Synthesis of molten-electrolyte corrosion resistant MgAl2O4MgAlON sidewall materials by pressureless sintering

MgAl 2 O 4 MgAlON materials as potential candidate sidewalls were prepared by using AlN , MgO , Al 2 O 3 , and nanosized MgAl 2 O 4 powder as starting materials. The reaction sintering of the MgAl 2 O 4 MgAlON materials was investigated by means of X-ray diffraction and scanning electron microscope. All the specimens were corroded in a Na 3 AlF 6 AlF 3 CaF 2 Al 2 O 3 bath to assess the electrolyte corrosion resistance . The results show that reaction sintering occurs in the MgAl 2 O 4 MgO Al 2 O 3 AlN system at 1830 °C and 5 MPa in flowing nitrogen for 5 h. The MgAl 2 O 4 MgAlON specimens are obtained and have high bulk density. The flexural strength increases from 202 ± 6 MPa to 248 ± 8 MPa and the Vickers hardness increases from 9.5 ± 0.2 GPa to 12.6 ± 0.4 GPa with increasing MgAlON content from 10 wt% to 40 wt%. The MgAl 2 O 4 MgAlON materials exhibit a good corrosion resistance to the Na 3 AlF 6 AlF 3 CaF 2 Al 2 O 3 bath owing to their high-density and the formation of the composite spinel in the specimens. The corrosion mechanisms of MgAl 2 O 4 MgAlON composites in molten electrolyte are mainly proposed by the dissolution of MgAl 2 O 4 and the diffusion of fluoride. Corrosion kinetic obeys a nearly parabolic law and the corrosion rate decreases with increasing MgAlON content.