Rapid synthesis of Tb3+-doped gadolinium oxyhydroxide and oxide green phosphors and their biological behaviour

Green phosphors based on terbium doped GdOOH and Gd2O3 powders are prepared through a rapid microwave-assisted solution based method using ethanol as a solvent and without using anysurfactants. The as-prepared Tb3+:GdOOH powders are crystalline and show a flower-like morphology comprising many two-dimensional flake-like structures. The as-prepared powders show good luminescence properties under UV excitation and their conversion to Tb3+:Gd2O3 by annealing takes place at modest temperatures. A considerable increase in luminescence intensity is observed for the annealed powders, which is ascribed to phase change from oxyhydroxide to oxide as well as an increase in crystallinity as a result of annealing. Cytotoxicity studies reveal that the as-prepared powders show considerable toxicity towards the cells, whereas the annealed powders do not hamper the cell growth.

A Low-Cost, High Energy-Density Lead/Acid Battery

Lightweight plastic grids for lead/acid battery plates have been prepared from acrylonitrile butadiene styrene copolymer. The grids have been coated with a conductive and corrosion-resistant tin oxide layer by a novel rapid thermally activated chemical reaction process. X-ray powder diffraction and X-ray photoelectron spectroscopy show the coated tin oxide film to be SnO2-like. The grids are about 75% lighter than conventional lead/acid battery grids. A 6 V/1 Ah lead/acid battery has been assembled and characterized employing positive and negative plates made from these grids. The energy density of such a lead/acid battery is believed to be more than 50 Wh/kg

MOCVD of aluminium oxide films using aluminium β\beta-diketonates as precursors

Deposition of Al$_2$0$_3$ coatings by CVD is of importance because they are often used as abrading material in cemented carbide cutting tools. The conventionally used CVD process for Al$_2$0$_3$ involves the corrosive reactant AICl$_3$. In this paper, we report on the thermal characterisation of the metalorganic precursors namely aluminium tris-tetramethyl-heptanedionate [ Al(thd)$_3$] and aluminium tris-acetylacetonate [ Al(acac)$_3$] and their application to the CVD of Al$_2$0$_3$ films. Crystalline A1203 films were deposited by MOCVD at low temperatures by the pyrolysis of Al(thd)$_3$ and AI(acac)$_3$. The films were deposited on a TiN-coated tungsten carbide (TiN/WC) and Si(100) substrates in the temperature range 500-1100 °C. The as-deposited films were characterised by x-ray diffraction, optical microscopy, scanning and transmission electron microscopy, Auger electron spectroscopy. The observed crystallinity of films grown at low temperatures, their microstructure, and composition may be interpreted in terms of a growth process that involves the melting of the metalorganic precursor on the hot growth surface

Cobalt oxide thin films prepared by metalorganic chemical vapor deposition from cobalt acetylacetonate

Thin films of cobalt oxide have been deposited on various substrates, such as glass, Si(100). SrTiO3(100), and LaAlO3(100), by low pressure metalorganic chemical vapor deposition (MOCVD) using cobalt(II) acetylacetonate as the precursor. Films obtained in the temperature range 400-600°C were uniform and highly crystalline having Co3O4 phase as revealed by x-ray diffraction. Under similar conditions of growth, highly oriented thin films of cobalt oxide grow on SrTiO3(100) and LaAlO3(100). The microstructure and the surface morphology of cobalt oxide films on glass, Si(100) and single crystalline substrates, SrTiO3(100) and LaAlO3(l00) were studied by scanning electron microscopy. Optical properties of the films were studied by uv-visible-near IR spectrophotometry

Improved lead–acid cells employing tin oxide coated Dynel fibres with positive active-material

A rapid-thermally-activated chemical reaction process has been employed to coat tin oxide onto Dynel fibres. Positive-limited 2 V/1.5 Ah lead-acid cells employing tin-oxide coated Dynel fibres as additive to positive active mass have been assembled and characterized under various operational conditions. In this manner, it has been possible to improve the positive active material utilization and particularly at higher discharge rates

ELECTRICAL TRANSITIONS IN PURE AND DOPED V2O3

Nous avons mesuré les propriétés électriques et thermiques de (CrxV1-x)2O3, 0 < x < 0,03 et de (TixV1-x)2O3, 0 < x < 0,06. Le dopage au chrome (0 < x < 0,018) augmente la température de la transition basse température et augmente la résistivité de la phase métallique ; il rend la transition haute température mieux définie puis diminue l'amplitude de cette transition. Cette dernière transition dans V2O3 dopé à 1 % de chrome est caractérisée par des discontinuités en forme de marche de la résistivité et par des pics lors des balayages en analyse thermique différentielle. L'étude de V2O3 dopé au titane montre que l'amplitude de même que la température de la transition basse température (Tt) diminue énormément lorsque le dopage au Ti augmente. Pour 5,6 % de Ti, Tt décroît de façon abrupte de 35 K à ≈ 0 K. L'énergie d'activation de la phase semi-conductrice diminue exponentiellement et tend vers zéro dans cette gamme de concentration. En rapprochant ces résultats avec d'autres (résistivité et chaleur spécifique), on peut penser que la transition haute température de (CrxV1-x)2O3 n'est pas une transition de Mott mais est peut-être une phase C. D. W. De plus, (TixV1-x)2O3 dont la structure n'est pas altérée par le dopage au Ti est un matériau intéressant pour tester les théories sur la disparition brutale des transitions isolant métal.Extensive electrical and thermal studies on transitions in (CrxV1-x)2O3, 0 ⩽ x ⩽ 0.03, and in (TixV1-x)2O3, 0 ⩽ x ⩽ 0.06, have been undertaken. An increase in Cr-doping (0 ⩽ x ⩽ 0.018) raises the temperature of the low-temperature transition and elevates the resistivity of the metallic phase ; it first sharpens and later diminishes the high-temperature transition. The latter (transition) in 1 at. % of Cr-doped V2O3 is characterized by stepwise discontinuities in resistivity and by sharp spikes in DSC scans. Experimental work on Ti-doped V2O3 shows that the size and temperature of the low-temperature transition (Tt) diminish drastically with increasing Ti content. At a Ti concentration of ca. 5.6 at. %, Tt drops abruptly from 35 to (presumably) 0 K. The activation energy of the semiconducting phase diminishes nearly exponentially to zero in this composition range. The above findings, in conjunction with other evidence obtained from resistivity and heat capacity measurements, suggest that the high-temperature transition in (CrxV1-x)2O3 system is not readily compatible with the Mott transition model but is consistent with the existence of Overhauser charge density waves. Further, the (TixV1-x)2O3 system, whose structure is essentially unaltered by Ti doping, provides a testing ground for theories on the abrupt disappearance of metal-insulator transitions