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Modelling and Experimental Characterization of Processing Parameters in Vertical Twin Roll Casting of Aluminium Alloy A356

Dhindaw B., Singh S., Mandal A., Pandey A.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 4

121--132

EN

Production of near net shape thin strips using vertical twin roll casting method has been studied. In a typical VTRC process, the simultaneous action of solidification and rolling makes the process quite attractive as well as complicated. An industrially popular alloy A356 has been chosen for the VTRC processing. It is challenging to identify VTRC processing parameters for the alloy to produce thin strips because of its freezing range and complex composition. In the present work processing parameters of VTRC like roll speed, roll gap, melt superheat and the interface convective heat transfer coefficient have been investigated through modelling of the process. The mathematical model was developed which simultaneously solves the heat transfer, fluid flow and solidification, using commercial software COMSOL Multiphysics 5.4. VTRC sheets of alloy A356 were produced in an experimental set up and attempts were made to correlate the microstructures of VTRC A356 alloy to that predicted from the numerical studies to validate the model.

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Optical and sensing properties of Fe doped ZnO nanocrystalline thin films

Shukla R. K., Srivastava A., Kumar N., Pandey A., Pandey M.

Materials Science Poland

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2016

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Vol. 34, No. 2

354--361

EN

Undoped and Fe doped ZnO films of different molarities deposited by spray pyrolysis method using zinc nitrate and ferric chloride as precursors show polycrystalline nature and hexagonal wurtzite structure. Crystallite size decreases with an increase in dopant concentration from 0 at.% to 3 at.%. Doping improves the transmission of the films whereas it reduces the optical band gap of ZnO from 3.28 eV to 3.17 eV. The morphology resembles flake-like structures which collapse when the dopant is introduced. The samples are found to be sensitive to CO2 gas. Undoped ZnO shows maximum sensitivity at 350 ºC for higher concentration of CO2. Doped samples show maximum sensitivity at 200 ºC for all CO2 concentrations i.e. from 500 ppm to 4000 ppm. Maximum sensitivity is achieved at temperatures 350 ºC, 250 ºC, 300 ºC and 450 ºC for the samples prepared using precursor solution of 0.1 M molarity.

3

Mechanistic studies on the oxidation of acrylic acid by quinolinium chlorochromate (QCC)

Mishra K., Singh J. V., Pandey A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 1

15-23

EN

The kinetics of oxidation of acrylic acid with a recently developed new mild Cr(VI) reagent quinolinium chlorochromate (QCC) has been investigated in acetic acid-water mixture (50% v/v). The order in [QCC], [acrylic acid] and [H+] is unity. The increase in the amount of acetic acid in its reaction mixture increases the rate. The effect of ionic strength is negligible. The reaction rates have been determined at different temperatures and the activation parameters have been computed. Stoichiometry indicates that one mole of acrylic acid reacts with one mole of QCC. The mechanism consistent with the observed results has been discussed.

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Kinetics and mechanism of oxidation of some unsaturated organic substrates by quinolinium chlorochromate

Mishra K., Singh J. V., Pandey A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 1

25-33

EN

The oxidation of unsaturated organic compounds, viz. crotyl alcohol, allyl alcohol, crotonaldehyde and maleic acid by quinolinium chlorochromate (QCC) in acetic acid-water medium (50% v/v) leads to the formation of corresponding epoxide. The reaction is of first order each in QCC and the reductant. The reaction is catalysed by hydrogen ions. The increase in dielectric constant of the medium decreases the rate, while variation I in ionic strength has no perceptible change in rate. The reaction rates have been determined at different temperatures and the activation parameters have been evaluated. The mechanism consistent with the observed results has been discussed.

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Kinetics and mechanism of oxidation of D-galactose by quinolinium chlorochromate (QCC) in aqueous acetic acid medium

Singh J. V., Mishra K., Pandey A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 1

35-43

EN

The oxidation kinetics of D-galactose with quinolinium chlorochromate, C(9)H(7)NHCrO(3)Cl, has been studied in aqueous acetic acid medium 50% (v/v) in the presence of perchloric acid at constant ionic strength. The reaction under pseudo-first order condition, is first order with respect to both the [oxidant] and the [substrate]. The reaction is markedly catalysed by [H+] and the effect of [NaClO(4)] is negligible. Increasing the dielectric constant of medium decreases the reaction rate. A 1 : 1 stoichiometry is observed and the reaction did not induce the polymerisation of acrylonitrile. The reaction has been carried out at different temperatures and the various activation parameters have been computed. A probable mechanism of the reaction is suggested.

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The mechanism of L-arginine oxidation by quinquevalent vanadium in the presence of cationic surfactant in sulphuric acid media. A kinetic study

Dubey S., Pandey A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2001

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Vol. 49, No. 2

183-191

EN

The oxidation is first order each in [substrate] and the [oxidant]. The reaction follows an acid catalysed path, exhibiting second order dependence in [H+]. Bunnett's plot indicates that water acts as a nucleophile. Protonated form of oxidant has been postulated as the reacting oxidizing species. The rate studied at four different temperatures enabled us to calculate activation parameters. A suitable mechanism has been proposed.