2,684 research outputs found

    Computation of Madelung Energies for Ionic Crystals of Variable Stoichiometries and Mixed Valencies and their application in Lithium-ion battery voltage modelling

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    Electrostatic energy (Madelung energy) is a major constituent of the cohesive energy of ionic crystals. Several physicochemical properties of these materials depend on the response of their electrostatic energy to a variety of applied thermal, electrical and mechanical stresses. In the present study, a method has been developed based on Ewalds technique, to compute the electrostatic energy arising from ion-ion interactions in ionic crystals like LixMn2O4 with variable stoichiometries and mixed valencies. An interesting application of this method in computing the voltages of lithium ion batteries employing spinel cathodes is presented for the first time. The advantages of the present method of computation over existing methods are also discussed.Comment: 15 page

    Stress corrosion cracking of prestressing steel in sulphide medium

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    Stress corrosion cracking behaviour of colddrawn and stress-relieved prestressing steel of standard quality conforming to IS. 1785- Part I has been studied in H2S saturated aqueous solution with and w~thout chloride. The steel was found to be highly susceptible to cracking even under open circuit condition at room temperature.The suscept~b~litdye creased slightly with temperature in the range 3O0C- 80°C. The threshold stress was found to increase with pH of the medium from 15%of proof stress at pH 2.6 to 40 %of proof stress at pH 6.5. A limiting pH of 7 above which stress corrosion cracking did not occur was obtained for water- H2S system and the corresponding value in 3.5PbNaCI- H2S system was found to be 9. Cathodic polar~sationd ecreased the time to failure while anodic polarisation increased the time to failure. Application of tensile stress was,found to increase the corrosion rate and also the solubility of hydrogen. The strain rate was found to have profound influence on the cracking process and the susceptihlity was h~gha t very low stram rates. SEM fractographic studies revealed that the fracture mode was predominantly intergranular. All these observations could be understood in terms of a decohesion mode

    Studies on the Corrosion Performance for Steel Embedded in Fly Ash Blended Concrete

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    The present investigation it to study the corrosion performance of fly ash blended cement concrete in chloride-contaminated environments by various electrochemical and non-electrochemical techniques. The chloride binding ability at the optimum replacement level of fly ash was also studied

    Electrochemical reduction of 2-methyl glutaronitrile on deposited electrodes in aqueous media

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    2-methyl- 1,5 diaminopentane is obtained by the reduction of 2-methyl glutaronitrile by a simple electrochemical technique, using deposited nickel black and palladium black cathodes under different conditions. Various synthetic parameters have been standardised. The results obtained from various reduction experiments are discusse

    Mono-chloro-substituted m-dinitrobenzene compound as cathode materials magnesium battery

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    The performance of mono-chloro-substituted m-dinitrobenzene compounds in magnesium battery is reported here. While the operating voltage is improved, the current efficiency is lowered by the chloro-substituents. The influence is explained taking into account inductive and mesomeric effects of the substituent

    Facile synthesis of mesoporous N doped zirconium titanium mixed oxide nanomaterial with enhanced photocatalytic activity under visible light

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    The present paper deals with a hydrazine mediated synthesis of high surface area and thermally stable N-doped zirconium titanium mixed oxide with enhanced photocatalytic activity towards reduction of selenium (VI) to metallic Se0 under visible light. Materials were synthesized at pH ¼ 2 by varying the hydrazine concentration and characterized by XRD, TEM, BET method, XPS, Raman spectroscopy and UV-vis solid state spectra. Presence of low amount of zirconium oxide (10 wt%) helps in phase stabilization and maintains the porous structure even at higher calcinations temperature in comparison to that of pure titania. XPS spectrum justifies the presence of nitrogen and Ti3+ in the material due to the decomposition reaction of hydrazine. Hydrazine controls the nitrogen content, surface area and the formation of oxygen vacancy in the material. Investigation of metal oxide to hydrazine ratio on the overall surface properties and photocatalytic activity indicates that the 1 : 6 ratio is the optimum composition for the best result. Surface area and pore volume increases to 298 m2/g and 0.323 cm3/g. The obtained material (TiZr-6N-400) is found to reduce selenium (VI) to selenium (0) under visible light within only 45 min of reaction. Increased photocatalytic activity under visible light is mostly due to the synergistic effect of substantial nitrogen doping, high surface area and presence of oxygen vacancy
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