Synthesis of Al6Si2O13-BaAl2Si2O8-ZrO2-based composites and their wettability by molten Al and an Al-Si alloy

The corrosion of refractory materials by molten aluminum alloys is a common problem during the aluminum recycling. Therefore, special emphasis has been focused in developing corrosion resistant materials by aluminum. In this research, composites based on Al6Si2O13-BaAl2Si2O8-ZrO2 were developed by two different methods. In the first method (S), BaAl2Si2O8, Al6Si2O13 and ZrO2 chemicals were mixed, pressed and sintered (1450 °C for 10 h). In the second method (R), the composites were obtained in situ by solid state reaction of BaCO3, Al2O3 and ZrSiO4 (1450 °C for 10 h). In both cases the amount of celsian was varied (8, 16 and 24 wt%) and the amount of ZrO2 was kept constant at 20 wt%. All the samples were characterized by X-ray diffraction (XRD) to identify the phases formed. A sessile drop test was performed on the samples obtained by the two methods using either pure Al or Al-8Si alloy. Then, the cross-section of the samples was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The thickness of the corrosion layer, when pure Al was tested, reached only about 266 µm after 2 h at 1100 °C for the samples prepared by the S process. The thickness was greater (around of 488 µm) in the case of the Al-8Si alloy for substrates prepared by the S and R processes under the same conditions. However, this is still a minimal penetration. Contact angles between molten metals and substrates were as high as 150° for all the systems, showing a non-wetting behavior. The contact angles obtained in this research were higher than those showed by a mullite substrate under the same conditions. The materials prepared in this work demonstrate to be highly potential composites for refractory applications in the aluminum industry.