Now showing 1 - 10 of 2947
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    1D-2D carbon heterostructure with low Pt loading as a superior cathode electrode for dye-sensitized solar cell
    (01-02-2017)
    Nechiyil, Divya
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    Cost-effective counter electrode (CE) with high electrocatalytic performance is very much essential for the wide application of dye-sensitized solar cells (DSSC). The 1D-2D carbon heterostructure (Pt/GR@CNT) with low platinum (Pt) loading has been synthesized by a facile in situ microwave-assisted polyol-reduction method. The excellent electrocatalytic activity as well as photovoltaic performance was achieved due to the combination of 2D graphene nanoribbons (GR) and 1D multi-walled carbon nanotubes (CNT) with high catalytically active Pt nanoparticles. Microwave-assisted longitudinal unzipping of few outer layers of CNTs along with co-reduction of Pt nanoparticles is an effective method to create electrochemically active defective edge sites, which have a crucial role in enhancing electrochemical performance. Synergistic effect of ultra-fine Pt nanoparticles, partially unzipped graphene nanoribbons and inner core tubes of CNTs modulates the power conversion efficiency of solar cell to 5.57% ± 0.03 as compared with 4.73% ± 0.13 of CNTs. Pt/GR@CNT CE even with low Pt loading of 14 μg cm−2 showcases equivalent performance with that of pure Pt counter electrode. [Figure not available: see fulltext.]
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    Generation of Ag nanoparticles by PAMAM dendrimers and their size dependence on the aggregation behavior of dendrimersa
    (21-08-2009)
    Kavitha, Manniledam
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    Parida, Manas R.
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    Prasad, Edamana
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    Deshmukh, P. C.
    Stable silver nanoparticles were generated in aqueous medium by amine, hydroxy and carboxylate terminated poly(amidoamine) (PAMAM) dendrimers in the absence of conventional reducing agents and light irradiation. Mechanistic studies suggest that, in spite of their lower pKa values, tertiary amines present in the dendritic structures act as the reducing agent. Dynamic light scattering and electron microscopic studies reveal that PAMAM dendrimers aggregate in presence of silver ions and the aggregation propensity plays a pivotal role in altering the size and shape of the nanoparticles generated in the dendritic milieu. The formation of metal nanoparticles with uniform size and shape by amine terminated PAMAM dendrimer is attributed to the unique aggregation propensity of amine terminated PAMAM. ©2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Minority carrier lifetime in thin films of Zn3P2 using microwave and optical transient measurements
    (01-10-1995)
    Fessenden, R. W.
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    Sobhanadri, J.
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    The transient nature of optical absorbance and the microwave cavity perturbation technique are used to measure the minority carrier lifetime in a polycrystalline thin film of Zn3P2 as well as to observe the spectral photoabsorbance. It has been observed that the transient decay curves consist of two components attributed to the surface carriers and the bulk carriers. The analysis of these spectral variation of carrier lifetime and spectral photoabsorbance indicate the possible band-band transitions in this material. © 1995.
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    Structural and magnetic properties of Nd3(Fe 1-xAlx)27.5Ti1.5(x=0.1-0.4)
    (25-05-2006)
    Ravi,
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    Venkatesh, S.
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    Prasad Rao, K.
    The structural and magnetic properties of Nd3 (Fe1-x Alx) 27.5 Ti1.5 (x=0.1-0.4) were investigated by x-ray diffraction, magnetization, and Curie temperature (TC) measurements. The unit cell volume increases with the Al substitution, in accordance with the larger atomic radius of Al. The saturation magnetization and the Curie temperature decrease with increasing Al content, and the decrease is attributed to the modification of the density of states of 3d band due to the 3p band of Al and to the magnetic dilution effect. The easy direction of magnetization is along the b axis for x=0.4. The anisotropy field (HA) decreases with increasing Al concentration. © 2006 American Institute of Physics.
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    Vibrational studies on Cu2ZnSnS4 thin films prepared by single step reactive DC magnetron sputtering
    (15-12-2020)
    Kaushik, Deepak Kumar
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    Cu2ZnSnS4 (CZTS) is a potential absorber material among its contemporary contenders for thin film solar cells. Controlling secondary phases in CZTS is a major concern. In the present study, CZTS thin films are prepared by a single step deposition technique: sputtering of individual metal targets of copper, zinc and tin in the sulfide plasma. The control on secondary phase formation and better microstructure properties are realized in the CZTS thin films prepared at low tin-target powers. The vibrational modes investigated by Raman measurement reveal transformation of CZTS thin films from less stable stannite phase to the stable kesterite phase under low Sn-power (30 W and 40 W) conditions.
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    Magnetoimpedance studies on ion irradiated Co33Fe33Ni7Si7B20 ribbons
    (15-04-2016)
    Kotagiri, Ganesh
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    Thulasiram, K. V.
