Investigations on the absorption spectrum of TiO2 nanofluid

Nanofluids are tailored nano- colloidal suspensions of nanoparticles in a suitable base fluid. This present work investigates the absorption spectrum in TiO2-water nanofluids to identify the potential application of nanofluids in Direct Absorption Solar Collectors (DASC). Nanoparticles of Titanium dioxide (TiO2) are prepared by sol gel and characterized by X Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). TiO2-water nanofluids with weight fraction of 0.1% are prepared by a two-step process with sonication. The prepared nanofluids are investigated for their stability by a gravity sedimentation method and for their optical property by UV-Vis spectroscopy. Stability of nanofluid is essential for the applications of nanofluid in DASC. TiO2 nanoparticles with a crystallite size of 43nm are obtained .The SEM image reveals the agglomerated state of TiO2 nanoparticles and the stability of TiO2 nanofluid is reported as 9-10days. UV results indicate the decrease in absorption from 440-500nm, complete absorption from 500-700nm and increase in absorption from 700-900nm.TiO2 nanofluids are recommended as potential candidates for DASC in UV and IR regions

The factorial structure of the supervisor’s core competencies scale

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Voltammetric studies of the reduction of furfural on glassy carbon electrode in aqueous solutions

The electrochemical reduction of furfural is studied on glassy carbon electrode in aqueous buffer solutions using voltammetric technique. Tafel slope obtained from steady state voltammetry is pH dependent. Cyclic voltammetric data have shown that a single wave is formed in acidic and alkaline pH and two waves are formed at neutral pH particularly at higher concentration and the overall reduction process is a kinetically controlled irreversible proces

Divalent europium-activated alkaline-earth-metal chlorophosphate luminophores [M5(PO4)3Cl:Eu2+;M=Ca,Sr,Ba] by self-propagating high-temperature synthesis

Divalent europium-activated alkaline-earth-metal chlorophosphate luminophores (MCAP:Eu2+;M=Ca,Sr,Ba) have been prepared by self-propagating high-temperature (SPHT) synthesis in one pol employing the corresponding nitrates/chlorides, urea and diammonium hydrogen phosphate. The synthesized materials have been characterized by X-ray diffraction, photoluminescent emission spectroscopy, thermogravimetry, scanning electron microscopy and particle size analysis. The formation of chloroapatite depends on the nature of acid used in the combustion mixture. The photoluminescent emission efficiency and particle size distribution are found to depend on the amount of metal chloride used and on the sintering temperature. The results obtained are discussed with respect to the processing method employe

Photoconductive studies on electron beam evaporated CdSe films

Thin CdSe films were electron beam evaporated. The CdSe powder synthesized in thel aboratory by a chemical method was used as source for the deposition of films. Clean glass and titanium substrates were used as substrates. The substrate temperature was varied in the range of 30–250 1C. X-ray diffraction studies indicated polycrystalline hexagonal structure. The band gap was 1.65eV. The grain size was15–30nm with increase of substrate temperature. Photoconductive cells fabricated with the doped and undoped films have exhibited high photosensitivity and high signal to noiseratio. The current voltage characteristics were linear

Structural, optical and photoconductive properties of electron beam evaporated CdSxSe1-x films

CdSxSe1-x films were deposited by the electron beam evaporation technique on glass substrates at different temperatures in the range 30 – 300 °C using the laboratory synthesized powders of different composition. The films exhibited hexagonal structure and the lattice parameters shifted from CdSe to CdS side as the composition changed from CdSe to CdS side. The bandgap of the films increased from 1.68 to 2.41 eV as the concentration of CdS increased. The root-mean-roughness (RMS) values are 3.4, 2.6, 1.2 and 0.6 nm as the composition of the films shifted towards CdS side. The conductivity varies from 30 Ωcm-1 to 480 Ωcm-1 as the ‘x’ value increases from 0 to 1. The films exhibited photosensitivity. The PL spectrum shifts towards lower energies with decreasing x, due to the decrease of the fundamental gap with Se composition

Electrochemical reduction of diazoamino benzene on glassy carbon electrode in alkaline solution

The electrochemical reduction of diazoamino benzene is studied on glassy carbon electrode in aqueous methanolic alkaline solution using voltammetry techniques. Tafel slope value derived from steady state voltammograms has indicated that the first electron transfer is irreversible. Cyclic voltammetric data have shown that a single wave is formed in methanolic alkaline medium and the overall reduction process is a diffusion controlled irreversible process. Product analysis of the preparative electrolysis experiments has confirmed that the reduction is a two electron transfer proces

Defects induced enhancement of Eu3+Emission in yttria (Y2O3:Eu3+)

Bixbyite type Y2O3:Eu3+ apart from being the efficient red phosphor extensively used in trichromatic fluorescent lamps, it is a typical system one can apply Jorgensen's refined electron spin pairing theory. This can be used to explain the enhancement in Eu3+ emission intensity observed with the aliovalent substitution in the yttria host matrix. Results based on these are explained qualitatively by considering a simple configurational coordinate model. Futhermore, an insight into the different types of defects induced with the aliovalent substitution in the yttria lattice has become possible with EPR probe

Electrochemical reduction of p-aminoazobenzene on glassy carbon electrode

The electrochemical reduction of p-aminoazobenzene was investigated on glassy carbon electrode in aqueous methanolic solution of less acidic and alkaline pII using voltametry techniques. Single wave was observed both at pH 3.0 and in alkaline pH conditions. Cyclic voltametric data showed that the reduction process was kineticly controlled irreverisible process at pH 3.0 and diffusion controlled irreversible process at alkaline pH. Product analysis of the preparative electrolysis experiments confirmed that the reduction was two electron transfer process