Synthesis of CaO•2MgO•8Al2O3 (CM2A8) and its slag resistance mechanism

CM(2)A(8) is a solid solution of MA and CA(6). As a component in the ternary phase diagram of CaO-Al2O3-MgO, it was not reported in detail. So in this work, analytically pure CaO, MgO and Al2L3 were adopted as starting materials and batched stoimotrically according to CM(2)A(8). The raw materials were ground, mixed, shaped and reaction-sintered at different temperatures (1550 degrees C, 1650 degrees C, 1700 degrees C, and 1750 degrees C) to synthesize CM(2)A(8). The synthesized specimens were analyzed by XRD, SEM, and TEM and the corrosion mechanism against LF slag was also researched. The results show that high-purity CM(2)A(8) can be synthesized by reaction sintering at 1750 degrees C. During synthesis, granular MA and flake CA6 form and grow together; at 1650 degrees C, they solid-solve together to form C(2)M(2)A(14). As the temperature rises, solid solution reaction goes on, which results in the disappearance of CA(6), C(2)M(2)A(14), and MA in succession and forms high-purity CM(2)A(8) growing towards hexagonal column crystals. In the high temperature reaction between CM(2)A(8) and steel slag, Ca2+ in the slag reacts with CM(2)A(8) to form CA(2), damaging the structure of CM(2)A(8) and releasing excessive Mg2+ and A13* which move towards the molten slag. As the reaction between Ca2+ and CM(2)A(8) proceeds, a dense CA(2) coating forms on the surface of CM(2)A(8). The slag viscosity increases as well because of the entrance of Mg2+ and Al3+. Thus, the formation of the CA(2) coating and the enhancement of the slag viscosity restrain the penetration and corrosion of slag towards CM(2)A(8). (C) 2016 Elsevier Ltd. All rights reserved.