In order to meet the needs of some users, such as environmental protection issues and optimization of various industrial production processes, refractory products are continuously improved. Therefore, the development of advanced materials (especially amorphous materials) is encouraged. For example, in the petrochemical and aluminum industries (most of the equipment operates at a maximum operating temperature of about 800°C and 1250°C), the refractory products originally designed for the steelmaking part are usually still used. However, these materials can only show microstructure sintering or densification and better thermodynamic properties when they are at higher temperatures (>1300°C). Therefore, it is necessary to design a novel refractory composition and enhance its usability to match its operating temperature.
One possible option is to add a sintering aid (SA) to the refractory castable to increase the densification speed at low temperature (ie 600～1000℃), in order to reduce energy consumption or develop a wider temperature range (800～1400℃) Products in the application. The sintering aid powder material is easy to handle and can be directly introduced into the castable dry mix. Because they interact with other raw materials and produce gases that affect the environment, these additives will generate a liquid phase in the designed microstructure during the first heat treatment of the refractory material, and then react and a new refractory phase (transient liquid phase) appears. . Braulio et al. evaluated the effects of various sintering aids (TiO₂, ZrO₂, MgF₂, BM and magnesium borosilicate) on the performance of Al₂O₃-MgO-CaO-SiO₂ castables. The selected sintering aid acts as a mineralizer or densifier for spinel (MgAl₂O4) and calcium hexaaluminate (CA6), increasing the formation of lamellae CA6 with high aspect ratio and refractory matrix The possibility of a small amount of liquid phase makes it excellent in creep resistance, for example when using boron-containing additives. Boron-based materials have a tendency to change phases (ie, decomposition and oxidation, etc.) at relatively low temperatures, and may produce boron-rich liquid phases, so they are a suitable choice for improving the sintering reaction of castables. As shown in Figure 1, B₂O₃ has a low melting point (approximately 470°C), and the presence of this liquid phase in the composition of high-aluminum refractories can help the substance to be transported (diffusion) faster and induce other components in the system to interact more easily. effect.
