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
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
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