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Synthesis and characterization of nanostructured molybdenum & tungsten carbide materials, and study of diffusion model

Covington L., Munirathinam K., Islam A. W., Roberts K. L.

Polish Journal of Chemical Technology

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2012

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Vol. 14, nr 1

28-34

EN

Powders of two molybdenum carbides (Mo2C and MoC1-x) and tungsten carbide (WC) were prepared by means of temperature programmed reaction (TPR) method. Mo2C and MoC1-x were synthesized by reacting MoO3 with a preselected molar ratio of methane/hydrogen and carbon monoxide/hydrogen gas mixtures respectively. WC was prepared using tungsten oxide (WO3) and a methane/hydrogen gas mixture. These carbides were ultrasonically dispersed in de-ionized water. Samples were characterized using room temperature x-ray diffraction and scanning microscopy. A kinetic diffusion model is also studied to determine diffusivities in solids where the diffusing species desorbs or reacts at the external surfaces, and where the diffusivity does not vary appreciably with concentrations. The method involves measuring the flux of the diffusive species into the solid under the influence of a temperature program.

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Analysis of partition coefficients of ternary liquid-liquid equilibrium systems and finding consistency using UNIQUAC model

Islam A. W., Zavvadi A., Kabadi V. N.

Chemical and Process Engineering

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2012

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Vol. 33, nr 2

243-253

EN

The objective of this study is to investigate the change in partition coefficient with a change in the concentration of the solute in a liquid system consisting of two relatively immiscible solvents. To investigate the changes in the partition coefficients, the data of the partition coefficients at infinite dilution and the ternary Liquid-Liquid Equilibrium (LLE) data at finite concentrations of the solute should be consistent. In this study, 29 ternary systems that are found in literature and for which the partition coefficients at infinite dilution and the ternary LLE data cannot be predicted accurately by the universal quasi-chemical (UNIQUAC) model are identified. On the basis of this model, some consistent and inconsistent ternary systems are introduced. Three inconsistent systems, namely hexane-butanol-water, CC14 (carbon tetrachloride)-PA (propanoic acid)-water, and hexane-PA-water, are chosen for detailed analysis in this study. The UNIQUAC activity coefficient model is used to represent these data over a range of concentrations. The results show large errors, exhibiting the inability of this model to correlate the data. Furthermore, some ternary systems in which cross behavior of solutes between two phases observed are identified.

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Universal liquid mixture model for vapor-liquid and liquid-liquid equilibria in hexane-butanol-water system over the temperature range 10 - 100 [degrees] C

Islam A. W., Kabadi V. N.

Chemical and Process Engineering

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2011

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Vol. 32, nr 2

101-115

EN

This is an extended research of the paper (Islam et al., 2011) conducted to obtain a universal set of interaction parameters of the model NRTL over the temperature range 10 - 100 [degrees] C for hexane. butanol.water system; meaning for binary pairs hexane.butanol, butanol.water and hexane.water; and for ternary system hexane.butanol.water. Thorough investigations of data selections for all binary pairs (Vapor.Liquid Equilibrium (VLE), Liquid.Liquid Equilibrium (LLE)), infinite dilution activity coefficient, infinite dilution distribution coefficient (Dsw), excess enthalpy (HE), and for ternary system (LLE of hexane.butanol.water) were carried out. Finally quadratic temperature dependent interaction parameters were estimated regressing all the mentioned data and in each case calculated results were compared with literature values. The comparisons showed an overall percentage of error within 15% for the mentioned phase equilibrium calculations.