Abstract:
The effects of BaSO4 additions on the wetting of alumina by molten aluminum were studied by the sessile drop technique. To study the effect of BaSO4 decomposition (1100–1150◦ C), the additions were treated at two temperatures 700◦ C (973 K) and 1450◦ C (1723 K), respectively. BaSO4 additions at low and high temperatures did not improve the nonwetting character of these compositions. However, at higher firing temperature, the formation of BA6 (BaO•6Al2O3) has a nonwetting trend with increasing its content. To address the BA6 specifically a pure BaO•6Al2O3 was produced and tested. It was more nonwetting than the pure alumina. After the analysis of the contact angles for the BaSO4 and the BA6 (BaO•6Al2O3), it was concluded that these additions to alumina do not inhibit wetting by molten aluminum. In fact, at the addition levels common for refractories, the wetting tendency of molten aluminum is enhanced. Alternative explanations for the effectiveness of BaSO4 additions to alumina refractories are discussed.
