Tensión superficial, viscosidad y densidad de algunas escorias CaO-Al₂O₃

Abstract

;Resumen Los conceptos metalúrgicos con respecto a la estructura y propiedades de los aluminatos de calcio, están predominantemente basados en analogías con el sistema ternario CaO-Al 2 0 3 -Si0 2 . En este trabajo se presentan y discuten los resultados de medidas de tensión superficial, densidad y viscosidad de algunas escorias de aluminato de calcio, en la franja de temperatura entre 1.500 y 1.650 °C, a la luz de investigaciones recientes sobre caracterización de la estructura vitrea de aluminatos y alumino-silicatos. La faja de composición investigada fue de 45 a 52 % en peso de alúmina. Los resultados indican una reducción en la densidad con la disminución de la razón molar CaO:Al 2 0 3 . La tensión superficial disminuye con el aumento de la relación molar CaO:Al 2 0 3 o con el aumento de la temperatura, en tanto que la viscosidad aumenta con la elevación del contenido de alúmina y disminuye con el aumento de la temperatura. El comportamiento observado en los valores de tensión superficial y viscosidad con la variación de la composición, puede estar asociado a la presencia de algunos iones de aluminio en coordinación octaédrica que, a su vez, pueden presentar una proporción de aluminatos conteniendo iones de aluminio en reducido estado de valencia, tal como Al 2+ .Palabras clave: Escoria. Aluminato de calcio. Estructura. Propiedades físico-químicas.Surface tensión, densities and viscosities of some GaO-Al 2 0 3 slags AbstractThe metallurgical concepts with regard to the structures and properties of calcium alumínate melts have been based upon analogies within ternary CaO-Al 2 0 3 -Si0 2 systems. In this work the results of surface tensión, density and viscosity of some calcium aluminate slags, in the temperature range of 1500 to 1600 °C are presented and the results are discussed based upon recent structural characterisation results of crystalline aluminates. The compositional range investigated was from 45 to 53 weight-% alumina. The results indicate a reduction in density as the molar ratio CaO-Al 2 0 3 decreases. Surface tensión falls on increasing either the molar ratio CaO-Al 2 0 3 or temperature.Conversely, viscosity increases with increasing molar ratio CaO-Al 2 0 3 and decreasing temperature. The compositional dependence of both surface tensión and viscosity data may be associated with the presence of some aluminium ions in octahedral co-ordination, and a concept of surface behaviour is proposed which involves surface activity of aluminate anions containing aluminium ions in a reduced valence state, such as Al 2+ .

Viscosity Measurement of Slags using Rotating Bob and Vibrating Finger Viscometer

“…The information regarding to the blast furnace slag was taken (selected) from the researches of Han et al, 25) Kim et al, 26,27) Suzuki et al 28) and Tang et al 29) were compared with the results obtained by Oliveira et al, 30) Urbain et al 31) and Wu et al 32,33) The results of present work for the industrial blast furnace slag are in a good agreement with the data reported by Han 25) and Kim. 27) In the work of Kim,27) a Brookfield digital viscometer (rotating cylindrical method) was employed for the viscosity measurements and holding time for reaching equilibrium state was more than 30 minutes at each temperature.…”

“…The experimental data presented in the research performed by Oliveira et al 30) were estimated using Brookfield LVTD viscometer at 1 550°C. Results of the present work for the CaO-Al 2 O 3 system are in a good agreement with the data reported by Oliveira et al 30) Comparison of the experimental data of the present work using two viscosity measurement techniques with the data of Oliveira et al 30) reveals that the obtained results for the vibrating (oscillating) finger viscometer is more compatible with the data reported by Oliveira et al 30) However, there are considerable differences between the experimental results of the present work and the calculated data presented by Wu et al 32,33) Moreover, the obtained viscosity values for CaO-SiO 2 system have been compared with both the rotation cup viscometer results reported by Urbain et al 31) in the temperature range of 1 552 to 1 903°C and with the viscosity data obtained by simulations reported by Wu et al 32,33) Surprisingly, computed results of Wu et al 32,33) depict a better agreement with the present research as compared to the experimentally obtained values of Urbain et al 31) Fig. 5.…”

Addition of ceramics materials to improve the corrosion resistance of alumina refractories

“…3) [1]. Since solubility and viscosity properties change in the slag as CaO content changes [21]. The dissolution process in ceramics can be controlled by the diffusion of oxide components, through the limiting layer of slag existing in the front side of the oxide surface, or by dissolution rate of oxides in the slag [1].…”

The formation and breakup of molten oxide jets under periodic excitation

“…The density was estimated from literature values published by Mukai and Ishikawa, and the surface tension σ was taken from own pendant drop measurements. Regarding dynamic viscosity, a look into experimental values available in literature reveals a considerable scatter; see a selection of data in Figure (more data can be found elsewhere).…”