Wettability of silicon carbide by CaO-SiO2 slags

Abstract

The wettability of silicon carbide by liquid CaO-SiO2 slags that contain 47 to 60 wt pct SiO2 was studied using the sessile drop wettability technique. The experiments were carried out in Ar and CO atmospheres. A small piece of slag was melted on SiC substrates under different heating regimes up to 1600 °C. It was found that the wetting is not significantly dependent on the temperature and the heating rate. However, the wettability is relatively high, and the wetting is higher for slags that contain lower SiO2 concentrations. Moreover, the wettability between the slags and SiC is dependent on the gas phase composition, and it is higher in Ar than that in CO. When the SiO2 concentration changes from 47 pct wt to 60 pct wt, the wetting angle changes from 20 deg to 73 deg in Ar and from 58 deg to 87 deg in a CO atmosphere. The formation and bursting of gas bubbles also was observed after some contact time, which indicates that the wetting system is a reactive type. However, microscopic studies indicated that no metal phase exists at the slag/silicon-carbide interface. Therefore, it was concluded that chemical reactions between the slag and SiC take place and that SiO2 is slowly reduced to form CO and SiO gases. Based on the experimental data, the dependence of the Girifalco-Good coefficient on the slag composition and the relationship between the interfacial tension of CaO-SiO2 slags and SiC also were estimated. © 2009 The Minerals, Metals & Materials Society and ASM International.