Mechanical enhancement of MgO-CaO ceramics through transition interface design: molecular dynamics simulations and experimental validation

This study aims at the inadequate mechanical properties of MgO-CaO ceramics used in high-temperature alloy smelting, achieving significant improvements through interface design. Molecular dynamics simulations reveal the microscopic mechanisms underlying the poor mechanical properties of MgO-CaO ceramics. Specifically, the weak bonding strength at the grain boundaries between MgO and CaO results in the MgO-CaO interface acting as a conduit for the rapid propagation of cracks, with minimal effect on crack deflection. To address this issue, the interfacial bond strength was improved by constructing transition layers at the interface using CaLaAlO₄. Molecular dynamics simulations show that CaLaAlO₄ reacts well with MgO and CaO crystals, forming dual-sided transition layers at the MgO-CaO interface. This increases the interfacial binding energy from 1.266 J/m² to 3.369 J/m² and 3.320 J/m². Interfacial tensile simulations also reveal significant improvements in mechanical properties. Furthermore, the incorporation of CaLaAlO₄ suppresses crack propagation rates and induces crack deflection at the MgO-CaO interface. Finally, experimental results confirm the effectiveness of the microstructural design and the enhanced macroscopic performance. At 0.4 mol % CaLaAlO₄, the MgO-CaO ceramics achieved optimal performance, with a flexural strength of 130.92 MPa and specific fracture energy of 2.91 kJ/m². The mechanical strength increased by 3.4 times compared to the pre-introduction period. Microstructural analysis confirmed dual-sided transitional interfaces and showed that the CaLaAlO₄ phase hindered crack propagation. This work establishes fundamental principles for microstructural design of high-performance MgO-CaO ceramics operating under extreme environments, offering theoretical frameworks for interface-controlled refractory material development.