Wetting may be classified into two broad categories physical wetting and chemical wetting. In physical wetting, reversible The present paper reports results relating to the physical forces such as van der Waals and dispersion forces kinetics and mechanism of FeO reduction by provide the attractive energy required to wet the surface, graphite, the data being obtained from experimental whereas in chemical wetting, the reaction occurring at the investigations into the wettability of graphite by solid/liquid interface, with mass transfer, is mostly responsible molten slag containing FeO. The rate of FeO for wetting. The latter, which may also be termed reactive reduction was determined by measuring the wetting, describes the topic under consideration. At present, volume of CO gas formed as a result of the to the authors' knowledge, there is no theory which satisreduction of FeO in experiments conducted in the factorily explains reactive wetting, although there is some same sessile drop apparatus. The reduction literature4-12 that deals with reactive wetting relating mostly reaction initiated by direct slag-graphite contact to a molten metal/refractory interface. produces CO gas which spreads into the moltenThe contact angle h is an accepted measure of wettability slag droplet causing foaming of the slag; further in relation to a liquid droplet on a solid surface. For a reduction of FeO proceeds mostly via indirect non-reacting system, a balance of surface tension forces reduction. The rate of reduction was found to constitutes the following Young equation depend directly on the initial FeO content. An increase in temperature improves the rate of c sv −c sl =c lv cos h . . . . . . . . . . . . (2) reaction, which has an activation energy of 112•18 kJ mol−1. These results indicate that where c sv , c lv , and c sl represent the surface tension forces transport of FeO (Fe2+, O2−) in the liquid slag for solid/vapour, liquid/vapour, and solid/liquid interfaces, phase is probably the slowest step.I&S/1496a respectively. A system is considered to be wetting when the wettability parameter c lv cos h is greater than zero. When At the time the work was carried out, Dr Siddiqi, Mr Bhoi, Dr a reaction occurs at the interface, the free energy change Sahajwalla, and Dr Ostrovski were in the School of Materials per unit area per unit time also enhances wetting. In this
The paper presents experimental results of reduction of cupric oxide (CuO) by low-temperature hydrogen plasma in a microwave-assisted plasma set-up. The experiments were carried out at low microwave powers in the range of 600-750 W and low hydrogen flow rates in the range of 0.833 9 10 -6 to 2.5 9 10 -6 m 3 s -1 . In all the experiments for reduction of CuO with hydrogen plasma, an initial induction period was observed in the kinetic plots. The induction period decreases with increase in pressure or temperature. The induction period leads to the formation of active sites for adsorption of H 2 . After the induction period, fast autocatalytic reduction takes place followed by a sluggish period towards the end. The reduction process proceeds in sequential steps through the formation of sub-oxides. The kinetic data fits the Avrami-Erofeev equation with 'n' value close to 3. The resultant activation energy measured during hydrogen plasma processing is around 75.64 kJ mol -1 . This is lower compared to activation energies measured by other methods of reduction indicating a clear advantage.
A lv areas, cause a change in the Gibbs free energy DG of the system at constant temperature and The present paper reports results of experimental pressure, which is represented by4 investigations into the wettability of graphite by molten slag containing FeO. The wettability was DG=D P sl c sl dA sl +D P sv c sv dA sv +D P lv c lv dA lv(4) determined by measurement of the graphite-slag contact angle. A higher initial FeO content in the slag phase and higher temperature lead to betterThe wetting can proceed when DG is negative, and the wettability of graphite owing to the chemical system achieves a mechanical equilibrium when DG is equal reaction between the molten FeO in the slag and to zero. Therefore, DG is a thermodynamic driving force the graphite surface. The presence of FeO also for wetting. In a reactive system, in which liquid and solid reduces the surface tension of the slag. The free phases brought into contact are not in chemical equilibrium, energy of reaction released per unit area DG r has the solid-liquid interfacial tension and wetting are affected been estimated and correlated with the wettability by the Gibbs free energy of the liquid-solid reaction.5 parameters. The overall contribution of this factor It was shown by Zhukhovitski et al.6 that the further is to lowering the interfacial tension has also been the solid-liquid system from chemical equilibrium, the examined.I&S/1496b smaller is the solid-liquid interfacial tension c sl
This paper describes investigations on the role of electrolyte composition on the mechanism of the electroless copper deposition process. Both potentiostatic and galvanostatic polarization curves as well as steady-state plots are used in these investigations. Actual deposition rates are also measured through gravimetrically determined weight gain for comparison. The observation indicates that the two-compartment cell gives the mixed potential, E,, values closer to that of the actual plating, whereas the deposition rate determined from the mixed current, value is lower than that of the actual one. The mechanism of electroless copper deposition changes from anodic to cathodic control as well as from diffusion to activation control depending on the concentration of Cu + and HCHO. The mechanism in each case could be determined through the application of the Butler-Volmer equation to the half-cell reactions depending on the position of Em in the polarization plots of the individual half-cell reactions.
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