Thermal conductivity prediction of MgAl₂O₄: a non-equilibrium molecular dynamics calculation

Magnesium aluminate spinel (MgAl₂O₄) is widely used in steel metallurgy industry. Thermal conductivity at high temperature significantly influences the cooling process of blast furnace and the heat preservation of steel converter. The effect of external (temperature) and internal (antisite defect and grain boundary) factors on the thermal conductivity of MgAl₂O₄ was studied with non-equilibrium molecular dynamics. The main factors affecting the thermal conductivity of MgAl₂O₄ were summarized. In the temperature range of 100–2000 K, the results showed that the thermal conductivity of MgAl₂O₄ changed from 11.54 to 4.95 W/(m K) with the increase in temperature and was relatively stable at the temperature above 1000 K. The thermal conductivity of MgAl₂O₄ declined first and then rose with the increase in the antisite defects, and the minimum value was 6.95 W/(m K) at the inversion parameter i = 0.35. In addition, grain boundaries reduced the thermal conductivity of MgAl₂O₄ by 20%–30% at temperature below 1000 K comparing with the non-grain boundary system. The grain boundary rotation angle at temperature above 1000 K had less effect on the thermal conductivity than that below 1000 K. Present simulation scheme for thermal conductivity of MgAl₂O₄ can also be applied to the study of other nonmetallic ceramics.