Thermal Conductivity Of CaTiO₃/MgAl₂O₄:A Non-equilibrium Molecular Dynamics Caculation

Calcium titanate?CaTiO₃?and magnesia alumina spinel?MgAl₂O₄?are widely used in metallurgical industry.They are common components of mold fluxes and blast furnace slag.Both of them have the characteristics of high melting point and low thermal conductivity,thus they dominate the heat transfer process between continuous casting slab and mold,affect the quality of continuous casting slab,and also affect the recovery and utilization of waste heat from blast furnace slag.Therefore,further research and exploration on the thermal conductivity of CaTiO₃ and MgAl₂O₄ and its influence factors at high temperature are of great significance for the quality control of continuous casting slab and the recovery of waste heat from blast furnace slag.This paper base on the non-equilibrium molecular dynamics method,and the thermal conductivity of CaTiO₃ and MgAl₂O₄ and its influence factors are studied by using software Lammps to provide theoretical basis and model basis for the calculation and prediction of high temperature thermal conductivity which is difficult to measure in the experiment.The thermal conductivity calculation model is established according to the research objects:CaTiO₃ and MgAl₂O₄,the structure models under the corresponding calculation condition are determined,and the appropriate potential and potential parameters are selected.The effects of size-effect,temperature,vacancies,antisite defects and grain boundary on the thermal conductivities of CaTiO₃ and MgAl₂O₄ are systematically studied.And the accuracy and correctness of the simulation are verified by comparing with the experimental data.And on this basis,the change rules of thermal conductivity are further discussed,and the thermal conductivity at high temperature is predicted and analyzed.The results of the study show that:?1?The size-effect affects the thermal conductivity of CaTiO₃ and MgAl₂O₄,and the thermal conductivity increases with the increase of the length of the simulation system,and the thermal conductivity tends to be stable after 19.10nm and 22.63nm for CaTiO₃ and MgAl₂O_4,respectively.?2?Temperature has a significant effect on the thermal conductivity of CaTiO₃ and MgAl₂O₄.In the temperature range of 100-1500K,the thermal conductivity of CaTiO₃increases first and then decreases with the increase of temperature,and changes at 1.36-2.15W/?m K?.In the temperature range of 100-2300K,the thermal conductivity of MgAl₂O₄changes at 4.73-11.54W/?m K?,and decreases with the increase of temperature,and tends to be stable after 1000K.Our calculated results are reasonable compared with the published experimental data.?3?Most of the defects in CaTiO₃ are calcium and oxygen vacancies,and oxygen vacancies are easier to form than calcium vacancies.The thermal conductivity of CaTiO₃decreases with the increase of vacancy number.When the concentration of calcium and oxygen vacancies exceeds 0.38%and 3.36%respectively,the thermal conductivity decreases slowly.The antisite defect is easier to form than any other point defect in MgAl₂O₄.The thermal conductivity of MgAl₂O₄ decreases first and then increases with the increase of the number of antisite defects,and reaches a minimum value of 6.95 W/?m K?at the inverse parameter i=0.35.?4?The thermal conductivity of CaTiO₃ and MgAl₂O₄ decrease obviously by the addition of grain boundaries,the maximum drop is up to 34.24%and 26.73%for CaTiO₃ and MgAl₂O_4,respectively.The change trend of thermal conductivity is basically the same as the system that without grain boundary.