiO2 powder. Raman spectroscopy studies show the presence of characteristic peaks corresponding to anatase TiO2, CNT. Morphological nature of the compounds was studied using High Resolution Transmission Electron Microscopy analysis respectively.

Effect of Surface Morphology on the Performance of Natural Dye Sensitized TiO2 Thin Film Solar Cell

Nanocrystalline and flower like structured TiO2 thin films are prepared by sol-gel spin coating method. The prepared films are annealed at 450°C. Natural dyes are prepared from delonix regia flower and eugenia Jambolana fruit. The prepared natural dyes were sensitized into both nanocrystalline and flower like structured TiO2 thin films. The prepared solar cell was characterized by SEM, Uv-Vis spectroscopy and J-V characteristics. Conversion of solar light into electricity was successfully accomplished with both natural dye based solar cells. The best solar energy conversion efficiency (ƞ= 0.2%) was obtained for eugenia Jambolana dye sensitized flower like structured TiO2 thin film solar cell.

Synthesis and Characterization of Fe and Fe2O3 Nanoparticles

Fe and Fe2 O3 nanoparticle have been synthesized by chemical precipitation method. The x-ray diffraction studies indicate the formation of Fe and Fe2 O3 nanoparticles with cubic phase and no secondary phase was observed. Surface morphology of Fe and Fe2 O3 has been studied using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) images reveal that Fe and Fe2 O3 nanoparticle have size ranging from 25-41 nm.