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    Fernandes, W. A.
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    Misra, D.
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    Tribedi, L. C.
    Magnetoimpedance (MI) effect was studied on amorphous Co33Fe33Ni7Si7B20 ribbons that were irradiated with N+1, Ar+2 and Xe+5 ions, at energy of 75 keV. The (MI)m [maximum MI in each case] values are 9.4% and 11%, 9.9% and 6.5%, the largest, for the as-quenched and N+1, Ar+2 and Xe+5 ion irradiated ribbons respectively, at 2 MHz. The (MI)m value of the N+1 ion irradiated ribbon was observed to be the highest, due to an induced in-plane transverse magnetic anisotropy. The saturation magnetizations of the ion-irradiated ribbons are not seen to change with respect to that of the as-quenched ribbon; a small increase in the Ms was observed only upon irradiation with Xe5+ ions. The interaction between the large number of domains, with large uniaxial anisotropy led to large (MI)m values, at frequencies above 8 MHz in the Ar+2 ion irradiated ribbon.
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    Tiny Ni-NiO nanocrystals with exchange bias induced room temperature ferromagnetism
    (01-03-2016)
    Chaghouri, Hanan Al
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    Tuna, F.
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    Thomas, P. John
    Ni nanocrystals coated with a thin layer of NiO with a diameter of 5.0 nm show exchange bias induced ferromagnetism at room temperature. These particulates are freely dispersible in water and were obtained by annealing Ni nanoparticles coated with a thin amorphous layer of NiO. Particulates with diameters between 5.0 and 16.8 nm are studied. Detailed magnetic measurements reveal signs consistent with strong exchange bias including elevated blocking temperatures and tangible loop shifts. The structure of the particulates are characterized by high resolution transmission electron microscopy, energy dispersive x-ray analysis and x-ray diffraction.
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    Scaling of extended defects in nano-sized Brownmillerite CaFeO 2.5
    (01-09-2013)
    Gupta, Kapil
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    Singh, Shubra
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    Ceretti, Monica
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    Paulus, Werner
    We investigated the formation of extended defects in CaFeO2.5, predominantly appearing as antiphase boundaries (APBs), as a function of the synthesis method and temperature. While CaFeO2.5 is known to adopt an ordered oxygen defect structure showing long range order of the (FeO 4)∞ chains in its bulk form, interestingly, we demonstrated that the length of these (FeO4)∞ chains can be considerably scaled down to few nanometers by adopting a modified sol-gel method (low temperature synthesis) while the grain size of the resulting nano-phase CaFeO2.5 is around 50 nm. We discuss the synthesis dependent modulation of the length of APBs, characterized by X-ray diffraction and high resolution TEM, to be at the origin of an amplified switching dynamics of the (FeO4)∞ chains. This can accordingly explain the reduction of the onset temperature for oxygen diffusion to set in from 450 °C for bulk-CaFeO2.5 to 320 °C for nano-CaFeO2.5, as determined by 18O/16O oxygen isotope exchange reactions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Removal of metals from aqueous solution and sea water by functionalized graphite nanoplatelets based electrodes
    (15-01-2011)
    Mishra, Ashish Kumar
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    In the present wok, we have demonstrated the simultaneous removal of sodium and arsenic (pentavalent and trivalent) from aqueous solution using functionalized graphite nanoplatelets (f-GNP) based electrodes. In addition, these electrodes based water filter was used for multiple metals removal from sea water. Graphite nanoplatelets (GNP) were prepared by acid intercalation and thermal exfoliation. Functionalization of GNP was done by further acid treatment. Material was characterized by different characterization techniques. Performance of supercapacitor based water filter was analyzed for the removal of high concentration of arsenic (trivalent and pentavalent) and sodium as well as for desalination of sea water, using cyclic voltametry (CV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES) techniques. Adsorption isotherms and kinetic characteristics were studied for the simultaneous removal of sodium and arsenic (both trivalent and pentavalent). Maximum adsorption capacities of 27, 29 and 32 mg/g for arsenate, arsenite and sodium were achieved in addition to good removal efficiency for sodium, magnesium, calcium and potassium from sea water. © 2010 Elsevier B.V.
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    Editorial
    (01-01-2015)
    Gordon, Ivan
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    Krebs, Frederik C.
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    Mathew, Xavier
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    Lampert, Carl M.
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    Rougier, Aline
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    Smestad, Greg P.
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    The editorial of Solar Energy Materials & Solar Cells deals with topics associated with solar energy conversion. Solar energy conversion has now become a viable method to satisfy a substantial amount of a substantial amount of our energy needs while reducing carbon dioxide pollution, creating jobs and decreasing market instabilities tied to the geopolitics of fossil fuels. There is a growing awareness that fossil fuels are undesirable and that their supplies are rapidly diminishing or are environmentally or economically unsustainable.